| /** |
| * @file |
| * Address Resolution Protocol module for IP over Ethernet |
| * |
| * $Log: etharp.c,v $ |
| * Revision 1.19 2003/01/08 10:09:43 likewise |
| * Updated lwIP module copyright years to include 2003. Committers must check theirs. |
| * |
| * Revision 1.18 2003/01/08 09:24:50 likewise |
| * Removed etharp_output_sent() as etharp.c no longer returns ARP packets to the driver. |
| * |
| * Revision 1.17 2002/12/18 12:49:02 jani |
| * renamed (hopefully everywhere) stats to lwip_stats.closes bug #1901 |
| * |
| * Revision 1.16 2002/12/17 09:41:16 jani |
| * Use C style comments.In debug stataments cast various struct pointers to void* to |
| * avoid printf warnings.misc warnings in etharp. |
| * |
| */ |
| |
| /* |
| * Copyright (c) 2001-2003 Swedish Institute of Computer Science. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without modification, |
| * are permitted provided that the following conditions are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright notice, |
| * this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright notice, |
| * this list of conditions and the following disclaimer in the documentation |
| * and/or other materials provided with the distribution. |
| * 3. The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED |
| * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT |
| * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
| * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT |
| * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING |
| * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY |
| * OF SUCH DAMAGE. |
| * |
| * This file is part of the lwIP TCP/IP stack. |
| * |
| * Author: Adam Dunkels <adam@sics.se> |
| * |
| */ |
| |
| /* |
| * TODO: |
| * |
| RFC 3220 4.6 IP Mobility Support for IPv4 January 2002 |
| |
| - A Gratuitous ARP [45] is an ARP packet sent by a node in order |
| to spontaneously cause other nodes to update an entry in their |
| ARP cache. A gratuitous ARP MAY use either an ARP Request or |
| an ARP Reply packet. In either case, the ARP Sender Protocol |
| Address and ARP Target Protocol Address are both set to the IP |
| address of the cache entry to be updated, and the ARP Sender |
| Hardware Address is set to the link-layer address to which this |
| cache entry should be updated. When using an ARP Reply packet, |
| the Target Hardware Address is also set to the link-layer |
| address to which this cache entry should be updated (this field |
| is not used in an ARP Request packet). |
| |
| In either case, for a gratuitous ARP, the ARP packet MUST be |
| transmitted as a local broadcast packet on the local link. As |
| specified in [36], any node receiving any ARP packet (Request |
| or Reply) MUST update its local ARP cache with the Sender |
| Protocol and Hardware Addresses in the ARP packet, if the |
| receiving node has an entry for that IP address already in its |
| ARP cache. This requirement in the ARP protocol applies even |
| for ARP Request packets, and for ARP Reply packets that do not |
| match any ARP Request transmitted by the receiving node [36]. |
| * |
| My suggestion would be to send a ARP request for our newly obtained |
| address upon configuration of an Ethernet interface. |
| |
| */ |
| |
| #include "lwip/opt.h" |
