Diff: core/ipv4/icmp.c

Revision:

0:51ac1d130fd4

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/ipv4/icmp.c	Fri Jun 22 09:25:39 2012 +0000
@@ -0,0 +1,335 @@
+/**
+ * @file
+ * ICMP - Internet Control Message Protocol
+ *
+ */
+
+/*
+ * 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>
+ *
+ */
+
+/* Some ICMP messages should be passed to the transport protocols. This
+   is not implemented. */
+
+#include "lwip/opt.h"
+
+#if LWIP_ICMP /* don't build if not configured for use in lwipopts.h */
+
+#include "lwip/icmp.h"
+#include "lwip/inet_chksum.h"
+#include "lwip/ip.h"
+#include "lwip/def.h"
+#include "lwip/stats.h"
+#include "lwip/snmp.h"
+
+#include <string.h>
+
+/** Small optimization: set to 0 if incoming PBUF_POOL pbuf always can be
+ * used to modify and send a response packet (and to 1 if this is not the case,
+ * e.g. when link header is stripped of when receiving) */
+#ifndef LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
+#define LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 1
+#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
+
+/* The amount of data from the original packet to return in a dest-unreachable */
+#define ICMP_DEST_UNREACH_DATASIZE 8
+
+static void icmp_send_response(struct pbuf *p, u8_t type, u8_t code);
+
+/**
+ * Processes ICMP input packets, called from ip_input().
+ *
+ * Currently only processes icmp echo requests and sends
+ * out the echo response.
+ *
+ * @param p the icmp echo request packet, p->payload pointing to the ip header
+ * @param inp the netif on which this packet was received
+ */
+void
+icmp_input(struct pbuf *p, struct netif *inp)
+{
+  u8_t type;
+#ifdef LWIP_DEBUG
+  u8_t code;
+#endif /* LWIP_DEBUG */
+  struct icmp_echo_hdr *iecho;
+  struct ip_hdr *iphdr;
+  s16_t hlen;
+
+  ICMP_STATS_INC(icmp.recv);
+  snmp_inc_icmpinmsgs();
+
+
+  iphdr = (struct ip_hdr *)p->payload;
+  hlen = IPH_HL(iphdr) * 4;
+  if (pbuf_header(p, -hlen) || (p->tot_len < sizeof(u16_t)*2)) {
+    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len));
+    goto lenerr;
+  }
+
+  type = *((u8_t *)p->payload);
+#ifdef LWIP_DEBUG
+  code = *(((u8_t *)p->payload)+1);
+#endif /* LWIP_DEBUG */
+  switch (type) {
+  case ICMP_ER:
+    /* This is OK, echo reply might have been parsed by a raw PCB
+       (as obviously, an echo request has been sent, too). */
+    break; 
+  case ICMP_ECHO:
+#if !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING
+    {
+      int accepted = 1;
+#if !LWIP_MULTICAST_PING
+      /* multicast destination address? */
+      if (ip_addr_ismulticast(&current_iphdr_dest)) {
+        accepted = 0;
+      }
+#endif /* LWIP_MULTICAST_PING */
+#if !LWIP_BROADCAST_PING
+      /* broadcast destination address? */
+      if (ip_addr_isbroadcast(&current_iphdr_dest, inp)) {
+        accepted = 0;
+      }
+#endif /* LWIP_BROADCAST_PING */
+      /* broadcast or multicast destination address not acceptd? */
+      if (!accepted) {
+        LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n"));
+        ICMP_STATS_INC(icmp.err);
+        pbuf_free(p);
+        return;
+      }
+    }
+#endif /* !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */
+    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n"));
+    if (p->tot_len < sizeof(struct icmp_echo_hdr)) {
+      LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n"));
+      goto lenerr;
+    }
+    if (inet_chksum_pbuf(p) != 0) {
+      LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n"));
+      pbuf_free(p);
+      ICMP_STATS_INC(icmp.chkerr);
+      snmp_inc_icmpinerrors();
+      return;
+    }
+#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
+    if (pbuf_header(p, (PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
+      /* p is not big enough to contain link headers
+       * allocate a new one and copy p into it
+       */
+      struct pbuf *r;
+      /* switch p->payload to ip header */
+      if (pbuf_header(p, hlen)) {
+        LWIP_ASSERT("icmp_input: moving p->payload to ip header failed\n", 0);
+        goto memerr;
+      }
+      /* allocate new packet buffer with space for link headers */
+      r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM);
+      if (r == NULL) {
+        LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n"));
+        goto memerr;
+      }
+      LWIP_ASSERT("check that first pbuf can hold struct the ICMP header",
+                  (r->len >= hlen + sizeof(struct icmp_echo_hdr)));
+      /* copy the whole packet including ip header */
+      if (pbuf_copy(r, p) != ERR_OK) {
+        LWIP_ASSERT("icmp_input: copying to new pbuf failed\n", 0);
+        goto memerr;
+      }
+      iphdr = (struct ip_hdr *)r->payload;
+      /* switch r->payload back to icmp header */
+      if (pbuf_header(r, -hlen)) {
+        LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
+        goto memerr;
+      }
+      /* free the original p */
+      pbuf_free(p);
+      /* we now have an identical copy of p that has room for link headers */
+      p = r;
+    } else {
+      /* restore p->payload to point to icmp header */
