net: sockets: Add socket processing priority

When creating a socket, all of the registered socket implementation are
processed in a sequence, allowing to find appropriate socket
implementation for specified family/type/protocol. So far however,
the order of processing was not clearly defined, leaving ambiguity if
multiple implmentations supported the same set of parameters.

Fix this, by registering socket priority along with implementation. This
makes the processing order of particular socket implementations
explicit, giving more flexibility to the user, for example when it's
neeed to prioritze one implementation over another if they support the
same set of parameters.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>

drivers/modem/quectel-bg9x.c

@@ -1203,4 +1203,5 @@ NET_DEVICE_DT_INST_OFFLOAD_DEFINE(0, modem_init, NULL,
 				  &api_funcs, MDM_MAX_DATA_LENGTH);
 
 /* Register NET sockets. */
-NET_SOCKET_REGISTER(quectel_bg9x, AF_UNSPEC, offload_is_supported, offload_socket);
+NET_SOCKET_REGISTER(quectel_bg9x, NET_SOCKET_DEFAULT_PRIO, AF_UNSPEC,
+		    offload_is_supported, offload_socket);

drivers/modem/ublox-sara-r4.c

@@ -1956,8 +1956,8 @@ static bool offload_is_supported(int family, int type, int proto)
 	return true;
 }
 
-NET_SOCKET_REGISTER(ublox_sara_r4, AF_UNSPEC, offload_is_supported,
-		    offload_socket);
+NET_SOCKET_REGISTER(ublox_sara_r4, NET_SOCKET_DEFAULT_PRIO, AF_UNSPEC,
+		    offload_is_supported, offload_socket);
 
 #if defined(CONFIG_DNS_RESOLVER)
 /* TODO: This is a bare-bones implementation of DNS handling

drivers/wifi/eswifi/eswifi_socket_offload.c

@@ -571,8 +571,8 @@ static const struct socket_op_vtable eswifi_socket_fd_op_vtable = {
 };
 
 #ifdef CONFIG_NET_SOCKETS_OFFLOAD
-NET_SOCKET_REGISTER(eswifi, AF_UNSPEC, eswifi_socket_is_supported,
-		    eswifi_socket_create);
+NET_SOCKET_REGISTER(eswifi, NET_SOCKET_DEFAULT_PRIO, AF_UNSPEC,
+		    eswifi_socket_is_supported, eswifi_socket_create);
 #endif
 
 static int eswifi_off_getaddrinfo(const char *node, const char *service,

drivers/wifi/simplelink/simplelink_sockets.c

@@ -1264,8 +1264,8 @@ static int simplelink_socket_accept(void *obj, struct sockaddr *addr,
 }
 
 #ifdef CONFIG_NET_SOCKETS_OFFLOAD
-NET_SOCKET_REGISTER(simplelink, AF_UNSPEC, simplelink_is_supported,
-		    simplelink_socket_create);
+NET_SOCKET_REGISTER(simplelink, NET_SOCKET_DEFAULT_PRIO, AF_UNSPEC,
+		    simplelink_is_supported, simplelink_socket_create);
 #endif
 
 void simplelink_sockets_init(void)

include/net/socket.h

@@ -880,12 +880,14 @@ struct net_socket_register {
 	int (*handler)(int family, int type, int proto);
 };
 
-#define NET_SOCKET_GET_NAME(socket_name)	\
-	(__net_socket_register_##socket_name)
+#define NET_SOCKET_DEFAULT_PRIO CONFIG_NET_SOCKETS_PRIORITY_DEFAULT
 
-#define NET_SOCKET_REGISTER(socket_name, _family, _is_supported, _handler) \
+#define NET_SOCKET_GET_NAME(socket_name, prio)	\
+	(__net_socket_register_##prio##_##socket_name)
+
+#define NET_SOCKET_REGISTER(socket_name, prio, _family, _is_supported, _handler) \
 	static const STRUCT_SECTION_ITERABLE(net_socket_register,	\
-			NET_SOCKET_GET_NAME(socket_name)) = {		\
+			NET_SOCKET_GET_NAME(socket_name, prio)) = {		\
 		.family = _family,					\
 		.is_supported = _is_supported,				\
 		.handler = _handler,					\

subsys/net/lib/sockets/Kconfig

@@ -10,6 +10,16 @@ menuconfig NET_SOCKETS
 
 if NET_SOCKETS
 
+config NET_SOCKETS_PRIORITY_DEFAULT
+	int "Default processing priority for sockets"
+	default 50
+	help
+	  Default processing priority for socket implementations. This defines
+	  the order of processing of particular socket implementations when
+	  creating a new socket, lower value indicate earlier processing. This
+	  allows to for instance prioritize offloaded socket processing during
+	  socket creation over the native one, or vice versa.
+
 config NET_SOCKETS_POSIX_NAMES
 	bool "POSIX names for Sockets API (without full POSIX API)"
 	default y if !POSIX_API
@@ -62,6 +72,13 @@ config NET_SOCKETS_SOCKOPT_TLS
 	  Enable TLS socket option support which automatically establishes
 	  a TLS connection to the remote host.
 
