[xen] Add support for Xen netfront virtual NICs

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

1 files changed, 852 insertions, 0 deletions

diff --git a/src/drivers/net/netfront.c b/src/drivers/net/netfront.c
new file mode 100644
index 00000000..18913c08
--- /dev/null
+++ b/src/drivers/net/netfront.c
@@ -0,0 +1,852 @@
+/*
+ * Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <ipxe/netdevice.h>
+#include <ipxe/ethernet.h>
+#include <ipxe/if_ether.h>
+#include <ipxe/malloc.h>
+#include <ipxe/base16.h>
+#include <ipxe/xen.h>
+#include <ipxe/xenstore.h>
+#include <ipxe/xenbus.h>
+#include <ipxe/xengrant.h>
+#include <ipxe/xenevent.h>
+#include "netfront.h"
+
+/** @file
+ *
+ * Xen netfront driver
+ *
+ */
+
+/* Disambiguate the various error causes */
+#define EIO_NETIF_RSP_ERROR						\
+	__einfo_error ( EINFO_EIO_NETIF_RSP_ERROR )
+#define EINFO_EIO_NETIF_RSP_ERROR					\
+	__einfo_uniqify ( EINFO_EIO, -NETIF_RSP_ERROR,			\
+			  "Unspecified network error" )
+#define EIO_NETIF_RSP_DROPPED						\
+	__einfo_error ( EINFO_EIO_NETIF_RSP_DROPPED )
+#define EINFO_EIO_NETIF_RSP_DROPPED					\
+	__einfo_uniqify ( EINFO_EIO, -NETIF_RSP_DROPPED,		\
+			  "Packet dropped" )
+#define EIO_NETIF_RSP( status )						\
+	EUNIQ ( EINFO_EIO, -(status),					\
+		EIO_NETIF_RSP_ERROR, EIO_NETIF_RSP_DROPPED )
+
+/******************************************************************************
+ *
+ * XenStore interface
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Fetch MAC address
+ *
+ * @v netfront		Netfront device
+ * @v hw_addr		Hardware address to fill in
+ * @ret rc		Return status code
+ */
+static int netfront_read_mac ( struct netfront_nic *netfront, void *hw_addr ) {
+	struct xen_device *xendev = netfront->xendev;
+	struct xen_hypervisor *xen = xendev->xen;
+	char *mac;
+	int len;
+	int rc;
+
+	/* Fetch MAC address */
+	if ( ( rc = xenstore_read ( xen, &mac, xendev->key, "mac", NULL ) )!=0){
+		DBGC ( netfront, "NETFRONT %s could not read MAC address: %s\n",
+		       xendev->key, strerror ( rc ) );
+		goto err_xenstore_read;
+	}
+	DBGC2 ( netfront, "NETFRONT %s has MAC address \"%s\"\n",
+		xendev->key, mac );
+
+	/* Decode MAC address */
+	len = hex_decode ( mac, ':', hw_addr, ETH_ALEN );
+	if ( len < 0 ) {
+		rc = len;
+		DBGC ( netfront, "NETFRONT %s could not decode MAC address "
+		       "\"%s\": %s\n", xendev->key, mac, strerror ( rc ) );
+		goto err_decode;
+	}
+
+	/* Success */
+	rc = 0;
+
+ err_decode:
+	free ( mac );
+ err_xenstore_read:
+	return rc;
+}
+
+/**
+ * Write XenStore numeric value
+ *
+ * @v netfront		Netfront device
+ * @v subkey		Subkey
+ * @v num		Numeric value
+ * @ret rc		Return status code
+ */
+static int netfront_write_num ( struct netfront_nic *netfront,
+				const char *subkey, unsigned long num ) {
+	struct xen_device *xendev = netfront->xendev;
+	struct xen_hypervisor *xen = xendev->xen;
+	int rc;
+
+	/* Write value */
+	if ( ( rc = xenstore_write_num ( xen, num, xendev->key, subkey,
+					 NULL ) ) != 0 ) {
+		DBGC ( netfront, "NETFRONT %s could not set %s=\"%ld\": %s\n",
+		       xendev->key, subkey, num, strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Write XenStore flag value
+ *
+ * @v netfront		Netfront device
+ * @v subkey		Subkey
+ * @v num		Numeric value
+ * @ret rc		Return status code
+ */
