1 /*
2 * pcap-linux.c: Packet capture interface to the Linux kernel
3 *
4 * Copyright (c) 2000 Torsten Landschoff <torsten@debian.org>
5 * Sebastian Krahmer <krahmer@cs.uni-potsdam.de>
6 *
7 * License: BSD
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 *
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in
17 * the documentation and/or other materials provided with the
18 * distribution.
19 * 3. The names of the authors may not be used to endorse or promote
20 * products derived from this software without specific prior
21 * written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
24 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
25 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
26 */
27
28 #ifndef lint
29 static const char rcsid[] _U_ =
30 "@(#) $Header: /tcpdump/master/libpcap/pcap-linux.c,v 1.110.2.14 2006/10/12 17:26:58 guy Exp $ (LBL)";
31 #endif
32
33 /*
34 * Known problems with 2.0[.x] kernels:
35 *
36 * - The loopback device gives every packet twice; on 2.2[.x] kernels,
37 * if we use PF_PACKET, we can filter out the transmitted version
38 * of the packet by using data in the "sockaddr_ll" returned by
39 * "recvfrom()", but, on 2.0[.x] kernels, we have to use
40 * PF_INET/SOCK_PACKET, which means "recvfrom()" supplies a
41 * "sockaddr_pkt" which doesn't give us enough information to let
42 * us do that.
43 *
44 * - We have to set the interface's IFF_PROMISC flag ourselves, if
45 * we're to run in promiscuous mode, which means we have to turn
46 * it off ourselves when we're done; the kernel doesn't keep track
47 * of how many sockets are listening promiscuously, which means
48 * it won't get turned off automatically when no sockets are
49 * listening promiscuously. We catch "pcap_close()" and, for
50 * interfaces we put into promiscuous mode, take them out of
51 * promiscuous mode - which isn't necessarily the right thing to
52 * do, if another socket also requested promiscuous mode between
53 * the time when we opened the socket and the time when we close
54 * the socket.
55 *
56 * - MSG_TRUNC isn't supported, so you can't specify that "recvfrom()"
57 * return the amount of data that you could have read, rather than
58 * the amount that was returned, so we can't just allocate a buffer
59 * whose size is the snapshot length and pass the snapshot length
60 * as the byte count, and also pass MSG_TRUNC, so that the return
61 * value tells us how long the packet was on the wire.
62 *
63 * This means that, if we want to get the actual size of the packet,
64 * so we can return it in the "len" field of the packet header,
65 * we have to read the entire packet, not just the part that fits
66 * within the snapshot length, and thus waste CPU time copying data
67 * from the kernel that our caller won't see.
68 *
69 * We have to get the actual size, and supply it in "len", because
70 * otherwise, the IP dissector in tcpdump, for example, will complain
71 * about "truncated-ip", as the packet will appear to have been
72 * shorter, on the wire, than the IP header said it should have been.
73 */
74
75
76 #include <stdlib.h>
77 #ifdef HAVE_CONFIG_H
78 #include "config.h"
79 #endif
80
81 #include "pcap-int.h"
82 #include "sll.h"
83
84 #ifdef HAVE_DAG_API
85 #include "pcap-dag.h"
86 #endif /* HAVE_DAG_API */
87
88 #ifdef HAVE_SEPTEL_API
89 #include "pcap-septel.h"
90 #endif /* HAVE_SEPTEL_API */
91
92 #include <errno.h>
93 #include <unistd.h>
94 #include <fcntl.h>
95 #include <string.h>
96 #include <sys/socket.h>
97 #include <sys/ioctl.h>
98 #include <sys/utsname.h>
99 #include <net/if.h>
100 #include <netinet/in.h>
101 #include <linux/if_ether.h>
102 #include <net/if_arp.h>
103
104 /*
105 * If PF_PACKET is defined, we can use {SOCK_RAW,SOCK_DGRAM}/PF_PACKET
106 * sockets rather than SOCK_PACKET sockets.
107 *
108 * To use them, we include <linux/if_packet.h> rather than
109 * <netpacket/packet.h>; we do so because
110 *
111 * some Linux distributions (e.g., Slackware 4.0) have 2.2 or
112 * later kernels and libc5, and don't provide a <netpacket/packet.h>
113 * file;
114 *
115 * not all versions of glibc2 have a <netpacket/packet.h> file
116 * that defines stuff needed for some of the 2.4-or-later-kernel
117 * features, so if the system has a 2.4 or later kernel, we
118 * still can't use those features.
119 *
120 * We're already including a number of other <linux/XXX.h> headers, and
121 * this code is Linux-specific (no other OS has PF_PACKET sockets as
122 * a raw packet capture mechanism), so it's not as if you gain any
123 * useful portability by using <netpacket/packet.h>
124 *
125 * XXX - should we just include <linux/if_packet.h> even if PF_PACKET
126 * isn't defined? It only defines one data structure in 2.0.x, so
127 * it shouldn't cause any problems.
128 */
129 #ifdef PF_PACKET
130 # include <linux/if_packet.h>
131
132 /*
133 * On at least some Linux distributions (for example, Red Hat 5.2),
134 * there's no <netpacket/packet.h> file, but PF_PACKET is defined if
135 * you include <sys/socket.h>, but <linux/if_packet.h> doesn't define
136 * any of the PF_PACKET stuff such as "struct sockaddr_ll" or any of
137 * the PACKET_xxx stuff.
138 *
139 * So we check whether PACKET_HOST is defined, and assume that we have
140 * PF_PACKET sockets only if it is defined.
141 */
142 # ifdef PACKET_HOST
143 # define HAVE_PF_PACKET_SOCKETS
144 # endif /* PACKET_HOST */
145 #endif /* PF_PACKET */
146
147 #ifdef SO_ATTACH_FILTER
148 #include <linux/types.h>
149 #include <linux/filter.h>
150 #endif
151
152 #ifndef __GLIBC__
153 typedef int socklen_t;
154 #endif
155
156 #ifndef MSG_TRUNC
157 /*
158 * This is being compiled on a system that lacks MSG_TRUNC; define it
159 * with the value it has in the 2.2 and later kernels, so that, on
160 * those kernels, when we pass it in the flags argument to "recvfrom()"
161 * we're passing the right value and thus get the MSG_TRUNC behavior
162 * we want. (We don't get that behavior on 2.0[.x] kernels, because
163 * they didn't support MSG_TRUNC.)
164 */
165 #define MSG_TRUNC 0x20
166 #endif
167
168 #ifndef SOL_PACKET
169 /*
170 * This is being compiled on a system that lacks SOL_PACKET; define it
171 * with the value it has in the 2.2 and later kernels, so that we can
172 * set promiscuous mode in the good modern way rather than the old
173 * 2.0-kernel crappy way.
174 */
175 #define SOL_PACKET 263
176 #endif
177
178 #define MAX_LINKHEADER_SIZE 256
179
180 /*
181 * When capturing on all interfaces we use this as the buffer size.
182 * Should be bigger then all MTUs that occur in real life.
183 * 64kB should be enough for now.
184 */
185 #define BIGGER_THAN_ALL_MTUS (64*1024)
186
187 /*
188 * Prototypes for internal functions
189 */
190 static void map_arphrd_to_dlt(pcap_t *, int, int);
191 static int live_open_old(pcap_t *, const char *, int, int, char *);
192 static int live_open_new(pcap_t *, const char *, int, int, char *);
193 static int pcap_read_linux(pcap_t *, int, pcap_handler, u_char *);
194 static int pcap_read_packet(pcap_t *, pcap_handler, u_char *);
195 static int pcap_inject_linux(pcap_t *, const void *, size_t);
196 static int pcap_stats_linux(pcap_t *, struct pcap_stat *);
197 static int pcap_setfilter_linux(pcap_t *, struct bpf_program *);
198 static int pcap_setdirection_linux(pcap_t *, pcap_direction_t);
199 static void pcap_close_linux(pcap_t *);
200
201 /*
202 * Wrap some ioctl calls
203 */
204 #ifdef HAVE_PF_PACKET_SOCKETS
205 static int iface_get_id(int fd, const char *device, char *ebuf);
206 #endif
207 static int iface_get_mtu(int fd, const char *device, char *ebuf);
208 static int iface_get_arptype(int fd, const char *device, char *ebuf);
209 #ifdef HAVE_PF_PACKET_SOCKETS
210 static int iface_bind(int fd, int ifindex, char *ebuf);
211 #endif
212 static int iface_bind_old(int fd, const char *device, char *ebuf);
213
214 #ifdef SO_ATTACH_FILTER
215 static int fix_program(pcap_t *handle, struct sock_fprog *fcode);
216 static int fix_offset(struct bpf_insn *p);
217 static int set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode);
218 static int reset_kernel_filter(pcap_t *handle);
219
220 static struct sock_filter total_insn
221 = BPF_STMT(BPF_RET | BPF_K, 0);
222 static struct sock_fprog total_fcode
223 = { 1, &total_insn };
224 #endif
225
226 /*
227 * Get a handle for a live capture from the given device. You can
228 * pass NULL as device to get all packages (without link level
229 * information of course). If you pass 1 as promisc the interface
230 * will be set to promiscous mode (XXX: I think this usage should
231 * be deprecated and functions be added to select that later allow
232 * modification of that values -- Torsten).
233 *
234 * See also pcap(3).
