src/core/ipv4/ip.c

/*
 * 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>
 *
 */


/*-----------------------------------------------------------------------------------*/
/* ip.c
 *
 * This is the code for the IP layer.
 *
 */   
/*-----------------------------------------------------------------------------------*/

#include "lwip/debug.h"

#include "lwip/def.h"
#include "lwip/mem.h"
#include "lwip/ip.h"
#include "lwip/ip_frag.h"
#include "lwip/inet.h"
#include "lwip/netif.h"
#include "lwip/icmp.h"
#include "lwip/udp.h"
#include "lwip/tcp.h"

#include "lwip/stats.h"

#include "arch/perf.h"

#if LWIP_SNMP > 0
#  include "snmp.h"
#endif
#if LWIP_DHCP
#include "lwip/dhcp.h"
#endif /* LWIP_DHCP */

/*-----------------------------------------------------------------------------------*/
/* ip_init:
 *
 * Initializes the IP layer.
 */
/*-----------------------------------------------------------------------------------*/
void
ip_init(void)
{
}
/*-----------------------------------------------------------------------------------*/
/* ip_lookup:
 *
 * An experimental feature that will be changed in future versions. Do
 * not depend on it yet...
 */
/*-----------------------------------------------------------------------------------*/
#ifdef LWIP_DEBUG
u8_t
ip_lookup(void *header, struct netif *inp)
{
  struct ip_hdr *iphdr;

  iphdr = header;

  /* Refuse anything that isn't IPv4. */
  if(IPH_V(iphdr) != 4) {
    return 0;
  }

  /* Immediately accept/decline packets that are fragments or has
     options. */
#if IP_REASSEMBLY == 0
  /*  if((IPH_OFFSET(iphdr) & htons(IP_OFFMASK | IP_MF)) != 0) {
    return 0;
    }*/
#endif /* IP_REASSEMBLY == 0 */

#if IP_OPTIONS == 0
  if(IPH_HL(iphdr) != 5) {
    return 0;
  }
#endif /* IP_OPTIONS == 0 */
  
  switch(IPH_PROTO(iphdr)) {
#if LWIP_UDP > 0
  case IP_PROTO_UDP:
    return udp_lookup(iphdr, inp);
    break;
#endif /* LWIP_UDP */
#if LWIP_TCP > 0    
  case IP_PROTO_TCP:
    return 1;
#endif /* LWIP_TCP */
  case IP_PROTO_ICMP:
    return 1;
    break;
  default:
    return 0;
  }
}
#endif /* LWIP_DEBUG */
/*-----------------------------------------------------------------------------------*/
/* ip_route:
 *
 * Finds the appropriate network interface for a given IP address. It
 * searches the list of network interfaces linearly. A match is found
 * if the masked IP address of the network interface equals the masked
 * IP address given to the function.
 */
/*-----------------------------------------------------------------------------------*/
struct netif *
ip_route(struct ip_addr *dest)
{
  struct netif *netif;
  
  for(netif = netif_list; netif != NULL; netif = netif->next) {
    if(ip_addr_maskcmp(dest, &(netif->ip_addr), &(netif->netmask))) {
      return netif;
    }
  }

  return netif_default;
}
#if IP_FORWARD
/*-----------------------------------------------------------------------------------*/
/* ip_forward:
 *
 * Forwards an IP packet. It finds an appropriate route for the
 * packet, decrements the TTL value of the packet, adjusts the
 * checksum and outputs the packet on the appropriate interface.
 */
/*-----------------------------------------------------------------------------------*/
static void
ip_forward(struct pbuf *p, struct ip_hdr *iphdr, struct netif *inp)
{
  struct netif *netif;
  
  PERF_START;
  
  if((netif = ip_route((struct ip_addr *)&(iphdr->dest))) == NULL) {

    DEBUGF(IP_DEBUG, ("ip_forward: no forwarding route for 0x%lx found\n",
		      iphdr->dest.addr));

