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 #include "diag-control.h"
  37
  38 #ifdef NEED_STRERROR_H
  39 #include "strerror.h"
  40 #endif
  41
  42 #include <errno.h>
  43 #include <stdlib.h>
  44 #include <unistd.h>
  45 #include <string.h>
  46 #include <sys/socket.h>
  47 #include <arpa/inet.h>
  48
  49 #include <time.h>
  50 #include <sys/time.h>
  51 #include <netinet/in.h>
  52 #include <linux/types.h>
  53
  54 #include <linux/netlink.h>
  55 #include <linux/netfilter.h>
  56 #include <linux/netfilter/nfnetlink.h>
  57 #include <linux/netfilter/nfnetlink_log.h>
  58 #include <linux/netfilter/nfnetlink_queue.h>
  59
  60 /* NOTE: if your program drops privileges after pcap_activate() it WON'T work with nfqueue.
  61  *       It took me quite some time to debug ;/
  62  *
  63  *       Sending any data to nfnetlink socket requires CAP_NET_ADMIN privileges,
  64  *       and in nfqueue we need to send verdict reply after receiving packet.
  65  *
  66  *       In tcpdump you can disable dropping privileges with -Z root
  67  */
  68
  69 #include "pcap-netfilter-linux.h"
  70
  71 #define HDR_LENGTH (NLMSG_LENGTH(NLMSG_ALIGN(sizeof(struct nfgenmsg))))
  72
  73 #define NFLOG_IFACE "nflog"
  74 #define NFQUEUE_IFACE "nfqueue"
  75
  76 typedef enum { OTHER = -1, NFLOG, NFQUEUE } nftype_t;
  77
  78 /*
  79  * Private data for capturing on Linux netfilter sockets.
  80  */
  81 struct pcap_netfilter {
  82         u_int   packets_read;   /* count of packets read with recvfrom() */
  83         u_int   packets_nobufs; /* ENOBUFS counter */
  84 };
  85
  86 static int nfqueue_send_verdict(const pcap_t *handle, uint16_t group_id, u_int32_t id, u_int32_t verdict);
  87
  88
  89 static int
  90 netfilter_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
  91 {
  92         struct pcap_netfilter *handlep = handle->priv;
  93         register u_char *bp, *ep;
  94         int count = 0;
  95         ssize_t len;
  96
  97         /*
  98          * Has "pcap_breakloop()" been called?
  99          */
 100         if (handle->break_loop) {
 101                 /*
 102                  * Yes - clear the flag that indicates that it
 103                  * has, and return PCAP_ERROR_BREAK to indicate
 104                  * that we were told to break out of the loop.
 105                  */
 106                 handle->break_loop = 0;
 107                 return PCAP_ERROR_BREAK;
 108         }
 109         len = handle->cc;
 110         if (len == 0) {
 111                 /*
 112                  * The buffer is empty; refill it.
 113                  *
 114                  * We ignore EINTR, as that might just be due to a signal
 115                  * being delivered - if the signal should interrupt the
 116                  * loop, the signal handler should call pcap_breakloop()
 117                  * to set handle->break_loop (we ignore it on other
 118                  * platforms as well).
 119                  */
 120                 do {
 121                         len = recv(handle->fd, handle->buffer, handle->bufsize, 0);
 122                         if (handle->break_loop) {
 123                                 handle->break_loop = 0;
 124                                 return PCAP_ERROR_BREAK;
 125                         }
 126                         if (len == -1 && errno == ENOBUFS)
 127                                 handlep->packets_nobufs++;
 128                 } while ((len == -1) && (errno == EINTR || errno == ENOBUFS));
 129
 130                 if (len < 0) {
 131                         pcapint_fmt_errmsg_for_errno(handle->errbuf,
 132                             PCAP_ERRBUF_SIZE, errno, "Can't receive packet");
 133                         return PCAP_ERROR;
 134                 }
 135
 136                 bp = (unsigned char *)handle->buffer;
 137         } else
 138                 bp = handle->bp;
 139
 140         /*
 141          * Loop through each message.
