source: bootcd/isolinux/syslinux-6.03/gpxe/src/net/tcp/iscsi.c @ e16e8f2

/*
 * Copyright (C) 2006 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

#include <stddef.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <assert.h>
#include <byteswap.h>
#include <gpxe/vsprintf.h>
#include <gpxe/socket.h>
#include <gpxe/xfer.h>
#include <gpxe/open.h>
#include <gpxe/scsi.h>
#include <gpxe/process.h>
#include <gpxe/uaccess.h>
#include <gpxe/tcpip.h>
#include <gpxe/settings.h>
#include <gpxe/features.h>
#include <gpxe/iscsi.h>

/** @file
 *
 * iSCSI protocol
 *
 */

FEATURE ( FEATURE_PROTOCOL, "iSCSI", DHCP_EB_FEATURE_ISCSI, 1 );

/** iSCSI initiator name (explicitly specified) */
static char *iscsi_explicit_initiator_iqn;

/** Default iSCSI initiator name (constructed from hostname) */
static char *iscsi_default_initiator_iqn;

/** iSCSI initiator username */
static char *iscsi_initiator_username;

/** iSCSI initiator password */
static char *iscsi_initiator_password;

/** iSCSI target username */
static char *iscsi_target_username;

/** iSCSI target password */
static char *iscsi_target_password;

static void iscsi_start_tx ( struct iscsi_session *iscsi );
static void iscsi_start_login ( struct iscsi_session *iscsi );
static void iscsi_start_data_out ( struct iscsi_session *iscsi,
                                   unsigned int datasn );

/**
 * Finish receiving PDU data into buffer
 *
 * @v iscsi             iSCSI session
 */
static void iscsi_rx_buffered_data_done ( struct iscsi_session *iscsi ) {
        free ( iscsi->rx_buffer );
        iscsi->rx_buffer = NULL;
}

/**
 * Free iSCSI session
 *
 * @v refcnt            Reference counter
 */
static void iscsi_free ( struct refcnt *refcnt ) {
        struct iscsi_session *iscsi =
                container_of ( refcnt, struct iscsi_session, refcnt );

        free ( iscsi->target_address );
        free ( iscsi->target_iqn );
        free ( iscsi->initiator_username );
        free ( iscsi->initiator_password );
        free ( iscsi->target_username );
        free ( iscsi->target_password );
        chap_finish ( &iscsi->chap );
        iscsi_rx_buffered_data_done ( iscsi );
        free ( iscsi );
}

/**
 * Open iSCSI transport-layer connection
 *
 * @v iscsi             iSCSI session
 * @ret rc              Return status code
 */
static int iscsi_open_connection ( struct iscsi_session *iscsi ) {
        struct sockaddr_tcpip target;
        int rc;

        assert ( iscsi->tx_state == ISCSI_TX_IDLE );
        assert ( iscsi->rx_state == ISCSI_RX_BHS );
        assert ( iscsi->rx_offset == 0 );

        /* Open socket */
        memset ( &target, 0, sizeof ( target ) );
        target.st_port = htons ( iscsi->target_port );
        if ( ( rc = xfer_open_named_socket ( &iscsi->socket, SOCK_STREAM,
                                             ( struct sockaddr * ) &target,
                                             iscsi->target_address,
                                             NULL ) ) != 0 ) {
                DBGC ( iscsi, "iSCSI %p could not open socket: %s\n",
                       iscsi, strerror ( rc ) );
                return rc;
        }

        /* Enter security negotiation phase */
        iscsi->status = ( ISCSI_STATUS_SECURITY_NEGOTIATION_PHASE |
                          ISCSI_STATUS_STRINGS_SECURITY );
        if ( iscsi->target_username )
                iscsi->status |= ISCSI_STATUS_AUTH_REVERSE_REQUIRED;

        /* Assign fresh initiator task tag */
        iscsi->itt++;

        /* Initiate login */
        iscsi_start_login ( iscsi );

        return 0;
}

/**
 * Close iSCSI transport-layer connection
 *
 * @v iscsi             iSCSI session
 * @v rc                Reason for close
 *
 * Closes the transport-layer connection and resets the session state
 * ready to attempt a fresh login.
 */
static void iscsi_close_connection ( struct iscsi_session *iscsi, int rc ) {

        /* Close all data transfer interfaces */
        xfer_close ( &iscsi->socket, rc );

        /* Clear connection status */
        iscsi->status = 0;

        /* Reset TX and RX state machines */
        iscsi->tx_state = ISCSI_TX_IDLE;
        iscsi->rx_state = ISCSI_RX_BHS;
        iscsi->rx_offset = 0;

        /* Free any temporary dynamically allocated memory */
        chap_finish ( &iscsi->chap );
        iscsi_rx_buffered_data_done ( iscsi );
}

/**
 * Mark iSCSI SCSI operation as complete
 *
 * @v iscsi             iSCSI session
 * @v rc                Return status code
 *
 * Note that iscsi_scsi_done() will not close the connection, and must
 * therefore be called only when the internal state machines are in an
 * appropriate state, otherwise bad things may happen on the next call
 * to iscsi_issue().  The general rule is to call iscsi_scsi_done()
 * only at the end of receiving a PDU; at this point the TX and RX
 * engines should both be idle.
 */
static void iscsi_scsi_done ( struct iscsi_session *iscsi, int rc ) {

        assert ( iscsi->tx_state == ISCSI_TX_IDLE );
        assert ( iscsi->command != NULL );

        iscsi->command->rc = rc;
        iscsi->command = NULL;
}

/****************************************************************************
 *
 * iSCSI SCSI command issuing
 *
 */

/**
 * Build iSCSI SCSI command BHS
 *
 * @v iscsi             iSCSI session
 *
 * We don't currently support bidirectional commands (i.e. with both
 * Data-In and Data-Out segments); these would require providing code
 * to generate an AHS, and there doesn't seem to be any need for it at
 * the moment.
 */
static void iscsi_start_command ( struct iscsi_session *iscsi ) {
        struct iscsi_bhs_scsi_command *command = &iscsi->tx_bhs.scsi_command;

        assert ( ! ( iscsi->command->data_in && iscsi->command->data_out ) );

        /* Construct BHS and initiate transmission */
        iscsi_start_tx ( iscsi );
        command->opcode = ISCSI_OPCODE_SCSI_COMMAND;
        command->flags = ( ISCSI_FLAG_FINAL |
                           ISCSI_COMMAND_ATTR_SIMPLE );
        if ( iscsi->command->data_in )
                command->flags |= ISCSI_COMMAND_FLAG_READ;
        if ( iscsi->command->data_out )
                command->flags |= ISCSI_COMMAND_FLAG_WRITE;
        /* lengths left as zero */
        command->lun = iscsi->lun;
        command->itt = htonl ( ++iscsi->itt );
        command->exp_len = htonl ( iscsi->command->data_in_len |
                                   iscsi->command->data_out_len );
        command->cmdsn = htonl ( iscsi->cmdsn );
        command->expstatsn = htonl ( iscsi->statsn + 1 );
        memcpy ( &command->cdb, &iscsi->command->cdb, sizeof ( command->cdb ));
        DBGC2 ( iscsi, "iSCSI %p start " SCSI_CDB_FORMAT " %s %#zx\n",
                iscsi, SCSI_CDB_DATA ( command->cdb ),
                ( iscsi->command->data_in ? "in" : "out" ),
                ( iscsi->command->data_in ?
                  iscsi->command->data_in_len :
                  iscsi->command->data_out_len ) );
}

/**
 * Receive data segment of an iSCSI SCSI response PDU
 *
 * @v iscsi             iSCSI session
 * @v data              Received data
 * @v len               Length of received data
 * @v remaining         Data remaining after this data
 * @ret rc              Return status code
 */
static int iscsi_rx_scsi_response ( struct iscsi_session *iscsi,
                                    const void *data, size_t len,
                                    size_t remaining ) {
        struct iscsi_bhs_scsi_response *response
                = &iscsi->rx_bhs.scsi_response;
        int sense_offset;

        /* Capture the sense response code as it floats past, if present */
        sense_offset = ISCSI_SENSE_RESPONSE_CODE_OFFSET - iscsi->rx_offset;
        if ( ( sense_offset >= 0 ) && len ) {
                iscsi->command->sense_response =
                        * ( ( char * ) data + sense_offset );
        }

