mDNSMacOSX/daemon.c - third_party/mdnsresponder - Git at Google

 /* -*- Mode: C; tab-width: 4 -*-
  *
  * Copyright (c) 2002-2011 Apple Computer, Inc. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
  */

 // We set VERSION_MIN_REQUIRED to 10.4 to avoid "bootstrap_register is deprecated" warnings from bootstrap.h
 #define MAC_OS_X_VERSION_MIN_REQUIRED MAC_OS_X_VERSION_10_4

 #include <mach/mach.h>
 #include <mach/mach_error.h>
 #include <servers/bootstrap.h>
 #include <sys/types.h>
 #include <errno.h>
 #include <signal.h>
 #include <unistd.h>
 #include <paths.h>
 #include <fcntl.h>
 #include <launch.h>
 #include <vproc.h>
 #include <pwd.h>
 #include <sys/event.h>
 #include <pthread.h>
 #include <sandbox.h>
 #include <SystemConfiguration/SCDynamicStoreCopyDHCPInfo.h>

 #if TARGET_OS_EMBEDDED
 #include <bootstrap_priv.h>

 #define bootstrap_register(A,B,C) bootstrap_register2((A),(B),(C),0)
 #endif

 #include "DNSServiceDiscoveryRequestServer.h"
 #include "DNSServiceDiscoveryReply.h"

 #include "uDNS.h"
 #include "DNSCommon.h"
 #include "mDNSMacOSX.h"             // Defines the specific types needed to run mDNS on this platform

 #include "uds_daemon.h"             // Interface to the server side implementation of dns_sd.h

 #include <DNSServiceDiscovery/DNSServiceDiscovery.h>
 #include "helper.h"

 //*************************************************************************************************************
 #if COMPILER_LIKES_PRAGMA_MARK
 #pragma mark - Globals
 #endif

 static mDNS_PlatformSupport PlatformStorage;

 // Start off with a default cache of 16K (99 records)
 // Each time we grow the cache we add another 99 records
 // 99 * 164 = 16236 bytes.
 // This fits in four 4kB pages, with 148 bytes spare for memory block headers and similar overhead
 #define RR_CACHE_SIZE ((16*1024) / sizeof(CacheRecord))
 static CacheEntity rrcachestorage[RR_CACHE_SIZE];

 static const char kmDNSBootstrapName[] = "com.apple.mDNSResponderRestart";
 static mach_port_t m_port            = MACH_PORT_NULL;

 #ifdef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM
 mDNSlocal void PrepareForIdle(void *m_param);
 #else // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM
 static mach_port_t client_death_port = MACH_PORT_NULL;
 static mach_port_t signal_port       = MACH_PORT_NULL;
 #endif // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 static mach_port_t server_priv_port  = MACH_PORT_NULL;

 static dnssd_sock_t *launchd_fds = mDNSNULL;
 static mDNSu32 launchd_fds_count = 0;

 // mDNS Mach Message Timeout, in milliseconds.
 // We need this to be short enough that we don't deadlock the mDNSResponder if a client
 // fails to service its mach message queue, but long enough to give a well-written
 // client a chance to service its mach message queue without getting cut off.
 // Empirically, 50ms seems to work, so we set the timeout to 250ms to give
 // even extra-slow clients a fair chance before we cut them off.
 #define MDNS_MM_TIMEOUT 250

 static int restarting_via_mach_init = 0;    // Used on Jaguar/Panther when daemon is started via mach_init mechanism
 static int started_via_launchdaemon = 0;    // Indicates we're running on Tiger or later, where daemon is managed by launchd
 static mDNSBool advertise = mDNS_Init_AdvertiseLocalAddresses; // By default, advertise addresses (& other records) via multicast

 extern mDNSBool StrictUnicastOrdering;
 extern mDNSBool AlwaysAppendSearchDomains;

 //*************************************************************************************************************
 #if COMPILER_LIKES_PRAGMA_MARK
 #pragma mark -
 #pragma mark - Active client list structures
 #endif

 typedef struct DNSServiceDomainEnumeration_struct DNSServiceDomainEnumeration;
 struct DNSServiceDomainEnumeration_struct
 {
     DNSServiceDomainEnumeration *next;
     mach_port_t ClientMachPort;
     DNSQuestion dom;    // Question asking for domains
     DNSQuestion def;    // Question asking for default domain
 };

 typedef struct DNSServiceBrowserResult_struct DNSServiceBrowserResult;
 struct DNSServiceBrowserResult_struct
 {
     DNSServiceBrowserResult *next;
     int resultType;
     domainname result;
 };

 typedef struct DNSServiceBrowser_struct DNSServiceBrowser;

 typedef struct DNSServiceBrowserQuestion
 {
     struct DNSServiceBrowserQuestion *next;
     DNSQuestion q;
     domainname domain;
 } DNSServiceBrowserQuestion;

 struct DNSServiceBrowser_struct
 {
     DNSServiceBrowser *next;
     mach_port_t ClientMachPort;
     DNSServiceBrowserQuestion *qlist;
     DNSServiceBrowserResult *results;
     mDNSs32 lastsuccess;
     mDNSBool DefaultDomain;                // was the browse started on an explicit domain?
     domainname type;                       // registration type
 };

 typedef struct DNSServiceResolver_struct DNSServiceResolver;
 struct DNSServiceResolver_struct
 {
     DNSServiceResolver *next;
     mach_port_t ClientMachPort;
     ServiceInfoQuery q;
     ServiceInfo i;
     mDNSs32 ReportTime;
 };

 // A single registered service: ServiceRecordSet + bookkeeping
 // Note that we duplicate some fields from parent DNSServiceRegistration object
 // to facilitate cleanup, when instances and parent may be deallocated at different times.
 typedef struct ServiceInstance
 {
     struct ServiceInstance *next;
     mach_port_t ClientMachPort;
     mDNSBool autoname;          // Set if this name is tied to the Computer Name
     mDNSBool renameonmemfree;   // Set if we just got a name conflict and now need to automatically pick a new name
     domainlabel name;
     domainname domain;
     ServiceRecordSet srs;
     // Don't add any fields after ServiceRecordSet.
     // This is where the implicit extra space goes if we allocate an oversized ServiceRecordSet object
 } ServiceInstance;

 // A client-created service.  May reference several ServiceInstance objects if default
 // settings cause registration in multiple domains.
 typedef struct DNSServiceRegistration
 {
     struct DNSServiceRegistration *next;
     mach_port_t ClientMachPort;
     mDNSBool DefaultDomain;
     mDNSBool autoname;
     size_t rdsize;
     int NumSubTypes;
     char regtype[MAX_ESCAPED_DOMAIN_NAME]; // for use in AllocateSubtypes
     domainlabel name;  // used only if autoname is false
     domainname type;
     mDNSIPPort port;
     unsigned char txtinfo[1024];
     size_t txt_len;
     uint32_t NextRef;
     ServiceInstance *regs;
 } DNSServiceRegistration;

 static DNSServiceDomainEnumeration *DNSServiceDomainEnumerationList = NULL;
 static DNSServiceBrowser           *DNSServiceBrowserList           = NULL;
 static DNSServiceResolver          *DNSServiceResolverList          = NULL;
 static DNSServiceRegistration      *DNSServiceRegistrationList      = NULL;

 // We keep a list of client-supplied event sources in KQSocketEventSource records
 typedef struct KQSocketEventSource
 {
     struct  KQSocketEventSource *next;
     int fd;
     KQueueEntry kqs;
 } KQSocketEventSource;

 static KQSocketEventSource *gEventSources;

 //*************************************************************************************************************
 #if COMPILER_LIKES_PRAGMA_MARK
 #pragma mark -
 #pragma mark - General Utility Functions
 #endif

 #if APPLE_OSX_mDNSResponder && MACOSX_MDNS_MALLOC_DEBUGGING

 char _malloc_options[] = "AXZ";

 mDNSexport void LogMemCorruption(const char *format, ...)
 {
     char buffer[512];
     va_list ptr;
     va_start(ptr,format);
     buffer[mDNS_vsnprintf((char *)buffer, sizeof(buffer), format, ptr)] = 0;
     va_end(ptr);
     LogMsg("!!!! %s !!!!", buffer);
     NotifyOfElusiveBug("Memory Corruption", buffer);
 #if ForceAlerts
     *(long*)0 = 0;  // Trick to crash and get a stack trace right here, if that's what we want
 #endif
 }

 mDNSlocal void validatelists(mDNS *const m)
 {
     // Check local lists
     KQSocketEventSource *k;
     for (k = gEventSources; k; k=k->next)
         if (k->next == (KQSocketEventSource *)~0 || k->fd < 0)
             LogMemCorruption("gEventSources: %p is garbage (%d)", k, k->fd);

     // Check Mach client lists
     DNSServiceDomainEnumeration *e;
     for (e = DNSServiceDomainEnumerationList; e; e=e->next)
         if (e->next == (DNSServiceDomainEnumeration *)~0 || e->ClientMachPort == 0 || e->ClientMachPort == (mach_port_t) ~0)
             LogMemCorruption("DNSServiceDomainEnumerationList: %p is garbage (%X)", e, e->ClientMachPort);

     DNSServiceBrowser           *b;
     for (b = DNSServiceBrowserList; b; b=b->next)
         if (b->next == (DNSServiceBrowser *)~0 || b->ClientMachPort == 0 || b->ClientMachPort == (mach_port_t) ~0)
             LogMemCorruption("DNSServiceBrowserList: %p is garbage (%X)", b, b->ClientMachPort);

     DNSServiceResolver          *l;
     for (l = DNSServiceResolverList; l; l=l->next)
         if (l->next == (DNSServiceResolver *)~0 || l->ClientMachPort == 0 || l->ClientMachPort == (mach_port_t) ~0)
             LogMemCorruption("DNSServiceResolverList: %p is garbage (%X)", l, l->ClientMachPort);

     DNSServiceRegistration      *r;
     for (r = DNSServiceRegistrationList; r; r=r->next)
         if (r->next == (DNSServiceRegistration *)~0 || r->ClientMachPort == 0 || r->ClientMachPort == (mach_port_t) ~0)
             LogMemCorruption("DNSServiceRegistrationList: %p is garbage (%X)", r, r->ClientMachPort);

     // Check Unix Domain Socket client lists (uds_daemon.c)
     uds_validatelists();

     // Check core mDNS lists
     AuthRecord                  *rr;
     for (rr = m->ResourceRecords; rr; rr=rr->next)
     {
         if (rr->next == (AuthRecord *)~0 || rr->resrec.RecordType == 0 || rr->resrec.RecordType == 0xFF)
             LogMemCorruption("ResourceRecords list: %p is garbage (%X)", rr, rr->resrec.RecordType);
         if (rr->resrec.name != &rr->namestorage)
             LogMemCorruption("ResourceRecords list: %p name %p does not point to namestorage %p %##s",
                              rr, rr->resrec.name->c, rr->namestorage.c, rr->namestorage.c);
     }

     for (rr = m->DuplicateRecords; rr; rr=rr->next)
         if (rr->next == (AuthRecord *)~0 || rr->resrec.RecordType == 0 || rr->resrec.RecordType == 0xFF)
             LogMemCorruption("DuplicateRecords list: %p is garbage (%X)", rr, rr->resrec.RecordType);

     rr = m->NewLocalRecords;
     if (rr)
         if (rr->next == (AuthRecord *)~0 || rr->resrec.RecordType == 0 || rr->resrec.RecordType == 0xFF)
             LogMemCorruption("NewLocalRecords: %p is garbage (%X)", rr, rr->resrec.RecordType);

     rr = m->CurrentRecord;
     if (rr)
         if (rr->next == (AuthRecord *)~0 || rr->resrec.RecordType == 0 || rr->resrec.RecordType == 0xFF)
             LogMemCorruption("CurrentRecord: %p is garbage (%X)", rr, rr->resrec.RecordType);

     DNSQuestion                 *q;
     for (q = m->Questions; q; q=q->next)
         if (q->next == (DNSQuestion*)~0 || q->ThisQInterval == (mDNSs32) ~0)
             LogMemCorruption("Questions list: %p is garbage (%lX %p)", q, q->ThisQInterval, q->next);

     CacheGroup                  *cg;
     CacheRecord                 *cr;
     mDNSu32 slot;
     FORALL_CACHERECORDS(slot, cg, cr)
     {
         if (cr->resrec.RecordType == 0 || cr->resrec.RecordType == 0xFF)
             LogMemCorruption("Cache slot %lu: %p is garbage (%X)", slot, cr, cr->resrec.RecordType);
         if (cr->CRActiveQuestion)
         {
             for (q = m->Questions; q; q=q->next) if (q == cr->CRActiveQuestion) break;
             if (!q) LogMemCorruption("Cache slot %lu: CRActiveQuestion %p not in m->Questions list %s", slot, cr->CRActiveQuestion, CRDisplayString(m, cr));
         }
     }

     // Check core uDNS lists
     udns_validatelists(m);

     // Check platform-layer lists
     NetworkInterfaceInfoOSX     *i;
     for (i = m->p->InterfaceList; i; i = i->next)
         if (i->next == (NetworkInterfaceInfoOSX *)~0 || !i->m || i->m == (mDNS *)~0)
             LogMemCorruption("m->p->InterfaceList: %p is garbage (%p)", i, i->ifinfo.ifname);

     ClientTunnel *t;
     for (t = m->TunnelClients; t; t=t->next)
         if (t->next == (ClientTunnel *)~0 || t->dstname.c[0] > 63)
             LogMemCorruption("m->TunnelClients: %p is garbage (%d)", t, t->dstname.c[0]);
 }

 mDNSexport void *mallocL(char *msg, unsigned int size)
 {
     // Allocate space for two words of sanity checking data before the requested block
     mDNSu32 *mem = malloc(sizeof(mDNSu32) * 2 + size);
     if (!mem)
     { LogMsg("malloc( %s : %d ) failed", msg, size); return(NULL); }
     else
     {
         if      (size > 24000) LogMsg("malloc( %s : %lu ) = %p suspiciously large", msg, size, &mem[2]);
         else if (MACOSX_MDNS_MALLOC_DEBUGGING >= 2) LogMsg("malloc( %s : %lu ) = %p",                    msg, size, &mem[2]);
         mem[0] = 0xDEAD1234;
         mem[1] = size;
         //mDNSPlatformMemZero(&mem[2], size);
         memset(&mem[2], 0xFF, size);
         validatelists(&mDNSStorage);
         return(&mem[2]);
     }
 }

 mDNSexport void freeL(char *msg, void *x)
 {
     if (!x)
         LogMsg("free( %s @ NULL )!", msg);
     else
     {
         mDNSu32 *mem = ((mDNSu32 *)x) - 2;
         if      (mem[0] != 0xDEAD1234)            { LogMsg("free( %s @ %p ) !!!! NOT ALLOCATED !!!!", msg, &mem[2]); return; }
         if      (mem[1] > 24000) LogMsg("free( %s : %ld @ %p) suspiciously large", msg, mem[1], &mem[2]);
         else if (MACOSX_MDNS_MALLOC_DEBUGGING >= 2) LogMsg("free( %s : %ld @ %p)",                    msg, mem[1], &mem[2]);
         //mDNSPlatformMemZero(mem, sizeof(mDNSu32) * 2 + mem[1]);
         memset(mem, 0xFF, sizeof(mDNSu32) * 2 + mem[1]);
         validatelists(&mDNSStorage);
         free(mem);
     }
 }

 #endif

 //*************************************************************************************************************
 #if COMPILER_LIKES_PRAGMA_MARK
 #pragma mark -
 #pragma mark - Mach client request handlers
 #endif

 //*************************************************************************************************************
 // Client Death Detection

 // This gets called after ALL constituent records of the Service Record Set have been deregistered
 mDNSlocal void FreeServiceInstance(ServiceInstance *x)
 {
     ServiceRecordSet *s = &x->srs;
     ExtraResourceRecord *e = x->srs.Extras, *tmp;

     while (e)
     {
         e->r.RecordContext = e;
         tmp = e;
         e = e->next;
         FreeExtraRR(&mDNSStorage, &tmp->r, mStatus_MemFree);
     }

     if (s->RR_TXT.resrec.rdata != &s->RR_TXT.rdatastorage)
         freeL("TXT RData", s->RR_TXT.resrec.rdata);

     if (s->SubTypes) freeL("ServiceSubTypes", s->SubTypes);
     freeL("ServiceInstance", x);
 }

