VBLADE/vblade-master/bpf.c

   1 // bpf.c: bpf packet filter for linux/freebsd
   2
   3 #include "config.h"
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <sys/types.h>
   8 #include "dat.h"
   9 #include "fns.h"
  10
  11 struct bpf_insn {
  12         ushort code;
  13         uchar jt;
  14         uchar jf;
  15         u_int32_t k;
  16 };
  17
  18 struct bpf_program {
  19         uint bf_len;
  20         struct bpf_insn *bf_insns;
  21 };
  22
  23 /* instruction classes */
  24 #define         BPF_CLASS(code) ((code) & 0x07)
  25 #define         BPF_LD          0x00
  26 #define         BPF_LDX         0x01
  27 #define         BPF_ST          0x02
  28 #define         BPF_STX         0x03
  29 #define         BPF_ALU         0x04
  30 #define         BPF_JMP         0x05
  31 #define         BPF_RET         0x06
  32 #define         BPF_MISC        0x07
  33
  34 /* ld/ldx fields */
  35 #define         BPF_SIZE(code)  ((code) & 0x18)
  36 #define         BPF_W           0x00
  37 #define         BPF_H           0x08
  38 #define         BPF_B           0x10
  39 #define         BPF_MODE(code)  ((code) & 0xe0)
  40 #define         BPF_IMM         0x00
  41 #define         BPF_ABS         0x20
  42 #define         BPF_IND         0x40
  43 #define         BPF_MEM         0x60
  44 #define         BPF_LEN         0x80
  45 #define         BPF_MSH         0xa0
  46
  47 /* alu/jmp fields */
  48 #define         BPF_OP(code)    ((code) & 0xf0)
  49 #define         BPF_ADD         0x00
  50 #define         BPF_SUB         0x10
  51 #define         BPF_MUL         0x20
  52 #define         BPF_DIV         0x30
  53 #define         BPF_OR          0x40
  54 #define         BPF_AND         0x50
  55 #define         BPF_LSH         0x60
  56 #define         BPF_RSH         0x70
  57 #define         BPF_NEG         0x80
  58 #define         BPF_JA          0x00
  59 #define         BPF_JEQ         0x10
  60 #define         BPF_JGT         0x20
  61 #define         BPF_JGE         0x30
  62 #define         BPF_JSET        0x40
  63 #define         BPF_SRC(code)   ((code) & 0x08)
  64 #define         BPF_K           0x00
  65 #define         BPF_X           0x08
  66
  67 /* ret - BPF_K and BPF_X also apply */
  68 #define         BPF_RVAL(code)  ((code) & 0x18)
  69 #define         BPF_A           0x10
  70
  71 /* misc */
  72 #define         BPF_MISCOP(code) ((code) & 0xf8)
  73 #define         BPF_TAX         0x00
  74 #define         BPF_TXA         0x80
  75
  76 /* macros for insn array initializers */
  77 #define BPF_STMT(code, k) { (ushort)(code), 0, 0, k }
  78 #define BPF_JUMP(code, k, jt, jf) { (ushort)(code), jt, jf, k }
  79
  80 void *
  81 create_bpf_program(int shelf, int slot)
  82 {
  83         struct bpf_program *bpf_program;
  84         struct bpf_insn insns[] = {
  85                 /* CHECKTYPE: Load the type into register */
  86                 BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 12),
  87                 /* Does it match AoE Type (0x88a2)? No, goto INVALID */
  88                 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0x88a2, 0, 10),
  89                 /* Load the flags into register */
  90                 BPF_STMT(BPF_LD+BPF_B+BPF_ABS, 14),
  91                 /* Check to see if the Resp flag is set */
  92                 BPF_STMT(BPF_ALU+BPF_AND+BPF_K, Resp),
  93                 /* Yes, goto INVALID */
  94                 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 7),
  95                 /* CHECKSHELF: Load the shelf number into register */
  96                 BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 16),
  97                 /* Does it match shelf number? Yes, goto CHECKSLOT */
  98                 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, shelf, 1, 0),
  99                 /* Does it match broadcast? No, goto INVALID */
 100                 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0xffff, 0, 4),
 101                 /* CHECKSLOT: Load the slot number into register */
 102                 BPF_STMT(BPF_LD+BPF_B+BPF_ABS, 18),
 103                 /* Does it match shelf number? Yes, goto VALID */
 104                 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, slot, 1, 0),
 105                 /* Does it match broadcast? No, goto INVALID */
 106                 BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0xff, 0, 1),
 107                 /* VALID: return -1 (allow the packet to be read) */
 108                 BPF_STMT(BPF_RET+BPF_K, -1),
 109                 /* INVALID: return 0 (ignore the packet) */
 110                 BPF_STMT(BPF_RET+BPF_K, 0),
 111         };
 112         if ((bpf_program = malloc(sizeof(struct bpf_program))) == NULL
 113             || (bpf_program->bf_insns = malloc(sizeof(insns))) == NULL) {
 114                 perror("malloc");
 115                 exit(1);
 116         }
 117         bpf_program->bf_len = sizeof(insns)/sizeof(struct bpf_insn);
 118         memcpy(bpf_program->bf_insns, insns, sizeof(insns));
 119         return (void *)bpf_program;
 120 }
 121
 122 void
 123 free_bpf_program(void *bpf_program)
 124 {
 125         free(((struct bpf_program *) bpf_program)->bf_insns);
 126         free(bpf_program);
 127 }