ip.c

00001 /**
00002  * @file
00003  * This is the IPv4 layer implementation for incoming and outgoing IP traffic.
00004  *
00005  * @see ip_frag.c
00006  *
00007  */
00008 
00009 /*
00010  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
00011  * All rights reserved.
00012  *
00013  * Redistribution and use in source and binary forms, with or without modification,
00014  * are permitted provided that the following conditions are met:
00015  *
00016  * 1. Redistributions of source code must retain the above copyright notice,
00017  *    this list of conditions and the following disclaimer.
00018  * 2. Redistributions in binary form must reproduce the above copyright notice,
00019  *    this list of conditions and the following disclaimer in the documentation
00020  *    and/or other materials provided with the distribution.
00021  * 3. The name of the author may not be used to endorse or promote products
00022  *    derived from this software without specific prior written permission.
00023  *
00024  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
00025  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
00026  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
00027  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00028  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
00029  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00030  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
00031  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
00032  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
00033  * OF SUCH DAMAGE.
00034  *
00035  * This file is part of the lwIP TCP/IP stack.
00036  *
00037  * Author: Adam Dunkels <adam@sics.se>
00038  *
00039  */
00040 
00041 #include "lwip/opt.h"
00042 #include "lwip/ip.h"
00043 #include "lwip/def.h"
00044 #include "lwip/mem.h"
00045 #include "lwip/ip_frag.h"
00046 #include "lwip/inet_chksum.h"
00047 #include "lwip/netif.h"
00048 #include "lwip/icmp.h"
00049 #include "lwip/igmp.h"
00050 #include "lwip/raw.h"
00051 #include "lwip/udp.h"
00052 #include "lwip/tcp_impl.h"
00053 #include "lwip/snmp.h"
00054 #include "lwip/dhcp.h "
00055 #include "lwip/autoip.h"
00056 #include "lwip/stats.h"
00057 #include "arch/perf.h"
00058 
00059 #include <string.h>
00060 
00061 /** Set this to 0 in the rare case of wanting to call an extra function to
00062  * generate the IP checksum (in contrast to calculating it on-the-fly). */
00063 #ifndef LWIP_INLINE_IP_CHKSUM
00064 #define LWIP_INLINE_IP_CHKSUM   1
00065 #endif
00066 #if LWIP_INLINE_IP_CHKSUM && CHECKSUM_GEN_IP
00067 #define CHECKSUM_GEN_IP_INLINE  1
00068 #else
00069 #define CHECKSUM_GEN_IP_INLINE  0
00070 #endif
00071 
00072 #if LWIP_DHCP || defined(LWIP_IP_ACCEPT_UDP_PORT)
00073 #define IP_ACCEPT_LINK_LAYER_ADDRESSING 1
00074 
00075 /** Some defines for DHCP to let link-layer-addressed packets through while the
00076  * netif is down.
00077  * To use this in your own application/protocol, define LWIP_IP_ACCEPT_UDP_PORT
00078  * to return 1 if the port is accepted and 0 if the port is not accepted.
00079  */
00080 #if LWIP_DHCP && defined(LWIP_IP_ACCEPT_UDP_PORT)
00081 /* accept DHCP client port and custom port */
00082 #define IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(port) (((port) == PP_NTOHS(DHCP_CLIENT_PORT)) \
00083          || (LWIP_IP_ACCEPT_UDP_PORT(port)))
00084 #elif defined(LWIP_IP_ACCEPT_UDP_PORT) /* LWIP_DHCP && defined(LWIP_IP_ACCEPT_UDP_PORT) */
00085 /* accept custom port only */
00086 #define IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(port) (LWIP_IP_ACCEPT_UDP_PORT(port))
00087 #else /* LWIP_DHCP && defined(LWIP_IP_ACCEPT_UDP_PORT) */
00088 /* accept DHCP client port only */
00089 #define IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(port) ((port) == PP_NTOHS(DHCP_CLIENT_PORT))
00090 #endif /* LWIP_DHCP && defined(LWIP_IP_ACCEPT_UDP_PORT) */
00091 
00092 #else /* LWIP_DHCP */
00093 #define IP_ACCEPT_LINK_LAYER_ADDRESSING 0
00094 #endif /* LWIP_DHCP */
00095 
00096 /**
00097  * The interface that provided the packet for the current callback
00098  * invocation.
00099  */
00100 struct netif *current_netif;
00101 
00102 /**
00103  * Header of the input packet currently being processed.
00104  */
00105 const struct ip_hdr *current_header;
00106 /** Source IP address of current_header */
00107 ip_addr_t current_iphdr_src;
00108 /** Destination IP address of current_header */
00109 ip_addr_t current_iphdr_dest;
00110 
00111 /** The IP header ID of the next outgoing IP packet */
00112 static u16_t ip_id;
00113 
00114 /**
00115  * Finds the appropriate network interface for a given IP address. It
00116  * searches the list of network interfaces linearly. A match is found
00117  * if the masked IP address of the network interface equals the masked
00118  * IP address given to the function.
