bpf: add sample usages for persistent maps/progs

This patch adds a couple of stand-alone examples on how BPF_OBJ_PIN
and BPF_OBJ_GET commands can be used.

Example with maps:

  # ./fds_example -F /sys/fs/bpf/m -P -m -k 1 -v 42
  bpf: map fd:3 (Success)
  bpf: pin ret:(0,Success)
  bpf: fd:3 u->(1:42) ret:(0,Success)
  # ./fds_example -F /sys/fs/bpf/m -G -m -k 1
  bpf: get fd:3 (Success)
  bpf: fd:3 l->(1):42 ret:(0,Success)
  # ./fds_example -F /sys/fs/bpf/m -G -m -k 1 -v 24
  bpf: get fd:3 (Success)
  bpf: fd:3 u->(1:24) ret:(0,Success)
  # ./fds_example -F /sys/fs/bpf/m -G -m -k 1
  bpf: get fd:3 (Success)
  bpf: fd:3 l->(1):24 ret:(0,Success)

  # ./fds_example -F /sys/fs/bpf/m2 -P -m
  bpf: map fd:3 (Success)
  bpf: pin ret:(0,Success)
  # ./fds_example -F /sys/fs/bpf/m2 -G -m -k 1
  bpf: get fd:3 (Success)
  bpf: fd:3 l->(1):0 ret:(0,Success)
  # ./fds_example -F /sys/fs/bpf/m2 -G -m
  bpf: get fd:3 (Success)

Example with progs:

  # ./fds_example -F /sys/fs/bpf/p -P -p
  bpf: prog fd:3 (Success)
  bpf: pin ret:(0,Success)
  bpf sock:4 <- fd:3 attached ret:(0,Success)
  # ./fds_example -F /sys/fs/bpf/p -G -p
  bpf: get fd:3 (Success)
  bpf: sock:4 <- fd:3 attached ret:(0,Success)

  # ./fds_example -F /sys/fs/bpf/p2 -P -p -o ./sockex1_kern.o
  bpf: prog fd:5 (Success)
  bpf: pin ret:(0,Success)
  bpf: sock:3 <- fd:5 attached ret:(0,Success)
  # ./fds_example -F /sys/fs/bpf/p2 -G -p
  bpf: get fd:3 (Success)
  bpf: sock:4 <- fd:3 attached ret:(0,Success)

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 208 insertions, 0 deletions

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index b30514514e37..79b4596b5f9a 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -4,6 +4,7 @@ obj- := dummy.o
 # List of programs to build
 hostprogs-y := test_verifier test_maps
 hostprogs-y += sock_example
+hostprogs-y += fds_example
 hostprogs-y += sockex1
 hostprogs-y += sockex2
 hostprogs-y += sockex3
@@ -19,6 +20,7 @@ hostprogs-y += lathist
 test_verifier-objs := test_verifier.o libbpf.o
 test_maps-objs := test_maps.o libbpf.o
 sock_example-objs := sock_example.o libbpf.o
+fds_example-objs := bpf_load.o libbpf.o fds_example.o
 sockex1-objs := bpf_load.o libbpf.o sockex1_user.o
 sockex2-objs := bpf_load.o libbpf.o sockex2_user.o
 sockex3-objs := bpf_load.o libbpf.o sockex3_user.o
@@ -49,6 +51,7 @@ always += lathist_kern.o
 HOSTCFLAGS += -I$(objtree)/usr/include
 
