common/bpf.c

   1 /* bpf.c
   2
   3    BPF socket interface code, originally contributed by Archie Cobbs. */
   4
   5 /*
   6  * Copyright (c) 1996-2000 Internet Software Consortium.
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  *
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of The Internet Software Consortium nor the names
  19  *    of its contributors may be used to endorse or promote products derived
  20  *    from this software without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE INTERNET SOFTWARE CONSORTIUM AND
  23  * CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
  24  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  25  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  26  * DISCLAIMED.  IN NO EVENT SHALL THE INTERNET SOFTWARE CONSORTIUM OR
  27  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  28  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  29  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  30  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  31  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  32  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  33  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * This software was contributed to the Internet Software Consortium
  37  * by Archie Cobbs, and is now maintained by Ted Lemon in cooperation
  38  * with Nominum, Inc.  To learn more about the Internet Software
  39  * Consortium, see ``http://www.isc.org/''.  To learn more about Vixie
  40  * Enterprises, see ``http://www.vix.com''.  To learn more about
  41  * Nominum, Inc., see ``http://www.nominum.com''.
  42  *
  43  * Patches for FDDI support on Digital Unix were written by Bill
  44  * Stapleton, and maintained for a while by Mike Meredith before he
  45  * managed to get me to integrate them.
  46  */
  47
  48 #ifndef lint
  49 static char copyright[] =
  50 "$Id: bpf.c,v 1.42 2000/09/01 23:03:31 mellon Exp $ Copyright (c) 1995-2000 The Internet Software Consortium.  All rights reserved.\n";
  51 #endif /* not lint */
  52
  53 #include "dhcpd.h"
  54 #if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE) \
  55                                 || defined (USE_LPF_RECEIVE)
  56 # if defined (USE_LPF_RECEIVE)
  57 #  include <asm/types.h>
  58 #  include <linux/filter.h>
  59 #  define bpf_insn sock_filter /* Linux: dare to be gratuitously different. */
  60 # else
  61 #  include <sys/ioctl.h>
  62 #  include <sys/uio.h>
  63 #  include <net/bpf.h>
  64 #  if defined (NEED_OSF_PFILT_HACKS)
  65 #   include <net/pfilt.h>
  66 #  endif
  67 # endif
  68
  69 #include <netinet/in_systm.h>
  70 #include "includes/netinet/ip.h"
  71 #include "includes/netinet/udp.h"
  72 #include "includes/netinet/if_ether.h"
  73 #endif
  74
  75 /* Reinitializes the specified interface after an address change.   This
  76    is not required for packet-filter APIs. */
  77
  78 #ifdef USE_BPF_SEND
  79 void if_reinitialize_send (info)
  80         struct interface_info *info;
  81 {
  82 }
  83 #endif
  84
  85 #ifdef USE_BPF_RECEIVE
  86 void if_reinitialize_receive (info)
  87         struct interface_info *info;
  88 {
  89 }
  90 #endif
  91
  92 /* Called by get_interface_list for each interface that's discovered.
  93    Opens a packet filter for each interface and adds it to the select
  94    mask. */
  95
  96 #if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE)
  97 int if_register_bpf (info)
  98         struct interface_info *info;
  99 {
 100         int sock;
 101         char filename[50];
 102         int b;
 103
 104         /* Open a BPF device */
 105         for (b = 0; 1; b++) {
 106 #ifndef NO_SNPRINTF
 107                 snprintf(filename, sizeof(filename), BPF_FORMAT, b);
 108 #else
 109                 sprintf(filename, BPF_FORMAT, b);
 110 #endif
 111                 sock = open (filename, O_RDWR, 0);
 112                 if (sock < 0) {
 113                         if (errno == EBUSY) {
 114                                 continue;
 115                         } else {
 116                                 if (!b)
 117                                         log_fatal ("No bpf devices.%s%s%s",
 118                                                "   Please read the README",
 119                                                " section for your operating",
 120                                                " system.");
 121                                 log_fatal ("Can't find free bpf: %m");
 122                         }
 123                 } else {
 124                         break;
 125                 }
 126         }
 127
 128         /* Set the BPF device to point at this interface. */
 129         if (ioctl (sock, BIOCSETIF, info -> ifp) < 0)
 130                 log_fatal ("Can't attach interface %s to bpf device %s: %m",
 131                        info -> name, filename);
 132
 133         return sock;
 134 }
 135 #endif /* USE_BPF_SEND || USE_BPF_RECEIVE */
 136
 137 #ifdef USE_BPF_SEND
 138 void if_register_send (info)
 139         struct interface_info *info;
 140 {
 141         /* If we're using the bpf API for sending and receiving,
 142            we don't need to register this interface twice. */
 143 #ifndef USE_BPF_RECEIVE
 144         info -> wfdesc = if_register_bpf (info, interface);
 145 #else
 146         info -> wfdesc = info -> rfdesc;
 147 #endif
 148         if (!quiet_interface_discovery)
 149                 log_info ("Sending on   BPF/%s/%s%s%s",
 150                       info -> name,
 151                       print_hw_addr (info -> hw_address.hbuf [0],
 152                                      info -> hw_address.hlen - 1,
 153                                      &info -> hw_address.hbuf [1]),
 154                       (info -> shared_network ? "/" : ""),
 155                       (info -> shared_network ?
