[tcpip] Allow for transmission to multicast IPv4 addresses

When sending to a multicast address, it may be necessary to specify
the source address explicitly, since the multicast destination address
does not provide enough information to deduce the source address via
the miniroute table.

Allow the source address specified via the data-xfer metadata to be
passed down through the TCP/IP stack to the IPv4 layer, which can use
it as a default source address.

src/include/gpxe/tcpip.h

 	 *
 	 * @v iobuf		I/O buffer
 	 * @v tcpip_protocol	Transport-layer protocol
+	 * @v st_src		Source address, or NULL to use default
 	 * @v st_dest		Destination address
 	 * @v netdev		Network device (or NULL to route automatically)
 	 * @v trans_csum	Transport-layer checksum to complete, or NULL
 	 */
 	int ( * tx ) ( struct io_buffer *iobuf,
 		       struct tcpip_protocol *tcpip_protocol,
+		       struct sockaddr_tcpip *st_src,
 		       struct sockaddr_tcpip *st_dest,
 		       struct net_device *netdev,
 		       uint16_t *trans_csum );
 extern int tcpip_rx ( struct io_buffer *iobuf, uint8_t tcpip_proto,
 		      struct sockaddr_tcpip *st_src,
 		      struct sockaddr_tcpip *st_dest, uint16_t pshdr_csum );
-extern int tcpip_tx ( struct io_buffer *iobuf, struct tcpip_protocol *tcpip, 
+extern int tcpip_tx ( struct io_buffer *iobuf, struct tcpip_protocol *tcpip,
+		      struct sockaddr_tcpip *st_src,
 		      struct sockaddr_tcpip *st_dest,
 		      struct net_device *netdev,
 		      uint16_t *trans_csum );

src/net/icmpv6.c

 	st_dest.sin6.sin6_addr.in6_u.u6_addr8[13] = 0xff;
 	
 	/* Send packet over IP6 */
-	return tcpip_tx ( iobuf, &icmp6_protocol, &st_dest.st,
+	return tcpip_tx ( iobuf, &icmp6_protocol, NULL, &st_dest.st,
 			  NULL, &nsolicit->csum );
 }
 

src/net/ipv4.c

  *
  * @v iobuf		I/O buffer
  * @v tcpip		Transport-layer protocol
+ * @v st_src		Source network-layer address
  * @v st_dest		Destination network-layer address
  * @v netdev		Network device to use if no route found, or NULL
  * @v trans_csum	Transport-layer checksum to complete, or NULL
  */
 static int ipv4_tx ( struct io_buffer *iobuf,
 		     struct tcpip_protocol *tcpip_protocol,
+		     struct sockaddr_tcpip *st_src,
 		     struct sockaddr_tcpip *st_dest,
 		     struct net_device *netdev,
 		     uint16_t *trans_csum ) {
 	struct iphdr *iphdr = iob_push ( iobuf, sizeof ( *iphdr ) );
+	struct sockaddr_in *sin_src = ( ( struct sockaddr_in * ) st_src );
 	struct sockaddr_in *sin_dest = ( ( struct sockaddr_in * ) st_dest );
 	struct ipv4_miniroute *miniroute;
 	struct in_addr next_hop;
 
 	/* Use routing table to identify next hop and transmitting netdev */
 	next_hop = iphdr->dest;
-	if ( ( miniroute = ipv4_route ( &next_hop ) ) ) {
+	if ( sin_src )
+		iphdr->src = sin_src->sin_addr;
+	if ( ( next_hop.s_addr != INADDR_BROADCAST ) &&
+	     ( ! IN_MULTICAST ( ntohl ( next_hop.s_addr ) ) ) &&
+	     ( ( miniroute = ipv4_route ( &next_hop ) ) != NULL ) ) {
 		iphdr->src = miniroute->address;
 		netdev = miniroute->netdev;
 	}

src/net/ipv6.c

  */
 static int ipv6_tx ( struct io_buffer *iobuf,
 		     struct tcpip_protocol *tcpip,
+		     struct sockaddr_tcpip *st_src __unused,
 		     struct sockaddr_tcpip *st_dest,
 		     struct net_device *netdev,
 		     uint16_t *trans_csum ) {

src/net/tcp.c

 	DBGC ( tcp, "\n" );
 
 	/* Transmit packet */
-	return tcpip_tx ( iobuf, &tcp_protocol, &tcp->peer, NULL,
+	return tcpip_tx ( iobuf, &tcp_protocol, NULL, &tcp->peer, NULL,
 			  &tcphdr->csum );
 }
 
