[PATCH bpf-next v3 3/5] selftests/bpf: Add ksock kfunc test

Add a selftest that exercises the ksock kfuncs end-to-end. One syscall
bpf setup program creates a ksock context and connects the socket.
Another syscall bpf program looks up the context and send test data.
The userspace harness creates a network namespace and a new socket on
loopback, run the setup and send syscall bpf progs then check that the
userspace socket received the data from bpf.

Signed-off-by: Mahe Tardy <[email protected]>
---
 .../testing/selftests/bpf/prog_tests/ksock.c  | 159 ++++++++++++++++++
 .../testing/selftests/bpf/progs/ksock_basic.c |  68 ++++++++
 .../selftests/bpf/progs/ksock_common.h        |  61 +++++++
 3 files changed, 288 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/ksock.c
 create mode 100644 tools/testing/selftests/bpf/progs/ksock_basic.c
 create mode 100644 tools/testing/selftests/bpf/progs/ksock_common.h

diff --git a/tools/testing/selftests/bpf/prog_tests/ksock.c b/tools/testing/selftests/bpf/prog_tests/ksock.c
new file mode 100644
index 000000000000..fb88eac9eeba
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/ksock.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Isovalent */
+
+#include <arpa/inet.h>
+
+#include "test_progs.h"
+#include "network_helpers.h"
+#include "ksock_basic.skel.h"
+
+#define NS_TEST "ksock_basic_ns"
+#define LOOPBACK_IP "127.0.0.1"
+#define RECV_PORT 7777
+#define RECV_TIMEOUT_SEC 5
+
+struct ksock_test_env {
+	const char *netns;
+	bool netns_created;
+	struct nstoken *nstoken;
+	struct sockaddr_in addr;
+	int rfd;
+	char buf[32];
+};
+
+static bool ksock_test_env_setup(struct ksock_test_env *env, const char *netns)
+{
+	struct timeval tv;
+	int err;
+
+	memset(env, 0, sizeof(*env));
+	env->netns = netns;
+	env->rfd = -1;
+
+	SYS(fail, "ip netns add %s", netns);
+	env->netns_created = true;
+	SYS(fail, "ip -net %s link set lo up", netns);
+
+	env->nstoken = open_netns(netns);
+	if (!ASSERT_OK_PTR(env->nstoken, "open_netns"))
+		goto fail;
+
+	env->rfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+	if (!ASSERT_OK_FD(env->rfd, "receiver socket"))
+		goto fail;
+
+	env->addr.sin_family = AF_INET;
+	env->addr.sin_addr.s_addr = inet_addr(LOOPBACK_IP);
+	env->addr.sin_port = htons(RECV_PORT);
+
+	err = bind(env->rfd, (struct sockaddr *)&env->addr, sizeof(env->addr));
+	if (!ASSERT_OK(err, "bind receiver"))
+		goto fail;
+
+	tv.tv_sec = RECV_TIMEOUT_SEC;
+	tv.tv_usec = 0;
+	err = setsockopt(env->rfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
+	if (!ASSERT_OK(err, "set rcvtimeo"))
+		goto fail;
+
+	return true;
+
+fail:
+	if (env->rfd >= 0) {
+		close(env->rfd);
+		env->rfd = -1;
+	}
+	if (env->nstoken) {
+		close_netns(env->nstoken);
+		env->nstoken = NULL;
+	}
+	if (env->netns_created) {
+		SYS_NOFAIL("ip netns del %s >/dev/null 2>&1", netns);
+		env->netns_created = false;
+	}
+	return false;
+}
+
+static void ksock_test_env_cleanup(struct ksock_test_env *env)
+{
+	if (env->rfd >= 0)
+		close(env->rfd);
+	if (env->nstoken)
+		close_netns(env->nstoken);
+	if (env->netns_created) {
+		SYS_NOFAIL("ip netns del %s >/dev/null 2>&1", env->netns);
+		env->netns_created = false;
+	}
+}
+
+static void ksock_assert_recv(struct ksock_test_env *env, const char *data,
+			      size_t data_sz)
+{
+	ssize_t n;
+
+	memset(env->buf, 0, sizeof(env->buf));
+	n = recvfrom(env->rfd, env->buf, sizeof(env->buf), 0, NULL, NULL);
+	if (!ASSERT_EQ(n, data_sz, "recvfrom len"))
+		return;
+	ASSERT_MEMEQ(env->buf, data, data_sz, "payload match");
+}
+
+static bool ksock_setup_ctx(struct ksock_basic *skel)
+{
+	LIBBPF_OPTS(bpf_test_run_opts, opts);
+	int err, pfd;
+
+	skel->bss->ipv4_remote = inet_addr(LOOPBACK_IP);
+	skel->bss->remote_port = RECV_PORT;
+
+	pfd = bpf_program__fd(skel->progs.ksock_setup);
+	err = bpf_prog_test_run_opts(pfd, &opts);
+	if (!ASSERT_OK(err, "ksock_setup run"))
+		return false;
+	if (!ASSERT_OK(opts.retval, "ksock_setup retval"))
+		return false;
+
+	return true;
+}
+
+void test_ksock_basic(void)
+{
+	LIBBPF_OPTS(bpf_test_run_opts, opts);
+	struct ksock_test_env env;
+	struct ksock_basic *skel;
+	int err, pfd;
+
