src/bpf.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * By Daniel Borkmann <daniel@netsniff-ng.org>
   4  * Copyright 2009, 2010 Daniel Borkmann.
   5  * Copyright 2009, 2010 Emmanuel Roullit.
   6  * Copyright 1990-1996 The Regents of the University of
   7  * California. All rights reserved. (3-clause BSD license)
   8  * Subject to the GPL, version 2.
   9  */
  10
  11 #include <stdint.h>
  12 #include <stdio.h>
  13 #include <arpa/inet.h>
  14 #include <sys/types.h>
  15 #include <sys/stat.h>
  16 #include <fcntl.h>
  17
  18 #include "bpf.h"
  19 #include "xmalloc.h"
  20 #include "xutils.h"
  21 #include "die.h"
  22
  23 /* This is a bug in libpcap, they actually use 'unsigned long' instead
  24  * of short! */
  25 #define EXTRACT_SHORT(packet)                                           \
  26                 ((unsigned short) ntohs(*(unsigned short *) packet))
  27 #define EXTRACT_LONG(packet)                                            \
  28                 (ntohl(*(unsigned long *) packet))
  29 #ifndef BPF_MEMWORDS
  30 # define BPF_MEMWORDS 16
  31 #endif
  32
  33 #define BPF_LD_B        (BPF_LD | BPF_B)
  34 #define BPF_LD_H        (BPF_LD | BPF_H)
  35 #define BPF_LD_W        (BPF_LD | BPF_W)
  36 #define BPF_LDX_B       (BPF_LDX | BPF_B)
  37 #define BPF_LDX_W       (BPF_LDX | BPF_W)
  38 #define BPF_JMP_JA      (BPF_JMP | BPF_JA)
  39 #define BPF_JMP_JEQ     (BPF_JMP | BPF_JEQ)
  40 #define BPF_JMP_JGT     (BPF_JMP | BPF_JGT)
  41 #define BPF_JMP_JGE     (BPF_JMP | BPF_JGE)
  42 #define BPF_JMP_JSET    (BPF_JMP | BPF_JSET)
  43 #define BPF_ALU_ADD     (BPF_ALU | BPF_ADD)
  44 #define BPF_ALU_SUB     (BPF_ALU | BPF_SUB)
  45 #define BPF_ALU_MUL     (BPF_ALU | BPF_MUL)
  46 #define BPF_ALU_DIV     (BPF_ALU | BPF_DIV)
  47 #define BPF_ALU_MOD     (BPF_ALU | BPF_MOD)
  48 #define BPF_ALU_NEG     (BPF_ALU | BPF_NEG)
  49 #define BPF_ALU_AND     (BPF_ALU | BPF_AND)
  50 #define BPF_ALU_OR      (BPF_ALU | BPF_OR)
  51 #define BPF_ALU_XOR     (BPF_ALU | BPF_XOR)
  52 #define BPF_ALU_LSH     (BPF_ALU | BPF_LSH)
  53 #define BPF_ALU_RSH     (BPF_ALU | BPF_RSH)
  54 #define BPF_MISC_TAX    (BPF_MISC | BPF_TAX)
  55 #define BPF_MISC_TXA    (BPF_MISC | BPF_TXA)
  56
  57 static const char *op_table[] = {
  58         [BPF_LD_B]      =       "ldb",
  59         [BPF_LD_H]      =       "ldh",
  60         [BPF_LD_W]      =       "ld",
  61         [BPF_LDX]       =       "ldx",
  62         [BPF_LDX_B]     =       "ldxb",
  63         [BPF_ST]        =       "st",
  64         [BPF_STX]       =       "stx",
  65         [BPF_JMP_JA]    =       "ja",
  66         [BPF_JMP_JEQ]   =       "jeq",
  67         [BPF_JMP_JGT]   =       "jgt",
  68         [BPF_JMP_JGE]   =       "jge",
  69         [BPF_JMP_JSET]  =       "jset",
  70         [BPF_ALU_ADD]   =       "add",
  71         [BPF_ALU_SUB]   =       "sub",
  72         [BPF_ALU_MUL]   =       "mul",
  73         [BPF_ALU_DIV]   =       "div",
  74         [BPF_ALU_MOD]   =       "mod",
  75         [BPF_ALU_NEG]   =       "neg",
  76         [BPF_ALU_AND]   =       "and",
  77         [BPF_ALU_OR]    =       "or",
  78         [BPF_ALU_XOR]   =       "xor",
  79         [BPF_ALU_LSH]   =       "lsh",
  80         [BPF_ALU_RSH]   =       "rsh",
  81         [BPF_RET]       =       "ret",
  82         [BPF_MISC_TAX]  =       "tax",
  83         [BPF_MISC_TXA]  =       "txa",
  84 };
  85
  86 void bpf_dump_op_table(void)
  87 {
  88         int i;
  89         for (i = 0; i < array_size(op_table); ++i) {
  90                 if (op_table[i])
  91                         printf("%s\n", op_table[i]);
  92         }
  93 }
  94
  95 static const char *bpf_dump_linux_k(uint32_t k)
  96 {
  97         switch (k) {
  98         default:
  99                 return "[%d]";
