dist/dhcp/common/bpf.c

   1 /* bpf.c
   2
   3    BPF socket interface code, originally contributed by Archie Cobbs. */
   4
   5 /*
   6  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
   7  * Copyright (c) 1996-2003 by Internet Software Consortium
   8  *
   9  * Permission to use, copy, modify, and distribute this software for any
  10  * purpose with or without fee is hereby granted, provided that the above
  11  * copyright notice and this permission notice appear in all copies.
  12  *
  13  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
  14  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  15  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
  16  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  17  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  18  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  19  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  20  *
  21  *   Internet Systems Consortium, Inc.
  22  *   950 Charter Street
  23  *   Redwood City, CA 94063
  24  *   <info@isc.org>
  25  *   http://www.isc.org/
  26  *
  27  * This software was contributed to Internet Systems Consortium
  28  * by Archie Cobbs.
  29  *
  30  * Patches for FDDI support on Digital Unix were written by Bill
  31  * Stapleton, and maintained for a while by Mike Meredith before he
  32  * managed to get me to integrate them.
  33  */
  34
  35 #ifndef lint
  36 static char copyright[] =
  37 "$Id: bpf.c,v 1.10 2005/08/11 17:13:21 drochner Exp $ Copyright (c) 2004 Internet Systems Consortium.  All rights reserved.\n";
  38 #endif /* not lint */
  39
  40 #include "dhcpd.h"
  41 #if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE) \
  42                                 || defined (USE_LPF_RECEIVE)
  43 # if defined (USE_LPF_RECEIVE)
  44 #  include <asm/types.h>
  45 #  include <linux/filter.h>
  46 #  define bpf_insn sock_filter /* Linux: dare to be gratuitously different. */
  47 # else
  48 #  include <sys/ioctl.h>
  49 #  include <sys/uio.h>
  50 #  include <net/bpf.h>
  51 #  if defined (NEED_OSF_PFILT_HACKS)
  52 #   include <net/pfilt.h>
  53 #  endif
  54 # endif
  55
  56 #include <paths.h>
  57 #include <netinet/in_systm.h>
  58 #include "includes/netinet/ip.h"
  59 #include "includes/netinet/udp.h"
  60 #include "includes/netinet/if_ether.h"
  61 #endif
  62
  63 /* Reinitializes the specified interface after an address change.   This
  64    is not required for packet-filter APIs. */
  65
  66 #ifdef USE_BPF_SEND
  67 void if_reinitialize_send (info)
  68         struct interface_info *info;
  69 {
  70 }
  71 #endif
  72
  73 #ifdef USE_BPF_RECEIVE
  74 void if_reinitialize_receive (info)
  75         struct interface_info *info;
  76 {
  77 }
  78 #endif
  79
  80 /* Called by get_interface_list for each interface that's discovered.