+	skel = ksock_basic__open();
+	if (!ASSERT_OK_PTR(skel, "skel open"))
+		return;
+
+	err = ksock_basic__load(skel);
+	if (!ASSERT_OK(err, "skel load")) {
+		ksock_basic__destroy(skel);
+		return;
+	}
+
+	if (!ksock_test_env_setup(&env, NS_TEST))
+		goto fail;
+
+	/* Step 1: Run the setup SYSCALL prog to create ksock */
+	if (!ksock_setup_ctx(skel))
+		goto fail;
+
+	/* Step 2: Run the send SYSCALL prog */
+	pfd = bpf_program__fd(skel->progs.ksock_send);
+	err = bpf_prog_test_run_opts(pfd, &opts);
+	if (!ASSERT_OK(err, "ksock_send run"))
+		goto fail;
+	if (!ASSERT_EQ(opts.retval, sizeof(skel->data->send_data),
+		       "sendmsg bytes"))
+		goto fail;
+
+	/* Step 3: Receive and verify the data */
+	ksock_assert_recv(&env, skel->data->send_data,
+			  sizeof(skel->data->send_data));
+
+fail:
+	ksock_test_env_cleanup(&env);
+	ksock_basic__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/ksock_basic.c b/tools/testing/selftests/bpf/progs/ksock_basic.c
new file mode 100644
index 000000000000..c18dcc2ea37b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/ksock_basic.c
@@ -0,0 +1,68 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Isovalent */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_endian.h>
+#include "bpf_tracing_net.h"
+#include "ksock_common.h"
+
+__be32 ipv4_remote;
+__u16 remote_port;
+
+char send_data[32] = "hello from bpf ksock";
+
+SEC("syscall")
+int ksock_setup(void *ctx)
+{
+	struct bpf_ksock_create_opts create_opts = {};
+	union bpf_ksock_addr addr = {};
+	struct bpf_ksock *ks;
+	int err = 0;
+
+	create_opts.family = AF_INET;
+	create_opts.type = SOCK_DGRAM;
+	create_opts.protocol = IPPROTO_UDP;
+
+	ks = bpf_ksock_create(&create_opts, sizeof(create_opts), &err);
+	if (!ks)
+		return err;
+
+	addr.sin.sin_family = AF_INET;
+	addr.sin.sin_port = bpf_htons(remote_port);
+	addr.sin.sin_addr.s_addr = ipv4_remote;
+
+	err = bpf_ksock_connect(ks, &addr, sizeof(addr));
+	if (err) {
+		bpf_ksock_release(ks);
+		return err;
+	}
+
+	err = ksock_ctx_insert(ks);
+	if (err && err != -EEXIST)
+		return err;
+	return 0;
+}
+
+SEC("syscall")
+int ksock_send(void *ctx)
+{
+	struct __ksock_ctx_value *v;
+	struct bpf_ksock *ks;
+	int send = -1;
+
+	v = ksock_ctx_value_lookup();
+	if (!v)
+		return -ENOENT;
+
+	ks = bpf_kptr_xchg(&v->ctx, NULL);
+	if (!ks)
+		return -ENOENT;
+
+	send = bpf_ksock_send(ks, send_data, sizeof(send_data));
+	bpf_ksock_release(ks);
+	return send;
+}
+
+char __license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/ksock_common.h b/tools/testing/selftests/bpf/progs/ksock_common.h
new file mode 100644
index 000000000000..6e5b5b089124
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/ksock_common.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) 2026 Isovalent */
+
+#ifndef _KSOCK_COMMON_H
+#define _KSOCK_COMMON_H
+
+#include "errno.h"
+#include <stdbool.h>
+
+#define SOCK_STREAM	1
+#define SOCK_DGRAM	2
+#define IPPROTO_TCP	6
+#define IPPROTO_UDP	17
+
+struct bpf_ksock *bpf_ksock_create(const struct bpf_ksock_create_opts *opts,
+				   u32 opts__sz, int *err__uninit) __ksym;
+int bpf_ksock_connect(struct bpf_ksock *ks, const union bpf_ksock_addr *addr,
+		      u32 addr__sz) __ksym;
+struct bpf_ksock *bpf_ksock_acquire(struct bpf_ksock *ks) __ksym;
+void bpf_ksock_release(struct bpf_ksock *ks) __ksym;
+int bpf_ksock_send(struct bpf_ksock *ks, const void *data, u32 data__sz) __ksym;
+
+struct __ksock_ctx_value {
+	struct bpf_ksock __kptr * ctx;
+};
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__type(key, int);
+	__type(value, struct __ksock_ctx_value);
+	__uint(max_entries, 1);
+} __ksock_ctx_map SEC(".maps");
+
+static inline struct __ksock_ctx_value *ksock_ctx_value_lookup(void)
+{
+	u32 key = 0;
+
+	return bpf_map_lookup_elem(&__ksock_ctx_map, &key);
+}
+
+static inline int ksock_ctx_insert(struct bpf_ksock *ctx)
+{
+	struct __ksock_ctx_value *v;
+	struct bpf_ksock *old;
+
+	v = ksock_ctx_value_lookup();
+	if (!v) {
+		bpf_ksock_release(ctx);
+		return -ENOENT;
+	}
+
+	old = bpf_kptr_xchg(&v->ctx, ctx);
+	if (old) {
+		bpf_ksock_release(old);
+		return -EEXIST;
+	}
+
+	return 0;
+}
+
+#endif /* _KSOCK_COMMON_H */
--
2.34.1