text: /*
   * 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 <ipxe/vsprintf.h>
  #include <ipxe/socket.h>
  #include <ipxe/iobuf.h>
  #include <ipxe/uri.h>
  #include <ipxe/xfer.h>
  #include <ipxe/open.h>
  #include <ipxe/scsi.h>
  #include <ipxe/process.h>
  #include <ipxe/uaccess.h>
  #include <ipxe/tcpip.h>
  #include <ipxe/settings.h>
  #include <ipxe/features.h>
  #include <ipxe/base16.h>
  #include <ipxe/base64.h>
  #include <ipxe/ibft.h>
  #include <ipxe/iscsi.h>
  
  /** @file
   *
   * iSCSI protocol
   *
   */
  
  FEATURE ( FEATURE_PROTOCOL, "iSCSI", DHCP_EB_FEATURE_ISCSI, 1 );
  
  /* Disambiguate the various error causes */
  #define EACCES_INCORRECT_TARGET_USERNAME \
  	__einfo_error ( EINFO_EACCES_INCORRECT_TARGET_USERNAME )
  #define EINFO_EACCES_INCORRECT_TARGET_USERNAME \
  	__einfo_uniqify ( EINFO_EACCES, 0x01, "Incorrect target username" )
  #define EACCES_INCORRECT_TARGET_PASSWORD \
  	__einfo_error ( EINFO_EACCES_INCORRECT_TARGET_PASSWORD )
  #define EINFO_EACCES_INCORRECT_TARGET_PASSWORD \
  	__einfo_uniqify ( EINFO_EACCES, 0x02, "Incorrect target password" )
  #define EINVAL_ROOT_PATH_TOO_SHORT \
  	__einfo_error ( EINFO_EINVAL_ROOT_PATH_TOO_SHORT )
  #define EINFO_EINVAL_ROOT_PATH_TOO_SHORT \
  	__einfo_uniqify ( EINFO_EINVAL, 0x01, "Root path too short" )
  #define EINVAL_BAD_CREDENTIAL_MIX \
  	__einfo_error ( EINFO_EINVAL_BAD_CREDENTIAL_MIX )
  #define EINFO_EINVAL_BAD_CREDENTIAL_MIX \
  	__einfo_uniqify ( EINFO_EINVAL, 0x02, "Bad credential mix" )
  #define EINVAL_NO_ROOT_PATH \
  	__einfo_error ( EINFO_EINVAL_NO_ROOT_PATH )
  #define EINFO_EINVAL_NO_ROOT_PATH \
  	__einfo_uniqify ( EINFO_EINVAL, 0x03, "No root path" )
  #define EINVAL_NO_TARGET_IQN \
  	__einfo_error ( EINFO_EINVAL_NO_TARGET_IQN )
  #define EINFO_EINVAL_NO_TARGET_IQN \
  	__einfo_uniqify ( EINFO_EINVAL, 0x04, "No target IQN" )
  #define EINVAL_NO_INITIATOR_IQN \
  	__einfo_error ( EINFO_EINVAL_NO_INITIATOR_IQN )
  #define EINFO_EINVAL_NO_INITIATOR_IQN \
  	__einfo_uniqify ( EINFO_EINVAL, 0x05, "No initiator IQN" )
  #define EIO_TARGET_UNAVAILABLE \
  	__einfo_error ( EINFO_EIO_TARGET_UNAVAILABLE )
  #define EINFO_EIO_TARGET_UNAVAILABLE \
  	__einfo_uniqify ( EINFO_EIO, 0x01, "Target not currently operational" )
  #define EIO_TARGET_NO_RESOURCES \
  	__einfo_error ( EINFO_EIO_TARGET_NO_RESOURCES )
  #define EINFO_EIO_TARGET_NO_RESOURCES \
  	__einfo_uniqify ( EINFO_EIO, 0x02, "Target out of resources" )
  #define ENOTSUP_INITIATOR_STATUS \
  	__einfo_error ( EINFO_ENOTSUP_INITIATOR_STATUS )
  #define EINFO_ENOTSUP_INITIATOR_STATUS \
  	__einfo_uniqify ( EINFO_ENOTSUP, 0x01, "Unsupported initiator status" )
  #define ENOTSUP_OPCODE \
  	__einfo_error ( EINFO_ENOTSUP_OPCODE )
