efi_snp.c

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/*
 * Copyright (C) 2008 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 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 );
FILE_SECBOOT ( PERMITTED );

#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <byteswap.h>
#include <ipxe/netdevice.h>
#include <ipxe/vlan.h>
#include <ipxe/iobuf.h>
#include <ipxe/in.h>
#include <ipxe/version.h>
#include <ipxe/console.h>
#include <ipxe/efi/efi.h>
#include <ipxe/efi/efi_driver.h>
#include <ipxe/efi/efi_strings.h>
#include <ipxe/efi/efi_path.h>
#include <ipxe/efi/efi_utils.h>
#include <ipxe/efi/efi_watchdog.h>
#include <ipxe/efi/efi_null.h>
#include <ipxe/efi/efi_snp.h>
#include <usr/autoboot.h>
#include <config/general.h>

/** List of SNP devices */
static LIST_HEAD ( efi_snp_devices );

/** Network devices are currently claimed for use by iPXE */
static int efi_snp_claimed;

/** TPL prior to network devices being claimed */
static struct efi_saved_tpl efi_snp_saved_tpl;

/* Downgrade user experience if configured to do so
 *
 * The default UEFI user experience for network boot is somewhat
 * excremental: only TFTP is available as a download protocol, and if
 * anything goes wrong the user will be shown just a dot on an
 * otherwise blank screen.  (Some programmer was clearly determined to
 * win a bet that they could outshine Apple at producing uninformative
 * error messages.)
 *
 * For comparison, the default iPXE user experience provides the
 * option to use protocols designed more recently than 1980 (such as
 * HTTP and iSCSI), and if anything goes wrong the the user will be
 * shown one of over 1200 different error messages, complete with a
 * link to a wiki page describing that specific error.
 *
 * We default to upgrading the user experience to match that available
 * in a "legacy" BIOS environment, by installing our own instance of
 * EFI_LOAD_FILE_PROTOCOL.
 *
 * Note that unfortunately we can't sensibly provide the choice of
 * both options to the user in the same build, because the UEFI boot
 * menu ignores the multitude of ways in which a network device handle
 * can be described and opaquely labels both menu entries as just "EFI
 * Network".
 */
#ifdef EFI_DOWNGRADE_UX
static EFI_GUID dummy_load_file_protocol_guid = {
        0x6f6c7323, 0x2077, 0x7523,
        { 0x6e, 0x68, 0x65, 0x6c, 0x70, 0x66, 0x75, 0x6c }
};
#define efi_load_file_protocol_guid dummy_load_file_protocol_guid
#endif

/**
 * Set EFI SNP mode state
 *
 * @v snp               SNP interface
 */
static void efi_snp_set_state ( struct efi_snp_device *snpdev ) {
        struct net_device *netdev = snpdev->netdev;
        EFI_SIMPLE_NETWORK_MODE *mode = &snpdev->mode;

        /* Calculate state */
        if ( ! snpdev->started ) {
                /* Start() method not called; report as Stopped */
                mode->State = EfiSimpleNetworkStopped;
        } else if ( ! netdev_is_open ( netdev ) ) {
                /* Network device not opened; report as Started */
                mode->State = EfiSimpleNetworkStarted;
        } else if ( efi_snp_claimed ) {
                /* Network device opened but claimed for use by iPXE; report
                 * as Started to inhibit receive polling.
                 */
                mode->State = EfiSimpleNetworkStarted;
        } else {
                /* Network device opened and available for use via SNP; report
                 * as Initialized.
                 */
                mode->State = EfiSimpleNetworkInitialized;
        }
}

/**
 * Set EFI SNP mode based on iPXE net device parameters
 *
 * @v snp               SNP interface
 */
static void efi_snp_set_mode ( struct efi_snp_device *snpdev ) {
        struct net_device *netdev = snpdev->netdev;
        EFI_SIMPLE_NETWORK_MODE *mode = &snpdev->mode;
        struct ll_protocol *ll_protocol = netdev->ll_protocol;
        unsigned int ll_addr_len = ll_protocol->ll_addr_len;

        mode->HwAddressSize = ll_addr_len;
        mode->MediaHeaderSize = ll_protocol->ll_header_len;
        mode->MaxPacketSize = netdev->mtu;
        mode->ReceiveFilterMask = ( EFI_SIMPLE_NETWORK_RECEIVE_UNICAST |
                                    EFI_SIMPLE_NETWORK_RECEIVE_MULTICAST |
                                    EFI_SIMPLE_NETWORK_RECEIVE_BROADCAST );
        assert ( ll_addr_len <= sizeof ( mode->CurrentAddress ) );
        memcpy ( &mode->CurrentAddress, netdev->ll_addr, ll_addr_len );
        memcpy ( &mode->BroadcastAddress, netdev->ll_broadcast, ll_addr_len );
        ll_protocol->init_addr ( netdev->hw_addr, &mode->PermanentAddress );
        mode->IfType = ntohs ( ll_protocol->ll_proto );
        mode->MacAddressChangeable = TRUE;
        mode->MediaPresentSupported = TRUE;
        mode->MediaPresent = ( netdev_link_ok ( netdev ) ? TRUE : FALSE );
}

/**
 * Flush transmit ring and receive queue
 *
 * @v snpdev            SNP device
 */
static void efi_snp_flush ( struct efi_snp_device *snpdev ) {
        struct io_buffer *iobuf;
        struct io_buffer *tmp;

        /* Reset transmit completion ring */
        snpdev->tx_prod = 0;
        snpdev->tx_cons = 0;

        /* Discard any queued receive buffers */
        list_for_each_entry_safe ( iobuf, tmp, &snpdev->rx, list ) {
                list_del ( &iobuf->list );
                free_iob ( iobuf );
        }
}

/**
 * Poll net device and count received packets
 *
 * @v snpdev            SNP device
 */
static void efi_snp_poll ( struct efi_snp_device *snpdev ) {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        struct io_buffer *iobuf;

        /* Poll network device */
        netdev_poll ( snpdev->netdev );

        /* Retrieve any received packets */
        while ( ( iobuf = netdev_rx_dequeue ( snpdev->netdev ) ) ) {
                list_add_tail ( &iobuf->list, &snpdev->rx );
                snpdev->interrupts |= EFI_SIMPLE_NETWORK_RECEIVE_INTERRUPT;
                bs->SignalEvent ( snpdev->snp.WaitForPacket );
        }
}

/**
 * Change SNP state from "stopped" to "started"
 *
 * @v snp               SNP interface
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_start ( EFI_SIMPLE_NETWORK_PROTOCOL *snp ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );

        DBGC ( snpdev, "SNPDEV %p START\n", snpdev );

        /* Allow start even if net device is currently claimed by iPXE */
        if ( efi_snp_claimed ) {
                DBGC ( snpdev, "SNPDEV %p allowing start while claimed\n",
                       snpdev );
        }

        snpdev->started = 1;
        efi_snp_set_state ( snpdev );
        return 0;
}

/**
 * Change SNP state from "started" to "stopped"
 *
 * @v snp               SNP interface
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_stop ( EFI_SIMPLE_NETWORK_PROTOCOL *snp ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );

        DBGC ( snpdev, "SNPDEV %p STOP\n", snpdev );

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed )
                return EFI_NOT_READY;

        snpdev->started = 0;
        efi_snp_set_state ( snpdev );

        return 0;
}

/**
 * Open the network device
 *
 * @v snp               SNP interface
 * @v extra_rx_bufsize  Extra RX buffer size, in bytes
 * @v extra_tx_bufsize  Extra TX buffer size, in bytes
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_initialize ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
                     UINTN extra_rx_bufsize, UINTN extra_tx_bufsize ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );
        struct efi_saved_tpl tpl;
        int rc;

        DBGC ( snpdev, "SNPDEV %p INITIALIZE (%ld extra RX, %ld extra TX)\n",
               snpdev, ( ( unsigned long ) extra_rx_bufsize ),
               ( ( unsigned long ) extra_tx_bufsize ) );

        /* Do nothing if net device is currently claimed for use by
         * iPXE.  Do not return an error, because this will cause
         * MnpDxe et al to fail to install the relevant child handles
         * and to leave behind a partially initialised device handle
         * that can cause a later system crash.
         */
        if ( efi_snp_claimed ) {
                DBGC ( snpdev, "SNPDEV %p ignoring initialization while "
                       "claimed\n", snpdev );
                return 0;
        }

        /* Raise TPL */
        efi_raise_tpl ( &tpl );

        /* Open network device */
        if ( ( rc = netdev_open ( snpdev->netdev ) ) != 0 ) {
                DBGC ( snpdev, "SNPDEV %p could not open %s: %s\n",
                       snpdev, snpdev->netdev->name, strerror ( rc ) );
                goto err_open;
        }
        efi_snp_set_state ( snpdev );

 err_open:
        efi_restore_tpl ( &tpl );
        return EFIRC ( rc );
}

/**
 * Reset the network device
 *
 * @v snp               SNP interface
 * @v ext_verify        Extended verification required
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_reset ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, BOOLEAN ext_verify ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );
        struct efi_saved_tpl tpl;
        int rc;

        DBGC ( snpdev, "SNPDEV %p RESET (%s extended verification)\n",
               snpdev, ( ext_verify ? "with" : "without" ) );

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed ) {
                rc = -EAGAIN;
                goto err_claimed;
        }

