rndis.c

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/*
 * 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.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

/** @file
 *
 * Remote Network Driver Interface Specification
 *
 */

#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <byteswap.h>
#include <ipxe/iobuf.h>
#include <ipxe/netdevice.h>
#include <ipxe/ethernet.h>
#include <ipxe/device.h>
#include <ipxe/rndis.h>

/**
 * Allocate I/O buffer
 *
 * @v len               Length
 * @ret iobuf           I/O buffer, or NULL
 */
static struct io_buffer * rndis_alloc_iob ( size_t len ) {
        struct rndis_header *header;
        struct io_buffer *iobuf;

        /* Allocate I/O buffer and reserve space */
        iobuf = alloc_iob ( sizeof ( *header ) + len );
        if ( iobuf )
                iob_reserve ( iobuf, sizeof ( *header ) );

        return iobuf;
}

/**
 * Wait for completion
 *
 * @v rndis             RNDIS device
 * @v wait_id           Request ID
 * @ret rc              Return status code
 */
static int rndis_wait ( struct rndis_device *rndis, unsigned int wait_id ) {
        unsigned int i;

        /* Record query ID */
        rndis->wait_id = wait_id;

        /* Wait for operation to complete */
        for ( i = 0 ; i < RNDIS_MAX_WAIT_MS ; i++ ) {

                /* Check for completion */
                if ( ! rndis->wait_id )
                        return rndis->wait_rc;

                /* Poll RNDIS device */
                rndis->op->poll ( rndis );

                /* Delay for 1ms */
                mdelay ( 1 );
        }

        DBGC ( rndis, "RNDIS %s timed out waiting for ID %#08x\n",
               rndis->name, wait_id );
        return -ETIMEDOUT;
}

/**
 * Transmit message
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 * @v type              Message type
 * @ret rc              Return status code
 */
static int rndis_tx_message ( struct rndis_device *rndis,
                              struct io_buffer *iobuf, unsigned int type ) {
        struct rndis_header *header;
        int rc;

        /* Prepend RNDIS header */
        header = iob_push ( iobuf, sizeof ( *header ) );
        header->type = cpu_to_le32 ( type );
        header->len = cpu_to_le32 ( iob_len ( iobuf ) );

        /* Transmit message */
        if ( ( rc = rndis->op->transmit ( rndis, iobuf ) ) != 0 ) {
                DBGC ( rndis, "RNDIS %s could not transmit: %s\n",
                       rndis->name, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Complete message transmission
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 * @v rc                Packet status code
 */
void rndis_tx_complete_err ( struct rndis_device *rndis,
                             struct io_buffer *iobuf, int rc ) {
        struct net_device *netdev = rndis->netdev;
        struct rndis_header *header;
        size_t len = iob_len ( iobuf );

        /* Sanity check */
        if ( len < sizeof ( *header ) ) {
                DBGC ( rndis, "RNDIS %s completed underlength transmission:\n",
                       rndis->name );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                netdev_tx_err ( netdev, NULL, -EINVAL );
                return;
        }
        header = iobuf->data;

        /* Complete buffer */
        if ( header->type == cpu_to_le32 ( RNDIS_PACKET_MSG ) ) {
                netdev_tx_complete_err ( netdev, iobuf, rc );
        } else {
                free_iob ( iobuf );
        }
}

/**
 * Transmit data packet
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 * @ret rc              Return status code
 */
static int rndis_tx_data ( struct rndis_device *rndis,
                           struct io_buffer *iobuf ) {
        struct rndis_packet_message *msg;
        size_t len = iob_len ( iobuf );
        int rc;

        /* Prepend packet message header */
        msg = iob_push ( iobuf, sizeof ( *msg ) );
        memset ( msg, 0, sizeof ( *msg ) );
        msg->data.offset = cpu_to_le32 ( sizeof ( *msg ) );
        msg->data.len = cpu_to_le32 ( len );

