Simplify RX data path.

Kill off the static single net device and move to proper dynamic
registration (which we need with the new device model).

Break the (flawed) assumption that all network-layer protocols can use
ARP; such network-layer protocols (i.e. IPv4) must now register as an ARP
protocol using ARP_NET_PROTOCOL() and provide a single method for checking
the existence of a local network-layer address.

src/core/main.c

 static int initialized;
 
 
-extern struct net_device static_single_netdev;
-
-
 /**************************************************************************
 MAIN - Kick off routine
 **************************************************************************/
 	call_init_fns ();
 	probe_devices();
 
-	/* Quick hack until netdevice.c uses proper dynamic registration */
-	netdev = &static_single_netdev;
-	if ( ! netdev->poll )
-		netdev = NULL;
-
+	netdev = next_netdev ();
 	if ( netdev ) {
-		test_aoeboot ( &static_single_netdev );
+		test_aoeboot ( netdev );
 	} else {
 		printf ( "No network device found\n" );
 	}

src/include/gpxe/arp.h

  *
  */
 
+#include <gpxe/tables.h>
+
 struct net_device;
 struct net_protocol;
 
+/** A network-layer protocol that relies upon ARP */
+struct arp_net_protocol {
+	/** Network-layer protocol */
+	struct net_protocol *net_protocol;
+	/** Check existence of address
+	 *
+	 * @v netdev	Network device
+	 * @v net_addr	Network-layer address
+	 * @ret rc	Return status code
+	 */
+	int ( * check ) ( struct net_device *netdev,
+			  const void *net_addr );
+};
+
+/**
+ * Register an ARP protocol
+ *
+ * @v protocol		ARP protocol
+ */
+#define ARP_NET_PROTOCOL( protocol ) \
+	struct arp_net_protocol protocol __table ( arp_net_protocols, 01 )
+
 extern int arp_resolve ( struct net_device *netdev,
 			 struct net_protocol *net_protocol,
 			 const void *dest_net_addr,

src/include/gpxe/ethernet.h

  * @v priv_size		Size of driver private data
  * @ret netdev		Network device, or NULL
  */
-#define alloc_etherdev( priv_size ) ( {				\
-	struct net_device *netdev;				\
-	netdev = alloc_netdev ( priv_size );			\
-	if ( netdev )						\
-		netdev->ll_protocol = &ethernet_protocol;	\
-	netdev;	} )
+static inline struct net_device * alloc_etherdev ( size_t priv_size ) {
+	struct net_device *netdev;
+
+	netdev = alloc_netdev ( priv_size );
+	if ( netdev ) {
+		netdev->ll_protocol = &ethernet_protocol;
+	}
+	return netdev;
+}
 
 #endif /* _GPXE_ETHERNET_H */

src/include/gpxe/ip.h

  *
  */
 
+#include <ip.h>
+
 struct net_protocol;
 
 extern struct net_protocol ipv4_protocol;
 			      struct in_addr address, struct in_addr netmask,
 			      struct in_addr gateway );
 extern void del_ipv4_address ( struct net_device *netdev );
-extern int ipv4_uip_transmit ( struct pk_buff *pkb );
+extern int ipv4_uip_tx ( struct pk_buff *pkb );
 
 #endif /* _GPXE_IP_H */

src/include/gpxe/netdevice.h

  */
 
 #include <stdint.h>
+#include <gpxe/list.h>
 #include <gpxe/tables.h>
 
 struct pk_buff;
 /** Maximum length of a network-layer address */
 #define MAX_NET_ADDR_LEN 4
 
