net: websocket: Add a way to unregister a websocket connection

Doing a normal close for a websocket does not close the underlying
real socket. If we do not have fd for the real socket, then it is
not possible to fully close a websocket connection. As we are allocating
a websocket using websocket_register() in HTTP server use case,
create a websocket_unregister() that will close both the real
socket and the websocket socket.

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>

include/zephyr/net/websocket.h

@@ -201,6 +201,17 @@ int websocket_disconnect(int ws_sock);
  */
 int websocket_register(int http_sock, uint8_t *recv_buf, size_t recv_buf_len);
 
+/**
+ * @brief Unregister a websocket. This is called when we no longer need
+ *        the underlaying "real" socket. This will close first the websocket
+ *        and then the original socket.
+ *
+ * @param ws_sock Websocket connection socket.
+ *
+ * @return <0 if error, 0 the websocket connection is now fully closed
+ */
+int websocket_unregister(int ws_sock);
+
 #if defined(CONFIG_WEBSOCKET_CLIENT)
 void websocket_init(void);
 #else

subsys/net/lib/websocket/websocket.c

@@ -1193,6 +1193,58 @@ out:
 	return ret;
 }
 
+static struct websocket_context *websocket_search(int sock)
+{
+	struct websocket_context *ctx = NULL;
+	int i;
+
+	k_sem_take(&contexts_lock, K_FOREVER);
+
+	for (i = 0; i < ARRAY_SIZE(contexts); i++) {
+		if (!websocket_context_is_used(&contexts[i])) {
+			continue;
+		}
+
+		if (contexts[i].sock != sock) {
+			continue;
+		}
+
+		ctx = &contexts[i];
+		break;
+	}
+
+	k_sem_give(&contexts_lock);
+
+	return ctx;
+}
+
+int websocket_unregister(int sock)
+{
+	struct websocket_context *ctx;
+
+	if (sock < 0) {
+		return -EINVAL;
+	}
+
+	ctx = websocket_search(sock);
+	if (ctx == NULL) {
+		NET_DBG("[%p] Real socket for websocket sock %d not found!", ctx, sock);
+		return -ENOENT;
+	}
+
+	if (ctx->real_sock < 0) {
+		return -EALREADY;
+	}
+
+	(void)zsock_close(sock);
+	(void)zsock_close(ctx->real_sock);
+
+	ctx->real_sock = -1;
+	ctx->sock = -1;
+
+	return 0;
+}
+
 static const struct socket_op_vtable websocket_fd_op_vtable = {
 	.fd_vtable = {
 		.read = websocket_read_vmeth,