235 */
236 pcap_t *
pcap_open_live(const char * device,int snaplen,int promisc,int to_ms,char * ebuf)237 pcap_open_live(const char *device, int snaplen, int promisc, int to_ms,
238 char *ebuf)
239 {
240 pcap_t *handle;
241 int mtu;
242 int err;
243 int live_open_ok = 0;
244 struct utsname utsname;
245
246 #ifdef HAVE_DAG_API
247 if (strstr(device, "dag")) {
248 return dag_open_live(device, snaplen, promisc, to_ms, ebuf);
249 }
250 #endif /* HAVE_DAG_API */
251
252 #ifdef HAVE_SEPTEL_API
253 if (strstr(device, "septel")) {
254 return septel_open_live(device, snaplen, promisc, to_ms, ebuf);
255 }
256 #endif /* HAVE_SEPTEL_API */
257
258 /* Allocate a handle for this session. */
259
260 handle = malloc(sizeof(*handle));
261 if (handle == NULL) {
262 snprintf(ebuf, PCAP_ERRBUF_SIZE, "malloc: %s",
263 pcap_strerror(errno));
264 return NULL;
265 }
266
267 /* Initialize some components of the pcap structure. */
268
269 memset(handle, 0, sizeof(*handle));
270 handle->snapshot = snaplen;
271 handle->md.timeout = to_ms;
272
273 /*
274 * NULL and "any" are special devices which give us the hint to
275 * monitor all devices.
276 */
277 if (!device || strcmp(device, "any") == 0) {
278 device = NULL;
279 handle->md.device = strdup("any");
280 if (promisc) {
281 promisc = 0;
282 /* Just a warning. */
283 snprintf(ebuf, PCAP_ERRBUF_SIZE,
284 "Promiscuous mode not supported on the \"any\" device");
285 }
286
287 } else
288 handle->md.device = strdup(device);
289
290 if (handle->md.device == NULL) {
291 snprintf(ebuf, PCAP_ERRBUF_SIZE, "strdup: %s",
292 pcap_strerror(errno) );
293 free(handle);
294 return NULL;
295 }
296
297 /*
298 * Current Linux kernels use the protocol family PF_PACKET to
299 * allow direct access to all packets on the network while
300 * older kernels had a special socket type SOCK_PACKET to
301 * implement this feature.
302 * While this old implementation is kind of obsolete we need
303 * to be compatible with older kernels for a while so we are
304 * trying both methods with the newer method preferred.
305 */
306
307 if ((err = live_open_new(handle, device, promisc, to_ms, ebuf)) == 1)
308 live_open_ok = 1;
309 else if (err == 0) {
310 /* Non-fatal error; try old way */
311 if (live_open_old(handle, device, promisc, to_ms, ebuf))
312 live_open_ok = 1;
313 }
314 if (!live_open_ok) {
315 /*
316 * Both methods to open the packet socket failed. Tidy
317 * up and report our failure (ebuf is expected to be
318 * set by the functions above).
319 */
320
321 if (handle->md.device != NULL)
322 free(handle->md.device);
323 free(handle);
324 return NULL;
325 }
326
327 /*
328 * Compute the buffer size.
329 *
330 * If we're using SOCK_PACKET, this might be a 2.0[.x] kernel,
331 * and might require special handling - check.
332 */
333 if (handle->md.sock_packet && (uname(&utsname) < 0 ||
334 strncmp(utsname.release, "2.0", 3) == 0)) {
335 /*
336 * We're using a SOCK_PACKET structure, and either
337 * we couldn't find out what kernel release this is,
338 * or it's a 2.0[.x] kernel.
339 *
340 * In the 2.0[.x] kernel, a "recvfrom()" on
341 * a SOCK_PACKET socket, with MSG_TRUNC set, will
342 * return the number of bytes read, so if we pass
343 * a length based on the snapshot length, it'll
344 * return the number of bytes from the packet
345 * copied to userland, not the actual length
346 * of the packet.
347 *
348 * This means that, for example, the IP dissector
349 * in tcpdump will get handed a packet length less
350 * than the length in the IP header, and will
351 * complain about "truncated-ip".
352 *
353 * So we don't bother trying to copy from the
354 * kernel only the bytes in which we're interested,
355 * but instead copy them all, just as the older
356 * versions of libpcap for Linux did.
357 *
358 * The buffer therefore needs to be big enough to
359 * hold the largest packet we can get from this
360 * device. Unfortunately, we can't get the MRU
361 * of the network; we can only get the MTU. The
362 * MTU may be too small, in which case a packet larger
363 * than the buffer size will be truncated *and* we
364 * won't get the actual packet size.
365 *
366 * However, if the snapshot length is larger than
367 * the buffer size based on the MTU, we use the
368 * snapshot length as the buffer size, instead;
369 * this means that with a sufficiently large snapshot
370 * length we won't artificially truncate packets
371 * to the MTU-based size.
372 *
373 * This mess just one of many problems with packet
374 * capture on 2.0[.x] kernels; you really want a
375 * 2.2[.x] or later kernel if you want packet capture
376 * to work well.
377 */
378 mtu = iface_get_mtu(handle->fd, device, ebuf);
379 if (mtu == -1) {
380 pcap_close_linux(handle);
381 free(handle);
382 return NULL;
383 }
384 handle->bufsize = MAX_LINKHEADER_SIZE + mtu;
385 if (handle->bufsize < handle->snapshot)
386 handle->bufsize = handle->snapshot;
387 } else {
388 /*
389 * This is a 2.2[.x] or later kernel (we know that
390 * either because we're not using a SOCK_PACKET
391 * socket - PF_PACKET is supported only in 2.2
392 * and later kernels - or because we checked the
393 * kernel version).
394 *
395 * We can safely pass "recvfrom()" a byte count
396 * based on the snapshot length.
397 *
398 * If we're in cooked mode, make the snapshot length
399 * large enough to hold a "cooked mode" header plus
400 * 1 byte of packet data (so we don't pass a byte
401 * count of 0 to "recvfrom()").
402 */
403 if (handle->md.cooked) {
404 if (handle->snapshot < SLL_HDR_LEN + 1)
405 handle->snapshot = SLL_HDR_LEN + 1;
406 }
407 handle->bufsize = handle->snapshot;
408 }
409
410 /* Allocate the buffer */
411
412 handle->buffer = malloc(handle->bufsize + handle->offset);
413 if (!handle->buffer) {
414 snprintf(ebuf, PCAP_ERRBUF_SIZE,
415 "malloc: %s", pcap_strerror(errno));
416 pcap_close_linux(handle);
417 free(handle);
418 return NULL;
419 }
420
421 /*
422 * "handle->fd" is a socket, so "select()" and "poll()"
423 * should work on it.
424 */
425 handle->selectable_fd = handle->fd;
426
427 handle->read_op = pcap_read_linux;
428 handle->inject_op = pcap_inject_linux;
429 handle->setfilter_op = pcap_setfilter_linux;
430 handle->setdirection_op = pcap_setdirection_linux;
431 handle->set_datalink_op = NULL; /* can't change data link type */
432 handle->getnonblock_op = pcap_getnonblock_fd;
433 handle->setnonblock_op = pcap_setnonblock_fd;
434 handle->stats_op = pcap_stats_linux;
435 handle->close_op = pcap_close_linux;
436
437 return handle;
438 }
439
440 /*
441 * Read at most max_packets from the capture stream and call the callback
442 * for each of them. Returns the number of packets handled or -1 if an
443 * error occured.
444 */
445 static int
pcap_read_linux(pcap_t * handle,int max_packets,pcap_handler callback,u_char * user)446 pcap_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
447 {
448 /*
449 * Currently, on Linux only one packet is delivered per read,
450 * so we don't loop.
451 */
452 return pcap_read_packet(handle, callback, user);
453 }
454
455 /*
456 * Read a packet from the socket calling the handler provided by
457 * the user. Returns the number of packets received or -1 if an
458 * error occured.
459 */
460 static int
pcap_read_packet(pcap_t * handle,pcap_handler callback,u_char * userdata)461 pcap_read_packet(pcap_t *handle, pcap_handler callback, u_char *userdata)
462 {
463 u_char *bp;
464 int offset;
465 #ifdef HAVE_PF_PACKET_SOCKETS
466 struct sockaddr_ll from;
467 struct sll_header *hdrp;
468 #else
469 struct sockaddr from;
470 #endif
471 socklen_t fromlen;
472 int packet_len, caplen;
473 struct pcap_pkthdr pcap_header;
474
475 #ifdef HAVE_PF_PACKET_SOCKETS
476 /*
477 * If this is a cooked device, leave extra room for a
478 * fake packet header.
479 */
480 if (handle->md.cooked)
481 offset = SLL_HDR_LEN;
482 else
483 offset = 0;
484 #else
485 /*
486 * This system doesn't have PF_PACKET sockets, so it doesn't
487 * support cooked devices.
488 */
489 offset = 0;
490 #endif
491
492 /* Receive a single packet from the kernel */
493
494 bp = handle->buffer + handle->offset;
495 do {
496 /*
497 * Has "pcap_breakloop()" been called?
498 */
499 if (handle->break_loop) {
500 /*
501 * Yes - clear the flag that indicates that it
502 * has, and return -2 as an indication that we
503 * were told to break out of the loop.
504 */
505 handle->break_loop = 0;
506 return -2;
507 }
508 fromlen = sizeof(from);
509 packet_len = recvfrom(
510 handle->fd, bp + offset,
511 handle->bufsize - offset, MSG_TRUNC,
512 (struct sockaddr *) &from, &fromlen);
513 } while (packet_len == -1 && errno == EINTR);
514
515 /* Check if an error occured */
516
517 if (packet_len == -1) {
518 if (errno == EAGAIN)
519 return 0; /* no packet there */
520 else {
521 snprintf(handle->errbuf, sizeof(handle->errbuf),
522 "recvfrom: %s", pcap_strerror(errno));
523 return -1;
524 }
525 }
526
527 #ifdef HAVE_PF_PACKET_SOCKETS
528 if (!handle->md.sock_packet) {
529 /*
530 * Unfortunately, there is a window between socket() and
531 * bind() where the kernel may queue packets from any
532 * interface. If we're bound to a particular interface,
533 * discard packets not from that interface.
534 *
535 * (If socket filters are supported, we could do the
536 * same thing we do when changing the filter; however,
537 * that won't handle packet sockets without socket
538 * filter support, and it's a bit more complicated.