        /* Transmit message */
        if ( ( rc = rndis_tx_message ( rndis, iobuf, RNDIS_PACKET_MSG ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Defer transmitted packet
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 * @ret rc              Return status code
 *
 * As with netdev_tx_defer(), the caller must ensure that space in the
 * transmit descriptor ring is freed up before calling
 * rndis_tx_complete().
 *
 * Unlike netdev_tx_defer(), this call may fail.
 */
int rndis_tx_defer ( struct rndis_device *rndis, struct io_buffer *iobuf ) {
        struct net_device *netdev = rndis->netdev;
        struct rndis_header *header;
        struct rndis_packet_message *msg;

        /* Fail unless this was a packet message.  Only packet
         * messages correspond to I/O buffers in the network device's
         * TX queue; other messages cannot be deferred in this way.
         */
        assert ( iob_len ( iobuf ) >= sizeof ( *header ) );
        header = iobuf->data;
        if ( header->type != cpu_to_le32 ( RNDIS_PACKET_MSG ) )
                return -ENOTSUP;

        /* Strip RNDIS header and packet message header, to return
         * this packet to the state in which we received it.
         */
        iob_pull ( iobuf, ( sizeof ( *header ) + sizeof ( *msg ) ) );

        /* Defer packet */
        netdev_tx_defer ( netdev, iobuf );

        return 0;
}

/**
 * Receive data packet
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 */
static void rndis_rx_data ( struct rndis_device *rndis,
                            struct io_buffer *iobuf ) {
        struct net_device *netdev = rndis->netdev;
        struct rndis_packet_message *msg;
        size_t len = iob_len ( iobuf );
        size_t data_offset;
        size_t data_len;
        int rc;

        /* Sanity check */
        if ( len < sizeof ( *msg ) ) {
                DBGC ( rndis, "RNDIS %s received underlength data packet:\n",
                       rndis->name );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -EINVAL;
                goto err_len;
        }
        msg = iobuf->data;

        /* Locate and sanity check data buffer */
        data_offset = le32_to_cpu ( msg->data.offset );
        data_len = le32_to_cpu ( msg->data.len );
        if ( ( data_offset > len ) || ( data_len > ( len - data_offset ) ) ) {
                DBGC ( rndis, "RNDIS %s data packet data exceeds packet:\n",
                       rndis->name );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -EINVAL;
                goto err_data;
        }

        /* Strip non-data portions */
        iob_pull ( iobuf, data_offset );
        iob_unput ( iobuf, ( iob_len ( iobuf ) - data_len ) );

        /* Hand off to network stack */
        netdev_rx ( netdev, iob_disown ( iobuf ) );

        return;

 err_data:
 err_len:
        /* Report error to network stack */
        netdev_rx_err ( netdev, iob_disown ( iobuf ), rc );
}

/**
 * Transmit initialisation message
 *
 * @v rndis             RNDIS device
 * @v id                Request ID
 * @ret rc              Return status code
 */
static int rndis_tx_initialise ( struct rndis_device *rndis, unsigned int id ) {
        struct io_buffer *iobuf;
        struct rndis_initialise_message *msg;
        int rc;

        /* Allocate I/O buffer */
        iobuf = rndis_alloc_iob ( sizeof ( *msg ) );
        if ( ! iobuf ) {
                rc = -ENOMEM;
                goto err_alloc;
        }

        /* Construct message */
        msg = iob_put ( iobuf, sizeof ( *msg ) );
        memset ( msg, 0, sizeof ( *msg ) );
        msg->id = id; /* Non-endian */
        msg->major = cpu_to_le32 ( RNDIS_VERSION_MAJOR );
        msg->minor = cpu_to_le32 ( RNDIS_VERSION_MINOR );
        msg->mtu = cpu_to_le32 ( RNDIS_MTU );

        /* Transmit message */
        if ( ( rc = rndis_tx_message ( rndis, iobuf,
                                       RNDIS_INITIALISE_MSG ) ) != 0 )
                goto err_tx;

        return 0;

 err_tx:
        free_iob ( iobuf );
 err_alloc:
        return rc;
}

/**
 * Receive initialisation completion
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 */
static void rndis_rx_initialise ( struct rndis_device *rndis,
                                  struct io_buffer *iobuf ) {
        struct rndis_initialise_completion *cmplt;
        size_t len = iob_len ( iobuf );
        unsigned int id;
        int rc;

        /* Sanity check */
        if ( len < sizeof ( *cmplt ) ) {
                DBGC ( rndis, "RNDIS %s received underlength initialisation "
                       "completion:\n", rndis->name );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -EINVAL;
                goto err_len;
        }
        cmplt = iobuf->data;

