Subject: [PATCH bpf-next v2 2/4] bpf: sockmap, add a sendmsg test so we can check that path

From: John Fastabend <[email-masked]>
Date: Wed, 24 Jan 2024 10:54:01 -0800

Sendmsg path with multiple buffers is slightly different from a single
send in how we have to handle and walk the sg when doing pops. Lets
ensure this walk is correct.

Signed-off-by: John Fastabend <[email-masked]>
---
 .../bpf/prog_tests/sockmap_helpers.h          |  8 +++
 .../bpf/prog_tests/sockmap_msg_helpers.c      | 53 +++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_helpers.h b/tools/testing/selftests/bpf/prog_tests/sockmap_helpers.h
index 781cbdf01d7b..4d8d24482032 100644
--- a/tools/testing/selftests/bpf/prog_tests/sockmap_helpers.h
+++ b/tools/testing/selftests/bpf/prog_tests/sockmap_helpers.h
@@ -103,6 +103,14 @@
 		__ret;                                                         \
 	})
 
+#define xsendmsg(fd, msg, flags)                                               \
+	({                                                                     \
+		ssize_t __ret = sendmsg((fd), (msg), (flags));                 \
+		if (__ret == -1)                                               \
+			FAIL_ERRNO("sendmsg");                                 \
+		__ret;                                                         \
+	})
+
 #define xrecv_nonblock(fd, buf, len, flags)                                    \
 	({                                                                     \
 		ssize_t __ret = recv_timeout((fd), (buf), (len), (flags),      \
diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_msg_helpers.c b/tools/testing/selftests/bpf/prog_tests/sockmap_msg_helpers.c
index 9ffe02f45808..e5e618e84950 100644
--- a/tools/testing/selftests/bpf/prog_tests/sockmap_msg_helpers.c
+++ b/tools/testing/selftests/bpf/prog_tests/sockmap_msg_helpers.c
@@ -52,6 +52,50 @@ static void pop_simple_send(struct msg_test_opts *opts, int start, int len)
 	ASSERT_OK(cmp, "pop cmp end bytes failed");
 }
 
+static void pop_complex_send(struct msg_test_opts *opts, int start, int len)
+{
+	struct test_sockmap_msg_helpers *skel = opts->skel;
+	char buf[] = "abcdefghijklmnopqrstuvwxyz";
+	size_t sent, recv, total = 0;
+	struct msghdr msg = {0};
+	struct iovec iov[15];
+	char *recvbuf;
+	int i;
+
+	for (i = 0; i < 15; i++) {
+		iov[i].iov_base = buf;
+		iov[i].iov_len = sizeof(buf);
+		total += sizeof(buf);
+	}
+
+	recvbuf = malloc(total);
+	if (!recvbuf)
+		FAIL("pop complex send malloc failure\n");
+
+	msg.msg_iov = iov;
+	msg.msg_iovlen = 15;
+
+	skel->bss->pop = true;
+
+	if (start == -1)
+		start = sizeof(buf) - len - 1;
+
+	skel->bss->pop_start = start;
+	skel->bss->pop_len = len;
+
+	sent = xsendmsg(opts->client, &msg, 0);
+	if (sent != total)
+		FAIL("xsend failed");
+
+	ASSERT_OK(skel->bss->err, "pop error");
+
+	recv = xrecv_nonblock(opts->server, recvbuf, total, 0);
+	if (recv != sent - skel->bss->pop_len)
+		FAIL("Received incorrect number number of bytes after pop");
+
+	free(recvbuf);
+}
+
 static void test_sockmap_pop(void)
 {
 	struct msg_test_opts opts;
@@ -92,6 +136,15 @@ static void test_sockmap_pop(void)
 	/* Pop from end */
 	pop_simple_send(&opts, POP_END, 5);
 
+	/* Empty pop from start of sendmsg */
+	pop_complex_send(&opts, 0, 0);
+	/* Pop from start of sendmsg */
+	pop_complex_send(&opts, 0, 10);
+	/* Pop from middle of sendmsg */
+	pop_complex_send(&opts, 100, 10);
+	/* Pop from end of sendmsg */
+	pop_complex_send(&opts, 394, 10);
+
 close_sockets:
 	close(client);
 	close(server);
-- 
2.33.0