  #define EINFO_ENOTSUP_OPCODE \
  	__einfo_uniqify ( EINFO_ENOTSUP, 0x02, "Unsupported opcode" )
  #define ENOTSUP_DISCOVERY \
  	__einfo_error ( EINFO_ENOTSUP_DISCOVERY )
  #define EINFO_ENOTSUP_DISCOVERY \
  	__einfo_uniqify ( EINFO_ENOTSUP, 0x03, "Discovery not supported" )
  #define ENOTSUP_TARGET_STATUS \
  	__einfo_error ( EINFO_ENOTSUP_TARGET_STATUS )
  #define EINFO_ENOTSUP_TARGET_STATUS \
  	__einfo_uniqify ( EINFO_ENOTSUP, 0x04, "Unsupported target status" )
  #define ENOTSUP_NOP_IN \
  	__einfo_error ( EINFO_ENOTSUP_NOP_IN )
  #define EINFO_ENOTSUP_NOP_IN \
  	__einfo_uniqify ( EINFO_ENOTSUP, 0x05, "Unsupported NOP-In received" )
  #define EPERM_INITIATOR_AUTHENTICATION \
  	__einfo_error ( EINFO_EPERM_INITIATOR_AUTHENTICATION )
  #define EINFO_EPERM_INITIATOR_AUTHENTICATION \
  	__einfo_uniqify ( EINFO_EPERM, 0x01, "Initiator authentication failed" )
  #define EPERM_INITIATOR_AUTHORISATION \
  	__einfo_error ( EINFO_EPERM_INITIATOR_AUTHORISATION )
  #define EINFO_EPERM_INITIATOR_AUTHORISATION \
  	__einfo_uniqify ( EINFO_EPERM, 0x02, "Initiator not authorised" )
  #define EPROTO_INVALID_CHAP_ALGORITHM \
  	__einfo_error ( EINFO_EPROTO_INVALID_CHAP_ALGORITHM )
  #define EINFO_EPROTO_INVALID_CHAP_ALGORITHM \
  	__einfo_uniqify ( EINFO_EPROTO, 0x01, "Invalid CHAP algorithm" )
  #define EPROTO_INVALID_CHAP_IDENTIFIER \
  	__einfo_error ( EINFO_EPROTO_INVALID_CHAP_IDENTIFIER )
  #define EINFO_EPROTO_INVALID_CHAP_IDENTIFIER \
  	__einfo_uniqify ( EINFO_EPROTO, 0x02, "Invalid CHAP identifier" )
  #define EPROTO_INVALID_LARGE_BINARY \
  	__einfo_error ( EINFO_EPROTO_INVALID_LARGE_BINARY )
  #define EINFO_EPROTO_INVALID_LARGE_BINARY \
  	__einfo_uniqify ( EINFO_EPROTO, 0x03, "Invalid large binary" )
  #define EPROTO_INVALID_CHAP_RESPONSE \
  	__einfo_error ( EINFO_EPROTO_INVALID_CHAP_RESPONSE )
  #define EINFO_EPROTO_INVALID_CHAP_RESPONSE \
  	__einfo_uniqify ( EINFO_EPROTO, 0x04, "Invalid CHAP response" )
  
  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;
  }
  
  /**
   * 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;
  }
  
  /**
   * 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->initiator_iqn );
  	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->command );
  	free ( iscsi );
  }
  
  /**
   * Shut down iSCSI interface
   *
   * @v iscsi		iSCSI session
   * @v rc		Reason for close
   */
  static void iscsi_close ( struct iscsi_session *iscsi, int rc ) {
  
  	/* A TCP graceful close is still an error from our point of view */
  	if ( rc == 0 )
  		rc = -ECONNRESET;
  
  	DBGC ( iscsi, "iSCSI %p closed: %s\n", iscsi, strerror ( rc ) );
  
  	/* Stop transmission process */
  	process_del ( &iscsi->process );
  