-/* Network-layer address may be required to hold a link-layer address
- * (if NETADDR_FL_RAW is set
- */
-#if MAX_NET_ADDR_LEN < MAX_LL_ADDR_LEN
-#undef MAX_NET_ADDR_LEN
-#define MAX_NET_ADDR_LEN MAX_LL_ADDR_LEN
-#endif
-
-/** A generic network-layer header */
-struct net_header {
-	/** Network-layer protocol */
-	struct net_protocol *net_protocol;
-	/** Flags
-	 *
-	 * This is the bitwise OR of zero or more PKT_FL_XXX
-	 * values.
-	 */
-	int flags;
-	/** Network-layer destination address */
-	uint8_t dest_net_addr[MAX_NET_ADDR_LEN];
-	/** Network-layer source address */
-	uint8_t source_net_addr[MAX_NET_ADDR_LEN];
-};
-
-/** Packet is a broadcast packet */
-#define PKT_FL_BROADCAST 0x01
-
-/** Packet is a multicast packet */
-#define PKT_FL_MULTICAST 0x02
-
-/** Addresses are raw hardware addresses */
-#define PKT_FL_RAW_ADDR 0x04
-
-/** A generic link-layer header */
-struct ll_header {
-	/** Link-layer protocol */
-	struct ll_protocol *ll_protocol;
-	/** Flags
-	 *
-	 * This is the bitwise OR of zero or more PKT_FL_XXX
-	 * values.
-	 */
-	int flags;
-	/** Link-layer destination address */
-	uint8_t dest_ll_addr[MAX_LL_ADDR_LEN];
-	/** Link-layer source address */
-	uint8_t source_ll_addr[MAX_LL_ADDR_LEN];
-	/** Network-layer protocol
-	 *
-	 *
-	 * This is an ETH_P_XXX constant, in network-byte order
-	 */
-	uint16_t net_proto;
-};
-
 /**
  * A network-layer protocol
  *
 	 * Process received packet
 	 *
 	 * @v pkb	Packet buffer
-	 * @ret rc	Return status code
+	 * @v netdev	Network device
+	 * @v ll_source	Link-layer source address
 	 *
 	 * This method takes ownership of the packet buffer.
 	 */
-	int ( * rx_process ) ( struct pk_buff *pkb );
+	int ( * rx ) ( struct pk_buff *pkb, struct net_device *netdev,
+		       const void *ll_source );
 	/**
 	 * Transcribe network-layer address
 	 *
 	/**
 	 * Transmit network-layer packet via network device
 	 *
-	 *
 	 * @v pkb		Packet buffer
 	 * @v netdev		Network device
 	 * @v net_protocol	Network-layer protocol
 	 * This method should prepend in the link-layer header
 	 * (e.g. the Ethernet DIX header) and transmit the packet.
 	 */
-	int ( * transmit ) ( struct pk_buff *pkb, struct net_device *netdev,
-			     struct net_protocol *net_protocol,
-			     const void *ll_dest );
+	int ( * tx ) ( struct pk_buff *pkb, struct net_device *netdev,
+		       struct net_protocol *net_protocol,
+		       const void *ll_dest );
 	/**
-	 * Parse media-specific link-layer header
+	 * Handle received packet
 	 *
 	 * @v pkb	Packet buffer
-	 * @v llhdr	Generic link-layer header
+	 * @v netdev	Network device
 	 *
-	 * This method should fill in the generic link-layer header
-	 * based on information in the link-layer header in the packet
-	 * buffer.
+	 * This method should strip off the link-layer header
+	 * (e.g. the Ethernet DIX header) and pass the packet to
+	 * net_rx().
 	 */
-	void ( * parse_llh ) ( const struct pk_buff *pkb,
-			       struct ll_header *llhdr );
-
+	void ( * rx ) ( struct pk_buff *pkb, struct net_device *netdev );
 	/**
 	 * Transcribe link-layer address
 	 *
 	 * The buffer used to hold the transcription is statically
 	 * allocated.
 	 */
-	const char * ( *ntoa ) ( const void * ll_addr );
+	const char * ( * ntoa ) ( const void * ll_addr );
 	/** Link-layer protocol
 	 *
 	 * This is an ARPHRD_XXX constant, in network byte order.
 	const uint8_t *ll_broadcast;
 };
 
-/**
- * A network-layer address assigned to a network device
- *
- */
-struct net_address {
-	/** Network-layer protocol */
-	struct net_protocol *net_protocol;
-	/** Network-layer address */
-	uint8_t net_addr[MAX_NET_ADDR_LEN];
-};
-
 /**
  * A network device
  *
  * not just an Ethernet device.
  */
 struct net_device {
+	/** List of network devices */
+	struct list_head list;
 	/** Transmit packet
 	 *
 	 * @v netdev	Network device
 	 */
 	uint8_t ll_addr[MAX_LL_ADDR_LEN];
 
+	/** Received packet queue */
+	struct list_head rx_queue;
+
 	/** Driver private data */
 	void *priv;
 };
 
-extern struct net_device static_single_netdev;
-
-/**
- * Allocate network device
- *
- * @v priv_size		Size of private data area (net_device::priv)
- * @ret netdev		Network device, or NULL
- *
- * Allocates space for a network device and its private data area.
- *
- * This macro allows for a very efficient implementation in the case
- * of a single static network device; it neatly avoids dynamic
- * allocation and can never return failure, meaning that the failure
- * path will be optimised away.  However, driver writers should not
- * rely on this feature; the drivers should be written to allow for
- * multiple instances of network devices.
- */
-#define alloc_netdev( priv_size ) ( {		\
-	static char priv_data[priv_size];	\
-	static_single_netdev.priv = priv_data;	\
-	&static_single_netdev; } )
-
-/**
- * Free network device
- *
- * @v netdev		Network device
- */
-static inline void
-free_netdev ( struct net_device *netdev __attribute__ (( unused )) ) {
-	/* Nothing to do */
-}
-
-/**
- * Transmit raw packet via network device
- *
- * @v netdev		Network device
- * @v pkb		Packet buffer
- * @ret rc		Return status code
- *
- * Transmits the packet via the specified network device.  The
- * link-layer header must already have been filled in.  This function
- * takes ownership of the packet buffer.
- */
-static inline int netdev_transmit ( struct net_device *netdev,
-				    struct pk_buff *pkb ) {
-	return netdev->transmit ( netdev, pkb );
-}
-
-/**
- * Transmit network-layer packet
- *
- * @v pkb		Packet buffer
- * @v netdev		Network device
- * @v net_protocol	Network-layer protocol
- * @v ll_dest		Destination link-layer address
- * @ret rc		Return status code
- *
- * Prepends link-layer headers to the packet buffer and transmits the
- * packet via the specified network device.  This function takes
- * ownership of the packet buffer.
- */
-static inline int net_transmit ( struct pk_buff *pkb,
-				 struct net_device *netdev,
-				 struct net_protocol *net_protocol,
-				 const void *ll_dest ) {
-	return netdev->ll_protocol->transmit ( pkb, netdev, net_protocol,
-					       ll_dest );
-}
-
 /**
  * Register a link-layer protocol
  *
 	struct net_protocol protocol __table ( net_protocols, 01 )
 