        /* Raise TPL */
        efi_raise_tpl ( &tpl );

        /* Close network device */
        netdev_close ( snpdev->netdev );
        efi_snp_set_state ( snpdev );
        efi_snp_flush ( snpdev );

        /* Reopen network device */
        if ( ( rc = netdev_open ( snpdev->netdev ) ) != 0 ) {
                DBGC ( snpdev, "SNPDEV %p could not reopen %s: %s\n",
                       snpdev, snpdev->netdev->name, strerror ( rc ) );
                goto err_open;
        }
        efi_snp_set_state ( snpdev );

 err_open:
        efi_restore_tpl ( &tpl );
 err_claimed:
        return EFIRC ( rc );
}

/**
 * Shut down the network device
 *
 * @v snp               SNP interface
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_shutdown ( EFI_SIMPLE_NETWORK_PROTOCOL *snp ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );
        struct efi_saved_tpl tpl;

        DBGC ( snpdev, "SNPDEV %p SHUTDOWN\n", snpdev );

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed )
                return EFI_NOT_READY;

        /* Raise TPL */
        efi_raise_tpl ( &tpl );

        /* Close network device */
        netdev_close ( snpdev->netdev );
        efi_snp_set_state ( snpdev );
        efi_snp_flush ( snpdev );

        /* Restore TPL */
        efi_restore_tpl ( &tpl );

        return 0;
}

/**
 * Manage receive filters
 *
 * @v snp               SNP interface
 * @v enable            Receive filters to enable
 * @v disable           Receive filters to disable
 * @v mcast_reset       Reset multicast filters
 * @v mcast_count       Number of multicast filters
 * @v mcast             Multicast filters
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_receive_filters ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, UINT32 enable,
                          UINT32 disable, BOOLEAN mcast_reset,
                          UINTN mcast_count, EFI_MAC_ADDRESS *mcast ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );
        unsigned int i;

        DBGC ( snpdev, "SNPDEV %p RECEIVE_FILTERS %08x&~%08x%s %ld mcast\n",
               snpdev, enable, disable, ( mcast_reset ? " reset" : "" ),
               ( ( unsigned long ) mcast_count ) );
        for ( i = 0 ; i < mcast_count ; i++ ) {
                DBGC2_HDA ( snpdev, i, &mcast[i],
                            snpdev->netdev->ll_protocol->ll_addr_len );
        }

        /* Lie through our teeth, otherwise MNP refuses to accept us.
         *
         * Return success even if the SNP device is currently claimed
         * for use by iPXE, since otherwise Windows Deployment
         * Services refuses to attempt to receive further packets via
         * our EFI PXE Base Code protocol.
         */
        return 0;
}

/**
 * Set station address
 *
 * @v snp               SNP interface
 * @v reset             Reset to permanent address
 * @v new               New station address
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_station_address ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, BOOLEAN reset,
                          EFI_MAC_ADDRESS *new ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );
        struct ll_protocol *ll_protocol = snpdev->netdev->ll_protocol;

        DBGC ( snpdev, "SNPDEV %p STATION_ADDRESS %s\n", snpdev,
               ( reset ? "reset" : ll_protocol->ntoa ( new ) ) );

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed )
                return EFI_NOT_READY;

        /* Set the MAC address */
        if ( reset )
                new = &snpdev->mode.PermanentAddress;
        memcpy ( snpdev->netdev->ll_addr, new, ll_protocol->ll_addr_len );

        /* MAC address changes take effect only on netdev_open() */
        if ( netdev_is_open ( snpdev->netdev ) ) {
                DBGC ( snpdev, "SNPDEV %p MAC address changed while net "
                       "device open\n", snpdev );
        }

        return 0;
}

/**
 * Get (or reset) statistics
 *
 * @v snp               SNP interface
 * @v reset             Reset statistics
 * @v stats_len         Size of statistics table
 * @v stats             Statistics table
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_statistics ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, BOOLEAN reset,
                     UINTN *stats_len, EFI_NETWORK_STATISTICS *stats ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );
        EFI_NETWORK_STATISTICS stats_buf;

        DBGC ( snpdev, "SNPDEV %p STATISTICS%s", snpdev,
               ( reset ? " reset" : "" ) );

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed )
                return EFI_NOT_READY;

        /* Gather statistics */
        memset ( &stats_buf, 0, sizeof ( stats_buf ) );
        stats_buf.TxGoodFrames = snpdev->netdev->tx_stats.good;
        stats_buf.TxDroppedFrames = snpdev->netdev->tx_stats.bad;
        stats_buf.TxTotalFrames = ( snpdev->netdev->tx_stats.good +
                                    snpdev->netdev->tx_stats.bad );
        stats_buf.RxGoodFrames = snpdev->netdev->rx_stats.good;
        stats_buf.RxDroppedFrames = snpdev->netdev->rx_stats.bad;
        stats_buf.RxTotalFrames = ( snpdev->netdev->rx_stats.good +
                                    snpdev->netdev->rx_stats.bad );
        if ( *stats_len > sizeof ( stats_buf ) )
                *stats_len = sizeof ( stats_buf );
        if ( stats )
                memcpy ( stats, &stats_buf, *stats_len );

        /* Reset statistics if requested to do so */
        if ( reset ) {
                memset ( &snpdev->netdev->tx_stats, 0,
                         sizeof ( snpdev->netdev->tx_stats ) );
                memset ( &snpdev->netdev->rx_stats, 0,
                         sizeof ( snpdev->netdev->rx_stats ) );
        }

        return 0;
}

/**
 * Convert multicast IP address to MAC address
 *
 * @v snp               SNP interface
 * @v ipv6              Address is IPv6
 * @v ip                IP address
 * @v mac               MAC address
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_mcast_ip_to_mac ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, BOOLEAN ipv6,
                          EFI_IP_ADDRESS *ip, EFI_MAC_ADDRESS *mac ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );
        struct ll_protocol *ll_protocol = snpdev->netdev->ll_protocol;
        const char *ip_str;
        int rc;

        ip_str = ( ipv6 ? "(IPv6)" /* FIXME when we have inet6_ntoa() */ :
                   inet_ntoa ( *( ( struct in_addr * ) ip ) ) );
        DBGC ( snpdev, "SNPDEV %p MCAST_IP_TO_MAC %s\n", snpdev, ip_str );

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed )
                return EFI_NOT_READY;

        /* Try to hash the address */
        if ( ( rc = ll_protocol->mc_hash ( ( ipv6 ? AF_INET6 : AF_INET ),
                                           ip, mac ) ) != 0 ) {
                DBGC ( snpdev, "SNPDEV %p could not hash %s: %s\n",
                       snpdev, ip_str, strerror ( rc ) );
                return EFIRC ( rc );
        }

        return 0;
}

/**
 * Read or write non-volatile storage
 *
 * @v snp               SNP interface
 * @v read              Operation is a read
 * @v offset            Starting offset within NVRAM
 * @v len               Length of data buffer
 * @v data              Data buffer
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_nvdata ( EFI_SIMPLE_NETWORK_PROTOCOL *snp, BOOLEAN read,
                 UINTN offset, UINTN len, VOID *data ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );

        DBGC ( snpdev, "SNPDEV %p NVDATA %s %lx+%lx\n", snpdev,
               ( read ? "read" : "write" ), ( ( unsigned long ) offset ),
               ( ( unsigned long ) len ) );
        if ( ! read )
                DBGC2_HDA ( snpdev, offset, data, len );

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed )
                return EFI_NOT_READY;

        return EFI_UNSUPPORTED;
}

/**
 * Read interrupt status and TX recycled buffer status
 *
 * @v snp               SNP interface
 * @v interrupts        Interrupt status, or NULL
 * @v txbuf             Recycled transmit buffer address, or NULL
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_get_status ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
                     UINT32 *interrupts, VOID **txbuf ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );
        struct efi_saved_tpl tpl;

        DBGC2 ( snpdev, "SNPDEV %p GET_STATUS", snpdev );

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed ) {
                DBGC2 ( snpdev, "\n" );
                return EFI_NOT_READY;
        }

        /* Raise TPL */
        efi_raise_tpl ( &tpl );

        /* Poll the network device */
        efi_snp_poll ( snpdev );

        /* Interrupt status.  In practice, this seems to be used only
         * to detect TX completions.
         */
        if ( interrupts ) {
                *interrupts = snpdev->interrupts;
                DBGC2 ( snpdev, " INTS:%02x", *interrupts );
                snpdev->interrupts = 0;
        }

        /* TX completions */
        if ( txbuf ) {
                if ( snpdev->tx_prod != snpdev->tx_cons ) {
                        *txbuf = snpdev->tx[snpdev->tx_cons++ % EFI_SNP_NUM_TX];
                } else {
                        *txbuf = NULL;
                }
                DBGC2 ( snpdev, " TX:%p", *txbuf );
        }

        /* Restore TPL */
        efi_restore_tpl ( &tpl );

        DBGC2 ( snpdev, "\n" );
        return 0;
}

/**
 * Start packet transmission
 *
 * @v snp               SNP interface
 * @v ll_header_len     Link-layer header length, if to be filled in
 * @v len               Length of data buffer
 * @v data              Data buffer
 * @v ll_src            Link-layer source address, if specified
 * @v ll_dest           Link-layer destination address, if specified
 * @v net_proto         Network-layer protocol (in host order)
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_transmit ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
                   UINTN ll_header_len, UINTN len, VOID *data,
                   EFI_MAC_ADDRESS *ll_src, EFI_MAC_ADDRESS *ll_dest,
                   UINT16 *net_proto ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );
        struct ll_protocol *ll_protocol = snpdev->netdev->ll_protocol;
        struct efi_saved_tpl tpl;
        struct io_buffer *iobuf;
        size_t payload_len;
        unsigned int tx_fill;
        int rc;