| #include "lwip/debug.h" |
| #include "lwip/inet.h" |
| #include "netif/etharp.h" |
| #include "lwip/ip.h" |
| #include "lwip/stats.h" |
| #include "lwipopts.h" |
| |
| /* ARP needs to inform DHCP of any ARP replies? */ |
| #if (LWIP_DHCP && DHCP_DOES_ARP_CHECK) |
| # include "lwip/dhcp.h" |
| #endif |
| |
| /** the time an ARP entry stays valid after its last update, (120 * 10) seconds = 20 minutes. */ |
| #define ARP_MAXAGE 120 |
| /** the time an ARP entry stays pending after first request, (2 * 10) seconds = 20 seconds. */ |
| #define ARP_MAXPENDING 2 |
| |
| /** |
| * |
| * - If enabled, cache entries are generated for every kind of ARP/IP traffic. |
| * This enhances behaviour for sending to a dynamic set of hosts, for example |
| * if acting as a gateway. |
| * - If disabled, cache entries are generated only for IP destination addresses |
| * in use by lwIP or applications. This enhances performance if sending to a small, |
| * reasonably static number of hosts. Typically for embedded devices. |
| */ |
| #ifndef ETHARP_ALWAYS_INSERT |
| # define ETHARP_ALWAYS_INSERT 1 |
| #endif |
| |
| #define HWTYPE_ETHERNET 1 |
| |
| /** ARP message types */ |
| #define ARP_REQUEST 1 |
| #define ARP_REPLY 2 |
| |
| #define ARPH_HWLEN(hdr) (NTOHS((hdr)->_hwlen_protolen) >> 8) |
| #define ARPH_PROTOLEN(hdr) (NTOHS((hdr)->_hwlen_protolen) & 0xff) |
| |
| #define ARPH_HWLEN_SET(hdr, len) (hdr)->_hwlen_protolen = HTONS(ARPH_PROTOLEN(hdr) | ((len) << 8)) |
| #define ARPH_PROTOLEN_SET(hdr, len) (hdr)->_hwlen_protolen = HTONS((len) | (ARPH_HWLEN(hdr) << 8)) |
| |
| enum etharp_state { |
| ETHARP_STATE_EMPTY, |
| ETHARP_STATE_PENDING, |
| ETHARP_STATE_STABLE |
| }; |
| |
| struct etharp_entry { |
| struct ip_addr ipaddr; |
| struct eth_addr ethaddr; |
| enum etharp_state state; |
| #if ARP_QUEUEING |
| struct pbuf *p; |
| #endif |
| u8_t ctime; |
| }; |
| |
| static const struct eth_addr ethbroadcast = {{0xff,0xff,0xff,0xff,0xff,0xff}}; |
| static struct etharp_entry arp_table[ARP_TABLE_SIZE]; |
| static u8_t ctime; |
| |
| static struct pbuf *update_arp_entry(struct netif *netif, struct ip_addr *ipaddr, struct eth_addr *ethaddr, u8_t flags); |
| #define ARP_INSERT_FLAG 1 |
| |
| /** |
| * Initializes ARP module. |
| */ |
| void |
| etharp_init(void) |
| { |
| u8_t i; |
| /* clear ARP entries */ |
| for(i = 0; i < ARP_TABLE_SIZE; ++i) { |
| arp_table[i].state = ETHARP_STATE_EMPTY; |
| #if ARP_QUEUEING |
| arp_table[i].p = NULL; |
| #endif |
| } |
| /* reset ARP current time */ |
| ctime = 0; |
| } |
| |
| /** |
| * Clears expired entries in the ARP table. |
| * |
| * This function should be called every ETHARP_TMR_INTERVAL microseconds (10 seconds), |
| * in order to expire entries in the ARP table. |
| */ |
| void |
| etharp_tmr(void) |
| { |
| u8_t i; |
| |
| ++ctime; |
| DEBUGF(ETHARP_DEBUG, ("etharp_timer\n")); |
| /* remove expired entries from the ARP table */ |
| for(i = 0; i < ARP_TABLE_SIZE; ++i) { |
| if((arp_table[i].state == ETHARP_STATE_STABLE) && |
| (ctime - arp_table[i].ctime >= ARP_MAXAGE)) { |
| DEBUGF(ETHARP_DEBUG, ("etharp_timer: expired stable entry %u.\n", i)); |
| arp_table[i].state = ETHARP_STATE_EMPTY; |
| #if ARP_QUEUEING |
| /* remove any queued packet */ |
| pbuf_free(arp_table[i].p); |
| arp_table[i].p = NULL; |
| #endif |
