Support bpf_get_socket_cookie in more prog types

bpf_get_socket_cookie() helper can be used to identify skb that correspond to the same socket.

Though socket cookie can be useful in many other use-cases where socket is available in program context. Specifically BPF_PROG_TYPE_CGROUP_SOCK_ADDR and BPF_PROG_TYPE_SOCK_OPS programs can benefit from it so that one of them can augment a value in a map prepared earlier by other program for the same socket.

The patch adds support to call bpf_get_socket_cookie() from BPF_PROG_TYPE_CGROUP_SOCK_ADDR and BPF_PROG_TYPE_SOCK_OPS.

It doesn't introduce new helpers. Instead it reuses same helper name bpf_get_socket_cookie() but adds support to this helper to accept struct bpf_sock_addr and struct bpf_sock_ops.

Documentation in bpf.h is changed in a way that should not break automatic generation of markdown.

Signed-off-by Andrey Ignatov <[email protected]>

Sync bpf_get_socket_cookie() related bpf UAPI changes to tools/.

Signed-off-by Andrey Ignatov <[email protected]>

Add missing helper to bpf_helpers.h that is used in tests and samples.

Signed-off-by Andrey Ignatov <[email protected]>

Add test to use get_socket_cookie() from BPF programs of types BPF_PROG_TYPE_SOCK_OPS and BPF_PROG_TYPE_CGROUP_SOCK_ADDR.

The test attaches two programs to cgroup, runs TCP server and client in the cgroup and checks that two operations are done properly on client socket when user calls connect(2):

1. In BPF_CGROUP_INET6_CONNECT socket cookie is used as the key to write new value in a map for client socket.

2. In BPF_CGROUP_SOCK_OPS (BPF_SOCK_OPS_TCP_CONNECT_CB callback) the value written in "1." is found by socket cookie, since it's the same socket, and updated.

Finally the test verifies the value in the map.

Signed-off-by Andrey Ignatov <[email protected]>

---
  tools/testing/selftests/bpf/Makefile          |   6 +-
  .../selftests/bpf/socket_cookie_prog.c        |  60 +++++
  .../selftests/bpf/test_socket_cookie.c        | 249 ++++++++++++++++++
  3 files changed, 313 insertions(+), 2 deletions(-)

create mode 100644 tools/testing/selftests/bpf/socket_cookie_prog.c create mode 100644 tools/testing/selftests/bpf/test_socket_cookie.c

tools/testing/selftests/bpf/Makefile +4 -2

index 478bf1bcbbf5..1b28277998e2 100644
@@ -22,7 +22,8 @@ $(TEST_CUSTOM_PROGS): $(OUTPUT)/%: %.c
  # Order correspond to 'make run_tests' order
  TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \
  	test_align test_verifier_log test_dev_cgroup test_tcpbpf_user \
-	test_sock test_btf test_sockmap test_lirc_mode2_user get_cgroup_id_user
+	test_sock test_btf test_sockmap test_lirc_mode2_user get_cgroup_id_user \
+	test_socket_cookie
 
  TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test_obj_id.o \
  	test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \

@@ -33,7 +34,7 @@ TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test
  	test_btf_haskv.o test_btf_nokv.o test_sockmap_kern.o test_tunnel_kern.o \
  	test_get_stack_rawtp.o test_sockmap_kern.o test_sockhash_kern.o \
  	test_lwt_seg6local.o sendmsg4_prog.o sendmsg6_prog.o test_lirc_mode2_kern.o \
-	get_cgroup_id_kern.o
+	get_cgroup_id_kern.o socket_cookie_prog.o
 
