linux-kernel - Re: [PATCH net-next v5 5/5] vsock/test: Add test for an unexpectedly lingering close()

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Message-ID: <edtepfqev6exbkfdnyzgkdkczif5wnn4oz4t5sxkl6sz64kcaf@f6yztxryvmlq>
Date: Wed, 21 May 2025 16:56:10 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Michal Luczaj <mhal@...x.co>
Cc: "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	"Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez <eperezma@...hat.com>, 
	Stefan Hajnoczi <stefanha@...hat.com>, virtualization@...ts.linux.dev, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH net-next v5 5/5] vsock/test: Add test for an unexpectedly
 lingering close()

On Wed, May 21, 2025 at 12:55:23AM +0200, Michal Luczaj wrote:
>There was an issue with SO_LINGER: instead of blocking until all queued
>messages for the socket have been successfully sent (or the linger timeout
>has been reached), close() would block until packets were handled by the
>peer.
>
>Add a test to alert on close() lingering when it should not.
>
>Signed-off-by: Michal Luczaj <mhal@...x.co>
>---
> tools/testing/vsock/vsock_test.c | 49 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 49 insertions(+)
>
>diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
>index f401c6a79495bc7fda97012e5bfeabec7dbfb60a..1040503333cf315e52592c876f2c1809b36fdfdb 100644
>--- a/tools/testing/vsock/vsock_test.c
>+++ b/tools/testing/vsock/vsock_test.c
>@@ -1839,6 +1839,50 @@ static void test_stream_linger_server(const struct test_opts *opts)
> 	close(fd);
> }
>
>+static void test_stream_nolinger_client(const struct test_opts *opts)
>+{
>+	bool nowait;
>+	time_t ns;
>+	int fd;
>+
>+	fd = vsock_stream_connect(opts->peer_cid, opts->peer_port);
>+	if (fd < 0) {
>+		perror("connect");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	enable_so_linger(fd);

If we use a parameter for the linger timeout, IMO will be easy to 
understand this test, defining the timeout in this test, set it and 
check the value, without defining LINGER_TIMEOUT in util.h.

>+	send_byte(fd, 1, 0); /* Left unread to expose incorrect behaviour. */
>+	nowait = vsock_wait_sent(fd);
>+
>+	ns = current_nsec();
>+	close(fd);
>+	ns = current_nsec() - ns;
>+
>+	if (nowait) {
>+		fprintf(stderr, "Test skipped, SIOCOUTQ not supported.\n");
>+	} else if ((ns + NSEC_PER_SEC - 1) / NSEC_PER_SEC >= LINGER_TIMEOUT) {

Should we define a macro for this conversion?

Or just use DIV_ROUND_UP:

--- a/tools/testing/vsock/vsock_test.c
+++ b/tools/testing/vsock/vsock_test.c
@@ -1831,7 +1831,7 @@ static void test_stream_nolinger_client(const struct test_opts *opts)

         if (nowait) {
                 fprintf(stderr, "Test skipped, SIOCOUTQ not supported.\n");
-       } else if ((ns + NSEC_PER_SEC - 1) / NSEC_PER_SEC >= LINGER_TIMEOUT) {
+       } else if (DIV_ROUND_UP(ns, NSEC_PER_SEC) >= LINGER_TIMEOUT) {
                 fprintf(stderr, "Unexpected lingering\n");
                 exit(EXIT_FAILURE);
         }

The rest LGTM.

Thanks,
Stefano

>+		fprintf(stderr, "Unexpected lingering\n");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	control_writeln("DONE");
>+}
>+
>+static void test_stream_nolinger_server(const struct test_opts *opts)
>+{
>+	int fd;
>+
>+	fd = vsock_stream_accept(VMADDR_CID_ANY, opts->peer_port, NULL);
>+	if (fd < 0) {
>+		perror("accept");
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	control_expectln("DONE");
>+	close(fd);
>+}
>+
> static struct test_case test_cases[] = {
> 	{
> 		.name = "SOCK_STREAM connection reset",
>@@ -1999,6 +2043,11 @@ static struct test_case test_cases[] = {
> 		.run_client = test_stream_linger_client,
> 		.run_server = test_stream_linger_server,
> 	},
>+	{
>+		.name = "SOCK_STREAM SO_LINGER close() on unread",
>+		.run_client = test_stream_nolinger_client,
>+		.run_server = test_stream_nolinger_server,
>+	},
> 	{},
> };
>
>
>-- 
>2.49.0
>