xref: /freebsd/contrib/libpcap/pcap-netfilter-linux.c (revision 3b8f08459569bf0faa21473e5cec2491e95c9349)
1 /*
2  * Copyright (c) 2011 Jakub Zawadzki
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  *
9  * 1. Redistributions of source code must retain the above copyright
10  * notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  * notice, this list of conditions and the following disclaimer in the
13  * documentation and/or other materials provided with the distribution.
14  * 3. The name of the author may not be used to endorse or promote
15  * products derived from this software without specific prior written
16  * permission.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29  */
30 
31 #ifdef HAVE_CONFIG_H
32 #include "config.h"
33 #endif
34 
35 #include "pcap-int.h"
36 
37 #ifdef NEED_STRERROR_H
38 #include "strerror.h"
39 #endif
40 
41 #include <errno.h>
42 #include <stdlib.h>
43 #include <unistd.h>
44 #include <string.h>
45 #include <sys/socket.h>
46 #include <arpa/inet.h>
47 
48 #include <time.h>
49 #include <sys/time.h>
50 #include <netinet/in.h>
51 #include <linux/types.h>
52 
53 #include <linux/netlink.h>
54 #include <linux/netfilter.h>
55 #include <linux/netfilter/nfnetlink.h>
56 #include <linux/netfilter/nfnetlink_log.h>
57 #include <linux/netfilter/nfnetlink_queue.h>
58 
59 /* NOTE: if your program drops privilages after pcap_activate() it WON'T work with nfqueue.
60  *       It took me quite some time to debug ;/
61  *
62  *       Sending any data to nfnetlink socket requires CAP_NET_ADMIN privilages,
63  *       and in nfqueue we need to send verdict reply after recving packet.
64  *
65  *       In tcpdump you can disable dropping privilages with -Z root
66  */
67 
68 #include "pcap-netfilter-linux.h"
69 
70 #define HDR_LENGTH (NLMSG_LENGTH(NLMSG_ALIGN(sizeof(struct nfgenmsg))))
71 
72 #define NFLOG_IFACE "nflog"
73 #define NFQUEUE_IFACE "nfqueue"
74 
75 typedef enum { OTHER = -1, NFLOG, NFQUEUE } nftype_t;
76 
77 static int nfqueue_send_verdict(const pcap_t *handle, u_int16_t group_id, u_int32_t id, u_int32_t verdict);
78 
79 static int
80 netfilter_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
81 {
82 	const unsigned char *buf;
83 	int count = 0;
84 	int len;
85 
86 	/* ignore interrupt system call error */
87 	do {
88 		len = recv(handle->fd, handle->buffer, handle->bufsize, 0);
89 		if (handle->break_loop) {
90 			handle->break_loop = 0;
91 			return -2;
92 		}
93 	} while ((len == -1) && (errno == EINTR));
94 
95 	if (len < 0) {
96 		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't receive packet %d:%s", errno, pcap_strerror(errno));
97 		return -1;
98 	}
99 
100 	buf = handle->buffer;
101 	while (len >= NLMSG_SPACE(0)) {
102 		const struct nlmsghdr *nlh = (const struct nlmsghdr *) buf;
103 		u_int32_t msg_len;
104 		nftype_t type = OTHER;
105 
106 		if (nlh->nlmsg_len < sizeof(struct nlmsghdr) || len < nlh->nlmsg_len) {
107 			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Message truncated: (got: %d) (nlmsg_len: %u)", len, nlh->nlmsg_len);
108 			return -1;
109 		}
110 
111 		if (NFNL_SUBSYS_ID(nlh->nlmsg_type) == NFNL_SUBSYS_ULOG &&
112 			NFNL_MSG_TYPE(nlh->nlmsg_type) == NFULNL_MSG_PACKET)
113 				type = NFLOG;
114 
115 		if (NFNL_SUBSYS_ID(nlh->nlmsg_type) == NFNL_SUBSYS_QUEUE &&
116 			NFNL_MSG_TYPE(nlh->nlmsg_type) == NFQNL_MSG_PACKET)
117 				type = NFQUEUE;
118 
119 		if (type != OTHER) {