539 * It would save some instructions per packet, however.)
540 */
541 if (handle->md.ifindex != -1 &&
542 from.sll_ifindex != handle->md.ifindex)
543 return 0;
544
545 /*
546 * Do checks based on packet direction.
547 * We can only do this if we're using PF_PACKET; the
548 * address returned for SOCK_PACKET is a "sockaddr_pkt"
549 * which lacks the relevant packet type information.
550 */
551 if (from.sll_pkttype == PACKET_OUTGOING) {
552 /*
553 * Outgoing packet.
554 * If this is from the loopback device, reject it;
555 * we'll see the packet as an incoming packet as well,
556 * and we don't want to see it twice.
557 */
558 if (from.sll_ifindex == handle->md.lo_ifindex)
559 return 0;
560
561 /*
562 * If the user only wants incoming packets, reject it.
563 */
564 if (handle->direction == PCAP_D_IN)
565 return 0;
566 } else {
567 /*
568 * Incoming packet.
569 * If the user only wants outgoing packets, reject it.
570 */
571 if (handle->direction == PCAP_D_OUT)
572 return 0;
573 }
574 }
575 #endif
576
577 #ifdef HAVE_PF_PACKET_SOCKETS
578 /*
579 * If this is a cooked device, fill in the fake packet header.
580 */
581 if (handle->md.cooked) {
582 /*
583 * Add the length of the fake header to the length
584 * of packet data we read.
585 */
586 packet_len += SLL_HDR_LEN;
587
588 hdrp = (struct sll_header *)bp;
589
590 /*
591 * Map the PACKET_ value to a LINUX_SLL_ value; we
592 * want the same numerical value to be used in
593 * the link-layer header even if the numerical values
594 * for the PACKET_ #defines change, so that programs
595 * that look at the packet type field will always be
596 * able to handle DLT_LINUX_SLL captures.
597 */
598 switch (from.sll_pkttype) {
599
600 case PACKET_HOST:
601 hdrp->sll_pkttype = htons(LINUX_SLL_HOST);
602 break;
603
604 case PACKET_BROADCAST:
605 hdrp->sll_pkttype = htons(LINUX_SLL_BROADCAST);
606 break;
607
608 case PACKET_MULTICAST:
609 hdrp->sll_pkttype = htons(LINUX_SLL_MULTICAST);
610 break;
611
612 case PACKET_OTHERHOST:
613 hdrp->sll_pkttype = htons(LINUX_SLL_OTHERHOST);
614 break;
615
616 case PACKET_OUTGOING:
617 hdrp->sll_pkttype = htons(LINUX_SLL_OUTGOING);
618 break;
619
620 default:
621 hdrp->sll_pkttype = -1;
622 break;
623 }
624
625 hdrp->sll_hatype = htons(from.sll_hatype);
626 hdrp->sll_halen = htons(from.sll_halen);
627 memcpy(hdrp->sll_addr, from.sll_addr,
628 (from.sll_halen > SLL_ADDRLEN) ?
629 SLL_ADDRLEN :
630 from.sll_halen);
631 hdrp->sll_protocol = from.sll_protocol;
632 }
633 #endif
634
635 /*
636 * XXX: According to the kernel source we should get the real
637 * packet len if calling recvfrom with MSG_TRUNC set. It does
638 * not seem to work here :(, but it is supported by this code
639 * anyway.
640 * To be honest the code RELIES on that feature so this is really
641 * broken with 2.2.x kernels.
642 * I spend a day to figure out what's going on and I found out
643 * that the following is happening:
644 *
645 * The packet comes from a random interface and the packet_rcv
646 * hook is called with a clone of the packet. That code inserts
647 * the packet into the receive queue of the packet socket.
648 * If a filter is attached to that socket that filter is run
649 * first - and there lies the problem. The default filter always
650 * cuts the packet at the snaplen:
651 *
652 * # tcpdump -d
653 * (000) ret #68
654 *
655 * So the packet filter cuts down the packet. The recvfrom call
656 * says "hey, it's only 68 bytes, it fits into the buffer" with
657 * the result that we don't get the real packet length. This
658 * is valid at least until kernel 2.2.17pre6.
659 *
660 * We currently handle this by making a copy of the filter
661 * program, fixing all "ret" instructions with non-zero
662 * operands to have an operand of 65535 so that the filter
663 * doesn't truncate the packet, and supplying that modified
664 * filter to the kernel.
665 */
666
667 caplen = packet_len;
668 if (caplen > handle->snapshot)
669 caplen = handle->snapshot;
670
671 /* Run the packet filter if not using kernel filter */
672 if (!handle->md.use_bpf && handle->fcode.bf_insns) {
673 if (bpf_filter(handle->fcode.bf_insns, bp,
674 packet_len, caplen) == 0)
675 {
676 /* rejected by filter */
677 return 0;
678 }
679 }
680
681 /* Fill in our own header data */
682
683 if (ioctl(handle->fd, SIOCGSTAMP, &pcap_header.ts) == -1) {
684 snprintf(handle->errbuf, sizeof(handle->errbuf),
685 "SIOCGSTAMP: %s", pcap_strerror(errno));
686 return -1;
687 }
688 pcap_header.caplen = caplen;
689 pcap_header.len = packet_len;
690
691 /*
692 * Count the packet.
693 *
694 * Arguably, we should count them before we check the filter,
695 * as on many other platforms "ps_recv" counts packets
696 * handed to the filter rather than packets that passed
697 * the filter, but if filtering is done in the kernel, we
698 * can't get a count of packets that passed the filter,
699 * and that would mean the meaning of "ps_recv" wouldn't
700 * be the same on all Linux systems.
701 *
702 * XXX - it's not the same on all systems in any case;
703 * ideally, we should have a "get the statistics" call
704 * that supplies more counts and indicates which of them
705 * it supplies, so that we supply a count of packets
706 * handed to the filter only on platforms where that
707 * information is available.
708 *
709 * We count them here even if we can get the packet count
710 * from the kernel, as we can only determine at run time
711 * whether we'll be able to get it from the kernel (if
712 * HAVE_TPACKET_STATS isn't defined, we can't get it from
713 * the kernel, but if it is defined, the library might
714 * have been built with a 2.4 or later kernel, but we
715 * might be running on a 2.2[.x] kernel without Alexey
716 * Kuznetzov's turbopacket patches, and thus the kernel
717 * might not be able to supply those statistics). We
718 * could, I guess, try, when opening the socket, to get
719 * the statistics, and if we can not increment the count
720 * here, but it's not clear that always incrementing
721 * the count is more expensive than always testing a flag
722 * in memory.
723 *
724 * We keep the count in "md.packets_read", and use that for
725 * "ps_recv" if we can't get the statistics from the kernel.
726 * We do that because, if we *can* get the statistics from
727 * the kernel, we use "md.stat.ps_recv" and "md.stat.ps_drop"
728 * as running counts, as reading the statistics from the
729 * kernel resets the kernel statistics, and if we directly
730 * increment "md.stat.ps_recv" here, that means it will
731 * count packets *twice* on systems where we can get kernel
732 * statistics - once here, and once in pcap_stats_linux().
733 */
734 handle->md.packets_read++;
735
736 /* Call the user supplied callback function */
737 callback(userdata, &pcap_header, bp);
738
739 return 1;
740 }
741
742 static int
pcap_inject_linux(pcap_t * handle,const void * buf,size_t size)743 pcap_inject_linux(pcap_t *handle, const void *buf, size_t size)
744 {
745 int ret;
746
747 #ifdef HAVE_PF_PACKET_SOCKETS
748 if (!handle->md.sock_packet) {
749 /* PF_PACKET socket */
750 if (handle->md.ifindex == -1) {
751 /*
752 * We don't support sending on the "any" device.
753 */
754 strlcpy(handle->errbuf,
755 "Sending packets isn't supported on the \"any\" device",
756 PCAP_ERRBUF_SIZE);
757 return (-1);
758 }
759
760 if (handle->md.cooked) {
761 /*
762 * We don't support sending on the "any" device.
763 *
764 * XXX - how do you send on a bound cooked-mode
765 * socket?
766 * Is a "sendto()" required there?
767 */
768 strlcpy(handle->errbuf,
769 "Sending packets isn't supported in cooked mode",
770 PCAP_ERRBUF_SIZE);
771 return (-1);
772 }
773 }
774 #endif
775
776 ret = send(handle->fd, buf, size, 0);
777 if (ret == -1) {
778 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "send: %s",
779 pcap_strerror(errno));
780 return (-1);
781 }
782 return (ret);
783 }
784
785 /*
786 * Get the statistics for the given packet capture handle.
787 * Reports the number of dropped packets iff the kernel supports
788 * the PACKET_STATISTICS "getsockopt()" argument (2.4 and later
789 * kernels, and 2.2[.x] kernels with Alexey Kuznetzov's turbopacket
790 * patches); otherwise, that information isn't available, and we lie
791 * and report 0 as the count of dropped packets.
792 */
793 static int
pcap_stats_linux(pcap_t * handle,struct pcap_stat * stats)794 pcap_stats_linux(pcap_t *handle, struct pcap_stat *stats)
795 {
796 #ifdef HAVE_TPACKET_STATS
797 struct tpacket_stats kstats;
798 socklen_t len = sizeof (struct tpacket_stats);
799 #endif
800
801 #ifdef HAVE_TPACKET_STATS
802 /*
803 * Try to get the packet counts from the kernel.
804 */
805 if (getsockopt(handle->fd, SOL_PACKET, PACKET_STATISTICS,
806 &kstats, &len) > -1) {
807 /*
808 * On systems where the PACKET_STATISTICS "getsockopt()"
809 * argument is supported on PF_PACKET sockets:
810 *
811 * "ps_recv" counts only packets that *passed* the
812 * filter, not packets that didn't pass the filter.
813 * This includes packets later dropped because we
814 * ran out of buffer space.
