common/bpf.c

   1 /* bpf.c
   2
   3    BPF socket interface code, originally contributed by Archie Cobbs. */
   4
   5 /*
   6  * Copyright (c) 1996-1999 Internet Software Consortium.
   7  * Use is subject to license terms which appear in the file named
   8  * ISC-LICENSE that should have accompanied this file when you
   9  * received it.   If a file named ISC-LICENSE did not accompany this
  10  * file, or you are not sure the one you have is correct, you may
  11  * obtain an applicable copy of the license at:
  12  *
  13  *             http://www.isc.org/isc-license-1.0.html.
  14  *
  15  * This file is part of the ISC DHCP distribution.   The documentation
  16  * associated with this file is listed in the file DOCUMENTATION,
  17  * included in the top-level directory of this release.
  18  *
  19  * Support and other services are available for ISC products - see
  20  * http://www.isc.org for more information.
  21  */
  22
  23 #ifndef lint
  24 static char copyright[] =
  25 "$Id: bpf.c,v 1.34 2000/03/06 19:39:53 mellon Exp $ Copyright (c) 1995, 1996 The Internet Software Consortium.  All rights reserved.\n";
  26 #endif /* not lint */
  27
  28 #include "dhcpd.h"
  29 #if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE) \
  30                                 || defined (USE_LPF_RECEIVE)
  31 # if defined (USE_LPF_RECEIVE)
  32 #  include <asm/types.h>
  33 #  include <linux/filter.h>
  34 #  define bpf_insn sock_filter /* Linux: dare to be gratuitously different. */
  35 # else
  36 #  include <sys/ioctl.h>
  37 #  include <sys/uio.h>
  38 #  include <net/bpf.h>
  39 #  if defined (NEED_OSF_PFILT_HACKS)
  40 #   include <net/pfilt.h>
  41 #  endif
  42 # endif
  43
  44 #include <netinet/in_systm.h>
  45 #include "includes/netinet/ip.h"
  46 #include "includes/netinet/udp.h"
  47 #include "includes/netinet/if_ether.h"
  48 #endif
  49
  50 /* Reinitializes the specified interface after an address change.   This
  51    is not required for packet-filter APIs. */
  52
  53 #ifdef USE_BPF_SEND
  54 void if_reinitialize_send (info)
  55         struct interface_info *info;
  56 {
  57 }
  58 #endif
  59
  60 #ifdef USE_BPF_RECEIVE
  61 void if_reinitialize_receive (info)
  62         struct interface_info *info;
  63 {
  64 }
  65 #endif
  66
  67 /* Called by get_interface_list for each interface that's discovered.
  68    Opens a packet filter for each interface and adds it to the select
  69    mask. */
  70
  71 #if defined (USE_BPF_SEND) || defined (USE_BPF_RECEIVE)
  72 int if_register_bpf (info)
  73         struct interface_info *info;
  74 {
  75         int sock;
  76         char filename[50];
  77         int b;
  78
  79         /* Open a BPF device */
  80         for (b = 0; 1; b++) {
  81 #ifndef NO_SNPRINTF
  82                 snprintf(filename, sizeof(filename), BPF_FORMAT, b);
  83 #else
  84                 sprintf(filename, BPF_FORMAT, b);
  85 #endif
  86                 sock = open (filename, O_RDWR, 0);
  87                 if (sock < 0) {
  88                         if (errno == EBUSY) {
  89                                 continue;
  90                         } else {
  91                                 if (!b)
  92                                         log_fatal ("No bpf devices.%s%s%s",
  93                                                "   Please read the README",
  94                                                " section for your operating",
  95                                                " system.");
  96                                 log_fatal ("Can't find free bpf: %m");
  97                         }
  98                 } else {
  99                         break;
 100                 }
 101         }
 102
 103         /* Set the BPF device to point at this interface. */
 104         if (ioctl (sock, BIOCSETIF, info -> ifp) < 0)
 105                 log_fatal ("Can't attach interface %s to bpf device %s: %m",
 106                        info -> name, filename);
 107
 108         return sock;
 109 }
 110 #endif /* USE_BPF_SEND || USE_BPF_RECEIVE */
 111
 112 #ifdef USE_BPF_SEND
 113 void if_register_send (info)
 114         struct interface_info *info;
 115 {
 116         /* If we're using the bpf API for sending and receiving,
 117            we don't need to register this interface twice. */
 118 #ifndef USE_BPF_RECEIVE
 119         info -> wfdesc = if_register_bpf (info, interface);
 120 #else
 121         info -> wfdesc = info -> rfdesc;
 122 #endif
 123         if (!quiet_interface_discovery)
 124                 log_info ("Sending on   BPF/%s/%s%s%s",
 125                       info -> name,
 126                       print_hw_addr (info -> hw_address.hbuf [0],
 127                                      info -> hw_address.hlen - 1,
 128                                      &info -> hw_address.hbuf [1]),
 129                       (info -> shared_network ? "/" : ""),
 130                       (info -> shared_network ?
