[PATCH net v2 2/2] selftest: af_unix: Test scm_fds on dgram disconnect.

[Siddharth Chintamaneni <sidchintamaneni@gmail.com>]

Add dgram_disconnect_fdinfo in scm_rights.c verifying that scm_fds in
/proc/self/fdinfo/<fd> returns to 0 when a connected SOCK_DGRAM socket
with queued SCM_RIGHTS datagrams disconnects via connect(AF_UNSPEC) or
observes a dead peer in send().

Signed-off-by: Siddharth Chintamaneni <sidchintamaneni@gmail.com>
---
 .../selftests/net/af_unix/scm_rights.c        | 79 +++++++++++++++++++
 1 file changed, 79 insertions(+)

diff --git a/tools/testing/selftests/net/af_unix/scm_rights.c b/tools/testing/selftests/net/af_unix/scm_rights.c
index c165f250220a..ced83d3173b7 100644
--- a/tools/testing/selftests/net/af_unix/scm_rights.c
+++ b/tools/testing/selftests/net/af_unix/scm_rights.c
@@ -395,4 +395,83 @@ TEST_F(scm_rights, mixed_lowpoint)
 	close_sockets(6);
 }
 
+static int count_scm_fds(struct __test_metadata *_metadata, int fd)
+{
+	char path[64], *line = NULL;
+	int scm_fds = -1, ret;
+	size_t unused = 0;
+	FILE *f;
+
+	snprintf(path, sizeof(path), "/proc/self/fdinfo/%d", fd);
+
+	f = fopen(path, "r");
+	ASSERT_NE(NULL, f);
+
+	while (getline(&line, &unused, f) != -1) {
+		if (strncmp(line, "scm_fds:", 8))
+			continue;
+
+		ret = sscanf(line + 8, "%d", &scm_fds);
+		ASSERT_EQ(1, ret);
+
+		break;
+	}
+
+	free(line);
+
+	ret = fclose(f);
+	ASSERT_EQ(0, ret);
+
+	return scm_fds;
+}
+
+TEST(dgram_disconnect_fdinfo)
+{
+	const FIXTURE_VARIANT(scm_rights) variant = {
+		.name = "UNIX ",
+		.type = SOCK_DGRAM,
+	};
+	FIXTURE_DATA(scm_rights) self = {};
+	struct sockaddr addr = {
+		.sa_family = AF_UNSPEC,
+	};
+	int ret;
+
+	ret = unshare(CLONE_NEWNET);
+	ASSERT_EQ(0, ret);
+	ASSERT_EQ(0, count_sockets(_metadata, &variant));
+
+	create_socketpairs(_metadata, &self, &variant, 2);
+
+	/* 1. Disconnect via connect(AF_UNSPEC) */
+	__send_fd(_metadata, &self, &variant, 0, 0);
+	ASSERT_EQ(2, count_scm_fds(_metadata, self.fd[0]));
+
+	ret = connect(self.fd[0], &addr, sizeof(addr.sa_family));
+	ASSERT_EQ(0, ret);
+	ASSERT_EQ(0, count_scm_fds(_metadata, self.fd[0]));
+
+	/* 2. Dead-peer disconnect via send() */
+	__send_fd(_metadata, &self, &variant, 1, 1);
+	ASSERT_EQ(2, count_scm_fds(_metadata, self.fd[2]));
+
+	ret = close(self.fd[3]);
+	ASSERT_EQ(0, ret);
+
+	ret = send(self.fd[2], "x", 1, 0);
+	ASSERT_EQ(-1, ret);
+	ASSERT_EQ(ECONNREFUSED, errno);
+	ASSERT_EQ(0, count_scm_fds(_metadata, self.fd[2]));
+
+	ret = close(self.fd[0]);
+	ASSERT_EQ(0, ret);
+	ret = close(self.fd[1]);
+	ASSERT_EQ(0, ret);
+	ret = close(self.fd[2]);
+	ASSERT_EQ(0, ret);
+
+	sleep(1);
+	ASSERT_EQ(0, count_sockets(_metadata, &variant));
+}
+
 TEST_HARNESS_MAIN
-- 
2.43.0