  # Order correspond to 'make run_tests' order
  TEST_PROGS := test_kmod.sh \

@@ -60,6 +61,7 @@ $(TEST_GEN_PROGS_EXTENDED): $(OUTPUT)/libbpf.a
  $(OUTPUT)/test_dev_cgroup: cgroup_helpers.c
  $(OUTPUT)/test_sock: cgroup_helpers.c
  $(OUTPUT)/test_sock_addr: cgroup_helpers.c
+$(OUTPUT)/test_socket_cookie: cgroup_helpers.c
  $(OUTPUT)/test_sockmap: cgroup_helpers.c
  $(OUTPUT)/test_tcpbpf_user: cgroup_helpers.c
  $(OUTPUT)/test_progs: trace_helpers.c

tools/testing/selftests/bpf/socket_cookie_prog.c new file +60 -0

new file mode 100644
index 000000000000..9ff8ac4b0bf6
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <linux/bpf.h>
+#include <sys/socket.h>
+
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+struct bpf_map_def SEC("maps") socket_cookies = {
+	.type = BPF_MAP_TYPE_HASH,
+	.key_size = sizeof(__u64),
+	.value_size = sizeof(__u32),
+	.max_entries = 1 << 8,
+};
+
+SEC("cgroup/connect6")
+int set_cookie(struct bpf_sock_addr *ctx)
+{
+	__u32 cookie_value = 0xFF;
+	__u64 cookie_key;
+
+	if (ctx->family != AF_INET6 || ctx->user_family != AF_INET6)
+		return 1;
+
+	cookie_key = bpf_get_socket_cookie(ctx);
+	if (bpf_map_update_elem(&socket_cookies, &cookie_key, &cookie_value, 0))
+		return 0;
+
+	return 1;
+}
+
+SEC("sockops")
+int update_cookie(struct bpf_sock_ops *ctx)
+{
+	__u32 new_cookie_value;
+	__u32 *cookie_value;
+	__u64 cookie_key;
+
+	if (ctx->family != AF_INET6)
+		return 1;
+
+	if (ctx->op != BPF_SOCK_OPS_TCP_CONNECT_CB)
+		return 1;
+
+	cookie_key = bpf_get_socket_cookie(ctx);
+
+	cookie_value = bpf_map_lookup_elem(&socket_cookies, &cookie_key);
+	if (!cookie_value)
+		return 1;
+
+	new_cookie_value = (ctx->local_port << 8) | *cookie_value;
+	bpf_map_update_elem(&socket_cookies, &cookie_key, &new_cookie_value, 0);
+
+	return 1;
+}
+
+int _version SEC("version") = 1;
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/test_socket_cookie.c new file +190 -0