 /**
- * Register a network-layer address for the static single network device
+ * Get network device name
+ *
+ * @v netdev		Network device
+ * @ret name		Network device name
  *
- * @v net_address	Network-layer address
+ * The name will be the device's link-layer address.
  */
-#define STATIC_SINGLE_NETDEV_ADDRESS( address ) \
-	struct net_address address __table ( sgl_netdev_addresses, 01 )
+static inline const char * netdev_name ( struct net_device *netdev ) {
+	return netdev->ll_protocol->ntoa ( netdev->ll_addr );
+}
 
+extern int netdev_tx ( struct net_device *netdev, struct pk_buff *pkb );
+extern void netdev_rx ( struct net_device *netdev, struct pk_buff *pkb );
+extern int net_tx ( struct pk_buff *pkb, struct net_device *netdev,
+		    struct net_protocol *net_protocol, const void *ll_dest );
+extern void net_rx ( struct pk_buff *pkb, struct net_device *netdev,
+		     uint16_t net_proto, const void *ll_source );
+extern int netdev_poll ( struct net_device *netdev );
+extern struct pk_buff * netdev_rx_dequeue ( struct net_device *netdev );
+extern struct net_device * alloc_netdev ( size_t priv_size );
 extern int register_netdev ( struct net_device *netdev );
 extern void unregister_netdev ( struct net_device *netdev );
-extern void netdev_rx ( struct net_device *netdev, struct pk_buff *pkb );
-
-extern struct net_protocol *find_net_protocol ( uint16_t net_proto );
-extern struct net_device *
-find_netdev_by_net_addr ( struct net_protocol *net_protocol, void *net_addr );
-
-extern int net_poll ( void );
-extern struct pk_buff * net_rx_dequeue ( void );
-extern int net_rx_process ( struct pk_buff *pkb );
+extern void free_netdev ( struct net_device *netdev );
+extern struct net_device * next_netdev ( void );
 
 #endif /* _GPXE_NETDEVICE_H */

src/include/gpxe/pkbuff.h

 #include <assert.h>
 #include <gpxe/list.h>
 
-struct net_protocol;
-struct ll_protocol;
-
 /**
  * Packet buffer alignment
  *
  * This structure is used to represent a network packet within gPXE.
  */
 struct pk_buff {
+	/** List of which this buffer is a member */
+	struct list_head list;
+
 	/** Start of the buffer */
 	void *head;
 	/** Start of data */
 	void *tail;
 	/** End of the buffer */
         void *end;
-
-	/** List of which this buffer is a member */
-	struct list_head list;
-
-	/** The network-layer protocol */
-	struct net_protocol *net_protocol;
-	/** The link-layer protocol */
-	struct ll_protocol *ll_protocol;
 };
 
 /**

src/net/aoe.c

 			  data_out_len );
 	if ( ! pkb )
 		return -ENOMEM;
-	pkb->net_protocol = &aoe_protocol;
 	pkb_reserve ( pkb, ETH_HLEN );
 	aoehdr = pkb_put ( pkb, sizeof ( *aoehdr ) );
 	aoecmd = pkb_put ( pkb, sizeof ( *aoecmd ) );
 
 	/* Send packet */
 	start_timer ( &aoe->timer );
-	return net_transmit ( pkb, aoe->netdev, &aoe_protocol, aoe->target );
+	return net_tx ( pkb, aoe->netdev, &aoe_protocol, aoe->target );
 }
 
 /**
  * Process incoming AoE packets
  *
  * @v pkb		Packet buffer
+ * @v netdev		Network device
+ * @v ll_source		Link-layer source address
  * @ret rc		Return status code
  *
  */
-static int aoe_rx ( struct pk_buff *pkb ) {
+static int aoe_rx ( struct pk_buff *pkb, struct net_device *netdev __unused,
+		    const void *ll_source ) {
 	struct aoehdr *aoehdr = pkb->data;
 	unsigned int len = pkb_len ( pkb );
-	struct ethhdr *ethhdr = pkb_push ( pkb, sizeof ( *ethhdr ) );
 	struct aoe_session *aoe;
 	int rc = 0;
 
 			continue;
 		if ( ntohl ( aoehdr->tag ) != aoe->tag )
 			continue;
-		memcpy ( aoe->target, ethhdr->h_source,
-			 sizeof ( aoe->target ) );
+		memcpy ( aoe->target, ll_source, sizeof ( aoe->target ) );
 		rc = aoe_rx_response ( aoe, aoehdr, len );
 		break;
 	}
 struct net_protocol aoe_protocol = {
 	.name = "AoE",
 	.net_proto = htons ( ETH_P_AOE ),
-	.rx_process = aoe_rx,
+	.rx = aoe_rx,
 };
 
