/* @file * * This is the IP layer implementation for incoming and outgoing IP traffic. *  * @see ip_frag.c * *//* * Copyright (c) 2001-2004 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> * */#include "lwip/opt.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/raw.h"#include "lwip/udp.h"#include "lwip/tcp.h"#include "lwip/stats.h"#include "arch/perf.h"#include "lwip/snmp.h"#if LWIP_DHCP#  include "lwip/dhcp.h"#endif /* LWIP_DHCP *//** * Initializes the IP layer. */voidip_init(void){  /* no initializations as of yet */}/** * 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;  /* iterate through netifs */  for(netif = netif_list; netif != NULL; netif = netif->next) {    /* network mask matches? */    if (ip_addr_netcmp(dest, &(netif->ip_addr), &(netif->netmask))) {      /* return netif on which to forward IP packet */      return netif;    }  }  /* no matching netif found, use default netif */  return netif_default;}#if 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 struct netif *ip_forward(struct pbuf *p, struct ip_hdr *iphdr, struct netif *inp){  struct netif *netif;  PERF_START;  /* Find network interface where to forward this IP packet to. */  netif = ip_route((struct ip_addr *)&(iphdr->dest));  if (netif == NULL) {    LWIP_DEBUGF(IP_DEBUG, ("ip_forward: no forwarding route for 0x%"X32_F" found\n",                      iphdr->dest.addr));    snmp_inc_ipnoroutes();    return (struct netif *)NULL;  }  /* Do not forward packets onto the same network interface on which   * they arrived. */  if (netif == inp) {    LWIP_DEBUGF(IP_DEBUG, ("ip_forward: not bouncing packets back on incoming interface.\n"));    snmp_inc_ipnoroutes();    return (struct netif *)NULL;  }  /* decrement TTL */  IPH_TTL_SET(iphdr, IPH_TTL(iphdr) - 1);  /* send ICMP if TTL == 0 */  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);      snmp_inc_icmpouttimeexcds();    }    return (struct netif *)NULL;  }  /* Incrementally update 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));  }  LWIP_DEBUGF(IP_DEBUG, ("ip_forward: forwarding packet to 0x%"X32_F"\n",                    iphdr->dest.addr));  IP_STATS_INC(ip.fw);  IP_STATS_INC(ip.xmit);    snmp_inc_ipforwdatagrams();  PERF_STOP("ip_forward");  /* transmit pbuf on chosen interface */  netif->output(netif, p, (struct ip_addr *)&(iphdr->dest));  return netif;}#endif /* IP_FORWARD *//** * 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_tip_input(struct pbuf *p, struct netif *inp) {  struct ip_hdr *iphdr;  struct netif *netif;  u16_t iphdrlen;  IP_STATS_INC(ip.recv);  snmp_inc_ipinreceives();  /* identify the IP header */  iphdr = p->payload;  if (IPH_V(iphdr) != 4) {    ip_debug_print(p);    pbuf_free(p);    IP_STATS_INC(ip.err);    IP_STATS_INC(ip.drop);    snmp_inc_ipunknownprotos();    return ERR_OK;  }  /* obtain IP header length in number of 32-bit words */  iphdrlen = IPH_HL(iphdr);  /* calculate IP header length in bytes */  iphdrlen *= 4;  /* header length exceeds first pbuf length? */  if (iphdrlen > p->len) {    LWIP_DEBUGF(IP_DEBUG | 2, ("IP header (len %"U16_F") does not fit in first pbuf (len %"U16_F"), IP packet droppped.\n",      iphdrlen, p->len));    /* free (drop) packet pbufs */    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, iphdrlen) != 0) {    ip_debug_print(p);    pbuf_free(p);    IP_STATS_INC(ip.chkerr);    IP_STATS_INC(ip.drop);    snmp_inc_ipindiscards();    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, ntohs(IPH_LEN(iphdr)));  /* match packet against an interface, i.e. is this packet for us? */  for (netif = netif_list; netif != NULL; netif = netif->next) {    /* 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(&(iphdr->dest), &(netif->ip_addr)) ||         /* or broadcast on this interface network address? */         ip_addr_isbroadcast(&(iphdr->dest), netif)) {                 /* break out of for loop */        break;      }    }  }  /* packet not for us? */  if (netif == NULL) {    /* packet not for us, route or discard */#if IP_FORWARD    /* non-broadcast packet? */    if (!ip_addr_isbroadcast(&(iphdr->dest), inp)) {      /* try to forward IP packet on (other) interfaces */      ip_forward(p, iphdr, inp);    }    else#endif /* IP_FORWARD */    {      snmp_inc_ipindiscards();    }    pbuf_free(p);    return ERR_OK;  }  /* packet consists of multiple fragments? */  if ((IPH_OFFSET(iphdr) & htons(IP_OFFMASK | IP_MF)) != 0) {#if IP_REASSEMBLY /* packet fragment reassembly code present? */    /* reassemble the packet*/    p = ip_reass(p);    /* packet not fully