#if LWIP_SNMP > 0
    snmp_inc_ipnoroutes();
#endif
    return;
  }

  /* Don't forward packets onto the same network interface on which
     they arrived. */
  if(netif == inp) {
    DEBUGF(IP_DEBUG, ("ip_forward: not forward packets back on incoming interface.\n"));

#if LWIP_SNMP > 0
    snmp_inc_ipnoroutes();
#endif
    return;
  }
  
  /* Decrement TTL and send ICMP if ttl == 0. */
  IPH_TTL_SET(iphdr, IPH_TTL(iphdr) - 1);
  if(IPH_TTL(iphdr) == 0) {
    /* Don't send ICMP messages in response to ICMP messages */
    if(IPH_PROTO(iphdr) != IP_PROTO_ICMP) {
      icmp_time_exceeded(p, ICMP_TE_TTL);
#if LWIP_SNMP > 0
      snmp_inc_icmpouttimeexcds();
#endif
    }
    return;       
  }
  
  /* Incremental update of the IP checksum. */
  if(IPH_CHKSUM(iphdr) >= htons(0xffff - 0x100)) {
    IPH_CHKSUM_SET(iphdr, IPH_CHKSUM(iphdr) + htons(0x100) + 1);
  } else {
    IPH_CHKSUM_SET(iphdr, IPH_CHKSUM(iphdr) + htons(0x100));
  }

  DEBUGF(IP_DEBUG, ("ip_forward: forwarding packet to 0x%lx\n",
		    iphdr->dest.addr));

#ifdef IP_STATS
  ++lwip_stats.ip.fw;
  ++lwip_stats.ip.xmit;
#endif /* IP_STATS */
#if LWIP_SNMP > 0
    snmp_inc_ipforwdatagrams();
#endif

  PERF_STOP("ip_forward");
  
  netif->output(netif, p, (struct ip_addr *)&(iphdr->dest));
}
#endif /* IP_FORWARD */
/*-----------------------------------------------------------------------------------*/
/* ip_input:
 *
 * This function is called by the network interface device driver when
 * an IP packet is received. The function does the basic checks of the
 * IP header such as packet size being at least larger than the header
 * size etc. If the packet was not destined for us, the packet is
 * forwarded (using ip_forward). The IP checksum is always checked.
 *
 * Finally, the packet is sent to the upper layer protocol input function.
 */
/*-----------------------------------------------------------------------------------*/
err_t
ip_input(struct pbuf *p, struct netif *inp) {
  static struct ip_hdr *iphdr;
  static struct netif *netif;
  static u8_t hl;

  
  
#ifdef IP_STATS
  ++lwip_stats.ip.recv;
#endif /* IP_STATS */
#if LWIP_SNMP > 0
    snmp_inc_ipinreceives();
#endif

  /* identify the IP header */
  iphdr = p->payload;
  if(IPH_V(iphdr) != 4) {
    DEBUGF(IP_DEBUG, ("IP packet dropped due to bad version number %d\n", IPH_V(iphdr)));
#if IP_DEBUG
    ip_debug_print(p);
#endif /* IP_DEBUG */
    pbuf_free(p);
#ifdef IP_STATS
    ++lwip_stats.ip.err;
    ++lwip_stats.ip.drop;
#endif /* IP_STATS */
#if LWIP_SNMP > 0
    snmp_inc_ipunknownprotos();
#endif
    return ERR_OK;
  }
  
  hl = IPH_HL(iphdr);
  
  if(hl * 4 > p->len) {
    DEBUGF(IP_DEBUG, ("IP packet dropped due to too short packet %d\n", p->len));

    pbuf_free(p);
#ifdef IP_STATS
    ++lwip_stats.ip.lenerr;
    ++lwip_stats.ip.drop;
#endif /* IP_STATS */
#if LWIP_SNMP > 0
    snmp_inc_ipindiscards();
#endif
    return ERR_OK;
  }