815 *
816 * "ps_drop" counts packets dropped because we ran
817 * out of buffer space. It doesn't count packets
818 * dropped by the interface driver. It counts only
819 * packets that passed the filter.
820 *
821 * Both statistics include packets not yet read from
822 * the kernel by libpcap, and thus not yet seen by
823 * the application.
824 *
825 * In "linux/net/packet/af_packet.c", at least in the
826 * 2.4.9 kernel, "tp_packets" is incremented for every
827 * packet that passes the packet filter *and* is
828 * successfully queued on the socket; "tp_drops" is
829 * incremented for every packet dropped because there's
830 * not enough free space in the socket buffer.
831 *
832 * When the statistics are returned for a PACKET_STATISTICS
833 * "getsockopt()" call, "tp_drops" is added to "tp_packets",
834 * so that "tp_packets" counts all packets handed to
835 * the PF_PACKET socket, including packets dropped because
836 * there wasn't room on the socket buffer - but not
837 * including packets that didn't pass the filter.
838 *
839 * In the BSD BPF, the count of received packets is
840 * incremented for every packet handed to BPF, regardless
841 * of whether it passed the filter.
842 *
843 * We can't make "pcap_stats()" work the same on both
844 * platforms, but the best approximation is to return
845 * "tp_packets" as the count of packets and "tp_drops"
846 * as the count of drops.
847 *
848 * Keep a running total because each call to
849 * getsockopt(handle->fd, SOL_PACKET, PACKET_STATISTICS, ....
850 * resets the counters to zero.
851 */
852 handle->md.stat.ps_recv += kstats.tp_packets;
853 handle->md.stat.ps_drop += kstats.tp_drops;
854 *stats = handle->md.stat;
855 return 0;
856 }
857 else
858 {
859 /*
860 * If the error was EOPNOTSUPP, fall through, so that
861 * if you build the library on a system with
862 * "struct tpacket_stats" and run it on a system
863 * that doesn't, it works as it does if the library
864 * is built on a system without "struct tpacket_stats".
865 */
866 if (errno != EOPNOTSUPP) {
867 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
868 "pcap_stats: %s", pcap_strerror(errno));
869 return -1;
870 }
871 }
872 #endif
873 /*
874 * On systems where the PACKET_STATISTICS "getsockopt()" argument
875 * is not supported on PF_PACKET sockets:
876 *
877 * "ps_recv" counts only packets that *passed* the filter,
878 * not packets that didn't pass the filter. It does not
879 * count packets dropped because we ran out of buffer
880 * space.
881 *
882 * "ps_drop" is not supported.
883 *
884 * "ps_recv" doesn't include packets not yet read from
885 * the kernel by libpcap.
886 *
887 * We maintain the count of packets processed by libpcap in
888 * "md.packets_read", for reasons described in the comment
889 * at the end of pcap_read_packet(). We have no idea how many
890 * packets were dropped.
891 */
892 stats->ps_recv = handle->md.packets_read;
893 stats->ps_drop = 0;
894 return 0;
895 }
896
897 /*
898 * Description string for the "any" device.
899 */
900 static const char any_descr[] = "Pseudo-device that captures on all interfaces";
901
902 int
pcap_platform_finddevs(pcap_if_t ** alldevsp,char * errbuf)903 pcap_platform_finddevs(pcap_if_t **alldevsp, char *errbuf)
904 {
905 if (pcap_add_if(alldevsp, "any", 0, any_descr, errbuf) < 0)
906 return (-1);
907
908 #ifdef HAVE_DAG_API
909 if (dag_platform_finddevs(alldevsp, errbuf) < 0)
910 return (-1);
911 #endif /* HAVE_DAG_API */
912
913 #ifdef HAVE_SEPTEL_API
914 if (septel_platform_finddevs(alldevsp, errbuf) < 0)
915 return (-1);
916 #endif /* HAVE_SEPTEL_API */
917
918 return (0);
919 }
920
921 /*
922 * Attach the given BPF code to the packet capture device.
923 */
924 static int
pcap_setfilter_linux(pcap_t * handle,struct bpf_program * filter)925 pcap_setfilter_linux(pcap_t *handle, struct bpf_program *filter)
926 {
927 #ifdef SO_ATTACH_FILTER
928 struct sock_fprog fcode;
929 int can_filter_in_kernel;
930 int err = 0;
931 #endif
932
933 if (!handle)
934 return -1;
935 if (!filter) {
936 strncpy(handle->errbuf, "setfilter: No filter specified",
937 sizeof(handle->errbuf));
938 return -1;
939 }
940
941 /* Make our private copy of the filter */
942
943 if (install_bpf_program(handle, filter) < 0)
944 /* install_bpf_program() filled in errbuf */
945 return -1;
946
947 /*
948 * Run user level packet filter by default. Will be overriden if
949 * installing a kernel filter succeeds.
950 */
951 handle->md.use_bpf = 0;
952
953 /* Install kernel level filter if possible */
954
955 #ifdef SO_ATTACH_FILTER
956 #ifdef USHRT_MAX
957 if (handle->fcode.bf_len > USHRT_MAX) {
958 /*
959 * fcode.len is an unsigned short for current kernel.
960 * I have yet to see BPF-Code with that much
961 * instructions but still it is possible. So for the
962 * sake of correctness I added this check.
963 */
964 fprintf(stderr, "Warning: Filter too complex for kernel\n");
965 fcode.len = 0;
966 fcode.filter = NULL;
967 can_filter_in_kernel = 0;
968 } else
969 #endif /* USHRT_MAX */
970 {
971 /*
972 * Oh joy, the Linux kernel uses struct sock_fprog instead
973 * of struct bpf_program and of course the length field is
974 * of different size. Pointed out by Sebastian
975 *
976 * Oh, and we also need to fix it up so that all "ret"
977 * instructions with non-zero operands have 65535 as the
978 * operand, and so that, if we're in cooked mode, all
979 * memory-reference instructions use special magic offsets
980 * in references to the link-layer header and assume that
981 * the link-layer payload begins at 0; "fix_program()"
982 * will do that.
983 */
984 switch (fix_program(handle, &fcode)) {
985
986 case -1:
987 default:
988 /*
989 * Fatal error; just quit.
990 * (The "default" case shouldn't happen; we
991 * return -1 for that reason.)
992 */
993 return -1;
994
995 case 0:
996 /*
997 * The program performed checks that we can't make
998 * work in the kernel.
999 */
1000 can_filter_in_kernel = 0;
1001 break;
1002
1003 case 1:
1004 /*
1005 * We have a filter that'll work in the kernel.
1006 */
1007 can_filter_in_kernel = 1;
1008 break;
1009 }
1010 }
1011
1012 if (can_filter_in_kernel) {
1013 if ((err = set_kernel_filter(handle, &fcode)) == 0)
1014 {
1015 /* Installation succeded - using kernel filter. */
1016 handle->md.use_bpf = 1;
1017 }
1018 else if (err == -1) /* Non-fatal error */
1019 {
1020 /*
1021 * Print a warning if we weren't able to install
1022 * the filter for a reason other than "this kernel
1023 * isn't configured to support socket filters.
1024 */
1025 if (errno != ENOPROTOOPT && errno != EOPNOTSUPP) {
1026 fprintf(stderr,
1027 "Warning: Kernel filter failed: %s\n",
1028 pcap_strerror(errno));
1029 }
1030 }
1031 }
1032
1033 /*
1034 * If we're not using the kernel filter, get rid of any kernel
1035 * filter that might've been there before, e.g. because the
1036 * previous filter could work in the kernel, or because some other
1037 * code attached a filter to the socket by some means other than
1038 * calling "pcap_setfilter()". Otherwise, the kernel filter may
1039 * filter out packets that would pass the new userland filter.
1040 */
1041 if (!handle->md.use_bpf)
1042 reset_kernel_filter(handle);
1043
1044 /*
1045 * Free up the copy of the filter that was made by "fix_program()".
1046 */
1047 if (fcode.filter != NULL)
1048 free(fcode.filter);
1049
1050 if (err == -2)
1051 /* Fatal error */
1052 return -1;
1053 #endif /* SO_ATTACH_FILTER */
1054
1055 return 0;
1056 }
1057
1058 /*
1059 * Set direction flag: Which packets do we accept on a forwarding
1060 * single device? IN, OUT or both?
1061 */
1062 static int
pcap_setdirection_linux(pcap_t * handle,pcap_direction_t d)1063 pcap_setdirection_linux(pcap_t *handle, pcap_direction_t d)
1064 {
1065 #ifdef HAVE_PF_PACKET_SOCKETS
1066 if (!handle->md.sock_packet) {
1067 handle->direction = d;
1068 return 0;
1069 }
1070 #endif
1071 /*
1072 * We're not using PF_PACKET sockets, so we can't determine
1073 * the direction of the packet.
1074 */
1075 snprintf(handle->errbuf, sizeof(handle->errbuf),
1076 "Setting direction is not supported on SOCK_PACKET sockets");
1077 return -1;
1078 }
1079
1080 /*
1081 * Linux uses the ARP hardware type to identify the type of an
1082 * interface. pcap uses the DLT_xxx constants for this. This
1083 * function takes a pointer to a "pcap_t", and an ARPHRD_xxx
1084 * constant, as arguments, and sets "handle->linktype" to the
1085 * appropriate DLT_XXX constant and sets "handle->offset" to
1086 * the appropriate value (to make "handle->offset" plus link-layer
1087 * header length be a multiple of 4, so that the link-layer payload
1088 * will be aligned on a 4-byte boundary when capturing packets).
1089 * (If the offset isn't set here, it'll be 0; add code as appropriate
1090 * for cases where it shouldn't be 0.)
1091 *
1092 * If "cooked_ok" is non-zero, we can use DLT_LINUX_SLL and capture
1093 * in cooked mode; otherwise, we can't use cooked mode, so we have
1094 * to pick some type that works in raw mode, or fail.