120 			const unsigned char *payload = NULL;
121 			struct pcap_pkthdr pkth;
122 
123 			const struct nfgenmsg *nfg;
124 			int id = 0;
125 
126 			if (handle->linktype != DLT_NFLOG) {
127 				const struct nfattr *payload_attr = NULL;
128 
129 				if (nlh->nlmsg_len < HDR_LENGTH) {
130 					snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Malformed message: (nlmsg_len: %u)", nlh->nlmsg_len);
131 					return -1;
132 				}
133 
134 				nfg = NLMSG_DATA(nlh);
135 				if (nlh->nlmsg_len > HDR_LENGTH) {
136 					struct nfattr *attr = NFM_NFA(nfg);
137 					int attr_len = nlh->nlmsg_len - NLMSG_ALIGN(HDR_LENGTH);
138 
139 					while (NFA_OK(attr, attr_len)) {
140 						if (type == NFQUEUE) {
141 							switch (NFA_TYPE(attr)) {
142 								case NFQA_PACKET_HDR:
143 									{
144 										const struct nfqnl_msg_packet_hdr *pkt_hdr = (const struct nfqnl_msg_packet_hdr *) NFA_DATA(attr);
145 
146 										id = ntohl(pkt_hdr->packet_id);
147 										break;
148 									}
149 								case NFQA_PAYLOAD:
150 									payload_attr = attr;
151 									break;
152 							}
153 
154 						} else if (type == NFLOG) {
155 							switch (NFA_TYPE(attr)) {
156 								case NFULA_PAYLOAD:
157 									payload_attr = attr;
158 									break;
159 							}
160 						}
161 						attr = NFA_NEXT(attr, attr_len);
162 					}
163 				}
164 
165 				if (payload_attr) {
166 					payload = NFA_DATA(payload_attr);
167 					pkth.len = pkth.caplen = NFA_PAYLOAD(payload_attr);
168 				}
169 
170 			} else {
171 				payload = NLMSG_DATA(nlh);
172 				pkth.caplen = pkth.len = nlh->nlmsg_len-NLMSG_ALIGN(sizeof(struct nlmsghdr));
173 			}
174 
175 			if (payload) {
176 				/* pkth.caplen = min (payload_len, handle->snapshot); */
177 
178 				gettimeofday(&pkth.ts, NULL);
179 				if (handle->fcode.bf_insns == NULL ||
180 						bpf_filter(handle->fcode.bf_insns, payload, pkth.len, pkth.caplen))
181 				{
182 					handle->md.packets_read++;
183 					callback(user, &pkth, payload);
184 					count++;
185 				}
186 			}
187 
188 			if (type == NFQUEUE) {
189 				/* XXX, possible responses: NF_DROP, NF_ACCEPT, NF_STOLEN, NF_QUEUE, NF_REPEAT, NF_STOP */
190 				nfqueue_send_verdict(handle, ntohs(nfg->res_id), id, NF_ACCEPT);
191 			}
192 		}
193 
194 		msg_len = NLMSG_ALIGN(nlh->nlmsg_len);
195 		if (msg_len > len)
196 			msg_len = len;
197 
198 		len -= msg_len;
199 		buf += msg_len;
200 	}
201 	return count;
202 }
203 
204 static int
205 netfilter_set_datalink(pcap_t *handle, int dlt)
206 {
207 	handle->linktype = dlt;
208 	return 0;
209 }
210 
211 static int
212 netfilter_stats_linux(pcap_t *handle, struct pcap_stat *stats)
213 {
214 	stats->ps_recv = handle->md.packets_read;
215 	stats->ps_drop = 0;
216 	stats->ps_ifdrop = 0;
217 	return 0;
218 }
219 
220 static int
221 netfilter_inject_linux(pcap_t *handle, const void *buf, size_t size)
222 {
223 	snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "inject not supported on netfilter devices");
224 	return (-1);
225 }
226 
227 struct my_nfattr {
228 	u_int16_t nfa_len;
229 	u_int16_t nfa_type;
230 	void *data;
231 };
232 
233 static int
234 netfilter_send_config_msg(const pcap_t *handle, u_int16_t msg_type, int ack, u_int8_t family, u_int16_t res_id, const struct my_nfattr *mynfa)
235 {
236 	char buf[1024] __attribute__ ((aligned));
237 
238 	struct nlmsghdr *nlh = (struct nlmsghdr *) buf;
239 	struct nfgenmsg *nfg = (struct nfgenmsg *) (buf + sizeof(struct nlmsghdr));
