Filter incoming UDP packets based on connected peer address.

Author: Seppo Takalo

features/netsocket/Socket.h

@@ -42,13 +42,18 @@ class Socket {
      */
     virtual nsapi_error_t close() = 0;
 
-    /** Connects socket to a remote host.
+    /** Connects socket to a remote address.
      *
-     *  Initiates a connection to a remote server specified by the
-     *  indicated address. In case of connectionless protocol, set
-     *  the remote address for next send() call.
+     *  Attempt to make connection on connection-mode protocol or set or reset
+     *  the peer address on connectionless protocol.
      *
-     *  @param address  The SocketAddress of the remote host
+     *  Also connectionless protocols use the connected address to filter
+     *  incoming packets for recv() and recvfrom() calls.
+     *
+     *  To reset the peer address, zero initialised(default constructor) SocketAddress
+     *  object have to be in the address parameter.
+     *
+     *  @param address  The SocketAddress of the remote peer
      *  @return         0 on success, negative error code on failure
      */
     virtual nsapi_error_t connect(const SocketAddress &address) = 0;
@@ -75,6 +80,11 @@ class Socket {
      *  Receive data from connected socket or in case of connectionless socket
      *  this is equivalent of calling recvfrom(NULL, data, size).
      *
+     *  If socket is connected, only packets coming from connected peer address
+     *  are accepted.
+     *
+     *  @note recv() is allowed write to data buffer even if error occurs.
+     *
      *  By default, recv blocks until some data is received. If socket is set to
      *  non-blocking or times out, NSAPI_ERROR_WOULD_BLOCK can be returned to
      *  indicate no data.
@@ -112,6 +122,11 @@ class Socket {
      *  Receives a data and stores the source address in address if address
      *  is not NULL. Returns the number of bytes written into the buffer.
      *
+     *  If socket is connected, only packets coming from connected peer address
+     *  are accepted.
+     *
+     *  @note recvfrom() is allowed write to address and data buffers even if error occurs.
+     *
      *  By default, recvfrom blocks until a datagram is received. If socket is set to
      *  non-blocking or times out with no data, NSAPI_ERROR_WOULD_BLOCK
      *  is returned.

features/netsocket/UDPSocket.cpp

@@ -122,6 +122,13 @@ nsapi_size_or_error_t UDPSocket::recvfrom(SocketAddress *address, void *buffer,
 
         _pending = 0;
         nsapi_size_or_error_t recv = _stack->socket_recvfrom(_socket, address, buffer, size);
+
+        // Filter incomming packets using connected peer address
+        if (recv >= 0 && _remote_peer && _remote_peer == *address) {
+            continue;
+        }
+
+        // Non-blocking sockets always return. Blocking only returns when success or errors other than WOULD_BLOCK
         if ((0 == _timeout) || (NSAPI_ERROR_WOULD_BLOCK != recv)) {
             ret = recv;
             break;

features/netsocket/UDPSocket.h

@@ -99,6 +99,11 @@ class UDPSocket : public InternetSocket {
      *  is not NULL. Returns the number of bytes written into the buffer. If the
      *  datagram is larger than the buffer, the excess data is silently discarded.
      *
+     *  If socket is connected, only packets coming from connected peer address
+     *  are accepted.
+     *
+     *  @note recvfrom() is allowed write to address and data buffers even if error occurs.
+     *
      *  By default, recvfrom blocks until a datagram is received. If socket is set to
      *  non-blocking or times out with no datagram, NSAPI_ERROR_WOULD_BLOCK
      *  is returned.
@@ -114,7 +119,9 @@ class UDPSocket : public InternetSocket {
 
     /** Set remote peer address
      *
-     *  Set the remote address for next send() call.
+     *  Set the remote address for next send() call and filtering
+     *  for incomming packets. To reset the address, zero initialised
+     *  SocketAddress must be in the address parameter.
      *
      *  @param address  The SocketAddress of the remote host
      *  @return         0 on success, negative error code on failure
@@ -141,6 +148,11 @@ class UDPSocket : public InternetSocket {
      *
      *  This is equivalent of calling recvfrom(NULL, data, size).
      *
+     *  If socket is connected, only packets coming from connected peer address
+     *  are accepted.
+     *
+     *  @note recv() is allowed write to data buffer even if error occurs.
+     *
      *  By default, recv blocks until some data is received. If socket is set to
      *  non-blocking or times out, NSAPI_ERROR_WOULD_BLOCK can be returned to
      *  indicate no data.