| } else if((arp_table[i].state == ETHARP_STATE_PENDING) && |
| (ctime - arp_table[i].ctime >= ARP_MAXPENDING)) { |
| arp_table[i].state = ETHARP_STATE_EMPTY; |
| #if ARP_QUEUEING |
| DEBUGF(ETHARP_DEBUG, ("etharp_timer: expired pending entry %u - dequeueing %p.\n", i, (void *)(arp_table[i].p))); |
| /* remove any queued packet */ |
| pbuf_free(arp_table[i].p); |
| arp_table[i].p = NULL; |
| #else |
| DEBUGF(ETHARP_DEBUG, ("etharp_timer: expired pending entry %u.\n", i)); |
| #endif |
| } |
| } |
| } |
| |
| /** |
| * Return an empty ARP entry or, if the table is full, ARP_TABLE_SIZE if all |
| * entries are pending, otherwise the oldest entry. |
| * |
| * @return The ARP entry index that is available, ARP_TABLE_SIZE if no usable |
| * entry is found. |
| */ |
| static u8_t |
| find_arp_entry(void) |
| { |
| u8_t i, j, maxtime; |
| |
| /* Try to find an unused entry in the ARP table. */ |
| for(i = 0; i < ARP_TABLE_SIZE; ++i) { |
| if(arp_table[i].state == ETHARP_STATE_EMPTY) { |
| DEBUGF(ETHARP_DEBUG, ("find_arp_entry: found empty entry %u\n", i)); |
| break; |
| } |
| } |
| |
| /* If no unused entry is found, we try to find the oldest entry and |
| throw it away. */ |
| if(i == ARP_TABLE_SIZE) { |
| maxtime = 0; |
| j = ARP_TABLE_SIZE; |
| for(i = 0; i < ARP_TABLE_SIZE; ++i) { |
| /* remember entry with oldest stable entry in j*/ |
| if((arp_table[i].state == ETHARP_STATE_STABLE) && |
| (ctime - arp_table[i].ctime > maxtime)) { |
| maxtime = ctime - arp_table[i].ctime; |
| j = i; |
| } |
| } |
| DEBUGF(ETHARP_DEBUG, ("find_arp_entry: found oldest stable entry %u\n", j)); |
| i = j; |
| } |
| DEBUGF(ETHARP_DEBUG, ("find_arp_entry: returning %u, state %u\n", i, arp_table[i].state)); |
| return i; |
| } |
| |
| /** |
| * Update (or insert) a IP/MAC address pair in the ARP cache. |
| * |
| * @param ipaddr IP address of the inserted ARP entry. |
| * @param ethaddr Ethernet address of the inserted ARP entry. |
| * @param flags Defines behaviour: |
| * - ARP_INSERT_FLAG Allows ARP to insert this as a new item. If not specified, |
| * only existing ARP entries will be updated. |
| * |
| * @return pbuf If non-NULL, a packet that was queued on a pending entry. |
| * You should sent it and must call pbuf_free() afterwards. |
| * |
| * @see pbuf_free() |
| */ |
| static struct pbuf * |
| update_arp_entry(struct netif *netif, struct ip_addr *ipaddr, struct eth_addr *ethaddr, u8_t flags) |
| { |
| u8_t i, k; |
| #if ARP_QUEUEING |
| struct eth_hdr *ethhdr; |
| #endif |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry()")); |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: %u.%u.%u.%u - %02x:%02x:%02x:%02x:%02x:%02x\n", ip4_addr1(ipaddr), ip4_addr2(ipaddr), ip4_addr3(ipaddr), ip4_addr4(ipaddr), |
| ethaddr->addr[0], ethaddr->addr[1], ethaddr->addr[2], ethaddr->addr[3], ethaddr->addr[4], ethaddr->addr[5])); |
| /* do not update for 0.0.0.0 addresses */ |
| if (ipaddr->addr == 0) { |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: will not add 0.0.0.0 to ARP cache\n")); |
| return NULL; |
| } |
| /* Walk through the ARP mapping table and try to find an entry to |
| update. If none is found, the IP -> MAC address mapping is |
| inserted in the ARP table. */ |
| for(i = 0; i < ARP_TABLE_SIZE; ++i) { |
| /* Check if the source IP address of the incoming packet matches |