  /* verify checksum */
  if(inet_chksum(iphdr, hl * 4) != 0) {

    DEBUGF(IP_DEBUG, ("IP packet dropped due to failing checksum 0x%x\n", inet_chksum(iphdr, hl * 4)));
#if IP_DEBUG
    ip_debug_print(p);
#endif /* IP_DEBUG */
    pbuf_free(p);
#ifdef IP_STATS
    ++lwip_stats.ip.chkerr;
    ++lwip_stats.ip.drop;
#endif /* IP_STATS */
#if LWIP_SNMP > 0
    snmp_inc_ipindiscards();
#endif
    return ERR_OK;
  }
  
  /* Trim pbuf. This should have been done at the netif layer,
     but we'll do it anyway just to be sure that its done. */
  pbuf_realloc(p, ntohs(IPH_LEN(iphdr)));

  /* is this packet for us? */
  for(netif = netif_list; netif != NULL; netif = netif->next) {

    DEBUGF(IP_DEBUG, ("ip_input: iphdr->dest 0x%lx netif->ip_addr 0x%lx (0x%lx, 0x%lx, 0x%lx)\n",
		      iphdr->dest.addr, netif->ip_addr.addr,
		      iphdr->dest.addr & netif->netmask.addr,
		      netif->ip_addr.addr & netif->netmask.addr,
		      iphdr->dest.addr & ~(netif->netmask.addr)));

    /* interface unconfigured? */
    if(ip_addr_isany(&(netif->ip_addr)) ||
       /* or unicast to this interface address? */
       ip_addr_cmp(&(iphdr->dest), &(netif->ip_addr)) ||
       /* or broadcast on this interface network address ? */
       (ip_addr_isbroadcast(&(iphdr->dest), &(netif->netmask)) &&
	ip_addr_maskcmp(&(iphdr->dest), &(netif->ip_addr), &(netif->netmask))) ||
       /* or restricted broadcast? */
       ip_addr_cmp(&(iphdr->dest), IP_ADDR_BROADCAST)) {
      break;
    }
  }

#if LWIP_DHCP
  /* If a DHCP packet has arrived on the interface, we pass it up the
     stack regardless of destination IP address. The reason is that
     DHCP replies are sent to the IP adress that will be given to this
     node (as recommended by RFC 1542 section 3.1.1, referred by RFC
     2131). */
  if(IPH_PROTO(iphdr) == IP_PROTO_UDP &&
     ((struct udp_hdr *)((u8_t *)iphdr + IPH_HL(iphdr) * 4))->src ==
     DHCP_SERVER_PORT) {
    netif = inp;
  }  
#endif /* LWIP_DHCP */
	  
  if(netif == NULL) {
    /* packet not for us, route or discard */
    DEBUGF(IP_DEBUG, ("ip_input: packet not for us.\n"));
#if IP_FORWARD
    if(!ip_addr_isbroadcast(&(iphdr->dest), &(inp->netmask))) {
      ip_forward(p, iphdr, inp);
    }
    else
#endif /* IP_FORWARD */
    {
#if LWIP_SNMP > 0
      snmp_inc_ipindiscards();
#endif
    }
    pbuf_free(p);
    return ERR_OK;
  }

#if IP_REASSEMBLY
  if((IPH_OFFSET(iphdr) & htons(IP_OFFMASK | IP_MF)) != 0) {
    p = ip_reass(p);
    if(p == NULL) {
      return ERR_OK;
    }
    iphdr = p->payload;
  }
#else /* IP_REASSEMBLY */
  if((IPH_OFFSET(iphdr) & htons(IP_OFFMASK | IP_MF)) != 0) {
    pbuf_free(p);
    DEBUGF(IP_DEBUG, ("IP packet dropped since it was fragmented (0x%x).\n",
		      ntohs(IPH_OFFSET(iphdr))));
#ifdef IP_STATS
    ++lwip_stats.ip.opterr;
    ++lwip_stats.ip.drop;
#endif /* IP_STATS */
#if LWIP_SNMP > 0
    snmp_inc_ipunknownprotos();
#endif
    return ERR_OK;
  }
#endif /* IP_REASSEMBLY */
  