 142          *
 143          * This assumes that a single buffer of message will have
 144          * <= INT_MAX packets, so the message count doesn't overflow.
 145          */
 146         ep = bp + len;
 147         while (bp < ep) {
 148                 const struct nlmsghdr *nlh = (const struct nlmsghdr *) bp;
 149                 uint32_t msg_len;
 150                 nftype_t type = OTHER;
 151                 /*
 152                  * Has "pcap_breakloop()" been called?
 153                  * If so, return immediately - if we haven't read any
 154                  * packets, clear the flag and return PCAP_ERROR_BREAK
 155                  * to indicate that we were told to break out of the loop,
 156                  * otherwise leave the flag set, so that the *next* call
 157                  * will break out of the loop without having read any
 158                  * packets, and return the number of packets we've
 159                  * processed so far.
 160                  */
 161                 if (handle->break_loop) {
 162                         handle->bp = bp;
 163                         handle->cc = (int)(ep - bp);
 164                         if (count == 0) {
 165                                 handle->break_loop = 0;
 166                                 return PCAP_ERROR_BREAK;
 167                         } else
 168                                 return count;
 169                 }
 170                 /*
 171                  * NLMSG_SPACE(0) might be signed or might be unsigned,
 172                  * depending on whether the kernel defines NLMSG_ALIGNTO
 173                  * as 4, which older kernels do, or as 4U, which newer
 174                  * kernels do.
 175                  *
 176                  * ep - bp is of type ptrdiff_t, which is signed.
 177                  *
 178                  * To squelch warnings, we cast both to size_t, which
 179                  * is unsigned; ep >= bp, so the cast is safe.
 180                  */
 181                 if ((size_t)(ep - bp) < (size_t)NLMSG_SPACE(0)) {
 182                         /*
 183                          * There's less than one netlink message left
 184                          * in the buffer.  Give up.
 185                          */
 186                         break;
 187                 }
 188
 189                 if (nlh->nlmsg_len < sizeof(struct nlmsghdr) || (u_int)len < nlh->nlmsg_len) {
 190                         snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Message truncated: (got: %zd) (nlmsg_len: %u)", len, nlh->nlmsg_len);
 191                         return -1;
 192                 }
 193
 194                 if (NFNL_SUBSYS_ID(nlh->nlmsg_type) == NFNL_SUBSYS_ULOG &&
 195                     NFNL_MSG_TYPE(nlh->nlmsg_type) == NFULNL_MSG_PACKET)
 196                         type = NFLOG;
 197                 else if (NFNL_SUBSYS_ID(nlh->nlmsg_type) == NFNL_SUBSYS_QUEUE &&
 198                          NFNL_MSG_TYPE(nlh->nlmsg_type) == NFQNL_MSG_PACKET)
 199                         type = NFQUEUE;
 200
 201                 if (type != OTHER) {
 202                         const unsigned char *payload = NULL;
 203                         struct pcap_pkthdr pkth;
 204
 205                         const struct nfgenmsg *nfg = NULL;
 206                         int id = 0;
 207
 208                         if (handle->linktype != DLT_NFLOG) {
 209                                 const struct nfattr *payload_attr = NULL;
 210
 211                                 if (nlh->nlmsg_len < HDR_LENGTH) {
 212                                         snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Malformed message: (nlmsg_len: %u)", nlh->nlmsg_len);
 213                                         return -1;
 214                                 }
 215
 216                                 nfg = NLMSG_DATA(nlh);
 217                                 if (nlh->nlmsg_len > HDR_LENGTH) {
 218                                         struct nfattr *attr = NFM_NFA(nfg);
 219                                         int attr_len = nlh->nlmsg_len - NLMSG_ALIGN(HDR_LENGTH);
 220
 221                                         while (NFA_OK(attr, attr_len)) {
 222                                                 if (type == NFQUEUE) {