        /* Wait for whole SCSI response to arrive */
        if ( remaining )
                return 0;
        
        /* Record SCSI status code */
        iscsi->command->status = response->status;

        /* Check for errors */
        if ( response->response != ISCSI_RESPONSE_COMMAND_COMPLETE )
                return -EIO;

        /* Mark as completed */
        iscsi_scsi_done ( iscsi, 0 );
        return 0;
}

/**
 * Receive data segment of an iSCSI data-in PDU
 *
 * @v iscsi             iSCSI session
 * @v data              Received data
 * @v len               Length of received data
 * @v remaining         Data remaining after this data
 * @ret rc              Return status code
 */
static int iscsi_rx_data_in ( struct iscsi_session *iscsi,
                              const void *data, size_t len,
                              size_t remaining ) {
        struct iscsi_bhs_data_in *data_in = &iscsi->rx_bhs.data_in;
        unsigned long offset;

        /* Copy data to data-in buffer */
        offset = ntohl ( data_in->offset ) + iscsi->rx_offset;
        assert ( iscsi->command != NULL );
        assert ( iscsi->command->data_in );
        assert ( ( offset + len ) <= iscsi->command->data_in_len );
        copy_to_user ( iscsi->command->data_in, offset, data, len );

        /* Wait for whole SCSI response to arrive */
        if ( remaining )
                return 0;

        /* Mark as completed if status is present */
        if ( data_in->flags & ISCSI_DATA_FLAG_STATUS ) {
                assert ( ( offset + len ) == iscsi->command->data_in_len );
                assert ( data_in->flags & ISCSI_FLAG_FINAL );
                iscsi->command->status = data_in->status;
                /* iSCSI cannot return an error status via a data-in */
                iscsi_scsi_done ( iscsi, 0 );
        }

        return 0;
}

/**
 * Receive data segment of an iSCSI R2T PDU
 *
 * @v iscsi             iSCSI session
 * @v data              Received data
 * @v len               Length of received data
 * @v remaining         Data remaining after this data
 * @ret rc              Return status code
 */
static int iscsi_rx_r2t ( struct iscsi_session *iscsi,
                          const void *data __unused, size_t len __unused,
                          size_t remaining __unused ) {
        struct iscsi_bhs_r2t *r2t = &iscsi->rx_bhs.r2t;

        /* Record transfer parameters and trigger first data-out */
        iscsi->ttt = ntohl ( r2t->ttt );
        iscsi->transfer_offset = ntohl ( r2t->offset );
        iscsi->transfer_len = ntohl ( r2t->len );
        iscsi_start_data_out ( iscsi, 0 );

        return 0;
}

/**
 * Build iSCSI data-out BHS
 *
 * @v iscsi             iSCSI session
 * @v datasn            Data sequence number within the transfer
 *
 */
static void iscsi_start_data_out ( struct iscsi_session *iscsi,
                                   unsigned int datasn ) {
        struct iscsi_bhs_data_out *data_out = &iscsi->tx_bhs.data_out;
        unsigned long offset;
        unsigned long remaining;
        unsigned long len;

        /* We always send 512-byte Data-Out PDUs; this removes the
         * need to worry about the target's MaxRecvDataSegmentLength.
         */
        offset = datasn * 512;
        remaining = iscsi->transfer_len - offset;
        len = remaining;
        if ( len > 512 )
                len = 512;

        /* Construct BHS and initiate transmission */
        iscsi_start_tx ( iscsi );
        data_out->opcode = ISCSI_OPCODE_DATA_OUT;
        if ( len == remaining )
                data_out->flags = ( ISCSI_FLAG_FINAL );
        ISCSI_SET_LENGTHS ( data_out->lengths, 0, len );
        data_out->lun = iscsi->lun;
        data_out->itt = htonl ( iscsi->itt );
        data_out->ttt = htonl ( iscsi->ttt );
        data_out->expstatsn = htonl ( iscsi->statsn + 1 );
        data_out->datasn = htonl ( datasn );
        data_out->offset = htonl ( iscsi->transfer_offset + offset );
        DBGC ( iscsi, "iSCSI %p start data out DataSN %#x len %#lx\n",
               iscsi, datasn, len );
}

/**
 * Complete iSCSI data-out PDU transmission
 *
 * @v iscsi             iSCSI session
 *
 */
static void iscsi_data_out_done ( struct iscsi_session *iscsi ) {
        struct iscsi_bhs_data_out *data_out = &iscsi->tx_bhs.data_out;

        /* If we haven't reached the end of the sequence, start
         * sending the next data-out PDU.
         */
        if ( ! ( data_out->flags & ISCSI_FLAG_FINAL ) )
                iscsi_start_data_out ( iscsi, ntohl ( data_out->datasn ) + 1 );
}

/**
 * Send iSCSI data-out data segment
 *
 * @v iscsi             iSCSI session
 * @ret rc              Return status code
 */
static int iscsi_tx_data_out ( struct iscsi_session *iscsi ) {
        struct iscsi_bhs_data_out *data_out = &iscsi->tx_bhs.data_out;
        struct io_buffer *iobuf;
        unsigned long offset;
        size_t len;

        offset = ntohl ( data_out->offset );
        len = ISCSI_DATA_LEN ( data_out->lengths );

        assert ( iscsi->command != NULL );
        assert ( iscsi->command->data_out );
        assert ( ( offset + len ) <= iscsi->command->data_out_len );

        iobuf = xfer_alloc_iob ( &iscsi->socket, len );
        if ( ! iobuf )
                return -ENOMEM;
        
        copy_from_user ( iob_put ( iobuf, len ),
                         iscsi->command->data_out, offset, len );

        return xfer_deliver_iob ( &iscsi->socket, iobuf );
}

/****************************************************************************
 *
 * iSCSI login
 *
 */

/**
 * Build iSCSI login request strings
 *
 * @v iscsi             iSCSI session
 *
 * These are the initial set of strings sent in the first login
 * request PDU.  We want the following settings:
 *
 *     HeaderDigest=None
 *     DataDigest=None
 *     MaxConnections is irrelevant; we make only one connection anyway
 *     InitialR2T=Yes [1]
 *     ImmediateData is irrelevant; we never send immediate data
 *     MaxRecvDataSegmentLength=8192 (default; we don't care) [3]
 *     MaxBurstLength=262144 (default; we don't care) [3]
 *     FirstBurstLength=262144 (default; we don't care)
 *     DefaultTime2Wait=0 [2]
 *     DefaultTime2Retain=0 [2]
 *     MaxOutstandingR2T=1
 *     DataPDUInOrder=Yes
 *     DataSequenceInOrder=Yes
 *     ErrorRecoveryLevel=0
 *
 * [1] InitialR2T has an OR resolution function, so the target may
 * force us to use it.  We therefore simplify our logic by always
 * using it.
 *
 * [2] These ensure that we can safely start a new task once we have
 * reconnected after a failure, without having to manually tidy up
 * after the old one.
 *
 * [3] We are quite happy to use the RFC-defined default values for
 * these parameters, but some targets (notably OpenSolaris)
 * incorrectly assume a default value of zero, so we explicitly
 * specify the default values.
 */
static int iscsi_build_login_request_strings ( struct iscsi_session *iscsi,
                                               void *data, size_t len ) {
        unsigned int used = 0;
        unsigned int i;
        const char *auth_method;

        if ( iscsi->status & ISCSI_STATUS_STRINGS_SECURITY ) {
                /* Default to allowing no authentication */
                auth_method = "None";
                /* If we have a credential to supply, permit CHAP */
                if ( iscsi->initiator_username )
                        auth_method = "CHAP,None";
                /* If we have a credential to check, force CHAP */
                if ( iscsi->target_username )
                        auth_method = "CHAP";
                used += ssnprintf ( data + used, len - used,
                                    "InitiatorName=%s%c"
                                    "TargetName=%s%c"
                                    "SessionType=Normal%c"
                                    "AuthMethod=%s%c",
                                    iscsi_initiator_iqn(), 0,
                                    iscsi->target_iqn, 0, 0,
                                    auth_method, 0 );
        }