 156                        info -> shared_network -> name : ""));
 157 }
 158
 159 void if_deregister_send (info)
 160         struct interface_info *info;
 161 {
 162         /* If we're using the bpf API for sending and receiving,
 163            we don't need to register this interface twice. */
 164 #ifndef USE_BPF_RECEIVE
 165         close (info -> wfdesc);
 166 #endif
 167         info -> wfdesc = -1;
 168
 169         if (!quiet_interface_discovery)
 170                 log_info ("Disabling output on BPF/%s/%s%s%s",
 171                       info -> name,
 172                       print_hw_addr (info -> hw_address.hbuf [0],
 173                                      info -> hw_address.hlen - 1,
 174                                      &info -> hw_address.hbuf [1]),
 175                       (info -> shared_network ? "/" : ""),
 176                       (info -> shared_network ?
 177                        info -> shared_network -> name : ""));
 178 }
 179 #endif /* USE_BPF_SEND */
 180
 181 #if defined (USE_BPF_RECEIVE) || defined (USE_LPF_RECEIVE)
 182 /* Packet filter program...
 183    XXX Changes to the filter program may require changes to the constant
 184    offsets used in if_register_send to patch the BPF program! XXX */
 185
 186 struct bpf_insn dhcp_bpf_filter [] = {
 187         /* Make sure this is an IP packet... */
 188         BPF_STMT (BPF_LD + BPF_H + BPF_ABS, 12),
 189         BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
 190
 191         /* Make sure it's a UDP packet... */
 192         BPF_STMT (BPF_LD + BPF_B + BPF_ABS, 23),
 193         BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
 194
 195         /* Make sure this isn't a fragment... */
 196         BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
 197         BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
 198
 199         /* Get the IP header length... */
 200         BPF_STMT (BPF_LDX + BPF_B + BPF_MSH, 14),
 201
 202         /* Make sure it's to the right port... */
 203         BPF_STMT (BPF_LD + BPF_H + BPF_IND, 16),
 204         BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1),             /* patch */
 205
 206         /* If we passed all the tests, ask for the whole packet. */
 207         BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
 208
 209         /* Otherwise, drop it. */
 210         BPF_STMT(BPF_RET+BPF_K, 0),
 211 };
 212
 213 struct bpf_insn *bpf_fddi_filter;
 214
 215 int dhcp_bpf_filter_len = sizeof dhcp_bpf_filter / sizeof (struct bpf_insn);
 216 struct bpf_insn dhcp_bpf_tr_filter [] = {
 217         /* accept all token ring packets due to variable length header */
 218         /* if we want to get clever, insert the program here */
 219
 220         /* If we passed all the tests, ask for the whole packet. */
 221         BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
 222
 223         /* Otherwise, drop it. */
 224         BPF_STMT(BPF_RET+BPF_K, 0),
 225 };
 226
 227 int dhcp_bpf_tr_filter_len = (sizeof dhcp_bpf_tr_filter /
 228                               sizeof (struct bpf_insn));
 229 #endif
 230
 231 #if defined (USE_BPF_RECEIVE)
 232 void if_register_receive (info)
 233         struct interface_info *info;
 234 {
 235         int flag = 1;
 236         struct bpf_version v;
 237         u_int32_t addr;
 238         struct bpf_program p;
 239         u_int32_t bits;
 240 #ifdef DEC_FDDI
 241         int link_layer;
 242 #endif /* DEC_FDDI */
 243
 244         /* Open a BPF device and hang it on this interface... */
 245         info -> rfdesc = if_register_bpf (info);
 246