| the IP address in this ARP table entry. */ |
| if(ip_addr_cmp(ipaddr, &arp_table[i].ipaddr)) { |
| /* pending entry? */ |
| if(arp_table[i].state == ETHARP_STATE_PENDING) { |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: pending entry %u goes stable\n", i)); |
| /* A pending entry was found, mark it stable */ |
| arp_table[i].state = ETHARP_STATE_STABLE; |
| /* fall-through to next if */ |
| } |
| /* stable entry? (possible just marked to become stable) */ |
| if(arp_table[i].state == ETHARP_STATE_STABLE) { |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: updating stable entry %u\n", i)); |
| /* An old entry found, update this and return. */ |
| for(k = 0; k < 6; ++k) { |
| arp_table[i].ethaddr.addr[k] = ethaddr->addr[k]; |
| } |
| /* time stamp */ |
| arp_table[i].ctime = ctime; |
| #if ARP_QUEUEING |
| /* queued packet present? */ |
| if(arp_table[i].p != NULL) { |
| |
| /* fill-in Ethernet header */ |
| ethhdr = arp_table[i].p->payload; |
| for(k = 0; k < 6; ++k) { |
| ethhdr->dest.addr[k] = ethaddr->addr[k]; |
| } |
| ethhdr->type = htons(ETHTYPE_IP); |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: sending queued IP packet.\n")); |
| /* send the queued IP packet */ |
| netif->linkoutput(netif, arp_table[i].p); |
| /* free the queued IP packet */ |
| pbuf_free(arp_table[i].p); |
| /* remove queued packet from ARP entry (must be freed by the caller) */ |
| arp_table[i].p = NULL; |
| } |
| #endif |
| return NULL; |
| } |
| } /* if */ |
| } /* for */ |
| |
| /* no matching ARP entry was found */ |
| ASSERT("update_arp_entry: i == ARP_TABLE_SIZE", i == ARP_TABLE_SIZE); |
| |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: IP address not yet in table\n")); |
| /* allowed to insert an entry? */ |
| if ((ETHARP_ALWAYS_INSERT) || (flags & ARP_INSERT_FLAG)) |
| { |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: adding entry to table\n")); |
| /* find an empty or old entry. */ |
| i = find_arp_entry(); |
| if(i == ARP_TABLE_SIZE) { |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: no available entry found\n")); |
| return NULL; |
| } |
| /* see if find_arp_entry() gave us an old stable, or empty entry to re-use */ |
| if (arp_table[i].state == ETHARP_STATE_STABLE) { |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: overwriting old stable entry %u\n", i)); |
| /* stable entries should have no queued packets (TODO: allow later) */ |
| ASSERT("update_arp_entry: arp_table[i].p == NULL", arp_table[i].p == NULL); |
| } else { |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: filling empty entry %u with state %u\n", i, arp_table[i].state)); |
| ASSERT("update_arp_entry: arp_table[i].state == ETHARP_STATE_EMPTY", arp_table[i].state == ETHARP_STATE_EMPTY); |
| } |
| /* set IP address */ |
| ip_addr_set(&arp_table[i].ipaddr, ipaddr); |
| /* set Ethernet hardware address */ |
| for(k = 0; k < 6; ++k) { |
| arp_table[i].ethaddr.addr[k] = ethaddr->addr[k]; |
| } |
| /* time-stamp */ |
| arp_table[i].ctime = ctime; |
| /* mark as stable */ |
| arp_table[i].state = ETHARP_STATE_STABLE; |
| /* no queued packet */ |
| #if ARP_QUEUEING |
| arp_table[i].p = NULL; |
| #endif |
| } |
| else |
| { |
| DEBUGF(ETHARP_DEBUG, ("update_arp_entry: no matching stable entry to update\n")); |
| } |
| return NULL; |
| } |
| |
| /** |