        if ( iscsi->status & ISCSI_STATUS_STRINGS_CHAP_ALGORITHM ) {
                used += ssnprintf ( data + used, len - used, "CHAP_A=5%c", 0 );
        }
        
        if ( ( iscsi->status & ISCSI_STATUS_STRINGS_CHAP_RESPONSE ) ) {
                assert ( iscsi->initiator_username != NULL );
                used += ssnprintf ( data + used, len - used,
                                    "CHAP_N=%s%cCHAP_R=0x",
                                    iscsi->initiator_username, 0 );
                for ( i = 0 ; i < iscsi->chap.response_len ; i++ ) {
                        used += ssnprintf ( data + used, len - used, "%02x",
                                            iscsi->chap.response[i] );
                }
                used += ssnprintf ( data + used, len - used, "%c", 0 );
        }

        if ( ( iscsi->status & ISCSI_STATUS_STRINGS_CHAP_CHALLENGE ) ) {
                used += ssnprintf ( data + used, len - used,
                                    "CHAP_I=%d%cCHAP_C=0x",
                                    iscsi->chap_challenge[0], 0 );
                for ( i = 1 ; i < sizeof ( iscsi->chap_challenge ) ; i++ ) {
                        used += ssnprintf ( data + used, len - used, "%02x",
                                            iscsi->chap_challenge[i] );
                }
                used += ssnprintf ( data + used, len - used, "%c", 0 );
        }

        if ( iscsi->status & ISCSI_STATUS_STRINGS_OPERATIONAL ) {
                used += ssnprintf ( data + used, len - used,
                                    "HeaderDigest=None%c"
                                    "DataDigest=None%c"
                                    "InitialR2T=Yes%c"
                                    "MaxRecvDataSegmentLength=8192%c"
                                    "MaxBurstLength=262144%c"
                                    "DefaultTime2Wait=0%c"
                                    "DefaultTime2Retain=0%c"
                                    "MaxOutstandingR2T=1%c"
                                    "DataPDUInOrder=Yes%c"
                                    "DataSequenceInOrder=Yes%c"
                                    "ErrorRecoveryLevel=0%c",
                                    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 );
        }

        return used;
}

/**
 * Build iSCSI login request BHS
 *
 * @v iscsi             iSCSI session
 */
static void iscsi_start_login ( struct iscsi_session *iscsi ) {
        struct iscsi_bhs_login_request *request = &iscsi->tx_bhs.login_request;
        int len;

        /* Construct BHS and initiate transmission */
        iscsi_start_tx ( iscsi );
        request->opcode = ( ISCSI_OPCODE_LOGIN_REQUEST |
                            ISCSI_FLAG_IMMEDIATE );
        request->flags = ( ( iscsi->status & ISCSI_STATUS_PHASE_MASK ) |
                           ISCSI_LOGIN_FLAG_TRANSITION );
        /* version_max and version_min left as zero */
        len = iscsi_build_login_request_strings ( iscsi, NULL, 0 );
        ISCSI_SET_LENGTHS ( request->lengths, 0, len );
        request->isid_iana_en = htonl ( ISCSI_ISID_IANA |
                                        IANA_EN_FEN_SYSTEMS );
        /* isid_iana_qual left as zero */
        request->tsih = htons ( iscsi->tsih );
        request->itt = htonl ( iscsi->itt );
        /* cid left as zero */
        request->cmdsn = htonl ( iscsi->cmdsn );
        request->expstatsn = htonl ( iscsi->statsn + 1 );
}

/**
 * Complete iSCSI login request PDU transmission
 *
 * @v iscsi             iSCSI session
 *
 */
static void iscsi_login_request_done ( struct iscsi_session *iscsi ) {

        /* Clear any "strings to send" flags */
        iscsi->status &= ~ISCSI_STATUS_STRINGS_MASK;

        /* Free any dynamically allocated storage used for login */
        chap_finish ( &iscsi->chap );
}

/**
 * Transmit data segment of an iSCSI login request PDU
 *
 * @v iscsi             iSCSI session
 * @ret rc              Return status code
 *
 * For login requests, the data segment consists of the login strings.
 */
static int iscsi_tx_login_request ( struct iscsi_session *iscsi ) {
        struct iscsi_bhs_login_request *request = &iscsi->tx_bhs.login_request;
        struct io_buffer *iobuf;
        size_t len;

        len = ISCSI_DATA_LEN ( request->lengths );
        iobuf = xfer_alloc_iob ( &iscsi->socket, len );
        if ( ! iobuf )
                return -ENOMEM;
        iob_put ( iobuf, len );
        iscsi_build_login_request_strings ( iscsi, iobuf->data, len );
        return xfer_deliver_iob ( &iscsi->socket, iobuf );
}

/**
 * Handle iSCSI TargetAddress text value
 *
 * @v iscsi             iSCSI session
 * @v value             TargetAddress value
 * @ret rc              Return status code
 */
static int iscsi_handle_targetaddress_value ( struct iscsi_session *iscsi,
                                              const char *value ) {
        char *separator;

        DBGC ( iscsi, "iSCSI %p will redirect to %s\n", iscsi, value );

        /* Replace target address */
        free ( iscsi->target_address );
        iscsi->target_address = strdup ( value );
        if ( ! iscsi->target_address )
                return -ENOMEM;

        /* Replace target port */
        iscsi->target_port = htons ( ISCSI_PORT );
        separator = strchr ( iscsi->target_address, ':' );
        if ( separator ) {
                *separator = '\0';
                iscsi->target_port = strtoul ( ( separator + 1 ), NULL, 0 );
        }

        return 0;
}

/**
 * Handle iSCSI AuthMethod text value
 *
 * @v iscsi             iSCSI session
 * @v value             AuthMethod value
 * @ret rc              Return status code
 */
static int iscsi_handle_authmethod_value ( struct iscsi_session *iscsi,
                                           const char *value ) {

        /* If server requests CHAP, send the CHAP_A string */
        if ( strcmp ( value, "CHAP" ) == 0 ) {
                DBGC ( iscsi, "iSCSI %p initiating CHAP authentication\n",
                       iscsi );
                iscsi->status |= ( ISCSI_STATUS_STRINGS_CHAP_ALGORITHM |
                                   ISCSI_STATUS_AUTH_FORWARD_REQUIRED );
        }

        return 0;
}

/**
 * Handle iSCSI CHAP_A text value
 *
 * @v iscsi             iSCSI session
 * @v value             CHAP_A value
 * @ret rc              Return status code
 */
static int iscsi_handle_chap_a_value ( struct iscsi_session *iscsi,
                                       const char *value ) {

        /* We only ever offer "5" (i.e. MD5) as an algorithm, so if
         * the server responds with anything else it is a protocol
         * violation.
         */
        if ( strcmp ( value, "5" ) != 0 ) {
                DBGC ( iscsi, "iSCSI %p got invalid CHAP algorithm \"%s\"\n",
                       iscsi, value );
                return -EPROTO;
        }

        return 0;
}

/**
 * Handle iSCSI CHAP_I text value
 *
 * @v iscsi             iSCSI session
 * @v value             CHAP_I value
 * @ret rc              Return status code
 */
static int iscsi_handle_chap_i_value ( struct iscsi_session *iscsi,
                                       const char *value ) {
        unsigned int identifier;
        char *endp;
        int rc;

        /* The CHAP identifier is an integer value */
        identifier = strtoul ( value, &endp, 0 );
        if ( *endp != '\0' ) {
                DBGC ( iscsi, "iSCSI %p saw invalid CHAP identifier \"%s\"\n",
                       iscsi, value );
                return -EPROTO;
        }

        /* Prepare for CHAP with MD5 */
        chap_finish ( &iscsi->chap );
        if ( ( rc = chap_init ( &iscsi->chap, &md5_algorithm ) ) != 0 ) {
                DBGC ( iscsi, "iSCSI %p could not initialise CHAP: %s\n",
                       iscsi, strerror ( rc ) );
                return rc;
        }

