The Tcpdump Group git mirrors - libpcap/blob - pcap-netfilter-linux.c

   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 /*
  78  * Private data for capturing on Linux netfilter sockets.
  79  */
  80 struct pcap_netfilter {
  81         u_int   packets_read;   /* count of packets read with recvfrom() */
  82         u_int   packets_nobufs; /* ENOBUFS counter */
  83 };
  84
  85 static int nfqueue_send_verdict(const pcap_t *handle, uint16_t group_id, u_int32_t id, u_int32_t verdict);
  86
  87
  88 static int
  89 netfilter_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
  90 {
  91         struct pcap_netfilter *handlep = handle->priv;
  92         register u_char *bp, *ep;
  93         int count = 0;
  94         ssize_t len;
  95
  96         /*
  97          * Has "pcap_breakloop()" been called?
  98          */
  99         if (handle->break_loop) {
 100                 /*
 101                  * Yes - clear the flag that indicates that it
 102                  * has, and return PCAP_ERROR_BREAK to indicate
 103                  * that we were told to break out of the loop.
 104                  */
 105                 handle->break_loop = 0;
 106                 return PCAP_ERROR_BREAK;
 107         }
 108         len = handle->cc;
 109         if (len == 0) {
 110                 /*
 111                  * The buffer is empty; refill it.
 112                  *
 113                  * We ignore EINTR, as that might just be due to a signal
 114                  * being delivered - if the signal should interrupt the
 115                  * loop, the signal handler should call pcap_breakloop()
 116                  * to set handle->break_loop (we ignore it on other
 117                  * platforms as well).
 118                  */
 119                 do {
 120                         len = recv(handle->fd, handle->buffer, handle->bufsize, 0);
 121                         if (handle->break_loop) {
 122                                 handle->break_loop = 0;
 123                                 return PCAP_ERROR_BREAK;
 124                         }
 125                         if (errno == ENOBUFS)
 126                                 handlep->packets_nobufs++;
 127                 } while ((len == -1) && (errno == EINTR || errno == ENOBUFS));
 128
 129                 if (len < 0) {
 130                         pcap_fmt_errmsg_for_errno(handle->errbuf,
 131                             PCAP_ERRBUF_SIZE, errno, "Can't receive packet");
 132                         return PCAP_ERROR;
 133                 }
 134
 135                 bp = (unsigned char *)handle->buffer;
 136         } else
 137                 bp = handle->bp;
 138         ep = bp + len;
 139         while (bp < ep) {
 140                 const struct nlmsghdr *nlh = (const struct nlmsghdr *) bp;
 141                 uint32_t msg_len;
 142                 nftype_t type = OTHER;
 143                 /*
 144                  * Has "pcap_breakloop()" been called?
 145                  * If so, return immediately - if we haven't read any
 146                  * packets, clear the flag and return PCAP_ERROR_BREAK
 147                  * to indicate that we were told to break out of the loop,
 148                  * otherwise leave the flag set, so that the *next* call
 149                  * will break out of the loop without having read any
 150                  * packets, and return the number of packets we've
 151                  * processed so far.
 152                  */
 153                 if (handle->break_loop) {
 154                         handle->bp = bp;
 155                         handle->cc = (int)(ep - bp);
 156                         if (count == 0) {
 157                                 handle->break_loop = 0;
 158                                 return PCAP_ERROR_BREAK;
 159                         } else
 160                                 return count;
 161                 }
 162                 /*
 163                  * NLMSG_SPACE(0) might be signed or might be unsigned,
 164                  * depending on whether the kernel defines NLMSG_ALIGNTO
 165                  * as 4, which older kernels do, or as 4U, which newer
 166                  * kernels do.
 167                  *
 168                  * ep - bp is of type ptrdiff_t, which is signed.
 169                  *
 170                  * To squelch warnings, we cast both to size_t, which
 171                  * is unsigned; ep >= bp, so the cast is safe.
 172                  */
 173                 if ((size_t)(ep - bp) < (size_t)NLMSG_SPACE(0)) {
 174                         /*
 175                          * There's less than one netlink message left
 176                          * in the buffer.  Give up.
