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 /**
00062  * The interface that provided the packet for the current callback
00063  * invocation.
00064  */
00065 struct netif *current_netif;
00066 
00067 /**
00068  * Header of the input packet currently being processed.
00069  */
00070 const struct ip_hdr *current_header;
00071 
00072 /**
00073  * Finds the appropriate network interface for a given IP address. It
00074  * searches the list of network interfaces linearly. A match is found
00075  * if the masked IP address of the network interface equals the masked
00076  * IP address given to the function.
00077  *
00078  * @param dest the destination IP address for which to find the route
00079  * @return the netif on which to send to reach dest
00080  */
00081 struct netif *
00082 ip_route(ip_addr_t *dest)
00083 {
00084   struct netif *netif;
00085 
00086   /* iterate through netifs */
00087   for(netif = netif_list; netif != NULL; netif = netif->next) {
00088     /* network mask matches? */
00089     if (netif_is_up(netif)) {
00090       if (ip_addr_netcmp(dest, &(netif->ip_addr), &(netif->netmask))) {
00091         /* return netif on which to forward IP packet */
00092         return netif;
00093       }
00094     }
00095   }
00096   if ((netif_default == NULL) || (!netif_is_up(netif_default))) {
00097     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_route: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00098       ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
00099     IP_STATS_INC(ip.rterr);
00100     snmp_inc_ipoutnoroutes();
00101     return NULL;
00102   }
00103   /* no matching netif found, use default netif */
00104   return netif_default;
00105 }
00106 
00107 #if IP_FORWARD
00108 /**
00109  * Forwards an IP packet. It finds an appropriate route for the
00110  * packet, decrements the TTL value of the packet, adjusts the
00111  * checksum and outputs the packet on the appropriate interface.
00112  *
00113  * @param p the packet to forward (p->payload points to IP header)
00114  * @param iphdr the IP header of the input packet
00115  * @param inp the netif on which this packet was received
00116  * @return the netif on which the packet was sent (NULL if it wasn't sent)
00117  */
00118 static struct netif *
00119 ip_forward(struct pbuf *p, struct ip_hdr *iphdr, struct netif *inp)
00120 {
00121   struct netif *netif;
00122   ip_addr_t dest;
00123 
00124   PERF_START;
00125   dest = iphdr->dest;
00126 
00127   /* RFC3927 2.7: do not forward link-local addresses */
00128   if (ip_addr_islinklocal(&dest)) {
00129     LWIP_DEBUGF(IP_DEBUG, ("ip_forward: not forwarding LLA %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00130       ip4_addr1_16(&dest), ip4_addr2_16(&dest), ip4_addr3_16(&dest), ip4_addr4_16(&dest)));
00131     snmp_inc_ipoutnoroutes();
00132     return (struct netif *)NULL;
00133   }
00134 
00135   /* Find network interface where to forward this IP packet to. */
00136   netif = ip_route(&dest);
00137   if (netif == NULL) {
00138     LWIP_DEBUGF(IP_DEBUG, ("ip_forward: no forwarding route for %"U16_F".%"U16_F".%"U16_F".%"U16_F" found\n",
00139       ip4_addr1_16(&dest), ip4_addr2_16(&dest), ip4_addr3_16(&dest), ip4_addr4_16(&dest)));
00140     snmp_inc_ipoutnoroutes();
00141     return (struct netif *)NULL;
00142   }
00143   /* Do not forward packets onto the same network interface on which
00144    * they arrived. */
00145   if (netif == inp) {
00146     LWIP_DEBUGF(IP_DEBUG, ("ip_forward: not bouncing packets back on incoming interface.\n"));
00147     snmp_inc_ipoutnoroutes();
00148     return (struct netif *)NULL;
00149   }
00150 
00151   /* decrement TTL */