        /* Identifier and secret are the first two components of the
         * challenge.
         */
        chap_set_identifier ( &iscsi->chap, identifier );
        if ( iscsi->initiator_password ) {
                chap_update ( &iscsi->chap, iscsi->initiator_password,
                              strlen ( iscsi->initiator_password ) );
        }

        return 0;
}

/**
 * Handle iSCSI CHAP_C text value
 *
 * @v iscsi             iSCSI session
 * @v value             CHAP_C value
 * @ret rc              Return status code
 */
static int iscsi_handle_chap_c_value ( struct iscsi_session *iscsi,
                                       const char *value ) {
        char buf[3];
        char *endp;
        uint8_t byte;
        unsigned int i;

        /* Check and strip leading "0x" */
        if ( ( value[0] != '0' ) || ( value[1] != 'x' ) ) {
                DBGC ( iscsi, "iSCSI %p saw invalid CHAP challenge \"%s\"\n",
                       iscsi, value );
                return -EPROTO;
        }
        value += 2;

        /* Process challenge an octet at a time */
        for ( ; ( value[0] && value[1] ) ; value += 2 ) {
                memcpy ( buf, value, 2 );
                buf[2] = 0;
                byte = strtoul ( buf, &endp, 16 );
                if ( *endp != '\0' ) {
                        DBGC ( iscsi, "iSCSI %p saw invalid CHAP challenge "
                               "byte \"%s\"\n", iscsi, buf );
                        return -EPROTO;
                }
                chap_update ( &iscsi->chap, &byte, sizeof ( byte ) );
        }

        /* Build CHAP response */
        DBGC ( iscsi, "iSCSI %p sending CHAP response\n", iscsi );
        chap_respond ( &iscsi->chap );
        iscsi->status |= ISCSI_STATUS_STRINGS_CHAP_RESPONSE;

        /* Send CHAP challenge, if applicable */
        if ( iscsi->target_username ) {
                iscsi->status |= ISCSI_STATUS_STRINGS_CHAP_CHALLENGE;
                /* Generate CHAP challenge data */
                for ( i = 0 ; i < sizeof ( iscsi->chap_challenge ) ; i++ ) {
                        iscsi->chap_challenge[i] = random();
                }
        }

        return 0;
}

/**
 * Handle iSCSI CHAP_N text value
 *
 * @v iscsi             iSCSI session
 * @v value             CHAP_N value
 * @ret rc              Return status code
 */
static int iscsi_handle_chap_n_value ( struct iscsi_session *iscsi,
                                       const char *value ) {

        /* The target username isn't actually involved at any point in
         * the authentication process; it merely serves to identify
         * which password the target is using to generate the CHAP
         * response.  We unnecessarily verify that the username is as
         * expected, in order to provide mildly helpful diagnostics if
         * the target is supplying the wrong username/password
         * combination.
         */
        if ( iscsi->target_username &&
             ( strcmp ( iscsi->target_username, value ) != 0 ) ) {
                DBGC ( iscsi, "iSCSI %p target username \"%s\" incorrect "
                       "(wanted \"%s\")\n",
                       iscsi, value, iscsi->target_username );
                return -EACCES;
        }

        return 0;
}

/**
 * Handle iSCSI CHAP_R text value
 *
 * @v iscsi             iSCSI session
 * @v value             CHAP_R value
 * @ret rc              Return status code
 */
static int iscsi_handle_chap_r_value ( struct iscsi_session *iscsi,
                                       const char *value ) {
        char buf[3];
        char *endp;
        uint8_t byte;
        unsigned int i;
        int rc;

        /* Generate CHAP response for verification */
        chap_finish ( &iscsi->chap );
        if ( ( rc = chap_init ( &iscsi->chap, &md5_algorithm ) ) != 0 ) {
                DBGC ( iscsi, "iSCSI %p could not initialise CHAP: %s\n",
                       iscsi, strerror ( rc ) );
                return rc;
        }
        chap_set_identifier ( &iscsi->chap, iscsi->chap_challenge[0] );
        if ( iscsi->target_password ) {
                chap_update ( &iscsi->chap, iscsi->target_password,
                              strlen ( iscsi->target_password ) );
        }
        chap_update ( &iscsi->chap, &iscsi->chap_challenge[1],
                      ( sizeof ( iscsi->chap_challenge ) - 1 ) );
        chap_respond ( &iscsi->chap );

        /* Check and strip leading "0x" */
        if ( ( value[0] != '0' ) || ( value[1] != 'x' ) ) {
                DBGC ( iscsi, "iSCSI %p saw invalid CHAP response \"%s\"\n",
                       iscsi, value );
                return -EPROTO;
        }
        value += 2;

        /* Check CHAP response length */
        if ( strlen ( value ) != ( 2 * iscsi->chap.response_len ) ) {
                DBGC ( iscsi, "iSCSI %p invalid CHAP response length\n",
                       iscsi );
                return -EPROTO;
        }

        /* Process response an octet at a time */
        for ( i = 0 ; ( value[0] && value[1] ) ; value += 2, i++ ) {
                memcpy ( buf, value, 2 );
                buf[2] = 0;
                byte = strtoul ( buf, &endp, 16 );
                if ( *endp != '\0' ) {
                        DBGC ( iscsi, "iSCSI %p saw invalid CHAP response "
                               "byte \"%s\"\n", iscsi, buf );
                        return -EPROTO;
                }
                if ( byte != iscsi->chap.response[i] ) {
                        DBGC ( iscsi, "iSCSI %p saw incorrect CHAP "
                               "response\n", iscsi );
                        return -EACCES;
                }
        }
        assert ( i == iscsi->chap.response_len );

        /* Mark session as authenticated */
        iscsi->status |= ISCSI_STATUS_AUTH_REVERSE_OK;

        return 0;
}

/** An iSCSI text string that we want to handle */
struct iscsi_string_type {
        /** String key
         *
         * This is the portion up to and including the "=" sign,
         * e.g. "InitiatorName=", "CHAP_A=", etc.
         */
        const char *key;
        /** Handle iSCSI string value
         *
         * @v iscsi             iSCSI session
         * @v value             iSCSI string value
         * @ret rc              Return status code
         */
        int ( * handle ) ( struct iscsi_session *iscsi, const char *value );
};

/** iSCSI text strings that we want to handle */
static struct iscsi_string_type iscsi_string_types[] = {
        { "TargetAddress=", iscsi_handle_targetaddress_value },
        { "AuthMethod=", iscsi_handle_authmethod_value },
        { "CHAP_A=", iscsi_handle_chap_a_value },
        { "CHAP_I=", iscsi_handle_chap_i_value },
        { "CHAP_C=", iscsi_handle_chap_c_value },
        { "CHAP_N=", iscsi_handle_chap_n_value },
        { "CHAP_R=", iscsi_handle_chap_r_value },
        { NULL, NULL }
};

/**
 * Handle iSCSI string
 *
 * @v iscsi             iSCSI session
 * @v string            iSCSI string (in "key=value" format)
 * @ret rc              Return status code
 */
static int iscsi_handle_string ( struct iscsi_session *iscsi,
                                 const char *string ) {
        struct iscsi_string_type *type;
        size_t key_len;
        int rc;

        for ( type = iscsi_string_types ; type->key ; type++ ) {
                key_len = strlen ( type->key );
                if ( strncmp ( string, type->key, key_len ) != 0 )
                        continue;
                DBGC ( iscsi, "iSCSI %p handling %s\n", iscsi, string );
                if ( ( rc = type->handle ( iscsi,
                                           ( string + key_len ) ) ) != 0 ) {
                        DBGC ( iscsi, "iSCSI %p could not handle %s: %s\n",
                               iscsi, string, strerror ( rc ) );
                        return rc;
                }
                return 0;
        }
        DBGC ( iscsi, "iSCSI %p ignoring %s\n", iscsi, string );
        return 0;
}

/**
 * Handle iSCSI strings
 *
 * @v iscsi             iSCSI session
 * @v string            iSCSI string buffer
 * @v len               Length of string buffer
 * @ret rc              Return status code
 */
static int iscsi_handle_strings ( struct iscsi_session *iscsi,
                                  const char *strings, size_t len ) {
        size_t string_len;
        int rc;