new file mode 100644
index 000000000000..eed4b3bc9fcd
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <string.h>
+#include <unistd.h>
+
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+
+#include "bpf_rlimit.h"
+#include "cgroup_helpers.h"
+
+#define CG_PATH			"/foo"
+#define SOCKET_COOKIE_PROG	"./socket_cookie_prog.o"
+
+static int attach_type_by_name(const char *prog_name,
+			       enum bpf_attach_type *attach_type)
+{
+	enum bpf_attach_type expected_attach_type;
+	enum bpf_prog_type prog_type;
+	int err = 0;
+
+	err = libbpf_prog_type_by_name(prog_name, &prog_type,
+				       &expected_attach_type);
+	if (err) {
+		log_err("Failed to get type for prog %s", prog_name);
+		goto out;
+	}
+
+	if (expected_attach_type) {
+		*attach_type = expected_attach_type;
+		goto out;
+	}
+
+	switch (prog_type) {
+	case BPF_PROG_TYPE_SOCK_OPS:
+		*attach_type = BPF_CGROUP_SOCK_OPS;
+		break;
+	default:
+		log_err("Can't detect attach type for prog %s", prog_name);
+		err = -1;
+	}
+out:
+	return err;
+}
+
+static int start_server(void)
+{
+	struct sockaddr_in6 addr;
+	int fd;
+
+	fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (fd == -1) {
+		log_err("Failed to create server socket");
+		goto out;
+	}
+
+	memset(&addr, 0, sizeof(addr));
+	addr.sin6_family = AF_INET6;
+	addr.sin6_addr = in6addr_loopback;
+	addr.sin6_port = 0;
+
+	if (bind(fd, (const struct sockaddr *)&addr, sizeof(addr)) == -1) {
+		log_err("Failed to bind server socket");
+		goto close_out;
+	}
+
+	if (listen(fd, 128) == -1) {
+		log_err("Failed to listen on server socket");
+		goto close_out;
+	}
+
+	goto out;
+
+close_out:
+	close(fd);
+	fd = -1;
+out:
+	return fd;
+}
+
+static int connect_to_server(int server_fd)
+{
+	struct sockaddr_storage addr;
+	socklen_t len = sizeof(addr);
+	int fd;
+
+	fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (fd == -1) {
+		log_err("Failed to create client socket");
+		goto out;
+	}
+
+	if (getsockname(server_fd, (struct sockaddr *)&addr, &len)) {
+		log_err("Failed to get server addr");
+		goto close_out;
+	}
+
+	if (connect(fd, (const struct sockaddr *)&addr, len) == -1) {
+		log_err("Fail to connect to server");
+		goto close_out;
+	}
+
+	goto out;
+
+close_out:
+	close(fd);
+	fd = -1;
+out:
+	return fd;
+}
+
+static int validate_map(struct bpf_map *map, int client_fd)
+{
+	__u32 cookie_expected_value;
+	struct sockaddr_in6 addr;
+	socklen_t len = sizeof(addr);
+	__u32 cookie_value;
+	__u64 cookie_key;
+	int err = 0;
+	int map_fd;
+
+	if (!map) {
+		log_err("Map not found in BPF object");
+		goto err;
+	}
+
+	map_fd = bpf_map__fd(map);
+
+	err = bpf_map_get_next_key(map_fd, NULL, &cookie_key);
+	if (err) {
+		log_err("Can't get cookie key from map");
+		goto out;
+	}
+
+	err = bpf_map_lookup_elem(map_fd, &cookie_key, &cookie_value);
+	if (err) {
+		log_err("Can't get cookie value from map");
+		goto out;
+	}
+
+	err = getsockname(client_fd, (struct sockaddr *)&addr, &len);
+	if (err) {
+		log_err("Can't get client local addr");
+		goto out;
+	}
+
+	cookie_expected_value = (ntohs(addr.sin6_port) << 8) | 0xFF;
+	if (cookie_value != cookie_expected_value) {
+		log_err("Unexpected value in map: %x != %x", cookie_value,
+			cookie_expected_value);
+		goto err;
+	}
+
+	goto out;
+err:
+	err = -1;
+out:
+	return err;
+}
+
+static int run_test(int cgfd)
+{
+	enum bpf_attach_type attach_type;
+	struct bpf_prog_load_attr attr;
+	struct bpf_program *prog;
+	struct bpf_object *pobj;
+	const char *prog_name;
+	int server_fd = -1;
+	int client_fd = -1;
+	int prog_fd = -1;
+	int err = 0;
+
+	memset(&attr, 0, sizeof(attr));
+	attr.file = SOCKET_COOKIE_PROG;
+	attr.prog_type = BPF_PROG_TYPE_UNSPEC;
+
+	err = bpf_prog_load_xattr(&attr, &pobj, &prog_fd);
+	if (err) {
+		log_err("Failed to load %s", attr.file);
+		goto out;
+	}
+
+	bpf_object__for_each_program(prog, pobj) {
+		prog_name = bpf_program__title(prog, /*needs_copy*/ false);

tools/testing/selftests/bpf/test_socket_cookie.c new file +48 -0

+	server_fd = start_server();
+	if (server_fd == -1)
+		goto err;
+
+	client_fd = connect_to_server(server_fd);
+	if (client_fd == -1)
+		goto err;
+
+	if (validate_map(bpf_map__next(NULL, pobj), client_fd))
+		goto err;
+
+	goto out;
+err:
+	err = -1;
+out:
+	close(client_fd);
+	close(server_fd);
+	bpf_object__close(pobj);
+	printf("%s\n", err ? "FAILED" : "PASSED");
+	return err;
+}
+
+int main(int argc, char **argv)
+{
+	int cgfd = -1;
+	int err = 0;
+
+	if (setup_cgroup_environment())
+		goto err;
+
+	cgfd = create_and_get_cgroup(CG_PATH);
+	if (!cgfd)
+		goto err;
+
+	if (join_cgroup(CG_PATH))
+		goto err;
+
+	if (run_test(cgfd))
+		goto err;
+
+	goto out;
+err:
+	err = -1;
+out:
+	close(cgfd);
+	cleanup_cgroup_environment();
+	return err;
+}

Quoted 316 lines

Add test to use get_socket_cookie() from BPF programs of types BPF_PROG_TYPE_SOCK_OPS and BPF_PROG_TYPE_CGROUP_SOCK_ADDR.

