fc.c

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/*
 * Copyright (C) 2010 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.
 *
 * 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 );

#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <assert.h>
#include <byteswap.h>
#include <ipxe/refcnt.h>
#include <ipxe/list.h>
#include <ipxe/tables.h>
#include <ipxe/timer.h>
#include <ipxe/retry.h>
#include <ipxe/interface.h>
#include <ipxe/xfer.h>
#include <ipxe/iobuf.h>
#include <ipxe/fc.h>
#include <ipxe/fcels.h>
#include <ipxe/fcns.h>

/** @file
 *
 * Fibre Channel
 *
 */

/** List of Fibre Channel ports */
LIST_HEAD ( fc_ports );

/** List of Fibre Channel peers */
LIST_HEAD ( fc_peers );

/******************************************************************************
 *
 * Well-known addresses
 *
 ******************************************************************************
 */

/** Unassigned port ID */
struct fc_port_id fc_empty_port_id = { .bytes = { 0x00, 0x00, 0x00 } };

/** F_Port contoller port ID */
struct fc_port_id fc_f_port_id = { .bytes = { 0xff, 0xff, 0xfe } };

/** Generic services port ID */
struct fc_port_id fc_gs_port_id = { .bytes = { 0xff, 0xff, 0xfc } };

/** Point-to-point low port ID */
struct fc_port_id fc_ptp_low_port_id = { .bytes = { 0x01, 0x01, 0x01 } };

/** Point-to-point high port ID */
struct fc_port_id fc_ptp_high_port_id = { .bytes = { 0x01, 0x01, 0x02 } };

/******************************************************************************
 *
 * Utility functions
 *
 ******************************************************************************
 */

/**
 * Format Fibre Channel port ID
 *
 * @v id                Fibre Channel port ID
 * @ret id_text         Port ID text
 */
const char * fc_id_ntoa ( const struct fc_port_id *id ) {
        static char id_text[ FC_PORT_ID_STRLEN + 1 /* NUL */ ];

        snprintf ( id_text, sizeof ( id_text ), "%02x.%02x.%02x",
                   id->bytes[0], id->bytes[1], id->bytes[2] );
        return id_text;
}

/**
 * Parse Fibre Channel port ID
 *
 * @v id_text           Port ID text
 * @ret id              Fibre Channel port ID
 * @ret rc              Return status code
 */
int fc_id_aton ( const char *id_text, struct fc_port_id *id ) {
        char *ptr = ( ( char * ) id_text );
        unsigned int i = 0;

        while ( 1 ) {
                id->bytes[i++] = strtoul ( ptr, &ptr, 16 );
                if ( i == sizeof ( id->bytes ) )
                        return ( ( *ptr == '\0' ) ? 0 : -EINVAL );
                if ( *ptr != '.' )
                        return -EINVAL;
                ptr++;
        }
}

/**
 * Format Fibre Channel WWN
 *
 * @v wwn               Fibre Channel WWN
 * @ret wwn_text        WWN text
 */
const char * fc_ntoa ( const struct fc_name *wwn ) {
        static char wwn_text[ FC_NAME_STRLEN + 1 /* NUL */ ];

        snprintf ( wwn_text, sizeof ( wwn_text ),
                   "%02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x",
                   wwn->bytes[0], wwn->bytes[1], wwn->bytes[2], wwn->bytes[3],
                   wwn->bytes[4], wwn->bytes[5], wwn->bytes[6], wwn->bytes[7] );
        return wwn_text;
}

/**
 * Parse Fibre Channel WWN
 *
 * @v wwn_text          WWN text
 * @ret wwn             Fibre Channel WWN
 * @ret rc              Return status code
 */
int fc_aton ( const char *wwn_text, struct fc_name *wwn ) {
        char *ptr = ( ( char * ) wwn_text );
        unsigned int i = 0;

        while ( 1 ) {
                wwn->bytes[i++] = strtoul ( ptr, &ptr, 16 );
                if ( i == sizeof ( wwn->bytes ) )
                        return ( ( *ptr == '\0' ) ? 0 : -EINVAL );
                if ( *ptr != ':' )
                        return -EINVAL;
                ptr++;
        }
}

/**
 * Fill Fibre Channel socket address
 *
 * @v sa_fc             Fibre Channel socket address to fill in
 * @v id                Fibre Channel port ID
 * @ret sa              Socket address
 */
struct sockaddr * fc_fill_sockaddr ( struct sockaddr_fc *sa_fc,
                                     struct fc_port_id *id ) {
        union {
                struct sockaddr sa;
                struct sockaddr_fc fc;
        } *u = container_of ( sa_fc, typeof ( *u ), fc );

        memset ( sa_fc, 0, sizeof ( *sa_fc ) );
        sa_fc->sfc_family = AF_FC;
        memcpy ( &sa_fc->sfc_port_id, id, sizeof ( sa_fc->sfc_port_id ) );
        return &u->sa;
}

/******************************************************************************
 *
 * Fibre Channel link state
 *
 ******************************************************************************
 */

/** Default link status code */
#define EUNKNOWN_LINK_STATUS __einfo_error ( EINFO_EUNKNOWN_LINK_STATUS )
#define EINFO_EUNKNOWN_LINK_STATUS \
        __einfo_uniqify ( EINFO_EINPROGRESS, 0x01, "Unknown" )

/**
 * Mark Fibre Channel link as up
 *
 * @v link              Fibre Channel link state monitor
 */
static void fc_link_up ( struct fc_link_state *link ) {

        /* Stop retry timer */
        stop_timer ( &link->timer );

        /* Record link state */
        link->rc = 0;
}

/**
 * Mark Fibre Channel link as down
 *
 * @v link              Fibre Channel link state monitor
 * @v rc                Link state
 */
static void fc_link_err ( struct fc_link_state *link, int rc ) {

        /* Record link state */
        if ( rc == 0 )
                rc = -EUNKNOWN_LINK_STATUS;
        link->rc = rc;

        /* Schedule another link examination */
        start_timer_fixed ( &link->timer, FC_LINK_RETRY_DELAY );
}

/**
 * Examine Fibre Channel link state
 *
 * @v link              Fibre Channel link state monitor
 */
static void fc_link_examine ( struct fc_link_state *link ) {

        link->examine ( link );
}

/**
 * Handle Fibre Channel link retry timer expiry
 */
static void fc_link_expired ( struct retry_timer *timer, int over __unused ) {
        struct fc_link_state *link =
                container_of ( timer, struct fc_link_state, timer );

        /* Schedule another link examination */
        start_timer_fixed ( &link->timer, FC_LINK_RETRY_DELAY );

        /* Examine link */
        fc_link_examine ( link );
}

/**
 * Initialise Fibre Channel link state monitor
 *
 * @v link              Fibre Channel link state monitor
 * @v examine           Examine link state method
 * @v refcnt            Reference counter
 */
static void fc_link_init ( struct fc_link_state *link,
                           void ( * examine ) ( struct fc_link_state *link ),
                           struct refcnt *refcnt ) {

        link->rc = -EUNKNOWN_LINK_STATUS;
        timer_init ( &link->timer, fc_link_expired, refcnt );
        link->examine = examine;
}

/**
 * Start monitoring Fibre Channel link state
 *
 * @v link              Fibre Channel link state monitor
 */
static void fc_link_start ( struct fc_link_state *link ) {
        start_timer_nodelay ( &link->timer );
}

/**
 * Stop monitoring Fibre Channel link state
 *
 * @v link              Fibre Channel link state monitor
 */
static void fc_link_stop ( struct fc_link_state *link ) {
        stop_timer ( &link->timer );
}

/******************************************************************************
 *
 * Fibre Channel exchanges
 *
 ******************************************************************************
 */

/** A Fibre Channel exchange */
struct fc_exchange {
        /** Reference count */
        struct refcnt refcnt;
        /** Fibre Channel port */
        struct fc_port *port;
        /** List of active exchanges within this port */
        struct list_head list;

        /** Peer port ID */
        struct fc_port_id peer_port_id;
        /** Data structure type */
        unsigned int type;
        /** Flags */
        unsigned int flags;
        /** Local exchange ID */
        uint16_t xchg_id;
        /** Peer exchange ID */
        uint16_t peer_xchg_id;
        /** Active sequence ID */
        uint8_t seq_id;
        /** Active sequence count */
        uint16_t seq_cnt;

