[RFC PATCH v1 2/2] vsock/test: SO_RCVLOWAT + deferred credit update test

[Arseniy Krasnov <avkrasnov@salutedevices.com>]

This adds test which checks, that updating SO_RCVLOWAT value also sends
credit update message. Otherwise mutual hungup may happen when receiver
didn't send credit update and then calls 'poll()' with non default
SO_RCVLOWAT value (e.g. waiting enough bytes to read), while sender
waits for free space at receiver's side.

Signed-off-by: Arseniy Krasnov <avkrasnov@salutedevices.com>
---
 tools/testing/vsock/vsock_test.c | 131 +++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)

diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index c1f7bc9abd22..c71b3875fd16 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -1180,6 +1180,132 @@ static void test_stream_shutrd_server(const struct test_opts *opts)
 	close(fd);
 }
 
+#define RCVLOWAT_CREDIT_UPD_BUF_SIZE	(1024 * 128)
+#define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE	(1024 * 64)
+
+static void test_stream_rcvlowat_def_cred_upd_client(const struct test_opts *opts)
+{
+	size_t buf_size;
+	void *buf;
+	int fd;
+
+	fd = vsock_stream_connect(opts->peer_cid, 1234);
+	if (fd < 0) {
+		perror("connect");
+		exit(EXIT_FAILURE);
+	}
+
+	/* Send 1 byte more than peer's buffer size. */
+	buf_size = RCVLOWAT_CREDIT_UPD_BUF_SIZE + 1;
+
+	buf = malloc(buf_size);
+	if (!buf) {
+		perror("malloc");
+		exit(EXIT_FAILURE);
+	}
+
+	/* Wait until peer sets needed buffer size. */
+	control_expectln("SRVREADY");
+
+	if (send(fd, buf, buf_size, 0) != buf_size) {
+		perror("send failed");
+		exit(EXIT_FAILURE);
+	}
+
+	free(buf);
+	close(fd);
+}
+
+static void test_stream_rcvlowat_def_cred_upd_server(const struct test_opts *opts)
+{
+	size_t recv_buf_size;
+	struct pollfd fds;
+	size_t buf_size;
+	void *buf;
+	int fd;
+
+	fd = vsock_stream_accept(VMADDR_CID_ANY, 1234, NULL);
+	if (fd < 0) {
+		perror("accept");
+		exit(EXIT_FAILURE);
+	}
+
+	buf_size = RCVLOWAT_CREDIT_UPD_BUF_SIZE;
+
+	if (setsockopt(fd, AF_VSOCK, SO_VM_SOCKETS_BUFFER_SIZE,
+		       &buf_size, sizeof(buf_size))) {
+		perror("setsockopt(SO_VM_SOCKETS_BUFFER_SIZE)");
+		exit(EXIT_FAILURE);
+	}
+
+	buf = malloc(buf_size);
+	if (!buf) {
+		perror("malloc");
+		exit(EXIT_FAILURE);
+	}
+
+	control_writeln("SRVREADY");
+
+	/* Wait until there will be 128KB of data in rx queue. */
+	while (1) {
+		ssize_t res;
+
+		res = recv(fd, buf, buf_size, MSG_PEEK);
+		if (res == buf_size)
+			break;
+
+		if (res <= 0) {
+			fprintf(stderr, "unexpected 'recv()' return: %zi\n", res);
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	/* There is 128KB of data in the socket's rx queue,
+	 * dequeue first 64KB, credit update is not sent.
+	 */
+	recv_buf_size = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
+	recv_buf(fd, buf, recv_buf_size, 0, recv_buf_size);
+	recv_buf_size++;
+
+	/* Updating SO_RCVLOWAT will send credit update. */
+	if (setsockopt(fd, SOL_SOCKET, SO_RCVLOWAT,
+		       &recv_buf_size, sizeof(recv_buf_size))) {
+		perror("setsockopt(SO_RCVLOWAT)");
+		exit(EXIT_FAILURE);
+	}
+
+	memset(&fds, 0, sizeof(fds));
+	fds.fd = fd;
+	fds.events = POLLIN | POLLRDNORM | POLLERR |
+		     POLLRDHUP | POLLHUP;
+
+	/* This 'poll()' will return once we receive last byte
+	 * sent by client.
+	 */
+	if (poll(&fds, 1, -1) < 0) {
+		perror("poll");
+		exit(EXIT_FAILURE);
+	}
+
+	if (fds.revents & POLLERR) {
+		fprintf(stderr, "'poll()' error\n");
+		exit(EXIT_FAILURE);
+	}
+
+	if (fds.revents & (POLLIN | POLLRDNORM)) {
+		recv_buf(fd, buf, recv_buf_size, 0, recv_buf_size);
+	} else {
+		/* These flags must be set, as there is at
+		 * least 64KB of data ready to read.
+		 */
+		fprintf(stderr, "POLLIN | POLLRDNORM expected\n");
+		exit(EXIT_FAILURE);
+	}
+
+	free(buf);
+	close(fd);
+}
+
 static struct test_case test_cases[] = {
 	{
 		.name = "SOCK_STREAM connection reset",
@@ -1285,6 +1411,11 @@ static struct test_case test_cases[] = {
 		.run_client = test_stream_msgzcopy_empty_errq_client,
 		.run_server = test_stream_msgzcopy_empty_errq_server,
 	},
+	{
+		.name = "SOCK_STREAM virtio SO_RCVLOWAT + deferred cred update",
+		.run_client = test_stream_rcvlowat_def_cred_upd_client,
+		.run_server = test_stream_rcvlowat_def_cred_upd_server,
+	},
 	{},
 };
 
-- 
2.25.1