        /* Handle each string in turn, taking care not to overrun the
         * data buffer in case of badly-terminated data.
         */
        while ( 1 ) {
                string_len = ( strnlen ( strings, len ) + 1 );
                if ( string_len > len )
                        break;
                if ( ( rc = iscsi_handle_string ( iscsi, strings ) ) != 0 )
                        return rc;
                strings += string_len;
                len -= string_len;
        }
        return 0;
}

/**
 * Receive PDU data into buffer
 *
 * @v iscsi             iSCSI session
 * @v data              Data to receive
 * @v len               Length of data
 * @ret rc              Return status code
 *
 * This can be used when the RX PDU type handler wishes to buffer up
 * all received data and process the PDU as a single unit.  The caller
 * is repsonsible for calling iscsi_rx_buffered_data_done() after
 * processing the data.
 */
static int iscsi_rx_buffered_data ( struct iscsi_session *iscsi,
                                    const void *data, size_t len ) {

        /* Allocate buffer on first call */
        if ( ! iscsi->rx_buffer ) {
                iscsi->rx_buffer = malloc ( iscsi->rx_len );
                if ( ! iscsi->rx_buffer )
                        return -ENOMEM;
        }

        /* Copy data to buffer */
        assert ( ( iscsi->rx_offset + len ) <= iscsi->rx_len );
        memcpy ( ( iscsi->rx_buffer + iscsi->rx_offset ), data, len );

        return 0;
}

/**
 * Convert iSCSI response status to return status code
 *
 * @v status_class      iSCSI status class
 * @v status_detail     iSCSI status detail
 * @ret rc              Return status code
 */
static int iscsi_status_to_rc ( unsigned int status_class,
                                unsigned int status_detail ) {
        switch ( status_class ) {
        case ISCSI_STATUS_INITIATOR_ERROR :
                switch ( status_detail ) {
                case ISCSI_STATUS_INITIATOR_ERROR_AUTHENTICATION :
                        return -EACCES;
                case ISCSI_STATUS_INITIATOR_ERROR_AUTHORISATION :
                        return -EPERM;
                case ISCSI_STATUS_INITIATOR_ERROR_NOT_FOUND :
                case ISCSI_STATUS_INITIATOR_ERROR_REMOVED :
                        return -ENODEV;
                default :
                        return -ENOTSUP;
                }
        case ISCSI_STATUS_TARGET_ERROR :
                return -EIO;
        default :
                return -EINVAL;
        }
}

/**
 * Receive data segment of an iSCSI login response PDU
 *
 * @v iscsi             iSCSI session
 * @v data              Received data
 * @v len               Length of received data
 * @v remaining         Data remaining after this data
 * @ret rc              Return status code
 */
static int iscsi_rx_login_response ( struct iscsi_session *iscsi,
                                     const void *data, size_t len,
                                     size_t remaining ) {
        struct iscsi_bhs_login_response *response
                = &iscsi->rx_bhs.login_response;
        int rc;

        /* Buffer up the PDU data */
        if ( ( rc = iscsi_rx_buffered_data ( iscsi, data, len ) ) != 0 ) {
                DBGC ( iscsi, "iSCSI %p could not buffer login response: %s\n",
                       iscsi, strerror ( rc ) );
                return rc;
        }
        if ( remaining )
                return 0;

        /* Process string data and discard string buffer */
        if ( ( rc = iscsi_handle_strings ( iscsi, iscsi->rx_buffer,
                                           iscsi->rx_len ) ) != 0 )
                return rc;
        iscsi_rx_buffered_data_done ( iscsi );

        /* Check for login redirection */
        if ( response->status_class == ISCSI_STATUS_REDIRECT ) {
                DBGC ( iscsi, "iSCSI %p redirecting to new server\n", iscsi );
                iscsi_close_connection ( iscsi, 0 );
                if ( ( rc = iscsi_open_connection ( iscsi ) ) != 0 ) {
                        DBGC ( iscsi, "iSCSI %p could not redirect: %s\n ",
                               iscsi, strerror ( rc ) );
                        return rc;
                }
                return 0;
        }

        /* Check for fatal errors */
        if ( response->status_class != 0 ) {
                DBGC ( iscsi, "iSCSI login failure: class %02x detail %02x\n",
                       response->status_class, response->status_detail );
                rc = iscsi_status_to_rc ( response->status_class,
                                          response->status_detail );
                iscsi->instant_rc = rc;
                return rc;
        }

        /* Handle login transitions */
        if ( response->flags & ISCSI_LOGIN_FLAG_TRANSITION ) {
                iscsi->status &= ~( ISCSI_STATUS_PHASE_MASK |
                                    ISCSI_STATUS_STRINGS_MASK );
                switch ( response->flags & ISCSI_LOGIN_NSG_MASK ) {
                case ISCSI_LOGIN_NSG_OPERATIONAL_NEGOTIATION:
                        iscsi->status |=
                                ( ISCSI_STATUS_OPERATIONAL_NEGOTIATION_PHASE |
                                  ISCSI_STATUS_STRINGS_OPERATIONAL );
                        break;
                case ISCSI_LOGIN_NSG_FULL_FEATURE_PHASE:
                        iscsi->status |= ISCSI_STATUS_FULL_FEATURE_PHASE;
                        break;
                default:
                        DBGC ( iscsi, "iSCSI %p got invalid response flags "
                               "%02x\n", iscsi, response->flags );
                        return -EIO;
                }
        }

        /* Send next login request PDU if we haven't reached the full
         * feature phase yet.
         */
        if ( ( iscsi->status & ISCSI_STATUS_PHASE_MASK ) !=
             ISCSI_STATUS_FULL_FEATURE_PHASE ) {
                iscsi_start_login ( iscsi );
                return 0;
        }

        /* Check that target authentication was successful (if required) */
        if ( ( iscsi->status & ISCSI_STATUS_AUTH_REVERSE_REQUIRED ) &&
             ! ( iscsi->status & ISCSI_STATUS_AUTH_REVERSE_OK ) ) {
                DBGC ( iscsi, "iSCSI %p nefarious target tried to bypass "
                       "authentication\n", iscsi );
                return -EPROTO;
        }

        /* Reset retry count */
        iscsi->retry_count = 0;

        /* Record TSIH for future reference */
        iscsi->tsih = ntohl ( response->tsih );
        
        /* Send the actual SCSI command */
        iscsi_start_command ( iscsi );

        return 0;
}

/****************************************************************************
 *
 * iSCSI to socket interface
 *
 */

/**
 * Start up a new TX PDU
 *
 * @v iscsi             iSCSI session
 *
 * This initiates the process of sending a new PDU.  Only one PDU may
 * be in transit at any one time.
 */
static void iscsi_start_tx ( struct iscsi_session *iscsi ) {
        assert ( iscsi->tx_state == ISCSI_TX_IDLE );
        
        /* Initialise TX BHS */
        memset ( &iscsi->tx_bhs, 0, sizeof ( iscsi->tx_bhs ) );

        /* Flag TX engine to start transmitting */
        iscsi->tx_state = ISCSI_TX_BHS;
}

/**
 * Transmit nothing
 *
 * @v iscsi             iSCSI session
 * @ret rc              Return status code
 */
static int iscsi_tx_nothing ( struct iscsi_session *iscsi __unused ) {
        return 0;
}

/**
 * Transmit basic header segment of an iSCSI PDU
 *
 * @v iscsi             iSCSI session
 * @ret rc              Return status code
 */
static int iscsi_tx_bhs ( struct iscsi_session *iscsi ) {
        return xfer_deliver_raw ( &iscsi->socket,  &iscsi->tx_bhs,
                                  sizeof ( iscsi->tx_bhs ) );
}

/**
 * Transmit data segment of an iSCSI PDU
 *
 * @v iscsi             iSCSI session
 * @ret rc              Return status code
 * 
 * Handle transmission of part of a PDU data segment.  iscsi::tx_bhs
 * will be valid when this is called.
 */
static int iscsi_tx_data ( struct iscsi_session *iscsi ) {
        struct iscsi_bhs_common *common = &iscsi->tx_bhs.common;

        switch ( common->opcode & ISCSI_OPCODE_MASK ) {
        case ISCSI_OPCODE_DATA_OUT:
                return iscsi_tx_data_out ( iscsi );
        case ISCSI_OPCODE_LOGIN_REQUEST:
                return iscsi_tx_login_request ( iscsi );
        default:
                /* Nothing to send in other states */
                return 0;
        }
}