+      if (pbuf_header(p, -(s16_t)(PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
+        LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0);
+        goto memerr;
+      }
+    }
+#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
+    /* At this point, all checks are OK. */
+    /* We generate an answer by switching the dest and src ip addresses,
+     * setting the icmp type to ECHO_RESPONSE and updating the checksum. */
+    iecho = (struct icmp_echo_hdr *)p->payload;
+    ip_addr_copy(iphdr->src, *ip_current_dest_addr());
+    ip_addr_copy(iphdr->dest, *ip_current_src_addr());
+    ICMPH_TYPE_SET(iecho, ICMP_ER);
+    /* adjust the checksum */
+    if (iecho->chksum >= PP_HTONS(0xffffU - (ICMP_ECHO << 8))) {
+      iecho->chksum += PP_HTONS(ICMP_ECHO << 8) + 1;
+    } else {
+      iecho->chksum += PP_HTONS(ICMP_ECHO << 8);
+    }
+
+    /* Set the correct TTL and recalculate the header checksum. */
+    IPH_TTL_SET(iphdr, ICMP_TTL);
+    IPH_CHKSUM_SET(iphdr, 0);
+#if CHECKSUM_GEN_IP
+    IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN));
+#endif /* CHECKSUM_GEN_IP */
+
+    ICMP_STATS_INC(icmp.xmit);
+    /* increase number of messages attempted to send */
+    snmp_inc_icmpoutmsgs();
+    /* increase number of echo replies attempted to send */
+    snmp_inc_icmpoutechoreps();
+
+    if(pbuf_header(p, hlen)) {
+      LWIP_ASSERT("Can't move over header in packet", 0);
+    } else {
+      err_t ret;
+      /* send an ICMP packet, src addr is the dest addr of the curren packet */
+      ret = ip_output_if(p, ip_current_dest_addr(), IP_HDRINCL,
+                   ICMP_TTL, 0, IP_PROTO_ICMP, inp);
+      if (ret != ERR_OK) {
+        LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %c.\n", ret));
+      }
+    }
+    break;
+  default:
+    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n", 
+                (s16_t)type, (s16_t)code));
+    ICMP_STATS_INC(icmp.proterr);
+    ICMP_STATS_INC(icmp.drop);
+  }
+  pbuf_free(p);
+  return;
+lenerr:
+  pbuf_free(p);
+  ICMP_STATS_INC(icmp.lenerr);
+  snmp_inc_icmpinerrors();
+  return;
+#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
+memerr:
+  pbuf_free(p);
+  ICMP_STATS_INC(icmp.err);
+  snmp_inc_icmpinerrors();
+  return;
+#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
+}
+
+/**
+ * Send an icmp 'destination unreachable' packet, called from ip_input() if
+ * the transport layer protocol is unknown and from udp_input() if the local
+ * port is not bound.
+ *
+ * @param p the input packet for which the 'unreachable' should be sent,
+ *          p->payload pointing to the IP header
+ * @param t type of the 'unreachable' packet
+ */
+void
+icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)
+{
+  icmp_send_response(p, ICMP_DUR, t);
+}
+
+#if IP_FORWARD || IP_REASSEMBLY
+/**
+ * Send a 'time exceeded' packet, called from ip_forward() if TTL is 0.
+ *
+ * @param p the input packet for which the 'time exceeded' should be sent,
+ *          p->payload pointing to the IP header
+ * @param t type of the 'time exceeded' packet
+ */
+void
+icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
+{
+  icmp_send_response(p, ICMP_TE, t);
+}
+
+#endif /* IP_FORWARD || IP_REASSEMBLY */
+
+/**
+ * Send an icmp packet in response to an incoming packet.
+ *
+ * @param p the input packet for which the 'unreachable' should be sent,
+ *          p->payload pointing to the IP header
+ * @param type Type of the ICMP header
+ * @param code Code of the ICMP header
+ */
+static void
+icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
+{
+  struct pbuf *q;
+  struct ip_hdr *iphdr;
+  /* we can use the echo header here */
+  struct icmp_echo_hdr *icmphdr;
+  ip_addr_t iphdr_src;
+
+  /* ICMP header + IP header + 8 bytes of data */
+  q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
+                 PBUF_RAM);
+  if (q == NULL) {
+    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
+    return;
+  }
+  LWIP_ASSERT("check that first pbuf can hold icmp message",
+             (q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
+
+  iphdr = (struct ip_hdr *)p->payload;
+  LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
+  ip_addr_debug_print(ICMP_DEBUG, &(iphdr->src));
+  LWIP_DEBUGF(ICMP_DEBUG, (" to "));
+  ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
+  LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
+
+  icmphdr = (struct icmp_echo_hdr *)q->payload;
+  icmphdr->type = type;
+  icmphdr->code = code;
+  icmphdr->id = 0;
+  icmphdr->seqno = 0;
+
+  /* copy fields from original packet */
+  SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload,
+          IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
+
+  /* calculate checksum */
+  icmphdr->chksum = 0;
+  icmphdr->chksum = inet_chksum(icmphdr, q->len);
+  ICMP_STATS_INC(icmp.xmit);
+  /* increase number of messages attempted to send */
+  snmp_inc_icmpoutmsgs();
+  /* increase number of destination unreachable messages attempted to send */
+  snmp_inc_icmpouttimeexcds();
+  ip_addr_copy(iphdr_src, iphdr->src);
+  ip_output(q, NULL, &iphdr_src, ICMP_TTL, 0, IP_PROTO_ICMP);
+  pbuf_free(q);
+}
+
+#endif /* LWIP_ICMP */