1095 *
1096 * Sets the link type to -1 if unable to map the type.
1097 */
map_arphrd_to_dlt(pcap_t * handle,int arptype,int cooked_ok)1098 static void map_arphrd_to_dlt(pcap_t *handle, int arptype, int cooked_ok)
1099 {
1100 switch (arptype) {
1101
1102 case ARPHRD_ETHER:
1103 /*
1104 * This is (presumably) a real Ethernet capture; give it a
1105 * link-layer-type list with DLT_EN10MB and DLT_DOCSIS, so
1106 * that an application can let you choose it, in case you're
1107 * capturing DOCSIS traffic that a Cisco Cable Modem
1108 * Termination System is putting out onto an Ethernet (it
1109 * doesn't put an Ethernet header onto the wire, it puts raw
1110 * DOCSIS frames out on the wire inside the low-level
1111 * Ethernet framing).
1112 *
1113 * XXX - are there any sorts of "fake Ethernet" that have
1114 * ARPHRD_ETHER but that *shouldn't offer DLT_DOCSIS as
1115 * a Cisco CMTS won't put traffic onto it or get traffic
1116 * bridged onto it? ISDN is handled in "live_open_new()",
1117 * as we fall back on cooked mode there; are there any
1118 * others?
1119 */
1120 handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
1121 /*
1122 * If that fails, just leave the list empty.
1123 */
1124 if (handle->dlt_list != NULL) {
1125 handle->dlt_list[0] = DLT_EN10MB;
1126 handle->dlt_list[1] = DLT_DOCSIS;
1127 handle->dlt_count = 2;
1128 }
1129 /* FALLTHROUGH */
1130
1131 case ARPHRD_METRICOM:
1132 case ARPHRD_LOOPBACK:
1133 handle->linktype = DLT_EN10MB;
1134 handle->offset = 2;
1135 break;
1136
1137 case ARPHRD_EETHER:
1138 handle->linktype = DLT_EN3MB;
1139 break;
1140
1141 case ARPHRD_AX25:
1142 handle->linktype = DLT_AX25;
1143 break;
1144
1145 case ARPHRD_PRONET:
1146 handle->linktype = DLT_PRONET;
1147 break;
1148
1149 case ARPHRD_CHAOS:
1150 handle->linktype = DLT_CHAOS;
1151 break;
1152
1153 #ifndef ARPHRD_IEEE802_TR
1154 #define ARPHRD_IEEE802_TR 800 /* From Linux 2.4 */
1155 #endif
1156 case ARPHRD_IEEE802_TR:
1157 case ARPHRD_IEEE802:
1158 handle->linktype = DLT_IEEE802;
1159 handle->offset = 2;
1160 break;
1161
1162 case ARPHRD_ARCNET:
1163 handle->linktype = DLT_ARCNET_LINUX;
1164 break;
1165
1166 #ifndef ARPHRD_FDDI /* From Linux 2.2.13 */
1167 #define ARPHRD_FDDI 774
1168 #endif
1169 case ARPHRD_FDDI:
1170 handle->linktype = DLT_FDDI;
1171 handle->offset = 3;
1172 break;
1173
1174 #ifndef ARPHRD_ATM /* FIXME: How to #include this? */
1175 #define ARPHRD_ATM 19
1176 #endif
1177 case ARPHRD_ATM:
1178 /*
1179 * The Classical IP implementation in ATM for Linux
1180 * supports both what RFC 1483 calls "LLC Encapsulation",
1181 * in which each packet has an LLC header, possibly
1182 * with a SNAP header as well, prepended to it, and
1183 * what RFC 1483 calls "VC Based Multiplexing", in which
1184 * different virtual circuits carry different network
1185 * layer protocols, and no header is prepended to packets.
1186 *
1187 * They both have an ARPHRD_ type of ARPHRD_ATM, so
1188 * you can't use the ARPHRD_ type to find out whether
1189 * captured packets will have an LLC header, and,
1190 * while there's a socket ioctl to *set* the encapsulation
1191 * type, there's no ioctl to *get* the encapsulation type.
1192 *
1193 * This means that
1194 *
1195 * programs that dissect Linux Classical IP frames
1196 * would have to check for an LLC header and,
1197 * depending on whether they see one or not, dissect
1198 * the frame as LLC-encapsulated or as raw IP (I
1199 * don't know whether there's any traffic other than
1200 * IP that would show up on the socket, or whether
1201 * there's any support for IPv6 in the Linux
1202 * Classical IP code);
1203 *
1204 * filter expressions would have to compile into
1205 * code that checks for an LLC header and does
1206 * the right thing.
1207 *
1208 * Both of those are a nuisance - and, at least on systems
1209 * that support PF_PACKET sockets, we don't have to put
1210 * up with those nuisances; instead, we can just capture
1211 * in cooked mode. That's what we'll do, if we can.
1212 * Otherwise, we'll just fail.
1213 */
1214 if (cooked_ok)
1215 handle->linktype = DLT_LINUX_SLL;
1216 else
1217 handle->linktype = -1;
1218 break;
1219
1220 #ifndef ARPHRD_IEEE80211 /* From Linux 2.4.6 */
1221 #define ARPHRD_IEEE80211 801
1222 #endif
1223 case ARPHRD_IEEE80211:
1224 handle->linktype = DLT_IEEE802_11;
1225 break;
1226
1227 #ifndef ARPHRD_IEEE80211_PRISM /* From Linux 2.4.18 */
1228 #define ARPHRD_IEEE80211_PRISM 802
1229 #endif
1230 case ARPHRD_IEEE80211_PRISM:
1231 handle->linktype = DLT_PRISM_HEADER;
1232 break;
1233
1234 #ifndef ARPHRD_IEEE80211_RADIOTAP /* new */
1235 #define ARPHRD_IEEE80211_RADIOTAP 803
1236 #endif
1237 case ARPHRD_IEEE80211_RADIOTAP:
1238 handle->linktype = DLT_IEEE802_11_RADIO;
1239 break;
1240
1241 case ARPHRD_PPP:
1242 /*
1243 * Some PPP code in the kernel supplies no link-layer
1244 * header whatsoever to PF_PACKET sockets; other PPP
1245 * code supplies PPP link-layer headers ("syncppp.c");
1246 * some PPP code might supply random link-layer
1247 * headers (PPP over ISDN - there's code in Ethereal,
1248 * for example, to cope with PPP-over-ISDN captures
1249 * with which the Ethereal developers have had to cope,
1250 * heuristically trying to determine which of the
1251 * oddball link-layer headers particular packets have).
1252 *
1253 * As such, we just punt, and run all PPP interfaces
1254 * in cooked mode, if we can; otherwise, we just treat
1255 * it as DLT_RAW, for now - if somebody needs to capture,
1256 * on a 2.0[.x] kernel, on PPP devices that supply a
1257 * link-layer header, they'll have to add code here to
1258 * map to the appropriate DLT_ type (possibly adding a
1259 * new DLT_ type, if necessary).
1260 */
1261 if (cooked_ok)
1262 handle->linktype = DLT_LINUX_SLL;
1263 else {
1264 /*
1265 * XXX - handle ISDN types here? We can't fall
1266 * back on cooked sockets, so we'd have to
1267 * figure out from the device name what type of
1268 * link-layer encapsulation it's using, and map
1269 * that to an appropriate DLT_ value, meaning
1270 * we'd map "isdnN" devices to DLT_RAW (they
1271 * supply raw IP packets with no link-layer
1272 * header) and "isdY" devices to a new DLT_I4L_IP
1273 * type that has only an Ethernet packet type as
1274 * a link-layer header.
1275 *
1276 * But sometimes we seem to get random crap
1277 * in the link-layer header when capturing on
1278 * ISDN devices....
1279 */
1280 handle->linktype = DLT_RAW;
1281 }
1282 break;
1283
1284 #ifndef ARPHRD_CISCO
1285 #define ARPHRD_CISCO 513 /* previously ARPHRD_HDLC */
1286 #endif
1287 case ARPHRD_CISCO:
1288 handle->linktype = DLT_C_HDLC;
1289 break;
1290
1291 /* Not sure if this is correct for all tunnels, but it
1292 * works for CIPE */
1293 case ARPHRD_TUNNEL:
1294 #ifndef ARPHRD_SIT
1295 #define ARPHRD_SIT 776 /* From Linux 2.2.13 */
1296 #endif
1297 case ARPHRD_SIT:
1298 case ARPHRD_CSLIP:
1299 case ARPHRD_SLIP6:
1300 case ARPHRD_CSLIP6:
1301 case ARPHRD_ADAPT:
1302 case ARPHRD_SLIP:
1303 #ifndef ARPHRD_RAWHDLC
1304 #define ARPHRD_RAWHDLC 518
1305 #endif
1306 case ARPHRD_RAWHDLC:
1307 #ifndef ARPHRD_DLCI
1308 #define ARPHRD_DLCI 15
1309 #endif
1310 case ARPHRD_DLCI:
1311 /*
1312 * XXX - should some of those be mapped to DLT_LINUX_SLL
1313 * instead? Should we just map all of them to DLT_LINUX_SLL?
1314 */
1315 handle->linktype = DLT_RAW;
1316 break;
1317
1318 #ifndef ARPHRD_FRAD
1319 #define ARPHRD_FRAD 770
1320 #endif
1321 case ARPHRD_FRAD:
1322 handle->linktype = DLT_FRELAY;
1323 break;
1324
1325 case ARPHRD_LOCALTLK:
1326 handle->linktype = DLT_LTALK;
1327 break;
1328
1329 #ifndef ARPHRD_FCPP
1330 #define ARPHRD_FCPP 784
1331 #endif
1332 case ARPHRD_FCPP:
1333 #ifndef ARPHRD_FCAL
1334 #define ARPHRD_FCAL 785
1335 #endif
1336 case ARPHRD_FCAL:
1337 #ifndef ARPHRD_FCPL
1338 #define ARPHRD_FCPL 786
1339 #endif
1340 case ARPHRD_FCPL:
1341 #ifndef ARPHRD_FCFABRIC
1342 #define ARPHRD_FCFABRIC 787
1343 #endif
1344 case ARPHRD_FCFABRIC:
1345 /*
1346 * We assume that those all mean RFC 2625 IP-over-
1347 * Fibre Channel, with the RFC 2625 header at
1348 * the beginning of the packet.
