selftests/bpf: Improve connect_force_port test reliability

The connect_force_port test fails intermittently in CI because the
hardcoded server ports (60123/60124) may already be in use by other
tests or processes [1].

Fix this by passing port 0 to start_server(), letting the kernel assign
a free port dynamically. The actual assigned port is then propagated to
the BPF programs by writing it into the .bss map's initial value (via
bpf_map__initial_value()) before loading, so the BPF programs use the
correct backend port at runtime.

[1] https://github.com/kernel-patches/bpf/actions/runs/22697676317/job/65808536038

Suggested-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Varun R Mallya <varunrmallya@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Sun Jian <sun.jian.kdev@gmail.com>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://patch.msgid.link/20260323081131.65604-1-varunrmallya@gmail.com

diff --git a/tools/testing/selftests/bpf/prog_tests/connect_force_port.c b/tools/testing/selftests/bpf/prog_tests/connect_force_port.c
index 24d553109f8dd0fd369eb3287c3b22bec8f1721e..dfb7f6cf3ee14c7b29baf83ed4ef3eb84e0e9a1d 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/connect_force_port.c
+++ b/tools/testing/selftests/bpf/prog_tests/connect_force_port.c
@@ -53,6 +53,9 @@ static int run_test(int cgroup_fd, int server_fd, int family, int type)
        __u16 expected_peer_port = 60000;
        struct bpf_program *prog;
        struct bpf_object *obj;
+       struct bpf_map *map;
+       __u16 *port_ptr;
+       size_t port_size;
        const char *obj_file = v4 ? "connect_force_port4.bpf.o" : "connect_force_port6.bpf.o";
        int fd, err;
        __u32 duration = 0;
@@ -61,6 +64,21 @@ static int run_test(int cgroup_fd, int server_fd, int family, int type)
        if (!ASSERT_OK_PTR(obj, "bpf_obj_open"))
                return -1;
 
+       map = bpf_object__find_map_by_name(obj, ".bss");
+       if (!ASSERT_OK_PTR(map, "find bss map")) {
+               err = -EIO;
+               goto close_bpf_object;
+       }
+
+       port_ptr = bpf_map__initial_value(map, &port_size);
+       if (!ASSERT_OK_PTR(port_ptr, "get bss initial value")) {
+               err = -EIO;
+               goto close_bpf_object;
+       }
+
+       /* Auto assigns the port according to availability */
+       *port_ptr = ntohs(get_socket_local_port(server_fd));
+
        err = bpf_object__load(obj);
        if (!ASSERT_OK(err, "bpf_obj_load")) {
                err = -EIO;
@@ -138,25 +156,25 @@ void test_connect_force_port(void)
        if (CHECK_FAIL(cgroup_fd < 0))
                return;
 
-       server_fd = start_server(AF_INET, SOCK_STREAM, NULL, 60123, 0);
+       server_fd = start_server(AF_INET, SOCK_STREAM, NULL, 0, 0);
        if (CHECK_FAIL(server_fd < 0))
                goto close_cgroup_fd;
        CHECK_FAIL(run_test(cgroup_fd, server_fd, AF_INET, SOCK_STREAM));
        close(server_fd);
 
-       server_fd = start_server(AF_INET6, SOCK_STREAM, NULL, 60124, 0);
+       server_fd = start_server(AF_INET6, SOCK_STREAM, NULL, 0, 0);
        if (CHECK_FAIL(server_fd < 0))
                goto close_cgroup_fd;
        CHECK_FAIL(run_test(cgroup_fd, server_fd, AF_INET6, SOCK_STREAM));
        close(server_fd);
 
-       server_fd = start_server(AF_INET, SOCK_DGRAM, NULL, 60123, 0);
+       server_fd = start_server(AF_INET, SOCK_DGRAM, NULL, 0, 0);
        if (CHECK_FAIL(server_fd < 0))
                goto close_cgroup_fd;
        CHECK_FAIL(run_test(cgroup_fd, server_fd, AF_INET, SOCK_DGRAM));
        close(server_fd);
 
-       server_fd = start_server(AF_INET6, SOCK_DGRAM, NULL, 60124, 0);
+       server_fd = start_server(AF_INET6, SOCK_DGRAM, NULL, 0, 0);
        if (CHECK_FAIL(server_fd < 0))
                goto close_cgroup_fd;
        CHECK_FAIL(run_test(cgroup_fd, server_fd, AF_INET6, SOCK_DGRAM));

diff --git a/tools/testing/selftests/bpf/progs/connect_force_port4.c b/tools/testing/selftests/bpf/progs/connect_force_port4.c
index 27a632dd382e00ff051ce097d8d0e994a0df767c..d5be6a559d6a1d86c6d983875528b4b06c669aba 100644 (file)
--- a/tools/testing/selftests/bpf/progs/connect_force_port4.c
+++ b/tools/testing/selftests/bpf/progs/connect_force_port4.c
@@ -14,6 +14,8 @@
 
 char _license[] SEC("license") = "GPL";
 