  	/* Shut down interfaces */
  	intf_shutdown ( &iscsi->socket, rc );
  	intf_shutdown ( &iscsi->control, rc );
  	intf_shutdown ( &iscsi->data, rc );
  }
  
  /**
   * Assign new iSCSI initiator task tag
   *
   * @v iscsi		iSCSI session
   */
  static void iscsi_new_itt ( struct iscsi_session *iscsi ) {
  	static uint16_t itt_idx;
  
  	iscsi->itt = ( ISCSI_TAG_MAGIC | (++itt_idx) );
  }
  
  /**
   * 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 new ISID */
  	iscsi->isid_iana_qual = ( random() & 0xffff );
  
  	/* Assign fresh initiator task tag */
  	iscsi_new_itt ( iscsi );
  
  	/* 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 */
  	intf_restart ( &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
   * @v rsp		SCSI response, if any
   *
   * 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_scsi_command().  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,
  			      struct scsi_rsp *rsp ) {
  	uint32_t itt = iscsi->itt;
  
  	assert ( iscsi->tx_state == ISCSI_TX_IDLE );
  
  	/* Clear command */
  	free ( iscsi->command );
  	iscsi->command = NULL;
  
  	/* Send SCSI response, if any */
  	scsi_response ( &iscsi->data, rsp );
  
  	/* Close SCSI command, if this is still the same command.  (It
  	 * is possible that the command interface has already been
  	 * closed as a result of the SCSI response we sent.)
  	 */
  	if ( iscsi->itt == itt )
  		intf_restart ( &iscsi->data, rc );
  }
  
  /****************************************************************************
   *
   * 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 */
  	memcpy ( &command->lun, &iscsi->command->lun,
  		 sizeof ( command->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;
  	struct scsi_rsp rsp;
  	uint32_t residual_count;
  	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;
  
  	/* Parse SCSI response and discard buffer */
  	memset ( &rsp, 0, sizeof ( rsp ) );
  	rsp.status = response->status;
  	residual_count = ntohl ( response->residual_count );
  	if ( response->flags & ISCSI_DATA_FLAG_OVERFLOW ) {
  		rsp.overrun = residual_count;
  	} else if ( response->flags & ISCSI_DATA_FLAG_UNDERFLOW ) {
  		rsp.overrun = -(residual_count);
  	}
  	if ( ISCSI_DATA_LEN ( response->lengths ) )
  		memcpy ( &rsp.sense, ( iscsi->rx_buffer + 2 ),
  			 sizeof ( rsp.sense ) );
  	iscsi_rx_buffered_data_done ( iscsi );
  
  	/* Check for errors */
  	if ( response->response != ISCSI_RESPONSE_COMMAND_COMPLETE )
  		return -EIO;
  
  	/* Mark as completed */
  	iscsi_scsi_done ( iscsi, 0, &rsp );
  	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 cannot return an error status via a data-in */
  		iscsi_scsi_done ( iscsi, 0, NULL );
  	}
  
  	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->command->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 );
  }
  
  /**
   * Receive data segment of an iSCSI NOP-In
   *
   * @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_nop_in ( struct iscsi_session *iscsi,
  			     const void *data __unused, size_t len __unused,
  			     size_t remaining __unused ) {
  	struct iscsi_nop_in *nop_in = &iscsi->rx_bhs.nop_in;
  
  	DBGC2 ( iscsi, "iSCSI %p received NOP-In\n", iscsi );
  
  	/* We don't currently have the ability to respond to NOP-Ins
  	 * sent as ping requests, but we can happily accept NOP-Ins
  	 * sent merely to update CmdSN.
  	 */
  	if ( nop_in->ttt != htonl ( ISCSI_TAG_RESERVED ) ) {
  		DBGC ( iscsi, "iSCSI %p received unsupported NOP-In with TTT "
  		       "%08x\n", iscsi, ntohl ( nop_in->ttt ) );
  		return -ENOTSUP_NOP_IN;
  	}
  