1349 */
1350 handle->linktype = DLT_IP_OVER_FC;
1351 break;
1352
1353 #ifndef ARPHRD_IRDA
1354 #define ARPHRD_IRDA 783
1355 #endif
1356 case ARPHRD_IRDA:
1357 /* Don't expect IP packet out of this interfaces... */
1358 handle->linktype = DLT_LINUX_IRDA;
1359 /* We need to save packet direction for IrDA decoding,
1360 * so let's use "Linux-cooked" mode. Jean II */
1361 //handle->md.cooked = 1;
1362 break;
1363
1364 /* ARPHRD_LAPD is unofficial and randomly allocated, if reallocation
1365 * is needed, please report it to <daniele@orlandi.com> */
1366 #ifndef ARPHRD_LAPD
1367 #define ARPHRD_LAPD 8445
1368 #endif
1369 case ARPHRD_LAPD:
1370 /* Don't expect IP packet out of this interfaces... */
1371 handle->linktype = DLT_LINUX_LAPD;
1372 break;
1373
1374 default:
1375 handle->linktype = -1;
1376 break;
1377 }
1378 }
1379
1380 /* ===== Functions to interface to the newer kernels ================== */
1381
1382 /*
1383 * Try to open a packet socket using the new kernel interface.
1384 * Returns 0 on failure.
1385 * FIXME: 0 uses to mean success (Sebastian)
1386 */
1387 static int
live_open_new(pcap_t * handle,const char * device,int promisc,int to_ms,char * ebuf)1388 live_open_new(pcap_t *handle, const char *device, int promisc,
1389 int to_ms, char *ebuf)
1390 {
1391 #ifdef HAVE_PF_PACKET_SOCKETS
1392 int sock_fd = -1, arptype;
1393 int err;
1394 int fatal_err = 0;
1395 struct packet_mreq mr;
1396
1397 /* One shot loop used for error handling - bail out with break */
1398
1399 do {
1400 /*
1401 * Open a socket with protocol family packet. If a device is
1402 * given we try to open it in raw mode otherwise we use
1403 * the cooked interface.
1404 */
1405 sock_fd = device ?
1406 socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL))
1407 : socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL));
1408
1409 if (sock_fd == -1) {
1410 snprintf(ebuf, PCAP_ERRBUF_SIZE, "socket: %s",
1411 pcap_strerror(errno) );
1412 break;
1413 }
1414
1415 /* It seems the kernel supports the new interface. */
1416 handle->md.sock_packet = 0;
1417
1418 /*
1419 * Get the interface index of the loopback device.
1420 * If the attempt fails, don't fail, just set the
1421 * "md.lo_ifindex" to -1.
1422 *
1423 * XXX - can there be more than one device that loops
1424 * packets back, i.e. devices other than "lo"? If so,
1425 * we'd need to find them all, and have an array of
1426 * indices for them, and check all of them in
1427 * "pcap_read_packet()".
1428 */
1429 handle->md.lo_ifindex = iface_get_id(sock_fd, "lo", ebuf);
1430
1431 /*
1432 * Default value for offset to align link-layer payload
1433 * on a 4-byte boundary.
1434 */
1435 handle->offset = 0;
1436
1437 /*
1438 * What kind of frames do we have to deal with? Fall back
1439 * to cooked mode if we have an unknown interface type.
1440 */
1441
1442 if (device) {
1443 /* Assume for now we don't need cooked mode. */
1444 handle->md.cooked = 0;
1445
1446 arptype = iface_get_arptype(sock_fd, device, ebuf);
1447 if (arptype == -1) {
1448 fatal_err = 1;
1449 break;
1450 }
1451 map_arphrd_to_dlt(handle, arptype, 1);
1452 if (handle->linktype == -1 ||
1453 handle->linktype == DLT_LINUX_SLL ||
1454 handle->linktype == DLT_LINUX_IRDA ||
1455 handle->linktype == DLT_LINUX_LAPD ||
1456 (handle->linktype == DLT_EN10MB &&
1457 (strncmp("isdn", device, 4) == 0 ||
1458 strncmp("isdY", device, 4) == 0))) {
1459 /*
1460 * Unknown interface type (-1), or a
1461 * device we explicitly chose to run
1462 * in cooked mode (e.g., PPP devices),
1463 * or an ISDN device (whose link-layer
1464 * type we can only determine by using
1465 * APIs that may be different on different
1466 * kernels) - reopen in cooked mode.
1467 */
1468 if (close(sock_fd) == -1) {
1469 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1470 "close: %s", pcap_strerror(errno));
1471 break;
1472 }
1473 sock_fd = socket(PF_PACKET, SOCK_DGRAM,
1474 htons(ETH_P_ALL));
1475 if (sock_fd == -1) {
1476 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1477 "socket: %s", pcap_strerror(errno));
1478 break;
1479 }
1480 handle->md.cooked = 1;
1481
1482 /*
1483 * Get rid of any link-layer type list
1484 * we allocated - this only supports cooked
1485 * capture.
1486 */
1487 if (handle->dlt_list != NULL) {
1488 free(handle->dlt_list);
1489 handle->dlt_list = NULL;
1490 handle->dlt_count = 0;
1491 }
1492
1493 if (handle->linktype == -1) {
1494 /*
1495 * Warn that we're falling back on
1496 * cooked mode; we may want to
1497 * update "map_arphrd_to_dlt()"
1498 * to handle the new type.
1499 */
1500 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1501 "arptype %d not "
1502 "supported by libpcap - "
1503 "falling back to cooked "
1504 "socket",
1505 arptype);
1506 }
1507 /* IrDA capture is not a real "cooked" capture,
1508 * it's IrLAP frames, not IP packets. */
1509 if (handle->linktype != DLT_LINUX_IRDA &&
1510 handle->linktype != DLT_LINUX_LAPD)
1511 handle->linktype = DLT_LINUX_SLL;
1512 }
1513
1514 handle->md.ifindex = iface_get_id(sock_fd, device, ebuf);
1515 if (handle->md.ifindex == -1)
1516 break;
1517
1518 if ((err = iface_bind(sock_fd, handle->md.ifindex,
1519 ebuf)) < 0) {
1520 if (err == -2)
1521 fatal_err = 1;
1522 break;
1523 }
1524 } else {
1525 /*
1526 * This is cooked mode.
1527 */
1528 handle->md.cooked = 1;
1529 handle->linktype = DLT_LINUX_SLL;
1530
1531 /*
1532 * We're not bound to a device.
1533 * XXX - true? Or true only if we're using
1534 * the "any" device?
1535 * For now, we're using this as an indication
1536 * that we can't transmit; stop doing that only
1537 * if we figure out how to transmit in cooked
1538 * mode.
1539 */
1540 handle->md.ifindex = -1;
1541 }
1542
1543 /*
1544 * Select promiscuous mode on if "promisc" is set.
1545 *
1546 * Do not turn allmulti mode on if we don't select
1547 * promiscuous mode - on some devices (e.g., Orinoco
1548 * wireless interfaces), allmulti mode isn't supported
1549 * and the driver implements it by turning promiscuous
1550 * mode on, and that screws up the operation of the
1551 * card as a normal networking interface, and on no
1552 * other platform I know of does starting a non-
1553 * promiscuous capture affect which multicast packets
1554 * are received by the interface.
1555 */
1556
1557 /*
1558 * Hmm, how can we set promiscuous mode on all interfaces?
1559 * I am not sure if that is possible at all.
1560 */
1561
1562 if (device && promisc) {
1563 memset(&mr, 0, sizeof(mr));
1564 mr.mr_ifindex = handle->md.ifindex;
1565 mr.mr_type = PACKET_MR_PROMISC;
1566 if (setsockopt(sock_fd, SOL_PACKET,
1567 PACKET_ADD_MEMBERSHIP, &mr, sizeof(mr)) == -1)
1568 {
1569 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1570 "setsockopt: %s", pcap_strerror(errno));
1571 break;
1572 }
1573 }
1574
1575 /* Save the socket FD in the pcap structure */
1576
1577 handle->fd = sock_fd;
1578
1579 return 1;
1580
1581 } while(0);
1582
1583 if (sock_fd != -1)
1584 close(sock_fd);
1585
1586 if (fatal_err) {
1587 /*
1588 * Get rid of any link-layer type list we allocated.
1589 */
1590 if (handle->dlt_list != NULL)
1591 free(handle->dlt_list);
1592 return -2;
1593 } else
1594 return 0;
1595 #else
1596 strncpy(ebuf,
1597 "New packet capturing interface not supported by build "
1598 "environment", PCAP_ERRBUF_SIZE);
1599 return 0;
1600 #endif
1601 }
1602
1603 #ifdef HAVE_PF_PACKET_SOCKETS
1604 /*
1605 * Return the index of the given device name. Fill ebuf and return
1606 * -1 on failure.
1607 */
1608 static int
iface_get_id(int fd,const char * device,char * ebuf)1609 iface_get_id(int fd, const char *device, char *ebuf)
1610 {
1611 struct ifreq ifr;
1612
1613 memset(&ifr, 0, sizeof(ifr));
1614 strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
1615
1616 if (ioctl(fd, SIOCGIFINDEX, &ifr) == -1) {
1617 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1618 "SIOCGIFINDEX: %s", pcap_strerror(errno));
1619 return -1;
1620 }
1621
1622 return ifr.ifr_ifindex;
1623 }
1624
1625 /*
1626 * Bind the socket associated with FD to the given device.
