[neighbour] Always use network device's own link-layer address

The API for neighbour_tx() allows for an explicit source link-layer
address, but this will be ignored if the packet is deferred for
transmission after completion of neighbour discovery.  The network
device's own link-layer address will always be used when sending
neighbour discovery packets, and when sending any deferred packets
after discovery completes.

All callers pass in the network device's own link-layer address as the
source address anyway, and so this explicit source link-layer address
is never used for any meaningful purpose.

Simplify the neighbour_tx() API by removing the ability to pass in an
explicit source link-layer address.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/arp.h

@@ -45,16 +45,14 @@ extern struct neighbour_discovery arp_discovery;
  * @v net_protocol	Network-layer protocol
  * @v net_dest		Destination network-layer address
  * @v net_source	Source network-layer address
- * @v ll_source		Source link-layer address
  * @ret rc		Return status code
  */
 static inline int arp_tx ( struct io_buffer *iobuf, struct net_device *netdev,
 			   struct net_protocol *net_protocol,
-			   const void *net_dest, const void *net_source,
+			   const void *net_dest, const void *net_source ) {
-			   const void *ll_source ) {
 
 	return neighbour_tx ( iobuf, netdev, net_protocol, net_dest,
-			      &arp_discovery, net_source, ll_source );
+			      &arp_discovery, net_source );
 }
 
 extern int arp_tx_request ( struct net_device *netdev,

src/include/ipxe/ndp.h

@@ -189,15 +189,13 @@ extern struct neighbour_discovery ndp_discovery;
  * @v netdev		Network device
  * @v net_dest		Destination network-layer address
  * @v net_source	Source network-layer address
- * @v ll_source		Source link-layer address
  * @ret rc		Return status code
  */
 static inline int ndp_tx ( struct io_buffer *iobuf, struct net_device *netdev,
-			   const void *net_dest, const void *net_source,
+			   const void *net_dest, const void *net_source ) {
-			   const void *ll_source ) {
 
 	return neighbour_tx ( iobuf, netdev, &ipv6_protocol, net_dest,
-			      &ndp_discovery, net_source, ll_source );
+			      &ndp_discovery, net_source );
 }
 
 /** NDP settings block name */

src/include/ipxe/neighbour.h

@@ -77,7 +77,7 @@ extern int neighbour_tx ( struct io_buffer *iobuf, struct net_device *netdev,
 			  struct net_protocol *net_protocol,
 			  const void *net_dest,
 			  struct neighbour_discovery *discovery,
-			  const void *net_source, const void *ll_source );
+			  const void *net_source );
 extern int neighbour_update ( struct net_device *netdev,
 			      struct net_protocol *net_protocol,
 			      const void *net_dest, const void *ll_dest );

src/net/ipv4.c

@@ -563,7 +563,7 @@ static int ipv4_tx ( struct io_buffer *iobuf,
 		}
 	} else {
 		if ( ( rc = arp_tx ( iobuf, netdev, &ipv4_protocol, &next_hop,
-				     &iphdr->src, netdev->ll_addr ) ) != 0 ) {
+				     &iphdr->src ) ) != 0 ) {
 			DBGC ( sin_dest->sin_addr, "IPv4 could not transmit "
 			       "packet via %s: %s\n",
 			       netdev->name, strerror ( rc ) );

src/net/ipv6.c

@@ -617,8 +617,8 @@ static int ipv6_tx ( struct io_buffer *iobuf,
 			return rc;
 		}
 	} else {
-		if ( ( rc = ndp_tx ( iobuf, netdev, next_hop, &iphdr->src,
+		if ( ( rc = ndp_tx ( iobuf, netdev, next_hop,
-				     netdev->ll_addr ) ) != 0 ) {
+				     &iphdr->src ) ) != 0 ) {
 			DBGC ( ipv6col ( &iphdr->dest ), "IPv6 could not "
 			       "transmit packet via %s: %s\n",
 			       netdev->name, strerror ( rc ) );

src/net/neighbour.c

@@ -293,13 +293,12 @@ static void neighbour_expired ( struct retry_timer *timer, int fail ) {
  * @v net_protocol	Network-layer protocol
  * @v net_dest		Destination network-layer address
  * @v net_source	Source network-layer address
- * @v ll_source		Source link-layer address
  * @ret rc		Return status code
  */
 int neighbour_tx ( struct io_buffer *iobuf, struct net_device *netdev,
 		   struct net_protocol *net_protocol, const void *net_dest,
 		   struct neighbour_discovery *discovery,
-		   const void *net_source, const void *ll_source ) {
+		   const void *net_source ) {
 	struct neighbour *neighbour;
 
 	/* Find or create neighbour cache entry */
@@ -316,7 +315,7 @@ int neighbour_tx ( struct io_buffer *iobuf, struct net_device *netdev,
 	 */
 	if ( neighbour_has_ll_dest ( neighbour ) ) {
 		return net_tx ( iobuf, netdev, net_protocol, neighbour->ll_dest,
-				ll_source );
+				netdev->ll_addr );
 	} else {
 		DBGC2 ( neighbour, "NEIGHBOUR %s %s %s deferring packet\n",
 			netdev->name, net_protocol->name,