The test attaches two programs to cgroup, runs TCP server and client in the cgroup and checks that two operations are done properly on client socket when user calls connect(2):

1. In BPF_CGROUP_INET6_CONNECT socket cookie is used as the key to write new value in a map for client socket.

2. In BPF_CGROUP_SOCK_OPS (BPF_SOCK_OPS_TCP_CONNECT_CB callback) the value written in "1." is found by socket cookie, since it's the same socket, and updated.

Finally the test verifies the value in the map.

Signed-off-by Andrey Ignatov <[email protected]>

---
  tools/testing/selftests/bpf/Makefile          |   6 +-
  .../selftests/bpf/socket_cookie_prog.c        |  60 +++++
  .../selftests/bpf/test_socket_cookie.c        | 249 ++++++++++++++++++
  3 files changed, 313 insertions(+), 2 deletions(-)

create mode 100644 tools/testing/selftests/bpf/socket_cookie_prog.c create mode 100644 tools/testing/selftests/bpf/test_socket_cookie.c

tools/testing/selftests/bpf/Makefile +4 -2

index 478bf1bcbbf5..1b28277998e2 100644
@@ -22,7 +22,8 @@ $(TEST_CUSTOM_PROGS): $(OUTPUT)/%: %.c
  # Order correspond to 'make run_tests' order
  TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test_progs \
  	test_align test_verifier_log test_dev_cgroup test_tcpbpf_user \
-	test_sock test_btf test_sockmap test_lirc_mode2_user get_cgroup_id_user
+	test_sock test_btf test_sockmap test_lirc_mode2_user get_cgroup_id_user \
+	test_socket_cookie
  TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test_obj_id.o \
  	test_pkt_md_access.o test_xdp_redirect.o test_xdp_meta.o sockmap_parse_prog.o     \

@@ -33,7 +34,7 @@ TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test
  	test_btf_haskv.o test_btf_nokv.o test_sockmap_kern.o test_tunnel_kern.o \
  	test_get_stack_rawtp.o test_sockmap_kern.o test_sockhash_kern.o \
  	test_lwt_seg6local.o sendmsg4_prog.o sendmsg6_prog.o test_lirc_mode2_kern.o \
-	get_cgroup_id_kern.o
+	get_cgroup_id_kern.o socket_cookie_prog.o
  # Order correspond to 'make run_tests' order
  TEST_PROGS := test_kmod.sh \

@@ -60,6 +61,7 @@ $(TEST_GEN_PROGS_EXTENDED): $(OUTPUT)/libbpf.a
  $(OUTPUT)/test_dev_cgroup: cgroup_helpers.c
  $(OUTPUT)/test_sock: cgroup_helpers.c
  $(OUTPUT)/test_sock_addr: cgroup_helpers.c
+$(OUTPUT)/test_socket_cookie: cgroup_helpers.c
  $(OUTPUT)/test_sockmap: cgroup_helpers.c
  $(OUTPUT)/test_tcpbpf_user: cgroup_helpers.c
  $(OUTPUT)/test_progs: trace_helpers.c

