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
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
/* eBPF example program:
*
* - Creates arraymap in kernel with 4 bytes keys and 8 byte values
*
* - Loads eBPF program
*
* The eBPF program accesses the map passed in to store two pieces of
* information. The number of invocations of the program, which maps
* to the number of packets received, is stored to key 0. Key 1 is
* incremented on each iteration by the number of bytes stored in
* the skb.
*
* - Attaches the new program to a cgroup using BPF_PROG_ATTACH
*
* - Every second, reads map[0] and map[1] to see how many bytes and
* packets were seen on any socket of tasks in the given cgroup.
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <string.h>
#include <unistd.h>
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <linux/bpf.h>
#include <bpf/bpf.h>
#include "bpf_insn.h"
#include "bpf_util.h"
enum {
MAP_KEY_PACKETS,
MAP_KEY_BYTES,
};
char bpf_log_buf[BPF_LOG_BUF_SIZE];
static int prog_load(int map_fd, int verdict)
{
struct bpf_insn prog[] = {
BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* save r6 so it's not clobbered by BPF_CALL */
/* Count packets */
BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */
BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* load map fd to r1 */
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
/* Count bytes */
BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */
BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
BPF_LD_MAP_FD(BPF_REG_1, map_fd),
BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */
BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */
BPF_EXIT_INSN(),
};
size_t insns_cnt = ARRAY_SIZE(prog);
LIBBPF_OPTS(bpf_prog_load_opts, opts,
.log_buf = bpf_log_buf,
.log_size = BPF_LOG_BUF_SIZE,
);
return bpf_prog_load(BPF_PROG_TYPE_CGROUP_SKB, NULL, "GPL",
prog, insns_cnt, &opts);
}
static int usage(const char *argv0)
{
printf("Usage: %s [-d] [-D] <cg-path> <egress|ingress>\n", argv0);
printf(" -d Drop Traffic\n");
printf(" -D Detach filter, and exit\n");
return EXIT_FAILURE;
}
static int attach_filter(int cg_fd, int type, int verdict)
{
int prog_fd, map_fd, ret, key;
long long pkt_cnt, byte_cnt;
map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL,
sizeof(key), sizeof(byte_cnt),
256, NULL);
if (map_fd < 0) {
printf("Failed to create map: '%s'\n", strerror(errno));
return EXIT_FAILURE;
}
prog_fd = prog_load(map_fd, verdict);
printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);
if (prog_fd < 0) {
printf("Failed to load prog: '%s'\n", strerror(errno));
return EXIT_FAILURE;
}
ret = bpf_prog_attach(prog_fd, cg_fd, type, 0);
if (ret < 0) {
printf("Failed to attach prog to cgroup: '%s'\n",
strerror(errno));
return EXIT_FAILURE;
}
while (1) {
key = MAP_KEY_PACKETS;
assert(bpf_map_lookup_elem(map_fd, &key, &pkt_cnt) == 0);
key = MAP_KEY_BYTES;
assert(bpf_map_lookup_elem(map_fd, &key, &byte_cnt) == 0);
printf("cgroup received %lld packets, %lld bytes\n",
pkt_cnt, byte_cnt);
sleep(1);
}
return EXIT_SUCCESS;
}
int main(int argc, char **argv)
{
int detach_only = 0, verdict = 1;
enum bpf_attach_type type;
int opt, cg_fd, ret;
while ((opt = getopt(argc, argv, "Dd")) != -1) {
switch (opt) {
case 'd':
verdict = 0;
break;
case 'D':
detach_only = 1;
break;
default:
return usage(argv[0]);
}
}
if (argc - optind < 2)
return usage(argv[0]);
if (strcmp(argv[optind + 1], "ingress") == 0)
type = BPF_CGROUP_INET_INGRESS;
else if (strcmp(argv[optind + 1], "egress") == 0)
type = BPF_CGROUP_INET_EGRESS;
else
return usage(argv[0]);
cg_fd = open(argv[optind], O_DIRECTORY | O_RDONLY);
if (cg_fd < 0) {
printf("Failed to open cgroup path: '%s'\n", strerror(errno));
return EXIT_FAILURE;
}
if (detach_only) {
ret = bpf_prog_detach(cg_fd, type);
printf("bpf_prog_detach() returned '%s' (%d)\n",
strerror(errno), errno);
} else
ret = attach_filter(cg_fd, type, verdict);
return ret;
}
|