 100         /* Linux specific arguments */
 101         case (SKF_AD_OFF + SKF_AD_PROTOCOL):
 102                 return "#proto";
 103         case (SKF_AD_OFF + SKF_AD_PKTTYPE):
 104                 return "#type";
 105         case (SKF_AD_OFF + SKF_AD_IFINDEX):
 106                 return "#ifidx";
 107         case (SKF_AD_OFF + SKF_AD_NLATTR):
 108                 return "#nla";
 109         case (SKF_AD_OFF + SKF_AD_NLATTR_NEST):
 110                 return "#nlan";
 111         case (SKF_AD_OFF + SKF_AD_MARK):
 112                 return "#mark";
 113         case (SKF_AD_OFF + SKF_AD_QUEUE):
 114                 return "#queue";
 115         case (SKF_AD_OFF + SKF_AD_HATYPE):
 116                 return "#hatype";
 117         case (SKF_AD_OFF + SKF_AD_RXHASH):
 118                 return "#rxhash";
 119         case (SKF_AD_OFF + SKF_AD_CPU):
 120                 return "#cpu";
 121         }
 122 }
 123
 124 static char *bpf_dump(const struct sock_filter bpf, int n)
 125 {
 126         int v;
 127         const char *fmt, *op;
 128         static char image[256];
 129         char operand[64];
 130
 131         v = bpf.k;
 132         switch (bpf.code) {
 133         default:
 134                 op = "unimp";
 135                 fmt = "0x%x";
 136                 v = bpf.code;
 137                 break;
 138         case BPF_RET | BPF_K:
 139                 op = op_table[BPF_RET];
 140                 fmt = "#0x%x";
 141                 break;
 142         case BPF_RET | BPF_A:
 143                 op = op_table[BPF_RET];
 144                 fmt = "";
 145                 break;
 146         case BPF_LD_W | BPF_ABS:
 147                 op = op_table[BPF_LD_W];
 148                 fmt = bpf_dump_linux_k(bpf.k);
 149                 break;
 150         case BPF_LD_H | BPF_ABS:
 151                 op = op_table[BPF_LD_H];
 152                 fmt = bpf_dump_linux_k(bpf.k);
 153                 break;
 154         case BPF_LD_B | BPF_ABS:
 155                 op = op_table[BPF_LD_B];
 156                 fmt = bpf_dump_linux_k(bpf.k);
 157                 break;
 158         case BPF_LD_W | BPF_LEN:
 159                 op = op_table[BPF_LD_W];
 160                 fmt = "#len";
 161                 break;
 162         case BPF_LD_W | BPF_IND:
 163                 op = op_table[BPF_LD_W];
 164                 fmt = "[x + %d]";
 165                 break;
 166         case BPF_LD_H | BPF_IND:
 167                 op = op_table[BPF_LD_H];
 168                 fmt = "[x + %d]";
 169                 break;
 170         case BPF_LD_B | BPF_IND:
 171                 op = op_table[BPF_LD_B];
 172                 fmt = "[x + %d]";
 173                 break;
 174         case BPF_LD | BPF_IMM:
 175                 op = op_table[BPF_LD_W];
 176                 fmt = "#0x%x";
 177                 break;
 178         case BPF_LDX | BPF_IMM:
 179                 op = op_table[BPF_LDX];
 180                 fmt = "#0x%x";
 181                 break;
 182         case BPF_LDX_B | BPF_MSH:
 183                 op = op_table[BPF_LDX_B];
 184                 fmt = "4*([%d]&0xf)";
 185                 break;
 186         case BPF_LD | BPF_MEM:
 187                 op = op_table[BPF_LD_W];
 188                 fmt = "M[%d]";
 189                 break;
 190         case BPF_LDX | BPF_MEM:
 191                 op = op_table[BPF_LDX];
 192                 fmt = "M[%d]";
 193                 break;
 194         case BPF_ST:
 195                 op = op_table[BPF_ST];
 196                 fmt = "M[%d]";
 197                 break;
 198         case BPF_STX:
 199                 op = op_table[BPF_STX];
 200                 fmt = "M[%d]";
 201                 break;
 202         case BPF_JMP_JA:
 203                 op = op_table[BPF_JMP_JA];
