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lwip/src/core/ipv4/icmp.c

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/**
* @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;
ip_addr_t tmpaddr;
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(&iphdr->dest)) {
accepted = 0;
}
#endif /* LWIP_MULTICAST_PING */
#if !LWIP_BROADCAST_PING
/* broadcast destination address? */
if (ip_addr_isbroadcast(&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(tmpaddr, iphdr->src);
ip_addr_copy(iphdr->src, iphdr->dest);
ip_addr_copy(iphdr->dest, tmpaddr);
ICMPH_TYPE_SET(iecho, ICMP_ER);
/* adjust the checksum */
if (iecho->chksum >= htons(0xffff - (ICMP_ECHO << 8))) {
iecho->chksum += htons(ICMP_ECHO << 8) + 1;
} else {
iecho->chksum += 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;
ret = ip_output_if(p, &(iphdr->src), 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;
/* 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_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP);
pbuf_free(q);
}
#endif /* LWIP_ICMP */
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