[udp] Verify local socket address (if specified) for UDP sockets

UDP sockets can be used for multicast, at which point it becomes
plausible that we could receive packets that aren't destined for us
but that still match on a port number.

src/include/gpxe/in.h

 	uint16_t sin_port;
 	/** IPv4 address */
 	struct in_addr sin_addr;
+	/** Padding
+	 *
+	 * This ensures that a struct @c sockaddr_tcpip is large
+	 * enough to hold a socket address for any TCP/IP address
+	 * family.
+	 */
+	char pad[ sizeof ( struct sockaddr ) - sizeof ( sa_family_t )
+					     - sizeof ( uint16_t )
+					     - sizeof ( struct in_addr ) ];
 };
 
 /**

src/net/udp.c

 	/** Data transfer interface */
 	struct xfer_interface xfer;
 
+	/** Local socket address */
+	struct sockaddr_tcpip local;
 	/** Remote socket address */
 	struct sockaddr_tcpip peer;
-	/** Local port on which the connection receives packets */
-	unsigned int local_port;
 };
 
 /**
  * Bind UDP connection to local port
  *
  * @v udp		UDP connection
- * @v port		Local port, in network byte order, or zero
  * @ret rc		Return status code
  *
- * Opens the UDP connection and binds to a local port.  If no local
- * port is specified, the first available port will be used.
+ * Opens the UDP connection and binds to the specified local port.  If
+ * no local port is specified, the first available port will be used.
  */
-static int udp_bind ( struct udp_connection *udp, unsigned int port ) {
+static int udp_bind ( struct udp_connection *udp ) {
 	struct udp_connection *existing;
 	static uint16_t try_port = 1024;
 
 	/* If no port specified, find the first available port */
-	if ( ! port ) {
+	if ( ! udp->local.st_port ) {
 		for ( ; try_port ; try_port++ ) {
 			if ( try_port < 1024 )
 				continue;
-			if ( udp_bind ( udp, htons ( try_port ) ) == 0 )
+			udp->local.st_port = htons ( try_port );
+			if ( udp_bind ( udp ) == 0 )
 				return 0;
 		}
 		return -EADDRINUSE;
 
 	/* Attempt bind to local port */
 	list_for_each_entry ( existing, &udp_conns, list ) {
-		if ( existing->local_port == port ) {
+		if ( existing->local.st_port == udp->local.st_port ) {
 			DBGC ( udp, "UDP %p could not bind: port %d in use\n",
-			       udp, ntohs ( port ) );
+			       udp, ntohs ( udp->local.st_port ) );
 			return -EADDRINUSE;
 		}
 	}
-	udp->local_port = port;
 
 	/* Add to UDP connection list */
-	DBGC ( udp, "UDP %p bound to port %d\n", udp, ntohs ( port ) );
+	DBGC ( udp, "UDP %p bound to port %d\n",
+	       udp, ntohs ( udp->local.st_port ) );
 
 	return 0;
 }
 	struct sockaddr_tcpip *st_peer = ( struct sockaddr_tcpip * ) peer;
 	struct sockaddr_tcpip *st_local = ( struct sockaddr_tcpip * ) local;
 	struct udp_connection *udp;
-	unsigned int bind_port;
 	int rc;
 
 	/* Allocate and initialise structure */
 	xfer_init ( &udp->xfer, &udp_xfer_operations, &udp->refcnt );
 	if ( st_peer )
 		memcpy ( &udp->peer, st_peer, sizeof ( udp->peer ) );
+	if ( st_local )
+		memcpy ( &udp->local, st_local, sizeof ( udp->local ) );
 
 	/* Bind to local port */
 	if ( ! promisc ) {
-		bind_port = ( st_local ? st_local->st_port : 0 );
-		if ( ( rc = udp_bind ( udp, bind_port ) ) != 0 )
+		if ( ( rc = udp_bind ( udp ) ) != 0 )
 			goto err;
 	}
 
 
 	/* Fill in default values if not explicitly provided */
 	if ( ! src_port )
-		src_port = udp->local_port;
+		src_port = udp->local.st_port;
 	if ( ! dest )
 		dest = &udp->peer;
 
 }
 
 /**
- * Identify UDP connection by local port number
+ * Identify UDP connection by local address
  *
- * @v local_port	Local port (in network-endian order)
+ * @v local		Local address
  * @ret udp		UDP connection, or NULL
  */
-static struct udp_connection * udp_demux ( unsigned int local_port ) {
+static struct udp_connection * udp_demux ( struct sockaddr_tcpip *local ) {
+	static const struct sockaddr_tcpip empty_sockaddr;
 	struct udp_connection *udp;
 
 	list_for_each_entry ( udp, &udp_conns, list ) {
-		if ( ( udp->local_port == local_port ) ||
-		     ( udp->local_port == 0 ) ) {
+		if ( ( ( udp->local.st_family == local->st_family ) ||
+		       ( udp->local.st_family == 0 ) ) &&
+		     ( ( udp->local.st_port == local->st_port ) ||
+		       ( udp->local.st_port == 0 ) ) &&
+		     ( ( memcmp ( udp->local.pad, local->pad,
+				  sizeof ( udp->local.pad ) ) == 0 ) ||
+		       ( memcmp ( udp->local.pad, empty_sockaddr.pad,
+				  sizeof ( udp->local.pad ) ) == 0 ) ) ) {
 			return udp;
 		}
 	}
 	/* Parse parameters from header and strip header */
 	st_src->st_port = udphdr->src;
 	st_dest->st_port = udphdr->dest;
-	udp = udp_demux ( udphdr->dest );
+	udp = udp_demux ( st_dest );
 	iob_unput ( iobuf, ( iob_len ( iobuf ) - ulen ) );
 	iob_pull ( iobuf, sizeof ( *udphdr ) );