net: if: Connect interface with offloaded socket implementation

Instead of keeping a boolean informing whether a network interface is
offloaded at socket layer or not, keep a pointer to a function which
allows to create an offloaded socket. Native interfaces keep this as
NULL, while for offloaded interfaces it allows to connect an offloaded
socket implementation with an interface.

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

drivers/modem/quectel-bg9x.c

@@ -1066,6 +1066,8 @@ static const struct socket_op_vtable offload_socket_fd_op_vtable = {
 	.setsockopt	= NULL,
 };
 
+static int offload_socket(int family, int type, int proto);
+
 /* Setup the Modem NET Interface. */
 static void modem_net_iface_init(struct net_if *iface)
 {
@@ -1077,6 +1079,8 @@ static void modem_net_iface_init(struct net_if *iface)
 			     sizeof(data->mac_addr),
 			     NET_LINK_ETHERNET);
 	data->net_iface = iface;
+
+	net_if_socket_offload_set(iface, offload_socket);
 }
 
 static struct net_if_api api_funcs = {

drivers/modem/simcom-sim7080.c

@@ -62,6 +62,8 @@ static inline uint8_t *modem_get_mac(const struct device *dev)
 	return data->mac_addr;
 }
 
+static int offload_socket(int family, int type, int proto);
+
 /* Setup the Modem NET Interface. */
 static void modem_net_iface_init(struct net_if *iface)
 {
@@ -73,6 +75,8 @@ static void modem_net_iface_init(struct net_if *iface)
 	data->netif = iface;
 
 	socket_offload_dns_register(&offload_dns_ops);
+
+	net_if_socket_offload_set(iface, offload_socket);
 }
 
 /**

drivers/modem/ublox-sara-r4.c

@@ -2097,6 +2097,8 @@ static inline uint8_t *modem_get_mac(const struct device *dev)
 	return data->mac_addr;
 }
 
+static int offload_socket(int family, int type, int proto);
+
 static void modem_net_iface_init(struct net_if *iface)
 {
 	const struct device *dev = net_if_get_device(iface);
@@ -2111,6 +2113,8 @@ static void modem_net_iface_init(struct net_if *iface)
 #ifdef CONFIG_DNS_RESOLVER
 	socket_offload_dns_register(&offload_dns_ops);
 #endif
+
+	net_if_socket_offload_set(iface, offload_socket);
 }
 
 static struct net_if_api api_funcs = {

drivers/wifi/eswifi/eswifi.h

@@ -130,6 +130,7 @@ struct eswifi_dev *eswifi_by_iface_idx(uint8_t iface);
 int eswifi_at_cmd_rsp(struct eswifi_dev *eswifi, char *cmd, char **rsp);
 void eswifi_async_msg(struct eswifi_dev *eswifi, char *msg, size_t len);
 void eswifi_offload_async_msg(struct eswifi_dev *eswifi, char *msg, size_t len);
+int eswifi_socket_create(int family, int type, int proto);
 
 int eswifi_socket_type_from_zephyr(int proto, enum eswifi_transport_type *type);
 

drivers/wifi/eswifi/eswifi_core.c

@@ -411,6 +411,8 @@ static void eswifi_iface_init(struct net_if *iface)
 	eswifi_offload_init(eswifi);
 #if defined(CONFIG_NET_SOCKETS_OFFLOAD)
 	eswifi_socket_offload_init(eswifi);
+
+	net_if_socket_offload_set(iface, eswifi_socket_create);
 #endif
 
 }

drivers/wifi/eswifi/eswifi_socket_offload.c

@@ -512,7 +512,7 @@ static bool eswifi_socket_is_supported(int family, int type, int proto)
 	return true;
 }
 
-static int eswifi_socket_create(int family, int type, int proto)
+int eswifi_socket_create(int family, int type, int proto)
 {
 	int fd = z_reserve_fd();
 	int sock;

drivers/wifi/simplelink/simplelink.c

@@ -258,6 +258,8 @@ static void simplelink_iface_init(struct net_if *iface)
 	/* Direct socket offload: */
 	socket_offload_dns_register(&simplelink_dns_ops);
 	simplelink_sockets_init();
+
+	net_if_socket_offload_set(iface, simplelink_socket_create);
 #endif
 
 }

drivers/wifi/simplelink/simplelink_sockets.c

@@ -1258,7 +1258,7 @@ static bool simplelink_is_supported(int family, int type, int proto)
 	return true;
 }
 
-static int simplelink_socket_create(int family, int type, int proto)
+int simplelink_socket_create(int family, int type, int proto)
 {
 	int fd = z_reserve_fd();
 	int sock;

drivers/wifi/simplelink/simplelink_support.h

@@ -45,6 +45,8 @@ extern int z_simplelink_init(simplelink_wifi_cb_t wifi_cb);
 extern int z_simplelink_connect(struct wifi_connect_req_params *params);
 extern int z_simplelink_disconnect(void);
 
+int simplelink_socket_create(int family, int type, int proto);
+
 #ifdef __cplusplus
 }
 #endif

include/zephyr/net/net_if.h

@@ -411,6 +411,14 @@ struct net_traffic_class {
 	k_thread_stack_t *stack;
 };
 
+/**
+ * @typedef net_socket_create_t
+
+ * @brief A function prototype to create an offloaded socket. The prototype is
+ *        compatible with socket() function.
+ */
+typedef int (*net_socket_create_t)(int, int, int);
+
 /**
  * @brief Network Interface Device structure
  *
@@ -453,8 +461,10 @@ struct net_if_dev {
 	uint16_t mtu;
 
 #if defined(CONFIG_NET_SOCKETS_OFFLOAD)
-	/** Indicate whether interface is offloaded at socket level. */
+	/** A function pointer to create an offloaded socket.
-	bool offloaded;
+	 *  If non-NULL, the interface is considered offloaded at socket level.
+	 */
+	net_socket_create_t socket_offload;
 #endif /* CONFIG_NET_SOCKETS_OFFLOAD */
 };
 
@@ -662,7 +672,7 @@ static inline struct net_offload *net_if_offload(struct net_if *iface)
 static inline bool net_if_is_socket_offloaded(struct net_if *iface)
 {
 #if defined(CONFIG_NET_SOCKETS_OFFLOAD)
-	return iface->if_dev->offloaded;
+	return (iface->if_dev->socket_offload != NULL);
 #else
 	ARG_UNUSED(iface);
 
@@ -670,6 +680,41 @@ static inline bool net_if_is_socket_offloaded(struct net_if *iface)
 #endif
 }
 
+/**
+ * @brief Set the function to create an offloaded socket
+ *
+ * @param iface Network interface
+ * @param socket_offload A function to create an offloaded socket
+ */
+static inline void net_if_socket_offload_set(
+		struct net_if *iface, net_socket_create_t socket_offload)
+{
+#if defined(CONFIG_NET_SOCKETS_OFFLOAD)
+	iface->if_dev->socket_offload = socket_offload;
+#else
+	ARG_UNUSED(iface);
+	ARG_UNUSED(socket_offload);
+#endif
+}
+
+/**
+ * @brief Return the function to create an offloaded socket
+ *
+ * @param iface Network interface
+ *
+ * @return NULL if the interface is not socket offloaded, valid pointer otherwise
+ */
+static inline net_socket_create_t net_if_socket_offload(struct net_if *iface)
+{
+#if defined(CONFIG_NET_SOCKETS_OFFLOAD)
+	return iface->if_dev->socket_offload;
+#else
+	ARG_UNUSED(iface);
+
+	return NULL;
+#endif
+}
+
 /**
  * @brief Get an network interface's link address
  *