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#include "bpf_util.h"
35
36enum {
37	MAP_KEY_PACKETS,
38	MAP_KEY_BYTES,
39};
40
41char bpf_log_buf[BPF_LOG_BUF_SIZE];
42
43static int prog_load(int map_fd, int verdict)
44{
45	struct bpf_insn prog[] = {
46		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* save r6 so it's not clobbered by BPF_CALL */
47
48		/* Count packets */
49		BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */
50		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
51		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
52		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
53		BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* load map fd to r1 */
54		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
55		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
56		BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
57		BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
58
59		/* Count bytes */
60		BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */
61		BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
62		BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
63		BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
64		BPF_LD_MAP_FD(BPF_REG_1, map_fd),
65		BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
66		BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
67		BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */
68
69		BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
70
71		BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */
72		BPF_EXIT_INSN(),
73	};
74	size_t insns_cnt = ARRAY_SIZE(prog);
75	LIBBPF_OPTS(bpf_prog_load_opts, opts,
76		.log_buf = bpf_log_buf,
77		.log_size = BPF_LOG_BUF_SIZE,
78	);
79
80	return bpf_prog_load(BPF_PROG_TYPE_CGROUP_SKB, NULL, "GPL",
81			     prog, insns_cnt, &opts);
82}
83
84static int usage(const char *argv0)
85{
86	printf("Usage: %s [-d] [-D] <cg-path> <egress|ingress>\n", argv0);
87	printf("	-d	Drop Traffic\n");
88	printf("	-D	Detach filter, and exit\n");
89	return EXIT_FAILURE;
90}
91
92static int attach_filter(int cg_fd, int type, int verdict)
93{
94	int prog_fd, map_fd, ret, key;
95	long long pkt_cnt, byte_cnt;
96
97	map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL,
98				sizeof(key), sizeof(byte_cnt),
99				256, NULL);
100	if (map_fd < 0) {
101		printf("Failed to create map: '%s'\n", strerror(errno));
102		return EXIT_FAILURE;
103	}
104
105	prog_fd = prog_load(map_fd, verdict);
106	printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);
107
108	if (prog_fd < 0) {
109		printf("Failed to load prog: '%s'\n", strerror(errno));
110		return EXIT_FAILURE;
111	}
112
113	ret = bpf_prog_attach(prog_fd, cg_fd, type, 0);
114	if (ret < 0) {
115		printf("Failed to attach prog to cgroup: '%s'\n",
116		       strerror(errno));
117		return EXIT_FAILURE;
118	}
119	while (1) {
120		key = MAP_KEY_PACKETS;
121		assert(bpf_map_lookup_elem(map_fd, &key, &pkt_cnt) == 0);
122
123		key = MAP_KEY_BYTES;
124		assert(bpf_map_lookup_elem(map_fd, &key, &byte_cnt) == 0);
125
126		printf("cgroup received %lld packets, %lld bytes\n",
127		       pkt_cnt, byte_cnt);
128		sleep(1);
129	}
130
131	return EXIT_SUCCESS;
132}
133
134int main(int argc, char **argv)
135{
136	int detach_only = 0, verdict = 1;
137	enum bpf_attach_type type;
138	int opt, cg_fd, ret;
139
140	while ((opt = getopt(argc, argv, "Dd")) != -1) {
141		switch (opt) {
142		case 'd':
143			verdict = 0;
144			break;
145		case 'D':
146			detach_only = 1;
147			break;
148		default:
149			return usage(argv[0]);
150		}
151	}
152
153	if (argc - optind < 2)
154		return usage(argv[0]);
155
156	if (strcmp(argv[optind + 1], "ingress") == 0)
157		type = BPF_CGROUP_INET_INGRESS;
158	else if (strcmp(argv[optind + 1], "egress") == 0)
159		type = BPF_CGROUP_INET_EGRESS;
160	else
161		return usage(argv[0]);
162
163	cg_fd = open(argv[optind], O_DIRECTORY | O_RDONLY);
164	if (cg_fd < 0) {
165		printf("Failed to open cgroup path: '%s'\n", strerror(errno));
166		return EXIT_FAILURE;
167	}
168
169	if (detach_only) {
170		ret = bpf_prog_detach(cg_fd, type);
171		printf("bpf_prog_detach() returned '%s' (%d)\n",
172		       strerror(errno), errno);
173	} else
174		ret = attach_filter(cg_fd, type, verdict);
175
176	return ret;
177}
178