 NET_PROTOCOL ( aoe_protocol );

src/net/arp.c

  *
  */
 
+/** Registered ARP protocols */
+static struct arp_net_protocol arp_net_protocols[0]
+	__table_start ( arp_net_protocols );
+static struct arp_net_protocol arp_net_protocols_end[0]
+	__table_end ( arp_net_protocols );
+
 /** An ARP cache entry */
 struct arp_entry {
 	/** Network-layer protocol */
 			  2 * ( MAX_LL_ADDR_LEN + MAX_NET_ADDR_LEN ) );
 	if ( ! pkb )
 		return -ENOMEM;
-	pkb->net_protocol = &arp_protocol;
 	pkb_reserve ( pkb, MAX_LL_HEADER_LEN );
 
 	/* Build up ARP request */
 		 dest_net_addr, net_protocol->net_addr_len );
 
 	/* Transmit ARP request */
-	if ( ( rc = net_transmit ( pkb, netdev, &arp_protocol, 
-				   ll_protocol->ll_broadcast ) ) != 0 )
+	if ( ( rc = net_tx ( pkb, netdev, &arp_protocol, 
+			     ll_protocol->ll_broadcast ) ) != 0 )
 		return rc;
 
 	return -ENOENT;
 }
 
+/**
+ * Identify ARP protocol
+ *
+ * @v net_proto			Network-layer protocol, in network-endian order
+ * @ret arp_net_protocol	ARP protocol, or NULL
+ *
+ */
+static struct arp_net_protocol * arp_find_protocol ( uint16_t net_proto ) {
+	struct arp_net_protocol *arp_net_protocol;
+
+	for ( arp_net_protocol = arp_net_protocols ;
+	      arp_net_protocol < arp_net_protocols_end ; arp_net_protocol++ ) {
+		if ( arp_net_protocol->net_protocol->net_proto == net_proto ) {
+			return arp_net_protocol;
+		}
+	}
+	return NULL;
+}
+
 /**
  * Process incoming ARP packets
  *
  * @v pkb		Packet buffer
+ * @v netdev		Network device
+ * @v ll_source		Link-layer source address
  * @ret rc		Return status code
  *
  * This handles ARP requests and responses as detailed in RFC826.  The
  * avoiding the need for extraneous ARP requests; read the RFC for
  * details.
  */
-static int arp_rx ( struct pk_buff *pkb ) {
+static int arp_rx ( struct pk_buff *pkb, struct net_device *netdev,
+		    const void *ll_source __unused ) {
 	struct arphdr *arphdr = pkb->data;
-	struct ll_protocol *ll_protocol;
+	struct arp_net_protocol *arp_net_protocol;
 	struct net_protocol *net_protocol;
+	struct ll_protocol *ll_protocol;
 	struct arp_entry *arp;
-	struct net_device *netdev;
 	int merge = 0;
 
-	/* Identify link-layer and network-layer protocols */
-	ll_protocol = pkb->ll_protocol;
-	net_protocol = find_net_protocol ( arphdr->ar_pro );
-	if ( ! net_protocol )
+	/* Identify network-layer and link-layer protocols */
+	arp_net_protocol = arp_find_protocol ( arphdr->ar_pro );
+	if ( ! arp_net_protocol )
 		goto done;
+	net_protocol = arp_net_protocol->net_protocol;
+	ll_protocol = netdev->ll_protocol;
 
 	/* Sanity checks */
 	if ( ( arphdr->ar_hrd != ll_protocol->ll_proto ) ||
 	}
 
 	/* See if we own the target protocol address */
-	netdev = find_netdev_by_net_addr ( net_protocol,
-					   arp_target_pa ( arphdr ) );
-	if ( ! netdev )
+	if ( arp_net_protocol->check ( netdev, arp_target_pa ( arphdr ) ) != 0)
 		goto done;
 	
 	/* Create new ARP table entry if necessary */
 	memcpy ( arp_sender_ha ( arphdr ), netdev->ll_addr, arphdr->ar_hln );
 
 	/* Send reply */
-	net_transmit ( pkb, netdev, &arp_protocol, arp_target_ha (arphdr ) );
+	net_tx ( pkb, netdev, &arp_protocol, arp_target_ha (arphdr ) );
 	pkb = NULL;
 
  done:
 struct net_protocol arp_protocol = {
 	.name = "ARP",
 	.net_proto = htons ( ETH_P_ARP ),
-	.rx_process = arp_rx,
+	.rx = arp_rx,
 	.ntoa = arp_ntoa,
 };
 

src/net/ethernet.c

  *
  * Prepends the Ethernet link-layer header and transmits the packet.
  */
-static int eth_transmit ( struct pk_buff *pkb, struct net_device *netdev,
-			  struct net_protocol *net_protocol,
-			  const void *ll_dest ) {
+static int eth_tx ( struct pk_buff *pkb, struct net_device *netdev,
+		    struct net_protocol *net_protocol, const void *ll_dest ) {
 	struct ethhdr *ethhdr = pkb_push ( pkb, sizeof ( *ethhdr ) );
 