  	return 0;
  }
  
  /****************************************************************************
   *
   * 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 [4]
   *     InitialR2T=Yes [1]
   *     ImmediateData is irrelevant; we never send immediate data [4]
   *     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.
   *
   * [4] We are quite happy to use the RFC-defined default values for
   * these parameters, but some targets (notably a QNAP TS-639Pro) fail
   * unless they are supplied, 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;
  	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 ) ) {
  		char buf[ base16_encoded_len ( iscsi->chap.response_len ) + 1 ];
  		assert ( iscsi->initiator_username != NULL );
  		base16_encode ( iscsi->chap.response, iscsi->chap.response_len,
  				buf );
  		used += ssnprintf ( data + used, len - used,
  				    "CHAP_N=%s%cCHAP_R=0x%s%c",
  				    iscsi->initiator_username, 0, buf, 0 );
  	}
  
  	if ( ( iscsi->status & ISCSI_STATUS_STRINGS_CHAP_CHALLENGE ) ) {
  		size_t challenge_len = ( sizeof ( iscsi->chap_challenge ) - 1 );
  		char buf[ base16_encoded_len ( challenge_len ) + 1 ];
  		base16_encode ( ( iscsi->chap_challenge + 1 ), challenge_len,
  				buf );
  		used += ssnprintf ( data + used, len - used,
  				    "CHAP_I=%d%cCHAP_C=0x%s%c",
  				    iscsi->chap_challenge[0], 0, buf, 0 );
  	}
  
  	if ( iscsi->status & ISCSI_STATUS_STRINGS_OPERATIONAL ) {
  		used += ssnprintf ( data + used, len - used,
  				    "HeaderDigest=None%c"
  				    "DataDigest=None%c"
  				    "MaxConnections=1%c"
  				    "InitialR2T=Yes%c"
  				    "ImmediateData=No%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, 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;
  
  	switch ( iscsi->status & ISCSI_LOGIN_CSG_MASK ) {
  	case ISCSI_LOGIN_CSG_SECURITY_NEGOTIATION:
  		DBGC ( iscsi, "iSCSI %p entering security negotiation\n",
  		       iscsi );
  		break;
  	case ISCSI_LOGIN_CSG_OPERATIONAL_NEGOTIATION:
  		DBGC ( iscsi, "iSCSI %p entering operational negotiation\n",
  		       iscsi );
  		break;
  	default:
  		assert ( 0 );
  	}
  
  	/* 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 );
  	request->isid_iana_qual = htons ( iscsi->isid_iana_qual );
  	/* tsih left as zero */
  	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 );
  }
  
  /**
   * Calculate maximum length of decoded large binary value
   *
   * @v encoded		Encoded large binary value
   * @v max_raw_len	Maximum length of raw data
   */
  static inline size_t
  iscsi_large_binary_decoded_max_len ( const char *encoded ) {
  	return ( strlen ( encoded ) ); /* Decoding never expands data */
  }
  
  /**
   * Decode large binary value
   *
   * @v encoded		Encoded large binary value
   * @v raw		Raw data
   * @ret len		Length of raw data, or negative error
   */
  static int iscsi_large_binary_decode ( const char *encoded, uint8_t *raw ) {
  
  	if ( encoded[0] != '0' )
  		return -EPROTO_INVALID_LARGE_BINARY;
  
  	switch ( encoded[1] ) {
  	case 'x' :
  	case 'X' :
  		return base16_decode ( ( encoded + 2 ), raw );
  	case 'b' :
  	case 'B' :
  		return base64_decode ( ( encoded + 2 ), raw );
  	default:
  		return -EPROTO_INVALID_LARGE_BINARY;
  	}
  }
  
  /**
   * 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_INVALID_CHAP_ALGORITHM;
  	}
  
  	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_INVALID_CHAP_IDENTIFIER;
  	}
  
  	/* 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 ) {
  	uint8_t buf[ iscsi_large_binary_decoded_max_len ( value ) ];
  	unsigned int i;
  	size_t len;
  	int rc;
  
  	/* Process challenge */
  	rc = iscsi_large_binary_decode ( value, buf );
  	if ( rc < 0 ) {
  		DBGC ( iscsi, "iSCSI %p invalid CHAP challenge \"%s\": %s\n",
  		       iscsi, value, strerror ( rc ) );
  		return rc;
  	}
  	len = rc;
  	chap_update ( &iscsi->chap, buf, len );
  