 177                          */
 178                         break;
 179                 }
 180
 181                 if (nlh->nlmsg_len < sizeof(struct nlmsghdr) || (u_int)len < nlh->nlmsg_len) {
 182                         snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Message truncated: (got: %zd) (nlmsg_len: %u)", len, nlh->nlmsg_len);
 183                         return -1;
 184                 }
 185
 186                 if (NFNL_SUBSYS_ID(nlh->nlmsg_type) == NFNL_SUBSYS_ULOG &&
 187                     NFNL_MSG_TYPE(nlh->nlmsg_type) == NFULNL_MSG_PACKET)
 188                         type = NFLOG;
 189                 else if (NFNL_SUBSYS_ID(nlh->nlmsg_type) == NFNL_SUBSYS_QUEUE &&
 190                          NFNL_MSG_TYPE(nlh->nlmsg_type) == NFQNL_MSG_PACKET)
 191                         type = NFQUEUE;
 192
 193                 if (type != OTHER) {
 194                         const unsigned char *payload = NULL;
 195                         struct pcap_pkthdr pkth;
 196
 197                         const struct nfgenmsg *nfg = NULL;
 198                         int id = 0;
 199
 200                         if (handle->linktype != DLT_NFLOG) {
 201                                 const struct nfattr *payload_attr = NULL;
 202
 203                                 if (nlh->nlmsg_len < HDR_LENGTH) {
 204                                         snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Malformed message: (nlmsg_len: %u)", nlh->nlmsg_len);
 205                                         return -1;
 206                                 }
 207
 208                                 nfg = NLMSG_DATA(nlh);
 209                                 if (nlh->nlmsg_len > HDR_LENGTH) {
 210                                         struct nfattr *attr = NFM_NFA(nfg);
 211                                         int attr_len = nlh->nlmsg_len - NLMSG_ALIGN(HDR_LENGTH);
 212
 213                                         while (NFA_OK(attr, attr_len)) {
 214                                                 if (type == NFQUEUE) {
 215                                                         switch (NFA_TYPE(attr)) {
 216                                                                 case NFQA_PACKET_HDR:
 217                                                                         {
 218                                                                                 const struct nfqnl_msg_packet_hdr *pkt_hdr = (const struct nfqnl_msg_packet_hdr *) NFA_DATA(attr);
 219
 220                                                                                 id = ntohl(pkt_hdr->packet_id);
 221                                                                                 break;
 222                                                                         }
 223                                                                 case NFQA_PAYLOAD:
 224                                                                         payload_attr = attr;
 225                                                                         break;
 226                                                         }
 227
 228                                                 } else if (type == NFLOG) {
 229                                                         switch (NFA_TYPE(attr)) {
 230                                                                 case NFULA_PAYLOAD:
 231                                                                         payload_attr = attr;
 232                                                                         break;
 233                                                         }
 234                                                 }
 235                                                 attr = NFA_NEXT(attr, attr_len);
 236                                         }
 237                                 }
 238
 239                                 if (payload_attr) {
 240                                         payload = NFA_DATA(payload_attr);
 241                                         pkth.len = pkth.caplen = NFA_PAYLOAD(payload_attr);
 242                                 }
 243
 244                         } else {
 245                                 payload = NLMSG_DATA(nlh);
 246                                 pkth.caplen = pkth.len = nlh->nlmsg_len-NLMSG_ALIGN(sizeof(struct nlmsghdr));
 247                         }
 248
 249                         if (payload) {
 250                                 /* pkth.caplen = min (payload_len, handle->snapshot); */
 251
 252                                 gettimeofday(&pkth.ts, NULL);
 253                                 if (handle->fcode.bf_insns == NULL ||
 254                                                 pcap_filter(handle->fcode.bf_insns, payload, pkth.len, pkth.caplen))
 255                                 {
 256                                         handlep->packets_read++;
 257                                         callback(user, &pkth, payload);
 258                                         count++;
 259                                 }
 260                         }
 261
 262                         if (type == NFQUEUE) {
 263                                 /* XXX, possible responses: NF_DROP, NF_ACCEPT, NF_STOLEN, NF_QUEUE, NF_REPEAT, NF_STOP */
 264                                 /* if type == NFQUEUE, handle->linktype is always != DLT_NFLOG,
 265                                    so nfg is always initialized to NLMSG_DATA(nlh). */
 266                                 if (nfg != NULL)
 267                                         nfqueue_send_verdict(handle, ntohs(nfg->res_id), id, NF_ACCEPT);
 268                         }
 269                 }
 270
 271                 msg_len = NLMSG_ALIGN(nlh->nlmsg_len);
 272                 /*
 273                  * If the message length would run past the end of the
 274                  * buffer, truncate it to the remaining space in the
 275                  * buffer.