 204                 fmt = "%d";
 205                 v = n + 1 + bpf.k;
 206                 break;
 207         case BPF_JMP_JGT | BPF_K:
 208                 op = op_table[BPF_JMP_JGT];
 209                 fmt = "#0x%x";
 210                 break;
 211         case BPF_JMP_JGE | BPF_K:
 212                 op = op_table[BPF_JMP_JGE];
 213                 fmt = "#0x%x";
 214                 break;
 215         case BPF_JMP_JEQ | BPF_K:
 216                 op = op_table[BPF_JMP_JEQ];
 217                 fmt = "#0x%x";
 218                 break;
 219         case BPF_JMP_JSET | BPF_K:
 220                 op = op_table[BPF_JMP_JSET];
 221                 fmt = "#0x%x";
 222                 break;
 223         case BPF_JMP_JGT | BPF_X:
 224                 op = op_table[BPF_JMP_JGT];
 225                 fmt = "x";
 226                 break;
 227         case BPF_JMP_JGE | BPF_X:
 228                 op = op_table[BPF_JMP_JGE];
 229                 fmt = "x";
 230                 break;
 231         case BPF_JMP_JEQ | BPF_X:
 232                 op = op_table[BPF_JMP_JEQ];
 233                 fmt = "x";
 234                 break;
 235         case BPF_JMP_JSET | BPF_X:
 236                 op = op_table[BPF_JMP_JSET];
 237                 fmt = "x";
 238                 break;
 239         case BPF_ALU_ADD | BPF_X:
 240                 op = op_table[BPF_ALU_ADD];
 241                 fmt = "x";
 242                 break;
 243         case BPF_ALU_SUB | BPF_X:
 244                 op = op_table[BPF_ALU_SUB];
 245                 fmt = "x";
 246                 break;
 247         case BPF_ALU_MUL | BPF_X:
 248                 op = op_table[BPF_ALU_MUL];
 249                 fmt = "x";
 250                 break;
 251         case BPF_ALU_DIV | BPF_X:
 252                 op = op_table[BPF_ALU_DIV];
 253                 fmt = "x";
 254                 break;
 255         case BPF_ALU_MOD | BPF_X:
 256                 op = op_table[BPF_ALU_MOD];
 257                 fmt = "x";
 258                 break;
 259         case BPF_ALU_AND | BPF_X:
 260                 op = op_table[BPF_ALU_AND];
 261                 fmt = "x";
 262                 break;
 263         case BPF_ALU_OR | BPF_X:
 264                 op = op_table[BPF_ALU_OR];
 265                 fmt = "x";
 266                 break;
 267         case BPF_ALU_XOR | BPF_X:
 268                 op = op_table[BPF_ALU_XOR];
 269                 fmt = "x";
 270                 break;
 271         case BPF_ALU_LSH | BPF_X:
 272                 op = op_table[BPF_ALU_LSH];
 273                 fmt = "x";
 274                 break;
 275         case BPF_ALU_RSH | BPF_X:
 276                 op = op_table[BPF_ALU_RSH];
 277                 fmt = "x";
 278                 break;
 279         case BPF_ALU_ADD | BPF_K:
 280                 op = op_table[BPF_ALU_ADD];
 281                 fmt = "#%d";
 282                 break;
 283         case BPF_ALU_SUB | BPF_K:
 284                 op = op_table[BPF_ALU_SUB];
 285                 fmt = "#%d";
 286                 break;
 287         case BPF_ALU_MUL | BPF_K:
 288                 op = op_table[BPF_ALU_MUL];
 289                 fmt = "#%d";
 290                 break;
 291         case BPF_ALU_DIV | BPF_K:
 292                 op = op_table[BPF_ALU_DIV];
 293                 fmt = "#%d";
 294                 break;
 295         case BPF_ALU_MOD | BPF_K:
 296                 op = op_table[BPF_ALU_MOD];
 297                 fmt = "#%d";
 298                 break;
 299         case BPF_ALU_AND | BPF_K:
 300                 op = op_table[BPF_ALU_AND];
 301                 fmt = "#0x%x";
 302                 break;
 303         case BPF_ALU_OR | BPF_K:
 304                 op = op_table[BPF_ALU_OR];
 305                 fmt = "#0x%x";