 131                        info -> shared_network -> name : ""));
 132 }
 133
 134 void if_deregister_send (info)
 135         struct interface_info *info;
 136 {
 137         /* If we're using the bpf API for sending and receiving,
 138            we don't need to register this interface twice. */
 139 #ifndef USE_BPF_RECEIVE
 140         close (info -> wfdesc);
 141 #endif
 142         info -> wfdesc = -1;
 143
 144         if (!quiet_interface_discovery)
 145                 log_info ("Disabling output on BPF/%s/%s%s%s",
 146                       info -> name,
 147                       print_hw_addr (info -> hw_address.hbuf [0],
 148                                      info -> hw_address.hlen - 1,
 149                                      &info -> hw_address.hbuf [1]),
 150                       (info -> shared_network ? "/" : ""),
 151                       (info -> shared_network ?
 152                        info -> shared_network -> name : ""));
 153 }
 154 #endif /* USE_BPF_SEND */
 155
 156 #if defined (USE_BPF_RECEIVE) || defined (USE_LPF_RECEIVE)
 157 /* Packet filter program...
 158    XXX Changes to the filter program may require changes to the constant
 159    offsets used in if_register_send to patch the BPF program! XXX */
 160
 161 struct bpf_insn dhcp_bpf_filter [] = {
 162         /* Make sure this is an IP packet... */
 163         BPF_STMT (BPF_LD + BPF_H + BPF_ABS, 12),
 164         BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 0, 8),
 165
 166         /* Make sure it's a UDP packet... */
 167         BPF_STMT (BPF_LD + BPF_B + BPF_ABS, 23),
 168         BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 0, 6),
 169
 170         /* Make sure this isn't a fragment... */
 171         BPF_STMT(BPF_LD + BPF_H + BPF_ABS, 20),
 172         BPF_JUMP(BPF_JMP + BPF_JSET + BPF_K, 0x1fff, 4, 0),
 173
 174         /* Get the IP header length... */
 175         BPF_STMT (BPF_LDX + BPF_B + BPF_MSH, 14),
 176
 177         /* Make sure it's to the right port... */
 178         BPF_STMT (BPF_LD + BPF_H + BPF_IND, 16),
 179         BPF_JUMP (BPF_JMP + BPF_JEQ + BPF_K, 67, 0, 1),             /* patch */
 180
 181         /* If we passed all the tests, ask for the whole packet. */
 182         BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
 183
 184         /* Otherwise, drop it. */
 185         BPF_STMT(BPF_RET+BPF_K, 0),
 186 };
 187
 188 int dhcp_bpf_filter_len = sizeof dhcp_bpf_filter / sizeof (struct bpf_insn);
 189 struct bpf_insn dhcp_bpf_tr_filter [] = {
 190         /* accept all token ring packets due to variable length header */
 191         /* if we want to get clever, insert the program here */
 192
 193         /* If we passed all the tests, ask for the whole packet. */
 194         BPF_STMT(BPF_RET+BPF_K, (u_int)-1),
 195
 196         /* Otherwise, drop it. */
 197         BPF_STMT(BPF_RET+BPF_K, 0),
 198 };
 199
 200 int dhcp_bpf_tr_filter_len = (sizeof dhcp_bpf_tr_filter /
 201                               sizeof (struct bpf_insn));
 202 #endif
 203
 204 #if defined (USE_BPF_RECEIVE)
 205 void if_register_receive (info)
 206         struct interface_info *info;
 207 {
 208         int flag = 1;
