udp.c

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/**
 * @file
 * User Datagram Protocol module
 *
 */
/*
 * 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 <[e-mail]>
 *
 */


/* udp.c
 *
 * The code for the User Datagram Protocol UDP.
 *
 */

#include <string.h>

#include "lwip/opt.h"

#include "lwip/def.h"
#include "lwip/memp.h"
#include "lwip/inet.h"
#include "lwip/ip_addr.h"
#include "lwip/netif.h"
#include "lwip/udp.h"
#include "lwip/icmp.h"

#include "lwip/stats.h"

#include "arch/perf.h"
#include "lwip/snmp.h"

/* The list of UDP PCBs */
#if LWIP_UDP
/* was static, but we may want to access this from a socket layer */
struct udp_pcb *udp_pcbs = NULL;

static struct udp_pcb *pcb_cache = NULL;

void
udp_init(void)
{
  udp_pcbs = pcb_cache = NULL;
}

/**
 * Process an incoming UDP datagram.
 *
 * Given an incoming UDP datagram (as a chain of pbufs) this function
 * finds a corresponding UDP PCB and
 *
 * @param pbuf pbuf to be demultiplexed to a UDP PCB.
 * @param netif network interface on which the datagram was received.
 *
 */
void
udp_input(struct pbuf *p, struct netif *inp)
{
  struct udp_hdr *udphdr;
  struct udp_pcb *pcb;
  struct udp_pcb *uncon_pcb;
  struct ip_hdr *iphdr;
  u16_t src, dest;
  u8_t local_match;

  PERF_START;

  UDP_STATS_INC(udp.recv);

  iphdr = p->payload;

  if (pbuf_header(p, -((s16_t)(UDP_HLEN + IPH_HL(iphdr) * 4)))) {
    /* drop short packets */
    LWIP_DEBUGF(UDP_DEBUG, ("udp_input: short UDP datagram (%"U16_F" bytes) discarded\n", p->tot_len));
    UDP_STATS_INC(udp.lenerr);
    UDP_STATS_INC(udp.drop);
    snmp_inc_udpinerrors();
    pbuf_free(p);
    goto end;
  }

  udphdr = (struct udp_hdr *)((u8_t *)p->payload - UDP_HLEN);

  LWIP_DEBUGF(UDP_DEBUG, ("udp_input: received datagram of length %"U16_F"\n", p->tot_len));

  src = ntohs(udphdr->src);
  dest = ntohs(udphdr->dest);

  udp_debug_print(udphdr);

  /* print the UDP source and destination */
  LWIP_DEBUGF(UDP_DEBUG, ("udp (%"U16_F".%"U16_F".%"U16_F".%"U16_F", %"U16_F") <-- (%"U16_F".%"U16_F".%"U16_F".%"U16_F", %"U16_F")\n",
    ip4_addr1(&iphdr->dest), ip4_addr2(&iphdr->dest),
    ip4_addr3(&iphdr->dest), ip4_addr4(&iphdr->dest), ntohs(udphdr->dest),
    ip4_addr1(&iphdr->src), ip4_addr2(&iphdr->src),
    ip4_addr3(&iphdr->src), ip4_addr4(&iphdr->src), ntohs(udphdr->src)));

  local_match = 0;
  uncon_pcb = NULL;
  /* Iterate through the UDP pcb list for a matching pcb */
  for (pcb = udp_pcbs; pcb != NULL; pcb = pcb->next) {
    /* print the PCB local and remote address */
    LWIP_DEBUGF(UDP_DEBUG, ("pcb (%"U16_F".%"U16_F".%"U16_F".%"U16_F", %"U16_F") --- (%"U16_F".%"U16_F".%"U16_F".%"U16_F", %"U16_F")\n",
      ip4_addr1(&pcb->local_ip), ip4_addr2(&pcb->local_ip),
      ip4_addr3(&pcb->local_ip), ip4_addr4(&pcb->local_ip), pcb->local_port,
      ip4_addr1(&pcb->remote_ip), ip4_addr2(&pcb->remote_ip),
      ip4_addr3(&pcb->remote_ip), ip4_addr4(&pcb->remote_ip), pcb->remote_port));