240 
241 	struct sockaddr_nl snl;
242 	static unsigned int seq_id;
243 
244 	if (!seq_id)
245 		seq_id = time(NULL);
246 	++seq_id;
247 
248 	nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct nfgenmsg));
249 	nlh->nlmsg_type = msg_type;
250 	nlh->nlmsg_flags = NLM_F_REQUEST | (ack ? NLM_F_ACK : 0);
251 	nlh->nlmsg_pid = 0;	/* to kernel */
252 	nlh->nlmsg_seq = seq_id;
253 
254 	nfg->nfgen_family = family;
255 	nfg->version = NFNETLINK_V0;
256 	nfg->res_id = htons(res_id);
257 
258 	if (mynfa) {
259 		struct nfattr *nfa = (struct nfattr *) (buf + NLMSG_ALIGN(nlh->nlmsg_len));
260 
261 		nfa->nfa_type = mynfa->nfa_type;
262 		nfa->nfa_len = NFA_LENGTH(mynfa->nfa_len);
263 		memcpy(NFA_DATA(nfa), mynfa->data, mynfa->nfa_len);
264 		nlh->nlmsg_len = NLMSG_ALIGN(nlh->nlmsg_len) + NFA_ALIGN(nfa->nfa_len);
265 	}
266 
267 	memset(&snl, 0, sizeof(snl));
268 	snl.nl_family = AF_NETLINK;
269 
270 	if (sendto(handle->fd, nlh, nlh->nlmsg_len, 0, (struct sockaddr *) &snl, sizeof(snl)) == -1)
271 		return -1;
272 
273 	if (!ack)
274 		return 0;
275 
276 	/* waiting for reply loop */
277 	do {
278 		socklen_t addrlen = sizeof(snl);
279 		int len;
280 
281 		/* ignore interrupt system call error */
282 		do {
283 			len = recvfrom(handle->fd, buf, sizeof(buf), 0, (struct sockaddr *) &snl, &addrlen);
284 		} while ((len == -1) && (errno == EINTR));
285 
286 		if (len <= 0)
287 			return len;
288 
289 		if (addrlen != sizeof(snl) || snl.nl_family != AF_NETLINK) {
290 			errno = EINVAL;
291 			return -1;
292 		}
293 
294 		nlh = (struct nlmsghdr *) buf;
295 		if (snl.nl_pid != 0 || seq_id != nlh->nlmsg_seq)	/* if not from kernel or wrong sequence skip */
296 			continue;
297 
298 		while (len >= NLMSG_SPACE(0) && NLMSG_OK(nlh, len)) {
299 			if (nlh->nlmsg_type == NLMSG_ERROR || (nlh->nlmsg_type == NLMSG_DONE && nlh->nlmsg_flags & NLM_F_MULTI)) {
300 				if (nlh->nlmsg_len < NLMSG_ALIGN(sizeof(struct nlmsgerr))) {
301 					errno = EBADMSG;
302 					return -1;
303 				}
304 				errno = -(*((int *)NLMSG_DATA(nlh)));
305 				return (errno == 0) ? 0 : -1;
306 			}
307 			nlh = NLMSG_NEXT(nlh, len);
308 		}
309 	} while (1);
310 
311 	return -1; /* never here */
312 }
313 
314 static int
315 nflog_send_config_msg(const pcap_t *handle, u_int8_t family, u_int16_t group_id, const struct my_nfattr *mynfa)
316 {
317 	return netfilter_send_config_msg(handle, (NFNL_SUBSYS_ULOG << 8) | NFULNL_MSG_CONFIG, 1, family, group_id, mynfa);
318 }
319 
320 static int
321 nflog_send_config_cmd(const pcap_t *handle, u_int16_t group_id, u_int8_t cmd, u_int8_t family)
322 {
323 	struct nfulnl_msg_config_cmd msg;
324 	struct my_nfattr nfa;
325 
326 	msg.command = cmd;
327 
328 	nfa.data = &msg;
329 	nfa.nfa_type = NFULA_CFG_CMD;
330 	nfa.nfa_len = sizeof(msg);
331 
332 	return nflog_send_config_msg(handle, family, group_id, &nfa);
333 }
334 
335 static int
336 nflog_send_config_mode(const pcap_t *handle, u_int16_t group_id, u_int8_t copy_mode, u_int32_t copy_range)
337 {
338 	struct nfulnl_msg_config_mode msg;
339 	struct my_nfattr nfa;
340 
341 	msg.copy_range = htonl(copy_range);
342 	msg.copy_mode = copy_mode;
343 
344 	nfa.data = &msg;
345 	nfa.nfa_type = NFULA_CFG_MODE;
346 	nfa.nfa_len = sizeof(msg);
347 
348 	return nflog_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
349 }
350 
351 static int
352 nfqueue_send_verdict(const pcap_t *handle, u_int16_t group_id, u_int32_t id, u_int32_t verdict)
