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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 <inttypes.h>
#include <linux/bpf.h>
#include "libbpf.h"
char bpf_log_buf[BPF_LOG_BUF_SIZE];
static int prog_load(__u32 idx, __u32 mark, __u32 prio)
{
/* save pointer to context */
struct bpf_insn prog_start[] = {
BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
};
struct bpf_insn prog_end[] = {
BPF_MOV64_IMM(BPF_REG_0, 1), /* r0 = verdict */
BPF_EXIT_INSN(),
};
/* set sk_bound_dev_if on socket */
struct bpf_insn prog_dev[] = {
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)),
};
/* set mark on socket */
struct bpf_insn prog_mark[] = {
BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
BPF_MOV64_IMM(BPF_REG_3, mark),
BPF_MOV64_IMM(BPF_REG_2, offsetof(struct bpf_sock, mark)),
BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_3, offsetof(struct bpf_sock, mark)),
};
/* set priority on socket */
struct bpf_insn prog_prio[] = {
BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
BPF_MOV64_IMM(BPF_REG_3, prio),
BPF_MOV64_IMM(BPF_REG_2, offsetof(struct bpf_sock, priority)),
BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_3, offsetof(struct bpf_sock, priority)),
};
struct bpf_insn *prog;
size_t insns_cnt;
void *p;
int ret;
insns_cnt = sizeof(prog_start) + sizeof(prog_end);
if (idx)
insns_cnt += sizeof(prog_dev);
if (mark)
insns_cnt += sizeof(prog_mark);
if (prio)
insns_cnt += sizeof(prog_prio);
p = prog = malloc(insns_cnt);
if (!prog) {
fprintf(stderr, "Failed to allocate memory for instructions\n");
return EXIT_FAILURE;
}
memcpy(p, prog_start, sizeof(prog_start));
p += sizeof(prog_start);
if (idx) {
memcpy(p, prog_dev, sizeof(prog_dev));
p += sizeof(prog_dev);
}
if (mark) {
memcpy(p, prog_mark, sizeof(prog_mark));
p += sizeof(prog_mark);
}
if (prio) {
memcpy(p, prog_prio, sizeof(prog_prio));
p += sizeof(prog_prio);
}
memcpy(p, prog_end, sizeof(prog_end));
p += sizeof(prog_end);
insns_cnt /= sizeof(struct bpf_insn);
ret = bpf_load_program(BPF_PROG_TYPE_CGROUP_SOCK, prog, insns_cnt,
"GPL", 0, bpf_log_buf, BPF_LOG_BUF_SIZE);
free(prog);
return ret;
}
static int usage(const char *argv0)
{
printf("Usage: %s -b bind-to-dev -m mark -p prio cg-path\n", argv0);
return EXIT_FAILURE;
}
int main(int argc, char **argv)
{
__u32 idx = 0, mark = 0, prio = 0;
const char *cgrp_path = NULL;
int cg_fd, prog_fd, ret;
int rc;
while ((rc = getopt(argc, argv, "b:m:p:")) != -1) {
switch (rc) {
case 'b':
idx = if_nametoindex(optarg);
if (!idx) {
idx = strtoumax(optarg, NULL, 0);
if (!idx) {
printf("Invalid device name\n");
return EXIT_FAILURE;
}
}
break;
case 'm':
mark = strtoumax(optarg, NULL, 0);
break;
case 'p':
prio = strtoumax(optarg, NULL, 0);
break;
default:
return usage(argv[0]);
}
}
if (optind == argc)
return usage(argv[0]);
cgrp_path = argv[optind];
if (!cgrp_path) {
fprintf(stderr, "cgroup path not given\n");
return EXIT_FAILURE;
}
if (!idx && !mark && !prio) {
fprintf(stderr,
"One of device, mark or priority must be given\n");
return EXIT_FAILURE;
}
cg_fd = open(cgrp_path, 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, mark, prio);
if (prog_fd < 0) {
printf("Failed to load prog: '%s'\n", strerror(errno));
printf("Output from kernel verifier:\n%s\n-------\n",
bpf_log_buf);
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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