icmp.c revision 32026 
1/*
2 * $Id$
3 */
4
5#include <stdlib.h>
6#include <stdio.h>
7#include <unistd.h>
8#include <string.h>
9#include <ctype.h>
10
11#include <sys/types.h>
12#include <sys/socket.h>
13#include <sys/time.h>
14#include <errno.h>
15#include <signal.h>
16
17#include <netdb.h>
18
19#include <netinet/in.h>
20#include <netinet/in_systm.h>
21#include <netinet/ip.h>
22#include <netinet/ip_icmp.h>
23#include <machine/in_cksum.h>
24
25#include <alias.h>
26
27#include "natd.h"
28
29int SendNeedFragIcmp (int sock, struct ip* failedDgram, int mtu)
30{
31	char			icmpBuf[IP_MAXPACKET];
32	struct ip*		ip;
33	struct icmp*		icmp;
34	int			icmpLen;
35	int			failBytes;
36	int			failHdrLen;
37	struct sockaddr_in	addr;
38	int			wrote;
39	struct in_addr		swap;
40/*
41 * Don't send error if packet is
42 * not the first fragment.
43 */
44	if (ntohs (failedDgram->ip_off) & ~(IP_MF | IP_DF))
45		return 0;
46/*
47 * Dont respond if failed datagram is ICMP.
48 */
49	if (failedDgram->ip_p == IPPROTO_ICMP)
50		return 0;
51/*
52 * Start building the message.
53 */
54	ip   = (struct ip*) icmpBuf;
55	icmp = (struct icmp*) (icmpBuf + sizeof (struct ip));
56/*
57 * Complete ICMP part.
58 */
59	icmp->icmp_type  	= ICMP_UNREACH;
60	icmp->icmp_code		= ICMP_UNREACH_NEEDFRAG;
61	icmp->icmp_cksum	= 0;
62	icmp->icmp_void		= 0;
63	icmp->icmp_nextmtu	= htons (mtu);
64/*
65 * Copy header + 64 bits of original datagram.
66 */
67	failHdrLen = (failedDgram->ip_hl << 2);
68	failBytes  = failedDgram->ip_len - failHdrLen;
69	if (failBytes > 8)
70		failBytes = 8;
71
72	failBytes += failHdrLen;
73	icmpLen    = ICMP_MINLEN + failBytes;
74
75	memcpy (&icmp->icmp_ip, failedDgram, failBytes);
76/*
77 * Calculate checksum.
78 */
79	icmp->icmp_cksum = PacketAliasInternetChecksum ((u_short*) icmp,
80							icmpLen);
81/*
82 * Add IP header using old IP header as template.
83 */
84	memcpy (ip, failedDgram, sizeof (struct ip));
85
86	ip->ip_v	= 4;
87	ip->ip_hl	= 5;
88	ip->ip_len	= htons (sizeof (struct ip) + icmpLen);
89	ip->ip_p	= IPPROTO_ICMP;
90	ip->ip_tos	= 0;
91
92	swap = ip->ip_dst;
93	ip->ip_dst = ip->ip_src;
94	ip->ip_src = swap;
95
96	PacketAliasIn ((char*) ip, IP_MAXPACKET);
97
98	addr.sin_family		= AF_INET;
99	addr.sin_addr		= ip->ip_dst;
100	addr.sin_port		= 0;
101/*
102 * Put packet into processing queue.
103 */
104	wrote = sendto (sock,
105		        icmp,
106	    		icmpLen,
107	    		0,
108	    		(struct sockaddr*) &addr,
109	    		sizeof addr);
110
111	if (wrote != icmpLen)
112		Warn ("Cannot send ICMP message.");
113
114	return 1;
115}
116
117
118