+	/* Build Ethernet header */
 	memcpy ( ethhdr->h_dest, ll_dest, ETH_ALEN );
 	memcpy ( ethhdr->h_source, netdev->ll_addr, ETH_ALEN );
 	ethhdr->h_protocol = net_protocol->net_proto;
-	return netdev_transmit ( netdev, pkb );
+
+	/* Hand off to network device */
+	return netdev_tx ( netdev, pkb );
 }
 
 /**
- * Parse Ethernet link-layer header
+ * Process received Ethernet packet
  *
  * @v pkb	Packet buffer
- * @v llhdr	Generic link-layer header
+ * @v netdev	Network device
  *
- * Fills in the generic link-layer header based on information in the
- * Ethernet link-layer header in the packet buffer.
+ * Strips off the Ethernet link-layer header and passes up to the
+ * network-layer protocol.
  */
-static void eth_parse_llh ( const struct pk_buff *pkb,
-			    struct ll_header *llhdr ) {
+static void eth_rx ( struct pk_buff *pkb, struct net_device *netdev ) {
 	struct ethhdr *ethhdr = pkb->data;
 
-	memcpy ( llhdr->dest_ll_addr, ethhdr->h_dest, ETH_ALEN );
-	memcpy ( llhdr->source_ll_addr, ethhdr->h_source, ETH_ALEN );
-	llhdr->net_proto = ethhdr->h_protocol;
-
-	if ( memcmp ( ethhdr->h_dest, eth_broadcast, ETH_ALEN ) == 0 ) {
-		llhdr->flags = PKT_FL_BROADCAST;
-	} else if ( ethhdr->h_dest[0] & 0x01 ) {
-		llhdr->flags = PKT_FL_MULTICAST;
-	} else {
-		llhdr->flags = 0;
+	/* Sanity check */
+	if ( pkb_len ( pkb ) < sizeof ( *ethhdr ) ) {
+		DBG ( "Ethernet packet too short (%d bytes)\n",
+		      pkb_len ( pkb ) );
+		return;
 	}
+
+	/* Strip off Ethernet header */
+	pkb_pull ( pkb, sizeof ( *ethhdr ) );
+
+	/* Hand off to network-layer protocol */
+	net_rx ( pkb, netdev, ethhdr->h_protocol, ethhdr->h_source );
 }
 
 /**
 	.ll_proto	= htons ( ARPHRD_ETHER ),
 	.ll_addr_len	= ETH_ALEN,
 	.ll_broadcast	= eth_broadcast,
-	.transmit	= eth_transmit,
-	.parse_llh	= eth_parse_llh,
+	.tx		= eth_tx,
+	.rx		= eth_rx,
 	.ntoa		= eth_ntoa,
 };
 

src/net/ipv4.c

 #include <gpxe/list.h>
 #include <gpxe/in.h>
 #include <gpxe/arp.h>
-
-#include <ip.h>
-
-
 #include <gpxe/if_ether.h>
 #include <gpxe/pkbuff.h>
 #include <gpxe/netdevice.h>
  * @ret rc		Return status code
  *
  */
-int ipv4_uip_transmit ( struct pk_buff *pkb ) {
+int ipv4_uip_tx ( struct pk_buff *pkb ) {
 	struct iphdr *iphdr = pkb->data;
 	struct ipv4_miniroute *miniroute;
 	struct net_device *netdev = NULL;
 	}
 	
 	/* Hand off to link layer */
-	return net_transmit ( pkb, netdev, &ipv4_protocol, ll_dest );
+	return net_tx ( pkb, netdev, &ipv4_protocol, ll_dest );
 
  err:
 	free_pkb ( pkb );
  * Process incoming IP packets
  *
  * @v pkb		Packet buffer
+ * @v netdev		Network device
+ * @v ll_source		Link-layer source address
  * @ret rc		Return status code
  *
  * This handles IP packets by handing them off to the uIP protocol
  * stack.
  */
-static int ipv4_rx ( struct pk_buff *pkb ) {
+static int ipv4_rx ( struct pk_buff *pkb, struct net_device *netdev __unused,
+		     const void *ll_source __unused ) {
 
 	/* Transfer to uIP buffer.  Horrendously space-inefficient,
 	 * but will do as a proof-of-concept for now.
 			return -ENOMEM;
 		pkb_reserve ( pkb, MAX_LL_HEADER_LEN );
 		memcpy ( pkb_put ( pkb, uip_len ), uip_buf, uip_len );
-		ipv4_uip_transmit ( pkb );
+		ipv4_uip_tx ( pkb );
 	}
 	return 0;
 }
 