        DBGC2 ( snpdev, "SNPDEV %p TRANSMIT %p+%lx", snpdev, data,
                ( ( unsigned long ) len ) );
        if ( ll_header_len ) {
                if ( ll_src ) {
                        DBGC2 ( snpdev, " src %s",
                                ll_protocol->ntoa ( ll_src ) );
                }
                if ( ll_dest ) {
                        DBGC2 ( snpdev, " dest %s",
                                ll_protocol->ntoa ( ll_dest ) );
                }
                if ( net_proto ) {
                        DBGC2 ( snpdev, " proto %04x", *net_proto );
                }
        }
        DBGC2 ( snpdev, "\n" );

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed ) {
                rc = -EAGAIN;
                goto err_claimed;
        }

        /* Raise TPL */
        efi_raise_tpl ( &tpl );

        /* Sanity checks */
        if ( ll_header_len ) {
                if ( ll_header_len != ll_protocol->ll_header_len ) {
                        DBGC ( snpdev, "SNPDEV %p TX invalid header length "
                               "%ld\n", snpdev,
                               ( ( unsigned long ) ll_header_len ) );
                        rc = -EINVAL;
                        goto err_sanity;
                }
                if ( len < ll_header_len ) {
                        DBGC ( snpdev, "SNPDEV %p invalid packet length %ld\n",
                               snpdev, ( ( unsigned long ) len ) );
                        rc = -EINVAL;
                        goto err_sanity;
                }
                if ( ! ll_dest ) {
                        DBGC ( snpdev, "SNPDEV %p TX missing destination "
                               "address\n", snpdev );
                        rc = -EINVAL;
                        goto err_sanity;
                }
                if ( ! net_proto ) {
                        DBGC ( snpdev, "SNPDEV %p TX missing network "
                               "protocol\n", snpdev );
                        rc = -EINVAL;
                        goto err_sanity;
                }
                if ( ! ll_src )
                        ll_src = &snpdev->mode.CurrentAddress;
        }

        /* Allocate buffer */
        payload_len = ( len - ll_protocol->ll_header_len );
        iobuf = alloc_iob ( MAX_LL_HEADER_LEN + ( ( payload_len > IOB_ZLEN ) ?
                                                  payload_len : IOB_ZLEN ) );
        if ( ! iobuf ) {
                DBGC ( snpdev, "SNPDEV %p TX could not allocate %ld-byte "
                       "buffer\n", snpdev, ( ( unsigned long ) len ) );
                rc = -ENOMEM;
                goto err_alloc_iob;
        }
        iob_reserve ( iobuf, ( MAX_LL_HEADER_LEN -
                               ll_protocol->ll_header_len ) );
        memcpy ( iob_put ( iobuf, len ), data, len );

        /* Create link-layer header, if specified */
        if ( ll_header_len ) {
                iob_pull ( iobuf, ll_protocol->ll_header_len );
                if ( ( rc = ll_protocol->push ( snpdev->netdev,
                                                iobuf, ll_dest, ll_src,
                                                htons ( *net_proto ) )) != 0 ){
                        DBGC ( snpdev, "SNPDEV %p TX could not construct "
                               "header: %s\n", snpdev, strerror ( rc ) );
                        goto err_ll_push;
                }
        }

        /* Transmit packet */
        if ( ( rc = netdev_tx ( snpdev->netdev, iob_disown ( iobuf ) ) ) != 0){
                DBGC ( snpdev, "SNPDEV %p TX could not transmit: %s\n",
                       snpdev, strerror ( rc ) );
                goto err_tx;
        }

        /* Record in transmit completion ring.  If we run out of
         * space, report the failure even though we have already
         * transmitted the packet.
         *
         * This allows us to report completions only for packets for
         * which we had reported successfully initiating transmission,
         * while continuing to support clients that never poll for
         * transmit completions.
         */
        tx_fill = ( snpdev->tx_prod - snpdev->tx_cons );
        if ( tx_fill >= EFI_SNP_NUM_TX ) {
                DBGC ( snpdev, "SNPDEV %p TX completion ring full\n", snpdev );
                rc = -ENOBUFS;
                goto err_ring_full;
        }
        snpdev->tx[ snpdev->tx_prod++ % EFI_SNP_NUM_TX ] = data;
        snpdev->interrupts |= EFI_SIMPLE_NETWORK_TRANSMIT_INTERRUPT;

        /* Restore TPL */
        efi_restore_tpl ( &tpl );

        return 0;

 err_ring_full:
 err_tx:
 err_ll_push:
        free_iob ( iobuf );
 err_alloc_iob:
 err_sanity:
        efi_restore_tpl ( &tpl );
 err_claimed:
        return EFIRC ( rc );
}

/**
 * Receive packet
 *
 * @v snp               SNP interface
 * @v ll_header_len     Link-layer header length, if to be filled in
 * @v len               Length of data buffer
 * @v data              Data buffer
 * @v ll_src            Link-layer source address, if specified
 * @v ll_dest           Link-layer destination address, if specified
 * @v net_proto         Network-layer protocol (in host order)
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_receive ( EFI_SIMPLE_NETWORK_PROTOCOL *snp,
                  UINTN *ll_header_len, UINTN *len, VOID *data,
                  EFI_MAC_ADDRESS *ll_src, EFI_MAC_ADDRESS *ll_dest,
                  UINT16 *net_proto ) {
        struct efi_snp_device *snpdev =
                container_of ( snp, struct efi_snp_device, snp );
        struct ll_protocol *ll_protocol = snpdev->netdev->ll_protocol;
        struct efi_saved_tpl tpl;
        struct io_buffer *iobuf;
        const void *iob_ll_dest;
        const void *iob_ll_src;
        uint16_t iob_net_proto;
        unsigned int iob_flags;
        size_t copy_len;
        int rc;

        DBGC2 ( snpdev, "SNPDEV %p RECEIVE %p(+%lx)", snpdev, data,
                ( ( unsigned long ) *len ) );

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed ) {
                rc = -EAGAIN;
                goto err_claimed;
        }

        /* Raise TPL */
        efi_raise_tpl ( &tpl );

        /* Poll the network device */
        efi_snp_poll ( snpdev );

        /* Check for an available packet */
        iobuf = list_first_entry ( &snpdev->rx, struct io_buffer, list );
        if ( ! iobuf ) {
                DBGC2 ( snpdev, "\n" );
                rc = -EAGAIN;
                goto out_no_packet;
        }
        DBGC2 ( snpdev, "+%zx\n", iob_len ( iobuf ) );

        /* Dequeue packet */
        list_del ( &iobuf->list );

        /* Return packet to caller, truncating to buffer length */
        copy_len = iob_len ( iobuf );
        if ( copy_len > *len )
                copy_len = *len;
        memcpy ( data, iobuf->data, copy_len );
        *len = iob_len ( iobuf );

        /* Attempt to decode link-layer header */
        if ( ( rc = ll_protocol->pull ( snpdev->netdev, iobuf, &iob_ll_dest,
                                        &iob_ll_src, &iob_net_proto,
                                        &iob_flags ) ) != 0 ) {
                DBGC ( snpdev, "SNPDEV %p could not parse header: %s\n",
                       snpdev, strerror ( rc ) );
                goto out_bad_ll_header;
        }

        /* Return link-layer header parameters to caller, if required */
        if ( ll_header_len )
                *ll_header_len = ll_protocol->ll_header_len;
        if ( ll_src )
                memcpy ( ll_src, iob_ll_src, ll_protocol->ll_addr_len );
        if ( ll_dest )
                memcpy ( ll_dest, iob_ll_dest, ll_protocol->ll_addr_len );
        if ( net_proto )
                *net_proto = ntohs ( iob_net_proto );

        /* Check buffer length */
        rc = ( ( copy_len == *len ) ? 0 : -ERANGE );

 out_bad_ll_header:
        free_iob ( iobuf );
 out_no_packet:
        efi_restore_tpl ( &tpl );
 err_claimed:
        return EFIRC ( rc );
}

/**
 * Poll event
 *
 * @v event             Event
 * @v context           Event context
 */
static VOID EFIAPI efi_snp_wait_for_packet ( EFI_EVENT event __unused,
                                             VOID *context ) {
        struct efi_snp_device *snpdev = context;
        struct efi_saved_tpl tpl;

        DBGCP ( snpdev, "SNPDEV %p WAIT_FOR_PACKET\n", snpdev );

        /* Do nothing unless the net device is open */
        if ( ! netdev_is_open ( snpdev->netdev ) )
                return;

        /* Do nothing if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed )
                return;

        /* Raise TPL */
        efi_raise_tpl ( &tpl );

        /* Poll the network device */
        efi_snp_poll ( snpdev );