+static int netfront_write_flag ( struct netfront_nic *netfront,
+				 const char *subkey ) {
+
+	return netfront_write_num ( netfront, subkey, 1 );
+}
+
+/**
+ * Delete XenStore value
+ *
+ * @v netfront		Netfront device
+ * @v subkey		Subkey
+ * @ret rc		Return status code
+ */
+static int netfront_rm ( struct netfront_nic *netfront, const char *subkey ) {
+	struct xen_device *xendev = netfront->xendev;
+	struct xen_hypervisor *xen = xendev->xen;
+	int rc;
+
+	/* Remove value */
+	if ( ( rc = xenstore_rm ( xen, xendev->key, subkey, NULL ) ) != 0 ) {
+		DBGC ( netfront, "NETFRONT %s could not delete %s: %s\n",
+		       xendev->key, subkey, strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/******************************************************************************
+ *
+ * Events
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Create event channel
+ *
+ * @v netfront		Netfront device
+ * @ret rc		Return status code
+ */
+static int netfront_create_event ( struct netfront_nic *netfront ) {
+	struct xen_device *xendev = netfront->xendev;
+	struct xen_hypervisor *xen = xendev->xen;
+	struct evtchn_alloc_unbound alloc_unbound;
+	struct evtchn_close close;
+	int xenrc;
+	int rc;
+
+	/* Allocate event */
+	alloc_unbound.dom = DOMID_SELF;
+	alloc_unbound.remote_dom = xendev->backend_id;
+	if ( ( xenrc = xenevent_alloc_unbound ( xen, &alloc_unbound ) ) != 0 ) {
+		rc = -EXEN ( xenrc );
+		DBGC ( netfront, "NETFRONT %s could not allocate event: %s\n",
+		       xendev->key, strerror ( rc ) );
+		goto err_alloc_unbound;
+	}
+	netfront->event.port = alloc_unbound.port;
+
+	/* Publish event channel */
+	if ( ( rc = netfront_write_num ( netfront, "event-channel",
+					 netfront->event.port ) ) != 0 )
+		goto err_write_num;
+
+	DBGC ( netfront, "NETFRONT %s event-channel=\"%d\"\n",
+	       xendev->key, netfront->event.port );
+	return 0;
+
+	netfront_rm ( netfront, "event-channel" );
+ err_write_num:
+	close.port = netfront->event.port;
+	xenevent_close ( xen, &close );
+ err_alloc_unbound:
+	return rc;
+}
+
+/**
+ * Send event
+ *
+ * @v netfront		Netfront device
+ * @ret rc		Return status code
+ */
+static inline __attribute__ (( always_inline )) int
+netfront_send_event ( struct netfront_nic *netfront ) {
+	struct xen_device *xendev = netfront->xendev;
+	struct xen_hypervisor *xen = xendev->xen;
+	int xenrc;
+	int rc;
+
+	/* Send event */
+	if ( ( xenrc = xenevent_send ( xen, &netfront->event ) ) != 0 ) {
+		rc = -EXEN ( xenrc );
+		DBGC ( netfront, "NETFRONT %s could not send event: %s\n",
+		       xendev->key, strerror ( rc ) );
+		return rc;
+	}
+
+	return 0;
+}
+
+/**
+ * Destroy event channel
+ *
+ * @v netfront		Netfront device
+ */
+static void netfront_destroy_event ( struct netfront_nic *netfront ) {
+	struct xen_device *xendev = netfront->xendev;
+	struct xen_hypervisor *xen = xendev->xen;
+	struct evtchn_close close;
+
+	/* Unpublish event channel */
+	netfront_rm ( netfront, "event-channel" );
+
+	/* Close event channel */
+	close.port = netfront->event.port;
+	xenevent_close ( xen, &close );
+}
+
+/******************************************************************************
+ *
+ * Descriptor rings
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Create descriptor ring
+ *
+ * @v netfront		Netfront device
+ * @v ring		Descriptor ring
+ * @ret rc		Return status code
+ */