 276                  *
 277                  * To squelch warnings, we cast ep - bp to uint32_t, which
 278                  * is unsigned and is the type of msg_len; ep >= bp, and
 279                  * len should fit in 32 bits (either it's set from an int
 280                  * or it's set from a recv() call with a buffer size that's
 281                  * an int, and we're assuming either ILP32 or LP64), so
 282                  * the cast is safe.
 283                  */
 284                 if (msg_len > (uint32_t)(ep - bp))
 285                         msg_len = (uint32_t)(ep - bp);
 286
 287                 bp += msg_len;
 288                 if (count >= max_packets && !PACKET_COUNT_IS_UNLIMITED(max_packets)) {
 289                         handle->bp = bp;
 290                         handle->cc = (int)(ep - bp);
 291                         if (handle->cc < 0)
 292                                 handle->cc = 0;
 293                         return count;
 294                 }
 295         }
 296
 297         handle->cc = 0;
 298         return count;
 299 }
 300
 301 static int
 302 netfilter_set_datalink(pcap_t *handle, int dlt)
 303 {
 304         handle->linktype = dlt;
 305         return 0;
 306 }
 307
 308 static int
 309 netfilter_stats_linux(pcap_t *handle, struct pcap_stat *stats)
 310 {
 311         struct pcap_netfilter *handlep = handle->priv;
 312
 313         stats->ps_recv = handlep->packets_read;
 314         stats->ps_drop = handlep->packets_nobufs;
 315         stats->ps_ifdrop = 0;
 316         return 0;
 317 }
 318
 319 static int
 320 netfilter_inject_linux(pcap_t *handle, const void *buf _U_, int size _U_)
 321 {
 322         snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
 323             "Packet injection is not supported on netfilter devices");
 324         return (-1);
 325 }
 326
 327 struct my_nfattr {
 328         uint16_t nfa_len;
 329         uint16_t nfa_type;
 330         void *data;
 331 };
 332
 333 static int
 334 netfilter_send_config_msg(const pcap_t *handle, uint16_t msg_type, int ack, u_int8_t family, u_int16_t res_id, const struct my_nfattr *mynfa)
 335 {
 336         char buf[1024] __attribute__ ((aligned));
 337         memset(buf, 0, sizeof(buf));
 338
 339         struct nlmsghdr *nlh = (struct nlmsghdr *) buf;
 340         struct nfgenmsg *nfg = (struct nfgenmsg *) (buf + sizeof(struct nlmsghdr));
 341
 342         struct sockaddr_nl snl;
 343         static unsigned int seq_id;
 344
 345         if (!seq_id)
 346                 seq_id = time(NULL);
 347         ++seq_id;
 348
 349         nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct nfgenmsg));
 350         nlh->nlmsg_type = msg_type;
 351         nlh->nlmsg_flags = NLM_F_REQUEST | (ack ? NLM_F_ACK : 0);
 352         nlh->nlmsg_pid = 0;     /* to kernel */
 353         nlh->nlmsg_seq = seq_id;
 354
 355         nfg->nfgen_family = family;
 356         nfg->version = NFNETLINK_V0;
 357         nfg->res_id = htons(res_id);
 358
 359         if (mynfa) {
 360                 struct nfattr *nfa = (struct nfattr *) (buf + NLMSG_ALIGN(nlh->nlmsg_len));
 361
 362                 nfa->nfa_type = mynfa->nfa_type;
 363                 nfa->nfa_len = NFA_LENGTH(mynfa->nfa_len);
 364                 memcpy(NFA_DATA(nfa), mynfa->data, mynfa->nfa_len);
 365                 nlh->nlmsg_len = NLMSG_ALIGN(nlh->nlmsg_len) + NFA_ALIGN(nfa->nfa_len);
 366         }
 367
 368         memset(&snl, 0, sizeof(snl));
 369         snl.nl_family = AF_NETLINK;
 370
 371         if (sendto(handle->fd, nlh, nlh->nlmsg_len, 0, (struct sockaddr *) &snl, sizeof(snl)) == -1)
 372                 return -1;
 373
 374         if (!ack)
 375                 return 0;
 376
 377         /* waiting for reply loop */
 378         do {
 379                 socklen_t addrlen = sizeof(snl);
 380                 int len;
 381
 382                 /* ignore interrupt system call error */
 383                 do {
 384                         /*
 385                          * The buffer is not so big that its size won't
 386                          * fit into an int.
