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();
+}