 306                 break;
 307         case BPF_ALU_XOR | BPF_K:
 308                 op = op_table[BPF_ALU_XOR];
 309                 fmt = "#0x%x";
 310                 break;
 311         case BPF_ALU_LSH | BPF_K:
 312                 op = op_table[BPF_ALU_LSH];
 313                 fmt = "#%d";
 314                 break;
 315         case BPF_ALU_RSH | BPF_K:
 316                 op = op_table[BPF_ALU_RSH];
 317                 fmt = "#%d";
 318                 break;
 319         case BPF_ALU_NEG:
 320                 op = op_table[BPF_ALU_NEG];
 321                 fmt = "";
 322                 break;
 323         case BPF_MISC_TAX:
 324                 op = op_table[BPF_MISC_TAX];
 325                 fmt = "";
 326                 break;
 327         case BPF_MISC_TXA:
 328                 op = op_table[BPF_MISC_TXA];
 329                 fmt = "";
 330                 break;
 331         }
 332
 333         slprintf(operand, sizeof(operand), fmt, v);
 334         slprintf(image, sizeof(image),
 335                  (BPF_CLASS(bpf.code) == BPF_JMP &&
 336                   BPF_OP(bpf.code) != BPF_JA) ?
 337                  " L%d: %s %s, L%d, L%d" : " L%d: %s %s",
 338                  n, op, operand, n + 1 + bpf.jt, n + 1 + bpf.jf);
 339
 340         return image;
 341 }
 342
 343 void bpf_dump_all(struct sock_fprog *bpf)
 344 {
 345         int i;
 346         for (i = 0; i < bpf->len; ++i)
 347                 printf("%s\n", bpf_dump(bpf->filter[i], i));
 348 }
 349
 350 void bpf_attach_to_sock(int sock, struct sock_fprog *bpf)
 351 {
 352         int ret;
 353
 354         if (bpf->len == 1) {
 355                 if (bpf->filter[0].code == BPF_RET &&
 356                     bpf->filter[0].k == 0xFFFFFFFF)
 357                         return;
 358         }
 359
 360         ret = setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
 361                          bpf, sizeof(*bpf));
 362         if (ret < 0)
 363                 panic("Cannot attach filter to socket!\n");
 364 }
 365
 366 void bpf_detach_from_sock(int sock)
 367 {
 368         int ret, empty = 0;
 369
 370         ret = setsockopt(sock, SOL_SOCKET, SO_DETACH_FILTER,
 371                          &empty, sizeof(empty));
 372         if (ret < 0)
 373                 panic("Cannot detach filter from socket!\n");
 374 }
 375
 376 void enable_kernel_bpf_jit_compiler(void)
 377 {
 378         int fd;
 379         ssize_t ret;
 380         char *file = "/proc/sys/net/core/bpf_jit_enable";
 381
 382         fd = open(file, O_WRONLY);
 383         if (fd < 0)
 384                 return;
 385
 386         ret = write(fd, "1", strlen("1"));
 387         if (ret > 0)
 388                 printf("BPF JIT\n");
 389
 390         close(fd);
 391 }
 392
 393 int bpf_validate(const struct sock_fprog *bpf)
 394 {
 395         uint32_t i, from;
 396         const struct sock_filter *p;
 397
 398         if (!bpf)
 399                 return 0;
 400         if (bpf->len < 1)
 401                 return 0;
 402
 403         for (i = 0; i < bpf->len; ++i) {
 404                 p = &bpf->filter[i];
 405                 switch (BPF_CLASS(p->code)) {
 406                         /* Check that memory operations use valid addresses. */
 407                 case BPF_LD:
 408                 case BPF_LDX:
 409                         switch (BPF_MODE(p->code)) {
 410                         case BPF_IMM:
 411                                 break;
 412                         case BPF_ABS:
 413                         case BPF_IND:
 414                         case BPF_MSH:
 415                                 /* There's no maximum packet data size
 416                                  * in userland.  The runtime packet length
 417                                  * check suffices.
