network-socket: Optionally return peer address from accept().

Fixes issue #2399 by optionally returning a SocketAddress from
TCPServer::accept().

This entails changes to underlying NetworkStack and nsapi.  This
commit deals only with lwip and higher level APIs; other users of
NetworkStack and nsapi may be affected.  Currently lwip is the only
in-tree user of nsapi.

features/net/FEATURE_IPV4/lwip-interface/lwip_stack.c

@@ -292,7 +292,7 @@ static int lwip_socket_connect(nsapi_stack_t *stack, nsapi_socket_t handle, nsap
     return lwip_err_remap(err);
 }
 
-static int lwip_socket_accept(nsapi_stack_t *stack, nsapi_socket_t *handle, nsapi_socket_t server)
+static int lwip_socket_accept(nsapi_stack_t *stack, nsapi_socket_t server, nsapi_socket_t *handle, nsapi_addr_t *addr, uint16_t *port)
 {
     struct lwip_socket *s = (struct lwip_socket *)server;
     struct lwip_socket *ns = lwip_arena_alloc();
@@ -304,6 +304,10 @@ static int lwip_socket_accept(nsapi_stack_t *stack, nsapi_socket_t *handle, nsap
     }
 
     *(struct lwip_socket **)handle = ns;
+
+    (void) netconn_peer(ns->conn, (ip_addr_t *)addr->bytes, port);
+    addr->version = NSAPI_IPv4;
+
     return 0;
 }
 

features/net/network-socket/NetworkStack.cpp

@@ -159,13 +159,23 @@ protected:
         return _stack_api()->socket_connect(_stack(), socket, address.get_addr(), address.get_port());
     }
 
-    virtual int socket_accept(nsapi_socket_t *socket, nsapi_socket_t server)
+    virtual int socket_accept(nsapi_socket_t *socket, nsapi_socket_t server, SocketAddress *address)
     {
         if (!_stack_api()->socket_accept) {
             return NSAPI_ERROR_UNSUPPORTED;
         }
 
-        return _stack_api()->socket_accept(_stack(), socket, server);
+        nsapi_addr_t addr = {NSAPI_IPv4, 0};
+        uint16_t port = 0;
+
+        int err = _stack_api()->socket_accept(_stack(), server, socket, &addr, &port);
+
+        if (address) {
+            address->set_addr(addr);
+            address->set_port(port);
+        }
+
+        return err;
     }
 
     virtual int socket_send(nsapi_socket_t socket, const void *data, unsigned size)

features/net/network-socket/NetworkStack.h

@@ -160,11 +160,12 @@ protected:
      *  This call is non-blocking. If accept would block,
      *  NSAPI_ERROR_WOULD_BLOCK is returned immediately.
      *
-     *  @param handle   Destination for a handle to the newly created sockey
+     *  @param handle   Destination for a handle to the newly created socket
      *  @param server   Socket handle to server to accept from
+     *  @param address  Destination for the remote address or NULL
      *  @return         0 on success, negative error code on failure
      */
-    virtual int socket_accept(nsapi_socket_t *handle, nsapi_socket_t server) = 0;
+    virtual int socket_accept(nsapi_socket_t *handle, nsapi_socket_t server, SocketAddress *address=0) = 0;
 
     /** Send data over a TCP socket
      *

features/net/network-socket/TCPServer.cpp

@@ -47,7 +47,7 @@ int TCPServer::listen(int backlog)
     return ret;
 }
 
-int TCPServer::accept(TCPSocket *connection)
+int TCPServer::accept(TCPSocket *connection, SocketAddress *address)
 {
     _lock.lock();
     int ret;
@@ -60,7 +60,7 @@ int TCPServer::accept(TCPSocket *connection)
 
         _pending = 0;
         void *socket;
-        ret = _stack->socket_accept(&socket, _socket);
+        ret = _stack->socket_accept(&socket, _socket, address);
 
         if (0 == ret) {
             connection->_lock.lock();

features/net/network-socket/TCPServer.h

@@ -78,9 +78,10 @@ public:
      *  immediately.
      *
      *  @param socket   TCPSocket instance that will handle the incoming connection.
+     *  @param address  Destination for the remote address or NULL
      *  @return         0 on success, negative error code on failure
      */
-    int accept(TCPSocket *connection);
+    int accept(TCPSocket *connection, SocketAddress *address = NULL);
 
 protected:
     virtual nsapi_protocol_t get_proto();

features/net/network-socket/nsapi_types.h

@@ -310,11 +310,13 @@ typedef struct nsapi_stack_api
      *  NSAPI_ERROR_WOULD_BLOCK is returned immediately.
      *
      *  @param stack    Stack handle
-     *  @param socket   Destination for a handle to the newly created sockey
      *  @param server   Socket handle to server to accept from
+     *  @param socket   Destination for a handle to the newly created socket
+     *  @param addr     Destination for the address of the remote host
+     *  @param port     Destination for the port of the remote host
      *  @return         0 on success, negative error code on failure
      */
-    int (*socket_accept)(nsapi_stack_t *stack, nsapi_socket_t *socket, nsapi_socket_t server);
+    int (*socket_accept)(nsapi_stack_t *stack, nsapi_socket_t server, nsapi_socket_t *socket, nsapi_addr_t *addr, uint16_t *port);
 
     /** Send data over a TCP socket
      *