 223                                                         switch (NFA_TYPE(attr)) {
 224                                                                 case NFQA_PACKET_HDR:
 225                                                                         {
 226                                                                                 const struct nfqnl_msg_packet_hdr *pkt_hdr = (const struct nfqnl_msg_packet_hdr *) NFA_DATA(attr);
 227
 228                                                                                 id = ntohl(pkt_hdr->packet_id);
 229                                                                                 break;
 230                                                                         }
 231                                                                 case NFQA_PAYLOAD:
 232                                                                         payload_attr = attr;
 233                                                                         break;
 234                                                         }
 235
 236                                                 } else if (type == NFLOG) {
 237                                                         switch (NFA_TYPE(attr)) {
 238                                                                 case NFULA_PAYLOAD:
 239                                                                         payload_attr = attr;
 240                                                                         break;
 241                                                         }
 242                                                 }
 243                                                 attr = NFA_NEXT(attr, attr_len);
 244                                         }
 245                                 }
 246
 247                                 if (payload_attr) {
 248                                         payload = NFA_DATA(payload_attr);
 249                                         pkth.len = pkth.caplen = NFA_PAYLOAD(payload_attr);
 250                                 }
 251
 252                         } else {
 253                                 payload = NLMSG_DATA(nlh);
 254                                 pkth.caplen = pkth.len = nlh->nlmsg_len-NLMSG_ALIGN(sizeof(struct nlmsghdr));
 255                         }
 256
 257                         if (payload) {
 258                                 /* pkth.caplen = min (payload_len, handle->snapshot); */
 259
 260                                 gettimeofday(&pkth.ts, NULL);
 261                                 if (handle->fcode.bf_insns == NULL ||
 262                                                 pcapint_filter(handle->fcode.bf_insns, payload, pkth.len, pkth.caplen))
 263                                 {
 264                                         handlep->packets_read++;
 265                                         callback(user, &pkth, payload);
 266                                         count++;
 267                                 }
 268                         }
 269
 270                         if (type == NFQUEUE) {
 271                                 /* XXX, possible responses: NF_DROP, NF_ACCEPT, NF_STOLEN, NF_QUEUE, NF_REPEAT, NF_STOP */
 272                                 /* if type == NFQUEUE, handle->linktype is always != DLT_NFLOG,
 273                                    so nfg is always initialized to NLMSG_DATA(nlh). */
 274                                 if (nfg != NULL)
 275                                         nfqueue_send_verdict(handle, ntohs(nfg->res_id), id, NF_ACCEPT);
 276                         }
 277                 }
 278
 279                 msg_len = NLMSG_ALIGN(nlh->nlmsg_len);
 280                 /*
 281                  * If the message length would run past the end of the
 282                  * buffer, truncate it to the remaining space in the
 283                  * buffer.
 284                  *
 285                  * To squelch warnings, we cast ep - bp to uint32_t, which
 286                  * is unsigned and is the type of msg_len; ep >= bp, and
 287                  * len should fit in 32 bits (either it's set from an int
 288                  * or it's set from a recv() call with a buffer size that's
 289                  * an int, and we're assuming either ILP32 or LP64), so
 290                  * the cast is safe.