+static int netfront_create_ring ( struct netfront_nic *netfront,
+				  struct netfront_ring *ring ) {
+	struct xen_device *xendev = netfront->xendev;
+	struct xen_hypervisor *xen = xendev->xen;
+	unsigned int i;
+	int rc;
+
+	/* Initialise buffer ID ring */
+	for ( i = 0 ; i < ring->count ; i++ ) {
+		ring->ids[i] = i;
+		assert ( ring->iobufs[i] == NULL );
+	}
+	ring->id_prod = 0;
+	ring->id_cons = 0;
+
+	/* Allocate and initialise shared ring */
+	ring->sring.raw = malloc_dma ( PAGE_SIZE, PAGE_SIZE );
+	if ( ! ring->sring.raw ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+
+	/* Grant access to shared ring */
+	xengrant_permit_access ( xen, ring->ref, xendev->backend_id, 0,
+				 ring->sring.raw );
+
+	/* Publish shared ring reference */
+	if ( ( rc = netfront_write_num ( netfront, ring->ref_key,
+					 ring->ref ) ) != 0 )
+		goto err_write_num;
+
+	DBGC ( netfront, "NETFRONT %s %s=\"%d\" [%08lx,%08lx)\n",
+	       xendev->key, ring->ref_key, ring->ref,
+	       virt_to_phys ( ring->sring.raw ),
+	       ( virt_to_phys ( ring->sring.raw ) + PAGE_SIZE ) );
+	return 0;
+
+	netfront_rm ( netfront, ring->ref_key );
+ err_write_num:
+	xengrant_invalidate ( xen, ring->ref );
+	free_dma ( ring->sring.raw, PAGE_SIZE );
+ err_alloc:
+	return rc;
+}
+
+/**
+ * Add buffer to descriptor ring
+ *
+ * @v netfront		Netfront device
+ * @v ring		Descriptor ring
+ * @v iobuf		I/O buffer
+ * @v ref		Grant reference to fill in
+ * @ret id		Buffer ID
+ *
+ * The caller is responsible for ensuring that there is space in the
+ * ring.
+ */
+static unsigned int netfront_push ( struct netfront_nic *netfront,
+				    struct netfront_ring *ring,
+				    struct io_buffer *iobuf,
+				    grant_ref_t *ref ) {
+	struct xen_device *xendev = netfront->xendev;
+	struct xen_hypervisor *xen = xendev->xen;
+	unsigned int id;
+
+	/* Sanity check */
+	assert ( ! netfront_ring_is_full ( ring ) );
+
+	/* Allocate buffer ID */
+	id = ring->ids[ ( ring->id_prod++ ) & ( ring->count - 1 ) ];
+
+	/* Store I/O buffer */
+	assert ( ring->iobufs[id] == NULL );
+	ring->iobufs[id] = iobuf;
+
+	/* Grant access to I/O buffer page.  I/O buffers are naturally
+	 * aligned, so we never need to worry about crossing a page
+	 * boundary.
+	 */
+	*ref = ring->refs[id];
+	xengrant_permit_access ( xen, ring->refs[id], xendev->backend_id, 0,
+				 iobuf->data );
+
+	return id;
+}
+
+/**
+ * Remove buffer from descriptor ring
+ *
+ * @v netfront		Netfront device
+ * @v ring		Descriptor ring
+ * @v id		Buffer ID
+ * @ret iobuf		I/O buffer
+ */
+static struct io_buffer * netfront_pull ( struct netfront_nic *netfront,
+					  struct netfront_ring *ring,
+					  unsigned int id ) {
+	struct xen_device *xendev = netfront->xendev;
+	struct xen_hypervisor *xen = xendev->xen;
+	struct io_buffer *iobuf;
+
+	/* Sanity check */
+	assert ( id < ring->count );
+
+	/* Revoke access from I/O buffer page */
+	xengrant_invalidate ( xen, ring->refs[id] );
+
+	/* Retrieve I/O buffer */
+	iobuf = ring->iobufs[id];
+	assert ( iobuf != NULL );
+	ring->iobufs[id] = NULL;
+
+	/* Free buffer ID */
+	ring->ids[ ( ring->id_cons++ ) & ( ring->count - 1 ) ] = id;
+
+	return iobuf;
+}
+
+/**
+ * Destroy descriptor ring
+ *
+ * @v netfront		Netfront device
+ * @v ring		Descriptor ring
+ * @v discard		Method used to discard outstanding buffer, or NULL
+ */
