1/*
2 * copy diverted (or tee'd) packets to a file in 'tcpdump' format
3 * (ie. this uses the '-lpcap' routines).
4 *
5 * example usage:
6 *	# ipfwpcap -r 8091 divt.log &
7 *	# ipfw add 2864 divert 8091 ip from 128.432.53.82 to any
8 *	# ipfw add 2864 divert 8091 ip from any to 128.432.53.82
9 *
10 *   the resulting dump file can be read with ...
11 *	# tcpdump -nX -r divt.log
12 */
13/*
14 * Written by P Kern { pkern [AT] cns.utoronto.ca }
15 *
16 * Copyright (c) 2004 University of Toronto. All rights reserved.
17 * Anyone may use or copy this software except that this copyright
18 * notice remain intact and that credit is given where it is due.
19 * The University of Toronto and the author make no warranty and
20 * accept no liability for this software.
21 *
22 * From: Header: /local/src/local.lib/SRC/ipfwpcap/RCS/ipfwpcap.c,v 1.4 2004/01/15 16:19:07 pkern Exp
23 *
24 * $FreeBSD$
25 */
26
27#include <stdio.h>
28#include <errno.h>
29#include <paths.h>
30#include <fcntl.h>
31#include <signal.h>
32#include <stdlib.h>
33#include <string.h>
34#include <unistd.h>
35#include <sys/types.h>
36#include <sys/time.h>
37#include <sys/param.h>		/* for MAXPATHLEN */
38#include <sys/socket.h>
39#include <netinet/in.h>
40
41#include <netinet/in_systm.h>	/* for IP_MAXPACKET */
42#include <netinet/ip.h>		/* for IP_MAXPACKET */
43
44#include <net/bpf.h>
45
46/* XXX normally defined in config.h */
47#define HAVE_STRLCPY 1
48#define HAVE_SNPRINTF 1
49#define HAVE_VSNPRINTF 1
50#include <pcap-int.h>	/* see pcap(3) and /usr/src/contrib/libpcap/. */
51
52#ifdef IP_MAXPACKET
53#define BUFMAX	IP_MAXPACKET
54#else
55#define BUFMAX	65535
56#endif
57
58#ifndef MAXPATHLEN
59#define MAXPATHLEN	1024
60#endif
61
62static int debug = 0;
63static int reflect = 0;		/* 1 == write packet back to socket. */
64
65static ssize_t totbytes = 0, maxbytes = 0;
66static ssize_t totpkts = 0, maxpkts = 0;
67
68static char *prog = NULL;
69static char pidfile[MAXPATHLEN];
70
71/*
72 * tidy up.
73 */
74static void
75quit(int sig)
76{
77	(void) unlink(pidfile);
78	exit(sig);
79}
80
81/*
82 * do the "paper work"
83 *	- save my own pid in /var/run/$0.{port#}.pid
84 */
85static void
86okay(int pn)
87{
88	int fd;
89	char *p, numbuf[80];
90
91	if (pidfile[0] == '\0') {
92		p = strrchr(prog, '/');
93		p = (p == NULL) ? prog : p + 1;
94
95		snprintf(pidfile, sizeof pidfile,
96			"%s%s.%d.pid", _PATH_VARRUN, p, pn);
97	}
98
99	fd = open(pidfile, O_WRONLY|O_CREAT|O_EXCL, 0644);
100	if (fd < 0) {
101		perror(pidfile);
102		exit(21);
103	}
104
105	siginterrupt(SIGTERM, 1);
106	siginterrupt(SIGHUP, 1);
107	signal(SIGTERM, quit);
108	signal(SIGHUP, quit);
109	signal(SIGINT, quit);
110
111	snprintf(numbuf, sizeof numbuf, "%d\n", getpid());
112	if (write(fd, numbuf, strlen(numbuf)) < 0) {
113		perror(pidfile);
114		quit(23);
115	}
116	(void) close(fd);
117}
118
119static void
120usage(void)
121{
122	fprintf(stderr,
123"\n"
124"usage:\n"
125"    %s [-dr] [-b maxbytes] [-p maxpkts] [-P pidfile] portnum dumpfile\n"
126"\n"
127"where:\n"
128"	'-d'  = enable debugging messages.\n"
129"	'-r'  = reflect. write packets back to the divert socket.\n"
130"		(ie. simulate the original intent of \"ipfw tee\").\n"
131"	'-rr' = indicate that it is okay to quit if packet-count or\n"
132"		byte-count limits are reached (see the NOTE below\n"
133"		about what this implies).\n"
134"	'-b bytcnt'   = stop dumping after {bytcnt} bytes.\n"
135"	'-p pktcnt'   = stop dumping after {pktcnt} packets.\n"
136"	'-P pidfile'  = alternate file to store the PID\n"
137"			(default: /var/run/%s.{portnum}.pid).\n"
138"\n"
139"	portnum  = divert(4) socket port number.\n"
140"	dumpfile = file to write captured packets (tcpdump format).\n"
141"		   (specify '-' to write packets to stdout).\n"
142"\n"