  81    Opens a packet filter for each interface and adds it to the select
  82    mask. */
  83
  84 #if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE)
  85 int if_register_bpf (info)
  86         struct interface_info *info;
  87 {
  88         int sock;
  89         u_int bufsize;
  90
  91         /* Open a BPF device */
  92 #ifdef _PATH_BPF
  93         const char *filename = _PATH_BPF;
  94         sock = open (filename, O_RDWR, 0);
  95         if (sock < 0)
  96                 log_fatal ("No bpf devices.%s%s%s",
  97                        "   Please read the README",
  98                        " section for your operating",
  99                        " system.");
 100
 101 #else
 102         char filename[50];
 103         int b;
 104         for (b = 0; 1; b++) {
 105                 /* %Audit% 31 bytes max. %2004.06.17,Safe% */
 106                 sprintf(filename, BPF_FORMAT, b);
 107                 sock = open (filename, O_RDWR, 0);
 108                 if (sock < 0) {
 109                         if (errno == EBUSY) {
 110                                 continue;
 111                         } else {
 112                                 if (!b)
 113                                         log_fatal ("No bpf devices.%s%s%s",
 114                                                "   Please read the README",
 115                                                " section for your operating",
 116                                                " system.");
 117                                 log_fatal ("Can't find free bpf: %m");
 118                         }
 119                 } else {
 120                         break;
 121                 }
 122         }
 123 #endif
 124
 125         /* Set the BPF buffer size to 32k */
 126         bufsize = 32768;
 127         if (ioctl (sock, BIOCSBLEN, &bufsize) < 0)
 128                 log_error ("Can't set bpf buffer to %d: %m", bufsize);
 129
 130         /* Set the BPF device to point at this interface. */
 131         if (ioctl (sock, BIOCSETIF, info -> ifp) < 0)
 132                 log_fatal ("Can't attach interface %s to bpf device %s: %m",
 133                        info -> name, filename);
 134
 135         return sock;
 136 }
 137 #endif /* USE_BPF_SEND || USE_BPF_RECEIVE */
 138
 139 #ifdef USE_BPF_SEND
 140 void if_register_send (info)
 141         struct interface_info *info;
 142 {
 143         /* If we're using the bpf API for sending and receiving,
 144            we don't need to register this interface twice. */
 145 #ifndef USE_BPF_RECEIVE
 146         info -> wfdesc = if_register_bpf (info, interface);
 147 #else
 148         info -> wfdesc = info -> rfdesc;
 149 #endif
 150         if (!quiet_interface_discovery)
 151                 log_info ("Sending on   BPF/%s/%s%s%s",
 152                       info -> name,
 153                       print_hw_addr (info -> hw_address.hbuf [0],
 154                                      info -> hw_address.hlen - 1,
 155                                      &info -> hw_address.hbuf [1]),
 156                       (info -> shared_network ? "/" : ""),
 157                       (info -> shared_network ?
 158                        info -> shared_network -> name : ""));
 159 }
 160
 161 void if_deregister_send (info)
 162         struct interface_info *info;
 163 {
 164         /* If we're using the bpf API for sending and receiving,
 165            we don't need to register this interface twice. */
 166 #ifndef USE_BPF_RECEIVE
 167         close (info -> wfdesc);
 168 #endif
 169         info -> wfdesc = -1;
 170
 171         if (!quiet_interface_discovery)
 172                 log_info ("Disabling output on BPF/%s/%s%s%s",
 173                       info -> name,
 174                       print_hw_addr (info -> hw_address.hbuf [0],
 175                                      info -> hw_address.hlen - 1,
 176                                      &info -> hw_address.hbuf [1]),
 177                       (info -> shared_network ? "/" : ""),
 178                       (info -> shared_network ?
 179                        info -> shared_network -> name : ""));
 180 }
 181 #endif /* USE_BPF_SEND */
 182
 183 #if defined (USE_BPF_RECEIVE) || defined (USE_LPF_RECEIVE)
 184 /* Packet filter program...