 247         /* Make sure the BPF version is in range... */
 248         if (ioctl (info -> rfdesc, BIOCVERSION, &v) < 0)
 249                 log_fatal ("Can't get BPF version: %m");
 250
 251         if (v.bv_major != BPF_MAJOR_VERSION ||
 252             v.bv_minor < BPF_MINOR_VERSION)
 253                 log_fatal ("Kernel BPF version out of range - recompile dhcpd!");
 254
 255         /* Set immediate mode so that reads return as soon as a packet
 256            comes in, rather than waiting for the input buffer to fill with
 257            packets. */
 258         if (ioctl (info -> rfdesc, BIOCIMMEDIATE, &flag) < 0)
 259                 log_fatal ("Can't set immediate mode on bpf device: %m");
 260
 261 #ifdef NEED_OSF_PFILT_HACKS
 262         /* Allow the copyall flag to be set... */
 263         if (ioctl(info -> rfdesc, EIOCALLOWCOPYALL, &flag) < 0)
 264                 log_fatal ("Can't set ALLOWCOPYALL: %m");
 265
 266         /* Clear all the packet filter mode bits first... */
 267         bits = 0;
 268         if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0)
 269                 log_fatal ("Can't clear pfilt bits: %m");
 270
 271         /* Set the ENBATCH, ENCOPYALL, ENBPFHDR bits... */
 272         bits = ENBATCH | ENCOPYALL | ENBPFHDR;
 273         if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0)
 274                 log_fatal ("Can't set ENBATCH|ENCOPYALL|ENBPFHDR: %m");
 275 #endif
 276         /* Get the required BPF buffer length from the kernel. */
 277         if (ioctl (info -> rfdesc, BIOCGBLEN, &info -> rbuf_max) < 0)
 278                 log_fatal ("Can't get bpf buffer length: %m");
 279         info -> rbuf = dmalloc (info -> rbuf_max, MDL);
 280         if (!info -> rbuf)
 281                 log_fatal ("Can't allocate %d bytes for bpf input buffer.",
 282                            info -> rbuf_max);
 283         info -> rbuf_offset = 0;
 284         info -> rbuf_len = 0;
 285
 286         /* Set up the bpf filter program structure. */
 287         p.bf_len = dhcp_bpf_filter_len;
 288
 289 #ifdef DEC_FDDI
 290         /* See if this is an FDDI interface, flag it for later. */
 291         if (ioctl(info -> rfdesc, BIOCGDLT, &link_layer) >= 0 &&
 292             link_layer == DLT_FDDI) {
 293                 if (!bpf_fddi_filter) {
 294                         bpf_fddi_filter = dmalloc (sizeof bpf_fddi_filter,
 295                                                     MDL);
 296                         if (!bpf_fddi_filter)
 297                                 log_fatal ("No memory for FDDI filter.");
 298                         memcpy (bpf_fddi_filter,
 299                                 dhcp_bpf_filter, sizeof dhcp_bpf_filter);
 300                         /* Patch the BPF program to account for the difference
 301                            in length between ethernet headers (14), FDDI and
 302                            802.2 headers (16 +8=24, +10).
 303                            XXX changes to filter program may require changes to
 304                            XXX the insn number(s) used below! */
 305                         bpf_fddi_filter[0].k += 10;
 306                         bpf_fddi_filter[2].k += 10;
 307                         bpf_fddi_filter[4].k += 10;
 308                         bpf_fddi_filter[6].k += 10;
 309                         bpf_fddi_filter[7].k += 10;
 310                 }
 311                 p.bf_insns = bpf_fddi_filter;
 312         } else
 313 #endif /* DEC_FDDI */
 314         p.bf_insns = dhcp_bpf_filter;
 315
 316         /* Patch the server port into the BPF  program...