00119  *
00120  * @param dest the destination IP address for which to find the route
00121  * @return the netif on which to send to reach dest
00122  */
00123 struct netif *
00124 ip_route(ip_addr_t *dest)
00125 {
00126   struct netif *netif;
00127 
00128 #ifdef LWIP_HOOK_IP4_ROUTE
00129   netif = LWIP_HOOK_IP4_ROUTE(dest);
00130   if (netif != NULL) {
00131     return netif;
00132   }
00133 #endif
00134 
00135   /* iterate through netifs */
00136   for (netif = netif_list; netif != NULL; netif = netif->next) {
00137     /* network mask matches? */
00138     if (netif_is_up(netif)) {
00139       if (ip_addr_netcmp(dest, &(netif->ip_addr), &(netif->netmask))) {
00140         /* return netif on which to forward IP packet */
00141         return netif;
00142       }
00143     }
00144   }
00145   if ((netif_default == NULL) || (!netif_is_up(netif_default))) {
00146     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_route: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00147       ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
00148     IP_STATS_INC(ip.rterr);
00149     snmp_inc_ipoutnoroutes();
00150     return NULL;
00151   }
00152   /* no matching netif found, use default netif */
00153   return netif_default;
00154 }
00155 
00156 #if IP_FORWARD
00157 /**
00158  * Determine whether an IP address is in a reserved set of addresses
00159  * that may not be forwarded, or whether datagrams to that destination
00160  * may be forwarded.
00161  * @param p the packet to forward
00162  * @param dest the destination IP address
00163  * @return 1: can forward 0: discard
00164  */
00165 static int
00166 ip_canforward(struct pbuf *p)
00167 {
00168   u32_t addr = ip4_addr_get_u32(ip_current_dest_addr());
00169 
00170   if (p->flags & PBUF_FLAG_LLBCAST) {
00171     /* don't route link-layer broadcasts */
00172     return 0;
00173   }
00174   if ((p->flags & PBUF_FLAG_LLMCAST) && !IP_MULTICAST(addr)) {
00175     /* don't route link-layer multicasts unless the destination address is an IP
00176        multicast address */
00177     return 0;
00178   }
00179   if (IP_EXPERIMENTAL(addr)) {
00180     return 0;
00181   }
00182   if (IP_CLASSA(addr)) {
00183     u32_t net = addr & IP_CLASSA_NET;
00184     if ((net == 0) || (net == (IP_LOOPBACKNET << IP_CLASSA_NSHIFT))) {
00185       /* don't route loopback packets */
00186       return 0;
00187     }
00188   }
00189   return 1;
00190 }
00191 
00192 /**
00193  * Forwards an IP packet. It finds an appropriate route for the
00194  * packet, decrements the TTL value of the packet, adjusts the
00195  * checksum and outputs the packet on the appropriate interface.
00196  *
00197  * @param p the packet to forward (p->payload points to IP header)
00198  * @param iphdr the IP header of the input packet
00199  * @param inp the netif on which this packet was received
00200  */
00201 static void
00202 ip_forward(struct pbuf *p, struct ip_hdr *iphdr, struct netif *inp)
00203 {
00204   struct netif *netif;
00205 
00206   PERF_START;
00207 
00208   if (!ip_canforward(p)) {
00209     goto return_noroute;
00210   }
00211 
00212   /* RFC3927 2.7: do not forward link-local addresses */
00213   if (ip_addr_islinklocal(&current_iphdr_dest)) {
00214     LWIP_DEBUGF(IP_DEBUG, ("ip_forward: not forwarding LLA %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00215       ip4_addr1_16(&current_iphdr_dest), ip4_addr2_16(&current_iphdr_dest),
00216       ip4_addr3_16(&current_iphdr_dest), ip4_addr4_16(&current_iphdr_dest)));
00217     goto return_noroute;
00218   }
00219 
00220   /* Find network interface where to forward this IP packet to. */
00221   netif = ip_route(&current_iphdr_dest);
00222   if (netif == NULL) {
00223     LWIP_DEBUGF(IP_DEBUG, ("ip_forward: no forwarding route for %"U16_F".%"U16_F".%"U16_F".%"U16_F" found\n",
00224       ip4_addr1_16(&current_iphdr_dest), ip4_addr2_16(&current_iphdr_dest),
00225       ip4_addr3_16(&current_iphdr_dest), ip4_addr4_16(&current_iphdr_dest)));
00226     /* @todo: send ICMP_DUR_NET? */
00227     goto return_noroute;
00228   }
00229 #if !IP_FORWARD_ALLOW_TX_ON_RX_NETIF
00230   /* Do not forward packets onto the same network interface on which
00231    * they arrived. */
00232   if (netif == inp) {
00233     LWIP_DEBUGF(IP_DEBUG, ("ip_forward: not bouncing packets back on incoming interface.\n"));
00234     goto return_noroute;
00235   }
00236 #endif /* IP_FORWARD_ALLOW_TX_ON_RX_NETIF */
00237 
00238   /* decrement TTL */
00239   IPH_TTL_SET(iphdr, IPH_TTL(iphdr) - 1);
00240   /* send ICMP if TTL == 0 */
00241   if (IPH_TTL(iphdr) == 0) {
00242     snmp_inc_ipinhdrerrors();
00243 #if LWIP_ICMP
00244     /* Don't send ICMP messages in response to ICMP messages */
00245     if (IPH_PROTO(iphdr) != IP_PROTO_ICMP) {
00246       icmp_time_exceeded(p, ICMP_TE_TTL);
00247     }
00248 #endif /* LWIP_ICMP */
00249     return;
00250   }
00251 
00252   /* Incrementally update the IP checksum. */
00253   if (IPH_CHKSUM(iphdr) >= PP_HTONS(0xffffU - 0x100)) {
00254     IPH_CHKSUM_SET(iphdr, IPH_CHKSUM(iphdr) + PP_HTONS(0x100) + 1);
00255   } else {
00256     IPH_CHKSUM_SET(iphdr, IPH_CHKSUM(iphdr) + PP_HTONS(0x100));
00257   }
00258 
00259   LWIP_DEBUGF(IP_DEBUG, ("ip_forward: forwarding packet to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00260     ip4_addr1_16(&current_iphdr_dest), ip4_addr2_16(&current_iphdr_dest),