 185    XXX Changes to the filter program may require changes to the constant
 186    offsets used in if_register_send to patch the BPF program! XXX */
 187
 188 struct bpf_insn dhcp_bpf_filter [] = {
 189         /* Make sure this is an IP packet... */
 190         BPF_STMT (BPF_LD + BPF_H + BPF_ABS, 12),
 191         BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
 192
 193         /* Make sure it's a UDP packet... */
 194         BPF_STMT (BPF_LD + BPF_B + BPF_ABS, 23),
 195         BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
 196
 197         /* Make sure this isn't a fragment... */
 198         BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
 199         BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
 200
 201         /* Get the IP header length... */
 202         BPF_STMT (BPF_LDX + BPF_B + BPF_MSH, 14),
 203
 204         /* Make sure it's to the right port... */
 205         BPF_STMT (BPF_LD + BPF_H + BPF_IND, 16),
 206         BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1),             /* patch */
 207
 208         /* If we passed all the tests, ask for the whole packet. */
 209         BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
 210
 211         /* Otherwise, drop it. */
 212         BPF_STMT(BPF_RET+BPF_K, 0),
 213 };
 214
 215 #if defined(DEC_FDDI) || defined(NETBSD_FDDI)
 216 struct bpf_insn *bpf_fddi_filter;
 217 #endif
 218
 219 int dhcp_bpf_filter_len = sizeof dhcp_bpf_filter / sizeof (struct bpf_insn);
 220 #if defined (HAVE_TR_SUPPORT)
 221 struct bpf_insn dhcp_bpf_tr_filter [] = {
 222         /* accept all token ring packets due to variable length header */
 223         /* if we want to get clever, insert the program here */
 224
 225         /* If we passed all the tests, ask for the whole packet. */
 226         BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
 227
 228         /* Otherwise, drop it. */
 229         BPF_STMT(BPF_RET+BPF_K, 0),
 230 };
 231
 232 int dhcp_bpf_tr_filter_len = (sizeof dhcp_bpf_tr_filter /
 233                               sizeof (struct bpf_insn));
 234 #endif /* HAVE_TR_SUPPORT */
 235 #endif /* USE_LPF_RECEIVE || USE_BPF_RECEIVE */
 236
 237 #if defined (USE_BPF_RECEIVE)
 238 void if_register_receive (info)
 239         struct interface_info *info;
 240 {
 241         int flag = 1;
 242         struct bpf_version v;
 243         struct bpf_program p;
 244 #ifdef NEED_OSF_PFILT_HACKS
 245         u_int32_t bits;
 246 #endif
 247         u_int32_t len;
 248 #if defined(DEC_FDDI) || defined(NETBSD_FDDI)
 249         int link_layer;
 250 #endif /* DEC_FDDI || NETBSD_FDDI */
 251
 252         /* Open a BPF device and hang it on this interface... */
 253         info -> rfdesc = if_register_bpf (info);
 254
 255         /* Make sure the BPF version is in range... */
 256         if (ioctl (info -> rfdesc, BIOCVERSION, &v) < 0)
 257                 log_fatal ("Can't get BPF version: %m");
 258
 259         if (v.bv_major != BPF_MAJOR_VERSION ||
 260             v.bv_minor < BPF_MINOR_VERSION)
 261                 log_fatal ("BPF version mismatch - recompile DHCP!");
 262
 263         /* Set immediate mode so that reads return as soon as a packet
 264            comes in, rather than waiting for the input buffer to fill with
 265            packets. */
 266         if (ioctl (info -> rfdesc, BIOCIMMEDIATE, &flag) < 0)
 267                 log_fatal ("Can't set immediate mode on bpf device: %m");
 268
 269 #ifdef NEED_OSF_PFILT_HACKS
 270         /* Allow the copyall flag to be set... */
 271         if (ioctl(info -> rfdesc, EIOCALLOWCOPYALL, &flag) < 0)
 272                 log_fatal ("Can't set ALLOWCOPYALL: %m");
 273
 274         /* Clear all the packet filter mode bits first... */
 275         bits = 0;
 276         if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0)
 277                 log_fatal ("Can't clear pfilt bits: %m");
 278
 279         /* Set the ENBATCH, ENCOPYALL, ENBPFHDR bits... */