 209         struct bpf_version v;
 210         u_int32_t addr;
 211         struct bpf_program p;
 212         u_int32_t bits;
 213
 214         /* Open a BPF device and hang it on this interface... */
 215         info -> rfdesc = if_register_bpf (info);
 216
 217         /* Make sure the BPF version is in range... */
 218         if (ioctl (info -> rfdesc, BIOCVERSION, &v) < 0)
 219                 log_fatal ("Can't get BPF version: %m");
 220
 221         if (v.bv_major != BPF_MAJOR_VERSION ||
 222             v.bv_minor < BPF_MINOR_VERSION)
 223                 log_fatal ("Kernel BPF version out of range - recompile dhcpd!");
 224
 225         /* Set immediate mode so that reads return as soon as a packet
 226            comes in, rather than waiting for the input buffer to fill with
 227            packets. */
 228         if (ioctl (info -> rfdesc, BIOCIMMEDIATE, &flag) < 0)
 229                 log_fatal ("Can't set immediate mode on bpf device: %m");
 230
 231 #ifdef NEED_OSF_PFILT_HACKS
 232         /* Allow the copyall flag to be set... */
 233         if (ioctl(info -> rfdesc, EIOCALLOWCOPYALL, &flag) < 0)
 234                 log_fatal ("Can't set ALLOWCOPYALL: %m");
 235
 236         /* Clear all the packet filter mode bits first... */
 237         bits = 0;
 238         if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0)
 239                 log_fatal ("Can't clear pfilt bits: %m");
 240
 241         /* Set the ENBATCH, ENCOPYALL, ENBPFHDR bits... */
 242         bits = ENBATCH | ENCOPYALL | ENBPFHDR;
 243         if (ioctl (info -> rfdesc, EIOCMBIS, &bits) < 0)
 244                 log_fatal ("Can't set ENBATCH|ENCOPYALL|ENBPFHDR: %m");
 245 #endif
 246         /* Get the required BPF buffer length from the kernel. */
 247         if (ioctl (info -> rfdesc, BIOCGBLEN, &info -> rbuf_max) < 0)
 248                 log_fatal ("Can't get bpf buffer length: %m");
 249         info -> rbuf = dmalloc (info -> rbuf_max, MDL);
 250         if (!info -> rbuf)
 251                 log_fatal ("Can't allocate %d bytes for bpf input buffer.",
 252                            info -> rbuf_max);
 253         info -> rbuf_offset = 0;
 254         info -> rbuf_len = 0;
 255
 256         /* Set up the bpf filter program structure. */
 257         p.bf_len = dhcp_bpf_filter_len;
 258         p.bf_insns = dhcp_bpf_filter;
 259
 260         /* Patch the server port into the BPF  program...
 261            XXX changes to filter program may require changes
 262            to the insn number(s) used below! XXX */
 263         dhcp_bpf_filter [8].k = ntohs (local_port);
 264
 265         if (ioctl (info -> rfdesc, BIOCSETF, &p) < 0)
 266                 log_fatal ("Can't install packet filter program: %m");
 267         if (!quiet_interface_discovery)
 268                 log_info ("Listening on BPF/%s/%s%s%s",
 269                       info -> name,
 270                       print_hw_addr (info -> hw_address.hbuf [0],
 271                                      info -> hw_address.hlen - 1,
 272                                      &info -> hw_address.hbuf [1]),
 273                       (info -> shared_network ? "/" : ""),
 274                       (info -> shared_network ?