 387                          */
 388                         len = (int)recvfrom(handle->fd, buf, sizeof(buf), 0, (struct sockaddr *) &snl, &addrlen);
 389                 } while ((len == -1) && (errno == EINTR));
 390
 391                 if (len <= 0)
 392                         return len;
 393
 394                 if (addrlen != sizeof(snl) || snl.nl_family != AF_NETLINK) {
 395                         errno = EINVAL;
 396                         return -1;
 397                 }
 398
 399                 nlh = (struct nlmsghdr *) buf;
 400                 if (snl.nl_pid != 0 || seq_id != nlh->nlmsg_seq)        /* if not from kernel or wrong sequence skip */
 401                         continue;
 402
 403                 while ((u_int)len >= NLMSG_SPACE(0) && NLMSG_OK(nlh, (u_int)len)) {
 404                         if (nlh->nlmsg_type == NLMSG_ERROR || (nlh->nlmsg_type == NLMSG_DONE && nlh->nlmsg_flags & NLM_F_MULTI)) {
 405                                 if (nlh->nlmsg_len < NLMSG_ALIGN(sizeof(struct nlmsgerr))) {
 406                                         errno = EBADMSG;
 407                                         return -1;
 408                                 }
 409                                 errno = -(*((int *)NLMSG_DATA(nlh)));
 410                                 return (errno == 0) ? 0 : -1;
 411                         }
 412                         nlh = NLMSG_NEXT(nlh, len);
 413                 }
 414         } while (1);
 415
 416         return -1; /* never here */
 417 }
 418
 419 static int
 420 nflog_send_config_msg(const pcap_t *handle, uint8_t family, u_int16_t group_id, const struct my_nfattr *mynfa)
 421 {
 422         return netfilter_send_config_msg(handle, (NFNL_SUBSYS_ULOG << 8) | NFULNL_MSG_CONFIG, 1, family, group_id, mynfa);
 423 }
 424
 425 static int
 426 nflog_send_config_cmd(const pcap_t *handle, uint16_t group_id, u_int8_t cmd, u_int8_t family)
 427 {
 428         struct nfulnl_msg_config_cmd msg;
 429         struct my_nfattr nfa;
 430
 431         msg.command = cmd;
 432
 433         nfa.data = &msg;
 434         nfa.nfa_type = NFULA_CFG_CMD;
 435         nfa.nfa_len = sizeof(msg);
 436
 437         return nflog_send_config_msg(handle, family, group_id, &nfa);
 438 }
 439
 440 static int
 441 nflog_send_config_mode(const pcap_t *handle, uint16_t group_id, u_int8_t copy_mode, u_int32_t copy_range)
 442 {
 443         struct nfulnl_msg_config_mode msg;
 444         struct my_nfattr nfa;
 445
 446         msg.copy_range = htonl(copy_range);
 447         msg.copy_mode = copy_mode;
 448
 449         nfa.data = &msg;
 450         nfa.nfa_type = NFULA_CFG_MODE;
 451         nfa.nfa_len = sizeof(msg);
 452
 453         return nflog_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
 454 }
 455
 456 static int
 457 nfqueue_send_verdict(const pcap_t *handle, uint16_t group_id, u_int32_t id, u_int32_t verdict)
 458 {
 459         struct nfqnl_msg_verdict_hdr msg;
 460         struct my_nfattr nfa;
 461
 462         msg.id = htonl(id);
 463         msg.verdict = htonl(verdict);
 464
 465         nfa.data = &msg;
 466         nfa.nfa_type = NFQA_VERDICT_HDR;
 467         nfa.nfa_len = sizeof(msg);
 468
 469         return netfilter_send_config_msg(handle, (NFNL_SUBSYS_QUEUE << 8) | NFQNL_MSG_VERDICT, 0, AF_UNSPEC, group_id, &nfa);
 470 }
 471
 472 static int
 473 nfqueue_send_config_msg(const pcap_t *handle, uint8_t family, u_int16_t group_id, const struct my_nfattr *mynfa)
 474 {
 475         return netfilter_send_config_msg(handle, (NFNL_SUBSYS_QUEUE << 8) | NFQNL_MSG_CONFIG, 1, family, group_id, mynfa);
 476 }
 477
 478 static int
 479 nfqueue_send_config_cmd(const pcap_t *handle, uint16_t group_id, u_int8_t cmd, u_int16_t pf)
 480 {
 481         struct nfqnl_msg_config_cmd msg;
 482         struct my_nfattr nfa;
