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/* eBPF example program:
* - creates arraymap in kernel with key 4 bytes and value 8 bytes
*
* - loads eBPF program:
* r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
* *(u32*)(fp - 4) = r0;
* // assuming packet is IPv4, lookup ip->proto in a map
* value = bpf_map_lookup_elem(map_fd, fp - 4);
* if (value)
* (*(u64*)value) += 1;
*
* - attaches this program to loopback interface "lo" raw socket
*
* - every second user space reads map[tcp], map[udp], map[icmp] to see
* how many packets of given protocol were seen on "lo"
*/
#include <stdio.h>
#include <unistd.h>
#include <assert.h>
#include <linux/bpf.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <linux/if_ether.h>
#include <linux/ip.h>
#include <stddef.h>
#include <bpf/bpf.h>
#include "bpf_insn.h"
#include "sock_example.h"
char bpf_log_buf[BPF_LOG_BUF_SIZE];
static int test_sock(void)
{
int sock = -1, map_fd, prog_fd, i, key;
long long value = 0, tcp_cnt, udp_cnt, icmp_cnt;
map_fd = bpf_map_create(BPF_MAP_TYPE_ARRAY, NULL, sizeof(key), sizeof(value),
256, NULL);
if (map_fd < 0) {
printf("failed to create map '%s'\n", strerror(errno));
goto cleanup;
}
struct bpf_insn prog[] = {
BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
BPF_LD_ABS(BPF_B, ETH_HLEN + offsetof(struct iphdr, protocol) /* R0 = ip->proto */),
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_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 */
BPF_EXIT_INSN(),
};
size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
LIBBPF_OPTS(bpf_prog_load_opts, opts,
.log_buf = bpf_log_buf,
.log_size = BPF_LOG_BUF_SIZE,
);
prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, NULL, "GPL",
prog, insns_cnt, &opts);
if (prog_fd < 0) {
printf("failed to load prog '%s'\n", strerror(errno));
goto cleanup;
}
sock = open_raw_sock("lo");
if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
sizeof(prog_fd)) < 0) {
printf("setsockopt %s\n", strerror(errno));
goto cleanup;
}
for (i = 0; i < 10; i++) {
key = IPPROTO_TCP;
assert(bpf_map_lookup_elem(map_fd, &key, &tcp_cnt) == 0);
key = IPPROTO_UDP;
assert(bpf_map_lookup_elem(map_fd, &key, &udp_cnt) == 0);
key = IPPROTO_ICMP;
assert(bpf_map_lookup_elem(map_fd, &key, &icmp_cnt) == 0);
printf("TCP %lld UDP %lld ICMP %lld packets\n",
tcp_cnt, udp_cnt, icmp_cnt);
sleep(1);
}
cleanup:
/* maps, programs, raw sockets will auto cleanup on process exit */
return 0;
}
int main(void)
{
FILE *f;
f = popen("ping -4 -c5 localhost", "r");
(void)f;
return test_sock();
}
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