        /** Timeout timer */
        struct retry_timer timer;

        /** Upper-layer protocol interface */
        struct interface ulp;
};

/** Fibre Channel exchange flags */
enum fc_exchange_flags {
        /** We are the exchange originator */
        FC_XCHG_ORIGINATOR = 0x0001,
        /** We have the sequence initiative */
        FC_XCHG_SEQ_INITIATIVE = 0x0002,
        /** This is the first sequence of the exchange */
        FC_XCHG_SEQ_FIRST = 0x0004,
};

/** Fibre Channel timeout */
#define FC_TIMEOUT ( 1 * TICKS_PER_SEC )

/**
 * Create local Fibre Channel exchange identifier
 *
 * @ret xchg_id         Local exchange ID
 */
static unsigned int fc_new_xchg_id ( void ) {
        static uint16_t next_id = 0x0000;

        /* We must avoid using FC_RX_ID_UNKNOWN (0xffff) */
        next_id += 2;
        return next_id;
}

/**
 * Create local Fibre Channel sequence identifier
 *
 * @ret seq_id          Local sequence identifier
 */
static unsigned int fc_new_seq_id ( void ) {
        static uint8_t seq_id = 0x00;

        return (++seq_id);
}

/**
 * Free Fibre Channel exchange
 *
 * @v refcnt            Reference count
 */
static void fc_xchg_free ( struct refcnt *refcnt ) {
        struct fc_exchange *xchg =
                container_of ( refcnt, struct fc_exchange, refcnt );

        assert ( ! timer_running ( &xchg->timer ) );
        assert ( list_empty ( &xchg->list ) );

        fc_port_put ( xchg->port );
        free ( xchg );
}

/**
 * Close Fibre Channel exchange
 *
 * @v xchg              Fibre Channel exchange
 * @v rc                Reason for close
 */
static void fc_xchg_close ( struct fc_exchange *xchg, int rc ) {
        struct fc_port *port = xchg->port;

        if ( rc != 0 ) {
                DBGC2 ( port, "FCXCHG %s/%04x closed: %s\n",
                        port->name, xchg->xchg_id, strerror ( rc ) );
        }

        /* Stop timer */
        stop_timer ( &xchg->timer );

        /* If list still holds a reference, remove from list of open
         * exchanges and drop list's reference.
         */
        if ( ! list_empty ( &xchg->list ) ) {
                list_del ( &xchg->list );
                INIT_LIST_HEAD ( &xchg->list );
                ref_put ( &xchg->refcnt );
        }

        /* Shutdown interfaces */
        intf_shutdown ( &xchg->ulp, rc );
}

/**
 * Handle exchange timeout
 *
 * @v timer             Timeout timer
 * @v over              Failure indicator
 */
static void fc_xchg_expired ( struct retry_timer *timer, int over __unused ) {
        struct fc_exchange *xchg =
                container_of ( timer, struct fc_exchange, timer );
        struct fc_port *port = xchg->port;

        DBGC ( port, "FCXCHG %s/%04x timed out\n", port->name, xchg->xchg_id );

        /* Terminate the exchange */
        fc_xchg_close ( xchg, -ETIMEDOUT );
}

/**
 * Check Fibre Channel exchange window
 *
 * @v xchg              Fibre Channel exchange
 * @ret len             Length opf window
 */
static size_t fc_xchg_window ( struct fc_exchange *xchg __unused ) {

        /* We don't currently store the path MTU */
        return FC_LOGIN_DEFAULT_MTU;
}

/**
 * Allocate Fibre Channel I/O buffer
 *
 * @v xchg              Fibre Channel exchange
 * @v len               Payload length
 * @ret iobuf           I/O buffer, or NULL
 */
static struct io_buffer * fc_xchg_alloc_iob ( struct fc_exchange *xchg,
                                              size_t len ) {
        struct fc_port *port = xchg->port;
        struct io_buffer *iobuf;

        iobuf = xfer_alloc_iob ( &port->transport,
                                 ( sizeof ( struct fc_frame_header ) + len ) );
        if ( iobuf ) {
                iob_reserve ( iobuf, sizeof ( struct fc_frame_header ) );
        }
        return iobuf;
}

/**
 * Transmit data as part of a Fibre Channel exchange
 *
 * @v xchg              Fibre Channel exchange
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int fc_xchg_tx ( struct fc_exchange *xchg, struct io_buffer *iobuf,
                        struct xfer_metadata *meta ) {
        struct fc_port *port = xchg->port;
        struct sockaddr_fc *dest = ( ( struct sockaddr_fc * ) meta->dest );
        struct fc_frame_header *fchdr;
        unsigned int r_ctl;
        unsigned int f_ctl_es;
        int rc;

        /* Sanity checks */
        if ( ! ( xchg->flags & FC_XCHG_SEQ_INITIATIVE ) ) {
                DBGC ( port, "FCXCHG %s/%04x cannot transmit while not "
                       "holding sequence initiative\n",
                       port->name, xchg->xchg_id );
                rc = -EBUSY;
                goto done;
        }

        /* Calculate routing control */
        switch ( xchg->type ) {
        case FC_TYPE_ELS:
                r_ctl = FC_R_CTL_ELS;
                if ( meta->flags & XFER_FL_RESPONSE ) {
                        r_ctl |= FC_R_CTL_SOL_CTRL;
                } else {
                        r_ctl |= FC_R_CTL_UNSOL_CTRL;
                }
                break;
        case FC_TYPE_CT:
                r_ctl = FC_R_CTL_DATA;
                if ( meta->flags & XFER_FL_RESPONSE ) {
                        r_ctl |= FC_R_CTL_SOL_CTRL;
                } else {
                        r_ctl |= FC_R_CTL_UNSOL_CTRL;
                }
                break;
        default:
                r_ctl = FC_R_CTL_DATA;
                switch ( meta->flags &
                         ( XFER_FL_CMD_STAT | XFER_FL_RESPONSE ) ) {
                case ( XFER_FL_CMD_STAT | XFER_FL_RESPONSE ):
                        r_ctl |= FC_R_CTL_CMD_STAT;
                        break;
                case ( XFER_FL_CMD_STAT ):
                        r_ctl |= FC_R_CTL_UNSOL_CMD;
                        break;
                case ( XFER_FL_RESPONSE ):
                        r_ctl |= FC_R_CTL_SOL_DATA;
                        break;
                default:
                        r_ctl |= FC_R_CTL_UNSOL_DATA;
                        break;
                }
                break;
        }

        /* Calculate exchange and sequence control */
        f_ctl_es = 0;
        if ( ! ( xchg->flags & FC_XCHG_ORIGINATOR ) )
                f_ctl_es |= FC_F_CTL_ES_RESPONDER;
        if ( xchg->flags & FC_XCHG_SEQ_FIRST )
                f_ctl_es |= FC_F_CTL_ES_FIRST;
        if ( meta->flags & XFER_FL_OUT )
                f_ctl_es |= ( FC_F_CTL_ES_END | FC_F_CTL_ES_LAST );
        if ( meta->flags & XFER_FL_OVER )
                f_ctl_es |= ( FC_F_CTL_ES_END | FC_F_CTL_ES_TRANSFER );

        /* Create frame header */
        fchdr = iob_push ( iobuf, sizeof ( *fchdr ) );
        memset ( fchdr, 0, sizeof ( *fchdr ) );
        fchdr->r_ctl = r_ctl;
        memcpy ( &fchdr->d_id,
                 ( dest ? &dest->sfc_port_id : &xchg->peer_port_id ),
                 sizeof ( fchdr->d_id ) );
        memcpy ( &fchdr->s_id, &port->port_id, sizeof ( fchdr->s_id ) );
        fchdr->type = xchg->type;
        fchdr->f_ctl_es = f_ctl_es;
        fchdr->seq_id = xchg->seq_id;
        fchdr->seq_cnt = htons ( xchg->seq_cnt++ );
        fchdr->ox_id = htons ( ( xchg->flags & FC_XCHG_ORIGINATOR ) ?
                               xchg->xchg_id : xchg->peer_xchg_id );
        fchdr->rx_id = htons ( ( xchg->flags & FC_XCHG_ORIGINATOR ) ?
                               xchg->peer_xchg_id : xchg->xchg_id );
        if ( meta->flags & XFER_FL_ABS_OFFSET ) {
                fchdr->f_ctl_misc |= FC_F_CTL_MISC_REL_OFF;
                fchdr->parameter = htonl ( meta->offset );
        }