 // AbortClient finds whatever client is identified by the given Mach port,
 // stops whatever operation that client was doing, and frees its memory.
 // In the case of a service registration, the actual freeing may be deferred
 // until we get the mStatus_MemFree message, if necessary
 mDNSlocal void AbortClient(mach_port_t ClientMachPort, void *m)
 {
     DNSServiceDomainEnumeration **e = &DNSServiceDomainEnumerationList;
     DNSServiceBrowser           **b = &DNSServiceBrowserList;
     DNSServiceResolver          **l = &DNSServiceResolverList;
     DNSServiceRegistration      **r = &DNSServiceRegistrationList;

     while (*e && (*e)->ClientMachPort != ClientMachPort) e = &(*e)->next;
     if (*e)
     {
         DNSServiceDomainEnumeration *x = *e;
         *e = (*e)->next;
         if (m && m != x)
             LogMsg("%5d: DNSServiceDomainEnumeration(%##s) STOP; WARNING m %p != x %p", ClientMachPort, x->dom.qname.c, m, x);
         else LogOperation("%5d: DNSServiceDomainEnumeration(%##s) STOP", ClientMachPort, x->dom.qname.c);
         mDNS_StopGetDomains(&mDNSStorage, &x->dom);
         mDNS_StopGetDomains(&mDNSStorage, &x->def);
         freeL("DNSServiceDomainEnumeration", x);
         return;
     }

     while (*b && (*b)->ClientMachPort != ClientMachPort) b = &(*b)->next;
     if (*b)
     {
         DNSServiceBrowser *x = *b;
         DNSServiceBrowserQuestion *freePtr, *qptr = x->qlist;
         *b = (*b)->next;
         while (qptr)
         {
             if (m && m != x)
                 LogMsg("%5d: DNSServiceBrowse(%##s) STOP; WARNING m %p != x %p", ClientMachPort, qptr->q.qname.c, m, x);
             else LogOperation("%5d: DNSServiceBrowse(%##s) STOP", ClientMachPort, qptr->q.qname.c);
             mDNS_StopBrowse(&mDNSStorage, &qptr->q);
             freePtr = qptr;
             qptr = qptr->next;
             freeL("DNSServiceBrowserQuestion", freePtr);
         }
         while (x->results)
         {
             DNSServiceBrowserResult *t = x->results;
             x->results = x->results->next;
             freeL("DNSServiceBrowserResult", t);
         }
         freeL("DNSServiceBrowser", x);
         return;
     }

     while (*l && (*l)->ClientMachPort != ClientMachPort) l = &(*l)->next;
     if (*l)
     {
         DNSServiceResolver *x = *l;
         *l = (*l)->next;
         if (m && m != x)
             LogMsg("%5d: DNSServiceResolve(%##s) STOP; WARNING m %p != x %p", ClientMachPort, x->i.name.c, m, x);
         else LogOperation("%5d: DNSServiceResolve(%##s) STOP", ClientMachPort, x->i.name.c);
         mDNS_StopResolveService(&mDNSStorage, &x->q);
         freeL("DNSServiceResolver", x);
         return;
     }

     while (*r && (*r)->ClientMachPort != ClientMachPort) r = &(*r)->next;
     if (*r)
     {
         ServiceInstance *si = NULL;
         DNSServiceRegistration *x = *r;
         *r = (*r)->next;

         si = x->regs;
         while (si)
         {
             ServiceInstance *instance = si;
             si = si->next;
             instance->renameonmemfree = mDNSfalse;
             if (m && m != x) LogMsg("%5d: DNSServiceRegistration(%##s, %u) STOP; WARNING m %p != x %p", ClientMachPort, instance->srs.RR_SRV.resrec.name->c, SRS_PORT(&instance->srs), m, x);
             else LogOperation("%5d: DNSServiceRegistration(%##s, %u) STOP", ClientMachPort, instance->srs.RR_SRV.resrec.name->c, SRS_PORT(&instance->srs));

             // If mDNS_DeregisterService() returns mStatus_NoError, that means that the service was found in the list,
             // is sending its goodbye packet, and we'll get an mStatus_MemFree message when we can free the memory.
             // If mDNS_DeregisterService() returns an error, it means that the service had already been removed from
             // the list, so we should go ahead and free the memory right now
             if (mDNS_DeregisterService(&mDNSStorage, &instance->srs)) FreeServiceInstance(instance); // FreeServiceInstance invalidates pointer
         }
         x->regs = NULL;
         freeL("DNSServiceRegistration", x);
         return;
     }

     LogMsg("%5d: died or deallocated, but no record of client can be found!", ClientMachPort);
 }

 #define AbortBlockedClient(C,MSG,M) AbortClientWithLogMessage((C), "stopped accepting Mach messages", " (" MSG ")", (M))

 mDNSlocal void AbortClientWithLogMessage(mach_port_t c, char *reason, char *msg, void *m)
 {
     DNSServiceDomainEnumeration *e = DNSServiceDomainEnumerationList;
     DNSServiceBrowser           *b = DNSServiceBrowserList;
     DNSServiceResolver          *l = DNSServiceResolverList;
     DNSServiceRegistration      *r = DNSServiceRegistrationList;
     DNSServiceBrowserQuestion   *qptr;

     while (e && e->ClientMachPort != c) e = e->next;
     while (b && b->ClientMachPort != c) b = b->next;
     while (l && l->ClientMachPort != c) l = l->next;
     while (r && r->ClientMachPort != c) r = r->next;

     if      (e) LogMsg("%5d: DomainEnumeration(%##s) %s%s",                   c, e->dom.qname.c,                reason, msg);
     else if (b)
     {
         for (qptr = b->qlist; qptr; qptr = qptr->next)
             LogMsg("%5d: Browser(%##s) %s%s",                             c, qptr->q.qname.c,               reason, msg);
     }
     else if (l) LogMsg("%5d: Resolver(%##s) %s%s",                            c, l->i.name.c,                   reason, msg);
     else if (r)
     {
         ServiceInstance *si;
         for (si = r->regs; si; si = si->next)
             LogMsg("%5d: Registration(%##s) %s%s",                        c, si->srs.RR_SRV.resrec.name->c, reason, msg);
     }
     else LogMsg("%5d: (%s) %s, but no record of client can be found!", c,                                reason, msg);

     AbortClient(c, m);
 }

 mDNSlocal mDNSBool CheckForExistingClient(mach_port_t c)
 {
     DNSServiceDomainEnumeration *e = DNSServiceDomainEnumerationList;
     DNSServiceBrowser           *b = DNSServiceBrowserList;
     DNSServiceResolver          *l = DNSServiceResolverList;
     DNSServiceRegistration      *r = DNSServiceRegistrationList;
     DNSServiceBrowserQuestion   *qptr;

     while (e && e->ClientMachPort != c) e = e->next;
     while (b && b->ClientMachPort != c) b = b->next;
     while (l && l->ClientMachPort != c) l = l->next;
     while (r && r->ClientMachPort != c) r = r->next;
     if (e) LogMsg("%5d: DomainEnumeration(%##s) already exists!", c, e->dom.qname.c);
     if (b)
     {
         for (qptr = b->qlist; qptr; qptr = qptr->next)
             LogMsg("%5d: Browser(%##s) already exists!",          c, qptr->q.qname.c);
     }
     if (l) LogMsg("%5d: Resolver(%##s) already exists!",          c, l->i.name.c);
     if (r) LogMsg("%5d: Registration(%##s) already exists!",      c, r->regs ? r->regs->srs.RR_SRV.resrec.name->c : NULL);
     return(e || b || l || r);
 }

 #ifndef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 mDNSlocal void ClientDeathCallback(CFMachPortRef unusedport, void *voidmsg, CFIndex size, void *info)
 {
     KQueueLock(&mDNSStorage);
     mach_msg_header_t *msg = (mach_msg_header_t *)voidmsg;
     (void)unusedport; // Unused
     (void)size; // Unused
     (void)info; // Unused
     if (msg->msgh_id == MACH_NOTIFY_DEAD_NAME)
     {
         const mach_dead_name_notification_t *const deathMessage = (mach_dead_name_notification_t *)msg;
         AbortClient(deathMessage->not_port, NULL);

         /* Deallocate the send right that came in the dead name notification */
         mach_port_destroy(mach_task_self(), deathMessage->not_port);
     }
     KQueueUnlock(&mDNSStorage, "Mach AbortClient");
 }

 #endif // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 mDNSlocal void EnableDeathNotificationForClient(mach_port_t ClientMachPort, void *m)
 {
 #ifdef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM
     dispatch_source_t mach_source = dispatch_source_create(DISPATCH_SOURCE_TYPE_MACH_SEND, ClientMachPort, 0, dispatch_get_main_queue());
     if (mach_source == mDNSNULL)
     {
         AbortClientWithLogMessage(ClientMachPort, "died/deallocated before we could enable death notification", "", m);
         return;
     }
     dispatch_source_set_event_handler(mach_source, ^{
                                           mach_port_destroy(mach_task_self(), ClientMachPort);
                                       });
     dispatch_resume(mach_source);
 #else // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM
     mach_port_t prev;
     kern_return_t r = mach_port_request_notification(mach_task_self(), ClientMachPort, MACH_NOTIFY_DEAD_NAME, 0,
                                                      client_death_port, MACH_MSG_TYPE_MAKE_SEND_ONCE, &prev);
     // If the port already died while we were thinking about it, then abort the operation right away
     if (r != KERN_SUCCESS)
         AbortClientWithLogMessage(ClientMachPort, "died/deallocated before we could enable death notification", "", m);
 #endif // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM
 }

 //*************************************************************************************************************
 // Domain Enumeration

 mDNSlocal void DomainEnumFound(mDNS *const m, DNSQuestion *question, const ResourceRecord *const answer, QC_result AddRecord)
 {
     kern_return_t status;
     char buffer[MAX_ESCAPED_DOMAIN_NAME];
     DNSServiceDomainEnumerationReplyResultType rt;
     DNSServiceDomainEnumeration *x = (DNSServiceDomainEnumeration *)question->QuestionContext;
     (void)m; // Unused

     debugf("DomainEnumFound: %##s PTR %##s", answer->name->c, answer->rdata->u.name.c);
     if (answer->rrtype != kDNSType_PTR) return;
     if (!x) { debugf("DomainEnumFound: DNSServiceDomainEnumeration is NULL"); return; }

     if (AddRecord)
     {
         if (question == &x->dom) rt = DNSServiceDomainEnumerationReplyAddDomain;
         else rt = DNSServiceDomainEnumerationReplyAddDomainDefault;
     }
     else
     {
         if (question == &x->dom) rt = DNSServiceDomainEnumerationReplyRemoveDomain;
         else return;
     }

     LogOperation("%5d: DNSServiceDomainEnumeration(%##s) %##s %s",
                  x->ClientMachPort, x->dom.qname.c, answer->rdata->u.name.c,
                  !AddRecord ? "RemoveDomain" :
                  question == &x->dom ? "AddDomain" : "AddDomainDefault");

     ConvertDomainNameToCString(&answer->rdata->u.name, buffer);
     status = DNSServiceDomainEnumerationReply_rpc(x->ClientMachPort, rt, buffer, 0, MDNS_MM_TIMEOUT);
     if (status == MACH_SEND_TIMED_OUT)
         AbortBlockedClient(x->ClientMachPort, "enumeration", x);
 }

 mDNSexport kern_return_t provide_DNSServiceDomainEnumerationCreate_rpc(mach_port_t unusedserver, mach_port_t client,
                                                                        int regDom)
 {
     // Check client parameter
     (void)unusedserver; // Unused
     mStatus err = mStatus_NoError;
     const char *errormsg = "Unknown";
     if (client == (mach_port_t)-1)      { err = mStatus_Invalid; errormsg = "Client id -1 invalid";     goto fail; }
     if (CheckForExistingClient(client)) { err = mStatus_Invalid; errormsg = "Client id already in use"; goto fail; }

     mDNS_DomainType dt1 = regDom ? mDNS_DomainTypeRegistration        : mDNS_DomainTypeBrowse;
     mDNS_DomainType dt2 = regDom ? mDNS_DomainTypeRegistrationDefault : mDNS_DomainTypeBrowseDefault;

     // Allocate memory, and handle failure
     DNSServiceDomainEnumeration *x = mallocL("DNSServiceDomainEnumeration", sizeof(*x));
     if (!x) { err = mStatus_NoMemoryErr; errormsg = "No memory"; goto fail; }

     // Set up object, and link into list
     x->ClientMachPort = client;
     x->next = DNSServiceDomainEnumerationList;
     DNSServiceDomainEnumerationList = x;

     verbosedebugf("%5d: Enumerate %s Domains", client, regDom ? "Registration" : "Browsing");

     // Do the operation
     err           = mDNS_GetDomains(&mDNSStorage, &x->dom, dt1, NULL, mDNSInterface_LocalOnly, DomainEnumFound, x);
     if (!err) err = mDNS_GetDomains(&mDNSStorage, &x->def, dt2, NULL, mDNSInterface_LocalOnly, DomainEnumFound, x);
     if (err) { AbortClient(client, x); errormsg = "mDNS_GetDomains"; goto fail; }

     // Succeeded: Wrap up and return
     LogOperation("%5d: DNSServiceDomainEnumeration(%##s) START", client, x->dom.qname.c);
     EnableDeathNotificationForClient(client, x);
     return(mStatus_NoError);

 fail:
     LogMsg("%5d: DNSServiceDomainEnumeration(%d) failed: %s (%d)", client, regDom, errormsg, err);
     return(err);
 }

 //*************************************************************************************************************
 // Browse for services

 mDNSlocal void FoundInstance(mDNS *const m, DNSQuestion *question, const ResourceRecord *const answer, QC_result AddRecord)
 {
     (void)m;        // Unused

     if (answer->rrtype != kDNSType_PTR)
     { LogMsg("FoundInstance: Should not be called with rrtype %d (not a PTR record)", answer->rrtype); return; }

     domainlabel name;
     domainname type, domain;
     if (!DeconstructServiceName(&answer->rdata->u.name, &name, &type, &domain))
     {
         LogMsg("FoundInstance: %##s PTR %##s received from network is not valid DNS-SD service pointer",
                answer->name->c, answer->rdata->u.name.c);
         return;
     }

     DNSServiceBrowserResult *x = mallocL("DNSServiceBrowserResult", sizeof(*x));
     if (!x) { LogMsg("FoundInstance: Failed to allocate memory for result %##s", answer->rdata->u.name.c); return; }

     verbosedebugf("FoundInstance: %s %##s", AddRecord ? "Add" : "Rmv", answer->rdata->u.name.c);
     AssignDomainName(&x->result, &answer->rdata->u.name);
     if (AddRecord)
         x->resultType = DNSServiceBrowserReplyAddInstance;
     else x->resultType = DNSServiceBrowserReplyRemoveInstance;
     x->next = NULL;

     DNSServiceBrowser *browser = (DNSServiceBrowser *)question->QuestionContext;
     DNSServiceBrowserResult **p = &browser->results;
     while (*p) p = &(*p)->next;
     *p = x;

     LogOperation("%5d: DNSServiceBrowse(%##s, %s) RESULT %s %s",
                  browser->ClientMachPort, question->qname.c, DNSTypeName(question->qtype), AddRecord ? "Add" : "Rmv", RRDisplayString(m, answer));
 }

 mDNSlocal mStatus AddDomainToBrowser(DNSServiceBrowser *browser, const domainname *d)
 {
     mStatus err = mStatus_NoError;
     DNSServiceBrowserQuestion *ptr, *question = NULL;

     for (ptr = browser->qlist; ptr; ptr = ptr->next)
     {
         if (SameDomainName(&ptr->q.qname, d))
         { debugf("Domain %##s already contained in browser", d->c); return mStatus_AlreadyRegistered; }
     }

     question = mallocL("DNSServiceBrowserQuestion", sizeof(DNSServiceBrowserQuestion));
     if (!question) { LogMsg("Error: malloc"); return mStatus_NoMemoryErr; }
     AssignDomainName(&question->domain, d);
     question->next = browser->qlist;
     LogOperation("%5d: DNSServiceBrowse(%##s%##s) START", browser->ClientMachPort, browser->type.c, d->c);
     err = mDNS_StartBrowse(&mDNSStorage, &question->q, &browser->type, d, mDNSInterface_Any, 0, mDNSfalse, mDNSfalse, FoundInstance, browser);
     if (!err)
         browser->qlist = question;
     else
     {
         LogMsg("Error: AddDomainToBrowser: mDNS_StartBrowse %d", err);
         freeL("DNSServiceBrowserQuestion", question);
     }
     return err;
 }

 mDNSexport void machserver_automatic_browse_domain_changed(const domainname *d, mDNSBool add)
 {
     DNSServiceBrowser *ptr;
     for (ptr = DNSServiceBrowserList; ptr; ptr = ptr->next)
     {
         if (ptr->DefaultDomain)
         {
             if (add)
             {
                 mStatus err = AddDomainToBrowser(ptr, d);
                 if (err && err != mStatus_AlreadyRegistered) LogMsg("Default browse in domain %##s for client %5d failed. Continuing", d, ptr->ClientMachPort);
             }
             else
             {
                 DNSServiceBrowserQuestion **q = &ptr->qlist;
                 while (*q)
                 {
                     if (SameDomainName(&(*q)->domain, d))
                     {
                         DNSServiceBrowserQuestion *rem = *q;
                         *q = (*q)->next;
                         mDNS_StopQueryWithRemoves(&mDNSStorage, &rem->q);
                         freeL("DNSServiceBrowserQuestion", rem);
                         return;
                     }
                     q = &(*q)->next;
                 }
                 LogMsg("Requested removal of default domain %##s not in client %5d's list", d->c, ptr->ClientMachPort);
             }
         }
     }
 }

 mDNSexport kern_return_t provide_DNSServiceBrowserCreate_rpc(mach_port_t unusedserver, mach_port_t client,
                                                              DNSCString regtype, DNSCString domain)
 {
     // Check client parameter
     (void)unusedserver;     // Unused
     mStatus err = mStatus_NoError;
     const char *errormsg = "Unknown";

     if (client == (mach_port_t)-1)      { err = mStatus_Invalid; errormsg = "Client id -1 invalid";     goto fail; }
     if (CheckForExistingClient(client)) { err = mStatus_Invalid; errormsg = "Client id already in use"; goto fail; }