        /* Restore TPL */
        efi_restore_tpl ( &tpl );
}

/** SNP interface */
static EFI_SIMPLE_NETWORK_PROTOCOL efi_snp_device_snp = {
        .Revision       = EFI_SIMPLE_NETWORK_PROTOCOL_REVISION,
        .Start          = efi_snp_start,
        .Stop           = efi_snp_stop,
        .Initialize     = efi_snp_initialize,
        .Reset          = efi_snp_reset,
        .Shutdown       = efi_snp_shutdown,
        .ReceiveFilters = efi_snp_receive_filters,
        .StationAddress = efi_snp_station_address,
        .Statistics     = efi_snp_statistics,
        .MCastIpToMac   = efi_snp_mcast_ip_to_mac,
        .NvData         = efi_snp_nvdata,
        .GetStatus      = efi_snp_get_status,
        .Transmit       = efi_snp_transmit,
        .Receive        = efi_snp_receive,
};

/******************************************************************************
 *
 * UNDI protocol
 *
 ******************************************************************************
 */

/** Union type for command parameter blocks */
typedef union {
        PXE_CPB_STATION_ADDRESS station_address;
        PXE_CPB_FILL_HEADER fill_header;
        PXE_CPB_FILL_HEADER_FRAGMENTED fill_header_fragmented;
        PXE_CPB_TRANSMIT transmit;
        PXE_CPB_RECEIVE receive;
} PXE_CPB_ANY;

/** Union type for data blocks */
typedef union {
        PXE_DB_GET_INIT_INFO get_init_info;
        PXE_DB_STATION_ADDRESS station_address;
        PXE_DB_GET_STATUS get_status;
        PXE_DB_RECEIVE receive;
} PXE_DB_ANY;

/**
 * Calculate UNDI byte checksum
 *
 * @v data              Data
 * @v len               Length of data
 * @ret sum             Checksum
 */
static uint8_t efi_undi_checksum ( void *data, size_t len ) {
        uint8_t *bytes = data;
        uint8_t sum = 0;

        while ( len-- )
                sum += *bytes++;
        return sum;
}

/**
 * Get UNDI SNP device interface number
 *
 * @v snpdev            SNP device
 * @ret ifnum           UNDI interface number
 */
static unsigned int efi_undi_ifnum ( struct efi_snp_device *snpdev ) {

        /* iPXE network device scope IDs are one-based (leaving zero
         * meaning "unspecified").  UNDI interface numbers are
         * zero-based.
         */
        return ( snpdev->netdev->scope_id - 1 );
}

/**
 * Identify UNDI SNP device
 *
 * @v ifnum             Interface number
 * @ret snpdev          SNP device, or NULL if not found
 */
static struct efi_snp_device * efi_undi_snpdev ( unsigned int ifnum ) {
        struct efi_snp_device *snpdev;

        list_for_each_entry ( snpdev, &efi_snp_devices, list ) {
                if ( efi_undi_ifnum ( snpdev ) == ifnum )
                        return snpdev;
        }
        return NULL;
}

/**
 * Convert EFI status code to UNDI status code
 *
 * @v efirc             EFI status code
 * @ret statcode        UNDI status code
 */
static PXE_STATCODE efi_undi_statcode ( EFI_STATUS efirc ) {

        switch ( efirc ) {
        case EFI_INVALID_PARAMETER:     return PXE_STATCODE_INVALID_PARAMETER;
        case EFI_UNSUPPORTED:           return PXE_STATCODE_UNSUPPORTED;
        case EFI_OUT_OF_RESOURCES:      return PXE_STATCODE_BUFFER_FULL;
        case EFI_PROTOCOL_ERROR:        return PXE_STATCODE_DEVICE_FAILURE;
        case EFI_NOT_READY:             return PXE_STATCODE_NO_DATA;
        default:
                return PXE_STATCODE_INVALID_CDB;
        }
}

/**
 * Get state
 *
 * @v snpdev            SNP device
 * @v cdb               Command description block
 * @ret efirc           EFI status code
 */
static EFI_STATUS efi_undi_get_state ( struct efi_snp_device *snpdev,
                                       PXE_CDB *cdb ) {
        EFI_SIMPLE_NETWORK_MODE *mode = &snpdev->mode;

        DBGC ( snpdev, "UNDI %p GET STATE\n", snpdev );

        /* Return current state */
        if ( mode->State == EfiSimpleNetworkInitialized ) {
                cdb->StatFlags |= PXE_STATFLAGS_GET_STATE_INITIALIZED;
        } else if ( mode->State == EfiSimpleNetworkStarted ) {
                cdb->StatFlags |= PXE_STATFLAGS_GET_STATE_STARTED;
        } else {
                cdb->StatFlags |= PXE_STATFLAGS_GET_STATE_STOPPED;
        }

        return 0;
}

/**
 * Start
 *
 * @v snpdev            SNP device
 * @ret efirc           EFI status code
 */
static EFI_STATUS efi_undi_start ( struct efi_snp_device *snpdev ) {
        EFI_STATUS efirc;

        DBGC ( snpdev, "UNDI %p START\n", snpdev );

        /* Start SNP device */
        if ( ( efirc = efi_snp_start ( &snpdev->snp ) ) != 0 )
                return efirc;

        return 0;
}

/**
 * Stop
 *
 * @v snpdev            SNP device
 * @ret efirc           EFI status code
 */
static EFI_STATUS efi_undi_stop ( struct efi_snp_device *snpdev ) {
        EFI_STATUS efirc;

        DBGC ( snpdev, "UNDI %p STOP\n", snpdev );

        /* Stop SNP device */
        if ( ( efirc = efi_snp_stop ( &snpdev->snp ) ) != 0 )
                return efirc;

        return 0;
}

/**
 * Get initialisation information
 *
 * @v snpdev            SNP device
 * @v cdb               Command description block
 * @v db                Data block
 * @ret efirc           EFI status code
 */
static EFI_STATUS efi_undi_get_init_info ( struct efi_snp_device *snpdev,
                                           PXE_CDB *cdb,
                                           PXE_DB_GET_INIT_INFO *db ) {
        struct net_device *netdev = snpdev->netdev;
        struct ll_protocol *ll_protocol = netdev->ll_protocol;

        DBGC ( snpdev, "UNDI %p GET INIT INFO\n", snpdev );

        /* Populate structure */
        memset ( db, 0, sizeof ( *db ) );
        db->FrameDataLen = ( netdev->max_pkt_len - ll_protocol->ll_header_len );
        db->MediaHeaderLen = ll_protocol->ll_header_len;
        db->HWaddrLen = ll_protocol->ll_addr_len;
        db->IFtype = ntohs ( ll_protocol->ll_proto );
        cdb->StatFlags |= ( PXE_STATFLAGS_CABLE_DETECT_SUPPORTED |
                            PXE_STATFLAGS_GET_STATUS_NO_MEDIA_SUPPORTED );

        return 0;
}

/**
 * Initialise
 *
 * @v snpdev            SNP device
 * @v cdb               Command description block
 * @v efirc             EFI status code
 */
static EFI_STATUS efi_undi_initialize ( struct efi_snp_device *snpdev,
                                        PXE_CDB *cdb ) {
        struct net_device *netdev = snpdev->netdev;
        EFI_STATUS efirc;

        DBGC ( snpdev, "UNDI %p INITIALIZE\n", snpdev );

        /* Reset SNP device */
        if ( ( efirc = efi_snp_initialize ( &snpdev->snp, 0, 0 ) ) != 0 )
                return efirc;

        /* Report link state */
        if ( ! netdev_link_ok ( netdev ) )
                cdb->StatFlags |= PXE_STATFLAGS_INITIALIZED_NO_MEDIA;

        return 0;
}

/**
 * Reset
 *
 * @v snpdev            SNP device
 * @v efirc             EFI status code
 */
static EFI_STATUS efi_undi_reset ( struct efi_snp_device *snpdev ) {
        EFI_STATUS efirc;

        DBGC ( snpdev, "UNDI %p RESET\n", snpdev );

        /* Reset SNP device */
        if ( ( efirc = efi_snp_reset ( &snpdev->snp, 0 ) ) != 0 )
                return efirc;

        return 0;
}

/**
 * Shutdown
 *
 * @v snpdev            SNP device
 * @v efirc             EFI status code
 */
static EFI_STATUS efi_undi_shutdown ( struct efi_snp_device *snpdev ) {
        EFI_STATUS efirc;

        DBGC ( snpdev, "UNDI %p SHUTDOWN\n", snpdev );

        /* Reset SNP device */
        if ( ( efirc = efi_snp_shutdown ( &snpdev->snp ) ) != 0 )
                return efirc;

        return 0;
}

/**
 * Get/set receive filters
 *
 * @v snpdev            SNP device
 * @v cdb               Command description block
 * @v efirc             EFI status code
 */
static EFI_STATUS efi_undi_receive_filters ( struct efi_snp_device *snpdev,
                                             PXE_CDB *cdb ) {

        DBGC ( snpdev, "UNDI %p RECEIVE FILTERS\n", snpdev );

        /* Mark everything as supported */
        cdb->StatFlags |= ( PXE_STATFLAGS_RECEIVE_FILTER_UNICAST |
                            PXE_STATFLAGS_RECEIVE_FILTER_BROADCAST |
                            PXE_STATFLAGS_RECEIVE_FILTER_PROMISCUOUS |
                            PXE_STATFLAGS_RECEIVE_FILTER_ALL_MULTICAST );

        return 0;
}

/**
 * Get/set station address
 *
 * @v snpdev            SNP device
 * @v cdb               Command description block
 * @v cpb               Command parameter block
 * @v efirc             EFI status code
 */
static EFI_STATUS efi_undi_station_address ( struct efi_snp_device *snpdev,
                                             PXE_CDB *cdb,
                                             PXE_CPB_STATION_ADDRESS *cpb,
                                             PXE_DB_STATION_ADDRESS *db ) {
        struct net_device *netdev = snpdev->netdev;
        struct ll_protocol *ll_protocol = netdev->ll_protocol;
        void *mac;
        int reset;
        EFI_STATUS efirc;