+static void netfront_destroy_ring ( struct netfront_nic *netfront,
+				    struct netfront_ring *ring,
+				    void ( * discard ) ( struct io_buffer * ) ){
+	struct xen_device *xendev = netfront->xendev;
+	struct xen_hypervisor *xen = xendev->xen;
+	struct io_buffer *iobuf;
+	unsigned int id;
+
+	/* Flush any outstanding buffers */
+	while ( ! netfront_ring_is_empty ( ring ) ) {
+		id = ring->ids[ ring->id_cons & ( ring->count - 1 ) ];
+		iobuf = netfront_pull ( netfront, ring, id );
+		if ( discard )
+			discard ( iobuf );
+	}
+
+	/* Unpublish shared ring reference */
+	netfront_rm ( netfront, ring->ref_key );
+
+	/* Revoke access from shared ring */
+	xengrant_invalidate ( xen, ring->ref );
+
+	/* Free page */
+	free_dma ( ring->sring.raw, PAGE_SIZE );
+	ring->sring.raw = NULL;
+}
+
+/******************************************************************************
+ *
+ * Network device interface
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Refill receive descriptor ring
+ *
+ * @v netfront		Netfront device
+ */
+static void netfront_refill_rx ( struct netfront_nic *netfront ) {
+	struct xen_device *xendev = netfront->xendev;
+	struct io_buffer *iobuf;
+	struct netif_rx_request *request;
+	int notify;
+
+	/* Do nothing if ring is already full */
+	if ( netfront_ring_is_full ( &netfront->rx ) )
+		return;
+
+	/* Refill ring */
+	do {
+
+		/* Allocate I/O buffer */
+		iobuf = alloc_iob ( PAGE_SIZE );
+		if ( ! iobuf ) {
+			/* Wait for next refill */
+			break;
+		}
+
+		/* Add to descriptor ring */
+		request = RING_GET_REQUEST ( &netfront->rx_fring,
+					     netfront->rx_fring.req_prod_pvt++);
+		request->id = netfront_push ( netfront, &netfront->rx, iobuf,
+					      &request->gref );
+		DBGC2 ( netfront, "NETFRONT %s RX id %d ref %d is %#08lx+%zx\n",
+			xendev->key, request->id, request->gref,
+			virt_to_phys ( iobuf->data ), iob_tailroom ( iobuf ) );
+
+	} while ( ! netfront_ring_is_full ( &netfront->rx ) );
+
+	/* Push new descriptors and notify backend if applicable */
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY ( &netfront->rx_fring, notify );
+	if ( notify )
+		netfront_send_event ( netfront );
+}
+
+/**
+ * Open network device
+ *
+ * @v netdev		Network device
+ * @ret rc		Return status code
+ */
+static int netfront_open ( struct net_device *netdev ) {
+	struct netfront_nic *netfront = netdev->priv;
+	struct xen_device *xendev = netfront->xendev;
+	int rc;
+
+	/* Create transmit descriptor ring */
+	if ( ( rc = netfront_create_ring ( netfront, &netfront->tx ) ) != 0 )
+		goto err_create_tx;
+	SHARED_RING_INIT ( netfront->tx_sring );
+	FRONT_RING_INIT ( &netfront->tx_fring, netfront->tx_sring, PAGE_SIZE );
+	assert ( RING_SIZE ( &netfront->tx_fring ) >= netfront->tx.count );
+
+	/* Create receive descriptor ring */
+	if ( ( rc = netfront_create_ring ( netfront, &netfront->rx ) ) != 0 )
+		goto err_create_rx;
+	SHARED_RING_INIT ( netfront->rx_sring );
+	FRONT_RING_INIT ( &netfront->rx_fring, netfront->rx_sring, PAGE_SIZE );
+	assert ( RING_SIZE ( &netfront->rx_fring ) >= netfront->rx.count );
+
+	/* Create event channel */
+	if ( ( rc = netfront_create_event ( netfront ) ) != 0 )
+		goto err_create_event;
+
+	/* "Request" the rx-copy feature.  Current versions of
+	 * xen_netback.ko will fail silently if this parameter is not
+	 * present.