     // Check other parameters
     domainname t, d;
     t.c[0] = 0;
     mDNSs32 NumSubTypes = ChopSubTypes(regtype);    // Note: Modifies regtype string to remove trailing subtypes
     if (NumSubTypes < 0 || NumSubTypes > 1)               { errormsg = "Bad Service SubType"; goto badparam; }
     if (NumSubTypes == 1 && !AppendDNSNameString(&t, regtype + strlen(regtype) + 1))
     { errormsg = "Bad Service SubType"; goto badparam; }
     if (!regtype[0] || !AppendDNSNameString(&t, regtype)) { errormsg = "Illegal regtype";     goto badparam; }
     domainname temp;
     if (!MakeDomainNameFromDNSNameString(&temp, regtype)) { errormsg = "Illegal regtype";     goto badparam; }
     if (temp.c[0] > 15 && (!domain || domain[0] == 0)) domain = "local."; // For over-long service types, we only allow domain "local"

     // Allocate memory, and handle failure
     DNSServiceBrowser *x = mallocL("DNSServiceBrowser", sizeof(*x));
     if (!x) { err = mStatus_NoMemoryErr; errormsg = "No memory"; goto fail; }

     // Set up object, and link into list
     AssignDomainName(&x->type, &t);
     x->ClientMachPort = client;
     x->results = NULL;
     x->lastsuccess = 0;
     x->qlist = NULL;
     x->next = DNSServiceBrowserList;
     DNSServiceBrowserList = x;

     if (domain[0])
     {
         // Start browser for an explicit domain
         x->DefaultDomain = mDNSfalse;
         if (!MakeDomainNameFromDNSNameString(&d, domain)) { errormsg = "Illegal domain";  goto badparam; }
         err = AddDomainToBrowser(x, &d);
         if (err) { AbortClient(client, x); errormsg = "AddDomainToBrowser"; goto fail; }
     }
     else
     {
         DNameListElem *sdPtr;
         // Start browser on all domains
         x->DefaultDomain = mDNStrue;
         if (!AutoBrowseDomains) { AbortClient(client, x); errormsg = "GetSearchDomainList"; goto fail; }
         for (sdPtr = AutoBrowseDomains; sdPtr; sdPtr = sdPtr->next)
         {
             err = AddDomainToBrowser(x, &sdPtr->name);
             if (err)
             {
                 // only terminally bail if .local fails
                 if (!SameDomainName(&localdomain, &sdPtr->name))
                     LogMsg("Default browse in domain %##s failed. Continuing", sdPtr->name.c);
                 else { AbortClient(client, x); errormsg = "AddDomainToBrowser"; goto fail; }
             }
         }
     }

     // Succeeded: Wrap up and return
     EnableDeathNotificationForClient(client, x);
     return(mStatus_NoError);

 badparam:
     err = mStatus_BadParamErr;
 fail:
     LogMsg("%5d: DNSServiceBrowse(\"%s\", \"%s\") failed: %s (%d)", client, regtype, domain, errormsg, err);
     return(err);
 }

 //*************************************************************************************************************
 // Resolve Service Info

 mDNSlocal void FoundInstanceInfo(mDNS *const m, ServiceInfoQuery *query)
 {
     kern_return_t status;
     DNSServiceResolver *x = (DNSServiceResolver *)query->ServiceInfoQueryContext;
     NetworkInterfaceInfoOSX *ifx = IfindexToInterfaceInfoOSX(m, query->info->InterfaceID);
     if (query->info->InterfaceID == mDNSInterface_LocalOnly || query->info->InterfaceID == mDNSInterface_P2P) ifx = mDNSNULL;
     struct sockaddr_storage interface;
     struct sockaddr_storage address;
     char cstring[1024];
     int i, pstrlen = query->info->TXTinfo[0];
     (void)m;        // Unused

     //debugf("FoundInstanceInfo %.4a %.4a %##s", &query->info->InterfaceAddr, &query->info->ip, &query->info->name);

     if (query->info->TXTlen > sizeof(cstring)) return;

     mDNSPlatformMemZero(&interface, sizeof(interface));
     mDNSPlatformMemZero(&address,   sizeof(address));

     if (ifx && ifx->ifinfo.ip.type == mDNSAddrType_IPv4)
     {
         struct sockaddr_in *s = (struct sockaddr_in*)&interface;
         s->sin_len         = sizeof(*s);
         s->sin_family      = AF_INET;
         s->sin_port        = 0;
         s->sin_addr.s_addr = ifx->ifinfo.ip.ip.v4.NotAnInteger;
     }
     else if (ifx && ifx->ifinfo.ip.type == mDNSAddrType_IPv6)
     {
         struct sockaddr_in6 *sin6 = (struct sockaddr_in6*)&interface;
         sin6->sin6_len       = sizeof(*sin6);
         sin6->sin6_family    = AF_INET6;
         sin6->sin6_flowinfo  = 0;
         sin6->sin6_port      = 0;
         sin6->sin6_addr      = *(struct in6_addr*)&ifx->ifinfo.ip.ip.v6;
         sin6->sin6_scope_id  = ifx->scope_id;
     }

     if (query->info->ip.type == mDNSAddrType_IPv4)
     {
         struct sockaddr_in *s = (struct sockaddr_in*)&address;
         s->sin_len         = sizeof(*s);
         s->sin_family      = AF_INET;
         s->sin_port        = query->info->port.NotAnInteger;
         s->sin_addr.s_addr = query->info->ip.ip.v4.NotAnInteger;
     }
     else
     {
         struct sockaddr_in6 *sin6 = (struct sockaddr_in6*)&address;
         sin6->sin6_len           = sizeof(*sin6);
         sin6->sin6_family        = AF_INET6;
         sin6->sin6_port          = query->info->port.NotAnInteger;
         sin6->sin6_flowinfo      = 0;
         sin6->sin6_addr          = *(struct in6_addr*)&query->info->ip.ip.v6;
         sin6->sin6_scope_id      = ifx ? ifx->scope_id : 0;
     }

     // The OS X DNSServiceResolverResolve() API is defined using a C-string,
     // but the mDNS_StartResolveService() call actually returns a packed block of P-strings.
     // Hence we have to convert the P-string(s) to a C-string before returning the result to the client.
     // ASCII-1 characters are used in the C-string as boundary markers,
     // to indicate the boundaries between the original constituent P-strings.
     for (i=1; i<query->info->TXTlen; i++)
     {
         if (--pstrlen >= 0)
             cstring[i-1] = query->info->TXTinfo[i];
         else
         {
             cstring[i-1] = 1;
             pstrlen = query->info->TXTinfo[i];
         }
     }
     cstring[i-1] = 0;       // Put the terminating NULL on the end

     LogOperation("%5d: DNSServiceResolver(%##s) -> %#a:%u", x->ClientMachPort,
                  x->i.name.c, &query->info->ip, mDNSVal16(query->info->port));
     status = DNSServiceResolverReply_rpc(x->ClientMachPort,
                                          (char*)&interface, (char*)&address, cstring, 0, MDNS_MM_TIMEOUT);
     if (status == MACH_SEND_TIMED_OUT)
         AbortBlockedClient(x->ClientMachPort, "resolve", x);
 }

 mDNSexport kern_return_t provide_DNSServiceResolverResolve_rpc(mach_port_t unusedserver, mach_port_t client,
                                                                DNSCString name, DNSCString regtype, DNSCString domain)
 {
     // Check client parameter
     (void)unusedserver;     // Unused
     mStatus err = mStatus_NoError;
     const char *errormsg = "Unknown";
     if (client == (mach_port_t)-1)      { err = mStatus_Invalid; errormsg = "Client id -1 invalid";     goto fail; }
     if (CheckForExistingClient(client)) { err = mStatus_Invalid; errormsg = "Client id already in use"; goto fail; }

     // Check other parameters
     domainlabel n;
     domainname t, d, srv;
     if (!name[0]    || !MakeDomainLabelFromLiteralString(&n, name))        { errormsg = "Bad Instance Name"; goto badparam; }
     if (!regtype[0] || !MakeDomainNameFromDNSNameString(&t, regtype))      { errormsg = "Bad Service Type";  goto badparam; }
     if (!domain[0]  || !MakeDomainNameFromDNSNameString(&d, domain))       { errormsg = "Bad Domain";        goto badparam; }
     if (!ConstructServiceName(&srv, &n, &t, &d))                           { errormsg = "Bad Name";          goto badparam; }

     // Allocate memory, and handle failure
     DNSServiceResolver *x = mallocL("DNSServiceResolver", sizeof(*x));
     if (!x) { err = mStatus_NoMemoryErr; errormsg = "No memory"; goto fail; }

     // Set up object, and link into list
     x->ClientMachPort = client;
     x->i.InterfaceID = mDNSInterface_Any;
     x->i.name = srv;
     x->ReportTime = NonZeroTime(mDNS_TimeNow(&mDNSStorage) + 130 * mDNSPlatformOneSecond);
     x->next = DNSServiceResolverList;
     DNSServiceResolverList = x;

     // Do the operation
     LogOperation("%5d: DNSServiceResolve(%##s) START", client, x->i.name.c);
     err = mDNS_StartResolveService(&mDNSStorage, &x->q, &x->i, FoundInstanceInfo, x);
     if (err) { AbortClient(client, x); errormsg = "mDNS_StartResolveService"; goto fail; }

     // Succeeded: Wrap up and return
     EnableDeathNotificationForClient(client, x);
     return(mStatus_NoError);

 badparam:
     err = mStatus_BadParamErr;
 fail:
     LogMsg("%5d: DNSServiceResolve(\"%s\", \"%s\", \"%s\") failed: %s (%d)", client, name, regtype, domain, errormsg, err);
     return(err);
 }

 //*************************************************************************************************************
 // Registration

 mDNSexport void RecordUpdatedNiceLabel(mDNS *const m, mDNSs32 delay)
 {
     m->p->NotifyUser = NonZeroTime(m->timenow + delay);
 }

 mDNSlocal void RegCallback(mDNS *const m, ServiceRecordSet *const srs, mStatus result)
 {
     ServiceInstance *si = (ServiceInstance*)srs->ServiceContext;

     if (result == mStatus_NoError)
     {
         kern_return_t status;
         LogOperation("%5d: DNSServiceRegistration(%##s, %u) Name Registered", si->ClientMachPort, srs->RR_SRV.resrec.name->c, SRS_PORT(srs));
         status = DNSServiceRegistrationReply_rpc(si->ClientMachPort, result, MDNS_MM_TIMEOUT);
         if (status == MACH_SEND_TIMED_OUT)
             AbortBlockedClient(si->ClientMachPort, "registration success", si);
         if (si->autoname && CountPeerRegistrations(m, srs) == 0)
             RecordUpdatedNiceLabel(m, 0);   // Successfully got new name, tell user immediately
     }

     else if (result == mStatus_NameConflict)
     {
         LogOperation("%5d: DNSServiceRegistration(%##s, %u) Name Conflict", si->ClientMachPort, srs->RR_SRV.resrec.name->c, SRS_PORT(srs));
         // Note: By the time we get the mStatus_NameConflict message, the service is already deregistered
         // and the memory is free, so we don't have to wait for an mStatus_MemFree message as well.
         if (si->autoname && CountPeerRegistrations(m, srs) == 0)
         {
             // On conflict for an autoname service, rename and reregister *all* autoname services
             IncrementLabelSuffix(&m->nicelabel, mDNStrue);
             mDNS_ConfigChanged(m);
         }
         else if (si->autoname)
         {
             mDNS_RenameAndReregisterService(m, srs, mDNSNULL);
             return;
         }
         else
         {
             // If we get a name conflict, we tell the client about it, and then they are expected to dispose
             // of their registration in the usual way (which we will catch via client death notification).
             // If the Mach queue is full, we forcibly abort the client immediately.
             kern_return_t status = DNSServiceRegistrationReply_rpc(si->ClientMachPort, result, MDNS_MM_TIMEOUT);
             if (status == MACH_SEND_TIMED_OUT)
                 AbortBlockedClient(si->ClientMachPort, "registration conflict", NULL);
         }
     }

     else if (result == mStatus_MemFree)
     {
         if (si->renameonmemfree)    // We intentionally terminated registration so we could re-register with new name
         {
             debugf("RegCallback renaming %#s to %#s", si->name.c, m->nicelabel.c);
             si->renameonmemfree = mDNSfalse;
             si->name            = m->nicelabel;
             mDNS_RenameAndReregisterService(m, srs, &si->name);
         }
         else
         {
             // SANITY CHECK: make sure service instance is no longer in any ServiceRegistration's list
             DNSServiceRegistration *r;
             for (r = DNSServiceRegistrationList; r; r = r->next)
             {
                 ServiceInstance **sp = &r->regs;
                 while (*sp)
                 {
                     if (*sp == si) { LogMsg("RegCallback: %##s Still in list; removing", srs->RR_SRV.resrec.name->c); *sp = (*sp)->next; break; }
                     sp = &(*sp)->next;
                 }
             }
             // END SANITY CHECK
             FreeServiceInstance(si);
         }
     }

     else if (result != mStatus_NATTraversal)
         LogMsg("%5d: DNSServiceRegistration(%##s, %u) Unknown Result %d", si->ClientMachPort, srs->RR_SRV.resrec.name->c, SRS_PORT(srs), result);
 }

 mDNSlocal mStatus AddServiceInstance(DNSServiceRegistration *x, const domainname *domain)
 {
     mStatus err = 0;
     ServiceInstance *si = NULL;
     AuthRecord *SubTypes = NULL;

     for (si = x->regs; si; si = si->next)
     {
         if (SameDomainName(&si->domain, domain))
         { LogMsg("Requested addition of domain %##s already in list", domain->c); return mStatus_AlreadyRegistered; }
     }

     SubTypes = AllocateSubTypes(x->NumSubTypes, x->regtype);
     if (x->NumSubTypes && !SubTypes) return mStatus_NoMemoryErr;

     si = mallocL("ServiceInstance", sizeof(*si) - sizeof(RDataBody) + x->rdsize);
     if (!si) return mStatus_NoMemoryErr;

     si->ClientMachPort  = x->ClientMachPort;
     si->renameonmemfree = mDNSfalse;
     si->autoname        = x->autoname;
     si->name            = x->autoname ? mDNSStorage.nicelabel : x->name;
     si->domain          = *domain;

     err = mDNS_RegisterService(&mDNSStorage, &si->srs, &si->name, &x->type, domain, NULL,
                                x->port, x->txtinfo, x->txt_len, SubTypes, x->NumSubTypes, mDNSInterface_Any, RegCallback, si, 0);
     if (!err)
     {
         si->next = x->regs;
         x->regs = si;
     }
     else
     {
         LogMsg("Error %d for registration of service in domain %##s", err, domain->c);
         freeL("ServiceInstance", si);
     }
     return err;
 }

 mDNSexport void machserver_automatic_registration_domain_changed(const domainname *d, mDNSBool add)
 {
     DNSServiceRegistration *reg;

     for (reg = DNSServiceRegistrationList; reg; reg = reg->next)
     {
         if (reg->DefaultDomain)
         {
             if (add)
                 AddServiceInstance(reg, d);
             else
             {
                 ServiceInstance **si = &reg->regs;
                 while (*si)
                 {
                     if (SameDomainName(&(*si)->domain, d))
                     {
                         ServiceInstance *s = *si;
                         *si = (*si)->next;
                         if (mDNS_DeregisterService(&mDNSStorage, &s->srs)) FreeServiceInstance(s);  // only free memory synchronously on error
                         break;
                     }
                     si = &(*si)->next;
                 }
                 if (!si) debugf("Requested removal of default domain %##s not in client %5d's list", d, reg->ClientMachPort); // normal if registration failed
             }
         }
     }
 }

 mDNSexport kern_return_t provide_DNSServiceRegistrationCreate_rpc(mach_port_t unusedserver, mach_port_t client,
                                                                   DNSCString name, DNSCString regtype, DNSCString domain, IPPort IpPort, DNSCString txtRecord)
 {
     (void)unusedserver;     // Unused
     mStatus err = mStatus_NoError;
     const char *errormsg = "Unknown";

     // older versions of this code passed the port via mach IPC as an int.
     // we continue to pass it as 4 bytes to maintain binary compatibility,
     // but now ensure that the network byte order is preserved by using a struct
     mDNSIPPort port;
     port.b[0] = IpPort.bytes[2];
     port.b[1] = IpPort.bytes[3];

     if (client == (mach_port_t)-1)      { err = mStatus_Invalid; errormsg = "Client id -1 invalid";     goto fail; }
     if (CheckForExistingClient(client)) { err = mStatus_Invalid; errormsg = "Client id already in use"; goto fail; }

     // Check for sub-types after the service type
     size_t reglen = strlen(regtype) + 1;
     if (reglen > MAX_ESCAPED_DOMAIN_NAME) { errormsg = "reglen too long"; goto badparam; }
     mDNSs32 NumSubTypes = ChopSubTypes(regtype);    // Note: Modifies regtype string to remove trailing subtypes
     if (NumSubTypes < 0) { errormsg = "Bad Service SubType"; goto badparam; }

     // Check other parameters
     domainlabel n;
     domainname t, d;
     domainname srv;
     if (!name[0]) n = mDNSStorage.nicelabel;
     else if (!MakeDomainLabelFromLiteralString(&n, name))                  { errormsg = "Bad Instance Name"; goto badparam; }
     if (!regtype[0] || !MakeDomainNameFromDNSNameString(&t, regtype))      { errormsg = "Bad Service Type";  goto badparam; }
     if (!MakeDomainNameFromDNSNameString(&d, *domain ? domain : "local.")) { errormsg = "Bad Domain";        goto badparam; }
     if (!ConstructServiceName(&srv, &n, &t, &d))                           { errormsg = "Bad Name";          goto badparam; }

     unsigned char txtinfo[1024] = "";
     unsigned int data_len = 0;
     unsigned int size = sizeof(RDataBody);
     unsigned char *pstring = &txtinfo[data_len];
     char *ptr = txtRecord;

