sock: Add a function to check if a socket is connected

This is useful for detecting sockets that have been disconnected
by the other end without reading data.

Change-Id: Ieb6529984d282d48373766d9f5555cf11720f19b
Signed-off-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/470513
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>

include/spdk/sock.h

@@ -195,6 +195,15 @@ bool spdk_sock_is_ipv6(struct spdk_sock *sock);
  */
 bool spdk_sock_is_ipv4(struct spdk_sock *sock);
 
+/**
+ * Check whether the socket is currently connected.
+ *
+ * \param sock Socket to check
+ *
+ * \return true if the socket is connected or false otherwise.
+ */
+bool spdk_sock_is_connected(struct spdk_sock *sock);
+
 /**
  * Callback function for spdk_sock_group_add_sock().
  *

include/spdk_internal/sock.h

@@ -86,6 +86,7 @@ struct spdk_net_impl {
 
 	bool (*is_ipv6)(struct spdk_sock *sock);
 	bool (*is_ipv4)(struct spdk_sock *sock);
+	bool (*is_connected)(struct spdk_sock *sock);
 
 	int (*get_placement_id)(struct spdk_sock *sock, int *placement_id);
 	struct spdk_sock_group_impl *(*group_impl_create)(void);

lib/sock/sock.c

@@ -308,6 +308,12 @@ spdk_sock_is_ipv4(struct spdk_sock *sock)
 	return sock->net_impl->is_ipv4(sock);
 }
 
+bool
+spdk_sock_is_connected(struct spdk_sock *sock)
+{
+	return sock->net_impl->is_connected(sock);
+}
+
 struct spdk_sock_group *
 spdk_sock_group_create(void *ctx)
 {

module/sock/posix/posix.c

@@ -529,6 +529,29 @@ spdk_posix_sock_is_ipv4(struct spdk_sock *_sock)
 	return (sa.ss_family == AF_INET);
 }
 
+static bool
+spdk_posix_sock_is_connected(struct spdk_sock *_sock)
+{
+	struct spdk_posix_sock *sock = __posix_sock(_sock);
+	uint8_t byte;
+	int rc;
+
+	rc = recv(sock->fd, &byte, 1, MSG_PEEK);
+	if (rc == 0) {
+		return false;
+	}
+
+	if (rc < 0) {
+		if (errno == EAGAIN || errno == EWOULDBLOCK) {
+			return true;
+		}
+
+		return false;
+	}
+
+	return true;
+}
+
 static int
 spdk_posix_sock_get_placement_id(struct spdk_sock *_sock, int *placement_id)
 {
@@ -686,6 +709,7 @@ static struct spdk_net_impl g_posix_net_impl = {
 	.set_priority	= spdk_posix_sock_set_priority,
 	.is_ipv6	= spdk_posix_sock_is_ipv6,
 	.is_ipv4	= spdk_posix_sock_is_ipv4,
+	.is_connected	= spdk_posix_sock_is_connected,
 	.get_placement_id	= spdk_posix_sock_get_placement_id,
 	.group_impl_create	= spdk_posix_sock_group_impl_create,
 	.group_impl_add_sock	= spdk_posix_sock_group_impl_add_sock,

module/sock/vpp/vpp.c

@@ -1006,6 +1006,14 @@ spdk_vpp_sock_is_ipv4(struct spdk_sock *_sock)
 	return __vpp_session(_sock)->app_session.transport.is_ip4;
 }
 
+static bool
+spdk_vpp_sock_is_connected(struct spdk_sock *_sock)
+{
+	assert(g_svm.vpp_initialized);
+
+	return (__vpp_session(_sock)->app_session.session_state == VPP_SESSION_STATE_READY);
+}
+
 static int
 spdk_vpp_sock_get_placement_id(struct spdk_sock *_sock, int *placement_id)
 {
@@ -1440,6 +1448,7 @@ static struct spdk_net_impl g_vpp_net_impl = {
 	.set_priority	= spdk_vpp_sock_set_priority,
 	.is_ipv6	= spdk_vpp_sock_is_ipv6,
 	.is_ipv4	= spdk_vpp_sock_is_ipv4,
+	.is_connected	= spdk_vpp_sock_is_connected,
 	.get_placement_id	= spdk_vpp_sock_get_placement_id,
 	.group_impl_create	= spdk_vpp_sock_group_impl_create,
 	.group_impl_add_sock	= spdk_vpp_sock_group_impl_add_sock,