 291                  */
 292                 if (msg_len > (uint32_t)(ep - bp))
 293                         msg_len = (uint32_t)(ep - bp);
 294
 295                 bp += msg_len;
 296                 if (count >= max_packets && !PACKET_COUNT_IS_UNLIMITED(max_packets)) {
 297                         handle->bp = bp;
 298                         handle->cc = (int)(ep - bp);
 299                         if (handle->cc < 0)
 300                                 handle->cc = 0;
 301                         return count;
 302                 }
 303         }
 304
 305         handle->cc = 0;
 306         return count;
 307 }
 308
 309 static int
 310 netfilter_set_datalink(pcap_t *handle, int dlt)
 311 {
 312         handle->linktype = dlt;
 313         return 0;
 314 }
 315
 316 static int
 317 netfilter_stats_linux(pcap_t *handle, struct pcap_stat *stats)
 318 {
 319         struct pcap_netfilter *handlep = handle->priv;
 320
 321         stats->ps_recv = handlep->packets_read;
 322         stats->ps_drop = handlep->packets_nobufs;
 323         stats->ps_ifdrop = 0;
 324         return 0;
 325 }
 326
 327 static int
 328 netfilter_inject_linux(pcap_t *handle, const void *buf _U_, int size _U_)
 329 {
 330         snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
 331             "Packet injection is not supported on netfilter devices");
 332         return (-1);
 333 }
 334
 335 struct my_nfattr {
 336         uint16_t nfa_len;
 337         uint16_t nfa_type;
 338         void *data;
 339 };
 340
 341 static int
 342 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)
 343 {
 344         char buf[1024] __attribute__ ((aligned));
 345         memset(buf, 0, sizeof(buf));
 346
 347         struct nlmsghdr *nlh = (struct nlmsghdr *) buf;
 348         struct nfgenmsg *nfg = (struct nfgenmsg *) (buf + sizeof(struct nlmsghdr));
 349
 350         struct sockaddr_nl snl;
 351         static unsigned int seq_id;
 352
 353         if (!seq_id)
 354 DIAG_OFF_NARROWING
 355                 seq_id = time(NULL);
 356 DIAG_ON_NARROWING
 357         ++seq_id;
 358
 359         nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct nfgenmsg));
 360         nlh->nlmsg_type = msg_type;
 361         nlh->nlmsg_flags = NLM_F_REQUEST | (ack ? NLM_F_ACK : 0);
 362         nlh->nlmsg_pid = 0;     /* to kernel */
 363         nlh->nlmsg_seq = seq_id;
 364
 365         nfg->nfgen_family = family;
 366         nfg->version = NFNETLINK_V0;
 367         nfg->res_id = htons(res_id);
 368
 369         if (mynfa) {
 370                 struct nfattr *nfa = (struct nfattr *) (buf + NLMSG_ALIGN(nlh->nlmsg_len));
 371
 372                 nfa->nfa_type = mynfa->nfa_type;
 373                 nfa->nfa_len = NFA_LENGTH(mynfa->nfa_len);
 374                 memcpy(NFA_DATA(nfa), mynfa->data, mynfa->nfa_len);
 375                 nlh->nlmsg_len = NLMSG_ALIGN(nlh->nlmsg_len) + NFA_ALIGN(nfa->nfa_len);
 376         }
 377
 378         memset(&snl, 0, sizeof(snl));
 379         snl.nl_family = AF_NETLINK;
 380
 381         if (sendto(handle->fd, nlh, nlh->nlmsg_len, 0, (struct sockaddr *) &snl, sizeof(snl)) == -1)
 382                 return -1;
 383
 384         if (!ack)
 385                 return 0;
 386
 387         /* waiting for reply loop */
 388         do {
 389                 socklen_t addrlen = sizeof(snl);
 390                 int len;
 391
 392                 /* ignore interrupt system call error */
 393                 do {
 394                         /*
 395                          * The buffer is not so big that its size won't
 396                          * fit into an int.
