ip.c

lwip-1.4.0

    pbuf_free(p);
    IP_STATS_INC(ip.lenerr);
    IP_STATS_INC(ip.drop);
    snmp_inc_ipindiscards();
    return ERR_OK;
  }

  /* verify checksum */
#if CHECKSUM_CHECK_IP
  if (inet_chksum(iphdr, iphdr_hlen) != 0) {

    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
      ("Checksum (0x%"X16_F") failed, IP packet dropped.\n", inet_chksum(iphdr, iphdr_hlen)));
    ip_debug_print(p);
    pbuf_free(p);
    IP_STATS_INC(ip.chkerr);
    IP_STATS_INC(ip.drop);
    snmp_inc_ipinhdrerrors();
    return ERR_OK;
  }
#endif

  /* 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, iphdr_len);

  /* copy IP addresses to aligned ip_addr_t */
  ip_addr_copy(current_iphdr_dest, iphdr->dest);
  ip_addr_copy(current_iphdr_src, iphdr->src);

  /* match packet against an interface, i.e. is this packet for us? */
#if LWIP_IGMP
  if (ip_addr_ismulticast(&current_iphdr_dest)) {
    if ((inp->flags & NETIF_FLAG_IGMP) && (igmp_lookfor_group(inp, &current_iphdr_dest))) {
      netif = inp;
    } else {
      netif = NULL;
    }
  } else
#endif /* LWIP_IGMP */
  {
    /* start trying with inp. if that's not acceptable, start walking the
       list of configured netifs.
       'first' is used as a boolean to mark whether we started walking the list */
    int first = 1;
    netif = inp;
    do {
      LWIP_DEBUGF(IP_DEBUG, ("ip_input: iphdr->dest 0x%"X32_F" netif->ip_addr 0x%"X32_F" (0x%"X32_F", 0x%"X32_F", 0x%"X32_F")\n",
          ip4_addr_get_u32(&iphdr->dest), ip4_addr_get_u32(&netif->ip_addr),
          ip4_addr_get_u32(&iphdr->dest) & ip4_addr_get_u32(&netif->netmask),
          ip4_addr_get_u32(&netif->ip_addr) & ip4_addr_get_u32(&netif->netmask),
          ip4_addr_get_u32(&iphdr->dest) & ~ip4_addr_get_u32(&netif->netmask)));

      /* interface is up and configured? */
      if ((netif_is_up(netif)) && (!ip_addr_isany(&(netif->ip_addr)))) {
        /* unicast to this interface address? */
        if (ip_addr_cmp(&current_iphdr_dest, &(netif->ip_addr)) ||
            /* or broadcast on this interface network address? */
            ip_addr_isbroadcast(&current_iphdr_dest, netif)) {
          LWIP_DEBUGF(IP_DEBUG, ("ip_input: packet accepted on interface %c%c\n",
              netif->name[0], netif->name[1]));
          /* break out of for loop */
          break;
        }
#if LWIP_AUTOIP
        /* connections to link-local addresses must persist after changing
           the netif's address (RFC3927 ch. 1.9) */
        if ((netif->autoip != NULL) &&
            ip_addr_cmp(&current_iphdr_dest, &(netif->autoip->llipaddr))) {
          LWIP_DEBUGF(IP_DEBUG, ("ip_input: LLA packet accepted on interface %c%c\n",
              netif->name[0], netif->name[1]));
          /* break out of for loop */
          break;
        }
#endif /* LWIP_AUTOIP */
      }
      if (first) {
        first = 0;
        netif = netif_list;
      } else {
        netif = netif->next;
      }
      if (netif == inp) {
        netif = netif->next;
      }
    } while(netif != NULL);
  }

#if IP_ACCEPT_LINK_LAYER_ADDRESSING
  /* Pass DHCP messages regardless of destination address. DHCP traffic is addressed
   * using link layer addressing (such as Ethernet MAC) so we must not filter on IP.
   * According to RFC 1542 section 3.1.1, referred by RFC 2131).
   *
   * If you want to accept private broadcast communication while a netif is down,
   * define LWIP_IP_ACCEPT_UDP_PORT(dst_port), e.g.:
   *
   * #define LWIP_IP_ACCEPT_UDP_PORT(dst_port) ((dst_port) == PP_NTOHS(12345))
   */
  if (netif == NULL) {
    /* remote port is DHCP server? */
    if (IPH_PROTO(iphdr) == IP_PROTO_UDP) {
      struct udp_hdr *udphdr = (struct udp_hdr *)((u8_t *)iphdr + iphdr_hlen);
      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: UDP packet to DHCP client port %"U16_F"\n",
        ntohs(udphdr->dest)));
      if (IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(udphdr->dest)) {
        LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: DHCP packet accepted.\n"));
        netif = inp;
        check_ip_src = 0;
      }
    }
  }
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */

  /* broadcast or multicast packet source address? Compliant with RFC 1122: 3.2.1.3 */
#if IP_ACCEPT_LINK_LAYER_ADDRESSING
  /* DHCP servers need 0.0.0.0 to be allowed as source address (RFC 1.1.2.2: 3.2.1.3/a) */
  if (check_ip_src && !ip_addr_isany(&current_iphdr_src))
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
  {  if ((ip_addr_isbroadcast(&current_iphdr_src, inp)) ||
         (ip_addr_ismulticast(&current_iphdr_src))) {
      /* packet source is not valid */
      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING, ("ip_input: packet source is not valid.\n"));
      /* free (drop) packet pbufs */
      pbuf_free(p);
      IP_STATS_INC(ip.drop);
      snmp_inc_ipinaddrerrors();
      snmp_inc_ipindiscards();
      return ERR_OK;
    }
  }

