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From:   Arseniy Krasnov <avkrasnov@salutedevices.com>
To:     Stefan Hajnoczi <stefanha@redhat.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        Bobby Eshleman <bobby.eshleman@bytedance.com>
CC:     <kvm@vger.kernel.org>, <virtualization@lists.linux-foundation.org>,
        <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <kernel@sberdevices.ru>, <oxffffaa@gmail.com>,
        <avkrasnov@salutedevices.com>
Subject: [PATCH net-next v6 4/4] vsock/test: two tests to check credit update logic
Date:   Tue, 5 Dec 2023 09:48:06 +0300
Message-ID: <20231205064806.2851305-5-avkrasnov@salutedevices.com>
In-Reply-To: <20231205064806.2851305-1-avkrasnov@salutedevices.com>
References: <20231205064806.2851305-1-avkrasnov@salutedevices.com>
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Both tests are almost same, only differs in two 'if' conditions, so
implemented in a single function. Tests check, that credit update
message is sent:

1) During setting SO_RCVLOWAT value of the socket.
2) When number of 'rx_bytes' become smaller than SO_RCVLOWAT value.

Signed-off-by: Arseniy Krasnov <avkrasnov@salutedevices.com>
---
 Changelog:
 v1 -> v2:
  * Update commit message by removing 'This patch adds XXX' manner.
  * Update commit message by adding details about dependency for this
    test from kernel internal define VIRTIO_VSOCK_MAX_PKT_BUF_SIZE.
  * Add comment for this dependency in 'vsock_test.c' where this define
    is duplicated.
 v2 -> v3:
  * Replace synchronization based on control TCP socket with vsock
    data socket - this is needed to allow sender transmit data only
    when new buffer size of receiver is visible to sender. Otherwise
    there is race and test fails sometimes.
 v3 -> v4:
  * Replace 'recv_buf()' to 'recv(MSG_DONTWAIT)' in last read operation
    in server part. This is needed to ensure that 'poll()' wake up us
    when number of bytes ready to read is equal to SO_RCVLOWAT value.
 v4 -> v5:
  * Use 'recv_buf(MSG_DONTWAIT)' instead of 'recv(MSG_DONTWAIT)'.
 v5 -> v6:
  * Add second test which checks, that credit update is sent during
    reading data from socket.
  * Update commit message.

 tools/testing/vsock/vsock_test.c | 175 +++++++++++++++++++++++++++++++
 1 file changed, 175 insertions(+)

diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
index 01fa816868bc..66246d81d654 100644
--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -1232,6 +1232,171 @@ static void test_double_bind_connect_client(const struct test_opts *opts)
 	}
 }
 
+#define RCVLOWAT_CREDIT_UPD_BUF_SIZE	(1024 * 128)
+/* This define is the same as in 'include/linux/virtio_vsock.h':
+ * it is used to decide when to send credit update message during
+ * reading from rx queue of a socket. Value and its usage in
+ * kernel is important for this test.
+ */
+#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. */
+	recv_byte(fd, 1, 0);
+
+	if (send(fd, buf, buf_size, 0) != buf_size) {
+		perror("send failed");
+		exit(EXIT_FAILURE);
+	}
+
+	free(buf);
+	close(fd);
+}
+
+static void test_stream_credit_update_test(const struct test_opts *opts,
+					   bool low_rx_bytes_test)
+{
+	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);
+	}
+
+	if (low_rx_bytes_test) {
+		/* Set new SO_RCVLOWAT here. This enables sending credit
+		 * update when number of bytes if our rx queue become <
+		 * SO_RCVLOWAT value.
+		 */
+		recv_buf_size = 1 + VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
+
+		if (setsockopt(fd, SOL_SOCKET, SO_RCVLOWAT,
+			       &recv_buf_size, sizeof(recv_buf_size))) {
+			perror("setsockopt(SO_RCVLOWAT)");
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	/* Send one dummy byte here, because 'setsockopt()' above also
+	 * sends special packet which tells sender to update our buffer
+	 * size. This 'send_byte()' will serialize such packet with data
+	 * reads in a loop below. Sender starts transmission only when
+	 * it receives this single byte.
+	 */
+	send_byte(fd, 1, 0);
+
+	buf = malloc(buf_size);
+	if (!buf) {
+		perror("malloc");
+		exit(EXIT_FAILURE);
+	}
+
+	/* 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 sent if 'low_rx_bytes_test' == true.
+	 * Otherwise, credit update is sent in 'if (!low_rx_bytes_test)'.
+	 */
+	recv_buf_size = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
+	recv_buf(fd, buf, recv_buf_size, 0, recv_buf_size);
+
+	if (!low_rx_bytes_test) {
+		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);
+		}
+	}
+
+	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, MSG_DONTWAIT, 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 void test_stream_cred_upd_on_low_rx_bytes(const struct test_opts *opts)
+{
+	test_stream_credit_update_test(opts, true);
+}
+
+static void test_stream_cred_upd_on_set_rcvlowat(const struct test_opts *opts)
+{
+	test_stream_credit_update_test(opts, false);
+}
+
 static struct test_case test_cases[] = {
 	{
 		.name = "SOCK_STREAM connection reset",
@@ -1342,6 +1507,16 @@ static struct test_case test_cases[] = {
 		.run_client = test_double_bind_connect_client,
 		.run_server = test_double_bind_connect_server,
 	},
+	{
+		.name = "SOCK_STREAM virtio credit update + SO_RCVLOWAT",
+		.run_client = test_stream_rcvlowat_def_cred_upd_client,
+		.run_server = test_stream_cred_upd_on_set_rcvlowat,
+	},
+	{
+		.name = "SOCK_STREAM virtio credit update + low rx_bytes",
+		.run_client = test_stream_rcvlowat_def_cred_upd_client,
+		.run_server = test_stream_cred_upd_on_low_rx_bytes,
+	},
 	{},
 };
 
-- 
2.25.1