     // The OS X DNSServiceRegistrationCreate() API is defined using a C-string,
     // but the mDNS_RegisterService() call actually requires a packed block of P-strings.
     // Hence we have to convert the C-string to a P-string.
     // ASCII-1 characters are allowed in the C-string as boundary markers,
     // so that a single C-string can be used to represent one or more P-strings.
     while (*ptr)
     {
         if (++data_len >= sizeof(txtinfo)) { errormsg = "TXT record too long"; goto badtxt; }
         if (*ptr == 1)      // If this is our boundary marker, start a new P-string
         {
             pstring = &txtinfo[data_len];
             pstring[0] = 0;
             ptr++;
         }
         else
         {
             if (pstring[0] == 255) { errormsg = "TXT record invalid (component longer than 255)"; goto badtxt; }
             pstring[++pstring[0]] = *ptr++;
         }
     }

     data_len++;
     if (size < data_len)
         size = data_len;

     // Some clients use mDNS for lightweight copy protection, registering a pseudo-service with
     // a port number of zero. When two instances of the protected client are allowed to run on one
     // machine, we don't want to see misleading "Bogus client" messages in syslog and the console.
     if (!mDNSIPPortIsZero(port))
     {
         int count = CountExistingRegistrations(&srv, port);
         if (count)
             LogMsg("%5d: Client application registered %d identical instances of service %##s port %u.",
                    client, count+1, srv.c, mDNSVal16(port));
     }

     // Allocate memory, and handle failure
     DNSServiceRegistration *x = mallocL("DNSServiceRegistration", sizeof(*x));
     if (!x) { err = mStatus_NoMemoryErr; errormsg = "No memory"; goto fail; }
     mDNSPlatformMemZero(x, sizeof(*x));

     // Set up object, and link into list
     x->ClientMachPort = client;
     x->DefaultDomain = !domain[0];
     x->autoname = (!name[0]);
     x->rdsize = size;
     x->NumSubTypes = NumSubTypes;
     memcpy(x->regtype, regtype, reglen);
     x->name = n;
     x->type = t;
     x->port = port;
     memcpy(x->txtinfo, txtinfo, 1024);
     x->txt_len = data_len;
     x->NextRef = 0;
     x->regs = NULL;

     x->next = DNSServiceRegistrationList;
     DNSServiceRegistrationList = x;

     LogOperation("%5d: DNSServiceRegistration(\"%s\", \"%s\", \"%s\", %u) START",
                  x->ClientMachPort, name, regtype, domain, mDNSVal16(port));

     err = AddServiceInstance(x, &d);
     if (err) { AbortClient(client, x); errormsg = "mDNS_RegisterService"; goto fail; }  // bail if .local (or explicit domain) fails

     if (x->DefaultDomain)
     {
         DNameListElem *p;
         for (p = AutoRegistrationDomains; p; p = p->next)
             AddServiceInstance(x, &p->name);
     }

     // Succeeded: Wrap up and return
     EnableDeathNotificationForClient(client, x);
     return(mStatus_NoError);

 badtxt:
     LogMsg("%5d: TXT record: %.100s...", client, txtRecord);
 badparam:
     err = mStatus_BadParamErr;
 fail:
     LogMsg("%5d: DNSServiceRegister(\"%s\", \"%s\", \"%s\", %d) failed: %s (%d)",
            client, name, regtype, domain, mDNSVal16(port), errormsg, err);
     return(err);
 }

 mDNSlocal void mDNSPreferencesSetNames(mDNS *const m, int key, domainlabel *old, domainlabel *new)
 {
     domainlabel *prevold, *prevnew;
     switch (key)
     {
     case kmDNSComputerName:
     case kmDNSLocalHostName:
         if (key == kmDNSComputerName)
         {
             prevold = &m->p->prevoldnicelabel;
             prevnew = &m->p->prevnewnicelabel;
         }
         else
         {
             prevold = &m->p->prevoldhostlabel;
             prevnew = &m->p->prevnewhostlabel;
         }
         // There are a few cases where we need to invoke the helper.
         //
         // 1. If the "old" label and "new" label are not same, it means there is a conflict. We need
         //    to invoke the helper so that it pops up a dialogue to inform the user about the
         //    conflict
         //
         // 2. If the "old" label and "new" label are same, it means the user has set the host/nice label
         //    through the preferences pane. We may have to inform the helper as it may have popped up
         //    a dialogue previously (due to a conflict) and it needs to suppress it now. We can avoid invoking
         //    the helper in this case if the previous values (old and new) that we told helper last time
         //    are same. If the previous old and new values are same, helper does not care.
         //
         // Note: "new" can be NULL when we have repeated conflicts and we are asking helper to give up. "old"
         // is not called with NULL today, but this makes it future proof.
         if (!old || !new || !SameDomainLabelCS(old->c, new->c) ||
             !SameDomainLabelCS(old->c, prevold->c) ||
             !SameDomainLabelCS(new->c, prevnew->c))
         {
             if (old)
                 *prevold = *old;
             else
                 prevold->c[0] = 0;
             if (new)
                 *prevnew = *new;
             else
                 prevnew->c[0] = 0;
             mDNSPreferencesSetName(key, old, new);
         }
         else
         {
             LogInfo("mDNSPreferencesSetNames not invoking helper %s %#s, %s %#s, old %#s, new %#s",
                     (key == kmDNSComputerName ? "prevoldnicelabel" : "prevoldhostlabel"), prevold->c,
                     (key == kmDNSComputerName ? "prevnewnicelabel" : "prevnewhostlabel"), prevnew->c,
                     old->c, new->c);
         }
         break;
     default:
         LogMsg("mDNSPreferencesSetNames: unrecognized key: %d", key);
         return;
     }
 }

 mDNSlocal void mDNS_StatusCallback(mDNS *const m, mStatus result)
 {
     (void)m; // Unused
     if (result == mStatus_NoError)
     {
         if (!SameDomainLabelCS(m->p->userhostlabel.c, m->hostlabel.c))
             LogInfo("Local Hostname changed from \"%#s.local\" to \"%#s.local\"", m->p->userhostlabel.c, m->hostlabel.c);
         // One second pause in case we get a Computer Name update too -- don't want to alert the user twice
         RecordUpdatedNiceLabel(m, mDNSPlatformOneSecond);
     }
     else if (result == mStatus_NameConflict)
     {
         LogInfo("Local Hostname conflict for \"%#s.local\"", m->hostlabel.c);
         if (!m->p->HostNameConflict) m->p->HostNameConflict = NonZeroTime(m->timenow);
         else if (m->timenow - m->p->HostNameConflict > 60 * mDNSPlatformOneSecond)
         {
             // Tell the helper we've given up
             mDNSPreferencesSetNames(m, kmDNSLocalHostName, &m->p->userhostlabel, NULL);
         }
     }
     else if (result == mStatus_GrowCache)
     {
         // Allocate another chunk of cache storage
         CacheEntity *storage = mallocL("mStatus_GrowCache", sizeof(CacheEntity) * RR_CACHE_SIZE);
         //LogInfo("GrowCache %d * %d = %d", sizeof(CacheEntity), RR_CACHE_SIZE, sizeof(CacheEntity) * RR_CACHE_SIZE);
         if (storage) mDNS_GrowCache(m, storage, RR_CACHE_SIZE);
     }
     else if (result == mStatus_ConfigChanged)
     {
         // Tell the helper we've seen a change in the labels.  It will dismiss the name conflict alert if needed.
         mDNSPreferencesSetNames(m, kmDNSComputerName, &m->p->usernicelabel, &m->nicelabel);
         mDNSPreferencesSetNames(m, kmDNSLocalHostName, &m->p->userhostlabel, &m->hostlabel);

         // First we check our list of old Mach-based registered services, to see if any need to be updated to a new name
         DNSServiceRegistration *r;
         for (r = DNSServiceRegistrationList; r; r=r->next)
             if (r->autoname)
             {
                 ServiceInstance *si;
                 for (si = r->regs; si; si = si->next)
                 {
                     if (!SameDomainLabelCS(si->name.c, m->nicelabel.c))
                     {
                         debugf("NetworkChanged renaming %##s to %#s", si->srs.RR_SRV.resrec.name->c, m->nicelabel.c);
                         si->renameonmemfree = mDNStrue;
                         if (mDNS_DeregisterService_drt(m, &si->srs, mDNS_Dereg_rapid))
                             RegCallback(m, &si->srs, mStatus_MemFree);  // If service deregistered already, we can re-register immediately
                     }
                 }
             }

         // Then we call into the UDS daemon code, to let it do the same
         udsserver_handle_configchange(m);
     }
 }

 //*************************************************************************************************************
 // Add / Update / Remove records from existing Registration

 mDNSexport kern_return_t provide_DNSServiceRegistrationAddRecord_rpc(mach_port_t unusedserver, mach_port_t client,
                                                                      int type, const char *data, mach_msg_type_number_t data_len, uint32_t ttl, natural_t *reference)
 {
     // Check client parameter
     uint32_t id;
     mStatus err = mStatus_NoError;
     const char *errormsg = "Unknown";
     DNSServiceRegistration *x = DNSServiceRegistrationList;
     if (client == (mach_port_t)-1) { err = mStatus_Invalid;         errormsg = "Client id -1 invalid"; goto fail; }
     ServiceInstance *si;
     size_t size;
     (void)unusedserver;     // Unused
     while (x && x->ClientMachPort != client) x = x->next;
     if (!x)                        { err = mStatus_BadReferenceErr; errormsg = "No such client";       goto fail; }

     // Check other parameters
     if (data_len > 8192) { err = mStatus_BadParamErr; errormsg = "data_len > 8K"; goto fail; }
     if (data_len > sizeof(RDataBody)) size = data_len;
     else size = sizeof(RDataBody);

     id = x->NextRef++;
     *reference = (natural_t)id;
     for (si = x->regs; si; si = si->next)
     {
         // Allocate memory, and handle failure
         ExtraResourceRecord *extra = mallocL("ExtraResourceRecord", sizeof(*extra) - sizeof(RDataBody) + size);
         if (!extra) { err = mStatus_NoMemoryErr; errormsg = "No memory"; goto fail; }

         // Fill in type, length, and data of new record
         extra->r.resrec.rrtype = type;
         extra->r.rdatastorage.MaxRDLength = size;
         extra->r.resrec.rdlength          = data_len;
         memcpy(&extra->r.rdatastorage.u.data, data, data_len);

         // Do the operation
         LogOperation("%5d: DNSServiceRegistrationAddRecord(%##s, type %d, length %d) REF %p",
                      client, si->srs.RR_SRV.resrec.name->c, type, data_len, extra);
         err = mDNS_AddRecordToService(&mDNSStorage, &si->srs, extra, &extra->r.rdatastorage, ttl, 0);

         if (err)
         {
             freeL("Extra Resource Record", extra);
             errormsg = "mDNS_AddRecordToService";
             goto fail;
         }

         extra->ClientID = id;
     }

     return mStatus_NoError;

 fail:
     LogMsg("%5d: DNSServiceRegistrationAddRecord(%##s, type %d, length %d) failed: %s (%d)", client, x ? x->name.c : (mDNSu8*)"\x8" "«NULL»", type, data_len, errormsg, err);
     return mStatus_UnknownErr;
 }

 mDNSlocal void UpdateCallback(mDNS *const m, AuthRecord *const rr, RData *OldRData, mDNSu16 OldRDLen)
 {
     (void)m;        // Unused
     (void)OldRDLen; // Unused
     if (OldRData != &rr->rdatastorage)
         freeL("Old RData", OldRData);
 }

 mDNSlocal mStatus UpdateRecord(ServiceRecordSet *srs, mach_port_t client, AuthRecord *rr, const char *data, mach_msg_type_number_t data_len, uint32_t ttl)
 {
     // Check client parameter
     mStatus err = mStatus_NoError;
     const char *errormsg = "Unknown";
     const domainname *name = (const domainname *)"";

     name = srs->RR_SRV.resrec.name;

     unsigned int size = sizeof(RDataBody);
     if (size < data_len)
         size = data_len;

     // Allocate memory, and handle failure
     RData *newrdata = mallocL("RData", sizeof(*newrdata) - sizeof(RDataBody) + size);
     if (!newrdata) { err = mStatus_NoMemoryErr; errormsg = "No memory"; goto fail; }

     // Fill in new length, and data
     newrdata->MaxRDLength = size;
     memcpy(&newrdata->u, data, data_len);

     // BIND named (name daemon) doesn't allow TXT records with zero-length rdata. This is strictly speaking correct,
     // since RFC 1035 specifies a TXT record as "One or more <character-string>s", not "Zero or more <character-string>s".
     // Since some legacy apps try to create zero-length TXT records, we'll silently correct it here.
     if (rr->resrec.rrtype == kDNSType_TXT && data_len == 0) { data_len = 1; newrdata->u.txt.c[0] = 0; }

     // Do the operation
     LogOperation("%5d: DNSServiceRegistrationUpdateRecord(%##s, new length %d)",
                  client, srs->RR_SRV.resrec.name->c, data_len);

     err = mDNS_Update(&mDNSStorage, rr, ttl, data_len, newrdata, UpdateCallback);
     if (err)
     {
         errormsg = "mDNS_Update";
         freeL("RData", newrdata);
         return err;
     }
     return(mStatus_NoError);

 fail:
     LogMsg("%5d: DNSServiceRegistrationUpdateRecord(%##s, %d) failed: %s (%d)", client, name->c, data_len, errormsg, err);
     return(err);
 }

 mDNSexport kern_return_t provide_DNSServiceRegistrationUpdateRecord_rpc(mach_port_t unusedserver, mach_port_t client,
                                                                         natural_t reference, const char *data, mach_msg_type_number_t data_len, uint32_t ttl)
 {
     // Check client parameter
     mStatus err = mStatus_NoError;
     const char *errormsg = "Unknown";
     const domainname *name = (const domainname *)"";
     ServiceInstance *si;

     (void)unusedserver; // unused
     if (client == (mach_port_t)-1) { err = mStatus_Invalid;         errormsg = "Client id -1 invalid"; goto fail; }
     DNSServiceRegistration *x = DNSServiceRegistrationList;
     while (x && x->ClientMachPort != client) x = x->next;
     if (!x)                        { err = mStatus_BadReferenceErr; errormsg = "No such client";       goto fail; }

     // Check other parameters
     if (data_len > 8192) { err = mStatus_BadParamErr; errormsg = "data_len > 8K"; goto fail; }

     for (si = x->regs; si; si = si->next)
     {
         AuthRecord *r = NULL;

         // Find the record we're updating. NULL reference means update the primary TXT record
         if (!reference) r = &si->srs.RR_TXT;
         else
         {
             ExtraResourceRecord *ptr;
             for (ptr = si->srs.Extras; ptr; ptr = ptr->next)
             {
                 if ((natural_t)ptr->ClientID == reference)
                 { r = &ptr->r; break; }
             }
             if (!r) { err = mStatus_BadReferenceErr; errormsg = "No such record"; goto fail; }
         }
         err = UpdateRecord(&si->srs, client, r, data, data_len, ttl);
         if (err) goto fail;  //!!!KRS this will cause failures for non-local defaults!
     }

     return mStatus_NoError;

 fail:
     LogMsg("%5d: DNSServiceRegistrationUpdateRecord(%##s, %X, %d) failed: %s (%d)", client, name->c, reference, data_len, errormsg, err);
     return(err);
 }

 mDNSlocal mStatus RemoveRecord(ServiceRecordSet *srs, ExtraResourceRecord *extra, mach_port_t client)
 {
     const domainname *const name = srs->RR_SRV.resrec.name;
     mStatus err = mStatus_NoError;

     // Do the operation
     LogOperation("%5d: DNSServiceRegistrationRemoveRecord(%##s)", client, srs->RR_SRV.resrec.name->c);

     err = mDNS_RemoveRecordFromService(&mDNSStorage, srs, extra, FreeExtraRR, extra);
     if (err) LogMsg("%5d: DNSServiceRegistrationRemoveRecord (%##s) failed: %d", client, name->c, err);

     return err;
 }

 mDNSexport kern_return_t provide_DNSServiceRegistrationRemoveRecord_rpc(mach_port_t unusedserver, mach_port_t client,
                                                                         natural_t reference)
 {
     // Check client parameter
     (void)unusedserver;     // Unused
     mStatus err = mStatus_NoError;
     const char *errormsg = "Unknown";
     if (client == (mach_port_t)-1) { err = mStatus_Invalid;         errormsg = "Client id -1 invalid"; goto fail; }
     DNSServiceRegistration *x = DNSServiceRegistrationList;
     ServiceInstance *si;

     while (x && x->ClientMachPort != client) x = x->next;
     if (!x)                        { err = mStatus_BadReferenceErr; errormsg = "No such client";       goto fail; }

     for (si = x->regs; si; si = si->next)
     {
         ExtraResourceRecord *e;
         for (e = si->srs.Extras; e; e = e->next)
         {
             if ((natural_t)e->ClientID == reference)
             {
                 err = RemoveRecord(&si->srs, e, client);
                 break;
             }
         }
         if (!e) { err = mStatus_BadReferenceErr; errormsg = "No such reference"; goto fail; }
     }

     return mStatus_NoError;

 fail:
     LogMsg("%5d: DNSServiceRegistrationRemoveRecord(%X) failed: %s (%d)", client, reference, errormsg, err);
     return(err);
 }

