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>
diff --git a/samples/bpf/sock_example.c b/samples/bpf/sock_example.c
new file mode 100644
index 0000000..c8ad040
--- /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();
+}