Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
tjh.dev
kernel
os
linux
1/* eBPF example program:
2 *
3 * - Creates arraymap in kernel with 4 bytes keys and 8 byte values
4 *
5 * - Loads eBPF program
6 *
7 * The eBPF program accesses the map passed in to store two pieces of
8 * information. The number of invocations of the program, which maps
9 * to the number of packets received, is stored to key 0. Key 1 is
10 * incremented on each iteration by the number of bytes stored in
11 * the skb.
12 *
13 * - Attaches the new program to a cgroup using BPF_PROG_ATTACH
14 *
15 * - Every second, reads map[0] and map[1] to see how many bytes and
16 * packets were seen on any socket of tasks in the given cgroup.
17 */
18
19#define _GNU_SOURCE
20
21#include <stdio.h>
22#include <stdlib.h>
23#include <stddef.h>
24#include <string.h>
25#include <unistd.h>
26#include <assert.h>
27#include <errno.h>
28#include <fcntl.h>
29
30#include <linux/bpf.h>
31#include <bpf/bpf.h>
32
33#include "bpf_insn.h"
34
35enum {
36 MAP_KEY_PACKETS,
37 MAP_KEY_BYTES,
38};
39
40char bpf_log_buf[BPF_LOG_BUF_SIZE];
41
42static int prog_load(int map_fd, int verdict)
43{
44 struct bpf_insn prog[] = {
45 BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* save r6 so it's not clobbered by BPF_CALL */
46
47 /* Count packets */
48 BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */
49 BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
50 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
51 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
52 BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* load map fd to r1 */
53 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
54 BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
55 BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
56 BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
57
58 /* Count bytes */
59 BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */
60 BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
61 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
62 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
63 BPF_LD_MAP_FD(BPF_REG_1, map_fd),
64 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
65 BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
66 BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */
67
68 BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
69
70 BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */
71 BPF_EXIT_INSN(),
72 };
73 size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
74 LIBBPF_OPTS(bpf_prog_load_opts, opts,
75 .log_buf = bpf_log_buf,
76 .log_size = BPF_LOG_BUF_SIZE,
77 );
78
79 return bpf_prog_load(BPF_PROG_TYPE_CGROUP_SKB, NULL, "GPL",
80 prog, insns_cnt, &opts);
81}
82
83static int usage(const char *argv0)
84{
85 printf("Usage: %s [-d] [-D] <cg-path> <egress|ingress>\n", argv0);
86 printf(" -d Drop Traffic\n");
87 printf(" -D Detach filter, and exit\n");
88 return EXIT_FAILURE;
89}
90
91static int attach_filter(int cg_fd, int type, int verdict)
92{
93 int prog_fd, map_fd, ret, key;
94 long long pkt_cnt, byte_cnt;
95
96 map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL,
97 sizeof(key), sizeof(byte_cnt),
98 256, NULL);
99 if (map_fd < 0) {
100 printf("Failed to create map: '%s'\n", strerror(errno));
101 return EXIT_FAILURE;
102 }
103
104 prog_fd = prog_load(map_fd, verdict);
105 printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);
106
107 if (prog_fd < 0) {
108 printf("Failed to load prog: '%s'\n", strerror(errno));
109 return EXIT_FAILURE;
110 }
111
112 ret = bpf_prog_attach(prog_fd, cg_fd, type, 0);
113 if (ret < 0) {
114 printf("Failed to attach prog to cgroup: '%s'\n",
115 strerror(errno));
116 return EXIT_FAILURE;
117 }
118 while (1) {
119 key = MAP_KEY_PACKETS;
120 assert(bpf_map_lookup_elem(map_fd, &key, &pkt_cnt) == 0);
121
122 key = MAP_KEY_BYTES;
123 assert(bpf_map_lookup_elem(map_fd, &key, &byte_cnt) == 0);
124
125 printf("cgroup received %lld packets, %lld bytes\n",
126 pkt_cnt, byte_cnt);
127 sleep(1);
128 }
129
130 return EXIT_SUCCESS;
131}
132
133int main(int argc, char **argv)
134{
135 int detach_only = 0, verdict = 1;
136 enum bpf_attach_type type;
137 int opt, cg_fd, ret;
138
139 while ((opt = getopt(argc, argv, "Dd")) != -1) {
140 switch (opt) {
141 case 'd':
142 verdict = 0;
143 break;
144 case 'D':
145 detach_only = 1;
146 break;
147 default:
148 return usage(argv[0]);
149 }
150 }
151
152 if (argc - optind < 2)
153 return usage(argv[0]);
154
155 if (strcmp(argv[optind + 1], "ingress") == 0)
156 type = BPF_CGROUP_INET_INGRESS;
157 else if (strcmp(argv[optind + 1], "egress") == 0)
158 type = BPF_CGROUP_INET_EGRESS;
159 else
160 return usage(argv[0]);
161
162 cg_fd = open(argv[optind], O_DIRECTORY | O_RDONLY);
163 if (cg_fd < 0) {
164 printf("Failed to open cgroup path: '%s'\n", strerror(errno));
165 return EXIT_FAILURE;
166 }
167
168 if (detach_only) {
169 ret = bpf_prog_detach(cg_fd, type);
170 printf("bpf_prog_detach() returned '%s' (%d)\n",
171 strerror(errno), errno);
172 } else
173 ret = attach_filter(cg_fd, type, verdict);
174
175 return ret;
176}