        /* Extract request ID */
        id = cmplt->id; /* Non-endian */

        /* Check status */
        if ( cmplt->status ) {
                DBGC ( rndis, "RNDIS %s received initialisation completion "
                       "failure %#08x\n", rndis->name,
                       le32_to_cpu ( cmplt->status ) );
                rc = -EIO;
                goto err_status;
        }

        /* Success */
        rc = 0;

 err_status:
        /* Record completion result if applicable */
        if ( id == rndis->wait_id ) {
                rndis->wait_id = 0;
                rndis->wait_rc = rc;
        }
 err_len:
        free_iob ( iobuf );
}

/**
 * Initialise RNDIS
 *
 * @v rndis             RNDIS device
 * @ret rc              Return status code
 */
static int rndis_initialise ( struct rndis_device *rndis ) {
        int rc;

        /* Transmit initialisation message */
        if ( ( rc = rndis_tx_initialise ( rndis, RNDIS_INIT_ID ) ) != 0 )
                return rc;

        /* Wait for response */
        if ( ( rc = rndis_wait ( rndis, RNDIS_INIT_ID ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Transmit halt message
 *
 * @v rndis             RNDIS device
 * @ret rc              Return status code
 */
static int rndis_tx_halt ( struct rndis_device *rndis ) {
        struct io_buffer *iobuf;
        struct rndis_halt_message *msg;
        int rc;

        /* Allocate I/O buffer */
        iobuf = rndis_alloc_iob ( sizeof ( *msg ) );
        if ( ! iobuf ) {
                rc = -ENOMEM;
                goto err_alloc;
        }

        /* Construct message */
        msg = iob_put ( iobuf, sizeof ( *msg ) );
        memset ( msg, 0, sizeof ( *msg ) );

        /* Transmit message */
        if ( ( rc = rndis_tx_message ( rndis, iobuf, RNDIS_HALT_MSG ) ) != 0 )
                goto err_tx;

        return 0;

 err_tx:
        free_iob ( iobuf );
 err_alloc:
        return rc;
}

/**
 * Halt RNDIS
 *
 * @v rndis             RNDIS device
 * @ret rc              Return status code
 */
static int rndis_halt ( struct rndis_device *rndis ) {
        int rc;

        /* Transmit halt message */
        if ( ( rc = rndis_tx_halt ( rndis ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Transmit OID message
 *
 * @v rndis             RNDIS device
 * @v oid               Object ID
 * @v data              New OID value (or NULL to query current value)
 * @v len               Length of new OID value
 * @ret rc              Return status code
 */
static int rndis_tx_oid ( struct rndis_device *rndis, unsigned int oid,
                          const void *data, size_t len ) {
        struct io_buffer *iobuf;
        struct rndis_oid_message *msg;
        unsigned int type;
        int rc;

        /* Allocate I/O buffer */
        iobuf = rndis_alloc_iob ( sizeof ( *msg ) + len );
        if ( ! iobuf ) {
                rc = -ENOMEM;
                goto err_alloc;
        }

        /* Construct message.  We use the OID as the request ID. */
        msg = iob_put ( iobuf, sizeof ( *msg ) );
        memset ( msg, 0, sizeof ( *msg ) );
        msg->id = oid; /* Non-endian */
        msg->oid = cpu_to_le32 ( oid );
        msg->offset = cpu_to_le32 ( sizeof ( *msg ) );
        msg->len = cpu_to_le32 ( len );
        memcpy ( iob_put ( iobuf, len ), data, len );

        /* Transmit message */
        type = ( data ? RNDIS_SET_MSG : RNDIS_QUERY_MSG );
        if ( ( rc = rndis_tx_message ( rndis, iobuf, type ) ) != 0 )
                goto err_tx;

        return 0;

 err_tx:
        free_iob ( iobuf );
 err_alloc:
        return rc;
}

/**
 * Receive query OID completion
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 */
static void rndis_rx_query_oid ( struct rndis_device *rndis,
                                 struct io_buffer *iobuf ) {
        struct net_device *netdev = rndis->netdev;
        struct rndis_query_completion *cmplt;
        size_t len = iob_len ( iobuf );
        size_t info_offset;
        size_t info_len;
        unsigned int id;
        void *info;
        uint32_t *link_status;
        int rc;