reassembled yet? */    if (p == NULL) {      return ERR_OK;    }    iphdr = p->payload;#else /* IP_REASSEMBLY == 0, no packet fragment reassembly code present */    pbuf_free(p);    IP_STATS_INC(ip.opterr);    IP_STATS_INC(ip.drop);    snmp_inc_ipunknownprotos();    return ERR_OK;#endif /* IP_REASSEMBLY */  }#if IP_OPTIONS == 0 /* no support for IP options in the IP header? */  if (iphdrlen > IP_HLEN) {    pbuf_free(p);    IP_STATS_INC(ip.opterr);    IP_STATS_INC(ip.drop);    snmp_inc_ipunknownprotos();    return ERR_OK;  }#endif /* IP_OPTIONS == 0 */  /* send to upper layers */  ip_debug_print(p);#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:  case IP_PROTO_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 */  case IP_PROTO_ICMP:    snmp_inc_ipindelivers();    icmp_input(p, inp);    break;  default:    /* send ICMP destination protocol unreachable unless is was a broadcast */    if (!ip_addr_isbroadcast(&(iphdr->dest), inp) &&        !ip_addr_ismulticast(&(iphdr->dest))) {      p->payload = iphdr;      icmp_dest_unreach(p, ICMP_DUR_PROTO);    }    pbuf_free(p);    IP_STATS_INC(ip.proterr);    IP_STATS_INC(ip.drop);    snmp_inc_ipunknownprotos();  }#if LWIP_RAW  } /* LWIP_RAW */#endif  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. */err_tip_output_if(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,             u8_t ttl, u8_t tos,             u8_t proto, struct netif *netif){  struct ip_hdr *iphdr;  u16_t ip_id = 0;  snmp_inc_ipoutrequests();  if (dest != IP_HDRINCL) {    if (pbuf_header(p, IP_HLEN)) {      LWIP_DEBUGF(IP_DEBUG | 2, ("ip_output: not enough room for IP header in pbuf\n"));      IP_STATS_INC(ip.err);      snmp_inc_ipoutdiscards();      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, tos);    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);#if CHECKSUM_GEN_IP    IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));#endif  } else {    iphdr = p->payload;    dest = &(iphdr->dest);  }#if IP_FRAG  /* don't fragment if interface has mtu set to 0 [loopif] */  if (netif->mtu && (p->tot_len > netif->mtu))    return ip_frag(p,netif,dest);#endif  IP_STATS_INC(ip.xmit);  LWIP_DEBUGF(IP_DEBUG, ("ip_output_if: %c%c%"U16_F"\n", netif->name[0], netif->name[1], netif->num));  ip_debug_print(p);  LWIP_DEBUGF(IP_DEBUG, ("netif->output()"));  return netif->output(netif, p, dest);}/** * Simple interface to ip_output_if. It finds the outgoing network * interface and calls upon ip_output_if to do the actual work. */err_tip_output(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,          u8_t ttl, u8_t tos, u8_t proto){  struct netif *netif;  if ((netif = ip_route(dest)) == NULL) {    LWIP_DEBUGF(IP_DEBUG | 2, ("ip_output: No route to 0x%"X32_F"\n", dest->addr));    IP_STATS_INC(ip.rterr);    snmp_inc_ipoutdiscards();    return ERR_RTE;  }  return ip_output_if(p, src, dest, ttl, tos, proto, netif);}#if IP_DEBUGvoidip_debug_print(struct pbuf *p){  struct ip_hdr *iphdr = p->payload;  u8_t *payload;  payload = (u8_t *)iphdr + IP_HLEN;  LWIP_DEBUGF(IP_DEBUG, ("IP header:\n"));  LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));  LWIP_DEBUGF(IP_DEBUG, ("|%2"S16_F" |%2"S16_F" |  0x%02"X16_F" |     %5"U16_F"     | (v, hl, tos, len)\n",                    IPH_V(iphdr),                    IPH_HL(iphdr),                    IPH_TOS(iphdr),                    ntohs(IPH_LEN(iphdr))));  LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));  LWIP_DEBUGF(IP_DEBUG, ("|    %5"U16_F"      |%"U16_F"%"U16_F"%"U16_F"|    %4"U16_F"   | (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));  LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));  LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |    0x%04"X16_F"     | (ttl, proto, chksum)\n",                    IPH_TTL(iphdr),                    IPH_PROTO(iphdr),                    ntohs(IPH_CHKSUM(iphdr))));  LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));  LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  | (src)\n",                    ip4_addr1(&iphdr->src),                    ip4_addr2(&iphdr->src),                    ip4_addr3(&iphdr->src),                    ip4_addr4(&iphdr->src)));  LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));  LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  | (dest)\n",                    ip4_addr1(&iphdr->dest),                    ip4_addr2(&iphdr->dest),                    ip4_addr3(&iphdr->dest),                    ip4_addr4(&iphdr->dest)));  LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));}#endif /* IP_DEBUG */