 418                                  */
 419                                 break;
 420                         case BPF_MEM:
 421                                 if (p->k >= BPF_MEMWORDS)
 422                                         return 0;
 423                                 break;
 424                         case BPF_LEN:
 425                                 break;
 426                         default:
 427                                 return 0;
 428                         }
 429                         break;
 430                 case BPF_ST:
 431                 case BPF_STX:
 432                         if (p->k >= BPF_MEMWORDS)
 433                                 return 0;
 434                         break;
 435                 case BPF_ALU:
 436                         switch (BPF_OP(p->code)) {
 437                         case BPF_ADD:
 438                         case BPF_SUB:
 439                         case BPF_MUL:
 440                         case BPF_OR:
 441                         case BPF_XOR:
 442                         case BPF_AND:
 443                         case BPF_LSH:
 444                         case BPF_RSH:
 445                         case BPF_NEG:
 446                                 break;
 447                         case BPF_DIV:
 448                         case BPF_MOD:
 449                                 /* Check for constant division by 0 (undefined
 450                                  * for div and mod).
 451                                  */
 452                                 if (BPF_RVAL(p->code) == BPF_K && p->k == 0)
 453                                         return 0;
 454                                 break;
 455                         default:
 456                                 return 0;
 457                         }
 458                         break;
 459                 case BPF_JMP:
 460                         /* Check that jumps are within the code block,
 461                          * and that unconditional branches don't go
 462                          * backwards as a result of an overflow.
 463                          * Unconditional branches have a 32-bit offset,
 464                          * so they could overflow; we check to make
 465                          * sure they don't.  Conditional branches have
 466                          * an 8-bit offset, and the from address is <=
 467                          * BPF_MAXINSNS, and we assume that BPF_MAXINSNS
 468                          * is sufficiently small that adding 255 to it
 469                          * won't overflow.
 470                          *
 471                          * We know that len is <= BPF_MAXINSNS, and we
 472                          * assume that BPF_MAXINSNS is < the maximum size
 473                          * of a u_int, so that i + 1 doesn't overflow.
 474                          *
 475                          * For userland, we don't know that the from
 476                          * or len are <= BPF_MAXINSNS, but we know that
 477                          * from <= len, and, except on a 64-bit system,
 478                          * it's unlikely that len, if it truly reflects
 479                          * the size of the program we've been handed,
 480                          * will be anywhere near the maximum size of
 481                          * a u_int.  We also don't check for backward
 482                          * branches, as we currently support them in
 483                          * userland for the protochain operation.
 484                          */
 485                         from = i + 1;
 486                         switch (BPF_OP(p->code)) {
 487                         case BPF_JA:
 488                                 if (from + p->k >= bpf->len)
 489                                         return 0;
 490                                 break;
 491                         case BPF_JEQ:
 492                         case BPF_JGT:
 493                         case BPF_JGE:
 494                         case BPF_JSET:
 495                                 if (from + p->jt >= bpf->len ||
 496                                     from + p->jf >= bpf->len)
 497                                         return 0;
 498                                 break;
 499                         default:
 500                                 return 0;
 501                         }
 502                         break;
 503                 case BPF_RET:
 504                         break;
 505                 case BPF_MISC:
 506                         break;
 507                 default:
 508                         return 0;
 509                 }
 510         }
 511
 512         return BPF_CLASS(bpf->filter[bpf->len - 1].code) == BPF_RET;
 513 }
 514
 515 uint32_t bpf_run_filter(const struct sock_fprog * fcode, uint8_t * packet,
 516                         size_t plen)
 517 {
 518         /* XXX: caplen == len */
 519         uint32_t A, X;
 520         uint32_t k;
 521         struct sock_filter *bpf;