 483
 484         msg.command = cmd;
 485         msg.pf = htons(pf);
 486
 487         nfa.data = &msg;
 488         nfa.nfa_type = NFQA_CFG_CMD;
 489         nfa.nfa_len = sizeof(msg);
 490
 491         return nfqueue_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
 492 }
 493
 494 static int
 495 nfqueue_send_config_mode(const pcap_t *handle, uint16_t group_id, u_int8_t copy_mode, u_int32_t copy_range)
 496 {
 497         struct nfqnl_msg_config_params msg;
 498         struct my_nfattr nfa;
 499
 500         msg.copy_range = htonl(copy_range);
 501         msg.copy_mode = copy_mode;
 502
 503         nfa.data = &msg;
 504         nfa.nfa_type = NFQA_CFG_PARAMS;
 505         nfa.nfa_len = sizeof(msg);
 506
 507         return nfqueue_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
 508 }
 509
 510 static int
 511 netfilter_activate(pcap_t* handle)
 512 {
 513         const char *dev = handle->opt.device;
 514         unsigned short groups[32];
 515         int group_count = 0;
 516         nftype_t type = OTHER;
 517         int i;
 518
 519         if (strncmp(dev, NFLOG_IFACE, strlen(NFLOG_IFACE)) == 0) {
 520                 dev += strlen(NFLOG_IFACE);
 521                 type = NFLOG;
 522
 523         } else if (strncmp(dev, NFQUEUE_IFACE, strlen(NFQUEUE_IFACE)) == 0) {
 524                 dev += strlen(NFQUEUE_IFACE);
 525                 type = NFQUEUE;
 526         }
 527
 528         if (type != OTHER && *dev == ':') {
 529                 dev++;
 530                 while (*dev) {
 531                         long int group_id;
 532                         char *end_dev;
 533
 534                         if (group_count == 32) {
 535                                 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
 536                                                 "Maximum 32 netfilter groups! dev: %s",
 537                                                 handle->opt.device);
 538                                 return PCAP_ERROR;
 539                         }
 540
 541                         group_id = strtol(dev, &end_dev, 0);
 542                         if (end_dev != dev) {
 543                                 if (group_id < 0 || group_id > 65535) {
 544                                         snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
 545                                                         "Netfilter group range from 0 to 65535 (got %ld)",
 546                                                         group_id);
 547                                         return PCAP_ERROR;
 548                                 }
 549
 550                                 groups[group_count++] = (unsigned short) group_id;
 551                                 dev = end_dev;
 552                         }
 553                         if (*dev != ',')
 554                                 break;
 555                         dev++;
 556                 }
 557         }
 558
 559         if (type == OTHER || *dev) {
 560                 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
 561                                 "Can't get netfilter group(s) index from %s",
 562                                 handle->opt.device);
 563                 return PCAP_ERROR;
 564         }
 565
 566         /* if no groups, add default: 0 */
 567         if (!group_count) {
 568                 groups[0] = 0;
 569                 group_count = 1;
 570         }
 571
 572         /*
 573          * Turn a negative snapshot value (invalid), a snapshot value of
 574          * 0 (unspecified), or a value bigger than the normal maximum
 575          * value, into the maximum allowed value.
 576          *
 577          * If some application really *needs* a bigger snapshot
 578          * length, we should just increase MAXIMUM_SNAPLEN.