tools/testing/selftests/bpf/socket_cookie_prog.c new file +60 -0

new file mode 100644
index 000000000000..9ff8ac4b0bf6
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <linux/bpf.h>
+#include <sys/socket.h>
+
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+struct bpf_map_def SEC("maps") socket_cookies = {
+	.type = BPF_MAP_TYPE_HASH,
+	.key_size = sizeof(__u64),
+	.value_size = sizeof(__u32),
+	.max_entries = 1 << 8,
+};
+
+SEC("cgroup/connect6")
+int set_cookie(struct bpf_sock_addr *ctx)
+{
+	__u32 cookie_value = 0xFF;
+	__u64 cookie_key;
+
+	if (ctx->family != AF_INET6 || ctx->user_family != AF_INET6)
+		return 1;
+
+	cookie_key = bpf_get_socket_cookie(ctx);
+	if (bpf_map_update_elem(&socket_cookies, &cookie_key, &cookie_value, 0))
+		return 0;
+
+	return 1;
+}
+
+SEC("sockops")
+int update_cookie(struct bpf_sock_ops *ctx)
+{
+	__u32 new_cookie_value;
+	__u32 *cookie_value;
+	__u64 cookie_key;
+
+	if (ctx->family != AF_INET6)
+		return 1;
+
+	if (ctx->op != BPF_SOCK_OPS_TCP_CONNECT_CB)
+		return 1;
+
+	cookie_key = bpf_get_socket_cookie(ctx);
+
+	cookie_value = bpf_map_lookup_elem(&socket_cookies, &cookie_key);
+	if (!cookie_value)
+		return 1;
+
+	new_cookie_value = (ctx->local_port << 8) | *cookie_value;
+	bpf_map_update_elem(&socket_cookies, &cookie_key, &new_cookie_value, 0);
+
+	return 1;
+}
+
+int _version SEC("version") = 1;
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/test_socket_cookie.c new file +190 -0

new file mode 100644
index 000000000000..eed4b3bc9fcd
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <string.h>
+#include <unistd.h>
+
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+
+#include "bpf_rlimit.h"
+#include "cgroup_helpers.h"
+
+#define CG_PATH			"/foo"
+#define SOCKET_COOKIE_PROG	"./socket_cookie_prog.o"
+
+static int attach_type_by_name(const char *prog_name,
+			       enum bpf_attach_type *attach_type)
+{
+	enum bpf_attach_type expected_attach_type;
+	enum bpf_prog_type prog_type;
+	int err = 0;
+
+	err = libbpf_prog_type_by_name(prog_name, &prog_type,
+				       &expected_attach_type);
+	if (err) {
+		log_err("Failed to get type for prog %s", prog_name);
+		goto out;
+	}
+
+	if (expected_attach_type) {
+		*attach_type = expected_attach_type;
+		goto out;
+	}
+
+	switch (prog_type) {
+	case BPF_PROG_TYPE_SOCK_OPS:
+		*attach_type = BPF_CGROUP_SOCK_OPS;
+		break;
+	default:
+		log_err("Can't detect attach type for prog %s", prog_name);
+		err = -1;
+	}
+out:
+	return err;
+}
+
+static int start_server(void)
+{
+	struct sockaddr_in6 addr;
+	int fd;
+
+	fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (fd == -1) {
+		log_err("Failed to create server socket");
+		goto out;
+	}
+
+	memset(&addr, 0, sizeof(addr));
+	addr.sin6_family = AF_INET6;
+	addr.sin6_addr = in6addr_loopback;
+	addr.sin6_port = 0;
+
+	if (bind(fd, (const struct sockaddr *)&addr, sizeof(addr)) == -1) {
+		log_err("Failed to bind server socket");
+		goto close_out;
+	}
+
+	if (listen(fd, 128) == -1) {
+		log_err("Failed to listen on server socket");
+		goto close_out;
+	}
+
+	goto out;
+
+close_out:
+	close(fd);
+	fd = -1;
+out:
+	return fd;
+}
+
+static int connect_to_server(int server_fd)
+{
+	struct sockaddr_storage addr;
+	socklen_t len = sizeof(addr);
+	int fd;
+
+	fd = socket(AF_INET6, SOCK_STREAM, 0);
+	if (fd == -1) {
+		log_err("Failed to create client socket");
+		goto out;
+	}
+
+	if (getsockname(server_fd, (struct sockaddr *)&addr, &len)) {
+		log_err("Failed to get server addr");
+		goto close_out;
+	}
+
+	if (connect(fd, (const struct sockaddr *)&addr, len) == -1) {
+		log_err("Fail to connect to server");
+		goto close_out;
+	}
+
+	goto out;
+
+close_out:
+	close(fd);
+	fd = -1;
+out:
+	return fd;
+}
+
+static int validate_map(struct bpf_map *map, int client_fd)
+{
+	__u32 cookie_expected_value;
+	struct sockaddr_in6 addr;
+	socklen_t len = sizeof(addr);
+	__u32 cookie_value;
+	__u64 cookie_key;
+	int err = 0;
+	int map_fd;
+
+	if (!map) {
+		log_err("Map not found in BPF object");
+		goto err;
+	}
+
+	map_fd = bpf_map__fd(map);
+
+	err = bpf_map_get_next_key(map_fd, NULL, &cookie_key);
+	if (err) {
+		log_err("Can't get cookie key from map");
+		goto out;
+	}
+
+	err = bpf_map_lookup_elem(map_fd, &cookie_key, &cookie_value);
+	if (err) {
+		log_err("Can't get cookie value from map");
+		goto out;
+	}
+
+	err = getsockname(client_fd, (struct sockaddr *)&addr, &len);
+	if (err) {
+		log_err("Can't get client local addr");
+		goto out;
+	}
+
+	cookie_expected_value = (ntohs(addr.sin6_port) << 8) | 0xFF;
+	if (cookie_value != cookie_expected_value) {
+		log_err("Unexpected value in map: %x != %x", cookie_value,
+			cookie_expected_value);
+		goto err;
+	}
+
+	goto out;
+err:
+	err = -1;
+out:
+	return err;
+}
+
+static int run_test(int cgfd)
+{
+	enum bpf_attach_type attach_type;
+	struct bpf_prog_load_attr attr;
+	struct bpf_program *prog;
+	struct bpf_object *pobj;
+	const char *prog_name;
+	int server_fd = -1;
+	int client_fd = -1;
+	int prog_fd = -1;
+	int err = 0;
+
+	memset(&attr, 0, sizeof(attr));
+	attr.file = SOCKET_COOKIE_PROG;
+	attr.prog_type = BPF_PROG_TYPE_UNSPEC;
+
+	err = bpf_prog_load_xattr(&attr, &pobj, &prog_fd);
+	if (err) {
+		log_err("Failed to load %s", attr.file);
+		goto out;
+	}
+
+	bpf_object__for_each_program(prog, pobj) {
+		prog_name = bpf_program__title(prog, /*needs_copy*/ false);