        /* Relinquish sequence initiative if applicable */
        if ( meta->flags & XFER_FL_OVER ) {
                xchg->flags &= ~( FC_XCHG_SEQ_INITIATIVE | FC_XCHG_SEQ_FIRST );
                xchg->seq_cnt = 0;
        }

        /* Reset timeout */
        start_timer_fixed ( &xchg->timer, FC_TIMEOUT );

        /* Deliver frame */
        if ( ( rc = xfer_deliver_iob ( &port->transport,
                                       iob_disown ( iobuf ) ) ) != 0 ) {
                DBGC ( port, "FCXCHG %s/%04x cannot transmit: %s\n",
                       port->name, xchg->xchg_id, strerror ( rc ) );
                goto done;
        }

 done:
        free_iob ( iobuf );
        return rc;
}

/** Mapping from Fibre Channel routing control information to xfer metadata */
static const uint8_t fc_r_ctl_info_meta_flags[ FC_R_CTL_INFO_MASK + 1 ] = {
        [FC_R_CTL_UNCAT]        = ( 0 ),
        [FC_R_CTL_SOL_DATA]     = ( XFER_FL_RESPONSE ),
        [FC_R_CTL_UNSOL_CTRL]   = ( XFER_FL_CMD_STAT ),
        [FC_R_CTL_SOL_CTRL]     = ( XFER_FL_CMD_STAT ),
        [FC_R_CTL_UNSOL_DATA]   = ( 0 ),
        [FC_R_CTL_DATA_DESC]    = ( XFER_FL_CMD_STAT ),
        [FC_R_CTL_UNSOL_CMD]    = ( XFER_FL_CMD_STAT ),
        [FC_R_CTL_CMD_STAT]     = ( XFER_FL_CMD_STAT | XFER_FL_RESPONSE ),
};

/**
 * Receive data as part of a Fibre Channel exchange
 *
 * @v xchg              Fibre Channel exchange
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int fc_xchg_rx ( struct fc_exchange *xchg, struct io_buffer *iobuf,
                        struct xfer_metadata *meta __unused ) {
        struct fc_port *port = xchg->port;
        struct fc_frame_header *fchdr = iobuf->data;
        struct xfer_metadata fc_meta;
        struct sockaddr_fc src;
        struct sockaddr_fc dest;
        int rc;

        /* Record peer exchange ID */
        xchg->peer_xchg_id =
                ntohs ( ( fchdr->f_ctl_es & FC_F_CTL_ES_RESPONDER ) ?
                        fchdr->rx_id : fchdr->ox_id );

        /* Sequence checks */
        if ( xchg->flags & FC_XCHG_SEQ_INITIATIVE ) {
                DBGC ( port, "FCXCHG %s/%04x received frame while holding "
                       "sequence initiative\n", port->name, xchg->xchg_id );
                rc = -EBUSY;
                goto done;
        }
        if ( ntohs ( fchdr->seq_cnt ) != xchg->seq_cnt ) {
                DBGC ( port, "FCXCHG %s/%04x received out-of-order frame %d "
                       "(expected %d)\n", port->name, xchg->xchg_id,
                       ntohs ( fchdr->seq_cnt ), xchg->seq_cnt );
                rc = -EPIPE;
                goto done;
        }
        if ( xchg->seq_cnt == 0 )
                xchg->seq_id = fchdr->seq_id;
        xchg->seq_cnt++;
        if ( fchdr->seq_id != xchg->seq_id ) {
                DBGC ( port, "FCXCHG %s/%04x received frame for incorrect "
                       "sequence %02x (expected %02x)\n", port->name,
                       xchg->xchg_id, fchdr->seq_id, xchg->seq_id );
                rc = -EPIPE;
                goto done;
        }

        /* Check for end of sequence and transfer of sequence initiative */
        if ( fchdr->f_ctl_es & FC_F_CTL_ES_END ) {
                xchg->seq_cnt = 0;
                if ( fchdr->f_ctl_es & FC_F_CTL_ES_TRANSFER ) {
                        xchg->flags |= FC_XCHG_SEQ_INITIATIVE;
                        xchg->seq_id = fc_new_seq_id();
                }
        }

        /* Construct metadata */
        memset ( &fc_meta, 0, sizeof ( fc_meta ) );
        fc_meta.flags =
                fc_r_ctl_info_meta_flags[ fchdr->r_ctl & FC_R_CTL_INFO_MASK ];
        if ( fchdr->f_ctl_es & FC_F_CTL_ES_TRANSFER ) {
                fc_meta.flags |= XFER_FL_OVER;
        }
        if ( ( fchdr->f_ctl_es & FC_F_CTL_ES_LAST ) &&
             ( fchdr->f_ctl_es & FC_F_CTL_ES_END ) ) {
                fc_meta.flags |= XFER_FL_OUT;
        }
        if ( fchdr->f_ctl_misc & FC_F_CTL_MISC_REL_OFF ) {
                fc_meta.flags |= XFER_FL_ABS_OFFSET;
                fc_meta.offset = ntohl ( fchdr->parameter );
        }
        fc_meta.src = fc_fill_sockaddr ( &src, &fchdr->s_id );
        fc_meta.dest = fc_fill_sockaddr ( &dest, &fchdr->d_id );

        /* Reset timeout */
        start_timer_fixed ( &xchg->timer, FC_TIMEOUT );

        /* Deliver via exchange's ULP interface */
        iob_pull ( iobuf, sizeof ( *fchdr ) );
        if ( ( rc = xfer_deliver ( &xchg->ulp, iob_disown ( iobuf ),
                                   &fc_meta ) ) != 0 ) {
                DBGC ( port, "FCXCHG %s/%04x cannot deliver frame: %s\n",
                       port->name, xchg->xchg_id, strerror ( rc ) );
                goto done;
        }

        /* Close exchange if applicable */
        if ( ( fchdr->f_ctl_es & FC_F_CTL_ES_LAST ) &&
             ( fchdr->f_ctl_es & FC_F_CTL_ES_END ) ) {
                fc_xchg_close ( xchg, 0 );
        }

 done:
        free_iob ( iobuf );
        return rc;
}

/** Fibre Channel exchange ULP interface operations */
static struct interface_operation fc_xchg_ulp_op[] = {
        INTF_OP ( xfer_deliver, struct fc_exchange *, fc_xchg_tx ),
        INTF_OP ( xfer_alloc_iob, struct fc_exchange *, fc_xchg_alloc_iob ),
        INTF_OP ( xfer_window, struct fc_exchange *, fc_xchg_window ),
        INTF_OP ( intf_close, struct fc_exchange *, fc_xchg_close ),
};

/** Fibre Channel exchange ULP interface descriptor */
static struct interface_descriptor fc_xchg_ulp_desc =
        INTF_DESC ( struct fc_exchange, ulp, fc_xchg_ulp_op );

/**
 * Create new Fibre Channel exchange
 *
 * @v port              Fibre Channel port
 * @v peer_port_id      Peer port ID
 * @ret xchg            Exchange, or NULL
 */
static struct fc_exchange * fc_xchg_create ( struct fc_port *port,
                                             struct fc_port_id *peer_port_id,
                                             unsigned int type ) {
        struct fc_exchange *xchg;

        /* Allocate and initialise structure */
        xchg = zalloc ( sizeof ( *xchg ) );
        if ( ! xchg )
                return NULL;
        ref_init ( &xchg->refcnt, fc_xchg_free );
        intf_init ( &xchg->ulp, &fc_xchg_ulp_desc, &xchg->refcnt );
        timer_init ( &xchg->timer, fc_xchg_expired, &xchg->refcnt );
        xchg->port = fc_port_get ( port );
        memcpy ( &xchg->peer_port_id, peer_port_id,
                 sizeof ( xchg->peer_port_id ) );
        xchg->type = type;
        xchg->xchg_id = fc_new_xchg_id();
        xchg->peer_xchg_id = FC_RX_ID_UNKNOWN;
        xchg->seq_id = fc_new_seq_id();

        /* Transfer reference to list of exchanges and return */
        list_add ( &xchg->list, &port->xchgs );
        return xchg;
}

