xref: /freebsd/usr.sbin/ipfwpcap/ipfwpcap.c (revision 734e82fe33aa764367791a7d603b383996c6b40b) 
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 
25 #include <stdio.h>
26 #include <errno.h>
27 #include <paths.h>
28 #include <fcntl.h>
29 #include <signal.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #include <unistd.h>
33 #include <sys/types.h>
34 #include <sys/time.h>
35 #include <sys/param.h>		/* for MAXPATHLEN */
36 #include <sys/socket.h>
37 #include <netinet/in.h>
38 
39 #include <netinet/in_systm.h>	/* for IP_MAXPACKET */
40 #include <netinet/ip.h>		/* for IP_MAXPACKET */
41 
42 #include <net/bpf.h>
43 
44 /* XXX normally defined in config.h */
45 #define HAVE_STRLCPY 1
46 #define HAVE_SNPRINTF 1
47 #define HAVE_VSNPRINTF 1
48 #include <pcap-int.h>	/* see pcap(3) and /usr/src/contrib/libpcap/. */
49 
50 #ifdef IP_MAXPACKET
51 #define BUFMAX	IP_MAXPACKET
52 #else
53 #define BUFMAX	65535
54 #endif
55 
56 #ifndef MAXPATHLEN
57 #define MAXPATHLEN	1024
58 #endif
59 
60 static int debug = 0;
61 static int reflect = 0;		/* 1 == write packet back to socket. */
62 
63 static ssize_t totbytes = 0, maxbytes = 0;
64 static ssize_t totpkts = 0, maxpkts = 0;
65 
66 static char *prog = NULL;
67 static char pidfile[MAXPATHLEN];
68 
69 /*
70  * tidy up.
71  */
72 static void
73 quit(int sig)
74 {
75 	(void) unlink(pidfile);
76 	exit(sig);
77 }
78 
79 /*
80  * do the "paper work"
81  *	- save my own pid in /var/run/$0.{port#}.pid
82  */
83 static void
84 okay(int pn)
85 {
86 	int fd;
87 	char *p, numbuf[80];
88 
89 	if (pidfile[0] == '\0') {
90 		p = strrchr(prog, '/');
91 		p = (p == NULL) ? prog : p + 1;
92 
93 		snprintf(pidfile, sizeof pidfile,
94 			"%s%s.%d.pid", _PATH_VARRUN, p, pn);
95 	}
96 
97 	fd = open(pidfile, O_WRONLY|O_CREAT|O_EXCL, 0644);
98 	if (fd < 0) {
99 		perror(pidfile);
100 		exit(21);
101 	}
102 
103 	siginterrupt(SIGTERM, 1);
104 	siginterrupt(SIGHUP, 1);
105 	signal(SIGTERM, quit);
106 	signal(SIGHUP, quit);
107 	signal(SIGINT, quit);
108 
109 	snprintf(numbuf, sizeof numbuf, "%d\n", getpid());
110 	if (write(fd, numbuf, strlen(numbuf)) < 0) {
111 		perror(pidfile);
112 		quit(23);
113 	}
114 	(void) close(fd);
115 }
116 
117 static void
118 usage(void)
119 {
120 	fprintf(stderr,
121 "\n"
122 "usage:\n"
123 "    %s [-dr] [-b maxbytes] [-p maxpkts] [-P pidfile] portnum dumpfile\n"
124 "\n"
125 "where:\n"
126 "	'-d'  = enable debugging messages.\n"
127 "	'-r'  = reflect. write packets back to the divert socket.\n"
128 "		(ie. simulate the original intent of \"ipfw tee\").\n"
129 "	'-rr' = indicate that it is okay to quit if packet-count or\n"
130 "		byte-count limits are reached (see the NOTE below\n"
131 "		about what this implies).\n"
132 "	'-b bytcnt'   = stop dumping after {bytcnt} bytes.\n"
133 "	'-p pktcnt'   = stop dumping after {pktcnt} packets.\n"
134 "	'-P pidfile'  = alternate file to store the PID\n"
135 "			(default: /var/run/%s.{portnum}.pid).\n"
136 "\n"
137 "	portnum  = divert(4) socket port number.\n"
138 "	dumpfile = file to write captured packets (tcpdump format).\n"
139 "		   (specify '-' to write packets to stdout).\n"
140 "\n"
141 "The '-r' option should not be necessary, but because \"ipfw tee\" is broken\n"
142 "(see BUGS in ipfw(8) for details) this feature can be used along with\n"
143 "an \"ipfw divert\" rule to simulate the original intent of \"ipfw tee\".\n"
144 "\n"
145 "NOTE: With an \"ipfw divert\" rule, diverted packets will silently\n"
146 "      disappear if there is nothing listening to the divert socket.\n"