 317            XXX changes to filter program may require changes
 318            to the insn number(s) used below! XXX */
 319         dhcp_bpf_filter [8].k = ntohs (local_port);
 320
 321         if (ioctl (info -> rfdesc, BIOCSETF, &p) < 0)
 322                 log_fatal ("Can't install packet filter program: %m");
 323         if (!quiet_interface_discovery)
 324                 log_info ("Listening on BPF/%s/%s%s%s",
 325                       info -> name,
 326                       print_hw_addr (info -> hw_address.hbuf [0],
 327                                      info -> hw_address.hlen - 1,
 328                                      &info -> hw_address.hbuf [1]),
 329                       (info -> shared_network ? "/" : ""),
 330                       (info -> shared_network ?
 331                        info -> shared_network -> name : ""));
 332 }
 333
 334 void if_deregister_receive (info)
 335         struct interface_info *info;
 336 {
 337         close (info -> rfdesc);
 338         info -> rfdesc = -1;
 339
 340         if (!quiet_interface_discovery)
 341                 log_info ("Disabling input on BPF/%s/%s%s%s",
 342                       info -> name,
 343                       print_hw_addr (info -> hw_address.hbuf [0],
 344                                      info -> hw_address.hlen - 1,
 345                                      &info -> hw_address.hbuf [1]),
 346                       (info -> shared_network ? "/" : ""),
 347                       (info -> shared_network ?
 348                        info -> shared_network -> name : ""));
 349 }
 350 #endif /* USE_BPF_RECEIVE */
 351
 352 #ifdef USE_BPF_SEND
 353 ssize_t send_packet (interface, packet, raw, len, from, to, hto)
 354         struct interface_info *interface;
 355         struct packet *packet;
 356         struct dhcp_packet *raw;
 357         size_t len;
 358         struct in_addr from;
 359         struct sockaddr_in *to;
 360         struct hardware *hto;
 361 {
 362         unsigned hbufp = 0, ibufp = 0;
 363         double hw [4];
 364         double ip [32];
 365         struct iovec iov [3];
 366         int result;
 367         int fudge;
 368
 369         if (!strcmp (interface -> name, "fallback"))
 370                 return send_fallback (interface, packet, raw,
 371                                       len, from, to, hto);
 372
 373         /* Assemble the headers... */
 374         assemble_hw_header (interface, (unsigned char *)hw, &hbufp, hto);
 375         assemble_udp_ip_header (interface,
 376                                 (unsigned char *)ip, &ibufp, from.s_addr,
 377                                 to -> sin_addr.s_addr, to -> sin_port,
 378                                 (unsigned char *)raw, len);
 379
 380         /* Fire it off */
 381         iov [0].iov_base = ((char *)hw);
 382         iov [0].iov_len = hbufp;
 383         iov [1].iov_base = ((char *)ip);
 384         iov [1].iov_len = ibufp;
 385         iov [2].iov_base = (char *)raw;
 386         iov [2].iov_len = len;
 387
 388         result = writev(interface -> wfdesc, iov, 3);
 389         if (result < 0)
 390                 log_error ("send_packet: %m");
 391         return result;
 392 }
 393 #endif /* USE_BPF_SEND */
 394
 395 #ifdef USE_BPF_RECEIVE
 396 ssize_t receive_packet (interface, buf, len, from, hfrom)
 397         struct interface_info *interface;
 398         unsigned char *buf;
 399         size_t len;
 400         struct sockaddr_in *from;
 401         struct hardware *hfrom;
 402 {
 403         int length = 0;
 404         int offset = 0;
 405         struct bpf_hdr hdr;
 406
 407         /* All this complexity is because BPF doesn't guarantee
 408            that only one packet will be returned at a time.   We're
 409            getting what we deserve, though - this is a terrible abuse
 410            of the BPF interface.   Sigh. */
 411
 412         /* Process packets until we get one we can return or until we've
 413            done a read and gotten nothing we can return... */
 414
 415         do {
 416                 /* If the buffer is empty, fill it. */
 417                 if (interface -> rbuf_offset == interface -> rbuf_len) {
 418                         length = read (interface -> rfdesc,
 419                                        interface -> rbuf,
 420                                        interface -> rbuf_max);
 421                         if (length <= 0)
 422                                 return length;
 423                         interface -> rbuf_offset = 0;
 424                         interface -> rbuf_len = length;
 425                 }
 426
 427                 /* If there isn't room for a whole bpf header, something went
 428                    wrong, but we'll ignore it and hope it goes away... XXX */
 429                 if (interface -> rbuf_len -