/**
 * Transmit data padding of an iSCSI PDU
 *
 * @v iscsi             iSCSI session
 * @ret rc              Return status code
 * 
 * Handle transmission of any data padding in a PDU data segment.
 * iscsi::tx_bhs will be valid when this is called.
 */
static int iscsi_tx_data_padding ( struct iscsi_session *iscsi ) {
        static const char pad[] = { '\0', '\0', '\0' };
        struct iscsi_bhs_common *common = &iscsi->tx_bhs.common;
        size_t pad_len;
        
        pad_len = ISCSI_DATA_PAD_LEN ( common->lengths );
        if ( ! pad_len )
                return 0;

        return xfer_deliver_raw ( &iscsi->socket, pad, pad_len );
}

/**
 * Complete iSCSI PDU transmission
 *
 * @v iscsi             iSCSI session
 *
 * Called when a PDU has been completely transmitted and the TX state
 * machine is about to enter the idle state.  iscsi::tx_bhs will be
 * valid for the just-completed PDU when this is called.
 */
static void iscsi_tx_done ( struct iscsi_session *iscsi ) {
        struct iscsi_bhs_common *common = &iscsi->tx_bhs.common;

        switch ( common->opcode & ISCSI_OPCODE_MASK ) {
        case ISCSI_OPCODE_DATA_OUT:
                iscsi_data_out_done ( iscsi );
        case ISCSI_OPCODE_LOGIN_REQUEST:
                iscsi_login_request_done ( iscsi );
        default:
                /* No action */
                break;
        }
}

/**
 * Transmit iSCSI PDU
 *
 * @v iscsi             iSCSI session
 * @v buf               Temporary data buffer
 * @v len               Length of temporary data buffer
 * 
 * Constructs data to be sent for the current TX state
 */
static void iscsi_tx_step ( struct process *process ) {
        struct iscsi_session *iscsi =
                container_of ( process, struct iscsi_session, process );
        struct iscsi_bhs_common *common = &iscsi->tx_bhs.common;
        int ( * tx ) ( struct iscsi_session *iscsi );
        enum iscsi_tx_state next_state;
        size_t tx_len;
        int rc;

        /* Select fragment to transmit */
        while ( 1 ) {
                switch ( iscsi->tx_state ) {
                case ISCSI_TX_IDLE:
                        /* Stop processing */
                        return;
                case ISCSI_TX_BHS:
                        tx = iscsi_tx_bhs;
                        tx_len = sizeof ( iscsi->tx_bhs );
                        next_state = ISCSI_TX_AHS;
                        break;
                case ISCSI_TX_AHS:
                        tx = iscsi_tx_nothing;
                        tx_len = 0;
                        next_state = ISCSI_TX_DATA;
                        break;
                case ISCSI_TX_DATA:
                        tx = iscsi_tx_data;
                        tx_len = ISCSI_DATA_LEN ( common->lengths );
                        next_state = ISCSI_TX_DATA_PADDING;
                        break;
                case ISCSI_TX_DATA_PADDING:
                        tx = iscsi_tx_data_padding;
                        tx_len = ISCSI_DATA_PAD_LEN ( common->lengths );
                        next_state = ISCSI_TX_IDLE;
                        break;
                default:
                        assert ( 0 );
                        return;
                }

                /* Check for window availability, if needed */
                if ( tx_len && ( xfer_window ( &iscsi->socket ) == 0 ) ) {
                        /* Cannot transmit at this point; stop processing */
                        return;
                }

                /* Transmit data */
                if ( ( rc = tx ( iscsi ) ) != 0 ) {
                        DBGC ( iscsi, "iSCSI %p could not transmit: %s\n",
                               iscsi, strerror ( rc ) );
                        return;
                }

                /* Move to next state */
                iscsi->tx_state = next_state;
                if ( next_state == ISCSI_TX_IDLE )
                        iscsi_tx_done ( iscsi );
        }
}

/**
 * Receive basic header segment of an iSCSI PDU
 *
 * @v iscsi             iSCSI session
 * @v data              Received data
 * @v len               Length of received data
 * @v remaining         Data remaining after this data
 * @ret rc              Return status code
 *
 * This fills in iscsi::rx_bhs with the data from the BHS portion of
 * the received PDU.
 */
static int iscsi_rx_bhs ( struct iscsi_session *iscsi, const void *data,
                          size_t len, size_t remaining __unused ) {
        memcpy ( &iscsi->rx_bhs.bytes[iscsi->rx_offset], data, len );
        if ( ( iscsi->rx_offset + len ) >= sizeof ( iscsi->rx_bhs ) ) {
                DBGC2 ( iscsi, "iSCSI %p received PDU opcode %#x len %#x\n",
                        iscsi, iscsi->rx_bhs.common.opcode,
                        ISCSI_DATA_LEN ( iscsi->rx_bhs.common.lengths ) );
        }
        return 0;
}

/**
 * Discard portion of an iSCSI PDU.
 *
 * @v iscsi             iSCSI session
 * @v data              Received data
 * @v len               Length of received data
 * @v remaining         Data remaining after this data
 * @ret rc              Return status code
 *
 * This discards data from a portion of a received PDU.
 */
static int iscsi_rx_discard ( struct iscsi_session *iscsi __unused,
                              const void *data __unused, size_t len __unused,
                              size_t remaining __unused ) {
        /* Do nothing */
        return 0;
}

/**
 * Receive data segment of an iSCSI PDU
 *
 * @v iscsi             iSCSI session
 * @v data              Received data
 * @v len               Length of received data
 * @v remaining         Data remaining after this data
 * @ret rc              Return status code
 *
 * Handle processing of part of a PDU data segment.  iscsi::rx_bhs
 * will be valid when this is called.
 */
static int iscsi_rx_data ( struct iscsi_session *iscsi, const void *data,
                           size_t len, size_t remaining ) {
        struct iscsi_bhs_common_response *response
                = &iscsi->rx_bhs.common_response;

        /* Update cmdsn and statsn */
        iscsi->cmdsn = ntohl ( response->expcmdsn );
        iscsi->statsn = ntohl ( response->statsn );

        switch ( response->opcode & ISCSI_OPCODE_MASK ) {
        case ISCSI_OPCODE_LOGIN_RESPONSE:
                return iscsi_rx_login_response ( iscsi, data, len, remaining );
        case ISCSI_OPCODE_SCSI_RESPONSE:
                return iscsi_rx_scsi_response ( iscsi, data, len, remaining );
        case ISCSI_OPCODE_DATA_IN:
                return iscsi_rx_data_in ( iscsi, data, len, remaining );
        case ISCSI_OPCODE_R2T:
                return iscsi_rx_r2t ( iscsi, data, len, remaining );
        default:
                if ( remaining )
                        return 0;
                DBGC ( iscsi, "iSCSI %p unknown opcode %02x\n", iscsi,
                       response->opcode );
                return -ENOTSUP;
        }
}