tools/testing/selftests/bpf/test_socket_cookie.c line 200

Quoted 10 lines

tools/testing/selftests/bpf/test_socket_cookie.c new file +10 -0

+		err = attach_type_by_name(prog_name, &attach_type);
+		if (err)
+			goto out;
+		err = bpf_prog_attach(bpf_program__fd(prog), cgfd, attach_type,
+				      BPF_F_ALLOW_OVERRIDE);
+		if (err) {
+			log_err("Failed to attach prog %s", prog_name);
+			goto out;
+		}
+	}

Tested and the program runs correctly in my FC27 environment. I kind of feel that the above attach program and attach_type_by_name are a little bit complicated since we only have two programs here.

There is a API in libbpf called bpf_object__find_program_by_title, which can be used to find the program based on program section name. Could this be used to simplify the program load/attachment logic here?

Quoted 49 lines

tools/testing/selftests/bpf/test_socket_cookie.c new file +48 -0

+	server_fd = start_server();
+	if (server_fd == -1)
+		goto err;
+
+	client_fd = connect_to_server(server_fd);
+	if (client_fd == -1)
+		goto err;
+
+	if (validate_map(bpf_map__next(NULL, pobj), client_fd))
+		goto err;
+
+	goto out;
+err:
+	err = -1;
+out:
+	close(client_fd);
+	close(server_fd);
+	bpf_object__close(pobj);
+	printf("%s\n", err ? "FAILED" : "PASSED");
+	return err;
+}
+
+int main(int argc, char **argv)
+{
+	int cgfd = -1;
+	int err = 0;
+
+	if (setup_cgroup_environment())
+		goto err;
+
+	cgfd = create_and_get_cgroup(CG_PATH);
+	if (!cgfd)
+		goto err;
+
+	if (join_cgroup(CG_PATH))
+		goto err;
+
+	if (run_test(cgfd))
+		goto err;
+
+	goto out;
+err:
+	err = -1;
+out:
+	close(cgfd);
+	cleanup_cgroup_environment();
+	return err;
+}