 //*************************************************************************************************************
 #if COMPILER_LIKES_PRAGMA_MARK
 #pragma mark -
 #pragma mark - Startup, shutdown, and supporting code
 #endif

 mDNSlocal void DNSserverCallback(CFMachPortRef port, void *msg, CFIndex size, void *info)
 {
     mig_reply_error_t *request = msg;
     mig_reply_error_t *reply;
     mach_msg_return_t mr;
     int options;
     (void)port;     // Unused
     (void)size;     // Unused
     (void)info;     // Unused

     KQueueLock(&mDNSStorage);

     /* allocate a reply buffer */
     reply = CFAllocatorAllocate(NULL, provide_DNSServiceDiscoveryRequest_subsystem.maxsize, 0);

     /* call the MiG server routine */
     (void) DNSServiceDiscoveryRequest_server(&request->Head, &reply->Head);

     if (!(reply->Head.msgh_bits & MACH_MSGH_BITS_COMPLEX) && (reply->RetCode != KERN_SUCCESS))
     {
         if (reply->RetCode == MIG_NO_REPLY)
         {
             /*
              * This return code is a little tricky -- it appears that the
              * demux routine found an error of some sort, but since that
              * error would not normally get returned either to the local
              * user or the remote one, we pretend it's ok.
              */
             CFAllocatorDeallocate(NULL, reply);
             goto done;
         }

         /*
          * destroy any out-of-line data in the request buffer but don't destroy
          * the reply port right (since we need that to send an error message).
          */
         request->Head.msgh_remote_port = MACH_PORT_NULL;
         mach_msg_destroy(&request->Head);
     }

     if (reply->Head.msgh_remote_port == MACH_PORT_NULL)
     {
         /* no reply port, so destroy the reply */
         if (reply->Head.msgh_bits & MACH_MSGH_BITS_COMPLEX)
             mach_msg_destroy(&reply->Head);
         CFAllocatorDeallocate(NULL, reply);
         goto done;
     }

     /*
      * send reply.
      *
      * We don't want to block indefinitely because the client
      * isn't receiving messages from the reply port.
      * If we have a send-once right for the reply port, then
      * this isn't a concern because the send won't block.
      * If we have a send right, we need to use MACH_SEND_TIMEOUT.
      * To avoid falling off the kernel's fast RPC path unnecessarily,
      * we only supply MACH_SEND_TIMEOUT when absolutely necessary.
      */

     options = MACH_SEND_MSG;
     if (MACH_MSGH_BITS_REMOTE(reply->Head.msgh_bits) == MACH_MSG_TYPE_MOVE_SEND_ONCE)
         options |= MACH_SEND_TIMEOUT;

     mr = mach_msg(&reply->Head,     /* msg */
                   options,      /* option */
                   reply->Head.msgh_size, /* send_size */
                   0,        /* rcv_size */
                   MACH_PORT_NULL,   /* rcv_name */
                   MACH_MSG_TIMEOUT_NONE, /* timeout */
                   MACH_PORT_NULL);  /* notify */

     /* Has a message error occurred? */
     switch (mr)
     {
     case MACH_SEND_INVALID_DEST:
     case MACH_SEND_TIMED_OUT:
         /* the reply can't be delivered, so destroy it */
         mach_msg_destroy(&reply->Head);
         break;

     default:
         /* Includes success case. */
         break;
     }

     CFAllocatorDeallocate(NULL, reply);

 done:
     KQueueUnlock(&mDNSStorage, "Mach client event");
 }

 mDNSlocal kern_return_t registerBootstrapService()
 {
     kern_return_t status;
     mach_port_t service_rcv_port;

     LogMsg("Registering Bootstrap Service");

     /*
      * See if our service name is already registered and if we have privilege to check in.
      */
     status = bootstrap_check_in(bootstrap_port, (char*)kmDNSBootstrapName, &service_rcv_port);
     if (status == KERN_SUCCESS)
     {
         /*
          * If so, we must be a followup instance of an already defined server.  In that case,
          * the bootstrap port we inherited from our parent is the server's privilege port, so set
          * that in case we have to unregister later (which requires the privilege port).
          */
         server_priv_port = bootstrap_port;
         restarting_via_mach_init = TRUE;
     }
     else
     {
         LogMsg("registerBootstrapService: ERROR!! Registering Bootstrap Service failed %d", status);
         return status;
     }

     /*
      * We have no intention of responding to requests on the service port.  We are not otherwise
      * a Mach port-based service.  We are just using this mechanism for relaunch facilities.
      * So, we can dispose of all the rights we have for the service port.  We don't destroy the
      * send right for the server's privileged bootstrap port - in case we have to unregister later.
      */
     mach_port_destroy(mach_task_self(), service_rcv_port);
     return status;
 }

 mDNSlocal kern_return_t destroyBootstrapService()
 {
     debugf("Destroying Bootstrap Service");
     return bootstrap_register(server_priv_port, (char*)kmDNSBootstrapName, MACH_PORT_NULL);
 }

 mDNSlocal void ExitCallback(int sig)
 {
     (void)sig; // Unused
     LogMsg("%s stopping", mDNSResponderVersionString);

     debugf("ExitCallback");
     if (!mDNS_DebugMode && !started_via_launchdaemon)
         destroyBootstrapService();

     debugf("ExitCallback: Aborting MIG clients");
     while (DNSServiceDomainEnumerationList)
         AbortClient(DNSServiceDomainEnumerationList->ClientMachPort, DNSServiceDomainEnumerationList);
     while (DNSServiceBrowserList)
         AbortClient(DNSServiceBrowserList->ClientMachPort, DNSServiceBrowserList);
     while (DNSServiceResolverList)
         AbortClient(DNSServiceResolverList->ClientMachPort, DNSServiceResolverList);
     while (DNSServiceRegistrationList)
         AbortClient(DNSServiceRegistrationList->ClientMachPort, DNSServiceRegistrationList);

     if (udsserver_exit() < 0) LogMsg("ExitCallback: udsserver_exit failed");

     debugf("ExitCallback: mDNS_StartExit");
     mDNS_StartExit(&mDNSStorage);
 }

 #ifndef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 // Send a mach_msg to ourselves (since that is signal safe) telling us to cleanup and exit
 mDNSlocal void HandleSIG(int sig)
 {
     kern_return_t status;
     mach_msg_header_t header;

     // WARNING: can't call syslog or fprintf from signal handler
     header.msgh_bits = MACH_MSGH_BITS(MACH_MSG_TYPE_MAKE_SEND, 0);
     header.msgh_remote_port = signal_port;
     header.msgh_local_port = MACH_PORT_NULL;
     header.msgh_size = sizeof(header);
     header.msgh_id = sig;

     status = mach_msg(&header, MACH_SEND_MSG | MACH_SEND_TIMEOUT, header.msgh_size,
                       0, MACH_PORT_NULL, 0, MACH_PORT_NULL);

     if (status != MACH_MSG_SUCCESS)
     {
         if (status == MACH_SEND_TIMED_OUT) mach_msg_destroy(&header);
         if (sig == SIGTERM || sig == SIGINT) exit(-1);
     }
 }

 #endif // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 mDNSlocal void INFOCallback(void)
 {
     mDNSs32 utc = mDNSPlatformUTC();
     DNSServiceDomainEnumeration *e;
     DNSServiceBrowser           *b;
     DNSServiceResolver          *l;
     DNSServiceRegistration      *r;
     NetworkInterfaceInfoOSX     *i;
     DNSServer *s;
     McastResolver *mr;

     LogMsg("---- BEGIN STATE LOG ---- %s %s %d", mDNSResponderVersionString, OSXVers ? "OSXVers" : "iOSVers", OSXVers ? OSXVers : iOSVers);

     udsserver_info(&mDNSStorage);

     LogMsgNoIdent("--------- Mach Clients ---------");
     if (!DNSServiceDomainEnumerationList && !DNSServiceBrowserList && !DNSServiceResolverList && !DNSServiceRegistrationList)
         LogMsgNoIdent("<None>");
     else
     {
         for (e = DNSServiceDomainEnumerationList; e; e=e->next)
             LogMsgNoIdent("%5d: Mach DomainEnumeration   %##s", e->ClientMachPort, e->dom.qname.c);

         for (b = DNSServiceBrowserList; b; b=b->next)
         {
             DNSServiceBrowserQuestion *qptr;
             for (qptr = b->qlist; qptr; qptr = qptr->next)
                 LogMsgNoIdent("%5d: Mach ServiceBrowse       %##s", b->ClientMachPort, qptr->q.qname.c);
         }

         for (l = DNSServiceResolverList; l; l=l->next)
             LogMsgNoIdent("%5d: Mach ServiceResolve      %##s", l->ClientMachPort, l->i.name.c);

         for (r = DNSServiceRegistrationList; r; r=r->next)
         {
             ServiceInstance *si;
             for (si = r->regs; si; si = si->next)
                 LogMsgNoIdent("%5d: Mach ServiceInstance     %##s %u", si->ClientMachPort, si->srs.RR_SRV.resrec.name->c, mDNSVal16(si->srs.RR_SRV.resrec.rdata->u.srv.port));
         }
     }

     LogMsgNoIdent("----- KQSocketEventSources -----");
     if (!gEventSources) LogMsgNoIdent("<None>");
     else
     {
         KQSocketEventSource *k;
         for (k = gEventSources; k; k=k->next)
         {
             LogMsgNoIdent("%3d %s", k->fd, k->kqs.KQtask);
             usleep((mDNSStorage.KnownBugs & mDNS_KnownBug_LossySyslog) ? 3333 : 1000);
         }
     }

     LogMsgNoIdent("------ Network Interfaces ------");
     if (!mDNSStorage.p->InterfaceList) LogMsgNoIdent("<None>");
     else
     {
         for (i = mDNSStorage.p->InterfaceList; i; i = i->next)
         {
             // Allow six characters for interface name, for names like "vmnet8"
             if (!i->Exists)
                 LogMsgNoIdent("%p %2ld, Registered %p,  %s %-6s(%lu) %.6a %.6a %#-14a dormant for %d seconds",
                               i, i->ifinfo.InterfaceID, i->Registered,
                               i->sa_family == AF_INET ? "v4" : i->sa_family == AF_INET6 ? "v6" : "??", i->ifinfo.ifname, i->scope_id, &i->ifinfo.MAC, &i->BSSID,
                               &i->ifinfo.ip, utc - i->LastSeen);
             else
             {
                 const CacheRecord *sps[3];
                 FindSPSInCache(&mDNSStorage, &i->ifinfo.NetWakeBrowse, sps);
                 LogMsgNoIdent("%p %2ld, Registered %p,  %s %-6s(%lu) %.6a %.6a %s %s %-15.4a %s %s %s %s %#a",
                               i, i->ifinfo.InterfaceID, i->Registered,
                               i->sa_family == AF_INET ? "v4" : i->sa_family == AF_INET6 ? "v6" : "??", i->ifinfo.ifname, i->scope_id, &i->ifinfo.MAC, &i->BSSID,
                               i->ifinfo.InterfaceActive ? "Active" : "      ",
                               i->ifinfo.IPv4Available ? "v4" : "  ",
                               i->ifinfo.IPv4Available ? (mDNSv4Addr*)&i->ifa_v4addr : &zerov4Addr,
                               i->ifinfo.IPv6Available ? "v6" : "  ",
                               i->ifinfo.Advertise ? "⊙" : " ",
                               i->ifinfo.McastTxRx ? "⇆" : " ",
                               !(i->ifinfo.InterfaceActive && i->ifinfo.NetWake) ? " " : !sps[0] ? "☼" : "☀",
                               &i->ifinfo.ip);

                 if (sps[0]) LogMsgNoIdent("  %13d %#s", SPSMetric(sps[0]->resrec.rdata->u.name.c), sps[0]->resrec.rdata->u.name.c);
                 if (sps[1]) LogMsgNoIdent("  %13d %#s", SPSMetric(sps[1]->resrec.rdata->u.name.c), sps[1]->resrec.rdata->u.name.c);
                 if (sps[2]) LogMsgNoIdent("  %13d %#s", SPSMetric(sps[2]->resrec.rdata->u.name.c), sps[2]->resrec.rdata->u.name.c);
             }
         }
     }

     LogMsgNoIdent("--------- DNS Servers ----------");
     if (!mDNSStorage.DNSServers) LogMsgNoIdent("<None>");
     else
     {
         for (s = mDNSStorage.DNSServers; s; s = s->next)
         {
             NetworkInterfaceInfoOSX *ifx = IfindexToInterfaceInfoOSX(&mDNSStorage, s->interface);
             LogMsgNoIdent("DNS Server %##s %s%s%#a:%d %d %s %d %d %s",
                           s->domain.c, ifx ? ifx->ifinfo.ifname : "", ifx ? " " : "", &s->addr, mDNSVal16(s->port),
                           s->penaltyTime ? s->penaltyTime - mDNS_TimeNow(&mDNSStorage) : 0, s->scoped ? "Scoped" : "",
                           s->timeout, s->resGroupID,
                           s->teststate == DNSServer_Untested ? "(Untested)" :
                           s->teststate == DNSServer_Passed   ? ""           :
                           s->teststate == DNSServer_Failed   ? "(Failed)"   :
                           s->teststate == DNSServer_Disabled ? "(Disabled)" : "(Unknown state)");
         }
     }

     LogMsgNoIdent("--------- Mcast Resolvers ----------");
     if (!mDNSStorage.McastResolvers) LogMsgNoIdent("<None>");
     else
     {
         for (mr = mDNSStorage.McastResolvers; mr; mr = mr->next)
             LogMsgNoIdent("Mcast Resolver %##s timeout %u", mr->domain.c, mr->timeout);
     }

     mDNSs32 now = mDNS_TimeNow(&mDNSStorage);
     LogMsgNoIdent("Timenow 0x%08lX (%d)", (mDNSu32)now, now);

     LogMsg("----  END STATE LOG  ---- %s %s %d", mDNSResponderVersionString, OSXVers ? "OSXVers" : "iOSVers", OSXVers ? OSXVers : iOSVers);
 }

 #ifndef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 mDNSlocal void SignalCallback(CFMachPortRef port, void *msg, CFIndex size, void *info)
 {
     (void)port;     // Unused
     (void)size;     // Unused
     (void)info;     // Unused
     mach_msg_header_t *msg_header = (mach_msg_header_t *)msg;
     mDNS *const m = &mDNSStorage;

     // We're running on the CFRunLoop (Mach port) thread, not the kqueue thread, so we need to grab the KQueueLock before proceeding
     KQueueLock(m);
     switch(msg_header->msgh_id)
     {
     case SIGHUP:    {
         mDNSu32 slot;
         CacheGroup *cg;
         CacheRecord *rr;
         LogMsg("SIGHUP: Purge cache");
         mDNS_Lock(m);
         FORALL_CACHERECORDS(slot, cg, rr)
         {
             mDNS_PurgeCacheResourceRecord(m, rr);
         }
         // Restart unicast and multicast queries
         mDNSCoreRestartQueries(m);
         mDNS_Unlock(m);
     } break;
     case SIGINT:
     case SIGTERM:   ExitCallback(msg_header->msgh_id); break;
     case SIGINFO:   INFOCallback(); break;
     case SIGUSR1:   mDNS_LoggingEnabled = mDNS_LoggingEnabled ? 0 : 1;
         LogMsg("SIGUSR1: Logging %s", mDNS_LoggingEnabled ? "Enabled" : "Disabled");
         WatchDogReportingThreshold = mDNS_LoggingEnabled ? 50 : 250;
         break;
     case SIGUSR2:   mDNS_PacketLoggingEnabled = mDNS_PacketLoggingEnabled ? 0 : 1;
         LogMsg("SIGUSR2: Packet Logging %s", mDNS_PacketLoggingEnabled ? "Enabled" : "Disabled");
         break;
     case SIGIO:
         m->mDNSHandlePeerEvents = m->mDNSHandlePeerEvents ? mDNSfalse : mDNStrue;
         LogMsg("SIGIO: Handle AWDL Peer Events %s", m->mDNSHandlePeerEvents ? "Enabled" : "Disabled");
         break;

     default: LogMsg("SignalCallback: Unknown signal %d", msg_header->msgh_id); break;
     }
     KQueueUnlock(m, "Unix Signal");
 }

 // On 10.2 the MachServerName is DNSServiceDiscoveryServer
 // On 10.3 and later, the MachServerName is com.apple.mDNSResponder
 mDNSlocal kern_return_t mDNSDaemonInitialize(void)
 {
     mStatus err;
     CFMachPortRef s_port;
     CFRunLoopSourceRef s_rls;
     CFRunLoopSourceRef d_rls;

     // If launchd already created our Mach port for us, then use that, else we create a new one of our own
     if (m_port != MACH_PORT_NULL)
         s_port = CFMachPortCreateWithPort(NULL, m_port, DNSserverCallback, NULL, NULL);
     else
     {
         s_port = CFMachPortCreate(NULL, DNSserverCallback, NULL, NULL);
         m_port = CFMachPortGetPort(s_port);
         kern_return_t status = bootstrap_register(bootstrap_port, "com.apple.mDNSResponder", m_port);

         if (status)
         {
             if (status == 1103)
                 LogMsg("bootstrap_register() failed: A copy of the daemon is apparently already running");
             else
                 LogMsg("bootstrap_register() failed: %d %X %s", status, status, mach_error_string(status));
             return(status);
         }
     }