00261     ip4_addr3_16(&current_iphdr_dest), ip4_addr4_16(&current_iphdr_dest)));
00262 
00263   IP_STATS_INC(ip.fw);
00264   IP_STATS_INC(ip.xmit);
00265   snmp_inc_ipforwdatagrams();
00266 
00267   PERF_STOP("ip_forward");
00268   /* don't fragment if interface has mtu set to 0 [loopif] */
00269   if (netif->mtu && (p->tot_len > netif->mtu)) {
00270     if ((IPH_OFFSET(iphdr) & PP_NTOHS(IP_DF)) == 0) {
00271 #if IP_FRAG
00272       ip_frag(p, netif, ip_current_dest_addr());
00273 #else /* IP_FRAG */
00274       /* @todo: send ICMP Destination Unreacheable code 13 "Communication administratively prohibited"? */
00275 #endif /* IP_FRAG */
00276     } else {
00277       /* send ICMP Destination Unreacheable code 4: "Fragmentation Needed and DF Set" */
00278       icmp_dest_unreach(p, ICMP_DUR_FRAG);
00279     }
00280     return;
00281   }
00282   /* transmit pbuf on chosen interface */
00283   netif->output(netif, p, &current_iphdr_dest);
00284   return;
00285 return_noroute:
00286   snmp_inc_ipoutnoroutes();
00287 }
00288 #endif /* IP_FORWARD */
00289 
00290 /**
00291  * This function is called by the network interface device driver when
00292  * an IP packet is received. The function does the basic checks of the
00293  * IP header such as packet size being at least larger than the header
00294  * size etc. If the packet was not destined for us, the packet is
00295  * forwarded (using ip_forward). The IP checksum is always checked.
00296  *
00297  * Finally, the packet is sent to the upper layer protocol input function.
00298  *
00299  * @param p the received IP packet (p->payload points to IP header)
00300  * @param inp the netif on which this packet was received
00301  * @return ERR_OK if the packet was processed (could return ERR_* if it wasn't
00302  *         processed, but currently always returns ERR_OK)
00303  */
00304 err_t
00305 ip_input(struct pbuf *p, struct netif *inp)
00306 {
00307   struct ip_hdr *iphdr;
00308   struct netif *netif;
00309   u16_t iphdr_hlen;
00310   u16_t iphdr_len;
00311 #if IP_ACCEPT_LINK_LAYER_ADDRESSING
00312   int check_ip_src=1;
00313 #endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
00314 
00315   IP_STATS_INC(ip.recv);
00316   snmp_inc_ipinreceives();
00317 
00318   /* identify the IP header */
00319   iphdr = (struct ip_hdr *)p->payload;
00320   if (IPH_V(iphdr) != 4) {
00321     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_WARNING, ("IP packet dropped due to bad version number %"U16_F"\n", IPH_V(iphdr)));
00322     ip_debug_print(p);
00323     pbuf_free(p);
00324     IP_STATS_INC(ip.err);
00325     IP_STATS_INC(ip.drop);
00326     snmp_inc_ipinhdrerrors();
00327     return ERR_OK;
00328   }
00329 
00330 #ifdef LWIP_HOOK_IP4_INPUT
00331   if (LWIP_HOOK_IP4_INPUT(p, inp)) {
00332     /* the packet has been eaten */
00333     return ERR_OK;
00334   }
00335 #endif
00336 
00337   /* obtain IP header length in number of 32-bit words */
00338   iphdr_hlen = IPH_HL(iphdr);
00339   /* calculate IP header length in bytes */
00340   iphdr_hlen *= 4;
00341   /* obtain ip length in bytes */
00342   iphdr_len = ntohs(IPH_LEN(iphdr));
00343 
00344   /* header length exceeds first pbuf length, or ip length exceeds total pbuf length? */
00345   if ((iphdr_hlen > p->len) || (iphdr_len > p->tot_len)) {
00346     if (iphdr_hlen > p->len) {
00347       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00348         ("IP header (len %"U16_F") does not fit in first pbuf (len %"U16_F"), IP packet dropped.\n",
00349         iphdr_hlen, p->len));
00350     }
00351     if (iphdr_len > p->tot_len) {
00352       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00353         ("IP (len %"U16_F") is longer than pbuf (len %"U16_F"), IP packet dropped.\n",
00354         iphdr_len, p->tot_len));
00355     }
00356     /* free (drop) packet pbufs */
00357     pbuf_free(p);
00358     IP_STATS_INC(ip.lenerr);
00359     IP_STATS_INC(ip.drop);
00360     snmp_inc_ipindiscards();
00361     return ERR_OK;
00362   }
00363 
00364   /* verify checksum */
00365 #if CHECKSUM_CHECK_IP
00366   if (inet_chksum(iphdr, iphdr_hlen) != 0) {
00367 
00368     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00369       ("Checksum (0x%"X16_F") failed, IP packet dropped.\n", inet_chksum(iphdr, iphdr_hlen)));
00370     ip_debug_print(p);
00371     pbuf_free(p);
00372     IP_STATS_INC(ip.chkerr);
00373     IP_STATS_INC(ip.drop);
00374     snmp_inc_ipinhdrerrors();
00375     return ERR_OK;
00376   }
00377 #endif
00378 
00379   /* Trim pbuf. This should have been done at the netif layer,
00380    * but we'll do it anyway just to be sure that its done. */
00381   pbuf_realloc(p, iphdr_len);
00382 
00383   /* copy IP addresses to aligned ip_addr_t */
00384   ip_addr_copy(current_iphdr_dest, iphdr->dest);
00385   ip_addr_copy(current_iphdr_src, iphdr->src);
00386 
00387   /* match packet against an interface, i.e. is this packet for us? */
00388 #if LWIP_IGMP
00389   if (ip_addr_ismulticast(&current_iphdr_dest)) {
00390     if ((inp->flags & NETIF_FLAG_IGMP) && (igmp_lookfor_group(inp, &current_iphdr_dest))) {
00391       netif = inp;
00392     } else {
00393       netif = NULL;
00394     }
00395   } else
00396 #endif /* LWIP_IGMP */
00397   {
00398     /* start trying with inp. if that's not acceptable, start walking the
00399        list of configured netifs.