#if IP_OPTIONS == 0
  if(hl * 4 > IP_HLEN) {
    DEBUGF(IP_DEBUG, ("IP packet dropped since there were IP options.\n"));

    pbuf_free(p);    
#ifdef IP_STATS
    ++lwip_stats.ip.opterr;
    ++lwip_stats.ip.drop;
#endif /* IP_STATS */
#if LWIP_SNMP > 0
    snmp_inc_ipunknownprotos();
#endif
    return ERR_OK;
  }  
#endif /* IP_OPTIONS == 0 */


  /* send to upper layers */
#if IP_DEBUG
  DEBUGF(IP_DEBUG, ("ip_input: \n"));
  ip_debug_print(p);
  DEBUGF(IP_DEBUG, ("ip_input: p->len %d p->tot_len %d\n", p->len, p->tot_len));
#endif /* IP_DEBUG */   

  switch(IPH_PROTO(iphdr)) {
#if LWIP_UDP > 0    
  case IP_PROTO_UDP:
#if LWIP_SNMP > 0
    snmp_inc_ipindelivers();
#endif
    udp_input(p, inp);
    break;
#endif /* LWIP_UDP */
#if LWIP_TCP > 0    
  case IP_PROTO_TCP:
#if LWIP_SNMP > 0
    snmp_inc_ipindelivers();
#endif
    tcp_input(p, inp);
    break;
#endif /* LWIP_TCP */
  case IP_PROTO_ICMP:
#if LWIP_SNMP > 0
    snmp_inc_ipindelivers();
#endif
    icmp_input(p, inp);
    break;
  default:
    /* send ICMP destination protocol unreachable unless is was a broadcast */
    if(!ip_addr_isbroadcast(&(iphdr->dest), &(inp->netmask)) &&
       !ip_addr_ismulticast(&(iphdr->dest))) {
      p->payload = iphdr;
      icmp_dest_unreach(p, ICMP_DUR_PROTO);
    }
    pbuf_free(p);

    DEBUGF(IP_DEBUG, ("Unsupported transportation protocol %d\n", IPH_PROTO(iphdr)));

#ifdef IP_STATS
    ++lwip_stats.ip.proterr;
    ++lwip_stats.ip.drop;
#endif /* IP_STATS */
#if LWIP_SNMP > 0
    snmp_inc_ipunknownprotos();
#endif

  }
  return ERR_OK;
}

/*-----------------------------------------------------------------------------------*/
/* ip_output_if:
 *
 * Sends an IP packet on a network interface. This function constructs
 * the IP header and calculates the IP header checksum. If the source
 * IP address is NULL, the IP address of the outgoing network
 * interface is filled in as source address.
 */
/*-----------------------------------------------------------------------------------*/
err_t
ip_output_if(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,
	     u8_t ttl,
	     u8_t proto, struct netif *netif)
{
  static struct ip_hdr *iphdr;
  static u16_t ip_id = 0;

  
#if LWIP_SNMP > 0
    snmp_inc_ipoutrequests();
#endif
  
  if(dest != IP_HDRINCL) {
    if(pbuf_header(p, IP_HLEN)) {
      DEBUGF(IP_DEBUG, ("ip_output: not enough room for IP header in pbuf\n"));
      
#ifdef IP_STATS
      ++lwip_stats.ip.err;
#endif /* IP_STATS */
#if LWIP_SNMP > 0
    snmp_inc_ipoutdiscards();
#endif
      return ERR_BUF;
    }
    
    iphdr = p->payload;
    
    IPH_TTL_SET(iphdr, ttl);
    IPH_PROTO_SET(iphdr, proto);
    
    ip_addr_set(&(iphdr->dest), dest);

    IPH_VHLTOS_SET(iphdr, 4, IP_HLEN / 4, 0);
    IPH_LEN_SET(iphdr, htons(p->tot_len));
    IPH_OFFSET_SET(iphdr, htons(IP_DF));
    IPH_ID_SET(iphdr, htons(ip_id));
    ++ip_id;

    if(ip_addr_isany(src)) {
      ip_addr_set(&(iphdr->src), &(netif->ip_addr));
    } else {
      ip_addr_set(&(iphdr->src), src);
    }