 275                        info -> shared_network -> name : ""));
 276 }
 277
 278 void if_deregister_receive (info)
 279         struct interface_info *info;
 280 {
 281         close (info -> rfdesc);
 282         info -> rfdesc = -1;
 283
 284         if (!quiet_interface_discovery)
 285                 log_info ("Disabling input on BPF/%s/%s%s%s",
 286                       info -> name,
 287                       print_hw_addr (info -> hw_address.hbuf [0],
 288                                      info -> hw_address.hlen - 1,
 289                                      &info -> hw_address.hbuf [1]),
 290                       (info -> shared_network ? "/" : ""),
 291                       (info -> shared_network ?
 292                        info -> shared_network -> name : ""));
 293 }
 294 #endif /* USE_BPF_RECEIVE */
 295
 296 #ifdef USE_BPF_SEND
 297 ssize_t send_packet (interface, packet, raw, len, from, to, hto)
 298         struct interface_info *interface;
 299         struct packet *packet;
 300         struct dhcp_packet *raw;
 301         size_t len;
 302         struct in_addr from;
 303         struct sockaddr_in *to;
 304         struct hardware *hto;
 305 {
 306         unsigned bufp = 0;
 307         unsigned char buf [256];
 308         struct iovec iov [2];
 309         int result;
 310
 311         if (!strcmp (interface -> name, "fallback"))
 312                 return send_fallback (interface, packet, raw,
 313                                       len, from, to, hto);
 314
 315         /* Assemble the headers... */
 316         assemble_hw_header (interface, buf, &bufp, hto);
 317         assemble_udp_ip_header (interface, buf, &bufp, from.s_addr,
 318                                 to -> sin_addr.s_addr, to -> sin_port,
 319                                 (unsigned char *)raw, len);
 320
 321         /* Fire it off */
 322         iov [0].iov_base = (char *)buf;
 323         iov [0].iov_len = bufp;
 324         iov [1].iov_base = (char *)raw;
 325         iov [1].iov_len = len;
 326
 327         result = writev(interface -> wfdesc, iov, 2);
 328         if (result < 0)
 329                 log_error ("send_packet: %m");
 330         return result;
 331 }
 332 #endif /* USE_BPF_SEND */
 333
 334 #ifdef USE_BPF_RECEIVE
 335 ssize_t receive_packet (interface, buf, len, from, hfrom)
 336         struct interface_info *interface;
 337         unsigned char *buf;
 338         size_t len;
 339         struct sockaddr_in *from;
 340         struct hardware *hfrom;
 341 {
 342         int length = 0;
 343         int offset = 0;
 344         struct bpf_hdr hdr;
 345
 346         /* All this complexity is because BPF doesn't guarantee
 347            that only one packet will be returned at a time.   We're
 348            getting what we deserve, though - this is a terrible abuse
 349            of the BPF interface.   Sigh. */
 350
 351         /* Process packets until we get one we can return or until we've
 352            done a read and gotten nothing we can return... */
 353
 354         do {
 355                 /* If the buffer is empty, fill it. */
 356                 if (interface -> rbuf_offset == interface -> rbuf_len) {
 357                         length = read (interface -> rfdesc,
 358                                        interface -> rbuf,
 359                                        interface -> rbuf_max);
 360                         if (length <= 0)
 361                                 return length;
 362                         interface -> rbuf_offset = 0;
 363                         interface -> rbuf_len = length;
 364                 }
 365
 366                 /* If there isn't room for a whole bpf header, something went
 367                    wrong, but we'll ignore it and hope it goes away... XXX */
 368                 if (interface -> rbuf_len -
 369                     interface -> rbuf_offset < sizeof hdr) {
 370                         interface -> rbuf_offset = interface -> rbuf_len;
 371                         continue;
 372                 }
 373
 374                 /* Copy out a bpf header... */
 375                 memcpy (&hdr, &interface -> rbuf [interface -> rbuf_offset],
 376                         sizeof hdr);
 377
 378                 /* If the bpf header plus data doesn't fit in what's left