    /* compare PCB local addr+port to UDP destination addr+port */
    if ((pcb->local_port == dest) &&
       (ip_addr_isany(&pcb->local_ip) ||
        ip_addr_cmp(&(pcb->local_ip), &(iphdr->dest)))) {
       local_match = 1;
       if ((uncon_pcb == NULL) && 
           ((pcb->flags & UDP_FLAGS_CONNECTED) == 0)) {
         /* the first unconnected matching PCB */     
         uncon_pcb = pcb;
       }
    }
    /* compare PCB remote addr+port to UDP source addr+port */
    if ((local_match != 0) &&
       (pcb->remote_port == src) &&
       (ip_addr_isany(&pcb->remote_ip) ||
       ip_addr_cmp(&(pcb->remote_ip), &(iphdr->src)))) {
       /* the first fully matching PCB */
      break;
    }
  }
  /* no fully matching pcb found? then look for an unconnected pcb */
  if (pcb == NULL) {
    pcb = uncon_pcb;
  }

  /* Check checksum if this is a match or if it was directed at us. */
  if (pcb != NULL  || ip_addr_cmp(&inp->ip_addr, &iphdr->dest))
    {
    LWIP_DEBUGF(UDP_DEBUG | DBG_TRACE, ("udp_input: calculating checksum\n"));
    pbuf_header(p, UDP_HLEN);
#ifdef IPv6
    if (iphdr->nexthdr == IP_PROTO_UDPLITE) {
#else
    if (IPH_PROTO(iphdr) == IP_PROTO_UDPLITE) {
#endif /* IPv4 */
      /* Do the UDP Lite checksum */
#if CHECKSUM_CHECK_UDP
      if (inet_chksum_pseudo(p, (struct ip_addr *)&(iphdr->src),
         (struct ip_addr *)&(iphdr->dest),
         IP_PROTO_UDPLITE, ntohs(udphdr->len)) != 0) {
  LWIP_DEBUGF(UDP_DEBUG | 2, ("udp_input: UDP Lite datagram discarded due to failing checksum\n"));
  UDP_STATS_INC(udp.chkerr);
  UDP_STATS_INC(udp.drop);
  snmp_inc_udpinerrors();
  pbuf_free(p);
  goto end;
      }
#endif
    } else {
#if CHECKSUM_CHECK_UDP
      if (udphdr->chksum != 0) {
  if (inet_chksum_pseudo(p, (struct ip_addr *)&(iphdr->src),
       (struct ip_addr *)&(iphdr->dest),
        IP_PROTO_UDP, p->tot_len) != 0) {
    LWIP_DEBUGF(UDP_DEBUG | 2, ("udp_input: UDP datagram discarded due to failing checksum\n"));

    UDP_STATS_INC(udp.chkerr);
    UDP_STATS_INC(udp.drop);
    snmp_inc_udpinerrors();
    pbuf_free(p);
    goto end;
  }
      }
#endif
    }
    pbuf_header(p, -UDP_HLEN);
    if (pcb != NULL) {
      snmp_inc_udpindatagrams();
      /* callback */
      if (pcb->recv != NULL)
      {
        pcb->recv(pcb->recv_arg, pcb, p, &(iphdr->src), src);
      }
        } else {
      LWIP_DEBUGF(UDP_DEBUG | DBG_TRACE, ("udp_input: not for us.\n"));

      /* No match was found, send ICMP destination port unreachable unless
      destination address was broadcast/multicast. */

      if (!ip_addr_isbroadcast(&iphdr->dest, inp) &&
          !ip_addr_ismulticast(&iphdr->dest)) {

  /* adjust pbuf pointer */
  p->payload = iphdr;
  icmp_dest_unreach(p, ICMP_DUR_PORT);
      }
      UDP_STATS_INC(udp.proterr);
      UDP_STATS_INC(udp.drop);
    snmp_inc_udpnoports();
      pbuf_free(p);
    }
  } else {
    pbuf_free(p);
  }
  end:

