lwip/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 configured? */
    if(!ip_addr_isany(&(netif->ip_addr)))
    {
      /* unicast to this interface address? */
      if(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 out of for loop */
         break;
      }
    }
#if LWIP_DHCP
  /* Pass DHCP messages in case of an unconfigured (0.0.0.0) interface, regardless
     of destination address. (DHCP replies are sent to the IP address-to-be. This
     is according to RFC 1542 section 3.1.1, referred by RFC 2131). */

    /* interface unconfigured (0.0.0.0) */
    else {
      /* remote port is DHCP server? */
      if(IPH_PROTO(iphdr) == IP_PROTO_UDP &&
       ((struct udp_hdr *)((u8_t *)iphdr + IPH_HL(iphdr) * 4))->src == DHCP_SERVER_PORT) {
         netif = inp;
         /* break out of for loop */
         break;
      }
    }
#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 */
/*-----------------------------------------------------------------------------------*/