+	 */
+	if ( ( rc = netfront_write_flag ( netfront, "request-rx-copy" ) ) != 0 )
+		goto err_request_rx_copy;
+
+	/* Disable checksum offload, since we will always do the work anyway */
+	if ( ( rc = netfront_write_flag ( netfront,
+					  "feature-no-csum-offload" ) ) != 0 )
+		goto err_feature_no_csum_offload;
+
+	/* Set state to Connected */
+	if ( ( rc = xenbus_set_state ( xendev, XenbusStateConnected ) ) != 0 ) {
+		DBGC ( netfront, "NETFRONT %s could not set state=\"%d\": %s\n",
+		       xendev->key, XenbusStateConnected, strerror ( rc ) );
+		goto err_set_state;
+	}
+
+	/* Wait for backend to connect */
+	if ( ( rc = xenbus_backend_wait ( xendev, XenbusStateConnected ) ) !=0){
+		DBGC ( netfront, "NETFRONT %s could not connect to backend: "
+		       "%s\n", xendev->key, strerror ( rc ) );
+		goto err_backend_wait;
+	}
+
+	/* Refill receive descriptor ring */
+	netfront_refill_rx ( netfront );
+
+	/* Set link up */
+	netdev_link_up ( netdev );
+
+	return 0;
+
+ err_backend_wait:
+	xenbus_set_state ( xendev, XenbusStateInitialising );
+ err_set_state:
+	netfront_rm ( netfront, "feature-no-csum-offload" );
+ err_feature_no_csum_offload:
+	netfront_rm ( netfront, "request-rx-copy" );
+ err_request_rx_copy:
+	netfront_destroy_event ( netfront );
+ err_create_event:
+	netfront_destroy_ring ( netfront, &netfront->rx, NULL );
+ err_create_rx:
+	netfront_destroy_ring ( netfront, &netfront->tx, NULL );
+ err_create_tx:
+	return rc;
+}
+
+/**
+ * Close network device
+ *
+ * @v netdev		Network device
+ */
+static void netfront_close ( struct net_device *netdev ) {
+	struct netfront_nic *netfront = netdev->priv;
+	struct xen_device *xendev = netfront->xendev;
+	int rc;
+
+	/* Set state to Closed */
+	xenbus_set_state ( xendev, XenbusStateClosed );
+
+	/* Wait for backend to close, thereby ensuring that grant
+	 * references are no longer in use, etc.
+	 */
+	if ( ( rc = xenbus_backend_wait ( xendev, XenbusStateClosed ) ) != 0 ) {
+		DBGC ( netfront, "NETFRONT %s could not disconnect from "
+		       "backend: %s\n", xendev->key, strerror ( rc ) );
+		/* Things will probably go _very_ badly wrong if this
+		 * happens, since it means the backend may still write
+		 * to the outstanding RX buffers that we are about to
+		 * free.  The best we can do is report the error via
+		 * the link status, but there's a good chance the
+		 * machine will crash soon.
+		 */
+		netdev_link_err ( netdev, rc );
+	} else {
+		netdev_link_down ( netdev );
+	}
+
+	/* Reset state to Initialising */
+	xenbus_set_state ( xendev, XenbusStateInitialising );
+
+	/* Delete flags */
+	netfront_rm ( netfront, "feature-no-csum-offload" );
+	netfront_rm ( netfront, "request-rx-copy" );
+
+	/* Destroy event channel */
+	netfront_destroy_event ( netfront );
+
+	/* Destroy receive descriptor ring, freeing any outstanding
+	 * I/O buffers.
+	 */
+	netfront_destroy_ring ( netfront, &netfront->rx, free_iob );
+
+	/* Destroy transmit descriptor ring.  Leave any outstanding
+	 * I/O buffers to be freed by netdev_tx_flush().