+/** 
+ * Check existence of IPv4 address for ARP
+ *
+ * @v netdev		Network device
+ * @v net_addr		Network-layer address
+ * @ret rc		Return status code
+ */
+static int ipv4_arp_check ( struct net_device *netdev, const void *net_addr ) {
+	const struct in_addr *address = net_addr;
+	struct ipv4_miniroute *miniroute;
+
+	list_for_each_entry ( miniroute, &miniroutes, list ) {
+		if ( ( miniroute->netdev == netdev ) &&
+		     ( miniroute->address.s_addr == address->s_addr ) ) {
+			/* Found matching address */
+			return 0;
+		}
+	}
+	return -ENOENT;
+}
+
 /**
  * Convert IPv4 address to dotted-quad notation
  *
 	.name = "IP",
 	.net_proto = htons ( ETH_P_IP ),
 	.net_addr_len = sizeof ( struct in_addr ),
-	.rx_process = ipv4_rx,
+	.rx = ipv4_rx,
 	.ntoa = ipv4_ntoa,
 };
 
 NET_PROTOCOL ( ipv4_protocol );
 
-/** IPv4 address for the static single net device */
-struct net_address static_single_ipv4_address = {
+/** IPv4 ARP protocol */
+struct arp_net_protocol ipv4_arp_protocol = {
 	.net_protocol = &ipv4_protocol,
-
-#warning "Remove this static-IP hack"
-	.net_addr = { 0x0a, 0xfe, 0xfe, 0x01 },
+	.check = ipv4_arp_check,
 };
 
-STATIC_SINGLE_NETDEV_ADDRESS ( static_single_ipv4_address );
+ARP_NET_PROTOCOL ( ipv4_arp_protocol );

src/net/netdevice.c

 #include <byteswap.h>
 #include <string.h>
 #include <errno.h>
+#include <malloc.h>
 #include <gpxe/if_ether.h>
 #include <gpxe/pkbuff.h>
 #include <gpxe/tables.h>
  *
  */
 
-/**
- * Static single instance of a network device
- *
- * The gPXE API is designed to accommodate multiple network devices.
- * However, in the interests of code size, the implementation behind
- * the API supports only a single instance of a network device.
- *
- * No code outside of netdevice.c should ever refer directly to @c
- * static_single_netdev.
- *
- * Callers should always check the return status of alloc_netdev(),
- * register_netdev() etc.  In the current implementation this code
- * will be optimised out by the compiler, so there is no penalty.
- */
-struct net_device static_single_netdev;
-
 /** Registered network-layer protocols */
 static struct net_protocol net_protocols[0] __table_start ( net_protocols );
 static struct net_protocol net_protocols_end[0] __table_end ( net_protocols );
 
-/** Network-layer addresses for @c static_single_netdev */
-static struct net_address static_single_netdev_addresses[0]
-	__table_start ( sgl_netdev_addresses );
-static struct net_address static_single_netdev_addresses_end[0]
-	__table_end ( sgl_netdev_addresses );
-
-/** Recevied packet queue */
-static LIST_HEAD ( rx_queue );
+/** List of network devices */
+static LIST_HEAD ( net_devices );
 
 #warning "Remove this static IP address hack"
 #include <ip.h>
 #include <gpxe/ip.h>
 
 /**
- * Register network device
+ * Transmit raw packet via network device
  *
  * @v netdev		Network device
+ * @v pkb		Packet buffer
  * @ret rc		Return status code
  *
- * Adds the network device to the list of network devices.
+ * Transmits the packet via the specified network device.  This
+ * function takes ownership of the packet buffer.
  */
-int register_netdev ( struct net_device *netdev ) {
-	
-#warning "Remove this static IP address hack"
-	{
-		const struct in_addr static_address = { htonl ( 0x0afefe01 ) };
-		const struct in_addr static_netmask = { htonl ( 0xffffff00 ) };
-		const struct in_addr static_gateway = { INADDR_NONE };
-		int rc;
-		
-		if ( ( rc = add_ipv4_address ( netdev, static_address,
-					       static_netmask,
-					       static_gateway ) ) != 0 )
-			return rc;
-	}
-
-	return 0;
+int netdev_tx ( struct net_device *netdev, struct pk_buff *pkb ) {
+	DBG ( "%s transmitting %p+%zx\n", netdev_name ( netdev ),
+	      pkb->data, pkb_len ( pkb ) );
+	return netdev->transmit ( netdev, pkb );
 }
 
 /**
- * Unregister network device
+ * Add packet to receive queue
  *
  * @v netdev		Network device
+ * @v pkb		Packet buffer
  *
- * Removes the network device from the list of network devices.
+ * The packet is added to the network device's RX queue.  This
+ * function takes ownership of the packet buffer.
  */
-void unregister_netdev ( struct net_device *netdev ) {
-
-#warning "Remove this static IP address hack"
-	del_ipv4_address ( netdev );
-
+void netdev_rx ( struct net_device *netdev, struct pk_buff *pkb ) {
+	DBG ( "%s received %p+%zx\n", netdev_name ( netdev ),
+	      pkb->data, pkb_len ( pkb ) );
+	list_add_tail ( &pkb->list, &netdev->rx_queue );
 }
 
