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/* eBPF example program:
*
* - Loads eBPF program
*
* The eBPF program sets the sk_bound_dev_if index in new AF_INET{6}
* sockets opened by processes in the cgroup.
*
* - Attaches the new program to a cgroup using BPF_PROG_ATTACH
*/
#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 <net/if.h>
#include <linux/bpf.h>
#include "libbpf.h"
char bpf_log_buf[BPF_LOG_BUF_SIZE];
static int prog_load(int idx)
{
struct bpf_insn prog[] = {
BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
BPF_MOV64_IMM(BPF_REG_3, idx),
BPF_MOV64_IMM(BPF_REG_2, offsetof(struct bpf_sock, bound_dev_if)),
BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_3, offsetof(struct bpf_sock, bound_dev_if)),
BPF_MOV64_IMM(BPF_REG_0, 1), /* r0 = verdict */
BPF_EXIT_INSN(),
};
size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
return bpf_load_program(BPF_PROG_TYPE_CGROUP_SOCK, prog, insns_cnt,
"GPL", 0, bpf_log_buf, BPF_LOG_BUF_SIZE);
}
static int usage(const char *argv0)
{
printf("Usage: %s cg-path device-index\n", argv0);
return EXIT_FAILURE;
}
int main(int argc, char **argv)
{
int cg_fd, prog_fd, ret;
unsigned int idx;
if (argc < 2)
return usage(argv[0]);
idx = if_nametoindex(argv[2]);
if (!idx) {
printf("Invalid device name\n");
return EXIT_FAILURE;
}
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;
}
prog_fd = prog_load(idx);
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, BPF_CGROUP_INET_SOCK_CREATE, 0);
if (ret < 0) {
printf("Failed to attach prog to cgroup: '%s'\n",
strerror(errno));
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
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