 579          */
 580         if (handle->snapshot <= 0 || handle->snapshot > MAXIMUM_SNAPLEN)
 581                 handle->snapshot = MAXIMUM_SNAPLEN;
 582
 583         /* Initialize some components of the pcap structure. */
 584         handle->bufsize = 128 + handle->snapshot;
 585         handle->offset = 0;
 586         handle->read_op = netfilter_read_linux;
 587         handle->inject_op = netfilter_inject_linux;
 588         handle->setfilter_op = install_bpf_program; /* no kernel filtering */
 589         handle->setdirection_op = NULL;
 590         handle->set_datalink_op = netfilter_set_datalink;
 591         handle->getnonblock_op = pcap_getnonblock_fd;
 592         handle->setnonblock_op = pcap_setnonblock_fd;
 593         handle->stats_op = netfilter_stats_linux;
 594
 595         /* Create netlink socket */
 596         handle->fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER);
 597         if (handle->fd < 0) {
 598                 pcap_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
 599                     errno, "Can't create raw socket");
 600                 return PCAP_ERROR;
 601         }
 602
 603         if (type == NFLOG) {
 604                 handle->linktype = DLT_NFLOG;
 605                 handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
 606                 if (handle->dlt_list != NULL) {
 607                         handle->dlt_list[0] = DLT_NFLOG;
 608                         handle->dlt_list[1] = DLT_IPV4;
 609                         handle->dlt_count = 2;
 610                 }
 611
 612         } else
 613                 handle->linktype = DLT_IPV4;
 614
 615         handle->buffer = malloc(handle->bufsize);
 616         if (!handle->buffer) {
 617                 pcap_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
 618                     errno, "Can't allocate dump buffer");
 619                 goto close_fail;
 620         }
 621
 622         if (type == NFLOG) {
 623                 if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_UNBIND, AF_INET) < 0) {
 624                         pcap_fmt_errmsg_for_errno(handle->errbuf,
 625                             PCAP_ERRBUF_SIZE, errno,
 626                             "NFULNL_CFG_CMD_PF_UNBIND");
 627                         goto close_fail;
 628                 }
 629
 630                 if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_BIND, AF_INET) < 0) {
 631                         pcap_fmt_errmsg_for_errno(handle->errbuf,
 632                             PCAP_ERRBUF_SIZE, errno, "NFULNL_CFG_CMD_PF_BIND");
 633                         goto close_fail;
 634                 }
 635
 636                 /* Bind socket to the nflog groups */
 637                 for (i = 0; i < group_count; i++) {
 638                         if (nflog_send_config_cmd(handle, groups[i], NFULNL_CFG_CMD_BIND, AF_UNSPEC) < 0) {
 639                                 pcap_fmt_errmsg_for_errno(handle->errbuf,
 640                                     PCAP_ERRBUF_SIZE, errno,
 641                                     "Can't listen on group group index");
 642                                 goto close_fail;
 643                         }
 644
 645                         if (nflog_send_config_mode(handle, groups[i], NFULNL_COPY_PACKET, handle->snapshot) < 0) {
 646                                 pcap_fmt_errmsg_for_errno(handle->errbuf,
 647                                     PCAP_ERRBUF_SIZE, errno,
 648                                     "NFULNL_COPY_PACKET");
 649                                 goto close_fail;
 650                         }
 651                 }
 652
 653         } else {
 654                 if (nfqueue_send_config_cmd(handle, 0, NFQNL_CFG_CMD_PF_UNBIND, AF_INET) < 0) {
 655                         pcap_fmt_errmsg_for_errno(handle->errbuf,
 656                             PCAP_ERRBUF_SIZE, errno, "NFQNL_CFG_CMD_PF_UNBIND");
 657                         goto close_fail;
 658                 }
 659
 660                 if (nfqueue_send_config_cmd(handle, 0, NFQNL_CFG_CMD_PF_BIND, AF_INET) < 0) {
 661                         pcap_fmt_errmsg_for_errno(handle->errbuf,
 662                             PCAP_ERRBUF_SIZE, errno, "NFQNL_CFG_CMD_PF_BIND");
 663                         goto close_fail;
 664                 }
 665
 666                 /* Bind socket to the nfqueue groups */
 667                 for (i = 0; i < group_count; i++) {
 668                         if (nfqueue_send_config_cmd(handle, groups[i], NFQNL_CFG_CMD_BIND, AF_UNSPEC) < 0) {
 669                                 pcap_fmt_errmsg_for_errno(handle->errbuf,
 670                                     PCAP_ERRBUF_SIZE, errno,
 671                                     "Can't listen on group group index");
 672                                 goto close_fail;
 673                         }
 674
 675                         if (nfqueue_send_config_mode(handle, groups[i], NFQNL_COPY_PACKET, handle->snapshot) < 0) {
 676                                 pcap_fmt_errmsg_for_errno(handle->errbuf,
 677                                     PCAP_ERRBUF_SIZE, errno,
 678                                     "NFQNL_COPY_PACKET");
 679                                 goto close_fail;
 680                         }
 681                 }
 682         }
 683
 684         if (handle->opt.rfmon) {
 685                 /*
 686                  * Monitor mode doesn't apply to netfilter devices.