 280         bits = ENBATCH | ENCOPYALL | ENBPFHDR;
 281         if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0)
 282                 log_fatal ("Can't set ENBATCH|ENCOPYALL|ENBPFHDR: %m");
 283 #endif
 284         /* Get the required BPF buffer length from the kernel. */
 285         if (ioctl (info -> rfdesc, BIOCGBLEN, &len) < 0)
 286                 log_fatal ("Can't get bpf buffer length: %m");
 287         info -> rbuf_max = len;
 288         info -> rbuf = dmalloc (info -> rbuf_max, MDL);
 289         if (!info -> rbuf)
 290                 log_fatal ("Can't allocate %ld bytes for bpf input buffer.",
 291                            (long)(info -> rbuf_max));
 292         info -> rbuf_offset = 0;
 293         info -> rbuf_len = 0;
 294
 295         /* Set up the bpf filter program structure. */
 296         p.bf_len = dhcp_bpf_filter_len;
 297
 298 #if defined(DEC_FDDI) || defined(NETBSD_FDDI)
 299         /* See if this is an FDDI interface, flag it for later. */
 300         if (ioctl(info -> rfdesc, BIOCGDLT, &link_layer) >= 0 &&
 301             link_layer == DLT_FDDI) {
 302                 if (!bpf_fddi_filter) {
 303                         bpf_fddi_filter = dmalloc (sizeof bpf_fddi_filter,
 304                                                     MDL);
 305                         if (!bpf_fddi_filter)
 306                                 log_fatal ("No memory for FDDI filter.");
 307                         memcpy (bpf_fddi_filter,
 308                                 dhcp_bpf_filter, sizeof dhcp_bpf_filter);
 309                         /* Patch the BPF program to account for the difference
 310                            in length between ethernet headers (14), FDDI and
 311                            802.2 headers (16 +8=24, +10).
 312                            XXX changes to filter program may require changes to
 313                            XXX the insn number(s) used below! */
 314                         bpf_fddi_filter[0].k += 10;
 315                         bpf_fddi_filter[2].k += 10;
 316                         bpf_fddi_filter[4].k += 10;
 317                         bpf_fddi_filter[6].k += 10;
 318                         bpf_fddi_filter[7].k += 10;
 319                 }
 320                 p.bf_insns = bpf_fddi_filter;
 321         } else
 322 #endif /* DEC_FDDI || NETBSD_FDDI */
 323         p.bf_insns = dhcp_bpf_filter;
 324
 325         /* Patch the server port into the BPF  program...
 326            XXX changes to filter program may require changes
 327            to the insn number(s) used below! XXX */
 328         dhcp_bpf_filter [8].k = ntohs (local_port);
 329
 330         if (ioctl (info -> rfdesc, BIOCSETF, &p) < 0)
 331                 log_fatal ("Can't install packet filter program: %m");
 332         if (!quiet_interface_discovery)
 333                 log_info ("Listening on BPF/%s/%s%s%s",
 334                       info -> name,
 335                       print_hw_addr (info -> hw_address.hbuf [0],
 336                                      info -> hw_address.hlen - 1,
 337                                      &info -> hw_address.hbuf [1]),
 338                       (info -> shared_network ? "/" : ""),
 339                       (info -> shared_network ?
 340                        info -> shared_network -> name : ""));
 341 }
 342
 343 void if_deregister_receive (info)
 344         struct interface_info *info;
 345 {
 346         close (info -> rfdesc);
 347         info -> rfdesc = -1;
 348
 349         if (!quiet_interface_discovery)
 350                 log_info ("Disabling input on BPF/%s/%s%s%s",
 351                       info -> name,
 352                       print_hw_addr (info -> hw_address.hbuf [0],
 353                                      info -> hw_address.hlen - 1,
 354                                      &info -> hw_address.hbuf [1]),
 355                       (info -> shared_network ? "/" : ""),
 356                       (info -> shared_network ?