00152   IPH_TTL_SET(iphdr, IPH_TTL(iphdr) - 1);
00153   /* send ICMP if TTL == 0 */
00154   if (IPH_TTL(iphdr) == 0) {
00155     snmp_inc_ipinhdrerrors();
00156 #if LWIP_ICMP
00157     /* Don't send ICMP messages in response to ICMP messages */
00158     if (IPH_PROTO(iphdr) != IP_PROTO_ICMP) {
00159       icmp_time_exceeded(p, ICMP_TE_TTL);
00160     }
00161 #endif /* LWIP_ICMP */
00162     return (struct netif *)NULL;
00163   }
00164 
00165   /* Incrementally update the IP checksum. */
00166   if (IPH_CHKSUM(iphdr) >= htons(0xffff - 0x100)) {
00167     IPH_CHKSUM_SET(iphdr, IPH_CHKSUM(iphdr) + htons(0x100) + 1);
00168   } else {
00169     IPH_CHKSUM_SET(iphdr, IPH_CHKSUM(iphdr) + htons(0x100));
00170   }
00171 
00172   LWIP_DEBUGF(IP_DEBUG, ("ip_forward: forwarding packet to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00173     ip4_addr1_16(&dest), ip4_addr2_16(&dest), ip4_addr3_16(&dest), ip4_addr4_16(&dest)));
00174 
00175   IP_STATS_INC(ip.fw);
00176   IP_STATS_INC(ip.xmit);
00177   snmp_inc_ipforwdatagrams();
00178 
00179   PERF_STOP("ip_forward");
00180   /* transmit pbuf on chosen interface */
00181   netif->output(netif, p, &dest);
00182   return netif;
00183 }
00184 #endif /* IP_FORWARD */
00185 
00186 /**
00187  * This function is called by the network interface device driver when
00188  * an IP packet is received. The function does the basic checks of the
00189  * IP header such as packet size being at least larger than the header
00190  * size etc. If the packet was not destined for us, the packet is
00191  * forwarded (using ip_forward). The IP checksum is always checked.
00192  *
00193  * Finally, the packet is sent to the upper layer protocol input function.
00194  * 
00195  * @param p the received IP packet (p->payload points to IP header)
00196  * @param inp the netif on which this packet was received
00197  * @return ERR_OK if the packet was processed (could return ERR_* if it wasn't
00198  *         processed, but currently always returns ERR_OK)
00199  */
00200 err_t
00201 ip_input(struct pbuf *p, struct netif *inp)
00202 {
00203   struct ip_hdr *iphdr;
00204   struct netif *netif;
00205   u16_t iphdr_hlen;
00206   u16_t iphdr_len;
00207 #if LWIP_DHCP
00208   int check_ip_src=1;
00209 #endif /* LWIP_DHCP */
00210 
00211   IP_STATS_INC(ip.recv);
00212   snmp_inc_ipinreceives();
00213 
00214   /* identify the IP header */
00215   iphdr = (struct ip_hdr *)p->payload;
00216   if (IPH_V(iphdr) != 4) {
00217     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_WARNING, ("IP packet dropped due to bad version number %"U16_F"\n", IPH_V(iphdr)));
00218     ip_debug_print(p);
00219     pbuf_free(p);
00220     IP_STATS_INC(ip.err);
00221     IP_STATS_INC(ip.drop);
00222     snmp_inc_ipinhdrerrors();
00223     return ERR_OK;
00224   }
00225 
00226   /* obtain IP header length in number of 32-bit words */
00227   iphdr_hlen = IPH_HL(iphdr);
00228   /* calculate IP header length in bytes */
00229   iphdr_hlen *= 4;
00230   /* obtain ip length in bytes */
00231   iphdr_len = ntohs(IPH_LEN(iphdr));
00232 
00233   /* header length exceeds first pbuf length, or ip length exceeds total pbuf length? */
00234   if ((iphdr_hlen > p->len) || (iphdr_len > p->tot_len)) {
00235     if (iphdr_hlen > p->len) {
00236       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00237         ("IP header (len %"U16_F") does not fit in first pbuf (len %"U16_F"), IP packet dropped.\n",
00238         iphdr_hlen, p->len));
00239     }
00240     if (iphdr_len > p->tot_len) {
00241       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00242         ("IP (len %"U16_F") is longer than pbuf (len %"U16_F"), IP packet dropped.\n",