| * Updates the ARP table using the given packet. |
| * |
| * Uses the incoming IP packet's source address to update the |
| * ARP cache for the local network. The function does not alter |
| * or free the packet. This function must be called before the |
| * packet p is passed to the IP layer. |
| * |
| * @param netif The lwIP network interface on which the IP packet pbuf arrived. |
| * @param pbuf The IP packet that arrived on netif. |
| * |
| * @return NULL |
| * |
| * @see pbuf_free() |
| */ |
| struct pbuf * |
| etharp_ip_input(struct netif *netif, struct pbuf *p) |
| { |
| struct ethip_hdr *hdr; |
| |
| /* Only insert an entry if the source IP address of the |
| incoming IP packet comes from a host on the local network. */ |
| hdr = p->payload; |
| /* source is on local network? */ |
| if(!ip_addr_maskcmp(&(hdr->ip.src), &(netif->ip_addr), &(netif->netmask))) { |
| /* do nothing */ |
| return NULL; |
| } |
| |
| DEBUGF(ETHARP_DEBUG, ("etharp_ip_input: updating ETHARP table.\n")); |
| /* update ARP table, ask to insert entry */ |
| update_arp_entry(netif, &(hdr->ip.src), &(hdr->eth.src), ARP_INSERT_FLAG); |
| return NULL; |
| } |
| |
| |
| /** |
| * Responds to ARP requests, updates ARP entries and sends queued IP packets. |
| * |
| * Should be called for incoming ARP packets. The pbuf in the argument |
| * is freed by this function. |
| * |
| * @param netif The lwIP network interface on which the ARP packet pbuf arrived. |
| * @param pbuf The ARP packet that arrived on netif. Is freed by this function. |
| * @param ethaddr Ethernet address of netif. |
| * |
| * @return NULL |
| * |
| * @see pbuf_free() |
| */ |
| struct pbuf * |
| etharp_arp_input(struct netif *netif, struct eth_addr *ethaddr, struct pbuf *p) |
| { |
| struct etharp_hdr *hdr; |
| u8_t i; |
| |
| /* drop short ARP packets */ |
| if(p->tot_len < sizeof(struct etharp_hdr)) { |
| DEBUGF(ETHARP_DEBUG, ("etharp_arp_input: packet too short (%d/%d)\n", p->tot_len, sizeof(struct etharp_hdr))); |
| pbuf_free(p); |
| return NULL; |
| } |
| |
| hdr = p->payload; |
| |
| switch(htons(hdr->opcode)) { |
| /* ARP request? */ |
| case ARP_REQUEST: |
| /* ARP request. If it asked for our address, we send out a |
| reply. In any case, we time-stamp any existing ARP entry, |
| and possiby send out an IP packet that was queued on it. */ |
| |
| DEBUGF(ETHARP_DEBUG, ("etharp_arp_input: incoming ARP request\n")); |
| /* we are not configured? */ |
| if(netif->ip_addr.addr == 0) { |
| DEBUGF(ETHARP_DEBUG, ("etharp_arp_input: we are unconfigured, ARP request ignored.\n")); |
| pbuf_free(p); |
| return NULL; |
| } |
| /* update the ARP cache */ |
| update_arp_entry(netif, &(hdr->sipaddr), &(hdr->shwaddr), 0); |
| /* ARP request for our address? */ |
| if(ip_addr_cmp(&(hdr->dipaddr), &(netif->ip_addr))) { |
| |
| DEBUGF(ETHARP_DEBUG, ("etharp_arp_input: replying to ARP request for our IP address\n")); |
| /* re-use pbuf to send ARP reply */ |
| hdr->opcode = htons(ARP_REPLY); |
| |
| ip_addr_set(&(hdr->dipaddr), &(hdr->sipaddr)); |
| ip_addr_set(&(hdr->sipaddr), &(netif->ip_addr)); |
| |
| for(i = 0; i < 6; ++i) { |
| hdr->dhwaddr.addr[i] = hdr->shwaddr.addr[i]; |
| hdr->shwaddr.addr[i] = ethaddr->addr[i]; |
| hdr->ethhdr.dest.addr[i] = hdr->dhwaddr.addr[i]; |
| hdr->ethhdr.src.addr[i] = ethaddr->addr[i]; |
