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
62 static int debug = 0;
63 static int reflect = 0; /* 1 == write packet back to socket. */
64
65 static ssize_t totbytes = 0, maxbytes = 0;
66 static ssize_t totpkts = 0, maxpkts = 0;
67
68 static char *prog = NULL;
69 static char pidfile[MAXPATHLEN];
70
71 /*
72 * tidy up.
73 */
74 static void
quit(int sig)75 quit(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 */
85 static void
okay(int pn)86 okay(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
119 static void
usage(void)120 usage(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
153 int
main(int ac,char * av[])154 main(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
203 if (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);
256 if (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);
270 if (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