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/**

 * @file

 * This is the IPv4 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/ip.h"

#include "lwip/def.h"

#include "lwip/mem.h"

#include "lwip/ip_frag.h"

#include "lwip/inet.h"

#include "lwip/inet_chksum.h"

#include "lwip/netif.h"

#include "lwip/icmp.h"

#include "lwip/igmp.h"

#include "lwip/raw.h"

#include "lwip/udp.h"

#include "lwip/tcp.h"

#include "lwip/snmp.h"

#include "lwip/dhcp.h"

#include "lwip/stats.h"

#include "arch/perf.h"

#include <string.h>

/**

 * The interface that provided the packet for the current callback

 * invocation.

 */

struct netif *current_netif;

/**

 * Header of the input packet currently being processed.

 */

const struct ip_hdr *current_header;

/**

 * 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.

 *

 * @param dest the destination IP address for which to find the route

 * @return the netif on which to send to reach dest

 */

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 (netif_is_up(netif)) {

      if (ip_addr_netcmp(dest, &(netif->ip_addr), &(netif->netmask))) {

        /* return netif on which to forward IP packet */

        return netif;

      }

    }

  }

  if ((netif_default == NULL) || (!netif_is_up(netif_default))) {

    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_route: No route to 0x%"X32_F"\n", dest->addr));

    IP_STATS_INC(ip.rterr);

    snmp_inc_ipoutnoroutes();

    return NULL;

  }

  /* 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.

 *

 * @param p the packet to forward (p->payload points to IP header)

 * @param iphdr the IP header of the input packet

 * @param inp the netif on which this packet was received

 * @return the netif on which the packet was sent (NULL if it wasn't sent)

 */

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_ipoutnoroutes();

    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_ipoutnoroutes();

    return (struct netif *)NULL;

  }

  /* decrement TTL */

  IPH_TTL_SET(iphdr, IPH_TTL(iphdr) - 1);

  /* send ICMP if TTL == 0 */

  if (IPH_TTL(iphdr) == 0) {

    snmp_inc_ipinhdrerrors();

#if LWIP_ICMP

    /* Don't send ICMP messages in response to ICMP messages */

    if (IPH_PROTO(iphdr) != IP_PROTO_ICMP) {

      icmp_time_exceeded(p, ICMP_TE_TTL);

    }

#endif /* LWIP_ICMP */

    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.

 *

 * @param p the received IP packet (p->payload points to IP header)

 * @param inp the netif on which this packet was received

 * @return ERR_OK if the packet was processed (could return ERR_* if it wasn't

 *         processed, but currently always returns ERR_OK)

 */

err_t

ip_input(struct pbuf *p, struct netif *inp)

{

  struct ip_hdr *iphdr;

  struct netif *netif;

  u16_t iphdr_hlen;

  u16_t iphdr_len;

#if LWIP_DHCP

  int check_ip_src=1;

#endif /* LWIP_DHCP */

  IP_STATS_INC(ip.recv);

  snmp_inc_ipinreceives();

  /* identify the IP header */

  iphdr = p->payload;

  if (IPH_V(iphdr) != 4) {

    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_WARNING, ("IP packet dropped due to bad version number %"U16_F"\n", IPH_V(iphdr)));

    ip_debug_print(p);

    pbuf_free(p);

    IP_STATS_INC(ip.err);

    IP_STATS_INC(ip.drop);

    snmp_inc_ipinhdrerrors();

    return ERR_OK;

  }

  /* obtain IP header length in number of 32-bit words */

  iphdr_hlen = IPH_HL(iphdr);

  /* calculate IP header length in bytes */

  iphdr_hlen *= 4;

  /* obtain ip length in bytes */

  iphdr_len = ntohs(IPH_LEN(iphdr));

  /* header length exceeds first pbuf length, or ip length exceeds total pbuf length? */

  if ((iphdr_hlen > p->len) || (iphdr_len > p->tot_len)) {

    if (iphdr_hlen > p->len) {

      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,

        ("IP header (len %"U16_F") does not fit in first pbuf (len %"U16_F"), IP packet dropped.\n",

        iphdr_hlen, p->len));

    }

    if (iphdr_len > p->tot_len) {

      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,

        ("IP (len %"U16_F") is longer than pbuf (len %"U16_F"), IP packet dropped.\n",

        iphdr_len, p->tot_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, 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);

  /* match packet against an interface, i.e. is this packet for us? */

#if LWIP_IGMP

  if (ip_addr_ismulticast(&(iphdr->dest))) {

    if ((inp->flags & NETIF_FLAG_IGMP) && (igmp_lookfor_group(inp, &(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",

          iphdr->dest.addr, netif->ip_addr.addr,

          iphdr->dest.addr & netif->netmask.addr,

          netif->ip_addr.addr & netif->netmask.addr,

          iphdr->dest.addr & ~(netif->netmask.addr)));

      /* interface 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)) {

          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 (first) {

        first = 0;

        netif = netif_list;

      } else {

        netif = netif->next;

      }

      if (netif == inp) {

        netif = netif->next;

      }

    } while(netif != NULL);