00243         iphdr_len, p->tot_len));
00244     }
00245     /* free (drop) packet pbufs */
00246     pbuf_free(p);
00247     IP_STATS_INC(ip.lenerr);
00248     IP_STATS_INC(ip.drop);
00249     snmp_inc_ipindiscards();
00250     return ERR_OK;
00251   }
00252 
00253   /* verify checksum */
00254 #if CHECKSUM_CHECK_IP
00255   if (inet_chksum(iphdr, iphdr_hlen) != 0) {
00256 
00257     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00258       ("Checksum (0x%"X16_F") failed, IP packet dropped.\n", inet_chksum(iphdr, iphdr_hlen)));
00259     ip_debug_print(p);
00260     pbuf_free(p);
00261     IP_STATS_INC(ip.chkerr);
00262     IP_STATS_INC(ip.drop);
00263     snmp_inc_ipinhdrerrors();
00264     return ERR_OK;
00265   }
00266 #endif
00267 
00268   /* Trim pbuf. This should have been done at the netif layer,
00269    * but we'll do it anyway just to be sure that its done. */
00270   pbuf_realloc(p, iphdr_len);
00271 
00272   /* match packet against an interface, i.e. is this packet for us? */
00273 #if LWIP_IGMP
00274   if (ip_addr_ismulticast(&(iphdr->dest))) {
00275     if ((inp->flags & NETIF_FLAG_IGMP) && (igmp_lookfor_group(inp, &(iphdr->dest)))) {
00276       netif = inp;
00277     } else {
00278       netif = NULL;
00279     }
00280   } else
00281 #endif /* LWIP_IGMP */
00282   {
00283     /* start trying with inp. if that's not acceptable, start walking the
00284        list of configured netifs.
00285        'first' is used as a boolean to mark whether we started walking the list */
00286     int first = 1;
00287     netif = inp;
00288     do {
00289       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",
00290           ip4_addr_get_u32(&iphdr->dest), ip4_addr_get_u32(&netif->ip_addr),
00291           ip4_addr_get_u32(&iphdr->dest) & ip4_addr_get_u32(&netif->netmask),
00292           ip4_addr_get_u32(&netif->ip_addr) & ip4_addr_get_u32(&netif->netmask),
00293           ip4_addr_get_u32(&iphdr->dest) & ~ip4_addr_get_u32(&netif->netmask)));
00294 
00295       /* interface is up and configured? */
00296       if ((netif_is_up(netif)) && (!ip_addr_isany(&(netif->ip_addr)))) {
00297         /* unicast to this interface address? */
00298         if (ip_addr_cmp(&(iphdr->dest), &(netif->ip_addr)) ||
00299             /* or broadcast on this interface network address? */
00300             ip_addr_isbroadcast(&(iphdr->dest), netif)) {
00301           LWIP_DEBUGF(IP_DEBUG, ("ip_input: packet accepted on interface %c%c\n",
00302               netif->name[0], netif->name[1]));
00303           /* break out of for loop */
00304           break;
00305         }
00306 #if LWIP_AUTOIP
00307         /* connections to link-local addresses must persist after changing
00308            the netif's address (RFC3927 ch. 1.9) */
00309         if ((netif->autoip != NULL) &&
00310             ip_addr_cmp(&(iphdr->dest), &(netif->autoip->llipaddr))) {
00311           LWIP_DEBUGF(IP_DEBUG, ("ip_input: LLA packet accepted on interface %c%c\n",
00312               netif->name[0], netif->name[1]));
00313           /* break out of for loop */
00314           break;
00315         }
00316 #endif /* LWIP_AUTOIP */
00317       }
00318       if (first) {
00319         first = 0;
00320         netif = netif_list;
00321       } else {
00322         netif = netif->next;
00323       }
00324       if (netif == inp) {
00325         netif = netif->next;
00326       }
00327     } while(netif != NULL);
00328   }
00329 
00330 #if LWIP_DHCP
00331   /* Pass DHCP messages regardless of destination address. DHCP traffic is addressed
00332    * using link layer addressing (such as Ethernet MAC) so we must not filter on IP.
