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author | Alexei Starovoitov <ast@plumgrid.com> | 2014-12-01 15:06:36 -0800 |
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committer | David S. Miller <davem@davemloft.net> | 2014-12-05 21:47:32 -0800 |
commit | 03f4723ed7a52bd31da26eefe2cdde563ea0f468 (patch) | |
tree | 4a3f1b2427c8bf1f2e86f4f1e842a32c5602b621 /samples/bpf/sock_example.c | |
parent | 89aa075832b0da4402acebd698d0411dcc82d03e (diff) | |
download | linux-03f4723ed7a52bd31da26eefe2cdde563ea0f468.tar.gz linux-03f4723ed7a52bd31da26eefe2cdde563ea0f468.tar.bz2 linux-03f4723ed7a52bd31da26eefe2cdde563ea0f468.zip |
samples: bpf: example of stateful socket filtering
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>
Diffstat (limited to 'samples/bpf/sock_example.c')
-rw-r--r-- | samples/bpf/sock_example.c | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/samples/bpf/sock_example.c b/samples/bpf/sock_example.c new file mode 100644 index 000000000000..c8ad0404416f --- /dev/null +++ b/samples/bpf/sock_example.c @@ -0,0 +1,101 @@ +/* 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 eth0 raw socket + * + * - every second user space reads map[tcp], map[udp], map[icmp] to see + * how many packets of given protocol were seen on eth0 + */ +#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 "libbpf.h" + +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_create_map(BPF_MAP_TYPE_ARRAY, sizeof(key), sizeof(value), + 256); + 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_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */ + BPF_MOV64_IMM(BPF_REG_0, 0), /* r0 = 0 */ + BPF_EXIT_INSN(), + }; + + prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, prog, sizeof(prog), + "GPL"); + 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_lookup_elem(map_fd, &key, &tcp_cnt) == 0); + + key = IPPROTO_UDP; + assert(bpf_lookup_elem(map_fd, &key, &udp_cnt) == 0); + + key = IPPROTO_ICMP; + assert(bpf_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 -c5 localhost", "r"); + (void)f; + + return test_sock(); +} |