        /* Sanity check */
        if ( len < sizeof ( *cmplt ) ) {
                DBGC ( rndis, "RNDIS %s received underlength query "
                       "completion:\n", rndis->name );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -EINVAL;
                goto err_len;
        }
        cmplt = iobuf->data;

        /* Extract request ID */
        id = cmplt->id; /* Non-endian */

        /* Check status */
        if ( cmplt->status ) {
                DBGC ( rndis, "RNDIS %s received query completion failure "
                       "%#08x\n", rndis->name, le32_to_cpu ( cmplt->status ) );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -EIO;
                goto err_status;
        }

        /* Locate and sanity check information buffer */
        info_offset = le32_to_cpu ( cmplt->offset );
        info_len = le32_to_cpu ( cmplt->len );
        if ( ( info_offset > len ) || ( info_len > ( len - info_offset ) ) ) {
                DBGC ( rndis, "RNDIS %s query completion information exceeds "
                       "packet:\n", rndis->name );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -EINVAL;
                goto err_info;
        }
        info = ( ( ( void * ) cmplt ) + info_offset );

        /* Handle OID */
        switch ( id ) {

        case RNDIS_OID_802_3_PERMANENT_ADDRESS:
                if ( info_len > sizeof ( netdev->hw_addr ) )
                        info_len = sizeof ( netdev->hw_addr );
                memcpy ( netdev->hw_addr, info, info_len );
                break;

        case RNDIS_OID_802_3_CURRENT_ADDRESS:
                if ( info_len > sizeof ( netdev->ll_addr ) )
                        info_len = sizeof ( netdev->ll_addr );
                memcpy ( netdev->ll_addr, info, info_len );
                break;

        case RNDIS_OID_GEN_MEDIA_CONNECT_STATUS:
                if ( info_len != sizeof ( *link_status ) ) {
                        DBGC ( rndis, "RNDIS %s invalid link status:\n",
                               rndis->name );
                        DBGC_HDA ( rndis, 0, iobuf->data, len );
                        rc = -EPROTO;
                        goto err_link_status;
                }
                link_status = info;
                if ( *link_status == 0 ) {
                        DBGC ( rndis, "RNDIS %s link is up\n", rndis->name );
                        netdev_link_up ( netdev );
                } else {
                        DBGC ( rndis, "RNDIS %s link is down: %#08x\n",
                               rndis->name, le32_to_cpu ( *link_status ) );
                        netdev_link_down ( netdev );
                }
                break;

        default:
                DBGC ( rndis, "RNDIS %s unexpected query completion ID %#08x\n",
                       rndis->name, id );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -EPROTO;
                goto err_id;
        }

        /* Success */
        rc = 0;

 err_id:
 err_link_status:
 err_info:
 err_status:
        /* Record completion result if applicable */
        if ( id == rndis->wait_id ) {
                rndis->wait_id = 0;
                rndis->wait_rc = rc;
        }
 err_len:
        /* Free I/O buffer */
        free_iob ( iobuf );
}

/**
 * Receive set OID completion
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 */
static void rndis_rx_set_oid ( struct rndis_device *rndis,
                               struct io_buffer *iobuf ) {
        struct rndis_set_completion *cmplt;
        size_t len = iob_len ( iobuf );
        unsigned int id;
        int rc;

        /* Sanity check */
        if ( len < sizeof ( *cmplt ) ) {
                DBGC ( rndis, "RNDIS %s received underlength set completion:\n",
                       rndis->name );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -EINVAL;
                goto err_len;
        }
        cmplt = iobuf->data;

        /* Extract request ID */
        id = cmplt->id; /* Non-endian */

        /* Check status */
        if ( cmplt->status ) {
                DBGC ( rndis, "RNDIS %s received set completion failure "
                       "%#08x\n", rndis->name, le32_to_cpu ( cmplt->status ) );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -EIO;
                goto err_status;
        }