  	/* 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_INCORRECT_TARGET_USERNAME;
  	}
  
  	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 ) {
  	uint8_t buf[ iscsi_large_binary_decoded_max_len ( value ) ];
  	size_t len;
  	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 );
  
  	/* Process response */
  	rc = iscsi_large_binary_decode ( value, buf );
  	if ( rc < 0 ) {
  		DBGC ( iscsi, "iSCSI %p invalid CHAP response \"%s\": %s\n",
  		       iscsi, value, strerror ( rc ) );
  		return rc;
  	}
  	len = rc;
  
  	/* Check CHAP response */
  	if ( len != iscsi->chap.response_len ) {
  		DBGC ( iscsi, "iSCSI %p invalid CHAP response length\n",
  		       iscsi );
  		return -EPROTO_INVALID_CHAP_RESPONSE;
  	}
  	if ( memcmp ( buf, iscsi->chap.response, len ) != 0 ) {
  		DBGC ( iscsi, "iSCSI %p incorrect CHAP response \"%s\"\n",
  		       iscsi, value );
  		return -EACCES_INCORRECT_TARGET_PASSWORD;
  	}
  
  	/* 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;
  }
  
  /**
   * 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 -EPERM_INITIATOR_AUTHENTICATION;
  		case ISCSI_STATUS_INITIATOR_ERROR_AUTHORISATION :
  			return -EPERM_INITIATOR_AUTHORISATION;
  		case ISCSI_STATUS_INITIATOR_ERROR_NOT_FOUND :
  		case ISCSI_STATUS_INITIATOR_ERROR_REMOVED :
  			return -ENODEV;
  		default :
  			return -ENOTSUP_INITIATOR_STATUS;
  		}
  	case ISCSI_STATUS_TARGET_ERROR :
  		switch ( status_detail ) {
  		case ISCSI_STATUS_TARGET_ERROR_UNAVAILABLE:
  			return -EIO_TARGET_UNAVAILABLE;
  		case ISCSI_STATUS_TARGET_ERROR_NO_RESOURCES:
  			return -EIO_TARGET_NO_RESOURCES;
  		default:
  			return -ENOTSUP_TARGET_STATUS;
  		}
  	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 );
  		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;
  	}
  
  	/* Notify SCSI layer of window change */
  	DBGC ( iscsi, "iSCSI %p entering full feature phase\n", iscsi );
  	xfer_window_changed ( &iscsi->control );
  
  	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 );
  	assert ( ! process_running ( &iscsi->process ) );
  	
  	/* Initialise TX BHS */
  	memset ( &iscsi->tx_bhs, 0, sizeof ( iscsi->tx_bhs ) );
  
  	/* Flag TX engine to start transmitting */
  	iscsi->tx_state = ISCSI_TX_BHS;
  
  	/* Start transmission process */
  	process_add ( &iscsi->process );
  }
  
  /**
   * 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;
  
  	/* Stop transmission process */
  	process_del ( &iscsi->process );
  
  	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_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;
  		case ISCSI_TX_IDLE:
  			/* Stop processing */
  			iscsi_tx_done ( iscsi );
  			return;
  		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 ) );
  			/* Transmission errors are fatal */
  			iscsi_close ( iscsi, rc );
  			return;
  		}
  
  		/* Move to next state */
  		iscsi->tx_state = next_state;
  	}
  }
  
  /**
   * 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 );
  	case ISCSI_OPCODE_NOP_IN:
  		return iscsi_rx_nop_in ( iscsi, data, len, remaining );
  	default:
  		if ( remaining )
  			return 0;
  		DBGC ( iscsi, "iSCSI %p unknown opcode %02x\n", iscsi,
  		       response->opcode );
  		return -ENOTSUP_OPCODE;
  	}
  }
  