/**
 * Originate a new Fibre Channel exchange
 *
 * @v parent            Interface to which to attach
 * @v port              Fibre Channel port
 * @v peer_port_id      Peer port ID
 * @ret xchg_id         Exchange ID, or negative error
 */
int fc_xchg_originate ( struct interface *parent, struct fc_port *port,
                        struct fc_port_id *peer_port_id, unsigned int type ) {
        struct fc_exchange *xchg;

        /* Allocate and initialise structure */
        xchg = fc_xchg_create ( port, peer_port_id, type );
        if ( ! xchg )
                return -ENOMEM;
        xchg->flags = ( FC_XCHG_ORIGINATOR | FC_XCHG_SEQ_INITIATIVE |
                        FC_XCHG_SEQ_FIRST );

        DBGC2 ( port, "FCXCHG %s/%04x originating to %s (type %02x)\n",
                port->name, xchg->xchg_id, fc_id_ntoa ( &xchg->peer_port_id ),
                xchg->type );

        /* Attach to parent interface and return */
        intf_plug_plug ( &xchg->ulp, parent );
        return xchg->xchg_id;
}

/**
 * Open a new responder Fibre Channel exchange
 *
 * @v port              Fibre Channel port
 * @v fchdr             Fibre Channel frame header
 * @ret xchg            Fibre Channel exchange, or NULL
 */
static struct fc_exchange * fc_xchg_respond ( struct fc_port *port,
                                              struct fc_frame_header *fchdr ) {
        struct fc_exchange *xchg;
        struct fc_responder *responder;
        unsigned int type = fchdr->type;
        int rc;

        /* Allocate and initialise structure */
        xchg = fc_xchg_create ( port, &fchdr->s_id, type );
        if ( ! xchg )
                return NULL;
        xchg->seq_id = fchdr->seq_id;

        DBGC2 ( port, "FCXCHG %s/%04x responding to %s xchg %04x (type "
                "%02x)\n", port->name, xchg->xchg_id,
                fc_id_ntoa ( &xchg->peer_port_id ),
                ntohs ( fchdr->ox_id ), xchg->type );

        /* Find a responder, if any */
        for_each_table_entry ( responder, FC_RESPONDERS ) {
                if ( responder->type == type ) {
                        if ( ( rc = responder->respond ( &xchg->ulp, port,
                                                         &fchdr->d_id,
                                                         &fchdr->s_id ) ) !=0 ){
                                DBGC ( port, "FCXCHG %s/%04x could not "
                                       "respond: %s\n", port->name,
                                       xchg->xchg_id, strerror ( rc ) );
                        }
                }
                break;
        }

        /* We may or may not have a ULP attached at this point, but
         * the exchange does exist.
         */
        return xchg;
}

/******************************************************************************
 *
 * Fibre Channel ports
 *
 ******************************************************************************
 */

/**
 * Close Fibre Channel port
 *
 * @v port              Fibre Channel port
 * @v rc                Reason for close
 */
static void fc_port_close ( struct fc_port *port, int rc ) {
        struct fc_exchange *xchg;
        struct fc_exchange *tmp;

        DBGC ( port, "FCPORT %s closed\n", port->name );

        /* Log out port, if necessary */
        if ( fc_link_ok ( &port->link ) )
                fc_port_logout ( port, rc );

        /* Stop link monitor */
        fc_link_stop ( &port->link );

        /* Shut down interfaces */
        intf_shutdown ( &port->transport, rc );
        intf_shutdown ( &port->flogi, rc );
        intf_shutdown ( &port->ns_plogi, rc );

        /* Shut down any remaining exchanges */
        list_for_each_entry_safe ( xchg, tmp, &port->xchgs, list )
                fc_xchg_close ( xchg, rc );

        /* Remove from list of ports */
        list_del ( &port->list );
        INIT_LIST_HEAD ( &port->list );
}

/**
 * Identify Fibre Channel exchange by local exchange ID
 *
 * @v port              Fibre Channel port
 * @v xchg_id           Local exchange ID
 * @ret xchg            Fibre Channel exchange, or NULL
 */
static struct fc_exchange * fc_port_demux ( struct fc_port *port,
                                            unsigned int xchg_id ) {
        struct fc_exchange *xchg;

        list_for_each_entry ( xchg, &port->xchgs, list ) {
                if ( xchg->xchg_id == xchg_id )
                        return xchg;
        }
        return NULL;
}

/**
 * Handle received frame from Fibre Channel port
 *
 * @v port              Fibre Channel port
 * @v iobuf             I/O buffer
 * @v meta              Data transfer metadata
 * @ret rc              Return status code
 */
static int fc_port_deliver ( struct fc_port *port, struct io_buffer *iobuf,
                             struct xfer_metadata *meta ) {
        struct fc_frame_header *fchdr = iobuf->data;
        unsigned int xchg_id;
        struct fc_exchange *xchg;
        int rc;

        /* Sanity check */
        if ( iob_len ( iobuf ) < sizeof ( *fchdr ) ) {
                DBGC ( port, "FCPORT %s received underlength frame (%zd "
                       "bytes)\n", port->name, iob_len ( iobuf ) );
                rc = -EINVAL;
                goto err_sanity;
        }

        /* Verify local port ID */
        if ( ( memcmp ( &fchdr->d_id, &port->port_id,
                        sizeof ( fchdr->d_id ) ) != 0 ) &&
             ( memcmp ( &fchdr->d_id, &fc_f_port_id,
                        sizeof ( fchdr->d_id ) ) != 0 ) &&
             ( memcmp ( &port->port_id, &fc_empty_port_id,
                        sizeof ( port->port_id ) ) != 0 ) ) {
                DBGC ( port, "FCPORT %s received frame for incorrect port ID "
                       "%s\n", port->name, fc_id_ntoa ( &fchdr->d_id ) );
                rc = -ENOTCONN;
                goto err_port_id;
        }

        /* Demultiplex amongst active exchanges */
        xchg_id = ntohs ( ( fchdr->f_ctl_es & FC_F_CTL_ES_RESPONDER ) ?
                          fchdr->ox_id : fchdr->rx_id );
        xchg = fc_port_demux ( port, xchg_id );

        /* If we have no active exchange and this frame starts a new
         * exchange, try to create a new responder exchange
         */
        if ( ( fchdr->f_ctl_es & FC_F_CTL_ES_FIRST ) &&
             ( fchdr->seq_cnt == 0 ) ) {

                /* Create new exchange */
                xchg = fc_xchg_respond ( port, fchdr );
                if ( ! xchg ) {
                        DBGC ( port, "FCPORT %s cannot create new exchange\n",
                               port->name );
                        rc = -ENOMEM;
                        goto err_respond;
                }
        }

        /* Fail if no exchange exists */
        if ( ! xchg ) {
                DBGC ( port, "FCPORT %s xchg %04x unknown\n",
                       port->name, xchg_id );
                rc = -ENOTCONN;
                goto err_no_xchg;
        }

        /* Pass received frame to exchange */
        ref_get ( &xchg->refcnt );
        if ( ( rc = fc_xchg_rx ( xchg, iob_disown ( iobuf ), meta ) ) != 0 )
                goto err_xchg_rx;

 err_xchg_rx:
        ref_put ( &xchg->refcnt );
 err_no_xchg:
 err_respond:
 err_port_id:
 err_sanity:
        free_iob ( iobuf );
        return rc;
}

/**
 * Log in Fibre Channel port
 *
 * @v port              Fibre Channel port
 * @v port_id           Local port ID
 * @v link_node_wwn     Link node name
 * @v link_port_wwn     Link port name
 * @v has_fabric        Link is to a fabric
 * @ret rc              Return status code
 */
int fc_port_login ( struct fc_port *port, struct fc_port_id *port_id,
                    const struct fc_name *link_node_wwn,
                    const struct fc_name *link_port_wwn, int has_fabric ) {
        struct fc_peer *peer;
        struct fc_peer *tmp;
        int rc;

        /* Perform implicit logout if logged in and details differ */
        if ( fc_link_ok ( &port->link ) &&
             ( ( ( !! ( port->flags & FC_PORT_HAS_FABRIC ) ) !=
                 ( !! has_fabric ) ) ||
               ( memcmp ( &port->link_node_wwn, link_node_wwn,
                          sizeof ( port->link_node_wwn ) ) != 0 ) ||
               ( memcmp ( &port->link_port_wwn, link_port_wwn,
                          sizeof ( port->link_port_wwn ) ) != 0 ) ||
               ( has_fabric &&
                 ( memcmp ( &port->port_id, port_id,
                            sizeof ( port->port_id ) ) != 0 ) ) ) ) {
                fc_port_logout ( port, 0 );
        }