        /* Success */
        rc = 0;

 err_status:
        /* Record completion result if applicable */
        if ( id == rndis->wait_id ) {
                rndis->wait_id = 0;
                rndis->wait_rc = rc;
        }
 err_len:
        /* Free I/O buffer */
        free_iob ( iobuf );
}

/**
 * Query or set OID
 *
 * @v rndis             RNDIS device
 * @v oid               Object ID
 * @v data              New OID value (or NULL to query current value)
 * @v len               Length of new OID value
 * @ret rc              Return status code
 */
static int rndis_oid ( struct rndis_device *rndis, unsigned int oid,
                       const void *data, size_t len ) {
        int rc;

        /* Transmit query */
        if ( ( rc = rndis_tx_oid ( rndis, oid, data, len ) ) != 0 )
                return rc;

        /* Wait for response */
        if ( ( rc = rndis_wait ( rndis, oid ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Describe RNDIS device
 *
 * @v rndis             RNDIS device
 * @ret rc              Return status code
 */
static int rndis_describe ( struct rndis_device *rndis ) {
        struct net_device *netdev = rndis->netdev;
        int rc;

        /* Assign device name (for debugging) */
        rndis->name = netdev->dev->name;

        /* Open RNDIS device to read MAC addresses */
        if ( ( rc = rndis->op->open ( rndis ) ) != 0 ) {
                DBGC ( rndis, "RNDIS %s could not open: %s\n",
                       rndis->name, strerror ( rc ) );
                goto err_open;
        }

        /* Initialise RNDIS */
        if ( ( rc = rndis_initialise ( rndis ) ) != 0 )
                goto err_initialise;

        /* Query permanent MAC address */
        if ( ( rc = rndis_oid ( rndis, RNDIS_OID_802_3_PERMANENT_ADDRESS,
                                NULL, 0 ) ) != 0 )
                goto err_query_permanent;

        /* Query current MAC address */
        if ( ( rc = rndis_oid ( rndis, RNDIS_OID_802_3_CURRENT_ADDRESS,
                                NULL, 0 ) ) != 0 )
                goto err_query_current;

        /* Get link status */
        if ( ( rc = rndis_oid ( rndis, RNDIS_OID_GEN_MEDIA_CONNECT_STATUS,
                                NULL, 0 ) ) != 0 )
                goto err_query_link;

        /* Halt RNDIS device */
        rndis_halt ( rndis );

        /* Close RNDIS device */
        rndis->op->close ( rndis );

        return 0;

 err_query_link:
 err_query_current:
 err_query_permanent:
        rndis_halt ( rndis );
 err_initialise:
        rndis->op->close ( rndis );
 err_open:
        return rc;
}

/**
 * Receive indicate status message
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 */
static void rndis_rx_status ( struct rndis_device *rndis,
                              struct io_buffer *iobuf ) {
        struct net_device *netdev = rndis->netdev;
        struct rndis_indicate_status_message *msg;
        size_t len = iob_len ( iobuf );
        unsigned int status;
        int rc;

        /* Sanity check */
        if ( len < sizeof ( *msg ) ) {
                DBGC ( rndis, "RNDIS %s received underlength status message:\n",
                       rndis->name );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -EINVAL;
                goto err_len;
        }
        msg = iobuf->data;

        /* Extract status */
        status = le32_to_cpu ( msg->status );

        /* Handle status */
        switch ( msg->status ) {

        case RNDIS_STATUS_MEDIA_CONNECT:
                DBGC ( rndis, "RNDIS %s link is up\n", rndis->name );
                netdev_link_up ( netdev );
                break;

        case RNDIS_STATUS_MEDIA_DISCONNECT:
                DBGC ( rndis, "RNDIS %s link is down\n", rndis->name );
                netdev_link_down ( netdev );
                break;

        case RNDIS_STATUS_WTF_WORLD:
                /* Ignore */
                break;

        default:
                DBGC ( rndis, "RNDIS %s unexpected status %#08x:\n",
                       rndis->name, status );
                DBGC_HDA ( rndis, 0, iobuf->data, len );
                rc = -ENOTSUP;
                goto err_status;
        }

        /* Free I/O buffer */
        free_iob ( iobuf );

        return;

 err_status:
 err_len:
        /* Report error via network device statistics */
        netdev_rx_err ( netdev, iobuf, rc );
}