     CFMachPortRef d_port = CFMachPortCreate(NULL, ClientDeathCallback, NULL, NULL);

     err = mDNS_Init(&mDNSStorage, &PlatformStorage,
                     rrcachestorage, RR_CACHE_SIZE,
                     advertise,
                     mDNS_StatusCallback, mDNS_Init_NoInitCallbackContext);

     if (err) { LogMsg("Daemon start: mDNS_Init failed %d", err); return(err); }

     client_death_port = CFMachPortGetPort(d_port);

     s_rls  = CFMachPortCreateRunLoopSource(NULL, s_port, 0);
     CFRunLoopAddSource(PlatformStorage.CFRunLoop, s_rls, kCFRunLoopDefaultMode);
     CFRelease(s_rls);

     d_rls  = CFMachPortCreateRunLoopSource(NULL, d_port, 0);
     CFRunLoopAddSource(PlatformStorage.CFRunLoop, d_rls, kCFRunLoopDefaultMode);
     CFRelease(d_rls);

     CFMachPortRef i_port = CFMachPortCreate(NULL, SignalCallback, NULL, NULL);
     CFRunLoopSourceRef i_rls  = CFMachPortCreateRunLoopSource(NULL, i_port, 0);
     signal_port       = CFMachPortGetPort(i_port);
     CFRunLoopAddSource(PlatformStorage.CFRunLoop, i_rls, kCFRunLoopDefaultMode);
     CFRelease(i_rls);

     if (mDNS_DebugMode) printf("Service registered with Mach Port %d\n", m_port);
     return(err);
 }

 #else // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 // SignalDispatch is mostly just a copy/paste of entire code block from SignalCallback above.
 // The common code should be a subroutine, or we end up having to fix bugs in two places all the time.
 // The same applies to mDNSDaemonInitialize, much of which is just a copy/paste of chunks
 // of code from above. Alternatively we could remove the duplicated source code by having
 // single routines, with the few differing parts bracketed with "#ifndef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM"

 mDNSlocal void SignalDispatch(dispatch_source_t source)
 {
     int sig = (int)dispatch_source_get_handle(source);
     mDNS *const m = &mDNSStorage;
     KQueueLock(m);
     switch(sig)
     {
     case SIGHUP:    {
         mDNSu32 slot;
         CacheGroup *cg;
         CacheRecord *rr;
         LogMsg("SIGHUP: Purge cache");
         mDNS_Lock(m);
         FORALL_CACHERECORDS(slot, cg, rr)
         {
             mDNS_PurgeCacheResourceRecord(m, rr);
         }
         // Restart unicast and multicast queries
         mDNSCoreRestartQueries(m);
         mDNS_Unlock(m);
     } break;
     case SIGINT:
     case SIGTERM:   ExitCallback(sig); break;
     case SIGINFO:   INFOCallback(); break;
     case SIGUSR1:   mDNS_LoggingEnabled = mDNS_LoggingEnabled ? 0 : 1;
         LogMsg("SIGUSR1: Logging %s", mDNS_LoggingEnabled ? "Enabled" : "Disabled");
         WatchDogReportingThreshold = mDNS_LoggingEnabled ? 50 : 250;
         break;
     case SIGUSR2:   mDNS_PacketLoggingEnabled = mDNS_PacketLoggingEnabled ? 0 : 1;
         LogMsg("SIGUSR2: Packet Logging %s", mDNS_PacketLoggingEnabled ? "Enabled" : "Disabled");
         break;
     default: LogMsg("SignalCallback: Unknown signal %d", sig); break;
     }
     KQueueUnlock(m, "Unix Signal");
 }

 mDNSlocal void mDNSSetupSignal(dispatch_queue_t queue, int sig)
 {
     signal(sig, SIG_IGN);
     dispatch_source_t source = dispatch_source_create(DISPATCH_SOURCE_TYPE_SIGNAL, sig, 0, queue);

     if (source)
     {
         dispatch_source_set_event_handler(source, ^{SignalDispatch(source);});
         // Start processing signals
         dispatch_resume(source);
     }
     else
     {
         LogMsg("mDNSSetupSignal: Cannot setup signal %d", sig);
     }
 }

 // On 10.2 the MachServerName is DNSServiceDiscoveryServer
 // On 10.3 and later, the MachServerName is com.apple.mDNSResponder
 mDNSlocal kern_return_t mDNSDaemonInitialize(void)
 {
     mStatus err;
     CFMachPortRef s_port;
     dispatch_source_t mach_source;
     dispatch_queue_t queue = dispatch_get_main_queue();

     // If launchd already created our Mach port for us, then use that, else we create a new one of our own
     if (m_port != MACH_PORT_NULL)
         s_port = CFMachPortCreateWithPort(NULL, m_port, DNSserverCallback, NULL, NULL);
     else
     {
         s_port = CFMachPortCreate(NULL, DNSserverCallback, NULL, NULL);
         m_port = CFMachPortGetPort(s_port);
         kern_return_t status = bootstrap_register(bootstrap_port, "com.apple.mDNSResponder", m_port);

         if (status)
         {
             if (status == 1103)
                 LogMsg("bootstrap_register() failed: A copy of the daemon is apparently already running");
             else
                 LogMsg("bootstrap_register() failed: %d %X %s", status, status, mach_error_string(status));
             return(status);
         }
     }

     err = mDNS_Init(&mDNSStorage, &PlatformStorage,
                     rrcachestorage, RR_CACHE_SIZE,
                     advertise,
                     mDNS_StatusCallback, mDNS_Init_NoInitCallbackContext);

     if (err) { LogMsg("Daemon start: mDNS_Init failed %d", err); return(err); }

     mach_source = dispatch_source_create(DISPATCH_SOURCE_TYPE_MACH_RECV, m_port, 0, queue);
     if (mach_source == mDNSNULL) {LogMsg("mDNSDaemonInitialize: Error creating source for m_port"); return -1;}
     dispatch_source_set_event_handler(mach_source, ^{
                                           dispatch_mig_server(mach_source, sizeof(union __RequestUnion__DNSServiceDiscoveryReply_subsystem),
                                                               DNSServiceDiscoveryRequest_server);
                                       });
     dispatch_resume(mach_source);

     mDNSSetupSignal(queue, SIGHUP);
     mDNSSetupSignal(queue, SIGINT);
     mDNSSetupSignal(queue, SIGTERM);
     mDNSSetupSignal(queue, SIGINFO);
     mDNSSetupSignal(queue, SIGUSR1);
     mDNSSetupSignal(queue, SIGUSR2);
     mDNSSetupSignal(queue, SIGIO);

     // Create a custom handler for doing the housekeeping work. This is either triggered
     // by the timer or an event source
     PlatformStorage.custom = dispatch_source_create(DISPATCH_SOURCE_TYPE_DATA_ADD, 0, 0, queue);
     if (PlatformStorage.custom == mDNSNULL) {LogMsg("mDNSDaemonInitialize: Error creating custom source"); return -1;}
     dispatch_source_set_event_handler(PlatformStorage.custom, ^{PrepareForIdle(&mDNSStorage);});
     dispatch_resume(PlatformStorage.custom);

     // Create a timer source to trigger housekeeping work. The houskeeping work itself
     // is done in the custom handler that we set below.

     PlatformStorage.timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
     if (PlatformStorage.timer == mDNSNULL) {LogMsg("mDNSDaemonInitialize: Error creating timer source"); return -1;}

     // As the API does not support one shot timers, we pass zero for the interval. In the custom handler, we
     // always reset the time to the new time computed. In effect, we ignore the interval
     dispatch_source_set_timer(PlatformStorage.timer, DISPATCH_TIME_NOW, 1000ull * 1000000000, 0);
     dispatch_source_set_event_handler(PlatformStorage.timer, ^{
                                           dispatch_source_merge_data(PlatformStorage.custom, 1);
                                       });
     dispatch_resume(PlatformStorage.timer);

     LogMsg("DaemonIntialize done successfully");

     if (mDNS_DebugMode) printf("Service registered with Mach Port %d\n", m_port);
     return(err);
 }

 #endif // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 mDNSlocal mDNSs32 mDNSDaemonIdle(mDNS *const m)
 {
     mDNSs32 now = mDNS_TimeNow(m);

     // 1. If we need to set domain secrets, do so before handling the network change
     // Detailed reason:
     // BTMM domains listed in DynStore Setup:/Network/BackToMyMac are added to the registration domains list,
     // and we need to setup the associated AutoTunnel DomainAuthInfo entries before that happens.
     if (m->p->KeyChainTimer && now - m->p->KeyChainTimer >= 0)
     {
         m->p->KeyChainTimer = 0;
         mDNS_Lock(m);
         SetDomainSecrets(m);
         mDNS_Unlock(m);
     }

     // 2. If we have network change events to handle, do them before calling mDNS_Execute()
     // Detailed reason:
     // mDNSMacOSXNetworkChanged() currently closes and re-opens its sockets. If there are received packets waiting, they are lost.
     // mDNS_Execute() generates packets, including multicasts that are looped back to ourself.
     // If we call mDNS_Execute() first, and generate packets, and then call mDNSMacOSXNetworkChanged() immediately afterwards
     // we then systematically lose our own looped-back packets.
     if (m->p->NetworkChanged && now - m->p->NetworkChanged >= 0) mDNSMacOSXNetworkChanged(m);

     if (m->p->RequestReSleep && now - m->p->RequestReSleep >= 0) { m->p->RequestReSleep = 0; mDNSPowerRequest(0, 0); }

     // 3. Call mDNS_Execute() to let mDNSCore do what it needs to do
     mDNSs32 nextevent = mDNS_Execute(m);

     if (m->p->NetworkChanged)
         if (nextevent - m->p->NetworkChanged > 0)
             nextevent = m->p->NetworkChanged;

     if (m->p->KeyChainTimer)
         if (nextevent - m->p->KeyChainTimer > 0)
             nextevent = m->p->KeyChainTimer;

     if (m->p->RequestReSleep)
         if (nextevent - m->p->RequestReSleep > 0)
             nextevent = m->p->RequestReSleep;

     // 4. Deliver any waiting browse messages to clients
     DNSServiceBrowser *b = DNSServiceBrowserList;

     while (b)
     {
         // Note: Need to advance b to the next element BEFORE we call DeliverInstance(), because in the
         // event that the client Mach queue overflows, DeliverInstance() will call AbortBlockedClient()
         // and that will cause the DNSServiceBrowser object's memory to be freed before it returns
         DNSServiceBrowser *x = b;
         b = b->next;
         if (x->results)         // Try to deliver the list of results
         {
             while (x->results)
             {
                 DNSServiceBrowserResult *const r = x->results;
                 domainlabel name;
                 domainname type, domain;
                 DeconstructServiceName(&r->result, &name, &type, &domain);  // Don't need to check result; already validated in FoundInstance()
                 char cname[MAX_DOMAIN_LABEL+1];         // Unescaped name: up to 63 bytes plus C-string terminating NULL.
                 char ctype[MAX_ESCAPED_DOMAIN_NAME];
                 char cdom [MAX_ESCAPED_DOMAIN_NAME];
                 ConvertDomainLabelToCString_unescaped(&name, cname);
                 ConvertDomainNameToCString(&type, ctype);
                 ConvertDomainNameToCString(&domain, cdom);
                 DNSServiceDiscoveryReplyFlags flags = (r->next) ? DNSServiceDiscoverReplyFlagsMoreComing : 0;
                 kern_return_t status = DNSServiceBrowserReply_rpc(x->ClientMachPort, r->resultType, cname, ctype, cdom, flags, 1);
                 // If we failed to send the mach message, try again in one second
                 if (status == MACH_SEND_TIMED_OUT)
                 {
                     if (nextevent - now > mDNSPlatformOneSecond)
                         nextevent = now + mDNSPlatformOneSecond;
                     break;
                 }
                 else
                 {
                     x->lastsuccess = now;
                     x->results = x->results->next;
                     freeL("DNSServiceBrowserResult", r);
                 }
             }
             // If this client hasn't read a single message in the last 60 seconds, abort it
             if (now - x->lastsuccess >= 60 * mDNSPlatformOneSecond)
                 AbortBlockedClient(x->ClientMachPort, "browse", x);
         }
     }

     DNSServiceResolver *l;
     for (l = DNSServiceResolverList; l; l=l->next)
         if (l->ReportTime && now - l->ReportTime >= 0)
         {
             l->ReportTime = 0;
             LogMsgNoIdent("Client application bug: DNSServiceResolver(%##s) active for over two minutes. "
                           "This places considerable burden on the network.", l->i.name.c);
         }

     if (m->p->NotifyUser)
     {
         if (m->p->NotifyUser - now < 0)
         {
             if (!SameDomainLabelCS(m->p->usernicelabel.c, m->nicelabel.c))
             {
                 LogMsg("Name Conflict: Updated Computer Name from \"%#s\" to \"%#s\"", m->p->usernicelabel.c, m->nicelabel.c);
                 mDNSPreferencesSetNames(m, kmDNSComputerName, &m->p->usernicelabel, &m->nicelabel);
                 m->p->usernicelabel = m->nicelabel;
             }
             if (!SameDomainLabelCS(m->p->userhostlabel.c, m->hostlabel.c))
             {
                 LogMsg("Name Conflict: Updated Local Hostname from \"%#s.local\" to \"%#s.local\"", m->p->userhostlabel.c, m->hostlabel.c);
                 mDNSPreferencesSetNames(m, kmDNSLocalHostName, &m->p->userhostlabel, &m->hostlabel);
                 m->p->HostNameConflict = 0; // Clear our indicator, now name change has been successful
                 m->p->userhostlabel = m->hostlabel;
             }
             m->p->NotifyUser = 0;
         }
         else
         if (nextevent - m->p->NotifyUser > 0)
             nextevent = m->p->NotifyUser;
     }

     return(nextevent);
 }

 // Right now we consider *ALL* of our DHCP leases
 // It might make sense to be a bit more selective and only consider the leases on interfaces
 // (a) that are capable and enabled for wake-on-LAN, and
 // (b) where we have found (and successfully registered with) a Sleep Proxy
 // If we can't be woken for traffic on a given interface, then why keep waking to renew its lease?
 mDNSlocal mDNSu32 DHCPWakeTime(void)
 {
     mDNSu32 e = 24 * 3600;      // Maximum maintenance wake interval is 24 hours
     const CFAbsoluteTime now = CFAbsoluteTimeGetCurrent();
     if (!now) LogMsg("DHCPWakeTime: CFAbsoluteTimeGetCurrent failed");
     else
     {
         int ic, j;

         const void *pattern = SCDynamicStoreKeyCreateNetworkServiceEntity(NULL, kSCDynamicStoreDomainState, kSCCompAnyRegex, kSCEntNetDHCP);
         if (!pattern)
         {
             LogMsg("DHCPWakeTime: SCDynamicStoreKeyCreateNetworkServiceEntity failed\n");
             return e;
         }
         CFArrayRef dhcpinfo = CFArrayCreate(NULL, (const void **)&pattern, 1, &kCFTypeArrayCallBacks);
         CFRelease(pattern);
         if (dhcpinfo)
         {
             SCDynamicStoreRef store = SCDynamicStoreCreate(NULL, CFSTR("DHCP-LEASES"), NULL, NULL);
             if (store)
             {
                 CFDictionaryRef dict = SCDynamicStoreCopyMultiple(store, NULL, dhcpinfo);
                 if (dict)
                 {
                     ic = CFDictionaryGetCount(dict);
                     const void *vals[ic];
                     CFDictionaryGetKeysAndValues(dict, NULL, vals);

                     for (j = 0; j < ic; j++)
                     {
                         const CFDictionaryRef dhcp = (CFDictionaryRef)vals[j];
                         if (dhcp)
                         {
                             const CFDateRef start = DHCPInfoGetLeaseStartTime(dhcp);
                             const CFDataRef lease = DHCPInfoGetOptionData(dhcp, 51);    // Option 51 = IP Address Lease Time
                             if (!start || !lease || CFDataGetLength(lease) < 4)
                                 LogMsg("DHCPWakeTime: SCDynamicStoreCopyDHCPInfo index %d failed "
                                        "CFDateRef start %p CFDataRef lease %p CFDataGetLength(lease) %d",
                                        j, start, lease, lease ? CFDataGetLength(lease) : 0);
                             else
                             {
                                 const UInt8 *d = CFDataGetBytePtr(lease);
                                 if (!d) LogMsg("DHCPWakeTime: CFDataGetBytePtr %d failed", j);
                                 else
                                 {
                                     const mDNSu32 elapsed   = now - CFDateGetAbsoluteTime(start);
                                     const mDNSu32 lifetime  = (mDNSs32) ((mDNSs32)d[0] << 24 | (mDNSs32)d[1] << 16 | (mDNSs32)d[2] << 8 | d[3]);
                                     const mDNSu32 remaining = lifetime - elapsed;
                                     const mDNSu32 wake      = remaining > 60 ? remaining - remaining/10 : 54;   // Wake at 90% of the lease time
                                     LogSPS("DHCP Address Lease Elapsed %6u Lifetime %6u Remaining %6u Wake %6u", elapsed, lifetime, remaining, wake);
                                     if (e > wake) e = wake;
                                 }
                             }
                         }
                     }
                     CFRelease(dict);
                 }
                 CFRelease(store);
             }
             CFRelease(dhcpinfo);
         }
     }
     return(e);
 }