00400        'first' is used as a boolean to mark whether we started walking the list */
00401     int first = 1;
00402     netif = inp;
00403     do {
00404       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",
00405           ip4_addr_get_u32(&iphdr->dest), ip4_addr_get_u32(&netif->ip_addr),
00406           ip4_addr_get_u32(&iphdr->dest) & ip4_addr_get_u32(&netif->netmask),
00407           ip4_addr_get_u32(&netif->ip_addr) & ip4_addr_get_u32(&netif->netmask),
00408           ip4_addr_get_u32(&iphdr->dest) & ~ip4_addr_get_u32(&netif->netmask)));
00409 
00410       /* interface is up and configured? */
00411       if ((netif_is_up(netif)) && (!ip_addr_isany(&(netif->ip_addr)))) {
00412         /* unicast to this interface address? */
00413         if (ip_addr_cmp(&current_iphdr_dest, &(netif->ip_addr)) ||
00414             /* or broadcast on this interface network address? */
00415             ip_addr_isbroadcast(&current_iphdr_dest, netif)) {
00416           LWIP_DEBUGF(IP_DEBUG, ("ip_input: packet accepted on interface %c%c\n",
00417               netif->name[0], netif->name[1]));
00418           /* break out of for loop */
00419           break;
00420         }
00421 #if LWIP_AUTOIP
00422         /* connections to link-local addresses must persist after changing
00423            the netif's address (RFC3927 ch. 1.9) */
00424         if ((netif->autoip != NULL) &&
00425             ip_addr_cmp(&current_iphdr_dest, &(netif->autoip->llipaddr))) {
00426           LWIP_DEBUGF(IP_DEBUG, ("ip_input: LLA packet accepted on interface %c%c\n",
00427               netif->name[0], netif->name[1]));
00428           /* break out of for loop */
00429           break;
00430         }
00431 #endif /* LWIP_AUTOIP */
00432       }
00433       if (first) {
00434         first = 0;
00435         netif = netif_list;
00436       } else {
00437         netif = netif->next;
00438       }
00439       if (netif == inp) {
00440         netif = netif->next;
00441       }
00442     } while(netif != NULL);
00443   }
00444 
00445 #if IP_ACCEPT_LINK_LAYER_ADDRESSING
00446   /* Pass DHCP messages regardless of destination address. DHCP traffic is addressed
00447    * using link layer addressing (such as Ethernet MAC) so we must not filter on IP.
00448    * According to RFC 1542 section 3.1.1, referred by RFC 2131).
00449    *
00450    * If you want to accept private broadcast communication while a netif is down,
00451    * define LWIP_IP_ACCEPT_UDP_PORT(dst_port), e.g.:
00452    *
00453    * #define LWIP_IP_ACCEPT_UDP_PORT(dst_port) ((dst_port) == PP_NTOHS(12345))
00454    */
00455   if (netif == NULL) {
00456     /* remote port is DHCP server? */
00457     if (IPH_PROTO(iphdr) == IP_PROTO_UDP) {
00458       struct udp_hdr *udphdr = (struct udp_hdr *)((u8_t *)iphdr + iphdr_hlen);
00459       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: UDP packet to DHCP client port %"U16_F"\n",
00460         ntohs(udphdr->dest)));
00461       if (IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(udphdr->dest)) {
00462         LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: DHCP packet accepted.\n"));
00463         netif = inp;
00464         check_ip_src = 0;
00465       }
00466     }
00467   }
00468 #endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
00469 
00470   /* broadcast or multicast packet source address? Compliant with RFC 1122: 3.2.1.3 */
00471 #if IP_ACCEPT_LINK_LAYER_ADDRESSING
00472   /* DHCP servers need 0.0.0.0 to be allowed as source address (RFC 1.1.2.2: 3.2.1.3/a) */
00473   if (check_ip_src && !ip_addr_isany(&current_iphdr_src))
00474 #endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
00475   {  if ((ip_addr_isbroadcast(&current_iphdr_src, inp)) ||
00476          (ip_addr_ismulticast(&current_iphdr_src))) {
00477       /* packet source is not valid */
00478       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING, ("ip_input: packet source is not valid.\n"));
00479       /* free (drop) packet pbufs */
00480       pbuf_free(p);
00481       IP_STATS_INC(ip.drop);
00482       snmp_inc_ipinaddrerrors();
00483       snmp_inc_ipindiscards();
00484       return ERR_OK;
00485     }
00486   }
00487 
00488   /* packet not for us? */
00489   if (netif == NULL) {
00490     /* packet not for us, route or discard */
00491     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: packet not for us.\n"));
00492 #if IP_FORWARD
00493     /* non-broadcast packet? */
00494     if (!ip_addr_isbroadcast(&current_iphdr_dest, inp)) {
00495       /* try to forward IP packet on (other) interfaces */
00496       ip_forward(p, iphdr, inp);
00497     } else
00498 #endif /* IP_FORWARD */
00499     {
00500       snmp_inc_ipinaddrerrors();
00501       snmp_inc_ipindiscards();
00502     }