        DBGC ( snpdev, "UNDI %p STATION ADDRESS\n", snpdev );

        /* Update address if applicable */
        reset = ( cdb->OpFlags & PXE_OPFLAGS_STATION_ADDRESS_RESET );
        mac = ( cpb ? &cpb->StationAddr : NULL );
        if ( ( reset || mac ) &&
             ( ( efirc = efi_snp_station_address ( &snpdev->snp, reset,
                                                   mac ) ) != 0 ) )
                return efirc;

        /* Fill in current addresses, if applicable */
        if ( db ) {
                memset ( db, 0, sizeof ( *db ) );
                memcpy ( &db->StationAddr, netdev->ll_addr,
                         ll_protocol->ll_addr_len );
                memcpy ( &db->BroadcastAddr, netdev->ll_broadcast,
                         ll_protocol->ll_addr_len );
                memcpy ( &db->PermanentAddr, netdev->hw_addr,
                         ll_protocol->hw_addr_len );
        }

        return 0;
}

/**
 * Get interrupt status
 *
 * @v snpdev            SNP device
 * @v cdb               Command description block
 * @v db                Data block
 * @v efirc             EFI status code
 */
static EFI_STATUS efi_undi_get_status ( struct efi_snp_device *snpdev,
                                        PXE_CDB *cdb, PXE_DB_GET_STATUS *db ) {
        UINT32 interrupts;
        VOID *txbuf;
        struct io_buffer *rxbuf;
        EFI_STATUS efirc;

        DBGC2 ( snpdev, "UNDI %p GET STATUS\n", snpdev );

        /* Get status */
        if ( ( efirc = efi_snp_get_status ( &snpdev->snp, &interrupts,
                                            &txbuf ) ) != 0 )
                return efirc;

        /* Report status */
        memset ( db, 0, sizeof ( *db ) );
        if ( interrupts & EFI_SIMPLE_NETWORK_RECEIVE_INTERRUPT )
                cdb->StatFlags |= PXE_STATFLAGS_GET_STATUS_RECEIVE;
        if ( interrupts & EFI_SIMPLE_NETWORK_TRANSMIT_INTERRUPT )
                cdb->StatFlags |= PXE_STATFLAGS_GET_STATUS_TRANSMIT;
        if ( txbuf ) {
                db->TxBuffer[0] = ( ( intptr_t ) txbuf );
        } else {
                cdb->StatFlags |= PXE_STATFLAGS_GET_STATUS_NO_TXBUFS_WRITTEN;
                /* The specification states clearly that UNDI drivers
                 * should set TXBUF_QUEUE_EMPTY if all completed
                 * buffer addresses are written into the returned data
                 * block.  However, SnpDxe chooses to interpret
                 * TXBUF_QUEUE_EMPTY as a synonym for
                 * NO_TXBUFS_WRITTEN, thereby rendering it entirely
                 * pointless.  Work around this UEFI stupidity, as per
                 * usual.
                 */
                if ( snpdev->tx_prod == snpdev->tx_cons )
                        cdb->StatFlags |=
                                PXE_STATFLAGS_GET_STATUS_TXBUF_QUEUE_EMPTY;
        }
        rxbuf = list_first_entry ( &snpdev->rx, struct io_buffer, list );
        if ( rxbuf )
                db->RxFrameLen = iob_len ( rxbuf );
        if ( ! netdev_link_ok ( snpdev->netdev ) )
                cdb->StatFlags |= PXE_STATFLAGS_GET_STATUS_NO_MEDIA;

        return 0;
}

/**
 * Fill header
 *
 * @v snpdev            SNP device
 * @v cdb               Command description block
 * @v cpb               Command parameter block
 * @v efirc             EFI status code
 */
static EFI_STATUS efi_undi_fill_header ( struct efi_snp_device *snpdev,
                                         PXE_CDB *cdb, PXE_CPB_ANY *cpb ) {
        struct net_device *netdev = snpdev->netdev;
        struct ll_protocol *ll_protocol = netdev->ll_protocol;
        PXE_CPB_FILL_HEADER *whole = &cpb->fill_header;
        PXE_CPB_FILL_HEADER_FRAGMENTED *fragged = &cpb->fill_header_fragmented;
        VOID *data;
        void *dest;
        void *src;
        uint16_t proto;
        struct io_buffer iobuf;
        int rc;

        /* SnpDxe will (pointlessly) use PXE_CPB_FILL_HEADER_FRAGMENTED
         * even though we choose to explicitly not claim support for
         * fragments via PXE_ROMID_IMP_FRAG_SUPPORTED.
         */
        if ( cdb->OpFlags & PXE_OPFLAGS_FILL_HEADER_FRAGMENTED ) {
                data = ( ( void * ) ( intptr_t ) fragged->FragDesc[0].FragAddr);
                dest = &fragged->DestAddr;
                src = &fragged->SrcAddr;
                proto = fragged->Protocol;
        } else {
                data = ( ( void * ) ( intptr_t ) whole->MediaHeader );
                dest = &whole->DestAddr;
                src = &whole->SrcAddr;
                proto = whole->Protocol;
        }

        /* Construct link-layer header */
        iob_populate ( &iobuf, data, 0, ll_protocol->ll_header_len );
        iob_reserve ( &iobuf, ll_protocol->ll_header_len );
        if ( ( rc = ll_protocol->push ( netdev, &iobuf, dest, src,
                                        proto ) ) != 0 )
                return EFIRC ( rc );

        return 0;
}

/**
 * Transmit
 *
 * @v snpdev            SNP device
 * @v cpb               Command parameter block
 * @v efirc             EFI status code
 */
static EFI_STATUS efi_undi_transmit ( struct efi_snp_device *snpdev,
                                      PXE_CPB_TRANSMIT *cpb ) {
        VOID *data = ( ( void * ) ( intptr_t ) cpb->FrameAddr );
        EFI_STATUS efirc;

        DBGC2 ( snpdev, "UNDI %p TRANSMIT\n", snpdev );

        /* Transmit packet */
        if ( ( efirc = efi_snp_transmit ( &snpdev->snp, 0, cpb->DataLen,
                                          data, NULL, NULL, NULL ) ) != 0 )
                return efirc;

        return 0;
}

/**
 * Receive
 *
 * @v snpdev            SNP device
 * @v cpb               Command parameter block
 * @v efirc             EFI status code
 */
static EFI_STATUS efi_undi_receive ( struct efi_snp_device *snpdev,
                                     PXE_CPB_RECEIVE *cpb,
                                     PXE_DB_RECEIVE *db ) {
        struct net_device *netdev = snpdev->netdev;
        struct ll_protocol *ll_protocol = netdev->ll_protocol;
        VOID *data = ( ( void * ) ( intptr_t ) cpb->BufferAddr );
        UINTN hdr_len;
        UINTN len = cpb->BufferLen;
        EFI_MAC_ADDRESS src;
        EFI_MAC_ADDRESS dest;
        UINT16 proto;
        EFI_STATUS efirc;

        DBGC2 ( snpdev, "UNDI %p RECEIVE\n", snpdev );

        /* Receive packet */
        if ( ( efirc = efi_snp_receive ( &snpdev->snp, &hdr_len, &len, data,
                                         &src, &dest, &proto ) ) != 0 )
                return efirc;

        /* Describe frame */
        memset ( db, 0, sizeof ( *db ) );
        memcpy ( &db->SrcAddr, &src, ll_protocol->ll_addr_len );
        memcpy ( &db->DestAddr, &dest, ll_protocol->ll_addr_len );
        db->FrameLen = len;
        db->Protocol = proto;
        db->MediaHeaderLen = ll_protocol->ll_header_len;
        db->Type = PXE_FRAME_TYPE_PROMISCUOUS;

        return 0;
}

/** UNDI entry point */
static EFIAPI VOID efi_undi_issue ( UINT64 cdb_phys ) {
        PXE_CDB *cdb = ( ( void * ) ( intptr_t ) cdb_phys );
        PXE_CPB_ANY *cpb = ( ( void * ) ( intptr_t ) cdb->CPBaddr );
        PXE_DB_ANY *db = ( ( void * ) ( intptr_t ) cdb->DBaddr );
        struct efi_snp_device *snpdev;
        EFI_STATUS efirc;

        /* Identify device */
        snpdev = efi_undi_snpdev ( cdb->IFnum );
        if ( ! snpdev ) {
                DBGC ( cdb, "UNDI invalid interface number %d\n", cdb->IFnum );
                cdb->StatCode = PXE_STATCODE_INVALID_CDB;
                cdb->StatFlags = PXE_STATFLAGS_COMMAND_FAILED;
                return;
        }

        /* Fail if net device is currently claimed for use by iPXE */
        if ( efi_snp_claimed ) {
                cdb->StatCode = PXE_STATCODE_BUSY;
                cdb->StatFlags = PXE_STATFLAGS_COMMAND_FAILED;
                return;
        }

