/* 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.
*
* - Detaches any eBPF program previously attached to the cgroup
*
* - 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 "libbpf.h"
enum {
MAP_KEY_PACKETS,
MAP_KEY_BYTES,
};
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_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
/* 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_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */
BPF_EXIT_INSN(),
};
return bpf_prog_load(BPF_PROG_TYPE_CGROUP_SKB,
prog, sizeof(prog), "GPL", 0);
}
static int usage(const char *argv0)
{
printf("Usage: %s <cg-path> <egress|ingress> [drop]\n", argv0);
return EXIT_FAILURE;
}
int main(int argc, char **argv)
{
int cg_fd, map_fd, prog_fd, key, ret;
long long pkt_cnt, byte_cnt;
enum bpf_attach_type type;
int verdict = 1;
if (argc < 3)
return usage(argv[0]);
if (strcmp(argv[2], "ingress") == 0)
type = BPF_CGROUP_INET_INGRESS;
else if (strcmp(argv[2], "egress") == 0)
type = BPF_CGROUP_INET_EGRESS;
else
return usage(argv[0]);
if (argc > 3 && strcmp(argv[3], "drop") == 0)
verdict = 0;
cg_fd = open(argv[1], O_DIRECTORY | O_RDONLY);
if (cg_fd < 0) {
printf("Failed to open cgroup path: '%s'\n", strerror(errno));
return EXIT_FAILURE;
}
map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY,
sizeof(key), sizeof(byte_cnt),
256, 0);
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_detach(cg_fd, type);
printf("bpf_prog_detach() returned '%s' (%d)\n", strerror(errno), errno);
ret = bpf_prog_attach(prog_fd, cg_fd, type);
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_lookup_elem(map_fd, &key, &pkt_cnt) == 0);
key = MAP_KEY_BYTES;
assert(bpf_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;
}