 522         int32_t mem[BPF_MEMWORDS];
 523
 524         if (fcode == NULL || fcode->filter == NULL || fcode->len == 0)
 525                 return 0xFFFFFFFF;
 526
 527         A = 0;
 528         X = 0;
 529
 530         bpf = fcode->filter;
 531         --bpf;
 532         while (1) {
 533                 ++bpf;
 534                 switch (bpf->code) {
 535                 default:
 536                         return 0;
 537                 case BPF_RET | BPF_K:
 538                         return (uint32_t) bpf->k;
 539                 case BPF_RET | BPF_A:
 540                         return (uint32_t) A;
 541                 case BPF_LD_W | BPF_ABS:
 542                         /* No Linux extensions supported here! */
 543                         k = bpf->k;
 544                         if (k + sizeof(int32_t) > plen)
 545                                 return 0;
 546                         A = EXTRACT_LONG(&packet[k]);
 547                         continue;
 548                 case BPF_LD_H | BPF_ABS:
 549                         /* No Linux extensions supported here! */
 550                         k = bpf->k;
 551                         if (k + sizeof(short) > plen)
 552                                 return 0;
 553                         A = EXTRACT_SHORT(&packet[k]);
 554                         continue;
 555                 case BPF_LD_B | BPF_ABS:
 556                         /* No Linux extensions supported here! */
 557                         k = bpf->k;
 558                         if (k >= plen)
 559                                 return 0;
 560                         A = packet[k];
 561                         continue;
 562                 case BPF_LD_W | BPF_LEN:
 563                         A = plen;
 564                         continue;
 565                 case BPF_LDX_W | BPF_LEN:
 566                         X = plen;
 567                         continue;
 568                 case BPF_LD_W | BPF_IND:
 569                         k = X + bpf->k;
 570                         if (k + sizeof(int32_t) > plen)
 571                                 return 0;
 572                         A = EXTRACT_LONG(&packet[k]);
 573                         continue;
 574                 case BPF_LD_H | BPF_IND:
 575                         k = X + bpf->k;
 576                         if (k + sizeof(short) > plen)
 577                                 return 0;
 578                         A = EXTRACT_SHORT(&packet[k]);
 579                         continue;
 580                 case BPF_LD_B | BPF_IND:
 581                         k = X + bpf->k;
 582                         if (k >= plen)
 583                                 return 0;
 584                         A = packet[k];
 585                         continue;
 586                 case BPF_LDX_B | BPF_MSH:
 587                         k = bpf->k;
 588                         if (k >= plen)
 589                                 return 0;
 590                         X = (packet[bpf->k] & 0xf) << 2;
 591                         continue;
 592                 case BPF_LD | BPF_IMM:
 593                         A = bpf->k;
 594                         continue;
 595                 case BPF_LDX | BPF_IMM:
 596                         X = bpf->k;
 597                         continue;
 598                 case BPF_LD | BPF_MEM:
 599                         A = mem[bpf->k];
 600                         continue;
 601                 case BPF_LDX | BPF_MEM:
 602                         X = mem[bpf->k];
 603                         continue;
 604                 case BPF_ST:
 605                         mem[bpf->k] = A;
 606                         continue;
 607                 case BPF_STX:
 608                         mem[bpf->k] = X;
 609                         continue;
 610                 case BPF_JMP_JA:
 611                         bpf += bpf->k;
 612                         continue;
 613                 case BPF_JMP_JGT | BPF_K:
 614                         bpf += (A > bpf->k) ? bpf->jt : bpf->jf;
 615                         continue;
 616                 case BPF_JMP_JGE | BPF_K:
 617                         bpf += (A >= bpf->k) ? bpf->jt : bpf->jf;
 618                         continue;
 619                 case BPF_JMP_JEQ | BPF_K:
 620                         bpf += (A == bpf->k) ? bpf->jt : bpf->jf;
 621                         continue;
 622                 case BPF_JMP_JSET | BPF_K:
 623                         bpf += (A & bpf->k) ? bpf->jt : bpf->jf;
 624                         continue;
 625                 case BPF_JMP_JGT | BPF_X:
 626                         bpf += (A > X) ? bpf->jt : bpf->jf;
 627                         continue;
 628                 case BPF_JMP_JGE | BPF_X:
 629                         bpf += (A >= X) ? bpf->jt : bpf->jf;
 630                         continue;
 631                 case BPF_JMP_JEQ | BPF_X:
 632                         bpf += (A == X) ? bpf->jt : bpf->jf;
 633                         continue;
 634                 case BPF_JMP_JSET | BPF_X:
 635                         bpf += (A & X) ? bpf->jt : bpf->jf;