| } |
| |
| hdr->hwtype = htons(HWTYPE_ETHERNET); |
| ARPH_HWLEN_SET(hdr, 6); |
| |
| hdr->proto = htons(ETHTYPE_IP); |
| ARPH_PROTOLEN_SET(hdr, sizeof(struct ip_addr)); |
| |
| hdr->ethhdr.type = htons(ETHTYPE_ARP); |
| /* return ARP reply */ |
| netif->linkoutput(netif, p); |
| } else { |
| DEBUGF(ETHARP_DEBUG, ("etharp_arp_input: incoming ARP request was not for us.\n")); |
| } |
| break; |
| case ARP_REPLY: |
| /* ARP reply. We insert or update the ARP table. */ |
| DEBUGF(ETHARP_DEBUG, ("etharp_arp_input: incoming ARP reply\n")); |
| #if (LWIP_DHCP && DHCP_DOES_ARP_CHECK) |
| /* DHCP needs to know about ARP replies */ |
| dhcp_arp_reply(&hdr->sipaddr); |
| #endif |
| /* ARP reply directed to us? */ |
| if(ip_addr_cmp(&(hdr->dipaddr), &(netif->ip_addr))) { |
| DEBUGF(ETHARP_DEBUG, ("etharp_arp_input: incoming ARP reply is for us\n")); |
| /* update_the ARP cache, ask to insert */ |
| update_arp_entry(netif, &(hdr->sipaddr), &(hdr->shwaddr), ARP_INSERT_FLAG); |
| /* ARP reply not directed to us */ |
| } else { |
| DEBUGF(ETHARP_DEBUG, ("etharp_arp_input: incoming ARP reply is not for us\n")); |
| /* update the destination address pair */ |
| update_arp_entry(netif, &(hdr->sipaddr), &(hdr->shwaddr), 0); |
| /* update the destination address pair */ |
| update_arp_entry(netif, &(hdr->dipaddr), &(hdr->dhwaddr), 0); |
| } |
| break; |
| default: |
| DEBUGF(ETHARP_DEBUG, ("etharp_arp_input: ARP unknown opcode type %d\n", htons(hdr->opcode))); |
| break; |
| } |
| /* free ARP packet */ |
| pbuf_free(p); |
| p = NULL; |
| /* nothing to send, we did it! */ |
| return NULL; |
| } |
| |
| /** |
| * Resolve and fill-in Ethernet address header for outgoing packet. |
| * |
| * If ARP has the Ethernet address in cache, the given packet is |
| * returned, ready to be sent. |
| * |
| * If ARP does not have the Ethernet address in cache the packet is |
| * queued and a ARP request is sent (on a best-effort basis). This |
| * ARP request is returned as a pbuf, which should be sent by the |
| * caller. |
| * |
| * If ARP failed to allocate resources, NULL is returned. |
| * |
| * A returned non-NULL packet should be sent by the caller and |
| * etharp_output_sent() must be called afterwards to free any ARP |
| * request. |
| * |
| * @param netif The lwIP network interface which the IP packet will be sent on. |
| * @param ipaddr The IP address of the packet destination. |
| * @param pbuf The pbuf(s) containing the IP packet to be sent. |
| * |
| * @return If non-NULL, a packet ready to be sent. |
| * @see etharp_output_sent() |
| */ |
| struct pbuf * |
| etharp_output(struct netif *netif, struct ip_addr *ipaddr, struct pbuf *q) |
| { |
| struct eth_addr *dest, *srcaddr, mcastaddr; |
| struct eth_hdr *ethhdr; |
| u8_t i; |
| |
| /* Make room for Ethernet header. */ |
| if(pbuf_header(q, sizeof(struct eth_hdr)) != 0) { |
| /* The pbuf_header() call shouldn't fail, and we'll just bail |
| out if it does.. */ |
| DEBUGF(ETHARP_DEBUG, ("etharp_output: could not allocate room for header.\n")); |
| #ifdef LINK_STATS |
| ++lwip_stats.link.lenerr; |
| #endif /* LINK_STATS */ |
| return NULL; |
| } |
| |
| /* obtain source Ethernet address of the given interface */ |
| srcaddr = (struct eth_addr *)netif->hwaddr; |
| |
| /* assume unresolved Ethernet address */ |
| dest = NULL; |