 687                  */
 688                 pcap_cleanup_live_common(handle);
 689                 return PCAP_ERROR_RFMON_NOTSUP;
 690         }
 691
 692         if (handle->opt.buffer_size != 0) {
 693                 /*
 694                  * Set the socket buffer size to the specified value.
 695                  */
 696                 if (setsockopt(handle->fd, SOL_SOCKET, SO_RCVBUF, &handle->opt.buffer_size, sizeof(handle->opt.buffer_size)) == -1) {
 697                         pcap_fmt_errmsg_for_errno(handle->errbuf,
 698                             PCAP_ERRBUF_SIZE, errno, "SO_RCVBUF");
 699                         goto close_fail;
 700                 }
 701         }
 702
 703         handle->selectable_fd = handle->fd;
 704         return 0;
 705
 706 close_fail:
 707         pcap_cleanup_live_common(handle);
 708         return PCAP_ERROR;
 709 }
 710
 711 pcap_t *
 712 netfilter_create(const char *device, char *ebuf, int *is_ours)
 713 {
 714         const char *cp;
 715         pcap_t *p;
 716
 717         /* Does this look like an netfilter device? */
 718         cp = strrchr(device, '/');
 719         if (cp == NULL)
 720                 cp = device;
 721
 722         /* Does it begin with NFLOG_IFACE or NFQUEUE_IFACE? */
 723         if (strncmp(cp, NFLOG_IFACE, sizeof NFLOG_IFACE - 1) == 0)
 724                 cp += sizeof NFLOG_IFACE - 1;
 725         else if (strncmp(cp, NFQUEUE_IFACE, sizeof NFQUEUE_IFACE - 1) == 0)
 726                 cp += sizeof NFQUEUE_IFACE - 1;
 727         else {
 728                 /* Nope, doesn't begin with NFLOG_IFACE nor NFQUEUE_IFACE */
 729                 *is_ours = 0;
 730                 return NULL;
 731         }
 732
 733         /*
 734          * Yes - is that either the end of the name, or is it followed
 735          * by a colon?
 736          */
 737         if (*cp != ':' && *cp != '\0') {
 738                 /* Nope */
 739                 *is_ours = 0;
 740                 return NULL;
 741         }
 742
 743         /* OK, it's probably ours. */
 744         *is_ours = 1;
 745
 746         p = pcap_create_common(ebuf, sizeof (struct pcap_netfilter));
 747         if (p == NULL)
 748                 return (NULL);
 749
 750         p->activate_op = netfilter_activate;
 751         return (p);
 752 }
 753
 754 int
 755 netfilter_findalldevs(pcap_if_list_t *devlistp, char *err_str)
 756 {
 757         int sock;
 758
 759         sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER);
 760         if (sock < 0) {
 761                 /* if netlink is not supported this is not fatal */
 762                 if (errno == EAFNOSUPPORT || errno == EPROTONOSUPPORT)
 763                         return 0;
 764                 pcap_fmt_errmsg_for_errno(err_str, PCAP_ERRBUF_SIZE,
 765                     errno, "Can't open netlink socket");
 766                 return -1;
 767         }
 768         close(sock);
 769
 770         /*
 771          * The notion of "connected" vs. "disconnected" doesn't apply.
 772          * XXX - what about "up" and "running"?
 773          */
 774         if (add_dev(devlistp, NFLOG_IFACE,
 775             PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE,
 776             "Linux netfilter log (NFLOG) interface", err_str) == NULL)
 777                 return -1;
 778         if (add_dev(devlistp, NFQUEUE_IFACE,
 779             PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE,
 780             "Linux netfilter queue (NFQUEUE) interface", err_str) == NULL)
 781                 return -1;
 782         return 0;
 783 }