  PERF_STOP("udp_input");
}

/**
 * Send data to a specified address using UDP.
 *
 * @param pcb UDP PCB used to send the data.
 * @param pbuf chain of pbuf's to be sent.
 * @param dst_ip Destination IP address.
 * @param dst_port Destination UDP port.
 *
 * If the PCB already has a remote address association, it will
 * be restored after the data is sent.
 * 
 * @return lwIP error code.
 * - ERR_OK. Successful. No error occured.
 * - ERR_MEM. Out of memory.
 * - ERR_RTE. Could not find route to destination address.
 *
 * @see udp_disconnect() udp_send()
 */
err_t
udp_sendto(struct udp_pcb *pcb, struct pbuf *p,
  struct ip_addr *dst_ip, u16_t dst_port)
{
  err_t err;
  /* temporary space for current PCB remote address */
  struct ip_addr pcb_remote_ip;
  u16_t pcb_remote_port;
  /* remember current remote peer address of PCB */
  pcb_remote_ip.addr = pcb->remote_ip.addr;
  pcb_remote_port = pcb->remote_port;
  /* copy packet destination address to PCB remote peer address */
  pcb->remote_ip.addr = dst_ip->addr;
  pcb->remote_port = dst_port;
  /* send to the packet destination address */
  err = udp_send(pcb, p);
  /* restore PCB remote peer address */
  pcb->remote_ip.addr = pcb_remote_ip.addr;
  pcb->remote_port = pcb_remote_port;
  return err;
}

/**
 * Send data using UDP.
 *
 * @param pcb UDP PCB used to send the data.
 * @param pbuf chain of pbuf's to be sent.
 *
 * @return lwIP error code.
 * - ERR_OK. Successful. No error occured.
 * - ERR_MEM. Out of memory.
 * - ERR_RTE. Could not find route to destination address.
 *
 * @see udp_disconnect() udp_sendto()
 */
err_t
udp_send(struct udp_pcb *pcb, struct pbuf *p)
{
  struct udp_hdr *udphdr;
  struct netif *netif;
  struct ip_addr *src_ip;
  err_t err;
  struct pbuf *q; /* q will be sent down the stack */

  LWIP_DEBUGF(UDP_DEBUG | DBG_TRACE | 3, ("udp_send\n"));

  /* if the PCB is not yet bound to a port, bind it here */
  if (pcb->local_port == 0) {
    LWIP_DEBUGF(UDP_DEBUG | DBG_TRACE | 2, ("udp_send: not yet bound to a port, binding now\n"));
    err = udp_bind(pcb, &pcb->local_ip, pcb->local_port);
    if (err != ERR_OK) {
      LWIP_DEBUGF(UDP_DEBUG | DBG_TRACE | 2, ("udp_send: forced port bind failed\n"));
      return err;
    }
  }
  /* find the outgoing network interface for this packet */
  netif = ip_route(&(pcb->remote_ip));
  /* no outgoing network interface could be found? */
  if (netif == NULL) {
    LWIP_DEBUGF(UDP_DEBUG | 1, ("udp_send: No route to 0x%"X32_F"\n", pcb->remote_ip.addr));
    UDP_STATS_INC(udp.rterr);
    return ERR_RTE;
  }

  /* not enough space to add an UDP header to first pbuf in given p chain? */
  if (pbuf_header(p, UDP_HLEN)) {
    /* allocate header in a seperate new pbuf */
    q = pbuf_alloc(PBUF_IP, UDP_HLEN, PBUF_RAM);
    /* new header pbuf could not be allocated? */
    if (q == NULL) {
      LWIP_DEBUGF(UDP_DEBUG | DBG_TRACE | 2, ("udp_send: could not allocate header\n"));
      return ERR_MEM;
    }
    /* chain header q in front of given pbuf p */