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https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
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03f4723ed7
this socket filter example does:
- creates arraymap in kernel with key 4 bytes and value 8 bytes
- loads eBPF program which assumes that packet is IPv4 and loads one byte of
IP->proto from the packet and uses it as a key in a map
r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
*(u32*)(fp - 4) = r0;
value = bpf_map_lookup_elem(map_fd, fp - 4);
if (value)
(*(u64*)value) += 1;
- attaches this program to raw socket
- every second user space reads map[IPPROTO_TCP], map[IPPROTO_UDP], map[IPPROTO_ICMP]
to see how many packets of given protocol were seen on loopback interface
Usage:
$sudo samples/bpf/sock_example
TCP 0 UDP 0 ICMP 0 packets
TCP 187600 UDP 0 ICMP 4 packets
TCP 376504 UDP 0 ICMP 8 packets
TCP 563116 UDP 0 ICMP 12 packets
TCP 753144 UDP 0 ICMP 16 packets
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
101 lines
2.7 KiB
C
101 lines
2.7 KiB
C
/* eBPF example program:
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* - creates arraymap in kernel with key 4 bytes and value 8 bytes
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*
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* - loads eBPF program:
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* r0 = skb->data[ETH_HLEN + offsetof(struct iphdr, protocol)];
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* *(u32*)(fp - 4) = r0;
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* // assuming packet is IPv4, lookup ip->proto in a map
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* value = bpf_map_lookup_elem(map_fd, fp - 4);
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* if (value)
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* (*(u64*)value) += 1;
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*
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* - attaches this program to eth0 raw socket
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*
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* - every second user space reads map[tcp], map[udp], map[icmp] to see
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* how many packets of given protocol were seen on eth0
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*/
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#include <stdio.h>
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#include <unistd.h>
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#include <assert.h>
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#include <linux/bpf.h>
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#include <string.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <sys/socket.h>
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#include <arpa/inet.h>
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#include <linux/if_ether.h>
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#include <linux/ip.h>
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#include <stddef.h>
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#include "libbpf.h"
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static int test_sock(void)
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{
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int sock = -1, map_fd, prog_fd, i, key;
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long long value = 0, tcp_cnt, udp_cnt, icmp_cnt;
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map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(key), sizeof(value),
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256);
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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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goto cleanup;
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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),
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BPF_LD_ABS(BPF_B, ETH_HLEN + offsetof(struct iphdr, protocol) /* R0 = ip->proto */),
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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_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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BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 */
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BPF_EXIT_INSN(),
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};
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prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, prog, sizeof(prog),
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"GPL");
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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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goto cleanup;
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}
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sock = open_raw_sock("lo");
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if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
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sizeof(prog_fd)) < 0) {
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printf("setsockopt %s\n", strerror(errno));
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goto cleanup;
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}
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for (i = 0; i < 10; i++) {
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key = IPPROTO_TCP;
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assert(bpf_lookup_elem(map_fd, &key, &tcp_cnt) == 0);
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key = IPPROTO_UDP;
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assert(bpf_lookup_elem(map_fd, &key, &udp_cnt) == 0);
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key = IPPROTO_ICMP;
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assert(bpf_lookup_elem(map_fd, &key, &icmp_cnt) == 0);
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printf("TCP %lld UDP %lld ICMP %lld packets\n",
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tcp_cnt, udp_cnt, icmp_cnt);
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sleep(1);
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}
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cleanup:
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/* maps, programs, raw sockets will auto cleanup on process exit */
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return 0;
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}
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int main(void)
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{
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FILE *f;
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f = popen("ping -c5 localhost", "r");
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(void)f;
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return test_sock();
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}
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