selftests/bpf: add splice_read tests for sockmap

Add splice_read coverage to sockmap_basic and sockmap_strp selftests.
Each test suite now runs twice: once with normal recv_timeout() and
once with splice-based reads, verifying that data read via splice(2)
through a pipe produces identical results.

A recv_timeout_with_splice() helper is added to sockmap_helpers.h
that creates a temporary pipe, splices data from the socket into
the pipe, then reads from the pipe into the user buffer. MSG_PEEK
calls fall back to native recv since splice does not support peek.
Non-TCP sockets also fall back to native recv.

The splice subtests are distinguished by appending " splice" to
each subtest name via a test__start_subtest macro override.

./test_progs -a sockmap_*
...
Summary: 5/830 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>

Author: mrpre

tools/testing/selftests/bpf/prog_tests/sockmap_basic.c

@@ -18,6 +18,23 @@
 
 #include "sockmap_helpers.h"
 
+static bool use_splice;
+
+static bool __start_subtest(const char *name)
+{
+	if (!use_splice)
+		return (test__start_subtest)(name);
+
+	char buf[MAX_TEST_NAME];
+
+	snprintf(buf, sizeof(buf), "%s splice", name);
+	return (test__start_subtest)(buf);
+}
+
+#define test__start_subtest(name) __start_subtest(name)
+#define recv_timeout(fd, buf, len, flags, timeout) \
+	recv_timeout_with_splice(fd, buf, len, flags, timeout, use_splice)
+
 #define TCP_REPAIR		19	/* TCP sock is under repair right now */
 
 #define TCP_REPAIR_ON		1
@@ -1314,7 +1331,7 @@ static void test_sockmap_multi_channels(int sotype)
 	test_sockmap_pass_prog__destroy(skel);
 }
 
-void test_sockmap_basic(void)
+static void __test_sockmap_basic(void)
 {
 	if (test__start_subtest("sockmap create_update_free"))
 		test_sockmap_create_update_free(BPF_MAP_TYPE_SOCKMAP);
@@ -1391,3 +1408,12 @@ void test_sockmap_basic(void)
 	if (test__start_subtest("sockmap udp multi channels"))
 		test_sockmap_multi_channels(SOCK_DGRAM);
 }
+
+void test_sockmap_basic(void)
+{
+	use_splice = false;
+	__test_sockmap_basic();
+
+	use_splice = true;
+	__test_sockmap_basic();
+}

tools/testing/selftests/bpf/prog_tests/sockmap_helpers.h

@@ -80,4 +80,66 @@ static inline int add_to_sockmap(int mapfd, int fd1, int fd2)
 	return xbpf_map_update_elem(mapfd, &u32(1), &u64(fd2), BPF_NOEXIST);
 }
 
+static inline ssize_t recv_timeout_with_splice(int fd, void *buf, size_t len,
+					       int flags,
+					       unsigned int timeout_sec,
+					       bool do_splice)
+{
+	ssize_t total = 0;
+	int pipefd[2];
+	int fl;
+
+	int sotype, protocol;
+	socklen_t optlen = sizeof(sotype);
+
+	if (!do_splice || (flags & MSG_PEEK) ||
+	    getsockopt(fd, SOL_SOCKET, SO_TYPE, &sotype, &optlen) ||
+	    sotype != SOCK_STREAM ||
+	    getsockopt(fd, SOL_SOCKET, SO_PROTOCOL, &protocol, &optlen) ||
+	    protocol != IPPROTO_TCP)
+		return recv_timeout(fd, buf, len, flags, timeout_sec);
+
+	if (poll_read(fd, timeout_sec))
+		return -1;
+
+	if (pipe(pipefd) < 0)
+		return -1;
+
+	/*
+	 * tcp_splice_read() only checks sock->file->f_flags for
+	 * O_NONBLOCK, ignoring SPLICE_F_NONBLOCK for the socket
+	 * side timeout. Set O_NONBLOCK on the fd so the loop won't
+	 * block forever when no more data is available.
+	 */
+	fl = fcntl(fd, F_GETFL);
+	fcntl(fd, F_SETFL, fl | O_NONBLOCK);
+
+	/*
+	 * Pipe has limited buffer slots (default 16), so a single
+	 * splice may not transfer all requested bytes. Loop until
+	 * we've read enough or no more data is available.
+	 */
+	while (total < (ssize_t)len) {
+		ssize_t spliced, n;
+
+		spliced = splice(fd, NULL, pipefd[1], NULL, len - total,
+				 SPLICE_F_NONBLOCK);
+		if (spliced <= 0)
+			break;
+
+		n = read(pipefd[0], buf + total, spliced);
+		if (n <= 0)
+			break;
+
+		total += n;
+	}
+
+	fcntl(fd, F_SETFL, fl);
+
+	close(pipefd[0]);
+	close(pipefd[1]);
+
+	return total > 0 ? total : -1;
+}
+
 #endif // __SOCKMAP_HELPERS__

tools/testing/selftests/bpf/prog_tests/sockmap_strp.c

@@ -6,6 +6,23 @@
 #include "test_skmsg_load_helpers.skel.h"
 #include "test_sockmap_strp.skel.h"
 
+static bool use_splice;
+
+static bool __start_subtest(const char *name)
+{
+	if (!use_splice)
+		return (test__start_subtest)(name);
+
+	char buf[MAX_TEST_NAME];
+
+	snprintf(buf, sizeof(buf), "%s splice", name);
+	return (test__start_subtest)(buf);
+}
+
+#define test__start_subtest(name) __start_subtest(name)
+#define recv_timeout(fd, buf, len, flags, timeout) \
+	recv_timeout_with_splice(fd, buf, len, flags, timeout, use_splice)
+
 #define STRP_PKT_HEAD_LEN 4
 #define STRP_PKT_BODY_LEN 6
 #define STRP_PKT_FULL_LEN (STRP_PKT_HEAD_LEN + STRP_PKT_BODY_LEN)
@@ -431,7 +448,7 @@ static void test_sockmap_strp_verdict(int family, int sotype)
 	test_sockmap_strp__destroy(strp);
 }
 
-void test_sockmap_strp(void)
+static void __test_sockmap_strp(void)
 {
 	if (test__start_subtest("sockmap strp tcp pass"))
 		test_sockmap_strp_pass(AF_INET, SOCK_STREAM, false);
@@ -452,3 +469,12 @@ void test_sockmap_strp(void)
 	if (test__start_subtest("sockmap strp tcp dispatch"))
 		test_sockmap_strp_dispatch_pkt(AF_INET, SOCK_STREAM);
 }
+
+void test_sockmap_strp(void)
+{
+	use_splice = false;
+	__test_sockmap_strp();
+
+	use_splice = true;
+	__test_sockmap_strp();
+}