143"The '-r' option should not be necessary, but because \"ipfw tee\" is broken\n"
144"(see BUGS in ipfw(8) for details) this feature can be used along with\n"
145"an \"ipfw divert\" rule to simulate the original intent of \"ipfw tee\".\n"
146"\n"
147"NOTE: With an \"ipfw divert\" rule, diverted packets will silently\n"
148"      disappear if there is nothing listening to the divert socket.\n"
149"\n", prog, prog);
150	exit(1);
151}
152
153int
154main(int ac, char *av[])
155{
156	int r, sd, portnum, l;
157        struct sockaddr_in sin;
158	int errflg = 0;
159
160	int nfd;
161	fd_set rds;
162
163	ssize_t nr;
164
165	char *dumpf, buf[BUFMAX];
166
167	pcap_t *p;
168	pcap_dumper_t *dp;
169	struct pcap_pkthdr phd;
170
171	prog = av[0];
172
173	while ((r = getopt(ac, av, "drb:p:P:")) != -1) {
174		switch (r) {
175		case 'd':
176			debug++;
177			break;
178		case 'r':
179			reflect++;
180			break;
181		case 'b':
182			maxbytes = (ssize_t) atol(optarg);
183			break;
184		case 'p':
185			maxpkts = (ssize_t) atoi(optarg);
186			break;
187		case 'P':
188			strcpy(pidfile, optarg);
189			break;
190		case '?':
191		default:
192			errflg++;
193			break;
194		}
195	}
196
197	if ((ac - optind) != 2 || errflg)
198		usage();
199
200	portnum = atoi(av[optind++]);
201	dumpf = av[optind];
202
203if (debug) fprintf(stderr, "bind to %d.\ndump to '%s'.\n", portnum, dumpf);
204
205	if ((r = socket(PF_INET, SOCK_RAW, IPPROTO_DIVERT)) == -1) {
206		perror("socket(DIVERT)");
207		exit(2);
208	}
209	sd = r;
210
211	sin.sin_port = htons(portnum);
212	sin.sin_family = AF_INET;
213	sin.sin_addr.s_addr = INADDR_ANY;
214
215	if (bind(sd, (struct sockaddr *)&sin, sizeof(sin)) == -1) {
216		perror("bind(divert)");
217		exit(3);
218	}
219
220	p = pcap_open_dead(DLT_RAW, BUFMAX);
221	dp = pcap_dump_open(p, dumpf);
222	if (dp == NULL) {
223		pcap_perror(p, dumpf);
224		exit(4);
225	}
226
227	okay(portnum);
228
229	nfd = sd + 1;
230	for (;;) {
231		FD_ZERO(&rds);
232		FD_SET(sd, &rds);
233
234		r = select(nfd, &rds, NULL, NULL, NULL);
235		if (r == -1) {
236			if (errno == EINTR) continue;
237			perror("select");
238			quit(11);
239		}
240
241		if (!FD_ISSET(sd, &rds))
242			/* hmm. no work. */
243			continue;
244
245		/*
246		 * use recvfrom(3 and sendto(3) as in natd(8).
247		 * see /usr/src/sbin/natd/natd.c
248		 * see ipfw(8) about using 'divert' and 'tee'.
249		 */
250
251		/*
252		 * read packet.
253		 */
254		l = sizeof(sin);
255		nr = recvfrom(sd, buf, sizeof(buf), 0, (struct sockaddr *)&sin, &l);
256if (debug) fprintf(stderr, "recvfrom(%d) = %zd (%d)\n", sd, nr, l);
257		if (nr < 0 && errno != EINTR) {
258			perror("recvfrom(sd)");
259			quit(12);
260		}
261		if (nr <= 0) continue;
262
263		if (reflect) {
264			/*
265			 * write packet back so it can continue
266			 * being processed by any further IPFW rules.
267			 */
268			l = sizeof(sin);
269			r = sendto(sd, buf, nr, 0, (struct sockaddr *)&sin, l);
270if (debug) fprintf(stderr, "  sendto(%d) = %d\n", sd, r);
271			if (r < 0) { perror("sendto(sd)"); quit(13); }
272		}
273
274		/*
275		 * check maximums, if any.
276		 * but don't quit if must continue reflecting packets.
277		 */
278		if (maxpkts) {
279			totpkts++;
280			if (totpkts > maxpkts) {
281				if (reflect == 1) continue;
282				quit(0);
283			}
284		}
285		if (maxbytes) {
286			totbytes += nr;
287			if (totbytes > maxbytes) {
288				if (reflect == 1) continue;
289				quit(0);
290			}
291		}
292
293		/*
294		 * save packet in tcpdump(1) format. see pcap(3).
295		 * divert packets are fully assembled. see ipfw(8).
296		 */
297		(void) gettimeofday(&(phd.ts), NULL);
298		phd.caplen = phd.len = nr;
299		pcap_dump((u_char *)dp, &phd, buf);
300		if (ferror((FILE *)dp)) { perror(dumpf); quit(14); }
301		(void) fflush((FILE *)dp);
302	}
303
304	quit(0);
305}
306