00333    * According to RFC 1542 section 3.1.1, referred by RFC 2131).
00334    */
00335   if (netif == NULL) {
00336     /* remote port is DHCP server? */
00337     if (IPH_PROTO(iphdr) == IP_PROTO_UDP) {
00338       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: UDP packet to DHCP client port %"U16_F"\n",
00339         ntohs(((struct udp_hdr *)((u8_t *)iphdr + iphdr_hlen))->dest)));
00340       if (ntohs(((struct udp_hdr *)((u8_t *)iphdr + iphdr_hlen))->dest) == DHCP_CLIENT_PORT) {
00341         LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: DHCP packet accepted.\n"));
00342         netif = inp;
00343         check_ip_src = 0;
00344       }
00345     }
00346   }
00347 #endif /* LWIP_DHCP */
00348 
00349   /* broadcast or multicast packet source address? Compliant with RFC 1122: 3.2.1.3 */
00350 #if LWIP_DHCP
00351   /* DHCP servers need 0.0.0.0 to be allowed as source address (RFC 1.1.2.2: 3.2.1.3/a) */
00352   if (check_ip_src && !ip_addr_isany(&iphdr->src))
00353 #endif /* LWIP_DHCP */
00354   {  if ((ip_addr_isbroadcast(&(iphdr->src), inp)) ||
00355          (ip_addr_ismulticast(&(iphdr->src)))) {
00356       /* packet source is not valid */
00357       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING, ("ip_input: packet source is not valid.\n"));
00358       /* free (drop) packet pbufs */
00359       pbuf_free(p);
00360       IP_STATS_INC(ip.drop);
00361       snmp_inc_ipinaddrerrors();
00362       snmp_inc_ipindiscards();
00363       return ERR_OK;
00364     }
00365   }
00366 
00367   /* packet not for us? */
00368   if (netif == NULL) {
00369     /* packet not for us, route or discard */
00370     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: packet not for us.\n"));
00371 #if IP_FORWARD
00372     /* non-broadcast packet? */
00373     if (!ip_addr_isbroadcast(&(iphdr->dest), inp)) {
00374       /* try to forward IP packet on (other) interfaces */
00375       ip_forward(p, iphdr, inp);
00376     } else
00377 #endif /* IP_FORWARD */
00378     {
00379       snmp_inc_ipinaddrerrors();
00380       snmp_inc_ipindiscards();
00381     }
00382     pbuf_free(p);
00383     return ERR_OK;
00384   }
00385   /* packet consists of multiple fragments? */
00386   if ((IPH_OFFSET(iphdr) & htons(IP_OFFMASK | IP_MF)) != 0) {
00387 #if IP_REASSEMBLY /* packet fragment reassembly code present? */
00388     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",
00389       ntohs(IPH_ID(iphdr)), p->tot_len, ntohs(IPH_LEN(iphdr)), !!(IPH_OFFSET(iphdr) & htons(IP_MF)), (ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK)*8));
00390     /* reassemble the packet*/
00391     p = ip_reass(p);
00392     /* packet not fully reassembled yet? */
00393     if (p == NULL) {
00394       return ERR_OK;
00395     }
00396     iphdr = (struct ip_hdr *)p->payload;
00397 #else /* IP_REASSEMBLY == 0, no packet fragment reassembly code present */
00398     pbuf_free(p);
00399     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since it was fragmented (0x%"X16_F") (while IP_REASSEMBLY == 0).\n",
00400       ntohs(IPH_OFFSET(iphdr))));
00401     IP_STATS_INC(ip.opterr);
00402     IP_STATS_INC(ip.drop);
00403     /* unsupported protocol feature */
00404     snmp_inc_ipinunknownprotos();