1627 */
1628 static int
iface_bind(int fd,int ifindex,char * ebuf)1629 iface_bind(int fd, int ifindex, char *ebuf)
1630 {
1631 struct sockaddr_ll sll;
1632 int err;
1633 socklen_t errlen = sizeof(err);
1634
1635 memset(&sll, 0, sizeof(sll));
1636 sll.sll_family = AF_PACKET;
1637 sll.sll_ifindex = ifindex;
1638 sll.sll_protocol = htons(ETH_P_ALL);
1639
1640 if (bind(fd, (struct sockaddr *) &sll, sizeof(sll)) == -1) {
1641 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1642 "bind: %s", pcap_strerror(errno));
1643 return -1;
1644 }
1645
1646 /* Any pending errors, e.g., network is down? */
1647
1648 if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &errlen) == -1) {
1649 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1650 "getsockopt: %s", pcap_strerror(errno));
1651 return -2;
1652 }
1653
1654 if (err > 0) {
1655 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1656 "bind: %s", pcap_strerror(err));
1657 return -2;
1658 }
1659
1660 return 0;
1661 }
1662
1663 #endif
1664
1665
1666 /* ===== Functions to interface to the older kernels ================== */
1667
1668 /*
1669 * With older kernels promiscuous mode is kind of interesting because we
1670 * have to reset the interface before exiting. The problem can't really
1671 * be solved without some daemon taking care of managing usage counts.
1672 * If we put the interface into promiscuous mode, we set a flag indicating
1673 * that we must take it out of that mode when the interface is closed,
1674 * and, when closing the interface, if that flag is set we take it out
1675 * of promiscuous mode.
1676 */
1677
1678 /*
1679 * List of pcaps for which we turned promiscuous mode on by hand.
1680 * If there are any such pcaps, we arrange to call "pcap_close_all()"
1681 * when we exit, and have it close all of them to turn promiscuous mode
1682 * off.
1683 */
1684 static struct pcap *pcaps_to_close;
1685
1686 /*
1687 * TRUE if we've already called "atexit()" to cause "pcap_close_all()" to
1688 * be called on exit.
1689 */
1690 static int did_atexit;
1691
pcap_close_all(void)1692 static void pcap_close_all(void)
1693 {
1694 struct pcap *handle;
1695
1696 while ((handle = pcaps_to_close) != NULL)
1697 pcap_close(handle);
1698 }
1699
pcap_close_linux(pcap_t * handle)1700 static void pcap_close_linux( pcap_t *handle )
1701 {
1702 struct pcap *p, *prevp;
1703 struct ifreq ifr;
1704
1705 if (handle->md.clear_promisc) {
1706 /*
1707 * We put the interface into promiscuous mode; take
1708 * it out of promiscuous mode.
1709 *
1710 * XXX - if somebody else wants it in promiscuous mode,
1711 * this code cannot know that, so it'll take it out
1712 * of promiscuous mode. That's not fixable in 2.0[.x]
1713 * kernels.
1714 */
1715 memset(&ifr, 0, sizeof(ifr));
1716 strncpy(ifr.ifr_name, handle->md.device, sizeof(ifr.ifr_name));
1717 if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) == -1) {
1718 fprintf(stderr,
1719 "Can't restore interface flags (SIOCGIFFLAGS failed: %s).\n"
1720 "Please adjust manually.\n"
1721 "Hint: This can't happen with Linux >= 2.2.0.\n",
1722 strerror(errno));
1723 } else {
1724 if (ifr.ifr_flags & IFF_PROMISC) {
1725 /*
1726 * Promiscuous mode is currently on; turn it
1727 * off.
1728 */
1729 ifr.ifr_flags &= ~IFF_PROMISC;
1730 if (ioctl(handle->fd, SIOCSIFFLAGS, &ifr) == -1) {
1731 fprintf(stderr,
1732 "Can't restore interface flags (SIOCSIFFLAGS failed: %s).\n"
1733 "Please adjust manually.\n"
1734 "Hint: This can't happen with Linux >= 2.2.0.\n",
1735 strerror(errno));
1736 }
1737 }
1738 }
1739
1740 /*
1741 * Take this pcap out of the list of pcaps for which we
1742 * have to take the interface out of promiscuous mode.
1743 */
1744 for (p = pcaps_to_close, prevp = NULL; p != NULL;
1745 prevp = p, p = p->md.next) {
1746 if (p == handle) {
1747 /*
1748 * Found it. Remove it from the list.
1749 */
1750 if (prevp == NULL) {
1751 /*
1752 * It was at the head of the list.
1753 */
1754 pcaps_to_close = p->md.next;
1755 } else {
1756 /*
1757 * It was in the middle of the list.
1758 */
1759 prevp->md.next = p->md.next;
1760 }
1761 break;
1762 }
1763 }
1764 }
1765
1766 if (handle->md.device != NULL)
1767 free(handle->md.device);
1768 handle->md.device = NULL;
1769 pcap_close_common(handle);
1770 }
1771
1772 /*
1773 * Try to open a packet socket using the old kernel interface.
1774 * Returns 0 on failure.
1775 * FIXME: 0 uses to mean success (Sebastian)
1776 */
1777 static int
live_open_old(pcap_t * handle,const char * device,int promisc,int to_ms,char * ebuf)1778 live_open_old(pcap_t *handle, const char *device, int promisc,
1779 int to_ms, char *ebuf)
1780 {
1781 int arptype;
1782 struct ifreq ifr;
1783
1784 do {
1785 /* Open the socket */
1786
1787 handle->fd = socket(PF_INET, SOCK_PACKET, htons(ETH_P_ALL));
1788 if (handle->fd == -1) {
1789 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1790 "socket: %s", pcap_strerror(errno));
1791 break;
1792 }
1793
1794 /* It worked - we are using the old interface */
1795 handle->md.sock_packet = 1;
1796
1797 /* ...which means we get the link-layer header. */
1798 handle->md.cooked = 0;
1799
1800 /* Bind to the given device */
1801
1802 if (!device) {
1803 strncpy(ebuf, "pcap_open_live: The \"any\" device isn't supported on 2.0[.x]-kernel systems",
1804 PCAP_ERRBUF_SIZE);
1805 break;
1806 }
1807 if (iface_bind_old(handle->fd, device, ebuf) == -1)
1808 break;
1809
1810 /*
1811 * Try to get the link-layer type.
1812 */
1813 arptype = iface_get_arptype(handle->fd, device, ebuf);
1814 if (arptype == -1)
1815 break;
1816
1817 /*
1818 * Try to find the DLT_ type corresponding to that
1819 * link-layer type.
1820 */
1821 map_arphrd_to_dlt(handle, arptype, 0);
1822 if (handle->linktype == -1) {
1823 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1824 "unknown arptype %d", arptype);
1825 break;
1826 }
1827
1828 /* Go to promisc mode if requested */
1829
1830 if (promisc) {
1831 memset(&ifr, 0, sizeof(ifr));
1832 strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
1833 if (ioctl(handle->fd, SIOCGIFFLAGS, &ifr) == -1) {
1834 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1835 "SIOCGIFFLAGS: %s", pcap_strerror(errno));
1836 break;
1837 }
1838 if ((ifr.ifr_flags & IFF_PROMISC) == 0) {
1839 /*
1840 * Promiscuous mode isn't currently on,
1841 * so turn it on, and remember that
1842 * we should turn it off when the
1843 * pcap_t is closed.
1844 */
1845
1846 /*
1847 * If we haven't already done so, arrange
1848 * to have "pcap_close_all()" called when
1849 * we exit.
1850 */
1851 if (!did_atexit) {
1852 if (atexit(pcap_close_all) == -1) {
1853 /*
1854 * "atexit()" failed; don't
1855 * put the interface in
1856 * promiscuous mode, just
1857 * give up.
1858 */
1859 strncpy(ebuf, "atexit failed",
1860 PCAP_ERRBUF_SIZE);
1861 break;
1862 }
1863 did_atexit = 1;
1864 }
1865
1866 ifr.ifr_flags |= IFF_PROMISC;
1867 if (ioctl(handle->fd, SIOCSIFFLAGS, &ifr) == -1) {
1868 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1869 "SIOCSIFFLAGS: %s",
1870 pcap_strerror(errno));
1871 break;
1872 }
1873 handle->md.clear_promisc = 1;
1874
1875 /*
1876 * Add this to the list of pcaps
1877 * to close when we exit.
1878 */
1879 handle->md.next = pcaps_to_close;
1880 pcaps_to_close = handle;
1881 }
1882 }
1883
1884 /*
1885 * Default value for offset to align link-layer payload
1886 * on a 4-byte boundary.
1887 */
1888 handle->offset = 0;
1889
1890 return 1;
1891
1892 } while (0);
1893
1894 pcap_close_linux(handle);
1895 return 0;
1896 }
1897
1898 /*
1899 * Bind the socket associated with FD to the given device using the
1900 * interface of the old kernels.
1901 */
1902 static int
iface_bind_old(int fd,const char * device,char * ebuf)1903 iface_bind_old(int fd, const char *device, char *ebuf)
1904 {
1905 struct sockaddr saddr;
1906 int err;
1907 socklen_t errlen = sizeof(err);
1908
1909 memset(&saddr, 0, sizeof(saddr));
1910 strncpy(saddr.sa_data, device, sizeof(saddr.sa_data));
1911 if (bind(fd, &saddr, sizeof(saddr)) == -1) {
1912 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1913 "bind: %s", pcap_strerror(errno));
1914 return -1;
1915 }
1916
1917 /* Any pending errors, e.g., network is down? */
1918
1919 if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &err, &errlen) == -1) {
1920 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1921 "getsockopt: %s", pcap_strerror(errno));
1922 return -1;
1923 }
1924
1925 if (err > 0) {
1926 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1927 "bind: %s", pcap_strerror(err));
1928 return -1;
1929 }
1930
1931 return 0;
1932 }
1933
1934
1935 /* ===== System calls available on all supported kernels ============== */
1936
1937 /*
1938 * Query the kernel for the MTU of the given interface.