 636                         continue;
 637                 case BPF_ALU_ADD | BPF_X:
 638                         A += X;
 639                         continue;
 640                 case BPF_ALU_SUB | BPF_X:
 641                         A -= X;
 642                         continue;
 643                 case BPF_ALU_MUL | BPF_X:
 644                         A *= X;
 645                         continue;
 646                 case BPF_ALU_DIV | BPF_X:
 647                         if (X == 0)
 648                                 return 0;
 649                         A /= X;
 650                         continue;
 651                 case BPF_ALU_MOD | BPF_X:
 652                         if (X == 0)
 653                                 return 0;
 654                         A %= X;
 655                         continue;
 656                 case BPF_ALU_AND | BPF_X:
 657                         A &= X;
 658                         continue;
 659                 case BPF_ALU_OR | BPF_X:
 660                         A |= X;
 661                         continue;
 662                 case BPF_ALU_XOR | BPF_X:
 663                         A ^= X;
 664                         continue;
 665                 case BPF_ALU_LSH | BPF_X:
 666                         A <<= X;
 667                         continue;
 668                 case BPF_ALU_RSH | BPF_X:
 669                         A >>= X;
 670                         continue;
 671                 case BPF_ALU_ADD | BPF_K:
 672                         A += bpf->k;
 673                         continue;
 674                 case BPF_ALU_SUB | BPF_K:
 675                         A -= bpf->k;
 676                         continue;
 677                 case BPF_ALU_MUL | BPF_K:
 678                         A *= bpf->k;
 679                         continue;
 680                 case BPF_ALU_DIV | BPF_K:
 681                         A /= bpf->k;
 682                         continue;
 683                 case BPF_ALU_MOD | BPF_K:
 684                         A %= bpf->k;
 685                         continue;
 686                 case BPF_ALU_AND | BPF_K:
 687                         A &= bpf->k;
 688                         continue;
 689                 case BPF_ALU_OR | BPF_K:
 690                         A |= bpf->k;
 691                         continue;
 692                 case BPF_ALU_XOR | BPF_K:
 693                         A ^= bpf->k;
 694                         continue;
 695                 case BPF_ALU_LSH | BPF_K:
 696                         A <<= bpf->k;
 697                         continue;
 698                 case BPF_ALU_RSH | BPF_K:
 699                         A >>= bpf->k;
 700                         continue;
 701                 case BPF_ALU_NEG:
 702                         A = -A;
 703                         continue;
 704                 case BPF_MISC_TAX:
 705                         X = A;
 706                         continue;
 707                 case BPF_MISC_TXA:
 708                         A = X;
 709                         continue;
 710                 }
 711         }
 712 }
 713
 714 void bpf_parse_rules(char *rulefile, struct sock_fprog *bpf)
 715 {
 716         int ret;
 717         char buff[256];
 718         struct sock_filter sf_single = { 0x06, 0, 0, 0xFFFFFFFF };
 719         FILE *fp;
 720
 721         if (rulefile == NULL) {
 722                 bpf->len = 1;
 723                 bpf->filter = xmalloc(sizeof(sf_single));
 724                 fmemcpy(&bpf->filter[0], &sf_single, sizeof(sf_single));
 725                 return;
 726         }
 727
 728         fp = fopen(rulefile, "r");
 729         if (!fp)
 730                 panic("Cannot read BPF rule file!\n");
 731
 732         fmemset(buff, 0, sizeof(buff));
 733         while (fgets(buff, sizeof(buff), fp) != NULL) {
 734                 buff[sizeof(buff) - 1] = 0;
 735                 if (buff[0] != '{') {
 736                         fmemset(buff, 0, sizeof(buff));
 737                         continue;
 738                 }
 739
 740                 fmemset(&sf_single, 0, sizeof(sf_single));
 741                 ret = sscanf(buff, "{ 0x%x, %u, %u, 0x%08x },",
 742                              (unsigned int *) &sf_single.code,
 743                              (unsigned int *) &sf_single.jt,
 744                              (unsigned int *) &sf_single.jf,
 745                              (unsigned int *) &sf_single.k);
 746                 if (ret != 4)
 747                         panic("BPF syntax error!\n");
 748
 749                 bpf->len++;
 750                 bpf->filter = xrealloc(bpf->filter, 1,
 751                                        bpf->len * sizeof(sf_single));
 752
 753                 fmemcpy(&bpf->filter[bpf->len - 1], &sf_single,
 754                        sizeof(sf_single));
 755                 fmemset(buff, 0, sizeof(buff));
 756         }
 757
 758         fclose(fp);
 759
 760         if (bpf_validate(bpf) == 0)
 761                 panic("This is not a valid BPF program!\n");
 762 }