/**
 * Receive RNDIS message
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 * @v type              Message type
 */
static void rndis_rx_message ( struct rndis_device *rndis,
                               struct io_buffer *iobuf, unsigned int type ) {
        struct net_device *netdev = rndis->netdev;
        int rc;

        /* Handle packet */
        switch ( type ) {

        case RNDIS_PACKET_MSG:
                rndis_rx_data ( rndis, iob_disown ( iobuf ) );
                break;

        case RNDIS_INITIALISE_CMPLT:
                rndis_rx_initialise ( rndis, iob_disown ( iobuf ) );
                break;

        case RNDIS_QUERY_CMPLT:
                rndis_rx_query_oid ( rndis, iob_disown ( iobuf ) );
                break;

        case RNDIS_SET_CMPLT:
                rndis_rx_set_oid ( rndis, iob_disown ( iobuf ) );
                break;

        case RNDIS_INDICATE_STATUS_MSG:
                rndis_rx_status ( rndis, iob_disown ( iobuf ) );
                break;

        default:
                DBGC ( rndis, "RNDIS %s received unexpected type %#08x\n",
                       rndis->name, type );
                DBGC_HDA ( rndis, 0, iobuf->data, iob_len ( iobuf ) );
                rc = -EPROTO;
                goto err_type;
        }

        return;

 err_type:
        /* Report error via network device statistics */
        netdev_rx_err ( netdev, iobuf, rc );
}

/**
 * Receive packet from underlying transport layer
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 */
void rndis_rx ( struct rndis_device *rndis, struct io_buffer *iobuf ) {
        struct net_device *netdev = rndis->netdev;
        struct rndis_header *header;
        unsigned int type;
        int rc;

        /* Sanity check */
        if ( iob_len ( iobuf ) < sizeof ( *header ) ) {
                DBGC ( rndis, "RNDIS %s received underlength packet:\n",
                       rndis->name );
                DBGC_HDA ( rndis, 0, iobuf->data, iob_len ( iobuf ) );
                rc = -EINVAL;
                goto drop;
        }
        header = iobuf->data;

        /* Parse and strip header */
        type = le32_to_cpu ( header->type );
        iob_pull ( iobuf, sizeof ( *header ) );

        /* Handle message */
        rndis_rx_message ( rndis, iob_disown ( iobuf ), type );

        return;

 drop:
        /* Record error */
        netdev_rx_err ( netdev, iob_disown ( iobuf ), rc );
}

/**
 * Discard packet from underlying transport layer
 *
 * @v rndis             RNDIS device
 * @v iobuf             I/O buffer
 * @v rc                Packet status code
 */
void rndis_rx_err ( struct rndis_device *rndis, struct io_buffer *iobuf,
                    int rc ) {
        struct net_device *netdev = rndis->netdev;

        /* Record error */
        netdev_rx_err ( netdev, iob_disown ( iobuf ), rc );
}

/**
 * Set receive filter
 *
 * @v rndis             RNDIS device
 * @v filter            Receive filter
 * @ret rc              Return status code
 */
static int rndis_filter ( struct rndis_device *rndis, unsigned int filter ) {
        uint32_t value = cpu_to_le32 ( filter );
        int rc;

        /* Set receive filter */
        if ( ( rc = rndis_oid ( rndis, RNDIS_OID_GEN_CURRENT_PACKET_FILTER,
                                &value, sizeof ( value ) ) ) != 0 ) {
                DBGC ( rndis, "RNDIS %s could not set receive filter to %#08x: "
                       "%s\n", rndis->name, filter, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Open network device
 *
 * @v netdev            Network device
 * @ret rc              Return status code
 */
static int rndis_open ( struct net_device *netdev ) {
        struct rndis_device *rndis = netdev->priv;
        int rc;

        /* Open RNDIS device */
        if ( ( rc = rndis->op->open ( rndis ) ) != 0 ) {
                DBGC ( rndis, "RNDIS %s could not open: %s\n",
                       rndis->name, strerror ( rc ) );
                goto err_open;
        }

        /* Initialise RNDIS */
        if ( ( rc = rndis_initialise ( rndis ) ) != 0 )
                goto err_initialise;