 // We deliberately schedule our wakeup for halfway between when we'd *like* it and when we *need* it.
 // For example, if our DHCP lease expires in two hours, we'll typically renew it at the halfway point, after one hour.
 // If we scheduled our wakeup for the one-hour renewal time, that might be just seconds from now, and sleeping
 // for a few seconds and then waking again is silly and annoying.
 // If we scheduled our wakeup for the two-hour expiry time, and we were slow to wake, we might lose our lease.
 // Scheduling our wakeup for halfway in between -- 90 minutes -- avoids short wakeups while still
 // allowing us an adequate safety margin to renew our lease before we lose it.

 mDNSlocal mDNSBool AllowSleepNow(mDNS *const m, mDNSs32 now)
 {
     mDNSBool ready = mDNSCoreReadyForSleep(m, now);
     if (m->SleepState && !ready && now - m->SleepLimit < 0) return(mDNSfalse);

     m->p->WakeAtUTC = 0;
     int result = kIOReturnSuccess;
     CFDictionaryRef opts = NULL;

     // If the sleep request was cancelled, and we're no longer planning to sleep, don't need to
     // do the stuff below, but we *DO* still need to acknowledge the sleep message we received.
     if (!m->SleepState)
         LogMsg("AllowSleepNow: Sleep request was canceled with %d ticks remaining", m->SleepLimit - now);
     else
     {
         if (!m->SystemWakeOnLANEnabled || !mDNSCoreHaveAdvertisedMulticastServices(m))
             LogSPS("AllowSleepNow: Not scheduling wakeup: SystemWakeOnLAN %s enabled; %s advertised services",
                    m->SystemWakeOnLANEnabled                  ? "is" : "not",
                    mDNSCoreHaveAdvertisedMulticastServices(m) ? "have" : "no");
         else
         {
             mDNSs32 dhcp = DHCPWakeTime();
             LogSPS("ComputeWakeTime: DHCP Wake %d", dhcp);
             mDNSs32 interval = mDNSCoreIntervalToNextWake(m, now) / mDNSPlatformOneSecond;
             if (interval > dhcp) interval = dhcp;

             // If we're not ready to sleep (failed to register with Sleep Proxy, maybe because of
             // transient network problem) then schedule a wakeup in one hour to try again. Otherwise,
             // a single SPS failure could result in a remote machine falling permanently asleep, requiring
             // someone to go to the machine in person to wake it up again, which would be unacceptable.
             if (!ready && interval > 3600) interval = 3600;

             //interval = 48; // For testing

 #ifdef kIOPMAcknowledgmentOptionSystemCapabilityRequirements
             if (m->p->IOPMConnection)   // If lightweight-wake capability is available, use that
             {
                 const CFDateRef WakeDate = CFDateCreate(NULL, CFAbsoluteTimeGetCurrent() + interval);
                 if (!WakeDate) LogMsg("ScheduleNextWake: CFDateCreate failed");
                 else
                 {
                     const mDNSs32 reqs         = kIOPMSystemPowerStateCapabilityNetwork;
                     const CFNumberRef Requirements = CFNumberCreate(NULL, kCFNumberSInt32Type, &reqs);
                     if (!Requirements) LogMsg("ScheduleNextWake: CFNumberCreate failed");
                     else
                     {
                         const void *OptionKeys[2] = { CFSTR("WakeDate"), CFSTR("Requirements") };
                         const void *OptionVals[2] = {        WakeDate,          Requirements   };
                         opts = CFDictionaryCreate(NULL, (void*)OptionKeys, (void*)OptionVals, 2, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
                         if (!opts) LogMsg("ScheduleNextWake: CFDictionaryCreate failed");
                         CFRelease(Requirements);
                     }
                     CFRelease(WakeDate);
                 }
                 LogSPS("AllowSleepNow: Will request lightweight wakeup in %d seconds", interval);
             }
             else                        // else schedule the wakeup using the old API instead to
 #endif
             {
                 // If we wake within +/- 30 seconds of our requested time we'll assume the system woke for us,
                 // so we should put it back to sleep. To avoid frustrating the user, we always request at least
                 // 60 seconds sleep, so if they immediately re-wake the system within seconds of it going to sleep,
                 // we then shouldn't hit our 30-second window, and we won't attempt to re-sleep the machine.
                 if (interval < 60) interval = 60;

                 result = mDNSPowerRequest(1, interval);

                 if (result == kIOReturnNotReady)
                 {
                     int r;
                     LogMsg("AllowSleepNow: Requested wakeup in %d seconds unsuccessful; retrying with longer intervals", interval);
                     // IOPMSchedulePowerEvent fails with kIOReturnNotReady (-536870184/0xe00002d8) if the
                     // requested wake time is "too soon", but there's no API to find out what constitutes
                     // "too soon" on any given OS/hardware combination, so if we get kIOReturnNotReady
                     // we just have to iterate with successively longer intervals until it doesn't fail.
                     // We preserve the value of "result" because if our original power request was deemed "too soon"
                     // for the machine to get to sleep and wake back up again, we attempt to cancel the sleep request,
                     // since the implication is that the system won't manage to be awake again at the time we need it.
                     do
                     {
                         interval += (interval < 20) ? 1 : ((interval+3) / 4);
                         r = mDNSPowerRequest(1, interval);
                     }
                     while (r == kIOReturnNotReady);
                     if (r) LogMsg("AllowSleepNow: Requested wakeup in %d seconds unsuccessful: %d %X", interval, r, r);
                     else LogSPS("AllowSleepNow: Requested later wakeup in %d seconds; will also attempt IOCancelPowerChange", interval);
                 }
                 else
                 {
                     if (result) LogMsg("AllowSleepNow: Requested wakeup in %d seconds unsuccessful: %d %X", interval, result, result);
                     else LogSPS("AllowSleepNow: Requested wakeup in %d seconds", interval);
                 }
                 m->p->WakeAtUTC = mDNSPlatformUTC() + interval;
             }
         }

         m->SleepState = SleepState_Sleeping;
         // We used to clear our interface list to empty state here before going to sleep.
         // The applications that try to connect to an external server during maintenance wakes, saw
         // DNS resolution errors as we don't have any interfaces (most queries use SuppressUnusable
         // flag). Thus, we don't remove our interfaces anymore on sleep.
     }

     LogSPS("AllowSleepNow: %s(%lX) %s at %ld (%d ticks remaining)",
 #if !TARGET_OS_EMBEDDED && defined(kIOPMAcknowledgmentOptionSystemCapabilityRequirements)
            (m->p->IOPMConnection) ? "IOPMConnectionAcknowledgeEventWithOptions" :
 #endif
            (result == kIOReturnSuccess) ? "IOAllowPowerChange" : "IOCancelPowerChange",
            m->p->SleepCookie, ready ? "ready for sleep" : "giving up", now, m->SleepLimit - now);

     m->SleepLimit = 0;  // Don't clear m->SleepLimit until after we've logged it above

 #if !TARGET_OS_EMBEDDED && defined(kIOPMAcknowledgmentOptionSystemCapabilityRequirements)
     if (m->p->IOPMConnection) IOPMConnectionAcknowledgeEventWithOptions(m->p->IOPMConnection, m->p->SleepCookie, opts);
     else
 #endif
     if (result == kIOReturnSuccess) IOAllowPowerChange (m->p->PowerConnection, m->p->SleepCookie);
     else IOCancelPowerChange(m->p->PowerConnection, m->p->SleepCookie);

     if (opts) CFRelease(opts);
     return(mDNStrue);
 }

 #ifdef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 mDNSexport void TriggerEventCompletion()
 {
     debugf("TriggerEventCompletion: Merge data");
     dispatch_source_merge_data(PlatformStorage.custom, 1);
 }

 mDNSlocal void PrepareForIdle(void *m_param)
 {
     mDNS            *m = m_param;
     int64_t time_offset;
     dispatch_time_t dtime;

     const int multiplier = 1000000000 / mDNSPlatformOneSecond;

     // This is the main work loop:
     // (1) First we give mDNSCore a chance to finish off any of its deferred work and calculate the next sleep time
     // (2) Then we make sure we've delivered all waiting browse messages to our clients
     // (3) Then we sleep for the time requested by mDNSCore, or until the next event, whichever is sooner

     debugf("PrepareForIdle: called");
     // Run mDNS_Execute to find out the time we next need to wake up
     mDNSs32 start          = mDNSPlatformRawTime();
     mDNSs32 nextTimerEvent = udsserver_idle(mDNSDaemonIdle(m));
     mDNSs32 end            = mDNSPlatformRawTime();
     if (end - start >= WatchDogReportingThreshold)
         LogInfo("CustomSourceHandler:WARNING: Idle task took %dms to complete", end - start);

     mDNSs32 now = mDNS_TimeNow(m);

     if (m->ShutdownTime)
     {
         if (mDNSStorage.ResourceRecords)
         {
             LogInfo("Cannot exit yet; Resource Record still exists: %s", ARDisplayString(m, mDNSStorage.ResourceRecords));
             if (mDNS_LoggingEnabled) usleep(10000);     // Sleep 10ms so that we don't flood syslog with too many messages
         }
         if (mDNS_ExitNow(m, now))
         {
             LogInfo("IdleLoop: mDNS_FinalExit");
             mDNS_FinalExit(&mDNSStorage);
             usleep(1000);       // Little 1ms pause before exiting, so we don't lose our final syslog messages
             exit(0);
         }
         if (nextTimerEvent - m->ShutdownTime >= 0)
             nextTimerEvent = m->ShutdownTime;
     }

     if (m->SleepLimit)
         if (!AllowSleepNow(m, now))
             if (nextTimerEvent - m->SleepLimit >= 0)
                 nextTimerEvent = m->SleepLimit;

     // Convert absolute wakeup time to a relative time from now
     mDNSs32 ticks = nextTimerEvent - now;
     if (ticks < 1) ticks = 1;

     static mDNSs32 RepeatedBusy = 0;    // Debugging sanity check, to guard against CPU spins
     if (ticks > 1)
         RepeatedBusy = 0;
     else
     {
         ticks = 1;
         if (++RepeatedBusy >= mDNSPlatformOneSecond) { ShowTaskSchedulingError(&mDNSStorage); RepeatedBusy = 0; }
     }

     time_offset = ((mDNSu32)ticks / mDNSPlatformOneSecond) * 1000000000 + (ticks % mDNSPlatformOneSecond) * multiplier;
     dtime = dispatch_time(DISPATCH_TIME_NOW, time_offset);
     dispatch_source_set_timer(PlatformStorage.timer, dtime, 1000ull*1000000000, 0);
     debugf("PrepareForIdle: scheduling timer with ticks %d", ticks);
     return;
 }

 #else // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 mDNSlocal void KQWokenFlushBytes(int fd, __unused short filter, __unused void *context)
 {
     // Read all of the bytes so we won't wake again.
     char buffer[100];
     while (recv(fd, buffer, sizeof(buffer), MSG_DONTWAIT) > 0) continue;
 }

 mDNSlocal void * KQueueLoop(void *m_param)
 {
     mDNS            *m = m_param;
     int numevents = 0;

 #if USE_SELECT_WITH_KQUEUEFD
     fd_set readfds;
     FD_ZERO(&readfds);
     const int multiplier = 1000000    / mDNSPlatformOneSecond;
 #else
     const int multiplier = 1000000000 / mDNSPlatformOneSecond;
 #endif

     pthread_mutex_lock(&PlatformStorage.BigMutex);
     LogInfo("Starting time value 0x%08lX (%ld)", (mDNSu32)mDNSStorage.timenow_last, mDNSStorage.timenow_last);

     // This is the main work loop:
     // (1) First we give mDNSCore a chance to finish off any of its deferred work and calculate the next sleep time
     // (2) Then we make sure we've delivered all waiting browse messages to our clients
     // (3) Then we sleep for the time requested by mDNSCore, or until the next event, whichever is sooner
     // (4) On wakeup we first process *all* events
     // (5) then when no more events remain, we go back to (1) to finish off any deferred work and do it all again
     for ( ; ; )
     {
         #define kEventsToReadAtOnce 1
         struct kevent new_events[kEventsToReadAtOnce];

         // Run mDNS_Execute to find out the time we next need to wake up
         mDNSs32 start          = mDNSPlatformRawTime();
         mDNSs32 nextTimerEvent = udsserver_idle(mDNSDaemonIdle(m));
         mDNSs32 end            = mDNSPlatformRawTime();
         if (end - start >= WatchDogReportingThreshold)
             LogInfo("WARNING: Idle task took %dms to complete", end - start);

         mDNSs32 now = mDNS_TimeNow(m);

         if (m->ShutdownTime)
         {
             if (mDNSStorage.ResourceRecords)
             {
                 AuthRecord *rr;
                 for (rr = mDNSStorage.ResourceRecords; rr; rr=rr->next)
                 {
                     LogInfo("Cannot exit yet; Resource Record still exists: %s", ARDisplayString(m, rr));
                     if (mDNS_LoggingEnabled) usleep(10000);     // Sleep 10ms so that we don't flood syslog with too many messages
                 }
             }
             if (mDNS_ExitNow(m, now))
             {
                 LogInfo("mDNS_FinalExit");
                 mDNS_FinalExit(&mDNSStorage);
                 usleep(1000);       // Little 1ms pause before exiting, so we don't lose our final syslog messages
                 exit(0);
             }
             if (nextTimerEvent - m->ShutdownTime >= 0)
                 nextTimerEvent = m->ShutdownTime;
         }

         if (m->SleepLimit)
             if (!AllowSleepNow(m, now))
                 if (nextTimerEvent - m->SleepLimit >= 0)
                     nextTimerEvent = m->SleepLimit;

         // Convert absolute wakeup time to a relative time from now
         mDNSs32 ticks = nextTimerEvent - now;
         if (ticks < 1) ticks = 1;

         static mDNSs32 RepeatedBusy = 0;    // Debugging sanity check, to guard against CPU spins
         if (ticks > 1)
             RepeatedBusy = 0;
         else
         {
             ticks = 1;
             if (++RepeatedBusy >= mDNSPlatformOneSecond) { ShowTaskSchedulingError(&mDNSStorage); RepeatedBusy = 0; }
         }

         verbosedebugf("KQueueLoop: Handled %d events; now sleeping for %d ticks", numevents, ticks);
         numevents = 0;

         // Release the lock, and sleep until:
         // 1. Something interesting happens like a packet arriving, or
         // 2. The other thread writes a byte to WakeKQueueLoopFD to poke us and make us wake up, or
         // 3. The timeout expires
         pthread_mutex_unlock(&PlatformStorage.BigMutex);

 #if USE_SELECT_WITH_KQUEUEFD
         struct timeval timeout;
         timeout.tv_sec = ticks / mDNSPlatformOneSecond;
         timeout.tv_usec = (ticks % mDNSPlatformOneSecond) * multiplier;
         FD_SET(KQueueFD, &readfds);
         if (select(KQueueFD+1, &readfds, NULL, NULL, &timeout) < 0)
         { LogMsg("select(%d) failed errno %d (%s)", KQueueFD, errno, strerror(errno)); sleep(1); }
 #else
         struct timespec timeout;
         timeout.tv_sec = ticks / mDNSPlatformOneSecond;
         timeout.tv_nsec = (ticks % mDNSPlatformOneSecond) * multiplier;
         // In my opinion, you ought to be able to call kevent() with nevents set to zero,
         // and have it work similarly to the way it does with nevents non-zero --
         // i.e. it waits until either an event happens or the timeout expires, and then wakes up.
         // In fact, what happens if you do this is that it just returns immediately. So, we have
         // to pass nevents set to one, and then we just ignore the event it gives back to us. -- SC
         if (kevent(KQueueFD, NULL, 0, new_events, 1, &timeout) < 0)
         { LogMsg("kevent(%d) failed errno %d (%s)", KQueueFD, errno, strerror(errno)); sleep(1); }
 #endif

         pthread_mutex_lock(&PlatformStorage.BigMutex);
         // We have to ignore the event we may have been told about above, because that
         // was done without holding the lock, and between the time we woke up and the
         // time we reclaimed the lock the other thread could have done something that
         // makes the event no longer valid. Now we have the lock, we call kevent again
         // and this time we can safely process the events it tells us about.