 397                          */
 398                         len = (int)recvfrom(handle->fd, buf, sizeof(buf), 0, (struct sockaddr *) &snl, &addrlen);
 399                 } while ((len == -1) && (errno == EINTR));
 400
 401                 if (len <= 0)
 402                         return len;
 403
 404                 if (addrlen != sizeof(snl) || snl.nl_family != AF_NETLINK) {
 405                         errno = EINVAL;
 406                         return -1;
 407                 }
 408
 409                 nlh = (struct nlmsghdr *) buf;
 410                 if (snl.nl_pid != 0 || seq_id != nlh->nlmsg_seq)        /* if not from kernel or wrong sequence skip */
 411                         continue;
 412
 413                 while ((u_int)len >= NLMSG_SPACE(0) && NLMSG_OK(nlh, (u_int)len)) {
 414                         if (nlh->nlmsg_type == NLMSG_ERROR || (nlh->nlmsg_type == NLMSG_DONE && nlh->nlmsg_flags & NLM_F_MULTI)) {
 415                                 if (nlh->nlmsg_len < NLMSG_ALIGN(sizeof(struct nlmsgerr))) {
 416                                         errno = EBADMSG;
 417                                         return -1;
 418                                 }
 419                                 errno = -(*((int *)NLMSG_DATA(nlh)));
 420                                 return (errno == 0) ? 0 : -1;
 421                         }
 422                         nlh = NLMSG_NEXT(nlh, len);
 423                 }
 424         } while (1);
 425
 426         return -1; /* never here */
 427 }
 428
 429 static int
 430 nflog_send_config_msg(const pcap_t *handle, uint8_t family, u_int16_t group_id, const struct my_nfattr *mynfa)
 431 {
 432         return netfilter_send_config_msg(handle, (NFNL_SUBSYS_ULOG << 8) | NFULNL_MSG_CONFIG, 1, family, group_id, mynfa);
 433 }
 434
 435 static int
 436 nflog_send_config_cmd(const pcap_t *handle, uint16_t group_id, u_int8_t cmd, u_int8_t family)
 437 {
 438         struct nfulnl_msg_config_cmd msg;
 439         struct my_nfattr nfa;
 440
 441         msg.command = cmd;
 442
 443         nfa.data = &msg;
 444         nfa.nfa_type = NFULA_CFG_CMD;
 445         nfa.nfa_len = sizeof(msg);
 446
 447         return nflog_send_config_msg(handle, family, group_id, &nfa);
 448 }
 449
 450 static int
 451 nflog_send_config_mode(const pcap_t *handle, uint16_t group_id, u_int8_t copy_mode, u_int32_t copy_range)
 452 {
 453         struct nfulnl_msg_config_mode msg;
 454         struct my_nfattr nfa;
 455
 456         msg.copy_range = htonl(copy_range);
 457         msg.copy_mode = copy_mode;
 458
 459         nfa.data = &msg;
 460         nfa.nfa_type = NFULA_CFG_MODE;
 461         nfa.nfa_len = sizeof(msg);
 462
 463         return nflog_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
 464 }
 465
 466 static int
 467 nfqueue_send_verdict(const pcap_t *handle, uint16_t group_id, u_int32_t id, u_int32_t verdict)
 468 {
 469         struct nfqnl_msg_verdict_hdr msg;
 470         struct my_nfattr nfa;
 471
 472         msg.id = htonl(id);
 473         msg.verdict = htonl(verdict);
 474
 475         nfa.data = &msg;
 476         nfa.nfa_type = NFQA_VERDICT_HDR;
 477         nfa.nfa_len = sizeof(msg);
 478
 479         return netfilter_send_config_msg(handle, (NFNL_SUBSYS_QUEUE << 8) | NFQNL_MSG_VERDICT, 0, AF_UNSPEC, group_id, &nfa);
 480 }
 481
 482 static int
 483 nfqueue_send_config_msg(const pcap_t *handle, uint8_t family, u_int16_t group_id, const struct my_nfattr *mynfa)
 484 {
 485         return netfilter_send_config_msg(handle, (NFNL_SUBSYS_QUEUE << 8) | NFQNL_MSG_CONFIG, 1, family, group_id, mynfa);
 486 }
 487
 488 static int
 489 nfqueue_send_config_cmd(const pcap_t *handle, uint16_t group_id, u_int8_t cmd, u_int16_t pf)
 490 {
 491         struct nfqnl_msg_config_cmd msg;
 492         struct my_nfattr nfa;
 493
 494         msg.command = cmd;
 495         msg.pf = htons(pf);
 496
 497         nfa.data = &msg;
 498         nfa.nfa_type = NFQA_CFG_CMD;
 499         nfa.nfa_len = sizeof(msg);
 500
 501         return nfqueue_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
 502 }
 503
 504 static int
 505 nfqueue_send_config_mode(const pcap_t *handle, uint16_t group_id, u_int8_t copy_mode, u_int32_t copy_range)
 506 {
 507         struct nfqnl_msg_config_params msg;
 508         struct my_nfattr nfa;
 509
 510         msg.copy_range = htonl(copy_range);
 511         msg.copy_mode = copy_mode;
 512
 513         nfa.data = &msg;