| /* Construct Ethernet header. Start with looking up deciding which |
| MAC address to use as a destination address. Broadcasts and |
| multicasts are special, all other addresses are looked up in the |
| ARP table. */ |
| |
| /* destination IP address is an IP broadcast address? */ |
| if(ip_addr_isany(ipaddr) || |
| ip_addr_isbroadcast(ipaddr, &(netif->netmask))) { |
| /* broadcast on Ethernet also */ |
| dest = (struct eth_addr *)ðbroadcast; |
| } |
| /* destination IP address is an IP multicast address? */ |
| else if(ip_addr_ismulticast(ipaddr)) { |
| /* Hash IP multicast address to MAC address. */ |
| mcastaddr.addr[0] = 0x01; |
| mcastaddr.addr[1] = 0x0; |
| mcastaddr.addr[2] = 0x5e; |
| mcastaddr.addr[3] = ip4_addr2(ipaddr) & 0x7f; |
| mcastaddr.addr[4] = ip4_addr3(ipaddr); |
| mcastaddr.addr[5] = ip4_addr4(ipaddr); |
| /* destination Ethernet address is multicast */ |
| dest = &mcastaddr; |
| } |
| /* destination IP address is an IP unicast address */ |
| else { |
| /* destination IP network address not on local network? */ |
| /* this occurs if the packet is routed to the default gateway on this interface */ |
| if(!ip_addr_maskcmp(ipaddr, &(netif->ip_addr), &(netif->netmask))) { |
| /* gateway available? */ |
| if (netif->gw.addr != 0) |
| { |
| /* use the gateway IP address */ |
| ipaddr = &(netif->gw); |
| } |
| /* no gateway available? */ |
| else |
| { |
| /* IP destination address outside local network, but no gateway available */ |
| return NULL; |
| } |
| } |
| |
| /* Ethernet address for IP destination address is in ARP cache? */ |
| for(i = 0; i < ARP_TABLE_SIZE; ++i) { |
| /* match found? */ |
| if(arp_table[i].state == ETHARP_STATE_STABLE && |
| ip_addr_cmp(ipaddr, &arp_table[i].ipaddr)) { |
| dest = &arp_table[i].ethaddr; |
| break; |
| } |
| } |
| /* could not find the destination Ethernet address in ARP cache? */ |
| if (dest == NULL) { |
| /* ARP query for the IP address, submit this IP packet for queueing */ |
| etharp_query(netif, ipaddr, q); |
| /* return nothing */ |
| return NULL; |
| } |
| /* destination Ethernet address resolved from ARP cache */ |
| else |
| { |
| /* fallthrough */ |
| } |
| } |
| |
| /* destination Ethernet address known */ |
| if (dest != NULL) { |
| /* A valid IP->MAC address mapping was found, so we construct the |
| Ethernet header for the outgoing packet. */ |
| ethhdr = q->payload; |
| |
| for(i = 0; i < 6; i++) { |
| ethhdr->dest.addr[i] = dest->addr[i]; |
| ethhdr->src.addr[i] = srcaddr->addr[i]; |
| } |
| |
| ethhdr->type = htons(ETHTYPE_IP); |
| /* return the outgoing packet */ |
| return q; |
| } |
| /* never reached; here for safety */ |
| return NULL; |
| } |
| |
| /** |
| * Send an ARP request for the given IP address. |
| * |
| * Sends an ARP request for the given IP address, unless |
| * a request for this address is already pending. Optionally |
| * queues an outgoing packet on the resulting ARP entry. |
| * |
| * @param netif The lwIP network interface where ipaddr |
| * must be queried for. |
| * @param ipaddr The IP address to be resolved. |
| * @param q If non-NULL, a pbuf that must be queued on the |
| * ARP entry for the ipaddr IP address. |
| * |
| * @return NULL. |
| * |
| * @note Might be used in the future by manual IP configuration |
| * as well. |
| * |