test/common/lib/test_sock.c

@@ -50,6 +50,7 @@ DEFINE_STUB(spdk_sock_set_recvbuf, int, (struct spdk_sock *sock, int sz), 0);
 DEFINE_STUB(spdk_sock_set_sendbuf, int, (struct spdk_sock *sock, int sz), 0);
 DEFINE_STUB(spdk_sock_is_ipv6, bool, (struct spdk_sock *sock), false);
 DEFINE_STUB(spdk_sock_is_ipv4, bool, (struct spdk_sock *sock), true);
+DEFINE_STUB(spdk_sock_is_connected, bool, (struct spdk_sock *sock), true);
 DEFINE_STUB(spdk_sock_group_create, struct spdk_sock_group *, (void *ctx), NULL);
 DEFINE_STUB(spdk_sock_group_add_sock, int, (struct spdk_sock_group *group, struct spdk_sock *sock,
 		spdk_sock_cb cb_fn, void *cb_arg), 0);

test/unit/lib/sock/sock.c/sock_ut.c

@@ -130,6 +130,7 @@ spdk_ut_sock_accept(struct spdk_sock *_sock)
 
 	SPDK_CU_ASSERT_FATAL(g_ut_client_sock != NULL);
 	g_ut_client_sock->peer = new_sock;
+	new_sock->peer = g_ut_client_sock;
 
 	return &new_sock->base;
 }
@@ -145,6 +146,11 @@ spdk_ut_sock_close(struct spdk_sock *_sock)
 	if (sock == g_ut_client_sock) {
 		g_ut_client_sock = NULL;
 	}
+
+	if (sock->peer != NULL) {
+		sock->peer->peer = NULL;
+	}
+
 	free(_sock);
 
 	return 0;
@@ -244,6 +250,14 @@ spdk_ut_sock_is_ipv4(struct spdk_sock *_sock)
 	return true;
 }
 
+static bool
+spdk_ut_sock_is_connected(struct spdk_sock *_sock)
+{
+	struct spdk_ut_sock *sock = __ut_sock(_sock);
+
+	return (sock->peer != NULL);
+}
+
 static int
 spdk_ut_sock_get_placement_id(struct spdk_sock *_sock, int *placement_id)
 {
@@ -331,6 +345,7 @@ static struct spdk_net_impl g_ut_net_impl = {
 	.set_priority	= spdk_ut_sock_set_priority,
 	.is_ipv6	= spdk_ut_sock_is_ipv6,
 	.is_ipv4	= spdk_ut_sock_is_ipv4,
+	.is_connected	= spdk_ut_sock_is_connected,
 	.get_placement_id	= spdk_ut_sock_get_placement_id,
 	.group_impl_create	= spdk_ut_sock_group_impl_create,
 	.group_impl_add_sock	= spdk_ut_sock_group_impl_add_sock,
@@ -371,6 +386,8 @@ _sock(const char *ip, int port)
 
 	server_sock = spdk_sock_accept(listen_sock);
 	SPDK_CU_ASSERT_FATAL(server_sock != NULL);
+	CU_ASSERT(spdk_sock_is_connected(client_sock) == true);
+	CU_ASSERT(spdk_sock_is_connected(server_sock) == true);
 
 	/* Test spdk_sock_recv */
 	iov.iov_base = test_string;
@@ -418,6 +435,11 @@ _sock(const char *ip, int port)
 	CU_ASSERT(client_sock == NULL);
 	CU_ASSERT(rc == 0);
 
+	/* On FreeBSD, it takes a small amount of time for a close to propagate to the
+	 * other side, even in loopback. Introduce a small sleep. */
+	sleep(1);
+	CU_ASSERT(spdk_sock_is_connected(server_sock) == false);
+
 	rc = spdk_sock_close(&server_sock);
 	CU_ASSERT(server_sock == NULL);
 	CU_ASSERT(rc == 0);