353 {
354 	struct nfqnl_msg_verdict_hdr msg;
355 	struct my_nfattr nfa;
356 
357 	msg.id = htonl(id);
358 	msg.verdict = htonl(verdict);
359 
360 	nfa.data = &msg;
361 	nfa.nfa_type = NFQA_VERDICT_HDR;
362 	nfa.nfa_len = sizeof(msg);
363 
364 	return netfilter_send_config_msg(handle, (NFNL_SUBSYS_QUEUE << 8) | NFQNL_MSG_VERDICT, 0, AF_UNSPEC, group_id, &nfa);
365 }
366 
367 static int
368 nfqueue_send_config_msg(const pcap_t *handle, u_int8_t family, u_int16_t group_id, const struct my_nfattr *mynfa)
369 {
370 	return netfilter_send_config_msg(handle, (NFNL_SUBSYS_QUEUE << 8) | NFQNL_MSG_CONFIG, 1, family, group_id, mynfa);
371 }
372 
373 static int
374 nfqueue_send_config_cmd(const pcap_t *handle, u_int16_t group_id, u_int8_t cmd, u_int16_t pf)
375 {
376 	struct nfqnl_msg_config_cmd msg;
377 	struct my_nfattr nfa;
378 
379 	msg.command = cmd;
380 	msg.pf = htons(pf);
381 
382 	nfa.data = &msg;
383 	nfa.nfa_type = NFQA_CFG_CMD;
384 	nfa.nfa_len = sizeof(msg);
385 
386 	return nfqueue_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
387 }
388 
389 static int
390 nfqueue_send_config_mode(const pcap_t *handle, u_int16_t group_id, u_int8_t copy_mode, u_int32_t copy_range)
391 {
392 	struct nfqnl_msg_config_params msg;
393 	struct my_nfattr nfa;
394 
395 	msg.copy_range = htonl(copy_range);
396 	msg.copy_mode = copy_mode;
397 
398 	nfa.data = &msg;
399 	nfa.nfa_type = NFQA_CFG_PARAMS;
400 	nfa.nfa_len = sizeof(msg);
401 
402 	return nfqueue_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
403 }
404 
405 static int
406 netfilter_activate(pcap_t* handle)
407 {
408 	const char *dev = handle->opt.source;
409 	unsigned short groups[32];
410 	int group_count = 0;
411 	nftype_t type = OTHER;
412 	int i;
413 
414  	if (strncmp(dev, NFLOG_IFACE, strlen(NFLOG_IFACE)) == 0) {
415  		dev += strlen(NFLOG_IFACE);
416 		type = NFLOG;
417 
418 	} else if (strncmp(dev, NFQUEUE_IFACE, strlen(NFQUEUE_IFACE)) == 0) {
419 		dev += strlen(NFQUEUE_IFACE);
420 		type = NFQUEUE;
421 	}
422 
423 	if (type != OTHER && *dev == ':') {
424 		dev++;
425 		while (*dev) {
426 			long int group_id;
427 			char *end_dev;
428 
429 			if (group_count == 32) {
430 				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
431 						"Maximum 32 netfilter groups! dev: %s",
432 						handle->opt.source);
433 				return PCAP_ERROR;
434 			}
435 
436 			group_id = strtol(dev, &end_dev, 0);
437 			if (end_dev != dev) {
438 				if (group_id < 0 || group_id > 65535) {
439 					snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
440 							"Netfilter group range from 0 to 65535 (got %ld)",
441 							group_id);
442 					return PCAP_ERROR;
443 				}
444 
445 				groups[group_count++] = (unsigned short) group_id;
446 				dev = end_dev;
447 			}
448 			if (*dev != ',')
449 				break;
450 			dev++;
451 		}
452 	}
453 
454 	if (type == OTHER || *dev) {
455 		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
456 				"Can't get netfilter group(s) index from %s",
457 				handle->opt.source);
458 		return PCAP_ERROR;
459 	}
460 
461 	/* if no groups, add default: 0 */
462 	if (!group_count) {
463 		groups[0] = 0;
464 		group_count = 1;
465 	}
466 
467 	/* Initialize some components of the pcap structure. */
468 	handle->bufsize = 128 + handle->snapshot;
469 	handle->offset = 0;
470 	handle->read_op = netfilter_read_linux;
471 	handle->inject_op = netfilter_inject_linux;