 514         nfa.nfa_type = NFQA_CFG_PARAMS;
 515         nfa.nfa_len = sizeof(msg);
 516
 517         return nfqueue_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
 518 }
 519
 520 static int
 521 netfilter_activate(pcap_t* handle)
 522 {
 523         const char *dev = handle->opt.device;
 524         unsigned short groups[32];
 525         int group_count = 0;
 526         nftype_t type = OTHER;
 527         int i;
 528
 529         if (strncmp(dev, NFLOG_IFACE, strlen(NFLOG_IFACE)) == 0) {
 530                 dev += strlen(NFLOG_IFACE);
 531                 type = NFLOG;
 532
 533         } else if (strncmp(dev, NFQUEUE_IFACE, strlen(NFQUEUE_IFACE)) == 0) {
 534                 dev += strlen(NFQUEUE_IFACE);
 535                 type = NFQUEUE;
 536         }
 537
 538         if (type != OTHER && *dev == ':') {
 539                 dev++;
 540                 while (*dev) {
 541                         long int group_id;
 542                         char *end_dev;
 543
 544                         if (group_count == 32) {
 545                                 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
 546                                                 "Maximum 32 netfilter groups! dev: %s",
 547                                                 handle->opt.device);
 548                                 return PCAP_ERROR;
 549                         }
 550
 551                         group_id = strtol(dev, &end_dev, 0);
 552                         if (end_dev != dev) {
 553                                 if (group_id < 0 || group_id > 65535) {
 554                                         snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
 555                                                         "Netfilter group range from 0 to 65535 (got %ld)",
 556                                                         group_id);
 557                                         return PCAP_ERROR;
 558                                 }
 559
 560                                 groups[group_count++] = (unsigned short) group_id;
 561                                 dev = end_dev;
 562                         }
 563                         if (*dev != ',')
 564                                 break;
 565                         dev++;
 566                 }
 567         }
 568
 569         if (type == OTHER || *dev) {
 570                 snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
 571                                 "Can't get netfilter group(s) index from %s",
 572                                 handle->opt.device);
 573                 return PCAP_ERROR;
 574         }
 575
 576         /* if no groups, add default: 0 */
 577         if (!group_count) {
 578                 groups[0] = 0;
 579                 group_count = 1;
 580         }
 581
 582         /*
 583          * Turn a negative snapshot value (invalid), a snapshot value of
 584          * 0 (unspecified), or a value bigger than the normal maximum
 585          * value, into the maximum allowed value.
 586          *
 587          * If some application really *needs* a bigger snapshot
 588          * length, we should just increase MAXIMUM_SNAPLEN.
 589          */
 590         if (handle->snapshot <= 0 || handle->snapshot > MAXIMUM_SNAPLEN)
 591                 handle->snapshot = MAXIMUM_SNAPLEN;
 592
 593         /* Initialize some components of the pcap structure. */
 594         handle->bufsize = 128 + handle->snapshot;
 595         handle->offset = 0;
 596         handle->read_op = netfilter_read_linux;
 597         handle->inject_op = netfilter_inject_linux;
 598         handle->setfilter_op = pcapint_install_bpf_program; /* no kernel filtering */
 599         handle->setdirection_op = NULL;
 600         handle->set_datalink_op = netfilter_set_datalink;
 601         handle->getnonblock_op = pcapint_getnonblock_fd;
 602         handle->setnonblock_op = pcapint_setnonblock_fd;
 603         handle->stats_op = netfilter_stats_linux;
 604
 605         /* Create netlink socket */
 606         handle->fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER);
 607         if (handle->fd < 0) {
 608                 pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
 609                     errno, "Can't create raw socket");
 610                 return PCAP_ERROR;
 611         }
 612
 613         if (type == NFLOG) {
 614                 handle->linktype = DLT_NFLOG;
