Add untested support for UNDI transmit and receive.

src/include/gpxe/arp.h

@@ -30,6 +30,8 @@ struct arp_net_protocol {
 #define __arp_net_protocol \
 	__table ( struct arp_net_protocol, arp_net_protocols, 01 )
 
+extern struct net_protocol arp_protocol;
+
 extern int arp_resolve ( struct net_device *netdev,
 			 struct net_protocol *net_protocol,
 			 const void *dest_net_addr,

src/include/gpxe/netdevice.h

@@ -122,6 +122,8 @@ struct ll_protocol {
 	uint16_t ll_proto;
 	/** Link-layer address length */
 	uint8_t ll_addr_len;
+	/** Link-layer header length */
+	uint8_t ll_header_len;
 	/** Link-layer broadcast address */
 	const uint8_t *ll_broadcast;
 };

src/include/gpxe/rarp.h

@@ -0,0 +1,14 @@
+#ifndef _GPXE_RARP_H
+#define _GPXE_RARP_H
+
+/** @file
+ *
+ * Reverse Address Resolution Protocol
+ *
+ */
+
+struct net_protocol;
+
+extern struct net_protocol rarp_protocol;
+
+#endif /* _GPXE_RARP_H */