1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
|
// bpf.c: bpf packet filter for linux/freebsd
#include "config.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include "dat.h"
#include "fns.h"
struct bpf_insn {
ushort code;
uchar jt;
uchar jf;
u_int32_t k;
};
struct bpf_program {
uint bf_len;
struct bpf_insn *bf_insns;
};
/* instruction classes */
#define BPF_CLASS(code) ((code) & 0x07)
#define BPF_LD 0x00
#define BPF_LDX 0x01
#define BPF_ST 0x02
#define BPF_STX 0x03
#define BPF_ALU 0x04
#define BPF_JMP 0x05
#define BPF_RET 0x06
#define BPF_MISC 0x07
/* ld/ldx fields */
#define BPF_SIZE(code) ((code) & 0x18)
#define BPF_W 0x00
#define BPF_H 0x08
#define BPF_B 0x10
#define BPF_MODE(code) ((code) & 0xe0)
#define BPF_IMM 0x00
#define BPF_ABS 0x20
#define BPF_IND 0x40
#define BPF_MEM 0x60
#define BPF_LEN 0x80
#define BPF_MSH 0xa0
/* alu/jmp fields */
#define BPF_OP(code) ((code) & 0xf0)
#define BPF_ADD 0x00
#define BPF_SUB 0x10
#define BPF_MUL 0x20
#define BPF_DIV 0x30
#define BPF_OR 0x40
#define BPF_AND 0x50
#define BPF_LSH 0x60
#define BPF_RSH 0x70
#define BPF_NEG 0x80
#define BPF_JA 0x00
#define BPF_JEQ 0x10
#define BPF_JGT 0x20
#define BPF_JGE 0x30
#define BPF_JSET 0x40
#define BPF_SRC(code) ((code) & 0x08)
#define BPF_K 0x00
#define BPF_X 0x08
/* ret - BPF_K and BPF_X also apply */
#define BPF_RVAL(code) ((code) & 0x18)
#define BPF_A 0x10
/* misc */
#define BPF_MISCOP(code) ((code) & 0xf8)
#define BPF_TAX 0x00
#define BPF_TXA 0x80
/* macros for insn array initializers */
#define BPF_STMT(code, k) { (ushort)(code), 0, 0, k }
#define BPF_JUMP(code, k, jt, jf) { (ushort)(code), jt, jf, k }
void *
create_bpf_program(int shelf, int slot)
{
struct bpf_program *bpf_program;
struct bpf_insn insns[] = {
/* Load the type into register */
BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 12),
/* Does it match AoE Type (0x88a2)? No, goto INVALID */
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0x88a2, 0, 12),
/* Load the flags into register */
BPF_STMT(BPF_LD+BPF_B+BPF_ABS, 14),
/* Check to see if the Resp flag is set */
BPF_STMT(BPF_ALU+BPF_AND+BPF_K, Resp),
/* Yes, goto INVALID */
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 9),
/* Load the shelf number into register */
BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 16),
/* Does it match shelf number? No, goto CHECKBROADCAST */
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, shelf, 0, 2),
/* Load the slot number into register */
BPF_STMT(BPF_LD+BPF_B+BPF_ABS, 18),
/* Does it match shelf number? Yes, goto VALID */
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, slot, 4, 0),
/* CHECKBROADCAST: is (shelf, slot) == (0xffff, 0xff)? */
/* Load the shelf number into register */
BPF_STMT(BPF_LD+BPF_H+BPF_ABS, 16),
/* Is it 0xffff? No, goto INVALID */
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0xffff, 0, 3),
/* Load the slot number into register */
BPF_STMT(BPF_LD+BPF_B+BPF_ABS, 18),
/* Is it 0xff? No, goto INVALID */
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0xff, 0, 1),
/* VALID: return -1 (allow the packet to be read) */
BPF_STMT(BPF_RET+BPF_K, -1),
/* INVALID: return 0 (ignore the packet) */
BPF_STMT(BPF_RET+BPF_K, 0),
};
if ((bpf_program = malloc(sizeof(struct bpf_program))) == NULL
|| (bpf_program->bf_insns = malloc(sizeof(insns))) == NULL) {
perror("malloc");
exit(1);
}
bpf_program->bf_len = sizeof(insns)/sizeof(struct bpf_insn);
memcpy(bpf_program->bf_insns, insns, sizeof(insns));
return (void *)bpf_program;
}
void
free_bpf_program(void *bpf_program)
{
free(((struct bpf_program *) bpf_program)->bf_insns);
free(bpf_program);
}
|