00405     return ERR_OK;
00406 #endif /* IP_REASSEMBLY */
00407   }
00408 
00409 #if IP_OPTIONS_ALLOWED == 0 /* no support for IP options in the IP header? */
00410 
00411 #if LWIP_IGMP
00412   /* there is an extra "router alert" option in IGMP messages which we allow for but do not police */
00413   if((iphdr_hlen > IP_HLEN) &&  (IPH_PROTO(iphdr) != IP_PROTO_IGMP)) {
00414 #else
00415   if (iphdr_hlen > IP_HLEN) {
00416 #endif /* LWIP_IGMP */
00417     LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since there were IP options (while IP_OPTIONS_ALLOWED == 0).\n"));
00418     pbuf_free(p);
00419     IP_STATS_INC(ip.opterr);
00420     IP_STATS_INC(ip.drop);
00421     /* unsupported protocol feature */
00422     snmp_inc_ipinunknownprotos();
00423     return ERR_OK;
00424   }
00425 #endif /* IP_OPTIONS_ALLOWED == 0 */
00426 
00427   /* send to upper layers */
00428   LWIP_DEBUGF(IP_DEBUG, ("ip_input: \n"));
00429   ip_debug_print(p);
00430   LWIP_DEBUGF(IP_DEBUG, ("ip_input: p->len %"U16_F" p->tot_len %"U16_F"\n", p->len, p->tot_len));
00431 
00432   current_netif = inp;
00433   current_header = iphdr;
00434 
00435 #if LWIP_RAW
00436   /* raw input did not eat the packet? */
00437   if (raw_input(p, inp) == 0)
00438 #endif /* LWIP_RAW */
00439   {
00440 
00441     switch (IPH_PROTO(iphdr)) {
00442 #if LWIP_UDP
00443     case IP_PROTO_UDP:
00444 #if LWIP_UDPLITE
00445     case IP_PROTO_UDPLITE:
00446 #endif /* LWIP_UDPLITE */
00447       snmp_inc_ipindelivers();
00448       udp_input(p, inp);
00449       break;
00450 #endif /* LWIP_UDP */
00451 #if LWIP_TCP
00452     case IP_PROTO_TCP:
00453       snmp_inc_ipindelivers();
00454       tcp_input(p, inp);
00455       break;
00456 #endif /* LWIP_TCP */
00457 #if LWIP_ICMP
00458     case IP_PROTO_ICMP:
00459       snmp_inc_ipindelivers();
00460       icmp_input(p, inp);
00461       break;
00462 #endif /* LWIP_ICMP */
00463 #if LWIP_IGMP
00464     case IP_PROTO_IGMP:
00465       igmp_input(p,inp,&(iphdr->dest));
00466       break;
00467 #endif /* LWIP_IGMP */
00468     default:
00469 #if LWIP_ICMP
00470       /* send ICMP destination protocol unreachable unless is was a broadcast */
00471       if (!ip_addr_isbroadcast(&(iphdr->dest), inp) &&
00472           !ip_addr_ismulticast(&(iphdr->dest))) {
00473         p->payload = iphdr;
00474         icmp_dest_unreach(p, ICMP_DUR_PROTO);
00475       }
00476 #endif /* LWIP_ICMP */
00477       pbuf_free(p);
00478 
00479       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("Unsupported transport protocol %"U16_F"\n", IPH_PROTO(iphdr)));
00480 
00481       IP_STATS_INC(ip.proterr);
00482       IP_STATS_INC(ip.drop);
00483       snmp_inc_ipinunknownprotos();
00484     }
00485   }
00486 
00487   current_netif = NULL;
00488   current_header = NULL;
00489 
00490   return ERR_OK;
00491 }
00492 
00493 /**
00494  * Sends an IP packet on a network interface. This function constructs
00495  * the IP header and calculates the IP header checksum. If the source
00496  * IP address is NULL, the IP address of the outgoing network
00497  * interface is filled in as source address.
00498  * If the destination IP address is IP_HDRINCL, p is assumed to already
00499  * include an IP header and p->payload points to it instead of the data.
