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