+__u16 port = 0;
+
 struct svc_addr {
        __be32 addr;
        __be16 port;
@@ -40,7 +42,7 @@ int connect4(struct bpf_sock_addr *ctx)
        if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
                return 0;
 
-       /* Rewire service 1.2.3.4:60000 to backend 127.0.0.1:60123. */
+       /* Rewire service 1.2.3.4:60000 to backend 127.0.0.1:port. */
        if (ctx->user_port == bpf_htons(60000)) {
                orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0,
                                          BPF_SK_STORAGE_GET_F_CREATE);
@@ -51,7 +53,7 @@ int connect4(struct bpf_sock_addr *ctx)
                orig->port = ctx->user_port;
 
                ctx->user_ip4 = bpf_htonl(0x7f000001);
-               ctx->user_port = bpf_htons(60123);
+               ctx->user_port = bpf_htons(port);
        }
        return 1;
 }
@@ -63,7 +65,7 @@ int getsockname4(struct bpf_sock_addr *ctx)
                return 1;
 
        /* Expose local server as 1.2.3.4:60000 to client. */
-       if (ctx->user_port == bpf_htons(60123)) {
+       if (ctx->user_port == bpf_htons(port)) {
                ctx->user_ip4 = bpf_htonl(0x01020304);
                ctx->user_port = bpf_htons(60000);
        }
@@ -79,7 +81,7 @@ int getpeername4(struct bpf_sock_addr *ctx)
                return 1;
 
        /* Expose service 1.2.3.4:60000 as peer instead of backend. */
-       if (ctx->user_port == bpf_htons(60123)) {
+       if (ctx->user_port == bpf_htons(port)) {
                orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0, 0);
                if (orig) {
                        ctx->user_ip4 = orig->addr;

diff --git a/tools/testing/selftests/bpf/progs/connect_force_port6.c b/tools/testing/selftests/bpf/progs/connect_force_port6.c
index 19cad93e612fc53f0440cc7259928b7d1e9b2491..a1a671b390831a48275a3c7d8dcc450ec215391e 100644 (file)
--- a/tools/testing/selftests/bpf/progs/connect_force_port6.c
+++ b/tools/testing/selftests/bpf/progs/connect_force_port6.c
@@ -13,6 +13,8 @@
 
 char _license[] SEC("license") = "GPL";
 
+__u16 port = 0;
+
 struct svc_addr {
        __be32 addr[4];
        __be16 port;
@@ -39,7 +41,7 @@ int connect6(struct bpf_sock_addr *ctx)
        if (bpf_bind(ctx, (struct sockaddr *)&sa, sizeof(sa)) != 0)
                return 0;
 
-       /* Rewire service [fc00::1]:60000 to backend [::1]:60124. */
+       /* Rewire service [fc00::1]:60000 to backend [::1]:port. */
        if (ctx->user_port == bpf_htons(60000)) {
                orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0,
                                          BPF_SK_STORAGE_GET_F_CREATE);
@@ -56,7 +58,7 @@ int connect6(struct bpf_sock_addr *ctx)
                ctx->user_ip6[1] = 0;
                ctx->user_ip6[2] = 0;
                ctx->user_ip6[3] = bpf_htonl(1);
-               ctx->user_port = bpf_htons(60124);
+               ctx->user_port = bpf_htons(port);
        }
        return 1;
 }
@@ -68,7 +70,7 @@ int getsockname6(struct bpf_sock_addr *ctx)
                return 1;
 
        /* Expose local server as [fc00::1]:60000 to client. */
-       if (ctx->user_port == bpf_htons(60124)) {
+       if (ctx->user_port == bpf_htons(port)) {
                ctx->user_ip6[0] = bpf_htonl(0xfc000000);
                ctx->user_ip6[1] = 0;
                ctx->user_ip6[2] = 0;
@@ -87,7 +89,7 @@ int getpeername6(struct bpf_sock_addr *ctx)
                return 1;
 
        /* Expose service [fc00::1]:60000 as peer instead of backend. */
-       if (ctx->user_port == bpf_htons(60124)) {
+       if (ctx->user_port == bpf_htons(port)) {
                orig = bpf_sk_storage_get(&service_mapping, ctx->sk, 0, 0);
                if (orig) {
                        ctx->user_ip6[0] = orig->addr[0];