00503     pbuf_free(p);
00504     return ERR_OK;
00505   }
00506   /* packet consists of multiple fragments? */
00507   if ((IPH_OFFSET(iphdr) & PP_HTONS(IP_OFFMASK | IP_MF)) != 0) {
00508 #if IP_REASSEMBLY /* packet fragment reassembly code present? */
00509     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",
00510       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));
00511     /* reassemble the packet*/
00512     p = ip_reass(p);
00513     /* packet not fully reassembled yet? */
00514     if (p == NULL) {
00515       return ERR_OK;
00516     }
00517     iphdr = (struct ip_hdr *)p->payload;
00518 #else /* IP_REASSEMBLY == 0, no packet fragment reassembly code present */
00519     pbuf_free(p);
00520     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since it was fragmented (0x%"X16_F") (while IP_REASSEMBLY == 0).\n",
00521       ntohs(IPH_OFFSET(iphdr))));
00522     IP_STATS_INC(ip.opterr);
00523     IP_STATS_INC(ip.drop);
00524     /* unsupported protocol feature */
00525     snmp_inc_ipinunknownprotos();
00526     return ERR_OK;
00527 #endif /* IP_REASSEMBLY */
00528   }
00529 
00530 #if IP_OPTIONS_ALLOWED == 0 /* no support for IP options in the IP header? */
00531 
00532 #if LWIP_IGMP
00533   /* there is an extra "router alert" option in IGMP messages which we allow for but do not police */
00534   if((iphdr_hlen > IP_HLEN) &&  (IPH_PROTO(iphdr) != IP_PROTO_IGMP)) {
00535 #else
00536   if (iphdr_hlen > IP_HLEN) {
00537 #endif /* LWIP_IGMP */
00538     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since there were IP options (while IP_OPTIONS_ALLOWED == 0).\n"));
00539     pbuf_free(p);
00540     IP_STATS_INC(ip.opterr);
00541     IP_STATS_INC(ip.drop);
00542     /* unsupported protocol feature */
00543     snmp_inc_ipinunknownprotos();
00544     return ERR_OK;
00545   }
00546 #endif /* IP_OPTIONS_ALLOWED == 0 */
00547 
00548   /* send to upper layers */
00549   LWIP_DEBUGF(IP_DEBUG, ("ip_input: \n"));
00550   ip_debug_print(p);
00551   LWIP_DEBUGF(IP_DEBUG, ("ip_input: p->len %"U16_F" p->tot_len %"U16_F"\n", p->len, p->tot_len));
00552 
00553   current_netif = inp;
00554   current_header = iphdr;
00555 
00556 #if LWIP_RAW
00557   /* raw input did not eat the packet? */
00558   if (raw_input(p, inp) == 0)
00559 #endif /* LWIP_RAW */
00560   {
00561     switch (IPH_PROTO(iphdr)) {
00562 #if LWIP_UDP
00563     case IP_PROTO_UDP:
00564 #if LWIP_UDPLITE
00565     case IP_PROTO_UDPLITE:
00566 #endif /* LWIP_UDPLITE */
00567       snmp_inc_ipindelivers();
00568       LWIP_DEBUGF(IP_DEBUG, ("udp_input: p 0x%x p->len %"U16_F" p->tot_len %"U16_F"\n",p->payload, p->len, p->tot_len));
00569       udp_input(p, inp);
00570       break;
00571 #endif /* LWIP_UDP */
00572 #if LWIP_TCP
00573     case IP_PROTO_TCP:
00574       snmp_inc_ipindelivers();
00575       LWIP_DEBUGF(IP_DEBUG, ("tcp_input_ip: p 0x%x p->len %"U16_F" p->tot_len %"U16_F"\n",p->payload, p->len, p->tot_len));
00576       tcp_input(p, inp);
00577       break;
00578 #endif /* LWIP_TCP */
00579 #if LWIP_ICMP
00580     case IP_PROTO_ICMP:
00581       snmp_inc_ipindelivers();
00582       LWIP_DEBUGF(IP_DEBUG, ("icmp_input: p 0x%x p->len %"U16_F" p->tot_len %"U16_F"\n",p->payload, p->len, p->tot_len));
00583       icmp_input(p, inp);
00584       break;
00585 #endif /* LWIP_ICMP */
00586 #if LWIP_IGMP
00587     case IP_PROTO_IGMP:
00588       LWIP_DEBUGF(IP_DEBUG, ("igmp_input: p 0x%x p->len %"U16_F" p->tot_len %"U16_F"\n",p->payload, p->len, p->tot_len));
00589       igmp_input(p, inp, &current_iphdr_dest);
00590       break;
00591 #endif /* LWIP_IGMP */
00592     default:
00593 #if LWIP_ICMP
00594       /* send ICMP destination protocol unreachable unless is was a broadcast */
00595       if (!ip_addr_isbroadcast(&current_iphdr_dest, inp) &&
00596           !ip_addr_ismulticast(&current_iphdr_dest)) {
00597         p->payload = iphdr;
00598         icmp_dest_unreach(p, ICMP_DUR_PROTO);
00599       }
00600 #endif /* LWIP_ICMP */
00601       pbuf_free(p);
00602 
00603       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("Unsupported transport protocol %"U16_F"\n", IPH_PROTO(iphdr)));
00604 
00605       IP_STATS_INC(ip.proterr);
00606       IP_STATS_INC(ip.drop);
00607       snmp_inc_ipinunknownprotos();
00608     }
00609   }
00610 
00611   current_netif = NULL;
00612   current_header = NULL;
00613   ip_addr_set_any(&current_iphdr_src);
00614   ip_addr_set_any(&current_iphdr_dest);
00615 
00616   return ERR_OK;
00617 }
00618 
00619 /**
00620  * Sends an IP packet on a network interface. This function constructs
00621  * the IP header and calculates the IP header checksum. If the source
00622  * IP address is NULL, the IP address of the outgoing network
00623  * interface is filled in as source address.