 HOSTCFLAGS_bpf_load.o += -I$(objtree)/usr/include -Wno-unused-variable
+HOSTLOADLIBES_fds_example += -lelf
 HOSTLOADLIBES_sockex1 += -lelf
 HOSTLOADLIBES_sockex2 += -lelf
 HOSTLOADLIBES_sockex3 += -lelf
diff --git a/samples/bpf/fds_example.c b/samples/bpf/fds_example.c
new file mode 100644
index 000000000000..e2fd16c3d0f0
--- /dev/null
+++ b/samples/bpf/fds_example.c
@@ -0,0 +1,183 @@
+#include <linux/unistd.h>
+#include <linux/bpf.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <string.h>
+#include <assert.h>
+#include <errno.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#include "bpf_load.h"
+#include "libbpf.h"
+
+#define BPF_F_PIN       (1 << 0)
+#define BPF_F_GET       (1 << 1)
+#define BPF_F_PIN_GET   (BPF_F_PIN | BPF_F_GET)
+
+#define BPF_F_KEY       (1 << 2)
+#define BPF_F_VAL       (1 << 3)
+#define BPF_F_KEY_VAL   (BPF_F_KEY | BPF_F_VAL)
+
+#define BPF_M_UNSPEC    0
+#define BPF_M_MAP       1
+#define BPF_M_PROG      2
+
+static void usage(void)
+{
+        printf("Usage: fds_example [...]\n");
+        printf("       -F <file>   File to pin/get object\n");
+        printf("       -P          |- pin object\n");
+        printf("       -G          `- get object\n");
+        printf("       -m          eBPF map mode\n");
+        printf("       -k <key>    |- map key\n");
+        printf("       -v <value>  `- map value\n");
+        printf("       -p          eBPF prog mode\n");
+        printf("       -o <object> `- object file\n");
+        printf("       -h          Display this help.\n");
+}
+
+static int bpf_map_create(void)
+{
+        return bpf_create_map(BPF_MAP_TYPE_ARRAY, sizeof(uint32_t),
+                              sizeof(uint32_t), 1024);
+}
+
+static int bpf_prog_create(const char *object)
+{
+        static const struct bpf_insn insns[] = {
+                BPF_MOV64_IMM(BPF_REG_0, 1),
+                BPF_EXIT_INSN(),
+        };
+
+        if (object) {
+                assert(!load_bpf_file((char *)object));
+                return prog_fd[0];
+        } else {
+                return bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER,
+                                     insns, sizeof(insns), "GPL", 0);
+        }
+}
+
+static int bpf_do_map(const char *file, uint32_t flags, uint32_t key,
+                      uint32_t value)
+{
+        int fd, ret;
+
+        if (flags & BPF_F_PIN) {
+                fd = bpf_map_create();
+                printf("bpf: map fd:%d (%s)\n", fd, strerror(errno));
+                assert(fd > 0);
+
+                ret = bpf_obj_pin(fd, file);
+                printf("bpf: pin ret:(%d,%s)\n", ret, strerror(errno));
+                assert(ret == 0);
+        } else {
+                fd = bpf_obj_get(file);
+                printf("bpf: get fd:%d (%s)\n", fd, strerror(errno));
+                assert(fd > 0);
+        }
+
+        if ((flags & BPF_F_KEY_VAL) == BPF_F_KEY_VAL) {
+                ret = bpf_update_elem(fd, &key, &value, 0);
+                printf("bpf: fd:%d u->(%u:%u) ret:(%d,%s)\n", fd, key, value,
+                       ret, strerror(errno));
+                assert(ret == 0);
+        } else if (flags & BPF_F_KEY) {
+                ret = bpf_lookup_elem(fd, &key, &value);
+                printf("bpf: fd:%d l->(%u):%u ret:(%d,%s)\n", fd, key, value,
+                       ret, strerror(errno));
+                assert(ret == 0);
+        }
+
+        return 0;
+}
+
+static int bpf_do_prog(const char *file, uint32_t flags, const char *object)
+{
+        int fd, sock, ret;
+
+        if (flags & BPF_F_PIN) {
+                fd = bpf_prog_create(object);
+                printf("bpf: prog fd:%d (%s)\n", fd, strerror(errno));
+                assert(fd > 0);
+
+                ret = bpf_obj_pin(fd, file);
+                printf("bpf: pin ret:(%d,%s)\n", ret, strerror(errno));
+                assert(ret == 0);
+        } else {
+                fd = bpf_obj_get(file);
+                printf("bpf: get fd:%d (%s)\n", fd, strerror(errno));
+                assert(fd > 0);
+        }
+
+        sock = open_raw_sock("lo");
+        assert(sock > 0);
+
+        ret = setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &fd, sizeof(fd));
+        printf("bpf: sock:%d <- fd:%d attached ret:(%d,%s)\n", sock, fd,
+               ret, strerror(errno));
+        assert(ret == 0);
+
+        return 0;
+}
+
+int main(int argc, char **argv)
+{
+        const char *file = NULL, *object = NULL;
+        uint32_t key = 0, value = 0, flags = 0;
+        int opt, mode = BPF_M_UNSPEC;
+
+        while ((opt = getopt(argc, argv, "F:PGmk:v:po:")) != -1) {
+                switch (opt) {
+                /* General args */
+                case 'F':
+                        file = optarg;
+                        break;
+                case 'P':
+                        flags |= BPF_F_PIN;
+                        break;
+                case 'G':
+                        flags |= BPF_F_GET;
+                        break;
+                /* Map-related args */
+                case 'm':
+                        mode = BPF_M_MAP;
+                        break;
+                case 'k':
+                        key = strtoul(optarg, NULL, 0);
+                        flags |= BPF_F_KEY;
+                        break;
+                case 'v':
+                        value = strtoul(optarg, NULL, 0);
+                        flags |= BPF_F_VAL;
+                        break;
+                /* Prog-related args */
+                case 'p':
+                        mode = BPF_M_PROG;
+                        break;
+                case 'o':
+                        object = optarg;
+                        break;
+                default:
+                        goto out;
+                }
+        }
+
+        if (!(flags & BPF_F_PIN_GET) || !file)
+                goto out;
+
+        switch (mode) {
+        case BPF_M_MAP:
+                return bpf_do_map(file, flags, key, value);
+        case BPF_M_PROG:
+                return bpf_do_prog(file, flags, object);
+        }
+out:
+        usage();
+        return -1;
+}
diff --git a/samples/bpf/libbpf.c b/samples/bpf/libbpf.c
index 7e1efa7e2ed7..65a8d48d2799 100644
--- a/samples/bpf/libbpf.c
+++ b/samples/bpf/libbpf.c
@@ -103,6 +103,25 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
         return syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
 }
 
+int bpf_obj_pin(int fd, const char *pathname)
+{
+        union bpf_attr attr = {
+                .pathname       = ptr_to_u64((void *)pathname),
+                .bpf_fd         = fd,
+        };
+
+        return syscall(__NR_bpf, BPF_OBJ_PIN, &attr, sizeof(attr));
+}
+
+int bpf_obj_get(const char *pathname)
+{
+        union bpf_attr attr = {
+                .pathname       = ptr_to_u64((void *)pathname),
+        };
+
+        return syscall(__NR_bpf, BPF_OBJ_GET, &attr, sizeof(attr));
+}
+
 int open_raw_sock(const char *name)
 {
         struct sockaddr_ll sll;
diff --git a/samples/bpf/libbpf.h b/samples/bpf/libbpf.h
index b7f63c70b4a2..014aacf916e4 100644
--- a/samples/bpf/libbpf.h
+++ b/samples/bpf/libbpf.h
@@ -15,6 +15,9 @@ int bpf_prog_load(enum bpf_prog_type prog_type,
                   const struct bpf_insn *insns, int insn_len,
                   const char *license, int kern_version);
 
+int bpf_obj_pin(int fd, const char *pathname);
+int bpf_obj_get(const char *pathname);
+
 #define LOG_BUF_SIZE 65536
 extern char bpf_log_buf[LOG_BUF_SIZE];