472 	handle->setfilter_op = install_bpf_program; /* no kernel filtering */
473 	handle->setdirection_op = NULL;
474 	handle->set_datalink_op = NULL;
475 	handle->set_datalink_op = netfilter_set_datalink;
476 	handle->getnonblock_op = pcap_getnonblock_fd;
477 	handle->setnonblock_op = pcap_setnonblock_fd;
478 	handle->stats_op = netfilter_stats_linux;
479 
480 	/* Create netlink socket */
481 	handle->fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER);
482 	if (handle->fd < 0) {
483 		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't create raw socket %d:%s", errno, pcap_strerror(errno));
484 		return PCAP_ERROR;
485 	}
486 
487 	if (type == NFLOG) {
488 		handle->linktype = DLT_NFLOG;
489 		handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
490 		if (handle->dlt_list != NULL) {
491 			handle->dlt_list[0] = DLT_NFLOG;
492 			handle->dlt_list[1] = DLT_IPV4;
493 			handle->dlt_count = 2;
494 		}
495 
496 	} else
497 		handle->linktype = DLT_IPV4;
498 
499 	handle->buffer = malloc(handle->bufsize);
500 	if (!handle->buffer) {
501 		snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't allocate dump buffer: %s", pcap_strerror(errno));
502 		goto close_fail;
503 	}
504 
505 	if (type == NFLOG) {
506 		if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_UNBIND, AF_INET) < 0) {
507 			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_CFG_CMD_PF_UNBIND: %s", pcap_strerror(errno));
508 			goto close_fail;
509 		}
510 
511 		if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_BIND, AF_INET) < 0) {
512 			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_CFG_CMD_PF_BIND: %s", pcap_strerror(errno));
513 			goto close_fail;
514 		}
515 
516 		/* Bind socket to the nflog groups */
517 		for (i = 0; i < group_count; i++) {
518 			if (nflog_send_config_cmd(handle, groups[i], NFULNL_CFG_CMD_BIND, AF_UNSPEC) < 0) {
519 				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't listen on group group index: %s", pcap_strerror(errno));
520 				goto close_fail;
521 			}
522 
523 			if (nflog_send_config_mode(handle, groups[i], NFULNL_COPY_PACKET, handle->snapshot) < 0) {
524 				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_COPY_PACKET: %s", pcap_strerror(errno));
525 				goto close_fail;
526 			}
527 		}
528 
529 	} else {
530 		if (nfqueue_send_config_cmd(handle, 0, NFQNL_CFG_CMD_PF_UNBIND, AF_INET) < 0) {
531 			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFQNL_CFG_CMD_PF_UNBIND: %s", pcap_strerror(errno));
532 			goto close_fail;
533 		}
534 
535 		if (nfqueue_send_config_cmd(handle, 0, NFQNL_CFG_CMD_PF_BIND, AF_INET) < 0) {
536 			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFQNL_CFG_CMD_PF_BIND: %s", pcap_strerror(errno));
537 			goto close_fail;
538 		}
539 
540 		/* Bind socket to the nfqueue groups */
541 		for (i = 0; i < group_count; i++) {
542 			if (nfqueue_send_config_cmd(handle, groups[i], NFQNL_CFG_CMD_BIND, AF_UNSPEC) < 0) {
543 				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't listen on group group index: %s", pcap_strerror(errno));
544 				goto close_fail;
545 			}
546 
547 			if (nfqueue_send_config_mode(handle, groups[i], NFQNL_COPY_PACKET, handle->snapshot) < 0) {
548 				snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFQNL_COPY_PACKET: %s", pcap_strerror(errno));
549 				goto close_fail;
550 			}
551 		}
552 	}
553 
554 	if (handle->opt.rfmon) {
555 		/*
556 		 * Monitor mode doesn't apply to netfilter devices.