/**
 * Receive new data
 *
 * @v socket            Transport layer interface
 * @v data              Received data
 * @v len               Length of received data
 * @ret rc              Return status code
 *
 * This handles received PDUs.  The receive strategy is to fill in
 * iscsi::rx_bhs with the contents of the BHS portion of the PDU,
 * throw away any AHS portion, and then process each part of the data
 * portion as it arrives.  The data processing routine therefore
 * always has a full copy of the BHS available, even for portions of
 * the data in different packets to the BHS.
 */
static int iscsi_socket_deliver_raw ( struct xfer_interface *socket,
                                      const void *data, size_t len ) {
        struct iscsi_session *iscsi =
                container_of ( socket, struct iscsi_session, socket );
        struct iscsi_bhs_common *common = &iscsi->rx_bhs.common;
        int ( * rx ) ( struct iscsi_session *iscsi, const void *data,
                       size_t len, size_t remaining );
        enum iscsi_rx_state next_state;
        size_t frag_len;
        size_t remaining;
        int rc;

        while ( 1 ) {
                switch ( iscsi->rx_state ) {
                case ISCSI_RX_BHS:
                        rx = iscsi_rx_bhs;
                        iscsi->rx_len = sizeof ( iscsi->rx_bhs );
                        next_state = ISCSI_RX_AHS;                      
                        break;
                case ISCSI_RX_AHS:
                        rx = iscsi_rx_discard;
                        iscsi->rx_len = 4 * ISCSI_AHS_LEN ( common->lengths );
                        next_state = ISCSI_RX_DATA;
                        break;
                case ISCSI_RX_DATA:
                        rx = iscsi_rx_data;
                        iscsi->rx_len = ISCSI_DATA_LEN ( common->lengths );
                        next_state = ISCSI_RX_DATA_PADDING;
                        break;
                case ISCSI_RX_DATA_PADDING:
                        rx = iscsi_rx_discard;
                        iscsi->rx_len = ISCSI_DATA_PAD_LEN ( common->lengths );
                        next_state = ISCSI_RX_BHS;
                        break;
                default:
                        assert ( 0 );
                        return -EINVAL;
                }

                frag_len = iscsi->rx_len - iscsi->rx_offset;
                if ( frag_len > len )
                        frag_len = len;
                remaining = iscsi->rx_len - iscsi->rx_offset - frag_len;
                if ( ( rc = rx ( iscsi, data, frag_len, remaining ) ) != 0 ) {
                        DBGC ( iscsi, "iSCSI %p could not process received "
                               "data: %s\n", iscsi, strerror ( rc ) );
                        iscsi_close_connection ( iscsi, rc );
                        iscsi_scsi_done ( iscsi, rc );
                        return rc;
                }

                iscsi->rx_offset += frag_len;
                data += frag_len;
                len -= frag_len;

                /* If all the data for this state has not yet been
                 * received, stay in this state for now.
                 */
                if ( iscsi->rx_offset != iscsi->rx_len )
                        return 0;

                iscsi->rx_state = next_state;
                iscsi->rx_offset = 0;
        }

        return 0;
}

/**
 * Handle stream connection closure
 *
 * @v socket            Transport layer interface
 * @v rc                Reason for close
 *
 */
static void iscsi_socket_close ( struct xfer_interface *socket, int rc ) {
        struct iscsi_session *iscsi =
                container_of ( socket, struct iscsi_session, socket );

        /* Even a graceful close counts as an error for iSCSI */
        if ( ! rc )
                rc = -ECONNRESET;

        /* Close session cleanly */
        iscsi_close_connection ( iscsi, rc );

        /* Retry connection if within the retry limit, otherwise fail */
        if ( ++iscsi->retry_count <= ISCSI_MAX_RETRIES ) {
                DBGC ( iscsi, "iSCSI %p retrying connection (retry #%d)\n",
                       iscsi, iscsi->retry_count );
                if ( ( rc = iscsi_open_connection ( iscsi ) ) != 0 ) {
                        DBGC ( iscsi, "iSCSI %p could not reconnect: %s\n",
                               iscsi, strerror ( rc ) );
                        iscsi_scsi_done ( iscsi, rc );
                }
        } else {
                DBGC ( iscsi, "iSCSI %p retry count exceeded\n", iscsi );
                iscsi->instant_rc = rc;
                iscsi_scsi_done ( iscsi, rc );
        }
}

/**
 * Handle redirection event
 *
 * @v socket            Transport layer interface
 * @v type              Location type
 * @v args              Remaining arguments depend upon location type
 * @ret rc              Return status code
 */
static int iscsi_vredirect ( struct xfer_interface *socket, int type,
                             va_list args ) {
        struct iscsi_session *iscsi =
                container_of ( socket, struct iscsi_session, socket );
        va_list tmp;
        struct sockaddr *peer;

        /* Intercept redirects to a LOCATION_SOCKET and record the IP
         * address for the iBFT.  This is a bit of a hack, but avoids
         * inventing an ioctl()-style call to retrieve the socket
         * address from a data-xfer interface.
         */
        if ( type == LOCATION_SOCKET ) {
                va_copy ( tmp, args );
                ( void ) va_arg ( tmp, int ); /* Discard "semantics" */
                peer = va_arg ( tmp, struct sockaddr * );
                memcpy ( &iscsi->target_sockaddr, peer,
                         sizeof ( iscsi->target_sockaddr ) );
                va_end ( tmp );
        }

        return xfer_vreopen ( socket, type, args );
}
                             

/** iSCSI socket operations */
static struct xfer_interface_operations iscsi_socket_operations = {
        .close          = iscsi_socket_close,
        .vredirect      = iscsi_vredirect,
        .window         = unlimited_xfer_window,
        .alloc_iob      = default_xfer_alloc_iob,
        .deliver_iob    = xfer_deliver_as_raw,
        .deliver_raw    = iscsi_socket_deliver_raw,
};


/****************************************************************************
 *
 * iSCSI command issuing
 *
 */

/**
 * Issue SCSI command
 *
 * @v scsi              SCSI device
 * @v command           SCSI command
 * @ret rc              Return status code
 */
static int iscsi_command ( struct scsi_device *scsi,
                           struct scsi_command *command ) {
        struct iscsi_session *iscsi =
                container_of ( scsi->backend, struct iscsi_session, refcnt );
        int rc;

        /* Abort immediately if we have a recorded permanent failure */
        if ( iscsi->instant_rc )
                return iscsi->instant_rc;

        /* Record SCSI command */
        iscsi->command = command;

        /* Issue command or open connection as appropriate */
        if ( iscsi->status ) {
                iscsi_start_command ( iscsi );
        } else {
                if ( ( rc = iscsi_open_connection ( iscsi ) ) != 0 ) {
                        iscsi->command = NULL;
                        return rc;
                }
        }

        return 0;
}

/**
 * Shut down iSCSI interface
 *
 * @v scsi              SCSI device
 */
void iscsi_detach ( struct scsi_device *scsi ) {
        struct iscsi_session *iscsi =
                container_of ( scsi->backend, struct iscsi_session, refcnt );

        xfer_nullify ( &iscsi->socket );
        iscsi_close_connection ( iscsi, 0 );
        process_del ( &iscsi->process );
        scsi->command = scsi_detached_command;
        ref_put ( scsi->backend );
        scsi->backend = NULL;
}

/****************************************************************************
 *
 * Instantiator
 *
 */

/** iSCSI root path components (as per RFC4173) */
enum iscsi_root_path_component {
        RP_LITERAL = 0,
        RP_SERVERNAME,
        RP_PROTOCOL,
        RP_PORT,
        RP_LUN,
        RP_TARGETNAME,
        NUM_RP_COMPONENTS
};

/**
 * Parse iSCSI root path
 *
 * @v iscsi             iSCSI session
 * @v root_path         iSCSI root path (as per RFC4173)
 * @ret rc              Return status code
 */
static int iscsi_parse_root_path ( struct iscsi_session *iscsi,
                                   const char *root_path ) {
        char rp_copy[ strlen ( root_path ) + 1 ];
        char *rp_comp[NUM_RP_COMPONENTS];
        char *rp = rp_copy;
        int i = 0;
        int rc;

        /* Split root path into component parts */
        strcpy ( rp_copy, root_path );
        while ( 1 ) {
                rp_comp[i++] = rp;
                if ( i == NUM_RP_COMPONENTS )
                        break;
                for ( ; *rp != ':' ; rp++ ) {
                        if ( ! *rp ) {
                                DBGC ( iscsi, "iSCSI %p root path \"%s\" "
                                       "too short\n", iscsi, root_path );
                                return -EINVAL;
                        }
                }
                *(rp++) = '\0';
        }

        /* Use root path components to configure iSCSI session */
        iscsi->target_address = strdup ( rp_comp[RP_SERVERNAME] );
        if ( ! iscsi->target_address )
                return -ENOMEM;
        iscsi->target_port = strtoul ( rp_comp[RP_PORT], NULL, 10 );
        if ( ! iscsi->target_port )
                iscsi->target_port = ISCSI_PORT;
        if ( ( rc = scsi_parse_lun ( rp_comp[RP_LUN], &iscsi->lun ) ) != 0 ) {
                DBGC ( iscsi, "iSCSI %p invalid LUN \"%s\"\n",
                       iscsi, rp_comp[RP_LUN] );
                return rc;
        }
        iscsi->target_iqn = strdup ( rp_comp[RP_TARGETNAME] );
        if ( ! iscsi->target_iqn )
                return -ENOMEM;

        return 0;
}

/**
 * Set iSCSI authentication details
 *
 * @v iscsi             iSCSI session
 * @v initiator_username Initiator username, if any
 * @v initiator_password Initiator password, if any
 * @v target_username   Target username, if any
 * @v target_password   Target password, if any
 * @ret rc              Return status code
 */
static int iscsi_set_auth ( struct iscsi_session *iscsi,
                            const char *initiator_username,
                            const char *initiator_password,
                            const char *target_username,
                            const char *target_password ) {

