148 lines
4.1 KiB
C
148 lines
4.1 KiB
C
/* eBPF example program:
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*
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* - Creates arraymap in kernel with 4 bytes keys and 8 byte values
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*
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* - Loads eBPF program
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*
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* The eBPF program accesses the map passed in to store two pieces of
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* information. The number of invocations of the program, which maps
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* to the number of packets received, is stored to key 0. Key 1 is
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* incremented on each iteration by the number of bytes stored in
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* the skb.
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*
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* - Detaches any eBPF program previously attached to the cgroup
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*
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* - Attaches the new program to a cgroup using BPF_PROG_ATTACH
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*
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* - Every second, reads map[0] and map[1] to see how many bytes and
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* packets were seen on any socket of tasks in the given cgroup.
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*/
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#define _GNU_SOURCE
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#include <stdio.h>
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#include <stdlib.h>
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#include <stddef.h>
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#include <string.h>
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#include <unistd.h>
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <linux/bpf.h>
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#include "libbpf.h"
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enum {
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MAP_KEY_PACKETS,
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MAP_KEY_BYTES,
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};
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static int prog_load(int map_fd, int verdict)
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{
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struct bpf_insn prog[] = {
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BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* save r6 so it's not clobbered by BPF_CALL */
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/* Count packets */
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BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */
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BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
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BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
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BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
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BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* load map fd to r1 */
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BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
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BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
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BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
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/* Count bytes */
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BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */
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BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
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BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
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BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
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BPF_LD_MAP_FD(BPF_REG_1, map_fd),
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BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
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BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */
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BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
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BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */
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BPF_EXIT_INSN(),
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};
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return bpf_prog_load(BPF_PROG_TYPE_CGROUP_SKB,
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prog, sizeof(prog), "GPL", 0);
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}
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static int usage(const char *argv0)
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{
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printf("Usage: %s <cg-path> <egress|ingress> [drop]\n", argv0);
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return EXIT_FAILURE;
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}
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int main(int argc, char **argv)
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{
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int cg_fd, map_fd, prog_fd, key, ret;
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long long pkt_cnt, byte_cnt;
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enum bpf_attach_type type;
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int verdict = 1;
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if (argc < 3)
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return usage(argv[0]);
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if (strcmp(argv[2], "ingress") == 0)
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type = BPF_CGROUP_INET_INGRESS;
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else if (strcmp(argv[2], "egress") == 0)
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type = BPF_CGROUP_INET_EGRESS;
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else
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return usage(argv[0]);
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if (argc > 3 && strcmp(argv[3], "drop") == 0)
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verdict = 0;
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cg_fd = open(argv[1], O_DIRECTORY | O_RDONLY);
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if (cg_fd < 0) {
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printf("Failed to open cgroup path: '%s'\n", strerror(errno));
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return EXIT_FAILURE;
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}
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map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY,
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sizeof(key), sizeof(byte_cnt),
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256, 0);
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if (map_fd < 0) {
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printf("Failed to create map: '%s'\n", strerror(errno));
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return EXIT_FAILURE;
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}
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prog_fd = prog_load(map_fd, verdict);
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printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);
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if (prog_fd < 0) {
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printf("Failed to load prog: '%s'\n", strerror(errno));
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return EXIT_FAILURE;
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}
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ret = bpf_prog_detach(cg_fd, type);
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printf("bpf_prog_detach() returned '%s' (%d)\n", strerror(errno), errno);
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ret = bpf_prog_attach(prog_fd, cg_fd, type, 0);
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if (ret < 0) {
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printf("Failed to attach prog to cgroup: '%s'\n",
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strerror(errno));
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return EXIT_FAILURE;
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}
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while (1) {
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key = MAP_KEY_PACKETS;
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assert(bpf_lookup_elem(map_fd, &key, &pkt_cnt) == 0);
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key = MAP_KEY_BYTES;
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assert(bpf_lookup_elem(map_fd, &key, &byte_cnt) == 0);
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printf("cgroup received %lld packets, %lld bytes\n",
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pkt_cnt, byte_cnt);
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sleep(1);
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}
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return EXIT_SUCCESS;
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}
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