        /* Set receive filter */
        if ( ( rc = rndis_filter ( rndis, ( RNDIS_FILTER_UNICAST |
                                            RNDIS_FILTER_MULTICAST |
                                            RNDIS_FILTER_ALL_MULTICAST |
                                            RNDIS_FILTER_BROADCAST |
                                            RNDIS_FILTER_PROMISCUOUS ) ) ) != 0)
                goto err_set_filter;

        /* Update link status */
        if ( ( rc = rndis_oid ( rndis, RNDIS_OID_GEN_MEDIA_CONNECT_STATUS,
                                NULL, 0 ) ) != 0 )
                goto err_query_link;

        return 0;

 err_query_link:
 err_set_filter:
        rndis_halt ( rndis );
 err_initialise:
        rndis->op->close ( rndis );
 err_open:
        return rc;
}

/**
 * Close network device
 *
 * @v netdev            Network device
 */
static void rndis_close ( struct net_device *netdev ) {
        struct rndis_device *rndis = netdev->priv;

        /* Clear receive filter */
        rndis_filter ( rndis, 0 );

        /* Halt RNDIS device */
        rndis_halt ( rndis );

        /* Close RNDIS device */
        rndis->op->close ( rndis );
}

/**
 * Transmit packet
 *
 * @v netdev            Network device
 * @v iobuf             I/O buffer
 * @ret rc              Return status code
 */
static int rndis_transmit ( struct net_device *netdev,
                            struct io_buffer *iobuf ) {
        struct rndis_device *rndis = netdev->priv;

        /* Transmit data packet */
        return rndis_tx_data ( rndis, iobuf );
}

/**
 * Poll for completed and received packets
 *
 * @v netdev            Network device
 */
static void rndis_poll ( struct net_device *netdev ) {
        struct rndis_device *rndis = netdev->priv;

        /* Poll RNDIS device */
        rndis->op->poll ( rndis );
}

/** Network device operations */
static struct net_device_operations rndis_operations = {
        .open           = rndis_open,
        .close          = rndis_close,
        .transmit       = rndis_transmit,
        .poll           = rndis_poll,
};

/**
 * Allocate RNDIS device
 *
 * @v priv_len          Length of private data
 * @ret rndis           RNDIS device, or NULL on allocation failure
 */
struct rndis_device * alloc_rndis ( size_t priv_len ) {
        struct net_device *netdev;
        struct rndis_device *rndis;

        /* Allocate and initialise structure */
        netdev = alloc_etherdev ( sizeof ( *rndis ) + priv_len );
        if ( ! netdev )
                return NULL;
        netdev_init ( netdev, &rndis_operations );
        rndis = netdev->priv;
        rndis->netdev = netdev;
        rndis->priv = ( ( ( void * ) rndis ) + sizeof ( *rndis ) );

        return rndis;
}

/**
 * Register RNDIS device
 *
 * @v rndis             RNDIS device
 * @ret rc              Return status code
 *
 * Note that this routine will open and use the RNDIS device in order
 * to query the MAC address.  The device must be immediately ready for
 * use prior to registration.
 */
int register_rndis ( struct rndis_device *rndis ) {
        struct net_device *netdev = rndis->netdev;
        int rc;

        /* Describe RNDIS device */
        if ( ( rc = rndis_describe ( rndis ) ) != 0 )
                goto err_describe;

        /* Register network device */
        if ( ( rc = register_netdev ( netdev ) ) != 0 ) {
                DBGC ( rndis, "RNDIS %s could not register: %s\n",
                       rndis->name, strerror ( rc ) );
                goto err_register;
        }

        return 0;

        unregister_netdev ( netdev );
 err_register:
 err_describe:
        return rc;
}

/**
 * Unregister RNDIS device
 *
 * @v rndis             RNDIS device
 */
void unregister_rndis ( struct rndis_device *rndis ) {
        struct net_device *netdev = rndis->netdev;

        /* Unregister network device */
        unregister_netdev ( netdev );
}

/**
 * Free RNDIS device
 *
 * @v rndis             RNDIS device
 */
void free_rndis ( struct rndis_device *rndis ) {
        struct net_device *netdev = rndis->netdev;

        /* Free network device */
        netdev_nullify ( netdev );
        netdev_put ( netdev );
}