147 "\n", prog, prog);
148 	exit(1);
149 }
150 
151 int
152 main(int ac, char *av[])
153 {
154 	int r, sd, portnum, l;
155         struct sockaddr_in sin;
156 	int errflg = 0;
157 
158 	int nfd;
159 	fd_set rds;
160 
161 	ssize_t nr;
162 
163 	char *dumpf, buf[BUFMAX];
164 
165 	pcap_t *p;
166 	pcap_dumper_t *dp;
167 	struct pcap_pkthdr phd;
168 
169 	prog = av[0];
170 
171 	while ((r = getopt(ac, av, "drb:p:P:")) != -1) {
172 		switch (r) {
173 		case 'd':
174 			debug++;
175 			break;
176 		case 'r':
177 			reflect++;
178 			break;
179 		case 'b':
180 			maxbytes = (ssize_t) atol(optarg);
181 			break;
182 		case 'p':
183 			maxpkts = (ssize_t) atoi(optarg);
184 			break;
185 		case 'P':
186 			strcpy(pidfile, optarg);
187 			break;
188 		case '?':
189 		default:
190 			errflg++;
191 			break;
192 		}
193 	}
194 
195 	if ((ac - optind) != 2 || errflg)
196 		usage();
197 
198 	portnum = atoi(av[optind++]);
199 	dumpf = av[optind];
200 
201 if (debug) fprintf(stderr, "bind to %d.\ndump to '%s'.\n", portnum, dumpf);
202 
203 	if ((r = socket(PF_DIVERT, SOCK_RAW, 0)) == -1) {
204 		perror("socket(DIVERT)");
205 		exit(2);
206 	}
207 	sd = r;
208 
209 	sin.sin_port = htons(portnum);
210 	sin.sin_family = AF_INET;
211 	sin.sin_addr.s_addr = INADDR_ANY;
212 
213 	if (bind(sd, (struct sockaddr *)&sin, sizeof(sin)) == -1) {
214 		perror("bind(divert)");
215 		exit(3);
216 	}
217 
218 	p = pcap_open_dead(DLT_RAW, BUFMAX);
219 	dp = pcap_dump_open(p, dumpf);
220 	if (dp == NULL) {
221 		pcap_perror(p, dumpf);
222 		exit(4);
223 	}
224 
225 	okay(portnum);
226 
227 	nfd = sd + 1;
228 	for (;;) {
229 		FD_ZERO(&rds);
230 		FD_SET(sd, &rds);
231 
232 		r = select(nfd, &rds, NULL, NULL, NULL);
233 		if (r == -1) {
234 			if (errno == EINTR) continue;
235 			perror("select");
236 			quit(11);
237 		}
238 
239 		if (!FD_ISSET(sd, &rds))
240 			/* hmm. no work. */
241 			continue;
242 
243 		/*
244 		 * use recvfrom(3 and sendto(3) as in natd(8).
245 		 * see /usr/src/sbin/natd/natd.c
246 		 * see ipfw(8) about using 'divert' and 'tee'.
247 		 */
248 
249 		/*
250 		 * read packet.
251 		 */
252 		l = sizeof(sin);
253 		nr = recvfrom(sd, buf, sizeof(buf), 0, (struct sockaddr *)&sin, &l);
254 if (debug) fprintf(stderr, "recvfrom(%d) = %zd (%d)\n", sd, nr, l);
255 		if (nr < 0 && errno != EINTR) {
256 			perror("recvfrom(sd)");
257 			quit(12);
258 		}
259 		if (nr <= 0) continue;
260 
261 		if (reflect) {
262 			/*
263 			 * write packet back so it can continue
264 			 * being processed by any further IPFW rules.
265 			 */
266 			l = sizeof(sin);
267 			r = sendto(sd, buf, nr, 0, (struct sockaddr *)&sin, l);
268 if (debug) fprintf(stderr, "  sendto(%d) = %d\n", sd, r);
269 			if (r < 0) { perror("sendto(sd)"); quit(13); }
270 		}
271 
272 		/*
273 		 * check maximums, if any.
274 		 * but don't quit if must continue reflecting packets.
275 		 */
276 		if (maxpkts) {
277 			totpkts++;
278 			if (totpkts > maxpkts) {
279 				if (reflect == 1) continue;
280 				quit(0);
281 			}
282 		}
283 		if (maxbytes) {
284 			totbytes += nr;
285 			if (totbytes > maxbytes) {
286 				if (reflect == 1) continue;
287 				quit(0);
288 			}
289 		}
290 
291 		/*
292 		 * save packet in tcpdump(1) format. see pcap(3).
293 		 * divert packets are fully assembled. see ipfw(8).
294 		 */
295 		(void) gettimeofday(&(phd.ts), NULL);
296 		phd.caplen = phd.len = nr;
297 		pcap_dump((u_char *)dp, &phd, buf);
298 		if (ferror((FILE *)dp)) { perror(dumpf); quit(14); }
299 		(void) fflush((FILE *)dp);
300 	}
301 
302 	quit(0);
303 }
304