 430                     interface -> rbuf_offset < sizeof hdr) {
 431                         interface -> rbuf_offset = interface -> rbuf_len;
 432                         continue;
 433                 }
 434
 435                 /* Copy out a bpf header... */
 436                 memcpy (&hdr, &interface -> rbuf [interface -> rbuf_offset],
 437                         sizeof hdr);
 438
 439                 /* If the bpf header plus data doesn't fit in what's left
 440                    of the buffer, stick head in sand yet again... */
 441                 if (interface -> rbuf_offset +
 442                     hdr.bh_hdrlen + hdr.bh_caplen > interface -> rbuf_len) {
 443                         interface -> rbuf_offset = interface -> rbuf_len;
 444                         continue;
 445                 }
 446
 447                 /* If the captured data wasn't the whole packet, or if
 448                    the packet won't fit in the input buffer, all we
 449                    can do is drop it. */
 450                 if (hdr.bh_caplen != hdr.bh_datalen) {
 451                         interface -> rbuf_offset +=
 452                                 hdr.bh_hdrlen = hdr.bh_caplen;
 453                         continue;
 454                 }
 455
 456                 /* Skip over the BPF header... */
 457                 interface -> rbuf_offset += hdr.bh_hdrlen;
 458
 459                 /* Decode the physical header... */
 460                 offset = decode_hw_header (interface,
 461                                            interface -> rbuf,
 462                                            interface -> rbuf_offset,
 463                                            hfrom);
 464
 465                 /* If a physical layer checksum failed (dunno of any
 466                    physical layer that supports this, but WTH), skip this
 467                    packet. */
 468                 if (offset < 0) {
 469                         interface -> rbuf_offset += hdr.bh_caplen;
 470                         continue;
 471                 }
 472                 interface -> rbuf_offset += offset;
 473                 hdr.bh_caplen -= offset;
 474
 475                 /* Decode the IP and UDP headers... */
 476                 offset = decode_udp_ip_header (interface,
 477                                                interface -> rbuf,
 478                                                interface -> rbuf_offset,
 479                                                from,
 480                                                (unsigned char *)0,
 481                                                hdr.bh_caplen);
 482
 483                 /* If the IP or UDP checksum was bad, skip the packet... */
 484                 if (offset < 0) {
 485                         interface -> rbuf_offset += hdr.bh_caplen;
 486                         continue;
 487                 }
 488                 interface -> rbuf_offset += offset;
 489                 hdr.bh_caplen -= offset;
 490
 491                 /* If there's not enough room to stash the packet data,
 492                    we have to skip it (this shouldn't happen in real
 493                    life, though). */
 494                 if (hdr.bh_caplen > len) {
 495                         interface -> rbuf_offset += hdr.bh_caplen;
 496                         continue;
 497                 }
 498
 499                 /* Copy out the data in the packet... */
 500                 memcpy (buf, interface -> rbuf + interface -> rbuf_offset,
 501                         hdr.bh_caplen);
 502                 interface -> rbuf_offset += hdr.bh_caplen;
 503                 return hdr.bh_caplen;
 504         } while (!length);
 505         return 0;
 506 }
 507
 508 int can_unicast_without_arp (ip)
 509         struct interface_info *ip;
 510 {
 511         return 1;
 512 }
 513
 514 int can_receive_unicast_unconfigured (ip)
 515         struct interface_info *ip;
 516 {
 517         return 1;
 518 }
 519
 520 int supports_multiple_interfaces (ip)
 521         struct interface_info *ip;
 522 {
 523         return 1;
 524 }
 525
 526 void maybe_setup_fallback ()
 527 {
 528         isc_result_t status;
 529         struct interface_info *fbi = (struct interface_info *)0;
 530         if (setup_fallback (&fbi, MDL)) {
 531                 if_register_fallback (fbi);
 532                 status = omapi_register_io_object ((omapi_object_t *)fbi,
 533                                                    if_readsocket, 0,
 534                                                    fallback_discard, 0, 0);
 535                 if (status != ISC_R_SUCCESS)
 536                         log_fatal ("Can't register I/O handle for %s: %s",
 537                                    fbi -> name, isc_result_totext (status));
 538                 interface_dereference (&fbi, MDL);
 539         }
 540 }
 541 #endif