natd.tproj/icmp.c

   1 /*
   2  * Copyright (c) 2000-2002 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25 /*
  26  * natd - Network Address Translation Daemon for FreeBSD.
  27  *
  28  * This software is provided free of charge, with no
  29  * warranty of any kind, either expressed or implied.
  30  * Use at your own risk.
  31  *
  32  * You may copy, modify and distribute this software (icmp.c) freely.
  33  *
  34  * Ari Suutari <suutari@iki.fi>
  35  *
  36  * Based upon:
  37  * $FreeBSD: src/sbin/natd/icmp.c,v 1.6 1999/08/28 00:13:45 peter Exp $
  38  */
  39
  40 #include <stdlib.h>
  41 #include <stdio.h>
  42 #include <unistd.h>
  43 #include <string.h>
  44 #include <ctype.h>
  45
  46 #include <sys/types.h>
  47 #include <sys/socket.h>
  48 #include <sys/time.h>
  49 #include <errno.h>
  50 #include <signal.h>
  51
  52 #include <netdb.h>
  53
  54 #include <netinet/in.h>
  55 #include <netinet/in_systm.h>
  56 #include <netinet/ip.h>
  57 #include <netinet/ip_icmp.h>
  58
  59 #include <alias.h>
  60
  61 #include "natd.h"
  62
  63 int SendNeedFragIcmp (int sock, struct ip* failedDgram, int mtu)
  64 {
  65         char                    icmpBuf[IP_MAXPACKET];
  66         struct ip*              ip;
  67         struct icmp*            icmp;
  68         int                     icmpLen;
  69         int                     failBytes;
  70         int                     failHdrLen;
  71         struct sockaddr_in      addr;
  72         int                     wrote;
  73         struct in_addr          swap;
  74 /*
  75  * Don't send error if packet is
  76  * not the first fragment.
  77  */
  78         if (ntohs (failedDgram->ip_off) & ~(IP_MF | IP_DF))
  79                 return 0;
  80 /*
  81  * Dont respond if failed datagram is ICMP.
  82  */
  83         if (failedDgram->ip_p == IPPROTO_ICMP)
  84                 return 0;
  85 /*
  86  * Start building the message.
  87  */
  88         ip   = (struct ip*) icmpBuf;
  89         icmp = (struct icmp*) (icmpBuf + sizeof (struct ip));
  90 /*
  91  * Complete ICMP part.
  92  */
  93         icmp->icmp_type         = ICMP_UNREACH;
  94         icmp->icmp_code         = ICMP_UNREACH_NEEDFRAG;
  95         icmp->icmp_cksum        = 0;
  96         icmp->icmp_void         = 0;
  97         icmp->icmp_nextmtu      = htons (mtu);
  98 /*
  99  * Copy header + 64 bits of original datagram.
 100  */
 101         failHdrLen = (failedDgram->ip_hl << 2);
 102         failBytes  = failedDgram->ip_len - failHdrLen;
 103         if (failBytes > 8)
 104                 failBytes = 8;
 105
 106         failBytes += failHdrLen;
 107         icmpLen    = ICMP_MINLEN + failBytes;
 108
 109         memcpy (&icmp->icmp_ip, failedDgram, failBytes);
 110 /*
 111  * Calculate checksum.
 112  */
 113         icmp->icmp_cksum = PacketAliasInternetChecksum ((u_short*) icmp,
 114                                                         icmpLen);
 115 /*
 116  * Add IP header using old IP header as template.
 117  */
 118         memcpy (ip, failedDgram, sizeof (struct ip));
 119
 120         ip->ip_v        = 4;
 121         ip->ip_hl       = 5;
 122         ip->ip_len      = htons (sizeof (struct ip) + icmpLen);
 123         ip->ip_p        = IPPROTO_ICMP;
 124         ip->ip_tos      = 0;
 125
 126         swap = ip->ip_dst;
 127         ip->ip_dst = ip->ip_src;
 128         ip->ip_src = swap;
 129
 130         PacketAliasIn ((char*) ip, IP_MAXPACKET);
 131
 132         addr.sin_family         = AF_INET;
 133         addr.sin_addr           = ip->ip_dst;
 134         addr.sin_port           = 0;
 135 /*
 136  * Put packet into processing queue.
 137  */
 138         wrote = sendto (sock,
 139                         icmp,
 140                         icmpLen,
 141                         0,
 142                         (struct sockaddr*) &addr,
 143                         sizeof addr);
 144
 145         if (wrote != icmpLen)
 146                 Warn ("Cannot send ICMP message.");
 147
 148         return 1;
 149 }
 150
 151