        /* Handle opcode */
        cdb->StatCode = PXE_STATCODE_SUCCESS;
        cdb->StatFlags = PXE_STATFLAGS_COMMAND_COMPLETE;
        switch ( cdb->OpCode ) {

        case PXE_OPCODE_GET_STATE:
                efirc = efi_undi_get_state ( snpdev, cdb );
                break;

        case PXE_OPCODE_START:
                efirc = efi_undi_start ( snpdev );
                break;

        case PXE_OPCODE_STOP:
                efirc = efi_undi_stop ( snpdev );
                break;

        case PXE_OPCODE_GET_INIT_INFO:
                efirc = efi_undi_get_init_info ( snpdev, cdb,
                                                 &db->get_init_info );
                break;

        case PXE_OPCODE_INITIALIZE:
                efirc = efi_undi_initialize ( snpdev, cdb );
                break;

        case PXE_OPCODE_RESET:
                efirc = efi_undi_reset ( snpdev );
                break;

        case PXE_OPCODE_SHUTDOWN:
                efirc = efi_undi_shutdown ( snpdev );
                break;

        case PXE_OPCODE_RECEIVE_FILTERS:
                efirc = efi_undi_receive_filters ( snpdev, cdb );
                break;

        case PXE_OPCODE_STATION_ADDRESS:
                efirc = efi_undi_station_address ( snpdev, cdb,
                                                   &cpb->station_address,
                                                   &db->station_address );
                break;

        case PXE_OPCODE_GET_STATUS:
                efirc = efi_undi_get_status ( snpdev, cdb, &db->get_status );
                break;

        case PXE_OPCODE_FILL_HEADER:
                efirc = efi_undi_fill_header ( snpdev, cdb, cpb );
                break;

        case PXE_OPCODE_TRANSMIT:
                efirc = efi_undi_transmit ( snpdev, &cpb->transmit );
                break;

        case PXE_OPCODE_RECEIVE:
                efirc = efi_undi_receive ( snpdev, &cpb->receive,
                                           &db->receive );
                break;

        default:
                DBGC ( snpdev, "UNDI %p unsupported opcode %#04x\n",
                       snpdev, cdb->OpCode );
                efirc = EFI_UNSUPPORTED;
                break;
        }

        /* Convert EFI status code to UNDI status code */
        if ( efirc != 0 ) {
                cdb->StatFlags &= ~PXE_STATFLAGS_STATUS_MASK;
                cdb->StatFlags |= PXE_STATFLAGS_COMMAND_FAILED;
                cdb->StatCode = efi_undi_statcode ( efirc );
        }
}

/** UNDI interface
 *
 * Must be aligned on a 16-byte boundary, for no particularly good
 * reason.
 */
static PXE_SW_UNDI efi_snp_undi __attribute__ (( aligned ( 16 ) )) = {
        .Signature      = PXE_ROMID_SIGNATURE,
        .Len            = sizeof ( efi_snp_undi ),
        .Rev            = PXE_ROMID_REV,
        .MajorVer       = PXE_ROMID_MAJORVER,
        .MinorVer       = PXE_ROMID_MINORVER,
        .Implementation = ( PXE_ROMID_IMP_SW_VIRT_ADDR |
                            PXE_ROMID_IMP_STATION_ADDR_SETTABLE |
                            PXE_ROMID_IMP_PROMISCUOUS_MULTICAST_RX_SUPPORTED |
                            PXE_ROMID_IMP_PROMISCUOUS_RX_SUPPORTED |
                            PXE_ROMID_IMP_BROADCAST_RX_SUPPORTED |
                            PXE_ROMID_IMP_TX_COMPLETE_INT_SUPPORTED |
                            PXE_ROMID_IMP_PACKET_RX_INT_SUPPORTED ),
        /* SnpDxe checks that BusCnt is non-zero.  It makes no further
         * use of BusCnt, and never looks as BusType[].  As with much
         * of the EDK2 code, this check seems to serve no purpose
         * whatsoever but must nonetheless be humoured.
         */
        .BusCnt         = 1,
        .BusType[0]     = PXE_BUSTYPE ( 'i', 'P', 'X', 'E' ),
};

/** Network Identification Interface (NII) */
static EFI_NETWORK_INTERFACE_IDENTIFIER_PROTOCOL efi_snp_device_nii = {
        .Revision       = EFI_NETWORK_INTERFACE_IDENTIFIER_PROTOCOL_REVISION,
        .StringId       = "UNDI",
        .Type           = EfiNetworkInterfaceUndi,
        .MajorVer       = 3,
        .MinorVer       = 1,
        .Ipv6Supported  = TRUE, /* This is a raw packet interface, FFS! */
};

/******************************************************************************
 *
 * VLAN configuration protocol
 *
 ******************************************************************************
 */

/**
 * Create or modify VLAN device
 *
 * @v vcfg              VLAN configuration protocol
 * @v tag               VLAN tag
 * @v priority          Default VLAN priority
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_vlan_set ( EFI_VLAN_CONFIG_PROTOCOL *vcfg,
                                        UINT16 tag, UINT8 priority ) {
        struct efi_snp_device *snpdev =
                container_of ( vcfg, struct efi_snp_device, vcfg );
        struct net_device *trunk = snpdev->netdev;
        struct efi_saved_tpl tpl;
        int rc;

        /* Raise TPL */
        efi_raise_tpl ( &tpl );

        /* Create or modify VLAN device */
        if ( ( rc = vlan_create ( trunk, tag, priority ) ) != 0 ) {
                DBGC ( snpdev, "SNPDEV %p could not create VLAN tag %d: %s\n",
                       snpdev, tag, strerror ( rc ) );
                goto err_create;
        }
        DBGC ( snpdev, "SNPDEV %p created VLAN tag %d priority %d\n",
               snpdev, tag, priority );

 err_create:
        efi_restore_tpl ( &tpl );
        return EFIRC ( rc );
}

/**
 * Find VLAN device(s)
 *
 * @v vcfg              VLAN configuration protocol
 * @v filter            VLAN tag, or NULL to find all VLANs
 * @v count             Number of VLANs
 * @v entries           List of VLANs
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_vlan_find ( EFI_VLAN_CONFIG_PROTOCOL *vcfg,
                                         UINT16 *filter, UINT16 *count,
                                         EFI_VLAN_FIND_DATA **entries ) {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        struct efi_snp_device *snpdev =
                container_of ( vcfg, struct efi_snp_device, vcfg );
        struct net_device *trunk = snpdev->netdev;
        struct net_device *vlan;
        struct efi_saved_tpl tpl;
        EFI_VLAN_FIND_DATA *entry;
        VOID *buffer;
        unsigned int tag;
        unsigned int tci;
        size_t len;
        EFI_STATUS efirc;
        int rc;

        /* Raise TPL */
        efi_raise_tpl ( &tpl );

        /* Count number of matching VLANs */
        *count = 0;
        for ( tag = 1 ; VLAN_TAG_IS_VALID ( tag ) ; tag++ ) {
                if ( filter && ( tag != *filter ) )
                        continue;
                if ( ! ( vlan = vlan_find ( trunk, tag ) ) )
                        continue;
                (*count)++;
        }

        /* Allocate buffer to hold results */
        len = ( (*count) * sizeof ( *entry ) );
        if ( ( efirc = bs->AllocatePool ( EfiBootServicesData, len,
                                          &buffer ) ) != 0 ) {
                rc = -EEFI ( efirc );
                goto err_alloc;
        }

        /* Fill in buffer */
        *entries = buffer;
        entry = *entries;
        for ( tag = 1 ; VLAN_TAG_IS_VALID ( tag ) ; tag++ ) {
                if ( filter && ( tag != *filter ) )
                        continue;
                if ( ! ( vlan = vlan_find ( trunk, tag ) ) )
                        continue;
                tci = vlan_tci ( vlan );
                entry->VlanId = VLAN_TAG ( tci );
                entry->Priority = VLAN_PRIORITY ( tci );
                assert ( entry->VlanId == tag );
                entry++;
        }
        assert ( entry == &(*entries)[*count] );

        /* Success */
        rc = 0;

 err_alloc:
        efi_restore_tpl ( &tpl );
        return EFIRC ( rc );
}

/**
 * Remove VLAN device
 *
 * @v vcfg              VLAN configuration protocol
 * @v tag               VLAN tag
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI efi_vlan_remove ( EFI_VLAN_CONFIG_PROTOCOL *vcfg,
                                           UINT16 tag ) {
        struct efi_snp_device *snpdev =
                container_of ( vcfg, struct efi_snp_device, vcfg );
        struct net_device *trunk = snpdev->netdev;
        struct net_device *vlan;
        struct efi_saved_tpl tpl;
        int rc;

        /* Raise TPL */
        efi_raise_tpl ( &tpl );

        /* Identify VLAN device */
        vlan = vlan_find ( trunk, tag );
        if ( ! vlan ) {
                DBGC ( snpdev, "SNPDEV %p could not find VLAN tag %d\n",
                       snpdev, tag );
                rc = -ENOENT;
                goto err_find;
        }

        /* Remove VLAN device */
        vlan_destroy ( vlan );
        DBGC ( snpdev, "SNPDEV %p removed VLAN tag %d\n", snpdev, tag );