+config NET_SOCKETS_TLS_PRIORITY
+	int "Default processing priority for TLS sockets"
+	default 45
+	help
+	  Processing priority for TLS sockets. Should be lower than
+	  NET_SOCKETS_PRIORITY_DEFAULT in order to be processed correctly.
+
 config NET_SOCKETS_TLS_SET_MAX_FRAGMENT_LENGTH
 	bool "Set Maximum Fragment Length (MFL)"
 	default y

subsys/net/lib/sockets/sockets.c

@@ -2217,6 +2217,6 @@ static bool inet_is_supported(int family, int type, int proto)
 	return true;
 }
 
-NET_SOCKET_REGISTER(af_inet46, AF_UNSPEC, inet_is_supported,
-		    zsock_socket_internal);
+NET_SOCKET_REGISTER(af_inet46, NET_SOCKET_DEFAULT_PRIO, AF_UNSPEC,
+		    inet_is_supported, zsock_socket_internal);
 #endif /* CONFIG_NET_NATIVE */

subsys/net/lib/sockets/sockets_can.c

@@ -703,4 +703,5 @@ static bool can_is_supported(int family, int type, int proto)
 	return true;
 }
 
-NET_SOCKET_REGISTER(af_can, AF_CAN, can_is_supported, zcan_socket);
+NET_SOCKET_REGISTER(af_can, NET_SOCKET_DEFAULT_PRIO, AF_CAN, can_is_supported,
+		    zcan_socket);

subsys/net/lib/sockets/sockets_net_mgmt.c

@@ -390,5 +390,5 @@ static bool net_mgmt_is_supported(int family, int type, int proto)
 	return true;
 }
 
-NET_SOCKET_REGISTER(af_net_mgmt, AF_NET_MGMT, net_mgmt_is_supported,
-		    znet_mgmt_socket);
+NET_SOCKET_REGISTER(af_net_mgmt, NET_SOCKET_DEFAULT_PRIO, AF_NET_MGMT,
+		    net_mgmt_is_supported, znet_mgmt_socket);

subsys/net/lib/sockets/sockets_packet.c

@@ -394,4 +394,5 @@ static bool packet_is_supported(int family, int type, int proto)
 	return false;
 }
 
-NET_SOCKET_REGISTER(af_packet, AF_PACKET, packet_is_supported, zpacket_socket);
+NET_SOCKET_REGISTER(af_packet, NET_SOCKET_DEFAULT_PRIO, AF_PACKET,
+		    packet_is_supported, zpacket_socket);

subsys/net/lib/sockets/sockets_tls.c

@@ -2658,4 +2658,13 @@ static bool tls_is_supported(int family, int type, int proto)
 	return false;
 }
 
-NET_SOCKET_REGISTER(tls, AF_UNSPEC, tls_is_supported, ztls_socket);
+/* Since both, TLS sockets and regular ones fall under the same address family,
+ * it's required to process TLS first in order to capture socket calls which
+ * create sockets for secure protocols. Every other call for AF_INET/AF_INET6
+ * will be forwarded to regular socket implementation.
+ */
+BUILD_ASSERT(CONFIG_NET_SOCKETS_TLS_PRIORITY < CONFIG_NET_SOCKETS_PRIORITY_DEFAULT,
+	     "CONFIG_NET_SOCKETS_TLS_PRIORITY have to be smaller than CONFIG_NET_SOCKETS_PRIORITY_DEFAULT");
+
+NET_SOCKET_REGISTER(tls, CONFIG_NET_SOCKETS_TLS_PRIORITY, AF_UNSPEC,
+		    tls_is_supported, ztls_socket);

tests/net/socket/register/src/main.c

@@ -133,7 +133,7 @@ static const struct test_result {
 		.test_case.type = SOCK_RAW,
 		.test_case.proto = IPPROTO_RAW,
 		.result = -1,
-		.error = EPFNOSUPPORT,
+		.error = EAFNOSUPPORT,
 	},
 	{
 		/* 15 */
@@ -212,14 +212,16 @@ static bool is_ip(int family, int type, int proto)
 	return true;
 }
 
-NET_SOCKET_REGISTER(af_inet,   AF_INET,   is_ip,      socket_test);
-NET_SOCKET_REGISTER(af_inet6,  AF_INET6,  is_ip,      socket_test);
-NET_SOCKET_REGISTER(af_can2,   AF_CAN,    is_ip,      socket_test);
+#define TEST_SOCKET_PRIO 40
+
+NET_SOCKET_REGISTER(af_inet,   TEST_SOCKET_PRIO, AF_INET,   is_ip,      socket_test);
+NET_SOCKET_REGISTER(af_inet6,  TEST_SOCKET_PRIO, AF_INET6,  is_ip,      socket_test);
+NET_SOCKET_REGISTER(af_can2,   TEST_SOCKET_PRIO, AF_CAN,    is_ip,      socket_test);
 
 /* For these socket families, we return ok always for now */
-NET_SOCKET_REGISTER(tls,       AF_UNSPEC, is_tls,    socket_test_ok);
-NET_SOCKET_REGISTER(af_packet, AF_PACKET, is_packet, socket_test_ok);
-NET_SOCKET_REGISTER(af_can,    AF_CAN,    is_can,    socket_test_ok);
+NET_SOCKET_REGISTER(tls,       TEST_SOCKET_PRIO, AF_UNSPEC, is_tls,    socket_test_ok);
+NET_SOCKET_REGISTER(af_packet, TEST_SOCKET_PRIO, AF_PACKET, is_packet, socket_test_ok);
+NET_SOCKET_REGISTER(af_can,    TEST_SOCKET_PRIO, AF_CAN,    is_can,    socket_test_ok);
 
 void test_create_sockets(void)
 {