 615                 handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
 616                 if (handle->dlt_list == NULL) {
 617                         pcapint_fmt_errmsg_for_errno(handle->errbuf,
 618                             PCAP_ERRBUF_SIZE, errno,
 619                             "Can't allocate DLT list");
 620                         goto close_fail;
 621                 }
 622                 handle->dlt_list[0] = DLT_NFLOG;
 623                 handle->dlt_list[1] = DLT_IPV4;
 624                 handle->dlt_count = 2;
 625         } else
 626                 handle->linktype = DLT_IPV4;
 627
 628         handle->buffer = malloc(handle->bufsize);
 629         if (!handle->buffer) {
 630                 pcapint_fmt_errmsg_for_errno(handle->errbuf, PCAP_ERRBUF_SIZE,
 631                     errno, "Can't allocate dump buffer");
 632                 goto close_fail;
 633         }
 634
 635         if (type == NFLOG) {
 636                 if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_UNBIND, AF_INET) < 0) {
 637                         pcapint_fmt_errmsg_for_errno(handle->errbuf,
 638                             PCAP_ERRBUF_SIZE, errno,
 639                             "NFULNL_CFG_CMD_PF_UNBIND");
 640                         goto close_fail;
 641                 }
 642
 643                 if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_BIND, AF_INET) < 0) {
 644                         pcapint_fmt_errmsg_for_errno(handle->errbuf,
 645                             PCAP_ERRBUF_SIZE, errno, "NFULNL_CFG_CMD_PF_BIND");
 646                         goto close_fail;
 647                 }
 648
 649                 /* Bind socket to the nflog groups */
 650                 for (i = 0; i < group_count; i++) {
 651                         if (nflog_send_config_cmd(handle, groups[i], NFULNL_CFG_CMD_BIND, AF_UNSPEC) < 0) {
 652                                 pcapint_fmt_errmsg_for_errno(handle->errbuf,
 653                                     PCAP_ERRBUF_SIZE, errno,
 654                                     "Can't listen on group index");
 655                                 goto close_fail;
 656                         }
 657
 658                         if (nflog_send_config_mode(handle, groups[i], NFULNL_COPY_PACKET, handle->snapshot) < 0) {
 659                                 pcapint_fmt_errmsg_for_errno(handle->errbuf,
 660                                     PCAP_ERRBUF_SIZE, errno,
 661                                     "NFULNL_COPY_PACKET");
 662                                 goto close_fail;
 663                         }
 664                 }
 665
 666         } else {
 667                 if (nfqueue_send_config_cmd(handle, 0, NFQNL_CFG_CMD_PF_UNBIND, AF_INET) < 0) {
 668                         pcapint_fmt_errmsg_for_errno(handle->errbuf,
 669                             PCAP_ERRBUF_SIZE, errno, "NFQNL_CFG_CMD_PF_UNBIND");
 670                         goto close_fail;
 671                 }
 672
 673                 if (nfqueue_send_config_cmd(handle, 0, NFQNL_CFG_CMD_PF_BIND, AF_INET) < 0) {
 674                         pcapint_fmt_errmsg_for_errno(handle->errbuf,
 675                             PCAP_ERRBUF_SIZE, errno, "NFQNL_CFG_CMD_PF_BIND");
 676                         goto close_fail;
 677                 }
 678
 679                 /* Bind socket to the nfqueue groups */
 680                 for (i = 0; i < group_count; i++) {
 681                         if (nfqueue_send_config_cmd(handle, groups[i], NFQNL_CFG_CMD_BIND, AF_UNSPEC) < 0) {
 682                                 pcapint_fmt_errmsg_for_errno(handle->errbuf,
 683                                     PCAP_ERRBUF_SIZE, errno,
 684                                     "Can't listen on group index");
 685                                 goto close_fail;
 686                         }
 687
 688                         if (nfqueue_send_config_mode(handle, groups[i], NFQNL_COPY_PACKET, handle->snapshot) < 0) {
 689                                 pcapint_fmt_errmsg_for_errno(handle->errbuf,
 690                                     PCAP_ERRBUF_SIZE, errno,
 691                                     "NFQNL_COPY_PACKET");
 692                                 goto close_fail;
 693                         }
 694                 }
 695         }
 696
 697         if (handle->opt.rfmon) {
 698                 /*
 699                  * Monitor mode doesn't apply to netfilter devices.