 379                    of the buffer, stick head in sand yet again... */
 380                 if (interface -> rbuf_offset +
 381                     hdr.bh_hdrlen + hdr.bh_caplen > interface -> rbuf_len) {
 382                         interface -> rbuf_offset = interface -> rbuf_len;
 383                         continue;
 384                 }
 385
 386                 /* If the captured data wasn't the whole packet, or if
 387                    the packet won't fit in the input buffer, all we
 388                    can do is drop it. */
 389                 if (hdr.bh_caplen != hdr.bh_datalen) {
 390                         interface -> rbuf_offset +=
 391                                 hdr.bh_hdrlen = hdr.bh_caplen;
 392                         continue;
 393                 }
 394
 395                 /* Skip over the BPF header... */
 396                 interface -> rbuf_offset += hdr.bh_hdrlen;
 397
 398                 /* Decode the physical header... */
 399                 offset = decode_hw_header (interface,
 400                                            interface -> rbuf,
 401                                            interface -> rbuf_offset,
 402                                            hfrom);
 403
 404                 /* If a physical layer checksum failed (dunno of any
 405                    physical layer that supports this, but WTH), skip this
 406                    packet. */
 407                 if (offset < 0) {
 408                         interface -> rbuf_offset += hdr.bh_caplen;
 409                         continue;
 410                 }
 411                 interface -> rbuf_offset += offset;
 412                 hdr.bh_caplen -= offset;
 413
 414                 /* Decode the IP and UDP headers... */
 415                 offset = decode_udp_ip_header (interface,
 416                                                interface -> rbuf,
 417                                                interface -> rbuf_offset,
 418                                                from,
 419                                                (unsigned char *)0,
 420                                                hdr.bh_caplen);
 421
 422                 /* If the IP or UDP checksum was bad, skip the packet... */
 423                 if (offset < 0) {
 424                         interface -> rbuf_offset += hdr.bh_caplen;
 425                         continue;
 426                 }
 427                 interface -> rbuf_offset += offset;
 428                 hdr.bh_caplen -= offset;
 429
 430                 /* If there's not enough room to stash the packet data,
 431                    we have to skip it (this shouldn't happen in real
 432                    life, though). */
 433                 if (hdr.bh_caplen > len) {
 434                         interface -> rbuf_offset += hdr.bh_caplen;
 435                         continue;
 436                 }
 437
 438                 /* Copy out the data in the packet... */
 439                 memcpy (buf, interface -> rbuf + interface -> rbuf_offset,
 440                         hdr.bh_caplen);
 441                 interface -> rbuf_offset += hdr.bh_caplen;
 442                 return hdr.bh_caplen;
 443         } while (!length);
 444         return 0;
 445 }
 446
 447 int can_unicast_without_arp (ip)
 448         struct interface_info *ip;
 449 {
 450         return 1;
 451 }
 452
 453 int can_receive_unicast_unconfigured (ip)
 454         struct interface_info *ip;
 455 {
 456         return 1;
 457 }
 458
 459 void maybe_setup_fallback ()
 460 {
 461         isc_result_t status;
 462         struct interface_info *fbi;
 463         fbi = setup_fallback ();
 464         if (fbi) {
 465                 if_register_fallback (fbi);
 466                 fbi -> refcnt = 1;
 467                 fbi -> type = dhcp_type_interface;
 468                 status = omapi_register_io_object ((omapi_object_t *)fbi,
 469                                                    if_readsocket, 0,
 470                                                    fallback_discard, 0, 0);
 471                 if (status != ISC_R_SUCCESS)
 472                         log_fatal ("Can't register I/O handle for %s: %s",
 473                                    fbi -> name, isc_result_totext (status));
 474         }
 475 }
 476 #endif