00624  * If the destination IP address is IP_HDRINCL, p is assumed to already
00625  * include an IP header and p->payload points to it instead of the data.
00626  *
00627  * @param p the packet to send (p->payload points to the data, e.g. next
00628             protocol header; if dest == IP_HDRINCL, p already includes an IP
00629             header and p->payload points to that IP header)
00630  * @param src the source IP address to send from (if src == IP_ADDR_ANY, the
00631  *         IP  address of the netif used to send is used as source address)
00632  * @param dest the destination IP address to send the packet to
00633  * @param ttl the TTL value to be set in the IP header
00634  * @param tos the TOS value to be set in the IP header
00635  * @param proto the PROTOCOL to be set in the IP header
00636  * @param netif the netif on which to send this packet
00637  * @return ERR_OK if the packet was sent OK
00638  *         ERR_BUF if p doesn't have enough space for IP/LINK headers
00639  *         returns errors returned by netif->output
00640  *
00641  * @note ip_id: RFC791 "some host may be able to simply use
00642  *  unique identifiers independent of destination"
00643  */
00644 err_t
00645 ip_output_if(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
00646              u8_t ttl, u8_t tos,
00647              u8_t proto, struct netif *netif)
00648 {
00649 #if IP_OPTIONS_SEND
00650   return ip_output_if_opt(p, src, dest, ttl, tos, proto, netif, NULL, 0);
00651 }
00652 
00653 /**
00654  * Same as ip_output_if() but with the possibility to include IP options:
00655  *
00656  * @ param ip_options pointer to the IP options, copied into the IP header
00657  * @ param optlen length of ip_options
00658  */
00659 err_t ip_output_if_opt(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
00660        u8_t ttl, u8_t tos, u8_t proto, struct netif *netif, void *ip_options,
00661        u16_t optlen)
00662 {
00663 #endif /* IP_OPTIONS_SEND */
00664   struct ip_hdr *iphdr;
00665   ip_addr_t dest_addr;
00666 #if CHECKSUM_GEN_IP_INLINE
00667   u32_t chk_sum = 0;
00668 #endif /* CHECKSUM_GEN_IP_INLINE */
00669 
00670   /* pbufs passed to IP must have a ref-count of 1 as their payload pointer
00671      gets altered as the packet is passed down the stack */
00672   LWIP_ASSERT("p->ref == 1", p->ref == 1);
00673 
00674   snmp_inc_ipoutrequests();
00675 
00676   /* Should the IP header be generated or is it already included in p? */
00677   if (dest != IP_HDRINCL) {
00678     u16_t ip_hlen = IP_HLEN;
00679 #if IP_OPTIONS_SEND
00680     u16_t optlen_aligned = 0;
00681     if (optlen != 0) {
00682 #if CHECKSUM_GEN_IP_INLINE
00683       int i;
00684 #endif /* CHECKSUM_GEN_IP_INLINE */
00685       /* round up to a multiple of 4 */
00686       optlen_aligned = ((optlen + 3) & ~3);
00687       ip_hlen += optlen_aligned;
00688       /* First write in the IP options */
00689       if (pbuf_header(p, optlen_aligned)) {
00690         LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_output_if_opt: not enough room for IP options in pbuf\n"));
00691         IP_STATS_INC(ip.err);
00692         snmp_inc_ipoutdiscards();
00693         return ERR_BUF;
00694       }
00695       MEMCPY(p->payload, ip_options, optlen);
00696       if (optlen < optlen_aligned) {
00697         /* zero the remaining bytes */
00698         memset(((char*)p->payload) + optlen, 0, optlen_aligned - optlen);
00699       }
00700 #if CHECKSUM_GEN_IP_INLINE
00701       for (i = 0; i < optlen_aligned/2; i++) {
00702         chk_sum += ((u16_t*)p->payload)[i];
00703       }
00704 #endif /* CHECKSUM_GEN_IP_INLINE */
00705     }
00706 #endif /* IP_OPTIONS_SEND */