        /* Success */
        rc = 0;

 err_find:
        efi_restore_tpl ( &tpl );
        return EFIRC ( rc );
}

/** VLAN configuration protocol */
static EFI_VLAN_CONFIG_PROTOCOL efi_vlan = {
        .Set            = efi_vlan_set,
        .Find           = efi_vlan_find,
        .Remove         = efi_vlan_remove,
};

/******************************************************************************
 *
 * Component name protocol
 *
 ******************************************************************************
 */

/**
 * Look up driver name
 *
 * @v name2             Component name protocol
 * @v language          Language to use
 * @v driver_name       Driver name to fill in
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_get_driver_name ( EFI_COMPONENT_NAME2_PROTOCOL *name2,
                          CHAR8 *language __unused, CHAR16 **driver_name ) {
        struct efi_snp_device *snpdev =
                container_of ( name2, struct efi_snp_device, name2 );

        *driver_name = snpdev->driver_name;
        return 0;
}

/**
 * Look up controller name
 *
 * @v name2                     Component name protocol
 * @v device            Device
 * @v child             Child device, or NULL
 * @v language          Language to use
 * @v driver_name       Device name to fill in
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_get_controller_name ( EFI_COMPONENT_NAME2_PROTOCOL *name2,
                              EFI_HANDLE device __unused,
                              EFI_HANDLE child __unused,
                              CHAR8 *language __unused,
                              CHAR16 **controller_name ) {
        struct efi_snp_device *snpdev =
                container_of ( name2, struct efi_snp_device, name2 );

        *controller_name = snpdev->controller_name;
        return 0;
}

/******************************************************************************
 *
 * Load file protocol
 *
 ******************************************************************************
 */

/**
 * Load file
 *
 * @v loadfile          Load file protocol
 * @v path              File path
 * @v booting           Loading as part of a boot attempt
 * @ret efirc           EFI status code
 */
static EFI_STATUS EFIAPI
efi_snp_load_file ( EFI_LOAD_FILE_PROTOCOL *load_file,
                    EFI_DEVICE_PATH_PROTOCOL *path __unused,
                    BOOLEAN booting, UINTN *len __unused,
                    VOID *data __unused ) {
        struct efi_snp_device *snpdev =
                container_of ( load_file, struct efi_snp_device, load_file );
        struct net_device *netdev = snpdev->netdev;
        int rc;

        /* Fail unless this is a boot attempt */
        if ( ! booting ) {
                DBGC ( snpdev, "SNPDEV %p cannot load non-boot file\n",
                       snpdev );
                return EFI_UNSUPPORTED;
        }

        /* Claim network devices for use by iPXE */
        efi_snp_claim();

        /* Start watchdog holdoff timer */
        efi_watchdog_start();

        /* Boot from network device */
        if ( ( rc = ipxe ( netdev ) ) != 0 )
                goto err_ipxe;

        /* Reset console */
        console_reset();

 err_ipxe:
        efi_watchdog_stop();
        efi_snp_release();
        return EFIRC ( rc );
}

/** Load file protocol */
static EFI_LOAD_FILE_PROTOCOL efi_snp_load_file_protocol = {
        .LoadFile       = efi_snp_load_file,
};

/******************************************************************************
 *
 * iPXE network driver
 *
 ******************************************************************************
 */

/**
 * Locate SNP device corresponding to network device
 *
 * @v netdev            Network device
 * @ret snp             SNP device, or NULL if not found
 */
static struct efi_snp_device * efi_snp_demux ( struct net_device *netdev ) {
        struct efi_snp_device *snpdev;

        list_for_each_entry ( snpdev, &efi_snp_devices, list ) {
                if ( snpdev->netdev == netdev )
                        return snpdev;
        }
        return NULL;
}

/**
 * Create SNP device
 *
 * @v netdev            Network device
 * @v priv              Private data
 * @ret rc              Return status code
 */
static int efi_snp_probe ( struct net_device *netdev, void *priv __unused ) {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        struct efi_device *efidev;
        struct efi_snp_device *snpdev;
        unsigned int ifcnt;
        void *interface;
        unsigned int tci;
        char vlan_name[ 12 /* ", VLAN xxxx" + NUL */ ];
        int leak = 0;
        EFI_STATUS efirc;
        int rc;

        /* Allocate the SNP device */
        snpdev = zalloc ( sizeof ( *snpdev ) );
        if ( ! snpdev ) {
                rc = -ENOMEM;
                goto err_alloc_snp;
        }
        snpdev->netdev = netdev_get ( netdev );
        INIT_LIST_HEAD ( &snpdev->rx );

        /* Find parent EFI device, if any */
        efidev = efidev_parent ( netdev->dev );
        if ( efidev )
                snpdev->parent = efidev->device;

        /* Sanity check */
        if ( netdev->ll_protocol->ll_addr_len > sizeof ( EFI_MAC_ADDRESS ) ) {
                DBGC ( snpdev, "SNPDEV %p cannot support link-layer address "
                       "length %d for %s\n", snpdev,
                       netdev->ll_protocol->ll_addr_len, netdev->name );
                rc = -ENOTSUP;
                goto err_ll_addr_len;
        }

        /* Populate the SNP structure */
        memcpy ( &snpdev->snp, &efi_snp_device_snp, sizeof ( snpdev->snp ) );
        snpdev->snp.Mode = &snpdev->mode;
        if ( ( efirc = bs->CreateEvent ( EVT_NOTIFY_WAIT, TPL_NOTIFY,
                                         efi_snp_wait_for_packet, snpdev,
                                         &snpdev->snp.WaitForPacket ) ) != 0 ){
                rc = -EEFI ( efirc );
                DBGC ( snpdev, "SNPDEV %p could not create event: %s\n",
                       snpdev, strerror ( rc ) );
                goto err_create_event;
        }

        /* Populate the SNP mode structure */
        snpdev->mode.State = EfiSimpleNetworkStopped;
        efi_snp_set_mode ( snpdev );

        /* Populate the NII structure */
        memcpy ( &snpdev->nii, &efi_snp_device_nii, sizeof ( snpdev->nii ) );
        snpdev->nii.Id = ( ( intptr_t ) &efi_snp_undi );
        snpdev->nii.IfNum = efi_undi_ifnum ( snpdev );
        efi_snp_undi.EntryPoint = ( ( intptr_t ) efi_undi_issue );
        ifcnt = ( ( efi_snp_undi.IFcntExt << 8 ) | efi_snp_undi.IFcnt );
        if ( ifcnt < snpdev->nii.IfNum )
                ifcnt = snpdev->nii.IfNum;
        efi_snp_undi.IFcnt = ( ifcnt & 0xff );
        efi_snp_undi.IFcntExt = ( ifcnt >> 8 );
        efi_snp_undi.Fudge -= efi_undi_checksum ( &efi_snp_undi,
                                                  sizeof ( efi_snp_undi ) );

        /* Populate the VLAN configuration protocol */
        memcpy ( &snpdev->vcfg, &efi_vlan, sizeof ( snpdev->vcfg ) );

        /* Populate the component name structure */
        efi_snprintf ( snpdev->driver_name,
                       ( sizeof ( snpdev->driver_name ) /
                         sizeof ( snpdev->driver_name[0] ) ),
                       "%s %s", product_short_name, netdev->dev->driver_name );
        tci = vlan_tci ( netdev );
        if ( tci ) {
                snprintf ( vlan_name, sizeof ( vlan_name ), ", VLAN %d",
                           VLAN_TAG ( tci ) );
        } else {
                vlan_name[0] = '\0';
        }
        efi_snprintf ( snpdev->controller_name,
                       ( sizeof ( snpdev->controller_name ) /
                         sizeof ( snpdev->controller_name[0] ) ),
                       "%s %s (%s, %s%s)", product_short_name,
                       netdev->dev->driver_name, netdev->dev->name,
                       netdev_addr ( netdev ), vlan_name );
        snpdev->name2.GetDriverName = efi_snp_get_driver_name;
        snpdev->name2.GetControllerName = efi_snp_get_controller_name;
        snpdev->name2.SupportedLanguages = "en";

        /* Populate the load file protocol structure */
        memcpy ( &snpdev->load_file, &efi_snp_load_file_protocol,
                 sizeof ( snpdev->load_file ) );

        /* Populate the device name */
        efi_snprintf ( snpdev->name, ( sizeof ( snpdev->name ) /
                                       sizeof ( snpdev->name[0] ) ),
                       "%s", netdev->name );

        /* Construct device path */
        snpdev->path = efi_netdev_path ( netdev );
        if ( ! snpdev->path ) {
                rc = -ENOMEM;
                goto err_path;
        }

        /* Install the SNP */
        if ( ( efirc = bs->InstallMultipleProtocolInterfaces (
                        &snpdev->handle,
                        &efi_simple_network_protocol_guid, &snpdev->snp,
                        &efi_device_path_protocol_guid, snpdev->path,
                        &efi_nii_protocol_guid, &snpdev->nii,
                        &efi_nii31_protocol_guid, &snpdev->nii,
                        &efi_vlan_config_protocol_guid, &snpdev->vcfg,
                        &efi_component_name2_protocol_guid, &snpdev->name2,
                        &efi_load_file_protocol_guid, &snpdev->load_file,
                        NULL ) ) != 0 ) {
                rc = -EEFI ( efirc );
                DBGC ( snpdev, "SNPDEV %p could not install protocols: %s\n",
                       snpdev, strerror ( rc ) );
                goto err_install_protocol_interface;
        }