 357                        info -> shared_network -> name : ""));
 358 }
 359 #endif /* USE_BPF_RECEIVE */
 360
 361 #ifdef USE_BPF_SEND
 362 ssize_t send_packet (interface, packet, raw, len, from, to, hto)
 363         struct interface_info *interface;
 364         struct packet *packet;
 365         struct dhcp_packet *raw;
 366         size_t len;
 367         struct in_addr from;
 368         struct sockaddr_in *to;
 369         struct hardware *hto;
 370 {
 371         unsigned hbufp = 0, ibufp = 0;
 372         double hw [4];
 373         double ip [32];
 374         struct iovec iov [3];
 375         int result;
 376
 377         if (!strcmp (interface -> name, "fallback"))
 378                 return send_fallback (interface, packet, raw,
 379                                       len, from, to, hto);
 380
 381         /* Assemble the headers... */
 382         assemble_hw_header (interface, (unsigned char *)hw, &hbufp, hto);
 383         assemble_udp_ip_header (interface,
 384                                 (unsigned char *)ip, &ibufp, from.s_addr,
 385                                 to -> sin_addr.s_addr, to -> sin_port,
 386                                 (unsigned char *)raw, len);
 387
 388         /* Fire it off */
 389         iov [0].iov_base = ((char *)hw);
 390         iov [0].iov_len = hbufp;
 391         iov [1].iov_base = ((char *)ip);
 392         iov [1].iov_len = ibufp;
 393         iov [2].iov_base = (char *)raw;
 394         iov [2].iov_len = len;
 395
 396         result = writev(interface -> wfdesc, iov, 3);
 397         if (result < 0)
 398                 log_error ("send_packet: %m");
 399         return result;
 400 }
 401 #endif /* USE_BPF_SEND */
 402
 403 #ifdef USE_BPF_RECEIVE
 404 ssize_t receive_packet (interface, buf, len, from, hfrom)
 405         struct interface_info *interface;
 406         unsigned char *buf;
 407         size_t len;
 408         struct sockaddr_in *from;
 409         struct hardware *hfrom;
 410 {
 411         int length = 0;
 412         int offset = 0;
 413         struct bpf_hdr hdr;
 414         unsigned paylen;
 415
 416         /* All this complexity is because BPF doesn't guarantee
 417            that only one packet will be returned at a time.   We're
 418            getting what we deserve, though - this is a terrible abuse
 419            of the BPF interface.   Sigh. */
 420
 421         /* Process packets until we get one we can return or until we've
 422            done a read and gotten nothing we can return... */
 423
 424         do {
 425                 /* If the buffer is empty, fill it. */
 426                 if (interface -> rbuf_offset == interface -> rbuf_len) {
 427                         length = read (interface -> rfdesc,
 428                                        interface -> rbuf,
 429                                        (size_t)interface -> rbuf_max);
 430                         if (length <= 0) {
 431 #ifdef __FreeBSD__
 432                                 if (errno == ENXIO) {
 433 #else
 434                                 if (errno == EIO) {
 435 #endif
 436                                         dhcp_interface_remove
 437                                                 ((omapi_object_t *)interface,
 438                                                  (omapi_object_t *)0);
 439                                 }
 440                                 return length;
 441                         }
 442                         interface -> rbuf_offset = 0;
 443                         interface -> rbuf_len = BPF_WORDALIGN (length);
 444                 }
 445
 446                 /* If there isn't room for a whole bpf header, something went
 447                    wrong, but we'll ignore it and hope it goes away... XXX */
 448                 if (interface -> rbuf_len -
 449                     interface -> rbuf_offset < sizeof hdr) {
 450                         interface -> rbuf_offset = interface -> rbuf_len;
 451                         continue;
 452                 }
 453
 454                 /* Adjust for any padding BPF inserted between the packets. */
 455                 interface -> rbuf_offset =
 456                     BPF_WORDALIGN (interface -> rbuf_offset);
 457
 458                 /* Copy out a bpf header... */
 459                 memcpy (&hdr, &interface -> rbuf [interface -> rbuf_offset],
 460                         sizeof hdr);
 461
 462                 /* If the bpf header plus data doesn't fit in what's left
 463                    of the buffer, stick head in sand yet again... */
 464                 if (interface -> rbuf_offset +
 465                     hdr.bh_hdrlen + hdr.bh_caplen > interface -> rbuf_len) {