        /* Log in, if applicable */
        if ( ! fc_link_ok ( &port->link ) ) {

                /* Record link port name */
                memcpy ( &port->link_node_wwn, link_node_wwn,
                         sizeof ( port->link_node_wwn ) );
                memcpy ( &port->link_port_wwn, link_port_wwn,
                         sizeof ( port->link_port_wwn ) );
                DBGC ( port, "FCPORT %s logged in to %s",
                       port->name, fc_ntoa ( &port->link_node_wwn ) );
                DBGC ( port, " port %s\n", fc_ntoa ( &port->link_port_wwn ) );

                /* Calculate local (and possibly remote) port IDs */
                if ( has_fabric ) {
                        port->flags |= FC_PORT_HAS_FABRIC;
                        memcpy ( &port->port_id, port_id,
                                 sizeof ( port->port_id ) );
                } else {
                        port->flags &= ~FC_PORT_HAS_FABRIC;
                        if ( memcmp ( &port->port_wwn, link_port_wwn,
                                      sizeof ( port->port_wwn ) ) > 0 ) {
                                memcpy ( &port->port_id, &fc_ptp_high_port_id,
                                         sizeof ( port->port_id ) );
                                memcpy ( &port->ptp_link_port_id,
                                         &fc_ptp_low_port_id,
                                         sizeof ( port->ptp_link_port_id ) );
                        } else {
                                memcpy ( &port->port_id, &fc_ptp_low_port_id,
                                         sizeof ( port->port_id ) );
                                memcpy ( &port->ptp_link_port_id,
                                         &fc_ptp_high_port_id,
                                         sizeof ( port->ptp_link_port_id ) );
                        }
                }
                DBGC ( port, "FCPORT %s logged in via a %s, with local ID "
                       "%s\n", port->name,
                       ( ( port->flags & FC_PORT_HAS_FABRIC ) ?
                         "fabric" : "point-to-point link" ),
                       fc_id_ntoa ( &port->port_id ) );
        }

        /* Log in to name server, if attached to a fabric */
        if ( has_fabric && ! ( port->flags & FC_PORT_HAS_NS ) ) {

                DBGC ( port, "FCPORT %s attempting login to name server\n",
                       port->name );

                intf_restart ( &port->ns_plogi, -ECANCELED );
                if ( ( rc = fc_els_plogi ( &port->ns_plogi, port,
                                           &fc_gs_port_id ) ) != 0 ) {
                        DBGC ( port, "FCPORT %s could not initiate name "
                               "server PLOGI: %s\n",
                               port->name, strerror ( rc ) );
                        fc_port_logout ( port, rc );
                        return rc;
                }
        }

        /* Record login */
        fc_link_up ( &port->link );

        /* Notify peers of link state change */
        list_for_each_entry_safe ( peer, tmp, &fc_peers, list ) {
                fc_peer_get ( peer );
                fc_link_examine ( &peer->link );
                fc_peer_put ( peer );
        }

        return 0;
}

/**
 * Log out Fibre Channel port
 *
 * @v port              Fibre Channel port
 * @v rc                Reason for logout
 */
void fc_port_logout ( struct fc_port *port, int rc ) {
        struct fc_peer *peer;
        struct fc_peer *tmp;

        DBGC ( port, "FCPORT %s logged out: %s\n",
               port->name, strerror ( rc ) );

        /* Erase port details */
        memset ( &port->port_id, 0, sizeof ( port->port_id ) );
        port->flags = 0;

        /* Record logout */
        fc_link_err ( &port->link, rc );

        /* Notify peers of link state change */
        list_for_each_entry_safe ( peer, tmp, &fc_peers, list ) {
                fc_peer_get ( peer );
                fc_link_examine ( &peer->link );
                fc_peer_put ( peer );
        }
}

/**
 * Handle FLOGI completion
 *
 * @v port              Fibre Channel port
 * @v rc                Reason for completion
 */
static void fc_port_flogi_done ( struct fc_port *port, int rc ) {

        intf_restart ( &port->flogi, rc );

        if ( rc != 0 )
                fc_port_logout ( port, rc );
}

/**
 * Handle name server PLOGI completion
 *
 * @v port              Fibre Channel port
 * @v rc                Reason for completion
 */
static void fc_port_ns_plogi_done ( struct fc_port *port, int rc ) {

        intf_restart ( &port->ns_plogi, rc );

        if ( rc == 0 ) {
                port->flags |= FC_PORT_HAS_NS;
                DBGC ( port, "FCPORT %s logged in to name server\n",
                       port->name );
        } else {
                DBGC ( port, "FCPORT %s could not log in to name server: %s\n",
                       port->name, strerror ( rc ) );
                /* Absence of a name server is not a fatal error */
        }
}

/**
 * Examine Fibre Channel port link state
 *
 * @ link               Fibre Channel link state monitor
 */
static void fc_port_examine ( struct fc_link_state *link ) {
        struct fc_port *port = container_of ( link, struct fc_port, link );
        int rc;

        /* Do nothing if already logged in */
        if ( fc_link_ok ( &port->link ) )
                return;

        DBGC ( port, "FCPORT %s attempting login\n", port->name );

        /* Try to create FLOGI ELS */
        intf_restart ( &port->flogi, -ECANCELED );
        if ( ( rc = fc_els_flogi ( &port->flogi, port ) ) != 0 ) {
                DBGC ( port, "FCPORT %s could not initiate FLOGI: %s\n",
                       port->name, strerror ( rc ) );
                fc_port_logout ( port, rc );
                return;
        }
}

/**
 * Handle change of flow control window
 *
 * @v port              Fibre Channel port
 */
static void fc_port_window_changed ( struct fc_port *port ) {
        size_t window;

        /* Check if transport layer is ready */
        window = xfer_window ( &port->transport );
        if ( window > 0 ) {

                /* Transport layer is ready.  Start login if the link
                 * is not already up.
                 */
                if ( ! fc_link_ok ( &port->link ) )
                        fc_link_start ( &port->link );

        } else {

                /* Transport layer is not ready.  Log out port and
                 * wait for transport layer before attempting log in
                 * again.
                 */
                fc_port_logout ( port, -ENOTCONN );
                fc_link_stop ( &port->link );
        }
}

/** Fibre Channel port transport interface operations */
static struct interface_operation fc_port_transport_op[] = {
        INTF_OP ( xfer_deliver, struct fc_port *, fc_port_deliver ),
        INTF_OP ( xfer_window_changed, struct fc_port *,
                  fc_port_window_changed ),
        INTF_OP ( intf_close, struct fc_port *, fc_port_close ),
};

/** Fibre Channel port transport interface descriptor */
static struct interface_descriptor fc_port_transport_desc =
        INTF_DESC ( struct fc_port, transport, fc_port_transport_op );

/** Fibre Channel port FLOGI interface operations */
static struct interface_operation fc_port_flogi_op[] = {
        INTF_OP ( intf_close, struct fc_port *, fc_port_flogi_done ),
};

/** Fibre Channel port FLOGI interface descriptor */
static struct interface_descriptor fc_port_flogi_desc =
        INTF_DESC ( struct fc_port, flogi, fc_port_flogi_op );

/** Fibre Channel port name server PLOGI interface operations */
static struct interface_operation fc_port_ns_plogi_op[] = {
        INTF_OP ( intf_close, struct fc_port *, fc_port_ns_plogi_done ),
};

/** Fibre Channel port name server PLOGI interface descriptor */
static struct interface_descriptor fc_port_ns_plogi_desc =
        INTF_DESC ( struct fc_port, ns_plogi, fc_port_ns_plogi_op );

/**
 * Create Fibre Channel port
 *
 * @v transport         Transport interface
 * @v node              Fibre Channel node name
 * @v port              Fibre Channel port name
 * @v name              Symbolic port name
 * @ret rc              Return status code
 */
int fc_port_open ( struct interface *transport, const struct fc_name *node_wwn,
                   const struct fc_name *port_wwn, const char *name ) {
        struct fc_port *port;