00500  *
00501  * @param p the packet to send (p->payload points to the data, e.g. next
00502             protocol header; if dest == IP_HDRINCL, p already includes an IP
00503             header and p->payload points to that IP header)
00504  * @param src the source IP address to send from (if src == IP_ADDR_ANY, the
00505  *         IP  address of the netif used to send is used as source address)
00506  * @param dest the destination IP address to send the packet to
00507  * @param ttl the TTL value to be set in the IP header
00508  * @param tos the TOS value to be set in the IP header
00509  * @param proto the PROTOCOL to be set in the IP header
00510  * @param netif the netif on which to send this packet
00511  * @return ERR_OK if the packet was sent OK
00512  *         ERR_BUF if p doesn't have enough space for IP/LINK headers
00513  *         returns errors returned by netif->output
00514  *
00515  * @note ip_id: RFC791 "some host may be able to simply use
00516  *  unique identifiers independent of destination"
00517  */
00518 err_t
00519 ip_output_if(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
00520              u8_t ttl, u8_t tos,
00521              u8_t proto, struct netif *netif)
00522 {
00523 #if IP_OPTIONS_SEND
00524   return ip_output_if_opt(p, src, dest, ttl, tos, proto, netif, NULL, 0);
00525 }
00526 
00527 /**
00528  * Same as ip_output_if() but with the possibility to include IP options:
00529  *
00530  * @ param ip_options pointer to the IP options, copied into the IP header
00531  * @ param optlen length of ip_options
00532  */
00533 err_t ip_output_if_opt(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
00534        u8_t ttl, u8_t tos, u8_t proto, struct netif *netif, void *ip_options,
00535        u16_t optlen)
00536 {
00537 #endif /* IP_OPTIONS_SEND */
00538   struct ip_hdr *iphdr;
00539   static u16_t ip_id = 0;
00540 
00541   /* pbufs passed to IP must have a ref-count of 1 as their payload pointer
00542      gets altered as the packet is passed down the stack */
00543   LWIP_ASSERT("p->ref == 1", p->ref == 1);
00544 
00545   snmp_inc_ipoutrequests();
00546 
00547   /* Should the IP header be generated or is it already included in p? */
00548   if (dest != IP_HDRINCL) {
00549     u16_t ip_hlen = IP_HLEN;
00550 #if IP_OPTIONS_SEND
00551     u16_t optlen_aligned = 0;
00552     if (optlen != 0) {
00553       /* round up to a multiple of 4 */
00554       optlen_aligned = ((optlen + 3) & ~3);
00555       ip_hlen += optlen_aligned;
00556       /* First write in the IP options */
00557       if (pbuf_header(p, optlen_aligned)) {
00558         LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_output_if_opt: not enough room for IP options in pbuf\n"));
00559         IP_STATS_INC(ip.err);
00560         snmp_inc_ipoutdiscards();
00561         return ERR_BUF;
00562       }
00563       MEMCPY(p->payload, ip_options, optlen);
00564       if (optlen < optlen_aligned) {
00565         /* zero the remaining bytes */
00566         memset(((char*)p->payload) + optlen, 0, optlen_aligned - optlen);
00567       }
00568     }
00569 #endif /* IP_OPTIONS_SEND */
00570     /* generate IP header */
00571     if (pbuf_header(p, IP_HLEN)) {
00572       LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_output: not enough room for IP header in pbuf\n"));
00573 
00574       IP_STATS_INC(ip.err);
00575       snmp_inc_ipoutdiscards();
00576       return ERR_BUF;
00577     }
00578 
00579     iphdr = (struct ip_hdr *)p->payload;
00580     LWIP_ASSERT("check that first pbuf can hold struct ip_hdr",
