natd.tproj/icmp.c

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