        /* SnpDxe will repeatedly start up and shut down our NII/UNDI
         * interface (in order to obtain the MAC address) before
         * discovering that it cannot install another SNP on the same
         * handle.  This causes the underlying network device to be
         * unexpectedly closed.
         *
         * Prevent this by opening our own NII (and NII31) protocol
         * instances to prevent SnpDxe from attempting to bind to
         * them.
         */
        if ( ( rc = efi_open_by_driver ( snpdev->handle,
                                         &efi_nii_protocol_guid,
                                         &interface ) ) != 0 ) {
                DBGC ( snpdev, "SNPDEV %p could not open NII protocol: %s\n",
                       snpdev, strerror ( rc ) );
                goto err_open_nii;
        }
        if ( ( rc = efi_open_by_driver ( snpdev->handle,
                                         &efi_nii31_protocol_guid,
                                         &interface ) ) != 0 ) {
                DBGC ( snpdev, "SNPDEV %p could not open NII31 protocol: %s\n",
                       snpdev, strerror ( rc ) );
                goto err_open_nii31;
        }

        /* Add as child of EFI parent device, if applicable */
        if ( snpdev->parent &&
             ( ( rc = efi_child_add ( snpdev->parent,
                                      snpdev->handle ) ) != 0 ) ) {
                DBGC ( snpdev, "SNPDEV %p could not become child of %s: %s\n",
                       snpdev, efi_handle_name ( efidev->device ),
                       strerror ( rc ) );
                goto err_efi_child_add;
        }

        /* Install HII */
        if ( ( rc = efi_snp_hii_install ( snpdev ) ) != 0 ) {
                DBGC ( snpdev, "SNPDEV %p could not install HII: %s\n",
                       snpdev, strerror ( rc ) );
                /* HII fails on several platforms.  It's
                 * non-essential, so treat this as a non-fatal
                 * error.
                 */
        }

        /* Add to list of SNP devices */
        list_add ( &snpdev->list, &efi_snp_devices );

        DBGC ( snpdev, "SNPDEV %p installed for %s as device %s\n",
               snpdev, netdev->name, efi_handle_name ( snpdev->handle ) );
        return 0;

        list_del ( &snpdev->list );
        if ( snpdev->package_list )
                leak |= efi_snp_hii_uninstall ( snpdev );
        if ( snpdev->parent )
                efi_child_del ( snpdev->parent, snpdev->handle );
 err_efi_child_add:
        efi_close_by_driver ( snpdev->handle, &efi_nii31_protocol_guid );
 err_open_nii31:
        efi_close_by_driver ( snpdev->handle, &efi_nii_protocol_guid );
 err_open_nii:
        if ( ( efirc = bs->UninstallMultipleProtocolInterfaces (
                        snpdev->handle,
                        &efi_simple_network_protocol_guid, &snpdev->snp,
                        &efi_device_path_protocol_guid, snpdev->path,
                        &efi_nii_protocol_guid, &snpdev->nii,
                        &efi_nii31_protocol_guid, &snpdev->nii,
                        &efi_vlan_config_protocol_guid, &snpdev->vcfg,
                        &efi_component_name2_protocol_guid, &snpdev->name2,
                        &efi_load_file_protocol_guid, &snpdev->load_file,
                        NULL ) ) != 0 ) {
                DBGC ( snpdev, "SNPDEV %p could not uninstall: %s\n",
                       snpdev, strerror ( -EEFI ( efirc ) ) );
                leak = 1;
        }
        efi_nullify_snp ( &snpdev->snp );
        efi_nullify_nii ( &snpdev->nii );
        efi_nullify_vlan ( &snpdev->vcfg );
        efi_nullify_name2 ( &snpdev->name2 );
        efi_nullify_load_file ( &snpdev->load_file );
 err_install_protocol_interface:
        if ( ! leak )
                free ( snpdev->path );
 err_path:
        bs->CloseEvent ( snpdev->snp.WaitForPacket );
 err_create_event:
 err_ll_addr_len:
        if ( ! leak ) {
                netdev_put ( netdev );
                free ( snpdev );
        }
 err_alloc_snp:
        if ( leak )
                DBGC ( snpdev, "SNPDEV %p nullified and leaked\n", snpdev );
        return rc;
}

/**
 * Handle SNP device or link state change
 *
 * @v netdev            Network device
 * @v priv              Private data
 */
static void efi_snp_notify ( struct net_device *netdev, void *priv __unused ) {
        struct efi_snp_device *snpdev;

        /* Locate SNP device */
        snpdev = efi_snp_demux ( netdev );
        if ( ! snpdev ) {
                DBG ( "SNP skipping non-SNP device %s\n", netdev->name );
                return;
        }

        /* Update link state */
        snpdev->mode.MediaPresent =
                ( netdev_link_ok ( netdev ) ? TRUE : FALSE );
        DBGC ( snpdev, "SNPDEV %p link is %s\n", snpdev,
               ( snpdev->mode.MediaPresent ? "up" : "down" ) );

        /* Update mode state */
        efi_snp_set_state ( snpdev );
}

/**
 * Destroy SNP device
 *
 * @v netdev            Network device
 * @v priv              Private data
 */
static void efi_snp_remove ( struct net_device *netdev, void *priv __unused ) {
        EFI_BOOT_SERVICES *bs = efi_systab->BootServices;
        struct efi_snp_device *snpdev;
        int leak = efi_shutdown_in_progress;
        EFI_STATUS efirc;

        /* Locate SNP device */
        snpdev = efi_snp_demux ( netdev );
        if ( ! snpdev ) {
                DBG ( "SNP skipping non-SNP device %s\n", netdev->name );
                return;
        }

        /* Uninstall the SNP */
        list_del ( &snpdev->list );
        if ( snpdev->package_list )
                leak |= efi_snp_hii_uninstall ( snpdev );
        if ( snpdev->parent )
                efi_child_del ( snpdev->parent, snpdev->handle );
        efi_close_by_driver ( snpdev->handle, &efi_nii_protocol_guid );
        efi_close_by_driver ( snpdev->handle, &efi_nii31_protocol_guid );
        if ( ( ! efi_shutdown_in_progress ) &&
             ( ( efirc = bs->UninstallMultipleProtocolInterfaces (
                        snpdev->handle,
                        &efi_simple_network_protocol_guid, &snpdev->snp,
                        &efi_device_path_protocol_guid, snpdev->path,
                        &efi_nii_protocol_guid, &snpdev->nii,
                        &efi_nii31_protocol_guid, &snpdev->nii,
                        &efi_vlan_config_protocol_guid, &snpdev->vcfg,
                        &efi_component_name2_protocol_guid, &snpdev->name2,
                        &efi_load_file_protocol_guid, &snpdev->load_file,
                        NULL ) ) != 0 ) ) {
                DBGC ( snpdev, "SNPDEV %p could not uninstall: %s\n",
                       snpdev, strerror ( -EEFI ( efirc ) ) );
                leak = 1;
        }
        efi_nullify_snp ( &snpdev->snp );
        efi_nullify_nii ( &snpdev->nii );
        efi_nullify_vlan ( &snpdev->vcfg );
        efi_nullify_name2 ( &snpdev->name2 );
        efi_nullify_load_file ( &snpdev->load_file );
        if ( ! leak )
                free ( snpdev->path );
        bs->CloseEvent ( snpdev->snp.WaitForPacket );
        if ( ! leak ) {
                netdev_put ( snpdev->netdev );
                free ( snpdev );
        }

        /* Report leakage, if applicable */
        if ( leak && ( ! efi_shutdown_in_progress ) )
                DBGC ( snpdev, "SNPDEV %p nullified and leaked\n", snpdev );
}

/** SNP driver */
struct net_driver efi_snp_driver __net_driver = {
        .name = "SNP",
        .probe = efi_snp_probe,
        .notify = efi_snp_notify,
        .remove = efi_snp_remove,
};

/**
 * Find SNP device by EFI device handle
 *
 * @v handle            EFI device handle
 * @ret snpdev          SNP device, or NULL
 */
struct efi_snp_device * find_snpdev ( EFI_HANDLE handle ) {
        struct efi_snp_device *snpdev;

        list_for_each_entry ( snpdev, &efi_snp_devices, list ) {
                if ( snpdev->handle == handle )
                        return snpdev;
        }
        return NULL;
}

/**
 * Get most recently opened SNP device
 *
 * @ret snpdev          Most recently opened SNP device, or NULL
 */
struct efi_snp_device * last_opened_snpdev ( void ) {
        struct net_device *netdev;

        netdev = last_opened_netdev();
        if ( ! netdev )
                return NULL;

        return efi_snp_demux ( netdev );
}

/**
 * Add to SNP claimed/released count
 *
 * @v delta             Claim count change
 */
void efi_snp_add_claim ( int delta ) {
        struct efi_snp_device *snpdev;

        /* Raise TPL if we are about to claim devices */
        if ( ! efi_snp_claimed )
                efi_raise_tpl ( &efi_snp_saved_tpl );

        /* Claim SNP devices */
        efi_snp_claimed += delta;
        assert ( efi_snp_claimed >= 0 );

        /* Update SNP mode state for each interface */
        list_for_each_entry ( snpdev, &efi_snp_devices, list )
                efi_snp_set_state ( snpdev );

        /* Restore TPL if we have released devices */
        if ( ! efi_snp_claimed )
                efi_restore_tpl ( &efi_snp_saved_tpl );
}