        /* Allocate and initialise structure */
        port = zalloc ( sizeof ( *port ) );
        if ( ! port )
                return -ENOMEM;
        ref_init ( &port->refcnt, NULL );
        intf_init ( &port->transport, &fc_port_transport_desc, &port->refcnt );
        fc_link_init ( &port->link, fc_port_examine, &port->refcnt );
        intf_init ( &port->flogi, &fc_port_flogi_desc, &port->refcnt );
        intf_init ( &port->ns_plogi, &fc_port_ns_plogi_desc, &port->refcnt );
        list_add_tail ( &port->list, &fc_ports );
        INIT_LIST_HEAD ( &port->xchgs );
        memcpy ( &port->node_wwn, node_wwn, sizeof ( port->node_wwn ) );
        memcpy ( &port->port_wwn, port_wwn, sizeof ( port->port_wwn ) );
        snprintf ( port->name, sizeof ( port->name ), "%s", name );

        DBGC ( port, "FCPORT %s opened as %s",
               port->name, fc_ntoa ( &port->node_wwn ) );
        DBGC ( port, " port %s\n", fc_ntoa ( &port->port_wwn ) );

        /* Attach to transport layer, mortalise self, and return */
        intf_plug_plug ( &port->transport, transport );
        ref_put ( &port->refcnt );
        return 0;
}

/**
 * Find Fibre Channel port by name
 *
 * @v name              Fibre Channel port name
 * @ret port            Fibre Channel port, or NULL
 */
struct fc_port * fc_port_find ( const char *name ) {
        struct fc_port *port;

        list_for_each_entry ( port, &fc_ports, list ) {
                if ( strcmp ( name, port->name ) == 0 )
                        return port;
        }
        return NULL;
}

/******************************************************************************
 *
 * Fibre Channel peers
 *
 ******************************************************************************
 */

/**
 * Close Fibre Channel peer
 *
 * @v peer              Fibre Channel peer
 * @v rc                Reason for close
 */
static void fc_peer_close ( struct fc_peer *peer, int rc ) {

        DBGC ( peer, "FCPEER %s closed: %s\n",
               fc_ntoa ( &peer->port_wwn ) , strerror ( rc ) );

        /* Sanity check */
        assert ( list_empty ( &peer->ulps ) );

        /* Stop link timer */
        fc_link_stop ( &peer->link );

        /* Shut down interfaces */
        intf_shutdown ( &peer->plogi, rc );

        /* Remove from list of peers */
        list_del ( &peer->list );
        INIT_LIST_HEAD ( &peer->list );
}

/**
 * Increment Fibre Channel peer active usage count
 *
 * @v peer              Fibre Channel peer
 */
static void fc_peer_increment ( struct fc_peer *peer ) {

        /* Increment our usage count */
        peer->usage++;
}

/**
 * Decrement Fibre Channel peer active usage count
 *
 * @v peer              Fibre Channel peer
 */
static void fc_peer_decrement ( struct fc_peer *peer ) {

        /* Sanity check */
        assert ( peer->usage > 0 );

        /* Decrement our usage count and log out if we reach zero */
        if ( --(peer->usage) == 0 )
                fc_peer_logout ( peer, 0 );
}

/**
 * Log in Fibre Channel peer
 *
 * @v peer              Fibre Channel peer
 * @v port              Fibre Channel port
 * @v port_id           Port ID
 * @ret rc              Return status code
 */
int fc_peer_login ( struct fc_peer *peer, struct fc_port *port,
                    struct fc_port_id *port_id ) {
        struct fc_ulp *ulp;
        struct fc_ulp *tmp;

        /* Perform implicit logout if logged in and details differ */
        if ( fc_link_ok ( &peer->link ) &&
             ( ( peer->port != port ) ||
               ( memcmp ( &peer->port_id, port_id,
                          sizeof ( peer->port_id ) ) !=0 ) ) ) {
                fc_peer_logout ( peer, 0 );
        }

        /* Log in, if applicable */
        if ( ! fc_link_ok ( &peer->link ) ) {

                /* Record peer details */
                assert ( peer->port == NULL );
                peer->port = fc_port_get ( port );
                memcpy ( &peer->port_id, port_id, sizeof ( peer->port_id ) );
                DBGC ( peer, "FCPEER %s logged in via %s as %s\n",
                       fc_ntoa ( &peer->port_wwn ), peer->port->name,
                       fc_id_ntoa ( &peer->port_id ) );

                /* Add login reference */
                fc_peer_get ( peer );
        }

        /* Record login */
        fc_link_up ( &peer->link );

        /* Notify ULPs of link state change */
        list_for_each_entry_safe ( ulp, tmp, &peer->ulps, list ) {
                fc_ulp_get ( ulp );
                fc_link_examine ( &ulp->link );
                fc_ulp_put ( ulp );
        }

        return 0;
}

/**
 * Log out Fibre Channel peer
 *
 * @v peer              Fibre Channel peer
 * @v rc                Reason for logout
 */
void fc_peer_logout ( struct fc_peer *peer, int rc ) {
        struct fc_ulp *ulp;
        struct fc_ulp *tmp;

        DBGC ( peer, "FCPEER %s logged out: %s\n",
               fc_ntoa ( &peer->port_wwn ), strerror ( rc ) );

        /* Drop login reference, if applicable */
        if ( fc_link_ok ( &peer->link ) )
                fc_peer_put ( peer );

        /* Erase peer details */
        fc_port_put ( peer->port );
        peer->port = NULL;

        /* Record logout */
        fc_link_err ( &peer->link, rc );

        /* Notify ULPs of link state change */
        list_for_each_entry_safe ( ulp, tmp, &peer->ulps, list ) {
                fc_ulp_get ( ulp );
                fc_link_examine ( &ulp->link );
                fc_ulp_put ( ulp );
        }

        /* Close peer if there are no active users */
        if ( peer->usage == 0 )
                fc_peer_close ( peer, rc );
}

/**
 * Handle PLOGI completion
 *
 * @v peer              Fibre Channel peer
 * @v rc                Reason for completion
 */
static void fc_peer_plogi_done ( struct fc_peer *peer, int rc ) {

        intf_restart ( &peer->plogi, rc );

        if ( rc != 0 )
                fc_peer_logout ( peer, rc );
}

/**
 * Initiate PLOGI
 *
 * @v peer              Fibre Channel peer
 * @v port              Fibre Channel port
 * @v peer_port_id      Peer port ID
 * @ret rc              Return status code
 */
static int fc_peer_plogi ( struct fc_peer *peer, struct fc_port *port,
                           struct fc_port_id *peer_port_id ) {
        int rc;

        /* Try to create PLOGI ELS */
        intf_restart ( &peer->plogi, -ECANCELED );
        if ( ( rc = fc_els_plogi ( &peer->plogi, port, peer_port_id ) ) != 0 ) {
                DBGC ( peer, "FCPEER %s could not initiate PLOGI: %s\n",
                       fc_ntoa ( &peer->port_wwn ), strerror ( rc ) );
                fc_peer_logout ( peer, rc );
                return rc;
        }

        return 0;
}

/**
 * Examine Fibre Channel peer link state
 *
 * @ link               Fibre Channel link state monitor
 */
static void fc_peer_examine ( struct fc_link_state *link ) {
        struct fc_peer *peer = container_of ( link, struct fc_peer, link );
        struct fc_port *port;
        int rc;

        /* Check to see if underlying port link has gone down */
        if ( peer->port && ( ! fc_link_ok ( &peer->port->link ) ) ) {
                fc_peer_logout ( peer, -ENOTCONN );
                return;
        }

        /* Do nothing if already logged in */
        if ( fc_link_ok ( &peer->link ) )
                return;

        DBGC ( peer, "FCPEER %s attempting login\n",
               fc_ntoa ( &peer->port_wwn ) );

        /* Sanity check */
        assert ( peer->port == NULL );

        /* First, look for a port with the peer attached via a
         * point-to-point link.
         */
        list_for_each_entry ( port, &fc_ports, list ) {
                if ( fc_link_ok ( &port->link ) &&
                     ( ! ( port->flags & FC_PORT_HAS_FABRIC ) ) &&
                     ( memcmp ( &peer->port_wwn, &port->link_port_wwn,
                                sizeof ( peer->port_wwn ) ) == 0 ) ) {
                        /* Use this peer port ID, and stop looking */
                        fc_peer_plogi ( peer, port, &port->ptp_link_port_id );
                        return;
                }
        }