        /* Check for initiator or target credentials */
        if ( initiator_username || initiator_password ||
             target_username || target_password ) {

                /* We must have at least an initiator username+password */
                if ( ! ( initiator_username && initiator_password ) )
                        goto invalid_auth;

                /* Store initiator credentials */
                iscsi->initiator_username = strdup ( initiator_username );
                if ( ! iscsi->initiator_username )
                        return -ENOMEM;
                iscsi->initiator_password = strdup ( initiator_password );
                if ( ! iscsi->initiator_password )
                        return -ENOMEM;

                /* Check for target credentials */
                if ( target_username || target_password ) {

                        /* We must have target username+password */
                        if ( ! ( target_username && target_password ) )
                                goto invalid_auth;

                        /* Store target credentials */
                        iscsi->target_username = strdup ( target_username );
                        if ( ! iscsi->target_username )
                                return -ENOMEM;
                        iscsi->target_password = strdup ( target_password );
                        if ( ! iscsi->target_password )
                                return -ENOMEM;
                }
        }

        return 0;

 invalid_auth:
        DBGC ( iscsi, "iSCSI %p invalid credentials: initiator "
               "%sname,%spw, target %sname,%spw\n", iscsi,
               ( initiator_username ? "" : "no " ),
               ( initiator_password ? "" : "no " ),
               ( target_username ? "" : "no " ),
               ( target_password ? "" : "no " ) );
        return -EINVAL;
}

/**
 * Attach iSCSI interface
 *
 * @v scsi              SCSI device
 * @v root_path         iSCSI root path (as per RFC4173)
 * @ret rc              Return status code
 */
int iscsi_attach ( struct scsi_device *scsi, const char *root_path ) {
        struct iscsi_session *iscsi;
        int rc;

        /* Allocate and initialise structure */
        iscsi = zalloc ( sizeof ( *iscsi ) );
        if ( ! iscsi )
                return -ENOMEM;
        iscsi->refcnt.free = iscsi_free;
        xfer_init ( &iscsi->socket, &iscsi_socket_operations, &iscsi->refcnt );
        process_init ( &iscsi->process, iscsi_tx_step, &iscsi->refcnt );

        /* Parse root path */
        if ( ( rc = iscsi_parse_root_path ( iscsi, root_path ) ) != 0 )
                goto err;
        /* Set fields not specified by root path */
        if ( ( rc = iscsi_set_auth ( iscsi,
                                     iscsi_initiator_username,
                                     iscsi_initiator_password,
                                     iscsi_target_username,
                                     iscsi_target_password ) ) != 0 )
                goto err;

        /* Sanity checks */
        if ( ! iscsi->target_address ) {
                DBGC ( iscsi, "iSCSI %p does not yet support discovery\n",
                       iscsi );
                rc = -ENOTSUP;
                goto err;
        }
        if ( ! iscsi->target_iqn ) {
                DBGC ( iscsi, "iSCSI %p no target address supplied in %s\n",
                       iscsi, root_path );
                rc = -EINVAL;
                goto err;
        }

        /* Attach parent interface, mortalise self, and return */
        scsi->backend = ref_get ( &iscsi->refcnt );
        scsi->command = iscsi_command;
        ref_put ( &iscsi->refcnt );
        return 0;
        
 err:
        ref_put ( &iscsi->refcnt );
        return rc;
}

/****************************************************************************
 *
 * Settings
 *
 */

/** iSCSI initiator IQN setting */
struct setting initiator_iqn_setting __setting = {
        .name = "initiator-iqn",
        .description = "iSCSI initiator name",
        .tag = DHCP_ISCSI_INITIATOR_IQN,
        .type = &setting_type_string,
};

/** iSCSI reverse username setting */
struct setting reverse_username_setting __setting = {
        .name = "reverse-username",
        .description = "Reverse user name",
        .tag = DHCP_EB_REVERSE_USERNAME,
        .type = &setting_type_string,
};

/** iSCSI reverse password setting */
struct setting reverse_password_setting __setting = {
        .name = "reverse-password",
        .description = "Reverse password",
        .tag = DHCP_EB_REVERSE_PASSWORD,
        .type = &setting_type_string,
};

/** An iSCSI string setting */
struct iscsi_string_setting {
        /** Setting */
        struct setting *setting;
        /** String to update */
        char **string;
        /** String prefix */
        const char *prefix;
};

/** iSCSI string settings */
static struct iscsi_string_setting iscsi_string_settings[] = {
        {
                .setting = &initiator_iqn_setting,
                .string = &iscsi_explicit_initiator_iqn,
                .prefix = "",
        },
        {
                .setting = &username_setting,
                .string = &iscsi_initiator_username,
                .prefix = "",
        },
        {
                .setting = &password_setting,
                .string = &iscsi_initiator_password,
                .prefix = "",
        },
        {
                .setting = &reverse_username_setting,
                .string = &iscsi_target_username,
                .prefix = "",
        },
        {
                .setting = &reverse_password_setting,
                .string = &iscsi_target_password,
                .prefix = "",
        },
        {
                .setting = &hostname_setting,
                .string = &iscsi_default_initiator_iqn,
                .prefix = "iqn.2000-01.org.etherboot:",
        },
};

/**
 * Apply iSCSI setting
 *
 * @v setting           iSCSI string setting
 * @ret rc              Return status code
 */
static int apply_iscsi_string_setting ( struct iscsi_string_setting *setting ){
        size_t prefix_len;
        int setting_len;
        size_t len;
        int check_len;
        char *p;

        /* Free old string */
        free ( *setting->string );
        *setting->string = NULL;

        /* Allocate new string */
        prefix_len = strlen ( setting->prefix );
        setting_len = fetch_setting_len ( NULL, setting->setting );
        if ( setting_len < 0 ) {
                /* Missing settings are not errors; leave strings as NULL */
                return 0;
        }
        len = ( prefix_len + setting_len + 1 );
        p = *setting->string = malloc ( len );
        if ( ! p )
                return -ENOMEM;

        /* Fill new string */
        strcpy ( p, setting->prefix );
        check_len = fetch_string_setting ( NULL, setting->setting,
                                           ( p + prefix_len ),
                                           ( len - prefix_len ) );
        assert ( check_len == setting_len );

        return 0;
}

/**
 * Apply iSCSI settings
 *
 * @ret rc              Return status code
 */
static int apply_iscsi_settings ( void ) {
        struct iscsi_string_setting *setting;
        unsigned int i;
        int rc;

        for ( i = 0 ; i < ( sizeof ( iscsi_string_settings ) /
                            sizeof ( iscsi_string_settings[0] ) ) ; i++ ) {
                setting = &iscsi_string_settings[i];
                if ( ( rc = apply_iscsi_string_setting ( setting ) ) != 0 ) {
                        DBG ( "iSCSI could not apply setting %s\n",
                              setting->setting->name );
                        return rc;
                }
        }

        return 0;
}

/** iSCSI settings applicator */
struct settings_applicator iscsi_settings_applicator __settings_applicator = {
        .apply = apply_iscsi_settings,
};

/****************************************************************************
 *
 * Initiator name
 *
 */

/**
 * Get iSCSI initiator IQN
 *
 * @v iscsi             iSCSI session
 * @ret rc              Return status code
 */
const char * iscsi_initiator_iqn ( void ) {

        if ( iscsi_explicit_initiator_iqn )
                return iscsi_explicit_initiator_iqn;
        if ( iscsi_default_initiator_iqn )
                return iscsi_default_initiator_iqn;
        return "iqn.2000-09.org.etherboot:UNKNOWN";
}