00707     /* generate IP header */
00708     if (pbuf_header(p, IP_HLEN)) {
00709       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_output: not enough room for IP header in pbuf\n"));
00710 
00711       IP_STATS_INC(ip.err);
00712       snmp_inc_ipoutdiscards();
00713       return ERR_BUF;
00714     }
00715 
00716     iphdr = (struct ip_hdr *)p->payload;
00717     LWIP_ASSERT("check that first pbuf can hold struct ip_hdr",
00718                (p->len >= sizeof(struct ip_hdr)));
00719 
00720     IPH_TTL_SET(iphdr, ttl);
00721     IPH_PROTO_SET(iphdr, proto);
00722 #if CHECKSUM_GEN_IP_INLINE
00723     chk_sum += LWIP_MAKE_U16(proto, ttl);
00724 #endif /* CHECKSUM_GEN_IP_INLINE */
00725 
00726     /* dest cannot be NULL here */
00727     ip_addr_copy(iphdr->dest, *dest);
00728 #if CHECKSUM_GEN_IP_INLINE
00729     chk_sum += ip4_addr_get_u32(&iphdr->dest) & 0xFFFF;
00730     chk_sum += ip4_addr_get_u32(&iphdr->dest) >> 16;
00731 #endif /* CHECKSUM_GEN_IP_INLINE */
00732 
00733     IPH_VHL_SET(iphdr, 4, ip_hlen / 4);
00734     IPH_TOS_SET(iphdr, tos);
00735 #if CHECKSUM_GEN_IP_INLINE
00736     chk_sum += LWIP_MAKE_U16(tos, iphdr->_v_hl);
00737 #endif /* CHECKSUM_GEN_IP_INLINE */
00738     IPH_LEN_SET(iphdr, htons(p->tot_len));
00739 #if CHECKSUM_GEN_IP_INLINE
00740     chk_sum += iphdr->_len;
00741 #endif /* CHECKSUM_GEN_IP_INLINE */
00742     IPH_OFFSET_SET(iphdr, 0);
00743     IPH_ID_SET(iphdr, htons(ip_id));
00744 #if CHECKSUM_GEN_IP_INLINE
00745     chk_sum += iphdr->_id;
00746 #endif /* CHECKSUM_GEN_IP_INLINE */
00747     ++ip_id;
00748 
00749     if (ip_addr_isany(src)) {
00750       ip_addr_copy(iphdr->src, netif->ip_addr);
00751     } else {
00752       /* src cannot be NULL here */
00753       ip_addr_copy(iphdr->src, *src);
00754     }
00755 
00756 #if CHECKSUM_GEN_IP_INLINE
00757     chk_sum += ip4_addr_get_u32(&iphdr->src) & 0xFFFF;
00758     chk_sum += ip4_addr_get_u32(&iphdr->src) >> 16;
00759     chk_sum = (chk_sum >> 16) + (chk_sum & 0xFFFF);
00760     chk_sum = (chk_sum >> 16) + chk_sum;
00761     chk_sum = ~chk_sum;
00762     iphdr->_chksum = chk_sum; /* network order */
00763 #else /* CHECKSUM_GEN_IP_INLINE */
00764     IPH_CHKSUM_SET(iphdr, 0);
00765 #if CHECKSUM_GEN_IP
00766     IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, ip_hlen));
00767 #endif
00768 #endif /* CHECKSUM_GEN_IP_INLINE */
00769   } else {
00770     /* IP header already included in p */
00771     iphdr = (struct ip_hdr *)p->payload;
00772     ip_addr_copy(dest_addr, iphdr->dest);
00773     dest = &dest_addr;
00774   }
00775 
00776   IP_STATS_INC(ip.xmit);
00777 
00778   LWIP_DEBUGF(IP_DEBUG, ("ip_output_if: %c%c%"U16_F"\n", netif->name[0], netif->name[1], netif->num));
00779   ip_debug_print(p);
00780 
00781 #if ENABLE_LOOPBACK
00782   if (ip_addr_cmp(dest, &netif->ip_addr)) {
00783     /* Packet to self, enqueue it for loopback */
00784     LWIP_DEBUGF(IP_DEBUG, ("netif_loop_output()"));
00785     return netif_loop_output(netif, p, dest);
00786   }
00787 #if LWIP_IGMP
00788   if ((p->flags & PBUF_FLAG_MCASTLOOP) != 0) {
00789     netif_loop_output(netif, p, dest);
00790   }
00791 #endif /* LWIP_IGMP */
00792 #endif /* ENABLE_LOOPBACK */
00793 #if IP_FRAG
00794   /* don't fragment if interface has mtu set to 0 [loopif] */
00795   if (netif->mtu && (p->tot_len > netif->mtu)) {
00796     return ip_frag(p, netif, dest);
00797   }
00798 #endif /* IP_FRAG */
00799 
00800   LWIP_DEBUGF(IP_DEBUG, ("netif->output()"));
00801   return netif->output(netif, p, dest);
00802 }
00803 
00804 /**
00805  * Simple interface to ip_output_if. It finds the outgoing network
00806  * interface and calls upon ip_output_if to do the actual work.