  /* packet not for us? */
  if (netif == NULL) {
    /* packet not for us, route or discard */
    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: packet not for us.\n"));
#if IP_FORWARD
    /* non-broadcast packet? */
    if (!ip_addr_isbroadcast(&current_iphdr_dest, inp)) {
      /* try to forward IP packet on (other) interfaces */
      ip_forward(p, iphdr, inp);
    } else
#endif /* IP_FORWARD */
    {
      snmp_inc_ipinaddrerrors();
      snmp_inc_ipindiscards();
    }
    pbuf_free(p);
    return ERR_OK;
  }
  /* packet consists of multiple fragments? */
  if ((IPH_OFFSET(iphdr) & PP_HTONS(IP_OFFMASK | IP_MF)) != 0) {
#if IP_REASSEMBLY /* packet fragment reassembly code present? */
    LWIP_DEBUGF(IP_DEBUG, ("IP packet is a fragment (id=0x%04"X16_F" tot_len=%"U16_F" len=%"U16_F" MF=%"U16_F" offset=%"U16_F"), calling ip_reass()\n",
      ntohs(IPH_ID(iphdr)), p->tot_len, ntohs(IPH_LEN(iphdr)), !!(IPH_OFFSET(iphdr) & PP_HTONS(IP_MF)), (ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK)*8));
    /* reassemble the packet*/
    p = ip_reass(p);
    /* packet not fully reassembled yet? */
    if (p == NULL) {
      return ERR_OK;
    }
    iphdr = (struct ip_hdr *)p->payload;
#else /* IP_REASSEMBLY == 0, no packet fragment reassembly code present */
    pbuf_free(p);
    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since it was fragmented (0x%"X16_F") (while IP_REASSEMBLY == 0).\n",
      ntohs(IPH_OFFSET(iphdr))));
    IP_STATS_INC(ip.opterr);
    IP_STATS_INC(ip.drop);
    /* unsupported protocol feature */
    snmp_inc_ipinunknownprotos();
    return ERR_OK;
#endif /* IP_REASSEMBLY */
  }

#if IP_OPTIONS_ALLOWED == 0 /* no support for IP options in the IP header? */

#if LWIP_IGMP
  /* there is an extra "router alert" option in IGMP messages which we allow for but do not police */
  if((iphdr_hlen > IP_HLEN) &&  (IPH_PROTO(iphdr) != IP_PROTO_IGMP)) {
#else
  if (iphdr_hlen > IP_HLEN) {
#endif /* LWIP_IGMP */
    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since there were IP options (while IP_OPTIONS_ALLOWED == 0).\n"));
    pbuf_free(p);
    IP_STATS_INC(ip.opterr);
    IP_STATS_INC(ip.drop);
    /* unsupported protocol feature */
    snmp_inc_ipinunknownprotos();
    return ERR_OK;
  }
#endif /* IP_OPTIONS_ALLOWED == 0 */

  /* send to upper layers */
  LWIP_DEBUGF(IP_DEBUG, ("ip_input: \n"));
  ip_debug_print(p);
  LWIP_DEBUGF(IP_DEBUG, ("ip_input: p->len %"U16_F" p->tot_len %"U16_F"\n", p->len, p->tot_len));

  current_netif = inp;
  current_header = iphdr;

#if LWIP_RAW
  /* raw input did not eat the packet? */
  if (raw_input(p, inp) == 0)
#endif /* LWIP_RAW */
  {

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

      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("Unsupported transport protocol %"U16_F"\n", IPH_PROTO(iphdr)));

      IP_STATS_INC(ip.proterr);
      IP_STATS_INC(ip.drop);
      snmp_inc_ipinunknownprotos();
    }
  }

  current_netif = NULL;
  current_header = NULL;
  ip_addr_set_any(&current_iphdr_src);
  ip_addr_set_any(&current_iphdr_dest);

  return ERR_OK;
}

/**
 * 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.
 * If the destination IP address is IP_HDRINCL, p is assumed to already
 * include an IP header and p->payload points to it instead of the data.
 *
 * @param p the packet to send (p->payload points to the data, e.g. next
            protocol header; if dest == IP_HDRINCL, p already includes an IP
            header and p->payload points to that IP header)
 * @param src the source IP address to send from (if src == IP_ADDR_ANY, the
 *         IP  address of the netif used to send is used as source address)
 * @param dest the destination IP address to send the packet to
 * @param ttl the TTL value to be set in the IP header
 * @param tos the TOS value to be set in the IP header
 * @param proto the PROTOCOL to be set in the IP header
 * @param netif the netif on which to send this packet
 * @return ERR_OK if the packet was sent OK
 *         ERR_BUF if p doesn't have enough space for IP/LINK headers
 *         returns errors returned by netif->output
 *
 * @note ip_id: RFC791 "some host may be able to simply use
 *  unique identifiers independent of destination"
 */
err_t
ip_output_if(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,