 /**
- * Add packet to receive queue
+ * Transmit network-layer packet
  *
- * @v netdev		Network device
  * @v pkb		Packet buffer
+ * @v netdev		Network device
+ * @v net_protocol	Network-layer protocol
+ * @v ll_dest		Destination link-layer address
+ * @ret rc		Return status code
  *
- * The packet is added to the RX queue.  This function takes ownership
- * of the packet buffer.
+ * Prepends link-layer headers to the packet buffer and transmits the
+ * packet via the specified network device.  This function takes
+ * ownership of the packet buffer.
  */
-void netdev_rx ( struct net_device *netdev, struct pk_buff *pkb ) {
-	DBG ( "Packet received\n" );
-	pkb->ll_protocol = netdev->ll_protocol;
-	list_add_tail ( &pkb->list, &rx_queue );
+int net_tx ( struct pk_buff *pkb, struct net_device *netdev,
+	     struct net_protocol *net_protocol, const void *ll_dest ) {
+	return netdev->ll_protocol->tx ( pkb, netdev, net_protocol, ll_dest );
 }
 
 /**
- * Identify network protocol
+ * Process received network-layer packet
  *
+ * @v pkb		Packet buffer
+ * @v netdev		Network device
  * @v net_proto		Network-layer protocol, in network-byte order
- * @ret net_protocol	Network-layer protocol, or NULL
- *
- * Identify a network-layer protocol from a protocol number, which
- * must be an ETH_P_XXX constant in network-byte order.
+ * @v ll_source		Source link-layer address
  */
-struct net_protocol * find_net_protocol ( uint16_t net_proto ) {
+void net_rx ( struct pk_buff *pkb, struct net_device *netdev,
+	      uint16_t net_proto, const void *ll_source ) {
 	struct net_protocol *net_protocol;
 
+	/* Hand off to network-layer protocol, if any */
 	for ( net_protocol = net_protocols ; net_protocol < net_protocols_end ;
 	      net_protocol++ ) {
-		if ( net_protocol->net_proto == net_proto )
-			return net_protocol;
-	}
-	return NULL;
-}
-
-/**
- * Identify network device by network-layer address
- *
- * @v net_protocol	Network-layer protocol
- * @v net_addr		Network-layer address
- * @ret netdev		Network device, or NULL
- *
- * Searches through all network devices to find the device with the
- * specified network-layer address.
- *
- * Note that even with a static single network device, this function
- * can still return NULL.
- */
-struct net_device *
-find_netdev_by_net_addr ( struct net_protocol *net_protocol,
-			  void *net_addr ) {
-	struct net_address *net_address;
-	struct net_device *netdev = &static_single_netdev;
-	
-	for ( net_address = static_single_netdev_addresses ;
-	      net_address < static_single_netdev_addresses_end ;
-	      net_address ++ ) {
-		if ( ( net_address->net_protocol == net_protocol ) &&
-		     ( memcmp ( net_address->net_addr, net_addr,
-				net_protocol->net_addr_len ) == 0 ) )
-			return netdev;
+		if ( net_protocol->net_proto == net_proto ) {
+			net_protocol->rx ( pkb, netdev, ll_source );
+			break;
+		}
 	}
-
-	return NULL;
 }
 
 /**
- * Poll for packet on all network devices
+ * Poll for packet on network device
  *
+ * @v netdev		Network device
  * @ret True		There are packets present in the receive queue
  * @ret False		There are no packets present in the receive queue
  *
- * Polls all network devices for received packets.  Any received
+ * Polls the network device for received packets.  Any received
  * packets will be added to the RX packet queue via netdev_rx().
  */
-int net_poll ( void ) {
-	struct net_device *netdev = &static_single_netdev;
-
-	DBG ( "Polling network\n" );
+int netdev_poll ( struct net_device *netdev ) {
 	netdev->poll ( netdev );
-
-	return ( ! list_empty ( &rx_queue ) );
+	return ( ! list_empty ( &netdev->rx_queue ) );
 }
 
 /**
- * Remove packet from receive queue
+ * Remove packet from device's receive queue
  *
+ * @v netdev		Network device
  * @ret pkb		Packet buffer, or NULL
  *
- * Removes the first packet from the RX queue and returns it.
+ * Removes the first packet from the device's RX queue and returns it.
  * Ownership of the packet is transferred to the caller.
  */
-struct pk_buff * net_rx_dequeue ( void ) {
+struct pk_buff * netdev_rx_dequeue ( struct net_device *netdev ) {
 	struct pk_buff *pkb;
 
-	list_for_each_entry ( pkb, &rx_queue, list ) {
+	list_for_each_entry ( pkb, &netdev->rx_queue, list ) {
 		list_del ( &pkb->list );
 		return pkb;
 	}
 }
 
 /**
- * Process received packet
+ * Allocate network device
  *
- * @v pkb		Packet buffer
- * @ret rc		Return status code
+ * @v priv_size		Size of private data area (net_device::priv)
+ * @ret netdev		Network device, or NULL
  *
- * Processes a packet received from the network (and, usually, removed
- * from the RX queue by net_rx_dequeue()).  This call takes ownership
- * of the packet buffer.
+ * Allocates space for a network device and its private data area.
  */
-int net_rx_process ( struct pk_buff *pkb ) {
-	struct ll_protocol *ll_protocol;
-	struct ll_header llhdr;
-	struct net_protocol *net_protocol;
-	int rc;
+struct net_device * alloc_netdev ( size_t priv_size ) {
+	struct net_device *netdev;
 