  }

#if LWIP_DHCP

  /* 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 (netif == NULL) {

    /* remote port is DHCP server? */

    if (IPH_PROTO(iphdr) == IP_PROTO_UDP) {

      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: UDP packet to DHCP client port %"U16_F"\n",

        ntohs(((struct udp_hdr *)((u8_t *)iphdr + iphdr_hlen))->dest)));

      if (ntohs(((struct udp_hdr *)((u8_t *)iphdr + iphdr_hlen))->dest) == DHCP_CLIENT_PORT) {

        LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: DHCP packet accepted.\n"));

        netif = inp;

        check_ip_src = 0;

      }

    }

  }

#endif /* LWIP_DHCP */

  /* broadcast or multicast packet source address? Compliant with RFC 1122: 3.2.1.3 */

#if LWIP_DHCP

  /* 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 && (iphdr->src.addr != 0))

#endif /* LWIP_DHCP */

  {  if ((ip_addr_isbroadcast(&(iphdr->src), inp)) ||

         (ip_addr_ismulticast(&(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(&(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) & 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) & 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 = 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,&(iphdr->dest));

      break;

#endif /* LWIP_IGMP */

    default:

#if LWIP_ICMP

      /* 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);

      }

#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;

  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, struct ip_addr *src, struct ip_addr *dest,

             u8_t ttl, u8_t tos,

             u8_t proto, struct netif *netif)

{

#if IP_OPTIONS_SEND

  return ip_output_if_opt(p, src, dest, ttl, tos, proto, netif, NULL, 0);

}

/**

 * Same as ip_output_if() but with the possibility to include IP options:

 *

 * @ param ip_options pointer to the IP options, copied into the IP header

 * @ param optlen length of ip_options

 */

err_t ip_output_if_opt(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,

       u8_t ttl, u8_t tos, u8_t proto, struct netif *netif, void *ip_options,

       u16_t optlen)

{

#endif /* IP_OPTIONS_SEND */

  struct ip_hdr *iphdr;

  static u16_t ip_id = 0;

  snmp_inc_ipoutrequests();

  /* Should the IP header be generated or is it already included in p? */

  if (dest != IP_HDRINCL) {

    u16_t ip_hlen = IP_HLEN;

#if IP_OPTIONS_SEND

    u16_t optlen_aligned = 0;

    if (optlen != 0) {

      /* round up to a multiple of 4 */

      optlen_aligned = ((optlen + 3) & ~3);

      ip_hlen += optlen_aligned;

      /* First write in the IP options */

      if (pbuf_header(p, optlen_aligned)) {

        LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_output_if_opt: not enough room for IP options in pbuf\n"));

        IP_STATS_INC(ip.err);

        snmp_inc_ipoutdiscards();

        return ERR_BUF;

      }

      MEMCPY(p->payload, ip_options, optlen);

      if (optlen < optlen_aligned) {

        /* zero the remaining bytes */

        memset(((char*)p->payload) + optlen, 0, optlen_aligned - optlen);

      }

    }

#endif /* IP_OPTIONS_SEND */

    /* generate IP header */

    if (pbuf_header(p, IP_HLEN)) {

      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("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;

    LWIP_ASSERT("check that first pbuf can hold struct ip_hdr",

               (p->len >= sizeof(struct ip_hdr)));

    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, 0);

    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 {

    /* IP header already included in p */

    iphdr = p->payload;

    dest = &(iphdr->dest);

  }

  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);

#if ENABLE_LOOPBACK

  if (ip_addr_cmp(dest, &netif->ip_addr)) {

    /* Packet to self, enqueue it for loopback */

    LWIP_DEBUGF(IP_DEBUG, ("netif_loop_output()"));

    return netif_loop_output(netif, p, dest);

  }

#endif /* ENABLE_LOOPBACK */

#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

  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.

 *

 * @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

 *

 * @return ERR_RTE if no route is found

 *         see ip_output_if() for more return values

 */

err_t

ip_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, ("ip_output: No route to 0x%"X32_F"\n", dest->addr));

    IP_STATS_INC(ip.rterr);

    return ERR_RTE;

  }

  return ip_output_if(p, src, dest, ttl, tos, proto, netif);

}

#if LWIP_NETIF_HWADDRHINT

/** Like ip_output, but takes and addr_hint pointer that is passed on to netif->addr_hint

 *  before calling ip_output_if.

 *

 * @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 addr_hint address hint pointer set to netif->addr_hint before

 *        calling ip_output_if()

 *

 * @return ERR_RTE if no route is found

 *         see ip_output_if() for more return values

 */

err_t

ip_output_hinted(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,

          u8_t ttl, u8_t tos, u8_t proto, u8_t *addr_hint)

{

  struct netif *netif;

  err_t err;

  if ((netif = ip_route(dest)) == NULL) {

    LWIP_DEBUGF(IP_DEBUG, ("ip_output: No route to 0x%"X32_F"\n", dest->addr));

    IP_STATS_INC(ip.rterr);

    return ERR_RTE;

  }

  netif->addr_hint = addr_hint;

  err = ip_output_if(p, src, dest, ttl, tos, proto, netif);

  netif->addr_hint = NULL;

  return err;

}

#endif /* LWIP_NETIF_HWADDRHINT*/

#if IP_DEBUG

/* Print an IP header by using LWIP_DEBUGF

 * @param p an IP packet, p->payload pointing to the IP header

 */