557 		 */
558 		pcap_cleanup_live_common(handle);
559 		return PCAP_ERROR_RFMON_NOTSUP;
560 	}
561 
562 	if (handle->opt.buffer_size != 0) {
563 		/*
564 		 * Set the socket buffer size to the specified value.
565 		 */
566 		if (setsockopt(handle->fd, SOL_SOCKET, SO_RCVBUF, &handle->opt.buffer_size, sizeof(handle->opt.buffer_size)) == -1) {
567 			snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "SO_RCVBUF: %s", pcap_strerror(errno));
568 			goto close_fail;
569 		}
570 	}
571 
572 	handle->selectable_fd = handle->fd;
573 	return 0;
574 
575 close_fail:
576 	pcap_cleanup_live_common(handle);
577 	return PCAP_ERROR;
578 }
579 
580 pcap_t *
581 netfilter_create(const char *device, char *ebuf, int *is_ours)
582 {
583 	const char *cp;
584 	pcap_t *p;
585 
586 	/* Does this look like an netfilter device? */
587 	cp = strrchr(device, '/');
588 	if (cp == NULL)
589 		cp = device;
590 
591 	/* Does it begin with NFLOG_IFACE or NFQUEUE_IFACE? */
592 	if (strncmp(cp, NFLOG_IFACE, sizeof NFLOG_IFACE - 1) == 0)
593 		cp += sizeof NFLOG_IFACE - 1;
594 	else if (strncmp(cp, NFQUEUE_IFACE, sizeof NFQUEUE_IFACE - 1) == 0)
595 		cp += sizeof NFQUEUE_IFACE - 1;
596 	else {
597 		/* Nope, doesn't begin with NFLOG_IFACE nor NFQUEUE_IFACE */
598 		*is_ours = 0;
599 		return NULL;
600 	}
601 
602 	/*
603 	 * Yes - is that either the end of the name, or is it followed
604 	 * by a colon?
605 	 */
606 	if (*cp != ':' && *cp != '\0') {
607 		/* Nope */
608 		*is_ours = 0;
609 		return NULL;
610 	}
611 
612 	/* OK, it's probably ours. */
613 	*is_ours = 1;
614 
615 	p = pcap_create_common(device, ebuf);
616 	if (p == NULL)
617 		return (NULL);
618 
619 	p->activate_op = netfilter_activate;
620 	return (p);
621 }
622 
623 int
624 netfilter_findalldevs(pcap_if_t **alldevsp, char *err_str)
625 {
626 	pcap_if_t *found_dev = *alldevsp;
627 	int sock;
628 
629 	sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER);
630 	if (sock < 0) {
631 		/* if netlink is not supported this is not fatal */
632 		if (errno == EAFNOSUPPORT || errno == EPROTONOSUPPORT)
633 			return 0;
634 		snprintf(err_str, PCAP_ERRBUF_SIZE, "Can't open netlink socket %d:%s",
635 			errno, pcap_strerror(errno));
636 		return -1;
637 	}
638 	close(sock);
639 
640 	if (pcap_add_if(&found_dev, NFLOG_IFACE, 0, "Linux netfilter log (NFLOG) interface", err_str) < 0)
641 		return -1;
642 	if (pcap_add_if(&found_dev, NFQUEUE_IFACE, 0, "Linux netfilter queue (NFQUEUE) interface", err_str) < 0)
643 		return -1;
644 	return 0;
645 }
646