| * TODO: enqueue q here if possible (BEWARE: possible other packet already |
| * queued. |
| * TODO: The host requirements RFC states that ARP should save at least one |
| * packet, and this should be the _latest_ packet. |
| * TODO: use the ctime field to see how long ago an ARP request was sent, |
| * possibly retry. |
| */ |
| struct pbuf *etharp_query(struct netif *netif, struct ip_addr *ipaddr, struct pbuf *q) |
| { |
| struct eth_addr *srcaddr; |
| struct etharp_hdr *hdr; |
| struct pbuf *p; |
| u8_t i; |
| |
| srcaddr = (struct eth_addr *)netif->hwaddr; |
| /* bail out if this IP address is pending */ |
| for(i = 0; i < ARP_TABLE_SIZE; ++i) { |
| if(ip_addr_cmp(ipaddr, &arp_table[i].ipaddr)) { |
| if (arp_table[i].state == ETHARP_STATE_PENDING) { |
| DEBUGF(ETHARP_DEBUG, ("etharp_query: requested IP already pending\n")); |
| /* break out of for-loop */ |
| break; |
| } |
| else if (arp_table[i].state == ETHARP_STATE_STABLE) { |
| DEBUGF(ETHARP_DEBUG, ("etharp_query: requested IP already stable\n")); |
| return NULL; |
| } |
| } |
| } |
| /* queried address not yet pending in ARP table? */ |
| if (i == ARP_TABLE_SIZE) |
| { |
| DEBUGF(ETHARP_DEBUG, ("etharp_query: IP address non-pending\n")); |
| /* find an available entry */ |
| i = find_arp_entry(); |
| /* bail out if no ARP entries are available */ |
| if(i == ARP_TABLE_SIZE) |
| { |
| DEBUGF(ETHARP_DEBUG, ("etharp_query: no more ARP table entries available.\n")); |
| return NULL; |
| } |
| DEBUGF(ETHARP_DEBUG, ("etharp_query: created ARP table entry.\n")); |
| /* i is available, create ARP entry */ |
| ip_addr_set(&arp_table[i].ipaddr, ipaddr); |
| arp_table[i].ctime = ctime; |
| arp_table[i].state = ETHARP_STATE_PENDING; |
| #if ARP_QUEUEING |
| arp_table[i].p = NULL; |
| #endif |
| } |
| /* allocate a pbuf for the outgoing ARP request packet */ |
| p = pbuf_alloc(PBUF_LINK, sizeof(struct etharp_hdr), PBUF_RAM); |
| /* could allocate pbuf? */ |
| if (p != NULL) { |
| DEBUGF(ETHARP_DEBUG, ("etharp_query: sending ARP request.\n")); |
| hdr = p->payload; |
| hdr->opcode = htons(ARP_REQUEST); |
| for(i = 0; i < 6; ++i) |
| { |
| hdr->dhwaddr.addr[i] = 0x00; |
| hdr->shwaddr.addr[i] = srcaddr->addr[i]; |
| } |
| ip_addr_set(&(hdr->dipaddr), ipaddr); |
| ip_addr_set(&(hdr->sipaddr), &(netif->ip_addr)); |
| |
| hdr->hwtype = htons(HWTYPE_ETHERNET); |
| ARPH_HWLEN_SET(hdr, 6); |
| |
| hdr->proto = htons(ETHTYPE_IP); |
| ARPH_PROTOLEN_SET(hdr, sizeof(struct ip_addr)); |
| for(i = 0; i < 6; ++i) |
| { |
| hdr->ethhdr.dest.addr[i] = 0xff; |
| hdr->ethhdr.src.addr[i] = srcaddr->addr[i]; |
| } |
| hdr->ethhdr.type = htons(ETHTYPE_ARP); |
| /* send ARP query */ |
| netif->linkoutput(netif, p); |
| /* free ARP query packet */ |
| pbuf_free(p); |
| p = NULL; |
| } else { |
| DEBUGF(ETHARP_DEBUG, ("etharp_query: could not allocate pbuf for ARP request.\n")); |
| } |
| #if ARP_QUEUEING |
| /* any pbuf to queue and queue is empty? */ |
| if ((q != NULL) && (arp_table[i].p == NULL)) { |
| /* copy PBUF_REF referenced payloads to PBUF_RAM */ |
| q = pbuf_unref(q); |
| /* pbufs are queued, increase the reference count */ |
| pbuf_ref_chain(q); |
| /* remember pbuf to queue, if any */ |
| arp_table[i].p = q; |
| DEBUGF(ETHARP_DEBUG, ("etharp_query: queued packet on ARP entry.\n")); |
| } |
| #endif |
| return NULL; |
| } |