1939 */
1940 static int
iface_get_mtu(int fd,const char * device,char * ebuf)1941 iface_get_mtu(int fd, const char *device, char *ebuf)
1942 {
1943 struct ifreq ifr;
1944
1945 if (!device)
1946 return BIGGER_THAN_ALL_MTUS;
1947
1948 memset(&ifr, 0, sizeof(ifr));
1949 strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
1950
1951 if (ioctl(fd, SIOCGIFMTU, &ifr) == -1) {
1952 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1953 "SIOCGIFMTU: %s", pcap_strerror(errno));
1954 return -1;
1955 }
1956
1957 return ifr.ifr_mtu;
1958 }
1959
1960 /*
1961 * Get the hardware type of the given interface as ARPHRD_xxx constant.
1962 */
1963 static int
iface_get_arptype(int fd,const char * device,char * ebuf)1964 iface_get_arptype(int fd, const char *device, char *ebuf)
1965 {
1966 struct ifreq ifr;
1967
1968 memset(&ifr, 0, sizeof(ifr));
1969 strncpy(ifr.ifr_name, device, sizeof(ifr.ifr_name));
1970
1971 if (ioctl(fd, SIOCGIFHWADDR, &ifr) == -1) {
1972 snprintf(ebuf, PCAP_ERRBUF_SIZE,
1973 "SIOCGIFHWADDR: %s", pcap_strerror(errno));
1974 return -1;
1975 }
1976
1977 return ifr.ifr_hwaddr.sa_family;
1978 }
1979
1980 #ifdef SO_ATTACH_FILTER
1981 static int
fix_program(pcap_t * handle,struct sock_fprog * fcode)1982 fix_program(pcap_t *handle, struct sock_fprog *fcode)
1983 {
1984 size_t prog_size;
1985 register int i;
1986 register struct bpf_insn *p;
1987 struct bpf_insn *f;
1988 int len;
1989
1990 /*
1991 * Make a copy of the filter, and modify that copy if
1992 * necessary.
1993 */
1994 prog_size = sizeof(*handle->fcode.bf_insns) * handle->fcode.bf_len;
1995 len = handle->fcode.bf_len;
1996 f = (struct bpf_insn *)malloc(prog_size);
1997 if (f == NULL) {
1998 snprintf(handle->errbuf, sizeof(handle->errbuf),
1999 "malloc: %s", pcap_strerror(errno));
2000 return -1;
2001 }
2002 memcpy(f, handle->fcode.bf_insns, prog_size);
2003 fcode->len = len;
2004 fcode->filter = (struct sock_filter *) f;
2005
2006 for (i = 0; i < len; ++i) {
2007 p = &f[i];
2008 /*
2009 * What type of instruction is this?
2010 */
2011 switch (BPF_CLASS(p->code)) {
2012
2013 case BPF_RET:
2014 /*
2015 * It's a return instruction; is the snapshot
2016 * length a constant, rather than the contents
2017 * of the accumulator?
2018 */
2019 if (BPF_MODE(p->code) == BPF_K) {
2020 /*
2021 * Yes - if the value to be returned,
2022 * i.e. the snapshot length, is anything
2023 * other than 0, make it 65535, so that
2024 * the packet is truncated by "recvfrom()",
2025 * not by the filter.
2026 *
2027 * XXX - there's nothing we can easily do
2028 * if it's getting the value from the
2029 * accumulator; we'd have to insert
2030 * code to force non-zero values to be
2031 * 65535.
2032 */
2033 if (p->k != 0)
2034 p->k = 65535;
2035 }
2036 break;
2037
2038 case BPF_LD:
2039 case BPF_LDX:
2040 /*
2041 * It's a load instruction; is it loading
2042 * from the packet?
2043 */
2044 switch (BPF_MODE(p->code)) {
2045
2046 case BPF_ABS:
2047 case BPF_IND:
2048 case BPF_MSH:
2049 /*
2050 * Yes; are we in cooked mode?
2051 */
2052 if (handle->md.cooked) {
2053 /*
2054 * Yes, so we need to fix this
2055 * instruction.
2056 */
2057 if (fix_offset(p) < 0) {
2058 /*
2059 * We failed to do so.
2060 * Return 0, so our caller
2061 * knows to punt to userland.
2062 */
2063 return 0;
2064 }
2065 }
2066 break;
2067 }
2068 break;
2069 }
2070 }
2071 return 1; /* we succeeded */
2072 }
2073
2074 static int
fix_offset(struct bpf_insn * p)2075 fix_offset(struct bpf_insn *p)
2076 {
2077 /*
2078 * What's the offset?
2079 */
2080 if (p->k >= SLL_HDR_LEN) {
2081 /*
2082 * It's within the link-layer payload; that starts at an
2083 * offset of 0, as far as the kernel packet filter is
2084 * concerned, so subtract the length of the link-layer
2085 * header.
2086 */
2087 p->k -= SLL_HDR_LEN;
2088 } else if (p->k == 14) {
2089 /*
2090 * It's the protocol field; map it to the special magic
2091 * kernel offset for that field.
2092 */
2093 p->k = SKF_AD_OFF + SKF_AD_PROTOCOL;
2094 } else {
2095 /*
2096 * It's within the header, but it's not one of those
2097 * fields; we can't do that in the kernel, so punt
2098 * to userland.
2099 */
2100 return -1;
2101 }
2102 return 0;
2103 }
2104
2105 static int
set_kernel_filter(pcap_t * handle,struct sock_fprog * fcode)2106 set_kernel_filter(pcap_t *handle, struct sock_fprog *fcode)
2107 {
2108 int total_filter_on = 0;
2109 int save_mode;
2110 int ret;
2111 int save_errno;
2112
2113 /*
2114 * The socket filter code doesn't discard all packets queued
2115 * up on the socket when the filter is changed; this means
2116 * that packets that don't match the new filter may show up
2117 * after the new filter is put onto the socket, if those
2118 * packets haven't yet been read.
2119 *
2120 * This means, for example, that if you do a tcpdump capture
2121 * with a filter, the first few packets in the capture might
2122 * be packets that wouldn't have passed the filter.
2123 *
2124 * We therefore discard all packets queued up on the socket
2125 * when setting a kernel filter. (This isn't an issue for
2126 * userland filters, as the userland filtering is done after
2127 * packets are queued up.)
2128 *
2129 * To flush those packets, we put the socket in read-only mode,
2130 * and read packets from the socket until there are no more to
2131 * read.
2132 *
2133 * In order to keep that from being an infinite loop - i.e.,
2134 * to keep more packets from arriving while we're draining
2135 * the queue - we put the "total filter", which is a filter
2136 * that rejects all packets, onto the socket before draining
2137 * the queue.
2138 *
2139 * This code deliberately ignores any errors, so that you may
2140 * get bogus packets if an error occurs, rather than having
2141 * the filtering done in userland even if it could have been
2142 * done in the kernel.
2143 */
2144 if (setsockopt(handle->fd, SOL_SOCKET, SO_ATTACH_FILTER,
2145 &total_fcode, sizeof(total_fcode)) == 0) {
2146 char drain[1];
2147
2148 /*
2149 * Note that we've put the total filter onto the socket.
2150 */
2151 total_filter_on = 1;
2152
2153 /*
2154 * Save the socket's current mode, and put it in
2155 * non-blocking mode; we drain it by reading packets
2156 * until we get an error (which is normally a
2157 * "nothing more to be read" error).
2158 */
2159 save_mode = fcntl(handle->fd, F_GETFL, 0);
2160 if (save_mode != -1 &&
2161 fcntl(handle->fd, F_SETFL, save_mode | O_NONBLOCK) >= 0) {
2162 while (recv(handle->fd, &drain, sizeof drain,
2163 MSG_TRUNC) >= 0)
2164 ;
2165 save_errno = errno;
2166 fcntl(handle->fd, F_SETFL, save_mode);
2167 if (save_errno != EAGAIN) {
2168 /* Fatal error */
2169 reset_kernel_filter(handle);
2170 snprintf(handle->errbuf, sizeof(handle->errbuf),
2171 "recv: %s", pcap_strerror(save_errno));
2172 return -2;
2173 }
2174 }
2175 }
2176
2177 /*
2178 * Now attach the new filter.
2179 */
2180 ret = setsockopt(handle->fd, SOL_SOCKET, SO_ATTACH_FILTER,
2181 fcode, sizeof(*fcode));
2182 if (ret == -1 && total_filter_on) {
2183 /*
2184 * Well, we couldn't set that filter on the socket,
2185 * but we could set the total filter on the socket.
2186 *
2187 * This could, for example, mean that the filter was
2188 * too big to put into the kernel, so we'll have to
2189 * filter in userland; in any case, we'll be doing
2190 * filtering in userland, so we need to remove the
2191 * total filter so we see packets.
2192 */
2193 save_errno = errno;
2194
2195 /*
2196 * XXX - if this fails, we're really screwed;
2197 * we have the total filter on the socket,
2198 * and it won't come off. What do we do then?
2199 */
2200 reset_kernel_filter(handle);
2201
2202 errno = save_errno;
2203 }
2204 return ret;
2205 }
2206
2207 static int
reset_kernel_filter(pcap_t * handle)2208 reset_kernel_filter(pcap_t *handle)
2209 {
2210 /*
2211 * setsockopt() barfs unless it get a dummy parameter.
2212 * valgrind whines unless the value is initialized,
2213 * as it has no idea that setsockopt() ignores its
2214 * parameter.
2215 */
2216 int dummy = 0;
2217
2218 return setsockopt(handle->fd, SOL_SOCKET, SO_DETACH_FILTER,
2219 &dummy, sizeof(dummy));
2220 }
2221 #endif
2222