natd.tproj/icmp.c

   1 /*
   2  * Copyright (c) 2000-2002 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23  * natd - Network Address Translation Daemon for FreeBSD.
  24  *
  25  * This software is provided free of charge, with no
  26  * warranty of any kind, either expressed or implied.
  27  * Use at your own risk.
  28  *
  29  * You may copy, modify and distribute this software (icmp.c) freely.
  30  *
  31  * Ari Suutari <suutari@iki.fi>
  32  *
  33  * Based upon:
  34  * $FreeBSD: src/sbin/natd/icmp.c,v 1.6 1999/08/28 00:13:45 peter Exp $
  35  */
  36
  37 #include <stdlib.h>
  38 #include <stdio.h>
  39 #include <unistd.h>
  40 #include <string.h>
  41 #include <ctype.h>
  42
  43 #include <sys/types.h>
  44 #include <sys/socket.h>
  45 #include <sys/time.h>
  46 #include <errno.h>
  47 #include <signal.h>
  48
  49 #include <netdb.h>
  50
  51 #include <netinet/in.h>
  52 #include <netinet/in_systm.h>
  53 #include <netinet/ip.h>
  54 #include <netinet/ip_icmp.h>
  55
  56 #include <alias.h>
  57
  58 #include "natd.h"
  59
  60 int SendNeedFragIcmp (int sock, struct ip* failedDgram, int mtu)
  61 {
  62         char                    icmpBuf[IP_MAXPACKET];
  63         struct ip*              ip;
  64         struct icmp*            icmp;
  65         int                     icmpLen;
  66         int                     failBytes;
  67         int                     failHdrLen;
  68         struct sockaddr_in      addr;
  69         int                     wrote;
  70         struct in_addr          swap;
  71 /*
  72  * Don't send error if packet is
  73  * not the first fragment.
  74  */
  75         if (ntohs (failedDgram->ip_off) & ~(IP_MF | IP_DF))
  76                 return 0;
  77 /*
  78  * Dont respond if failed datagram is ICMP.
  79  */
  80         if (failedDgram->ip_p == IPPROTO_ICMP)
  81                 return 0;
  82 /*
  83  * Start building the message.
  84  */
  85         ip   = (struct ip*) icmpBuf;
  86         icmp = (struct icmp*) (icmpBuf + sizeof (struct ip));
  87 /*
  88  * Complete ICMP part.
  89  */
  90         icmp->icmp_type         = ICMP_UNREACH;
  91         icmp->icmp_code         = ICMP_UNREACH_NEEDFRAG;
  92         icmp->icmp_cksum        = 0;
  93         icmp->icmp_void         = 0;
  94         icmp->icmp_nextmtu      = htons (mtu);
  95 /*
  96  * Copy header + 64 bits of original datagram.
  97  */
  98         failHdrLen = (failedDgram->ip_hl << 2);
  99         failBytes  = failedDgram->ip_len - failHdrLen;
 100         if (failBytes > 8)
 101                 failBytes = 8;
 102
 103         failBytes += failHdrLen;
 104         icmpLen    = ICMP_MINLEN + failBytes;
 105
 106         memcpy (&icmp->icmp_ip, failedDgram, failBytes);
 107 /*
 108  * Calculate checksum.
 109  */
 110         icmp->icmp_cksum = PacketAliasInternetChecksum ((u_short*) icmp,
 111                                                         icmpLen);
 112 /*
 113  * Add IP header using old IP header as template.
 114  */
 115         memcpy (ip, failedDgram, sizeof (struct ip));
 116
 117         ip->ip_v        = 4;
 118         ip->ip_hl       = 5;
 119         ip->ip_len      = htons (sizeof (struct ip) + icmpLen);
 120         ip->ip_p        = IPPROTO_ICMP;
 121         ip->ip_tos      = 0;
 122
 123         swap = ip->ip_dst;
 124         ip->ip_dst = ip->ip_src;
 125         ip->ip_src = swap;
 126
 127         PacketAliasIn ((char*) ip, IP_MAXPACKET);
 128
 129         addr.sin_family         = AF_INET;
 130         addr.sin_addr           = ip->ip_dst;
 131         addr.sin_port           = 0;
 132 /*
 133  * Put packet into processing queue.
 134  */
 135         wrote = sendto (sock,
 136                         icmp,
 137                         icmpLen,
 138                         0,
 139                         (struct sockaddr*) &addr,
 140                         sizeof addr);
 141
 142         if (wrote != icmpLen)
 143                 Warn ("Cannot send ICMP message.");
 144
 145         return 1;
 146 }
 147
 148