        /* If the peer is not directly attached, try initiating a name
         * server lookup on any suitable ports.
         */
        list_for_each_entry ( port, &fc_ports, list ) {
                if ( fc_link_ok ( &port->link ) &&
                     ( port->flags & FC_PORT_HAS_FABRIC ) &&
                     ( port->flags & FC_PORT_HAS_NS ) ) {
                        if ( ( rc = fc_ns_query ( peer, port,
                                                  fc_peer_plogi ) ) != 0 ) {
                                DBGC ( peer, "FCPEER %s could not attempt "
                                       "name server lookup on %s: %s\n",
                                       fc_ntoa ( &peer->port_wwn ), port->name,
                                       strerror ( rc ) );
                                /* Non-fatal */
                        }
                }
        }
}

/** Fibre Channel peer PLOGI interface operations */
static struct interface_operation fc_peer_plogi_op[] = {
        INTF_OP ( intf_close, struct fc_peer *, fc_peer_plogi_done ),
};

/** Fibre Channel peer PLOGI interface descriptor */
static struct interface_descriptor fc_peer_plogi_desc =
        INTF_DESC ( struct fc_peer, plogi, fc_peer_plogi_op );

/**
 * Create Fibre Channel peer
 *
 * @v port_wwn          Node name
 * @ret peer            Fibre Channel peer, or NULL
 */
static struct fc_peer * fc_peer_create ( const struct fc_name *port_wwn ) {
        struct fc_peer *peer;

        /* Allocate and initialise structure */
        peer = zalloc ( sizeof ( *peer ) );
        if ( ! peer )
                return NULL;
        ref_init ( &peer->refcnt, NULL );
        fc_link_init ( &peer->link, fc_peer_examine, &peer->refcnt );
        intf_init ( &peer->plogi, &fc_peer_plogi_desc, &peer->refcnt );
        list_add_tail ( &peer->list, &fc_peers );
        memcpy ( &peer->port_wwn, port_wwn, sizeof ( peer->port_wwn ) );
        INIT_LIST_HEAD ( &peer->ulps );

        /* Start link monitor */
        fc_link_start ( &peer->link );

        DBGC ( peer, "FCPEER %s created\n", fc_ntoa ( &peer->port_wwn ) );
        return peer;
}

/**
 * Get Fibre Channel peer by node name
 *
 * @v port_wwn          Node name
 * @ret peer            Fibre Channel peer, or NULL
 */
struct fc_peer * fc_peer_get_wwn ( const struct fc_name *port_wwn ) {
        struct fc_peer *peer;

        /* Look for an existing peer */
        list_for_each_entry ( peer, &fc_peers, list ) {
                if ( memcmp ( &peer->port_wwn, port_wwn,
                              sizeof ( peer->port_wwn ) ) == 0 )
                        return fc_peer_get ( peer );
        }

        /* Create a new peer */
        peer = fc_peer_create ( port_wwn );
        if ( ! peer )
                return NULL;

        return peer;
}

/**
 * Get Fibre Channel peer by port ID
 *
 * @v port              Fibre Channel port
 * @v peer_port_id      Peer port ID
 * @ret peer            Fibre Channel peer, or NULL
 */
struct fc_peer * fc_peer_get_port_id ( struct fc_port *port,
                                       const struct fc_port_id *peer_port_id ){
        struct fc_peer *peer;

        /* Look for an existing peer */
        list_for_each_entry ( peer, &fc_peers, list ) {
                if ( ( peer->port == port ) &&
                     ( memcmp ( &peer->port_id, peer_port_id,
                                sizeof ( peer->port_id ) ) == 0 ) )
                        return fc_peer_get ( peer );
        }

        /* Cannot create a new peer, since we have no port name to use */
        return NULL;
}

/******************************************************************************
 *
 * Fibre Channel upper-layer protocols
 *
 ******************************************************************************
 */

/**
 * Free Fibre Channel upper-layer protocol
 *
 * @v refcnt            Reference count
 */
static void fc_ulp_free ( struct refcnt *refcnt ) {
        struct fc_ulp *ulp = container_of ( refcnt, struct fc_ulp, refcnt );

        fc_peer_put ( ulp->peer );
        free ( ulp );
}

/**
 * Close Fibre Channel upper-layer protocol
 *
 * @v ulp               Fibre Channel upper-layer protocol
 * @v rc                Reason for close
 */
static void fc_ulp_close ( struct fc_ulp *ulp, int rc ) {

        DBGC ( ulp, "FCULP %s/%02x closed: %s\n",
               fc_ntoa ( &ulp->peer->port_wwn ), ulp->type, strerror ( rc ) );

        /* Sanity check */
        assert ( list_empty ( &ulp->users ) );

        /* Stop link monitor */
        fc_link_stop ( &ulp->link );

        /* Shut down interfaces */
        intf_shutdown ( &ulp->prli, rc );

        /* Remove from list of ULPs */
        list_del ( &ulp->list );
        INIT_LIST_HEAD ( &ulp->list );
}

/**
 * Attach Fibre Channel upper-layer protocol user
 *
 * @v ulp               Fibre Channel upper-layer protocol
 * @v user              Fibre Channel upper-layer protocol user
 */
void fc_ulp_attach ( struct fc_ulp *ulp, struct fc_ulp_user *user ) {

        /* Sanity check */
        assert ( user->ulp == NULL );

        /* Increment peer's usage count */
        fc_peer_increment ( ulp->peer );

        /* Attach user */
        user->ulp = fc_ulp_get ( ulp );
        list_add ( &user->list, &ulp->users );
}

/**
 * Detach Fibre Channel upper-layer protocol user
 *
 * @v user              Fibre Channel upper-layer protocol user
 */
void fc_ulp_detach ( struct fc_ulp_user *user ) {
        struct fc_ulp *ulp = user->ulp;

        /* Do nothing if not attached */
        if ( ! ulp )
                return;

        /* Sanity checks */
        list_check_contains_entry ( user, &ulp->users, list );

        /* Detach user and log out if no users remain */
        list_del ( &user->list );
        if ( list_empty ( &ulp->users ) )
                fc_ulp_logout ( ulp, 0 );

        /* Decrement our peer's usage count */
        fc_peer_decrement ( ulp->peer );

        /* Drop reference */
        user->ulp = NULL;
        fc_ulp_put ( ulp );
}

/**
 * Log in Fibre Channel upper-layer protocol
 *
 * @v ulp               Fibre Channel upper-layer protocol
 * @v param             Service parameters
 * @v param_len         Length of service parameters
 * @v originated        Login was originated by us
 * @ret rc              Return status code
 */
int fc_ulp_login ( struct fc_ulp *ulp, const void *param, size_t param_len,
                   int originated ) {
        struct fc_ulp_user *user;
        struct fc_ulp_user *tmp;

        /* Perform implicit logout if logged in and service parameters differ */
        if ( fc_link_ok ( &ulp->link ) &&
             ( ( ulp->param_len != param_len ) ||
               ( memcmp ( ulp->param, param, ulp->param_len ) != 0 ) ) ) {
                fc_ulp_logout ( ulp, 0 );
        }

        /* Work around a bug in some versions of the Linux Fibre
         * Channel stack, which fail to fully initialise image pairs
         * established via a PRLI originated by the Linux stack
         * itself.
         */
        if ( originated )
                ulp->flags |= FC_ULP_ORIGINATED_LOGIN_OK;
        if ( ! ( ulp->flags & FC_ULP_ORIGINATED_LOGIN_OK ) ) {
                DBGC ( ulp, "FCULP %s/%02x sending extra PRLI to work around "
                       "Linux bug\n",
                       fc_ntoa ( &ulp->peer->port_wwn ), ulp->type );
                fc_link_stop ( &ulp->link );
                fc_link_start ( &ulp->link );
                return 0;
        }

        /* Log in, if applicable */
        if ( ! fc_link_ok ( &ulp->link ) ) {

                /* Record service parameters */
                assert ( ulp->param == NULL );
                assert ( ulp->param_len == 0 );
                ulp->param = malloc ( param_len );
                if ( ! ulp->param ) {
                        DBGC ( ulp, "FCULP %s/%02x could not record "
                               "parameters\n",
                               fc_ntoa ( &ulp->peer->port_wwn ), ulp->type );
                        return -ENOMEM;
                }
                memcpy ( ulp->param, param, param_len );
                ulp->param_len = param_len;
                DBGC ( ulp, "FCULP %s/%02x logged in with parameters:\n",
                       fc_ntoa ( &ulp->peer->port_wwn ), ulp->type );
                DBGC_HDA ( ulp, 0, ulp->param, ulp->param_len );