 466                         interface -> rbuf_offset = interface -> rbuf_len;
 467                         continue;
 468                 }
 469
 470                 /* If the captured data wasn't the whole packet, or if
 471                    the packet won't fit in the input buffer, all we
 472                    can do is drop it. */
 473                 if (hdr.bh_caplen != hdr.bh_datalen) {
 474                         interface -> rbuf_offset =
 475                                 BPF_WORDALIGN (interface -> rbuf_offset +
 476                                                hdr.bh_hdrlen + hdr.bh_caplen);
 477                         continue;
 478                 }
 479
 480                 /* Skip over the BPF header... */
 481                 interface -> rbuf_offset += hdr.bh_hdrlen;
 482
 483                 /* Decode the physical header... */
 484                 offset = decode_hw_header (interface,
 485                                            interface -> rbuf,
 486                                            interface -> rbuf_offset,
 487                                            hfrom);
 488
 489                 /* If a physical layer checksum failed (dunno of any
 490                    physical layer that supports this, but WTH), skip this
 491                    packet. */
 492                 if (offset < 0) {
 493                         interface -> rbuf_offset =
 494                                 BPF_WORDALIGN (interface -> rbuf_offset +
 495                                                hdr.bh_caplen);
 496                         continue;
 497                 }
 498                 interface -> rbuf_offset += offset;
 499                 hdr.bh_caplen -= offset;
 500
 501                 /* Decode the IP and UDP headers... */
 502                 offset = decode_udp_ip_header (interface,
 503                                                interface -> rbuf,
 504                                                interface -> rbuf_offset,
 505                                                from,
 506                                                hdr.bh_caplen, &paylen);
 507
 508                 /* If the IP or UDP checksum was bad, skip the packet... */
 509                 if (offset < 0) {
 510                         interface -> rbuf_offset =
 511                                 BPF_WORDALIGN (interface -> rbuf_offset +
 512                                                hdr.bh_caplen);
 513                         continue;
 514                 }
 515                 interface -> rbuf_offset = interface -> rbuf_offset + offset;
 516                 hdr.bh_caplen -= offset;
 517
 518                 /* If there's not enough room to stash the packet data,
 519                    we have to skip it (this shouldn't happen in real
 520                    life, though). */
 521                 if (hdr.bh_caplen > len) {
 522                         interface -> rbuf_offset =
 523                                 BPF_WORDALIGN (interface -> rbuf_offset +
 524                                                hdr.bh_caplen);
 525                         continue;
 526                 }
 527
 528                 /* Copy out the data in the packet... */
 529                 memcpy (buf, interface -> rbuf + interface -> rbuf_offset,
 530                         paylen);
 531                 interface -> rbuf_offset =
 532                         BPF_WORDALIGN (interface -> rbuf_offset +
 533                                        hdr.bh_caplen);
 534                 return paylen;
 535         } while (!length);
 536         return 0;
 537 }
 538
 539 int can_unicast_without_arp (ip)
 540         struct interface_info *ip;
 541 {
 542         return 1;
 543 }
 544
 545 int can_receive_unicast_unconfigured (ip)
 546         struct interface_info *ip;
 547 {
 548         return 1;
 549 }
 550
 551 int supports_multiple_interfaces (ip)
 552         struct interface_info *ip;
 553 {
 554         return 1;
 555 }
 556
 557 void maybe_setup_fallback ()
 558 {
 559         isc_result_t status;
 560         struct interface_info *fbi = (struct interface_info *)0;
 561         if (setup_fallback (&fbi, MDL)) {
 562                 if_register_fallback (fbi);
 563                 status = omapi_register_io_object ((omapi_object_t *)fbi,
 564                                                    if_readsocket, 0,
 565                                                    fallback_discard, 0, 0);
 566                 if (status != ISC_R_SUCCESS)
 567                         log_fatal ("Can't register I/O handle for %s: %s",
 568                                    fbi -> name, isc_result_totext (status));
 569                 interface_dereference (&fbi, MDL);
 570         }
 571 }
 572 #endif