  /**
   * Receive new data
   *
   * @v iscsi		iSCSI session
   * @v iobuf		I/O buffer
   * @v meta		Data transfer metadata
   * @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 ( struct iscsi_session *iscsi,
  				  struct io_buffer *iobuf,
  				  struct xfer_metadata *meta __unused ) {
  	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 );
  			rc = -EINVAL;
  			goto done;
  		}
  
  		frag_len = iscsi->rx_len - iscsi->rx_offset;
  		if ( frag_len > iob_len ( iobuf ) )
  			frag_len = iob_len ( iobuf );
  		remaining = iscsi->rx_len - iscsi->rx_offset - frag_len;
  		if ( ( rc = rx ( iscsi, iobuf->data, frag_len,
  				 remaining ) ) != 0 ) {
  			DBGC ( iscsi, "iSCSI %p could not process received "
  			       "data: %s\n", iscsi, strerror ( rc ) );
  			goto done;
  		}
  
  		iscsi->rx_offset += frag_len;
  		iob_pull ( iobuf, 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 ) {
  			rc = 0;
  			goto done;
  		}
  
  		iscsi->rx_state = next_state;
  		iscsi->rx_offset = 0;
  	}
  
   done:
  	/* Free I/O buffer */
  	free_iob ( iobuf );
  
  	/* Destroy session on error */
  	if ( rc != 0 )
  		iscsi_close ( iscsi, rc );
  
  	return rc;
  }
  
  /**
   * Handle redirection event
   *
   * @v iscsi		iSCSI session
   * @v type		Location type
   * @v args		Remaining arguments depend upon location type
   * @ret rc		Return status code
   */
  static int iscsi_vredirect ( struct iscsi_session *iscsi, int type,
  			     va_list args ) {
  	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 ( &iscsi->socket, type, args );
  }
  
  /** iSCSI socket interface operations */
  static struct interface_operation iscsi_socket_operations[] = {
  	INTF_OP ( xfer_deliver, struct iscsi_session *, iscsi_socket_deliver ),
  	INTF_OP ( xfer_vredirect, struct iscsi_session *, iscsi_vredirect ),
  	INTF_OP ( intf_close, struct iscsi_session *, iscsi_close ),
  };
  
  /** iSCSI socket interface descriptor */
  static struct interface_descriptor iscsi_socket_desc =
  	INTF_DESC ( struct iscsi_session, socket, iscsi_socket_operations );
  
  /****************************************************************************
   *
   * iSCSI command issuing
   *
   */
  
  /**
   * Check iSCSI flow-control window
   *
   * @v iscsi		iSCSI session
   * @ret len		Length of window
   */
  static size_t iscsi_scsi_window ( struct iscsi_session *iscsi ) {
  
  	if ( ( ( iscsi->status & ISCSI_STATUS_PHASE_MASK ) ==
  	       ISCSI_STATUS_FULL_FEATURE_PHASE ) &&
  	     ( iscsi->command == NULL ) ) {
  		/* We cannot handle concurrent commands */
  		return 1;
  	} else {
  		return 0;
  	}
  }
  
  /**
   * Issue iSCSI SCSI command
   *
   * @v iscsi		iSCSI session
   * @v parent		Parent interface
   * @v command		SCSI command
   * @ret tag		Command tag, or negative error
   */
  static int iscsi_scsi_command ( struct iscsi_session *iscsi,
  				struct interface *parent,
  				struct scsi_cmd *command ) {
  
  	/* This iSCSI implementation cannot handle multiple concurrent
  	 * commands or commands arriving before login is complete.
  	 */
  	if ( iscsi_scsi_window ( iscsi ) == 0 ) {
  		DBGC ( iscsi, "iSCSI %p cannot handle concurrent commands\n",
  		       iscsi );
  		return -EOPNOTSUPP;
  	}
  
  	/* Store command */
  	iscsi->command = malloc ( sizeof ( *command ) );
  	if ( ! iscsi->command )
  		return -ENOMEM;
  	memcpy ( iscsi->command, command, sizeof ( *command ) );
  
  	/* Assign new ITT */
  	iscsi_new_itt ( iscsi );
  
  	/* Start sending command */
  	iscsi_start_command ( iscsi );
  