-	/* Parse link-layer header */
-	ll_protocol = pkb->ll_protocol;
-	ll_protocol->parse_llh ( pkb, &llhdr );
-	
-	/* Identify network-layer protocol */
-	net_protocol = find_net_protocol ( llhdr.net_proto );
-	if ( ! net_protocol ) {
-		DBG ( "Unknown network-layer protocol %x\n",
-		      ntohs ( llhdr.net_proto ) );
-		free_pkb ( pkb );
-		return -EPROTONOSUPPORT;
+	netdev = calloc ( 1, sizeof ( *netdev ) + priv_size );
+	if ( netdev ) {
+		INIT_LIST_HEAD ( &netdev->rx_queue );
+		netdev->priv = ( ( ( void * ) netdev ) + sizeof ( *netdev ) );
 	}
-	pkb->net_protocol = net_protocol;
-	
-	/* Strip off link-layer header */
-#warning "Temporary hack"
-	pkb_pull ( pkb, ETH_HLEN );
+	return netdev;
+}
+
+/**
+ * Register network device
+ *
+ * @v netdev		Network device
+ * @ret rc		Return status code
+ *
+ * Adds the network device to the list of network devices.
+ */
+int register_netdev ( struct net_device *netdev ) {
 	
-	/* Hand off to network layer */
-	if ( ( rc = net_protocol->rx_process ( pkb ) ) != 0 ) {
-		DBG ( "Network-layer protocol dropped packet\n" );
-		return rc;
+#warning "Remove this static IP address hack"
+	{
+		const struct in_addr static_address = { htonl ( 0x0afefe01 ) };
+		const struct in_addr static_netmask = { htonl ( 0xffffff00 ) };
+		const struct in_addr static_gateway = { INADDR_NONE };
+		int rc;
+		
+		if ( ( rc = add_ipv4_address ( netdev, static_address,
+					       static_netmask,
+					       static_gateway ) ) != 0 )
+			return rc;
 	}
 
+	/* Add to device list */
+	list_add_tail ( &netdev->list, &net_devices );
+	DBG ( "%s registered\n", netdev_name ( netdev ) );
+
 	return 0;
 }
 
+/**
+ * Unregister network device
+ *
+ * @v netdev		Network device
+ *
+ * Removes the network device from the list of network devices.
+ */
+void unregister_netdev ( struct net_device *netdev ) {
+	struct pk_buff *pkb;
+
+#warning "Remove this static IP address hack"
+	del_ipv4_address ( netdev );
+
+	/* Discard any packets in the RX queue */
+	while ( ( pkb = netdev_rx_dequeue ( netdev ) ) ) {
+		DBG ( "%s discarding %p+%zx\n", netdev_name ( netdev ),
+		      pkb->data, pkb_len ( pkb ) );
+		free_pkb ( pkb );
+	}
+
+	/* Remove from device list */
+	list_del ( &netdev->list );
+	DBG ( "%s unregistered\n", netdev_name ( netdev ) );
+}
+
+/**
+ * Free network device
+ *
+ * @v netdev		Network device
+ */
+void free_netdev ( struct net_device *netdev ) {
+	free ( netdev );
+}
+
+/**
+ * Iterate through network devices
+ *
+ * @ret netdev		Network device, or NULL
+ *
+ * This returns the registered network devices in the order of
+ * registration.  If no network devices are registered, it will return
+ * NULL.
+ */
+struct net_device * next_netdev ( void ) {
+	struct net_device *netdev;
+
+	list_for_each_entry ( netdev, &net_devices, list ) {
+		list_del ( &netdev->list );
+		list_add_tail ( &netdev->list, &net_devices );
+		return netdev;
+	}
+	return NULL;
+}
+
 /**
  * Single-step the network stack
  *
  * multiple packets are processed per poll.
  */
 static void net_step ( struct process *process ) {
+	struct net_device *netdev;
 	struct pk_buff *pkb;
 
-	/* Poll for new packets */
-	net_poll();
+	/* Poll and process each network device */
+	list_for_each_entry ( netdev, &net_devices, list ) {
+
+		/* Poll for new packets */
+		netdev_poll ( netdev );
 
-	/* Handle at most one received packet */
-	if ( ( pkb = net_rx_dequeue () ) ) {
-		net_rx_process ( pkb );
-		DBG ( "Processed received packet\n" );
+		/* Handle at most one received packet per poll */
+		if ( ( pkb = netdev_rx_dequeue ( netdev ) ) ) {
+			DBG ( "%s processing %p+%zx\n", netdev_name ( netdev ),
+			      pkb->data, pkb_len ( pkb ) );
+			netdev->ll_protocol->rx ( pkb, netdev );
+		}
 	}
 
 	/* Re-schedule ourself */

src/net/tcp.c

 			pkb_put ( pkb, uip_len );
 			memcpy ( pkb->data, uip_buf, uip_len );
 
-			ipv4_uip_transmit ( pkb );
+			ipv4_uip_tx ( pkb );
 		}
 	}
 }