 700                  */
 701                 pcapint_cleanup_live_common(handle);
 702                 return PCAP_ERROR_RFMON_NOTSUP;
 703         }
 704
 705         if (handle->opt.buffer_size != 0) {
 706                 /*
 707                  * Set the socket buffer size to the specified value.
 708                  */
 709                 if (setsockopt(handle->fd, SOL_SOCKET, SO_RCVBUF, &handle->opt.buffer_size, sizeof(handle->opt.buffer_size)) == -1) {
 710                         pcapint_fmt_errmsg_for_errno(handle->errbuf,
 711                             PCAP_ERRBUF_SIZE, errno, "SO_RCVBUF");
 712                         goto close_fail;
 713                 }
 714         }
 715
 716         handle->selectable_fd = handle->fd;
 717         return 0;
 718
 719 close_fail:
 720         pcapint_cleanup_live_common(handle);
 721         return PCAP_ERROR;
 722 }
 723
 724 pcap_t *
 725 netfilter_create(const char *device, char *ebuf, int *is_ours)
 726 {
 727         const char *cp;
 728         pcap_t *p;
 729
 730         /* Does this look like an netfilter device? */
 731         cp = strrchr(device, '/');
 732         if (cp == NULL)
 733                 cp = device;
 734
 735         /* Does it begin with NFLOG_IFACE or NFQUEUE_IFACE? */
 736         if (strncmp(cp, NFLOG_IFACE, sizeof NFLOG_IFACE - 1) == 0)
 737                 cp += sizeof NFLOG_IFACE - 1;
 738         else if (strncmp(cp, NFQUEUE_IFACE, sizeof NFQUEUE_IFACE - 1) == 0)
 739                 cp += sizeof NFQUEUE_IFACE - 1;
 740         else {
 741                 /* Nope, doesn't begin with NFLOG_IFACE nor NFQUEUE_IFACE */
 742                 *is_ours = 0;
 743                 return NULL;
 744         }
 745
 746         /*
 747          * Yes - is that either the end of the name, or is it followed
 748          * by a colon?
 749          */
 750         if (*cp != ':' && *cp != '\0') {
 751                 /* Nope */
 752                 *is_ours = 0;
 753                 return NULL;
 754         }
 755
 756         /* OK, it's probably ours. */
 757         *is_ours = 1;
 758
 759         p = PCAP_CREATE_COMMON(ebuf, struct pcap_netfilter);
 760         if (p == NULL)
 761                 return (NULL);
 762
 763         p->activate_op = netfilter_activate;
 764         return (p);
 765 }
 766
 767 int
 768 netfilter_findalldevs(pcap_if_list_t *devlistp, char *err_str)
 769 {
 770         int sock;
 771
 772         sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER);
 773         if (sock < 0) {
 774                 /* if netlink is not supported this is not fatal */
 775                 if (errno == EAFNOSUPPORT || errno == EPROTONOSUPPORT)
 776                         return 0;
 777                 pcapint_fmt_errmsg_for_errno(err_str, PCAP_ERRBUF_SIZE,
 778                     errno, "Can't open netlink socket");
 779                 return -1;
 780         }
 781         close(sock);
 782
 783         /*
 784          * The notion of "connected" vs. "disconnected" doesn't apply.
 785          * XXX - what about "up" and "running"?
 786          */
 787         if (pcapint_add_dev(devlistp, NFLOG_IFACE,
 788             PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE,
 789             "Linux netfilter log (NFLOG) interface", err_str) == NULL)
 790                 return -1;
 791         if (pcapint_add_dev(devlistp, NFQUEUE_IFACE,
 792             PCAP_IF_CONNECTION_STATUS_NOT_APPLICABLE,
 793             "Linux netfilter queue (NFQUEUE) interface", err_str) == NULL)
 794                 return -1;
 795         return 0;
 796 }