00581                (p->len >= sizeof(struct ip_hdr)));
00582 
00583     IPH_TTL_SET(iphdr, ttl);
00584     IPH_PROTO_SET(iphdr, proto);
00585 
00586     /* dest cannot be NULL here */
00587     ip_addr_copy(iphdr->dest, *dest);
00588 
00589     IPH_VHLTOS_SET(iphdr, 4, ip_hlen / 4, tos);
00590     IPH_LEN_SET(iphdr, htons(p->tot_len));
00591     IPH_OFFSET_SET(iphdr, 0);
00592     IPH_ID_SET(iphdr, htons(ip_id));
00593     ++ip_id;
00594 
00595     if (ip_addr_isany(src)) {
00596       ip_addr_copy(iphdr->src, netif->ip_addr);
00597     } else {
00598       /* src cannot be NULL here */
00599       ip_addr_copy(iphdr->src, *src);
00600     }
00601 
00602     IPH_CHKSUM_SET(iphdr, 0);
00603 #if CHECKSUM_GEN_IP
00604     IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, ip_hlen));
00605 #endif
00606   } else {
00607     /* IP header already included in p */
00608     iphdr = (struct ip_hdr *)p->payload;
00609     dest = &(iphdr->dest);
00610   }
00611 
00612   IP_STATS_INC(ip.xmit);
00613 
00614   LWIP_DEBUGF(IP_DEBUG, ("ip_output_if: %c%c%"U16_F"\n", netif->name[0], netif->name[1], netif->num));
00615   ip_debug_print(p);
00616 
00617 #if ENABLE_LOOPBACK
00618   if (ip_addr_cmp(dest, &netif->ip_addr)) {
00619     /* Packet to self, enqueue it for loopback */
00620     LWIP_DEBUGF(IP_DEBUG, ("netif_loop_output()"));
00621     return netif_loop_output(netif, p, dest);
00622   }
00623 #endif /* ENABLE_LOOPBACK */
00624 #if IP_FRAG
00625   /* don't fragment if interface has mtu set to 0 [loopif] */
00626   if (netif->mtu && (p->tot_len > netif->mtu)) {
00627     return ip_frag(p,netif,dest);
00628   }
00629 #endif
00630 
00631   LWIP_DEBUGF(IP_DEBUG, ("netif->output()"));
00632   return netif->output(netif, p, dest);
00633 }
00634 
00635 /**
00636  * Simple interface to ip_output_if. It finds the outgoing network
00637  * interface and calls upon ip_output_if to do the actual work.
00638  *
00639  * @param p the packet to send (p->payload points to the data, e.g. next
00640             protocol header; if dest == IP_HDRINCL, p already includes an IP
00641             header and p->payload points to that IP header)
00642  * @param src the source IP address to send from (if src == IP_ADDR_ANY, the
00643  *         IP  address of the netif used to send is used as source address)
00644  * @param dest the destination IP address to send the packet to
00645  * @param ttl the TTL value to be set in the IP header
00646  * @param tos the TOS value to be set in the IP header
00647  * @param proto the PROTOCOL to be set in the IP header
00648  *
00649  * @return ERR_RTE if no route is found
00650  *         see ip_output_if() for more return values
00651  */
00652 err_t
00653 ip_output(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
00654           u8_t ttl, u8_t tos, u8_t proto)
00655 {
00656   struct netif *netif;
00657 
00658   /* pbufs passed to IP must have a ref-count of 1 as their payload pointer
00659      gets altered as the packet is passed down the stack */
00660   LWIP_ASSERT("p->ref == 1", p->ref == 1);
00661 
00662   if ((netif = ip_route(dest)) == NULL) {
00663     LWIP_DEBUGF(IP_DEBUG, ("ip_output: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00664       ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
00665     IP_STATS_INC(ip.rterr);
00666     return ERR_RTE;
00667   }
00668 
00669   return ip_output_if(p, src, dest, ttl, tos, proto, netif);
00670 }
00671 
00672 #if LWIP_NETIF_HWADDRHINT
00673 /** Like ip_output, but takes and addr_hint pointer that is passed on to netif->addr_hint
00674  *  before calling ip_output_if.