                /* Add login reference */
                fc_ulp_get ( ulp );
        }

        /* Record login */
        fc_link_up ( &ulp->link );

        /* Notify users of link state change */
        list_for_each_entry_safe ( user, tmp, &ulp->users, list ) {
                fc_ulp_user_get ( user );
                user->examine ( user );
                fc_ulp_user_put ( user );
        }

        return 0;
}

/**
 * Log out Fibre Channel upper-layer protocol
 *
 * @v ulp               Fibre Channel upper-layer protocol
 * @v rc                Reason for logout
 */
void fc_ulp_logout ( struct fc_ulp *ulp, int rc ) {
        struct fc_ulp_user *user;
        struct fc_ulp_user *tmp;

        DBGC ( ulp, "FCULP %s/%02x logged out: %s\n",
               fc_ntoa ( &ulp->peer->port_wwn ), ulp->type, strerror ( rc ) );

        /* Drop login reference, if applicable */
        if ( fc_link_ok ( &ulp->link ) )
                fc_ulp_put ( ulp );

        /* Discard service parameters */
        free ( ulp->param );
        ulp->param = NULL;
        ulp->param_len = 0;
        ulp->flags = 0;

        /* Record logout */
        fc_link_err ( &ulp->link, rc );

        /* Notify users of link state change */
        list_for_each_entry_safe ( user, tmp, &ulp->users, list ) {
                fc_ulp_user_get ( user );
                user->examine ( user );
                fc_ulp_user_put ( user );
        }

        /* Close ULP if there are no clients attached */
        if ( list_empty ( &ulp->users ) )
                fc_ulp_close ( ulp, rc );
}

/**
 * Handle PRLI completion
 *
 * @v ulp               Fibre Channel upper-layer protocol
 * @v rc                Reason for completion
 */
static void fc_ulp_prli_done ( struct fc_ulp *ulp, int rc ) {

        intf_restart ( &ulp->prli, rc );

        if ( rc != 0 )
                fc_ulp_logout ( ulp, rc );
}

/**
 * Examine Fibre Channel upper-layer protocol link state
 *
 * @ link               Fibre Channel link state monitor
 */
static void fc_ulp_examine ( struct fc_link_state *link ) {
        struct fc_ulp *ulp = container_of ( link, struct fc_ulp, link );
        int rc;

        /* Check to see if underlying peer link has gone down */
        if ( ! fc_link_ok ( &ulp->peer->link ) ) {
                fc_ulp_logout ( ulp, -ENOTCONN );
                return;
        }

        /* Do nothing if already logged in */
        if ( fc_link_ok ( &ulp->link ) &&
             ( ulp->flags & FC_ULP_ORIGINATED_LOGIN_OK ) )
                return;

        DBGC ( ulp, "FCULP %s/%02x attempting login\n",
               fc_ntoa ( &ulp->peer->port_wwn ), ulp->type );

        /* Try to create PRLI ELS */
        intf_restart ( &ulp->prli, -ECANCELED );
        if ( ( rc = fc_els_prli ( &ulp->prli, ulp->peer->port,
                                  &ulp->peer->port_id, ulp->type ) ) != 0 ) {
                DBGC ( ulp, "FCULP %s/%02x could not initiate PRLI: %s\n",
                       fc_ntoa ( &ulp->peer->port_wwn ), ulp->type,
                       strerror ( rc ) );
                fc_ulp_logout ( ulp, rc );
                return;
        }
}

/** Fibre Channel upper-layer protocol PRLI interface operations */
static struct interface_operation fc_ulp_prli_op[] = {
        INTF_OP ( intf_close, struct fc_ulp *, fc_ulp_prli_done ),
};

/** Fibre Channel upper-layer protocol PRLI interface descriptor */
static struct interface_descriptor fc_ulp_prli_desc =
        INTF_DESC ( struct fc_ulp, prli, fc_ulp_prli_op );

/**
 * Create Fibre Channel upper-layer protocl
 *
 * @v peer              Fibre Channel peer
 * @v type              Type
 * @ret ulp             Fibre Channel upper-layer protocol, or NULL
 */
static struct fc_ulp * fc_ulp_create ( struct fc_peer *peer,
                                       unsigned int type ) {
        struct fc_ulp *ulp;

        /* Allocate and initialise structure */
        ulp = zalloc ( sizeof ( *ulp ) );
        if ( ! ulp )
                return NULL;
        ref_init ( &ulp->refcnt, fc_ulp_free );
        fc_link_init ( &ulp->link, fc_ulp_examine, &ulp->refcnt );
        intf_init ( &ulp->prli, &fc_ulp_prli_desc, &ulp->refcnt );
        ulp->peer = fc_peer_get ( peer );
        list_add_tail ( &ulp->list, &peer->ulps );
        ulp->type = type;
        INIT_LIST_HEAD ( &ulp->users );

        /* Start link state monitor */
        fc_link_start ( &ulp->link );

        DBGC ( ulp, "FCULP %s/%02x created\n",
               fc_ntoa ( &ulp->peer->port_wwn ), ulp->type );
        return ulp;
}

/**
 * Get Fibre Channel upper-layer protocol by peer and type
 *
 * @v peer              Fibre Channel peer
 * @v type              Type
 * @ret ulp             Fibre Channel upper-layer protocol, or NULL
 */
static struct fc_ulp * fc_ulp_get_type ( struct fc_peer *peer,
                                         unsigned int type ) {
        struct fc_ulp *ulp;

        /* Look for an existing ULP */
        list_for_each_entry ( ulp, &peer->ulps, list ) {
                if ( ulp->type == type )
                        return fc_ulp_get ( ulp );
        }

        /* Create a new ULP */
        ulp = fc_ulp_create ( peer, type );
        if ( ! ulp )
                return NULL;

        return ulp;
}

/**
 * Get Fibre Channel upper-layer protocol by port name and type
 *
 * @v port_wwn          Port name
 * @v type              Type
 * @ret ulp             Fibre Channel upper-layer protocol, or NULL
 */
struct fc_ulp * fc_ulp_get_wwn_type ( const struct fc_name *port_wwn,
                                      unsigned int type ) {
        struct fc_ulp *ulp;
        struct fc_peer *peer;

        /* Get peer */
        peer = fc_peer_get_wwn ( port_wwn );
        if ( ! peer )
                goto err_peer_get_wwn;

        /* Get ULP */
        ulp = fc_ulp_get_type ( peer, type );
        if ( ! ulp )
                goto err_ulp_get_type;

        /* Drop temporary reference to peer */
        fc_peer_put ( peer );

        return ulp;

        fc_ulp_put ( ulp );
 err_ulp_get_type:
        fc_peer_put ( peer );
 err_peer_get_wwn:
        return NULL;
}

/**
 * Get Fibre Channel upper-layer protocol by port ID and type
 *
 * @v port              Fibre Channel port
 * @v peer_port_id      Peer port ID
 * @v type              Type
 * @ret ulp             Fibre Channel upper-layer protocol, or NULL
 */
struct fc_ulp * fc_ulp_get_port_id_type ( struct fc_port *port,
                                          const struct fc_port_id *peer_port_id,
                                          unsigned int type ) {
        struct fc_ulp *ulp;
        struct fc_peer *peer;

        /* Get peer */
        peer = fc_peer_get_port_id ( port, peer_port_id );
        if ( ! peer )
                goto err_peer_get_wwn;

        /* Get ULP */
        ulp = fc_ulp_get_type ( peer, type );
        if ( ! ulp )
                goto err_ulp_get_type;

        /* Drop temporary reference to peer */
        fc_peer_put ( peer );

        return ulp;

        fc_ulp_put ( ulp );
 err_ulp_get_type:
        fc_peer_put ( peer );
 err_peer_get_wwn:
        return NULL;
}

/* Drag in objects via fc_ports */
REQUIRING_SYMBOL ( fc_ports );

/* Drag in Fibre Channel configuration */
REQUIRE_OBJECT ( config_fc );