 	DBGC ( tcp, "\n" );
 
 	/* Transmit packet */
-	return tcpip_tx ( iobuf, &tcp_protocol, st_dest,
+	return tcpip_tx ( iobuf, &tcp_protocol, NULL, st_dest,
 			  NULL, &tcphdr->csum );
 }
 

src/net/tcpip.c

  *
  * @v iobuf		I/O buffer
  * @v tcpip_protocol	Transport-layer protocol
+ * @v st_src		Source address, or NULL to use route default
  * @v st_dest		Destination address
  * @v netdev		Network device to use if no route found, or NULL
  * @v trans_csum	Transport-layer checksum to complete, or NULL
  * @ret rc		Return status code
  */
 int tcpip_tx ( struct io_buffer *iobuf, struct tcpip_protocol *tcpip_protocol,
-	       struct sockaddr_tcpip *st_dest, struct net_device *netdev,
-	       uint16_t *trans_csum ) {
+	       struct sockaddr_tcpip *st_src, struct sockaddr_tcpip *st_dest,
+	       struct net_device *netdev, uint16_t *trans_csum ) {
 	struct tcpip_net_protocol *tcpip_net;
 
 	/* Hand off packet to the appropriate network-layer protocol */
 	      tcpip_net < tcpip_net_protocols_end ; tcpip_net++ ) {
 		if ( tcpip_net->sa_family == st_dest->st_family ) {
 			DBG ( "TCP/IP sending %s packet\n", tcpip_net->name );
-			return tcpip_net->tx ( iobuf, tcpip_protocol, st_dest,
-					       netdev, trans_csum );
+			return tcpip_net->tx ( iobuf, tcpip_protocol, st_src,
+					       st_dest, netdev, trans_csum );
 		}
 	}
 	

src/net/udp.c

  *
  * @v udp		UDP connection
  * @v iobuf		I/O buffer
- * @v src_port		Source port, or 0 to use default
+ * @v src		Source address, or NULL to use default
  * @v dest		Destination address, or NULL to use default
  * @v netdev		Network device, or NULL to use default
  * @ret rc		Return status code
  */
 static int udp_tx ( struct udp_connection *udp, struct io_buffer *iobuf,
-		    unsigned int src_port, struct sockaddr_tcpip *dest,
+		    struct sockaddr_tcpip *src, struct sockaddr_tcpip *dest,
 		    struct net_device *netdev ) {
        	struct udp_header *udphdr;
 	size_t len;
 	}
 
 	/* Fill in default values if not explicitly provided */
-	if ( ! src_port )
-		src_port = udp->local.st_port;
+	if ( ! src )
+		src = &udp->local;
 	if ( ! dest )
 		dest = &udp->peer;
 
 	udphdr = iob_push ( iobuf, sizeof ( *udphdr ) );
 	len = iob_len ( iobuf );
 	udphdr->dest = dest->st_port;
-	udphdr->src = src_port;
+	udphdr->src = src->st_port;
 	udphdr->len = htons ( len );
 	udphdr->chksum = 0;
 	udphdr->chksum = tcpip_chksum ( udphdr, len );
 	       ntohs ( udphdr->len ) );
 
 	/* Send it to the next layer for processing */
-	if ( ( rc = tcpip_tx ( iobuf, &udp_protocol, dest, netdev,
+	if ( ( rc = tcpip_tx ( iobuf, &udp_protocol, src, dest, netdev,
 			       &udphdr->chksum ) ) != 0 ) {
 		DBGC ( udp, "UDP %p could not transmit packet: %s\n",
 		       udp, strerror ( rc ) );
 				  struct xfer_metadata *meta ) {
 	struct udp_connection *udp =
 		container_of ( xfer, struct udp_connection, xfer );
-	struct sockaddr_tcpip *src;
+	struct sockaddr_tcpip *src = NULL;
 	struct sockaddr_tcpip *dest = NULL;
 	struct net_device *netdev = NULL;
-	unsigned int src_port = 0;
 
 	/* Apply xfer metadata */
 	if ( meta ) {
 		src = ( struct sockaddr_tcpip * ) meta->src;
-		if ( src )
-			src_port = src->st_port;
 		dest = ( struct sockaddr_tcpip * ) meta->dest;
 		netdev = meta->netdev;
 	}
 
 	/* Transmit data, if possible */
-	udp_tx ( udp, iobuf, src_port, dest, netdev );
+	udp_tx ( udp, iobuf, src, dest, netdev );
 
 	return 0;
 }