+	 */
+	netfront_destroy_ring ( netfront, &netfront->tx, NULL );
+}
+
+/**
+ * Transmit packet
+ *
+ * @v netdev		Network device
+ * @v iobuf		I/O buffer
+ * @ret rc		Return status code
+ */
+static int netfront_transmit ( struct net_device *netdev,
+			       struct io_buffer *iobuf ) {
+	struct netfront_nic *netfront = netdev->priv;
+	struct xen_device *xendev = netfront->xendev;
+	struct netif_tx_request *request;
+	int notify;
+
+	/* Check that we have space in the ring */
+	if ( netfront_ring_is_full ( &netfront->tx ) ) {
+		DBGC ( netfront, "NETFRONT %s out of transmit descriptors\n",
+		       xendev->key );
+		return -ENOBUFS;
+	}
+
+	/* Add to descriptor ring */
+	request = RING_GET_REQUEST ( &netfront->tx_fring,
+				     netfront->tx_fring.req_prod_pvt++ );
+	request->id = netfront_push ( netfront, &netfront->tx, iobuf,
+				      &request->gref );
+	request->offset = ( virt_to_phys ( iobuf->data ) & ( PAGE_SIZE - 1 ) );
+	request->flags = NETTXF_data_validated;
+	request->size = iob_len ( iobuf );
+	DBGC2 ( netfront, "NETFRONT %s TX id %d ref %d is %#08lx+%zx\n",
+		xendev->key, request->id, request->gref,
+		virt_to_phys ( iobuf->data ), iob_len ( iobuf ) );
+
+	/* Push new descriptor and notify backend if applicable */
+	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY ( &netfront->tx_fring, notify );
+	if ( notify )
+		netfront_send_event ( netfront );
+
+	return 0;
+}
+
+/**
+ * Poll for completed packets
+ *
+ * @v netdev		Network device
+ */
+static void netfront_poll_tx ( struct net_device *netdev ) {
+	struct netfront_nic *netfront = netdev->priv;
+	struct xen_device *xendev = netfront->xendev;
+	struct netif_tx_response *response;
+	struct io_buffer *iobuf;
+	unsigned int status;
+	int rc;
+
+	/* Consume any unconsumed responses */
+	while ( RING_HAS_UNCONSUMED_RESPONSES ( &netfront->tx_fring ) ) {
+
+		/* Get next response */
+		response = RING_GET_RESPONSE ( &netfront->tx_fring,
+					       netfront->tx_fring.rsp_cons++ );
+
+		/* Retrieve from descriptor ring */
+		iobuf = netfront_pull ( netfront, &netfront->tx, response->id );
+		status = response->status;
+		if ( status == NETIF_RSP_OKAY ) {
+			DBGC2 ( netfront, "NETFRONT %s TX id %d complete\n",
+				xendev->key, response->id );
+			netdev_tx_complete ( netdev, iobuf );
+		} else {
+			rc = -EIO_NETIF_RSP ( status );
+			DBGC2 ( netfront, "NETFRONT %s TX id %d error %d: %s\n",
+				xendev->key, response->id, status,
+				strerror ( rc ) );
+			netdev_tx_complete_err ( netdev, iobuf, rc );
+		}
+	}
+}
+
+/**
+ * Poll for received packets
+ *
+ * @v netdev		Network device
+ */
+static void netfront_poll_rx ( struct net_device *netdev ) {
+	struct netfront_nic *netfront = netdev->priv;
+	struct xen_device *xendev = netfront->xendev;
+	struct netif_rx_response *response;
+	struct io_buffer *iobuf;
+	int status;
+	size_t len;
+	int rc;
+
+	/* Consume any unconsumed responses */
+	while ( RING_HAS_UNCONSUMED_RESPONSES ( &netfront->rx_fring ) ) {
+
+		/* Get next response */
+		response = RING_GET_RESPONSE ( &netfront->rx_fring,
+					       netfront->rx_fring.rsp_cons++ );
+
+		/* Retrieve from descriptor ring */
+		iobuf = netfront_pull ( netfront, &netfront->rx, response->id );
+		status = response->status;
+		if ( status >= 0 ) {
+			len = status;
+			iob_reserve ( iobuf, response->offset );
+			iob_put ( iobuf, len );
+			DBGC2 ( netfront, "NETFRONT %s RX id %d complete "
+				"%#08lx+%zx\n", xendev->key, response->id,
+				virt_to_phys ( iobuf->data ), len );
+			netdev_rx ( netdev, iobuf );
+		} else {
+			rc = -EIO_NETIF_RSP ( status );
+			DBGC2 ( netfront, "NETFRONT %s RX id %d error %d: %s\n",