00807  *
00808  * @param p the packet to send (p->payload points to the data, e.g. next
00809             protocol header; if dest == IP_HDRINCL, p already includes an IP
00810             header and p->payload points to that IP header)
00811  * @param src the source IP address to send from (if src == IP_ADDR_ANY, the
00812  *         IP  address of the netif used to send is used as source address)
00813  * @param dest the destination IP address to send the packet to
00814  * @param ttl the TTL value to be set in the IP header
00815  * @param tos the TOS value to be set in the IP header
00816  * @param proto the PROTOCOL to be set in the IP header
00817  *
00818  * @return ERR_RTE if no route is found
00819  *         see ip_output_if() for more return values
00820  */
00821 err_t
00822 ip_output(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
00823           u8_t ttl, u8_t tos, u8_t proto)
00824 {
00825   struct netif *netif;
00826 
00827   /* pbufs passed to IP must have a ref-count of 1 as their payload pointer
00828      gets altered as the packet is passed down the stack */
00829   LWIP_ASSERT("p->ref == 1", p->ref == 1);
00830 
00831   if ((netif = ip_route(dest)) == NULL) {
00832     LWIP_DEBUGF(IP_DEBUG, ("ip_output: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00833       ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
00834     IP_STATS_INC(ip.rterr);
00835     return ERR_RTE;
00836   }
00837 
00838   return ip_output_if(p, src, dest, ttl, tos, proto, netif);
00839 }
00840 
00841 #if LWIP_NETIF_HWADDRHINT
00842 /** Like ip_output, but takes and addr_hint pointer that is passed on to netif->addr_hint
00843  *  before calling ip_output_if.
00844  *
00845  * @param p the packet to send (p->payload points to the data, e.g. next
00846             protocol header; if dest == IP_HDRINCL, p already includes an IP
00847             header and p->payload points to that IP header)
00848  * @param src the source IP address to send from (if src == IP_ADDR_ANY, the
00849  *         IP  address of the netif used to send is used as source address)
00850  * @param dest the destination IP address to send the packet to
00851  * @param ttl the TTL value to be set in the IP header
00852  * @param tos the TOS value to be set in the IP header
00853  * @param proto the PROTOCOL to be set in the IP header
00854  * @param addr_hint address hint pointer set to netif->addr_hint before
00855  *        calling ip_output_if()
00856  *
00857  * @return ERR_RTE if no route is found
00858  *         see ip_output_if() for more return values
00859  */
00860 err_t
00861 ip_output_hinted(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
00862           u8_t ttl, u8_t tos, u8_t proto, u8_t *addr_hint)
00863 {
00864   struct netif *netif;
00865   err_t err;
00866 
00867   /* pbufs passed to IP must have a ref-count of 1 as their payload pointer
00868      gets altered as the packet is passed down the stack */
00869   LWIP_ASSERT("p->ref == 1", p->ref == 1);
00870 
00871   if ((netif = ip_route(dest)) == NULL) {
00872     LWIP_DEBUGF(IP_DEBUG, ("ip_output: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00873       ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
00874     IP_STATS_INC(ip.rterr);
00875     return ERR_RTE;
00876   }
00877 
00878   NETIF_SET_HWADDRHINT(netif, addr_hint);
00879   err = ip_output_if(p, src, dest, ttl, tos, proto, netif);
00880   NETIF_SET_HWADDRHINT(netif, NULL);
00881 
00882   return err;
00883 }
00884 #endif /* LWIP_NETIF_HWADDRHINT*/
00885 
00886 #if IP_DEBUG
00887 /* Print an IP header by using LWIP_DEBUGF
00888  * @param p an IP packet, p->payload pointing to the IP header
00889  */
00890 void
00891 ip_debug_print(struct pbuf *p)
00892 {
00893   struct ip_hdr *iphdr = (struct ip_hdr *)p->payload;
00894 
00895   LWIP_DEBUGF(IP_DEBUG, ("IP header:\n"));
00896   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00897   LWIP_DEBUGF(IP_DEBUG, ("|%2"S16_F" |%2"S16_F" |  0x%02"X16_F" |     %5"U16_F"     | (v, hl, tos, len)\n",
00898                     IPH_V(iphdr),
00899                     IPH_HL(iphdr),
00900                     IPH_TOS(iphdr),
00901                     ntohs(IPH_LEN(iphdr))));
00902   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00903   LWIP_DEBUGF(IP_DEBUG, ("|    %5"U16_F"      |%"U16_F"%"U16_F"%"U16_F"|    %4"U16_F"   | (id, flags, offset)\n",
00904                     ntohs(IPH_ID(iphdr)),
00905                     ntohs(IPH_OFFSET(iphdr)) >> 15 & 1,
00906                     ntohs(IPH_OFFSET(iphdr)) >> 14 & 1,
00907                     ntohs(IPH_OFFSET(iphdr)) >> 13 & 1,
00908                     ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK));
00909   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00910   LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |    0x%04"X16_F"     | (ttl, proto, chksum)\n",
00911                     IPH_TTL(iphdr),
00912                     IPH_PROTO(iphdr),
00913                     ntohs(IPH_CHKSUM(iphdr))));
00914   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00915   LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  | (src)\n",
00916                     ip4_addr1_16(&iphdr->src),
00917                     ip4_addr2_16(&iphdr->src),
00918                     ip4_addr3_16(&iphdr->src),
00919                     ip4_addr4_16(&iphdr->src)));
00920   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00921   LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  | (dest)\n",
00922                     ip4_addr1_16(&iphdr->dest),
00923                     ip4_addr2_16(&iphdr->dest),
00924                     ip4_addr3_16(&iphdr->dest),
00925                     ip4_addr4_16(&iphdr->dest)));
00926   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00927 }
00928 #endif /* IP_DEBUG */