    IPH_CHKSUM_SET(iphdr, 0);
    IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
  } else {
    iphdr = p->payload;
    dest = &(iphdr->dest);
  }

#if IP_FRAG	
  if (p->tot_len > netif->mtu)
    return ip_frag(p,netif,dest);
#endif
  
#ifdef IP_STATS
  lwip_stats.ip.xmit++;
#endif /* IP_STATS */
  DEBUGF(IP_DEBUG, ("ip_output_if: %c%c ", netif->name[0], netif->name[1]));
#if IP_DEBUG
  ip_debug_print(p);
#endif /* IP_DEBUG */

   DEBUGF(IP_DEBUG, ("netif->output()"));

  return netif->output(netif, p, dest);  
}
/*-----------------------------------------------------------------------------------*/
/* ip_output:
 *
 * Simple interface to ip_output_if. It finds the outgoing network
 * interface and calls upon ip_output_if to do the actual work.
 */
/*-----------------------------------------------------------------------------------*/
err_t
ip_output(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,
	  u8_t ttl, u8_t proto)
{
  struct netif *netif;
  
  if((netif = ip_route(dest)) == NULL) {
    DEBUGF(IP_DEBUG, ("ip_output: No route to 0x%lx\n", dest->addr));

#ifdef IP_STATS
    ++lwip_stats.ip.rterr;
#endif /* IP_STATS */
#if LWIP_SNMP > 0
    snmp_inc_ipoutdiscards();
#endif
    return ERR_RTE;
  }

  return ip_output_if(p, src, dest, ttl, proto, netif);
}
/*-----------------------------------------------------------------------------------*/
#if IP_DEBUG
void
ip_debug_print(struct pbuf *p)
{
  struct ip_hdr *iphdr = p->payload;
  u8_t *payload;

  payload = (u8_t *)iphdr + IP_HLEN;
  
  DEBUGF(IP_DEBUG, ("IP header:\n"));
  DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
  DEBUGF(IP_DEBUG, ("|%2d |%2d |   %2d  |      %4d     | (v, hl, tos, len)\n",
		    IPH_V(iphdr),
		    IPH_HL(iphdr),
		    IPH_TOS(iphdr),
		    ntohs(IPH_LEN(iphdr))));
  DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
  DEBUGF(IP_DEBUG, ("|    %5d      |%d%d%d|    %4d   | (id, flags, offset)\n",
		    ntohs(IPH_ID(iphdr)),
		    ntohs(IPH_OFFSET(iphdr)) >> 15 & 1,
		    ntohs(IPH_OFFSET(iphdr)) >> 14 & 1,
		    ntohs(IPH_OFFSET(iphdr)) >> 13 & 1,
		    ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK));
  DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
  DEBUGF(IP_DEBUG, ("|   %2d  |   %2d  |    0x%04x     | (ttl, proto, chksum)\n",
		    IPH_TTL(iphdr),
		    IPH_PROTO(iphdr),
		    ntohs(IPH_CHKSUM(iphdr))));
  DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
  DEBUGF(IP_DEBUG, ("|  %3ld  |  %3ld  |  %3ld  |  %3ld  | (src)\n",
		    ntohl(iphdr->src.addr) >> 24 & 0xff,
		    ntohl(iphdr->src.addr) >> 16 & 0xff,
		    ntohl(iphdr->src.addr) >> 8 & 0xff,
		    ntohl(iphdr->src.addr) & 0xff));
  DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
  DEBUGF(IP_DEBUG, ("|  %3ld  |  %3ld  |  %3ld  |  %3ld  | (dest)\n",
		    ntohl(iphdr->dest.addr) >> 24 & 0xff,
		    ntohl(iphdr->dest.addr) >> 16 & 0xff,
		    ntohl(iphdr->dest.addr) >> 8 & 0xff,
		    ntohl(iphdr->dest.addr) & 0xff));
  DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
}
#endif /* IP_DEBUG */
/*-----------------------------------------------------------------------------------*/