+				xendev->key, response->id, status,
+				strerror ( rc ) );
+			netdev_rx_err ( netdev, iobuf, rc );
+		}
+	}
+}
+
+/**
+ * Poll for completed and received packets
+ *
+ * @v netdev		Network device
+ */
+static void netfront_poll ( struct net_device *netdev ) {
+	struct netfront_nic *netfront = netdev->priv;
+
+	/* Poll for TX completions */
+	netfront_poll_tx ( netdev );
+
+	/* Poll for RX completions */
+	netfront_poll_rx ( netdev );
+
+	/* Refill RX descriptor ring */
+	netfront_refill_rx ( netfront );
+}
+
+/** Network device operations */
+static struct net_device_operations netfront_operations = {
+	.open		= netfront_open,
+	.close		= netfront_close,
+	.transmit	= netfront_transmit,
+	.poll		= netfront_poll,
+};
+
+/******************************************************************************
+ *
+ * Xen device bus interface
+ *
+ ******************************************************************************
+ */
+
+/**
+ * Probe Xen device
+ *
+ * @v xendev		Xen device
+ * @ret rc		Return status code
+ */
+static int netfront_probe ( struct xen_device *xendev ) {
+	struct xen_hypervisor *xen = xendev->xen;
+	struct net_device *netdev;
+	struct netfront_nic *netfront;
+	int rc;
+
+	/* Allocate and initialise structure */
+	netdev = alloc_etherdev ( sizeof ( *netfront ) );
+	if ( ! netdev ) {
+		rc = -ENOMEM;
+		goto err_alloc;
+	}
+	netdev_init ( netdev, &netfront_operations );
+	netdev->dev = &xendev->dev;
+	netfront = netdev->priv;
+	netfront->xendev = xendev;
+	DBGC ( netfront, "NETFRONT %s backend=\"%s\" in domain %ld\n",
+	       xendev->key, xendev->backend, xendev->backend_id );
+
+	/* Allocate grant references and initialise descriptor rings */
+	if ( ( rc = xengrant_alloc ( xen, netfront->refs,
+				     NETFRONT_REF_COUNT ) ) != 0 ) {
+		DBGC ( netfront, "NETFRONT %s could not allocate grant "
+		       "references: %s\n", xendev->key, strerror ( rc ) );
+		goto err_grant_alloc;
+	}
+	netfront_init_ring ( &netfront->tx, "tx-ring-ref",
+			     netfront->refs[NETFRONT_REF_TX_RING],
+			     NETFRONT_NUM_TX_DESC, netfront->tx_iobufs,
+			     &netfront->refs[NETFRONT_REF_TX_BASE],
+			     netfront->tx_ids );
+	netfront_init_ring ( &netfront->rx, "rx-ring-ref",
+			     netfront->refs[NETFRONT_REF_RX_RING],
+			     NETFRONT_NUM_RX_DESC, netfront->rx_iobufs,
+			     &netfront->refs[NETFRONT_REF_RX_BASE],
+			     netfront->rx_ids );
+
+	/* Fetch MAC address */
+	if ( ( rc = netfront_read_mac ( netfront, netdev->hw_addr ) ) != 0 )
+		goto err_read_mac;
+
+	/* Register network device */
+	if ( ( rc = register_netdev ( netdev ) ) != 0 )
+		goto err_register_netdev;
+
+	/* Set initial link state */
+	netdev_link_down ( netdev );
+
+	xen_set_drvdata ( xendev, netdev );
+	return 0;
+
+	unregister_netdev ( netdev );
+ err_register_netdev:
+ err_read_mac:
+	xengrant_free ( xen, netfront->refs, NETFRONT_REF_COUNT );
+ err_grant_alloc:
+	netdev_nullify ( netdev );
+	netdev_put ( netdev );
+ err_alloc:
+	return rc;
+}
+
+/**
+ * Remove Xen device
+ *
+ * @v xendev		Xen device
+ */
+static void netfront_remove ( struct xen_device *xendev ) {
+	struct net_device *netdev = xen_get_drvdata ( xendev );
+	struct netfront_nic *netfront = netdev->priv;
+	struct xen_hypervisor *xen = xendev->xen;
+
+	/* Unregister network device */
+	unregister_netdev ( netdev );
+
+	/* Free resources */
+	xengrant_free ( xen, netfront->refs, NETFRONT_REF_COUNT );
+
+	/* Free network device */
+	netdev_nullify ( netdev );
+	netdev_put ( netdev );
+}
+
+/** Xen netfront driver */
+struct xen_driver netfront_driver __xen_driver = {
+	.name = "netfront",
+	.type = "vif",
+	.probe = netfront_probe,
+	.remove = netfront_remove,
+};