00675  *
00676  * @param p the packet to send (p->payload points to the data, e.g. next
00677             protocol header; if dest == IP_HDRINCL, p already includes an IP
00678             header and p->payload points to that IP header)
00679  * @param src the source IP address to send from (if src == IP_ADDR_ANY, the
00680  *         IP  address of the netif used to send is used as source address)
00681  * @param dest the destination IP address to send the packet to
00682  * @param ttl the TTL value to be set in the IP header
00683  * @param tos the TOS value to be set in the IP header
00684  * @param proto the PROTOCOL to be set in the IP header
00685  * @param addr_hint address hint pointer set to netif->addr_hint before
00686  *        calling ip_output_if()
00687  *
00688  * @return ERR_RTE if no route is found
00689  *         see ip_output_if() for more return values
00690  */
00691 err_t
00692 ip_output_hinted(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
00693           u8_t ttl, u8_t tos, u8_t proto, u8_t *addr_hint)
00694 {
00695   struct netif *netif;
00696   err_t err;
00697 
00698   /* pbufs passed to IP must have a ref-count of 1 as their payload pointer
00699      gets altered as the packet is passed down the stack */
00700   LWIP_ASSERT("p->ref == 1", p->ref == 1);
00701 
00702   if ((netif = ip_route(dest)) == NULL) {
00703     LWIP_DEBUGF(IP_DEBUG, ("ip_output: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
00704       ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
00705     IP_STATS_INC(ip.rterr);
00706     return ERR_RTE;
00707   }
00708 
00709   netif->addr_hint = addr_hint;
00710   err = ip_output_if(p, src, dest, ttl, tos, proto, netif);
00711   netif->addr_hint = NULL;
00712 
00713   return err;
00714 }
00715 #endif /* LWIP_NETIF_HWADDRHINT*/
00716 
00717 #if IP_DEBUG
00718 /* Print an IP header by using LWIP_DEBUGF
00719  * @param p an IP packet, p->payload pointing to the IP header
00720  */
00721 void
00722 ip_debug_print(struct pbuf *p)
00723 {
00724   struct ip_hdr *iphdr = (struct ip_hdr *) p->payload;
00725   u8_t *payload;
00726 
00727   payload = (u8_t *)iphdr + IP_HLEN;
00728 
00729   LWIP_DEBUGF(IP_DEBUG, ("IP header:\n"));
00730   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00731   LWIP_DEBUGF(IP_DEBUG, ("|%2"S16_F" |%2"S16_F" |  0x%02"X16_F" |     %5"U16_F"     | (v, hl, tos, len)\n",
00732                     IPH_V(iphdr),
00733                     IPH_HL(iphdr),
00734                     IPH_TOS(iphdr),
00735                     ntohs(IPH_LEN(iphdr))));
00736   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00737   LWIP_DEBUGF(IP_DEBUG, ("|    %5"U16_F"      |%"U16_F"%"U16_F"%"U16_F"|    %4"U16_F"   | (id, flags, offset)\n",
00738                     ntohs(IPH_ID(iphdr)),
00739                     ntohs(IPH_OFFSET(iphdr)) >> 15 & 1,
00740                     ntohs(IPH_OFFSET(iphdr)) >> 14 & 1,
00741                     ntohs(IPH_OFFSET(iphdr)) >> 13 & 1,
00742                     ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK));
00743   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00744   LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |    0x%04"X16_F"     | (ttl, proto, chksum)\n",
00745                     IPH_TTL(iphdr),
00746                     IPH_PROTO(iphdr),
00747                     ntohs(IPH_CHKSUM(iphdr))));
00748   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00749   LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  | (src)\n",
00750                     ip4_addr1_16(&iphdr->src),
00751                     ip4_addr2_16(&iphdr->src),
00752                     ip4_addr3_16(&iphdr->src),
00753                     ip4_addr4_16(&iphdr->src)));
00754   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00755   LWIP_DEBUGF(IP_DEBUG, ("|  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  |  %3"U16_F"  | (dest)\n",
00756                     ip4_addr1_16(&iphdr->dest),
00757                     ip4_addr2_16(&iphdr->dest),
00758                     ip4_addr3_16(&iphdr->dest),
00759                     ip4_addr4_16(&iphdr->dest)));
00760   LWIP_DEBUGF(IP_DEBUG, ("+-------------------------------+\n"));
00761 }
00762 #endif /* IP_DEBUG */