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126 lines
2.5 KiB
C
126 lines
2.5 KiB
C
/*
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* This software is provided free of charge, with no
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* warranty of any kind, either expressed or implied.
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* Use at your own risk.
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*
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* You may copy, modify and distribute this software freely.
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*
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* Ari Suutari <suutari@iki.fi>
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*
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* $Id: icmp.c,v 1.3 1997/12/27 19:31:11 alex Exp $
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <string.h>
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#include <ctype.h>
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <sys/time.h>
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#include <errno.h>
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#include <signal.h>
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#include <netdb.h>
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#include <netinet/in.h>
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#include <netinet/in_systm.h>
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#include <netinet/ip.h>
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#include <netinet/ip_icmp.h>
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#include <machine/in_cksum.h>
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#include <alias.h>
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#include "natd.h"
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int SendNeedFragIcmp (int sock, struct ip* failedDgram, int mtu)
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{
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char icmpBuf[IP_MAXPACKET];
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struct ip* ip;
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struct icmp* icmp;
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int icmpLen;
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int failBytes;
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int failHdrLen;
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struct sockaddr_in addr;
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int wrote;
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struct in_addr swap;
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/*
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* Don't send error if packet is
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* not the first fragment.
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*/
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if (ntohs (failedDgram->ip_off) & ~(IP_MF | IP_DF))
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return 0;
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/*
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* Dont respond if failed datagram is ICMP.
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*/
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if (failedDgram->ip_p == IPPROTO_ICMP)
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return 0;
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/*
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* Start building the message.
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*/
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ip = (struct ip*) icmpBuf;
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icmp = (struct icmp*) (icmpBuf + sizeof (struct ip));
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/*
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* Complete ICMP part.
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*/
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icmp->icmp_type = ICMP_UNREACH;
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icmp->icmp_code = ICMP_UNREACH_NEEDFRAG;
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icmp->icmp_cksum = 0;
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icmp->icmp_void = 0;
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icmp->icmp_nextmtu = htons (mtu);
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/*
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* Copy header + 64 bits of original datagram.
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*/
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failHdrLen = (failedDgram->ip_hl << 2);
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failBytes = failedDgram->ip_len - failHdrLen;
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if (failBytes > 8)
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failBytes = 8;
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failBytes += failHdrLen;
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icmpLen = ICMP_MINLEN + failBytes;
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memcpy (&icmp->icmp_ip, failedDgram, failBytes);
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/*
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* Calculate checksum.
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*/
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icmp->icmp_cksum = PacketAliasInternetChecksum ((u_short*) icmp,
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icmpLen);
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/*
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* Add IP header using old IP header as template.
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*/
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memcpy (ip, failedDgram, sizeof (struct ip));
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ip->ip_v = 4;
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ip->ip_hl = 5;
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ip->ip_len = htons (sizeof (struct ip) + icmpLen);
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ip->ip_p = IPPROTO_ICMP;
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ip->ip_tos = 0;
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swap = ip->ip_dst;
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ip->ip_dst = ip->ip_src;
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ip->ip_src = swap;
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PacketAliasIn ((char*) ip, IP_MAXPACKET);
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addr.sin_family = AF_INET;
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addr.sin_addr = ip->ip_dst;
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addr.sin_port = 0;
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/*
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* Put packet into processing queue.
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*/
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wrote = sendto (sock,
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icmp,
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icmpLen,
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0,
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(struct sockaddr*) &addr,
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sizeof addr);
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if (wrote != icmpLen)
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Warn ("Cannot send ICMP message.");
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return 1;
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}
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