         static const struct timespec zero_timeout = { 0, 0 };
         int events_found;
         while ((events_found = kevent(KQueueFD, NULL, 0, new_events, kEventsToReadAtOnce, &zero_timeout)) != 0)
         {
             if (events_found > kEventsToReadAtOnce || (events_found < 0 && errno != EINTR))
             {
                 // Not sure what to do here, our kqueue has failed us - this isn't ideal
                 LogMsg("ERROR: KQueueLoop - kevent failed errno %d (%s)", errno, strerror(errno));
                 exit(errno);
             }

             numevents += events_found;

             int i;
             for (i = 0; i < events_found; i++)
             {
                 const KQueueEntry *const kqentry = new_events[i].udata;
                 mDNSs32 stime = mDNSPlatformRawTime();
                 const char *const KQtask = kqentry->KQtask; // Grab a copy in case KQcallback deletes the task
                 kqentry->KQcallback(new_events[i].ident, new_events[i].filter, kqentry->KQcontext);
                 mDNSs32 etime = mDNSPlatformRawTime();
                 if (etime - stime >= WatchDogReportingThreshold)
                     LogInfo("WARNING: %s took %dms to complete", KQtask, etime - stime);
             }
         }
     }

     return NULL;
 }

 #endif // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

 mDNSlocal void LaunchdCheckin(void)
 {
     launch_data_t msg  = launch_data_new_string(LAUNCH_KEY_CHECKIN);
     launch_data_t resp = launch_msg(msg);
     launch_data_free(msg);
     if (!resp) { LogMsg("launch_msg returned NULL"); return; }

     if (launch_data_get_type(resp) == LAUNCH_DATA_ERRNO)
     {
         int err = launch_data_get_errno(resp);
         // When running on Tiger with "ServiceIPC = false", we get "err == EACCES" to tell us there's no launchdata to fetch
         if (err != EACCES) LogMsg("launch_msg returned %d", err);
         else LogInfo("Launchd provided no launchdata; will open Mach port and Unix Domain Socket explicitly...", err);
     }
     else
     {
         launch_data_t skts = launch_data_dict_lookup(resp, LAUNCH_JOBKEY_SOCKETS);
         if (!skts) LogMsg("launch_data_dict_lookup LAUNCH_JOBKEY_SOCKETS returned NULL");
         else
         {
             launch_data_t skt = launch_data_dict_lookup(skts, "Listeners");
             if (!skt) LogMsg("launch_data_dict_lookup Listeners returned NULL");
             else
             {
                 launchd_fds_count = launch_data_array_get_count(skt);
                 if (launchd_fds_count == 0) LogMsg("launch_data_array_get_count(skt) returned 0");
                 else
                 {
                     launchd_fds = mallocL("LaunchdCheckin", sizeof(dnssd_sock_t) * launchd_fds_count);
                     if (!launchd_fds) LogMsg("LaunchdCheckin: malloc failed");
                     else
                     {
                         size_t i;
                         for(i = 0; i < launchd_fds_count; i++)
                         {
                             launch_data_t s = launch_data_array_get_index(skt, i);
                             if (!s)
                             {
                                 launchd_fds[i] = dnssd_InvalidSocket;
                                 LogMsg("launch_data_array_get_index(skt, %d) returned NULL", i);
                             }
                             else
                             {
                                 launchd_fds[i] = launch_data_get_fd(s);
                                 LogInfo("Launchd Unix Domain Socket [%d]: %d", i, launchd_fds[i]);
                             }
                         }
                     }
                     // In some early versions of 10.4.x, the permissions on the UDS were not set correctly, so we fix them here
                     chmod(MDNS_UDS_SERVERPATH, S_IRUSR|S_IWUSR | S_IRGRP|S_IWGRP | S_IROTH|S_IWOTH);
                 }
             }
         }

         launch_data_t ports = launch_data_dict_lookup(resp, "MachServices");
         if (!ports) LogMsg("launch_data_dict_lookup MachServices returned NULL");
         else
         {
             launch_data_t p = launch_data_dict_lookup(ports, "com.apple.mDNSResponder");
             if (!p) LogInfo("launch_data_dict_lookup(ports, \"com.apple.mDNSResponder\") returned NULL");
             else
             {
                 m_port = launch_data_get_fd(p);
                 LogInfo("Launchd Mach Port: %d", m_port);
                 if (m_port == ~0U) m_port = MACH_PORT_NULL;
             }
         }
     }
     launch_data_free(resp);
 }

 mDNSlocal void DropPrivileges(void)
 {
     static const char login[] = "_mdnsresponder";
     struct passwd *pwd = getpwnam(login);
     if (NULL == pwd)
         LogMsg("Could not find account name \"%s\". Running as root.", login);
     else
     {
         uid_t uid = pwd->pw_uid;
         gid_t gid = pwd->pw_gid;

         LogMsg("Started as root. Switching to userid \"%s\".", login);

         if (unlink(MDNS_UDS_SERVERPATH) < 0 && errno != ENOENT) LogMsg("DropPrivileges: Could not unlink \"%s\": (%d) %s", MDNS_UDS_SERVERPATH, errno, strerror(errno));
         else
         {
             static char path[] = "/var/run/mdns/mDNSResponder";
             char *p = strrchr(path, '/');
             *p = '\0';
             if (mkdir(path, 0755) < 0 && errno != EEXIST) LogMsg("DropPrivileges: Could not create directory \"%s\": (%d) %s", path, errno, strerror(errno));
             else if (chown(path, uid, gid) < 0) LogMsg("DropPrivileges: Could not chown directory \"%s\": (%d) %s", path, errno, strerror(errno));
             else
             {
                 *p = '/';
                 if (unlink(path) < 0 && errno != ENOENT) LogMsg("DropPrivileges: Could not unlink \"%s\": (%d) %s", path, errno, strerror(errno));
                 else if (symlink(path, MDNS_UDS_SERVERPATH) < 0) LogMsg("DropPrivileges: Could not symlink \"%s\" -> \"%s\": (%d) %s", MDNS_UDS_SERVERPATH, path, errno, strerror(errno));
                 else LogInfo("DropPrivileges: Created subdirectory and symlink");
             }
         }

         if (0 != initgroups(login, gid)) LogMsg("initgroups(\"%s\", %lu) failed.  Continuing.", login,        (unsigned long)gid);
         if (0 != setgid(gid)) LogMsg("setgid(%lu) failed.  Continuing with group %lu privileges.", (unsigned long)getegid());
         if (0 != setuid(uid)) LogMsg("setuid(%lu) failed. Continuing as root after all.",          (unsigned long)uid);
     }
 }

 extern int sandbox_init(const char *profile, uint64_t flags, char **errorbuf) __attribute__((weak_import));

 mDNSexport int main(int argc, char **argv)
 {
     int i;
     kern_return_t status;

     mDNSMacOSXSystemBuildNumber(NULL);
     LogMsg("%s starting %s %d", mDNSResponderVersionString, OSXVers ? "OSXVers" : "iOSVers", OSXVers ? OSXVers : iOSVers);

 #if 0
     LogMsg("CacheRecord %d", sizeof(CacheRecord));
     LogMsg("CacheGroup  %d", sizeof(CacheGroup));
     LogMsg("ResourceRecord  %d", sizeof(ResourceRecord));
     LogMsg("RData_small     %d", sizeof(RData_small));

     LogMsg("sizeof(CacheEntity) %d", sizeof(CacheEntity));
     LogMsg("RR_CACHE_SIZE       %d", RR_CACHE_SIZE);
     LogMsg("block usage         %d", sizeof(CacheEntity) * RR_CACHE_SIZE);
     LogMsg("block wastage       %d", 16*1024 - sizeof(CacheEntity) * RR_CACHE_SIZE);
 #endif

     if (0 == geteuid()) DropPrivileges();

     for (i=1; i<argc; i++)
     {
         if (!strcasecmp(argv[i], "-d"                        )) mDNS_DebugMode            = mDNStrue;
         if (!strcasecmp(argv[i], "-launchd"                  )) started_via_launchdaemon  = mDNStrue;
         if (!strcasecmp(argv[i], "-launchdaemon"             )) started_via_launchdaemon  = mDNStrue;
         if (!strcasecmp(argv[i], "-NoMulticastAdvertisements")) advertise                 = mDNS_Init_DontAdvertiseLocalAddresses;
         if (!strcasecmp(argv[i], "-DisableSleepProxyClient"  )) DisableSleepProxyClient   = mDNStrue;
         if (!strcasecmp(argv[i], "-DebugLogging"             )) mDNS_LoggingEnabled       = mDNStrue;
         if (!strcasecmp(argv[i], "-UnicastPacketLogging"     )) mDNS_PacketLoggingEnabled = mDNStrue;
         if (!strcasecmp(argv[i], "-OfferSleepProxyService"   ))
             OfferSleepProxyService = (i+1 < argc && mDNSIsDigit(argv[i+1][0]) && mDNSIsDigit(argv[i+1][1]) && argv[i+1][2]==0) ? atoi(argv[++i]) : 100;
         if (!strcasecmp(argv[i], "-UseInternalSleepProxy"    ))
             UseInternalSleepProxy = (i+1<argc && mDNSIsDigit(argv[i+1][0]) && argv[i+1][1]==0) ? atoi(argv[++i]) : 1;
         if (!strcasecmp(argv[i], "-StrictUnicastOrdering"    )) StrictUnicastOrdering     = mDNStrue;
         if (!strcasecmp(argv[i], "-AlwaysAppendSearchDomains")) AlwaysAppendSearchDomains = mDNStrue;
     }

     // Note that mDNSPlatformInit will set DivertMulticastAdvertisements in the mDNS structure
     if (!advertise) LogMsg("Administratively prohibiting multicast advertisements");

 #ifndef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

     signal(SIGHUP,  HandleSIG);     // (Debugging) Purge the cache to check for cache handling bugs
     signal(SIGINT,  HandleSIG);     // Ctrl-C: Detach from Mach BootstrapService and exit cleanly
     signal(SIGPIPE, SIG_IGN  );     // Don't want SIGPIPE signals -- we'll handle EPIPE errors directly
     signal(SIGTERM, HandleSIG);     // Machine shutting down: Detach from and exit cleanly like Ctrl-C
     signal(SIGINFO, HandleSIG);     // (Debugging) Write state snapshot to syslog
     signal(SIGUSR1, HandleSIG);     // (Debugging) Enable Logging
     signal(SIGUSR2, HandleSIG);     // (Debugging) Enable Packet Logging
     signal(SIGIO, HandleSIG);       // (Debugging) Toggle AWDL Peer Event Handling

 #endif // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

     mDNSStorage.p = &PlatformStorage;   // Make sure mDNSStorage.p is set up, because validatelists uses it
     LaunchdCheckin();

     // Register the server with mach_init for automatic restart only during normal (non-debug) mode
     if (!mDNS_DebugMode && !started_via_launchdaemon)
     {
         registerBootstrapService();
         if (!restarting_via_mach_init) exit(0); // mach_init will restart us immediately as a daemon
         int fd = open(_PATH_DEVNULL, O_RDWR, 0);
         if (fd < 0) LogMsg("open(_PATH_DEVNULL, O_RDWR, 0) failed errno %d (%s)", errno, strerror(errno));
         else
         {
             // Avoid unnecessarily duplicating a file descriptor to itself
             if (fd != STDIN_FILENO) if (dup2(fd, STDIN_FILENO)  < 0) LogMsg("dup2(fd, STDIN_FILENO)  failed errno %d (%s)", errno, strerror(errno));
             if (fd != STDOUT_FILENO) if (dup2(fd, STDOUT_FILENO) < 0) LogMsg("dup2(fd, STDOUT_FILENO) failed errno %d (%s)", errno, strerror(errno));
             if (fd != STDERR_FILENO) if (dup2(fd, STDERR_FILENO) < 0) LogMsg("dup2(fd, STDERR_FILENO) failed errno %d (%s)", errno, strerror(errno));
             if (fd != STDIN_FILENO && fd != STDOUT_FILENO && fd != STDERR_FILENO) (void)close(fd);
         }
     }

 #ifndef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

     // Create the kqueue, mutex and thread to support KQSockets
     KQueueFD = kqueue();
     if (KQueueFD == -1) { LogMsg("kqueue() failed errno %d (%s)", errno, strerror(errno)); status = errno; goto exit; }

     i = pthread_mutex_init(&PlatformStorage.BigMutex, NULL);
     if (i == -1) { LogMsg("pthread_mutex_init() failed errno %d (%s)", errno, strerror(errno)); status = errno; goto exit; }

     int fdpair[2] = {0, 0};
     i = socketpair(AF_UNIX, SOCK_STREAM, 0, fdpair);
     if (i == -1) { LogMsg("socketpair() failed errno %d (%s)", errno, strerror(errno)); status = errno; goto exit; }

     // Socket pair returned us two identical sockets connected to each other
     // We will use the first socket to send the second socket. The second socket
     // will be added to the kqueue so it will wake when data is sent.
     static const KQueueEntry wakeKQEntry = { KQWokenFlushBytes, NULL, "kqueue wakeup after CFRunLoop event" };

     PlatformStorage.WakeKQueueLoopFD = fdpair[0];
     KQueueSet(fdpair[1], EV_ADD, EVFILT_READ, &wakeKQEntry);

 #endif // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

     // Invoke sandbox profile /usr/share/sandbox/mDNSResponder.sb
 #if MDNS_NO_SANDBOX
     LogMsg("Note: Compiled without Apple Sandbox support");
 #else // MDNS_NO_SANDBOX
     if (!sandbox_init)
         LogMsg("Note: Running without Apple Sandbox support (not available on this OS)");
     else
     {
         char *sandbox_msg;
         uint64_t sandbox_flags = SANDBOX_NAMED;

         int sandbox_err = sandbox_init("mDNSResponder", sandbox_flags, &sandbox_msg);
         if (sandbox_err) { LogMsg("WARNING: sandbox_init error %s", sandbox_msg); sandbox_free_error(sandbox_msg); }
         else LogInfo("Now running under Apple Sandbox restrictions");
     }
 #endif // MDNS_NO_SANDBOX

     // We use BeginTransactionAtShutdown in the plist that ensures that we will
     // receive a SIGTERM during shutdown rather than a SIGKILL. But launchd (due to some
     // limitation) currently requires us to still start and end the transaction for
     // its proper initialization.
     vproc_transaction_t vt = vproc_transaction_begin(NULL);
     if (vt) vproc_transaction_end(NULL, vt);

     status = mDNSDaemonInitialize();
     if (status) { LogMsg("Daemon start: mDNSDaemonInitialize failed"); goto exit; }

     status = udsserver_init(launchd_fds, launchd_fds_count);
     if (status) { LogMsg("Daemon start: udsserver_init failed"); goto exit; }

     mDNSMacOSXNetworkChanged(&mDNSStorage);

 #ifdef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM
     LogInfo("Daemon Start: Using LibDispatch");
     // CFRunLoopRun runs both CFRunLoop sources and dispatch sources
     CFRunLoopRun();
 #else // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM
       // Start the kqueue thread
     pthread_t KQueueThread;
     i = pthread_create(&KQueueThread, NULL, KQueueLoop, &mDNSStorage);
     if (i == -1) { LogMsg("pthread_create() failed errno %d (%s)", errno, strerror(errno)); status = errno; goto exit; }
     if (status == 0)
     {
         CFRunLoopRun();
         LogMsg("ERROR: CFRunLoopRun Exiting.");
         mDNS_Close(&mDNSStorage);
     }
 #endif // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

     LogMsg("%s exiting", mDNSResponderVersionString);

 exit:
     if (!mDNS_DebugMode && !started_via_launchdaemon) destroyBootstrapService();
     return(status);
 }

 // uds_daemon.c support routines /////////////////////////////////////////////

 // Arrange things so that when data appears on fd, callback is called with context
 mDNSexport mStatus udsSupportAddFDToEventLoop(int fd, udsEventCallback callback, void *context, void **platform_data)
 {
     KQSocketEventSource **p = &gEventSources;
     (void) platform_data;
     while (*p && (*p)->fd != fd) p = &(*p)->next;
     if (*p) { LogMsg("udsSupportAddFDToEventLoop: ERROR fd %d already has EventLoop source entry", fd); return mStatus_AlreadyRegistered; }

     KQSocketEventSource *newSource = (KQSocketEventSource*) mallocL("KQSocketEventSource", sizeof *newSource);
     if (!newSource) return mStatus_NoMemoryErr;

     newSource->next           = mDNSNULL;
     newSource->fd             = fd;
     newSource->kqs.KQcallback = callback;
     newSource->kqs.KQcontext  = context;
     newSource->kqs.KQtask     = "UDS client";
 #ifdef MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM
     newSource->kqs.readSource  = mDNSNULL;
     newSource->kqs.writeSource = mDNSNULL;
     newSource->kqs.fdClosed    = mDNSfalse;
 #endif // MDNSRESPONDER_USES_LIB_DISPATCH_AS_PRIMARY_EVENT_LOOP_MECHANISM

     if (KQueueSet(fd, EV_ADD, EVFILT_READ, &newSource->kqs) == 0)
     {
         *p = newSource;
         return mStatus_NoError;
     }

     LogMsg("KQueueSet failed for fd %d errno %d (%s)", fd, errno, strerror(errno));
     freeL("KQSocketEventSource", newSource);
     return mStatus_BadParamErr;
 }

 int udsSupportReadFD(dnssd_sock_t fd, char *buf, int len, int flags, void *platform_data)
 {
     (void) platform_data;
     return recv(fd, buf, len, flags);
 }

 mDNSexport mStatus udsSupportRemoveFDFromEventLoop(int fd, void *platform_data)     // Note: This also CLOSES the file descriptor
 {
     KQSocketEventSource **p = &gEventSources;
     (void) platform_data;
     while (*p && (*p)->fd != fd) p = &(*p)->next;
     if (*p)
     {
         KQSocketEventSource *s = *p;
         *p = (*p)->next;
         // We don't have to explicitly do a kqueue EV_DELETE here because closing the fd
         // causes the kernel to automatically remove any associated kevents
         mDNSPlatformCloseFD(&s->kqs, s->fd);
         freeL("KQSocketEventSource", s);
         return mStatus_NoError;
     }
     LogMsg("udsSupportRemoveFDFromEventLoop: ERROR fd %d not found in EventLoop source list", fd);
     return mStatus_NoSuchNameErr;
 }

 #if _BUILDING_XCODE_PROJECT_
 // If mDNSResponder crashes, then this string will be magically included in the automatically-generated crash log
 const char *__crashreporter_info__ = mDNSResponderVersionString;
 asm (".desc ___crashreporter_info__, 0x10");
 #endif

 // For convenience when using the "strings" command, this is the last thing in the file
 // The "@(#) " pattern is a special prefix the "what" command looks for
 mDNSexport const char mDNSResponderVersionString_SCCS[] = "@(#) mDNSResponder " STRINGIFY(mDNSResponderVersion) " (" __DATE__ " " __TIME__ ")";