  	/* Attach to parent interface and return */
  	intf_plug_plug ( &iscsi->data, parent );
  	return iscsi->itt;
  }
  
  /** iSCSI SCSI command-issuing interface operations */
  static struct interface_operation iscsi_control_op[] = {
  	INTF_OP ( scsi_command, struct iscsi_session *, iscsi_scsi_command ),
  	INTF_OP ( xfer_window, struct iscsi_session *, iscsi_scsi_window ),
  	INTF_OP ( intf_close, struct iscsi_session *, iscsi_close ),
  	INTF_OP ( acpi_describe, struct iscsi_session *, ibft_describe ),
  };
  
  /** iSCSI SCSI command-issuing interface descriptor */
  static struct interface_descriptor iscsi_control_desc =
  	INTF_DESC ( struct iscsi_session, control, iscsi_control_op );
  
  /**
   * Close iSCSI command
   *
   * @v iscsi		iSCSI session
   * @v rc		Reason for close
   */
  static void iscsi_command_close ( struct iscsi_session *iscsi, int rc ) {
  
  	/* Restart interface */
  	intf_restart ( &iscsi->data, rc );
  
  	/* Treat unsolicited command closures mid-command as fatal,
  	 * because we have no code to handle partially-completed PDUs.
  	 */
  	if ( iscsi->command != NULL )
  		iscsi_close ( iscsi, ( ( rc == 0 ) ? -ECANCELED : rc ) );
  }
  
  /** iSCSI SCSI command interface operations */
  static struct interface_operation iscsi_data_op[] = {
  	INTF_OP ( intf_close, struct iscsi_session *, iscsi_command_close ),
  };
  
  /** iSCSI SCSI command interface descriptor */
  static struct interface_descriptor iscsi_data_desc =
  	INTF_DESC ( struct iscsi_session, data, iscsi_data_op );
  
  /****************************************************************************
   *
   * Instantiator
   *
   */
  
  /** iSCSI root path components (as per RFC4173) */
  enum iscsi_root_path_component {
  	RP_SERVERNAME = 0,
  	RP_PROTOCOL,
  	RP_PORT,
  	RP_LUN,
  	RP_TARGETNAME,
  	NUM_RP_COMPONENTS
  };
  
  /** iSCSI initiator IQN setting */
  struct setting initiator_iqn_setting __setting ( SETTING_SANBOOT_EXTRA ) = {
  	.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 ( SETTING_AUTH_EXTRA ) = {
  	.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 ( SETTING_AUTH_EXTRA ) = {
  	.name = "reverse-password",
  	.description = "Reverse password",
  	.tag = DHCP_EB_REVERSE_PASSWORD,
  	.type = &setting_type_string,
  };
  
  /**
   * 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_ROOT_PATH_TOO_SHORT;
  			}
  		}
  		*(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;
  }
  
  /**
   * Fetch iSCSI settings
   *
   * @v iscsi		iSCSI session
   * @ret rc		Return status code
   */
  static int iscsi_fetch_settings ( struct iscsi_session *iscsi ) {
  	char *hostname;
  	union uuid uuid;
  	int len;
  
  	/* Fetch relevant settings.  Don't worry about freeing on
  	 * error, since iscsi_free() will take care of that anyway.
  	 */
  	if ( ( len = fetch_string_setting_copy ( NULL, &username_setting,
  					  &iscsi->initiator_username ) ) < 0 ) {
  		DBGC ( iscsi, "iSCSI %p could not fetch username: %s\n",
  		       iscsi, strerror ( len ) );
  		return len;
  	}
  	if ( ( len = fetch_string_setting_copy ( NULL, &password_setting,
  					  &iscsi->initiator_password ) ) < 0 ) {
  		DBGC ( iscsi, "iSCSI %p could not fetch password: %s\n",
  		       iscsi, strerror ( len ) );
  		return len;
  	}
  	if ( ( len = fetch_string_setting_copy( NULL, &reverse_username_setting,
  					     &iscsi->target_username ) ) < 0 ) {
  		DBGC ( iscsi, "iSCSI %p could not fetch reverse username: %s\n",
  		       iscsi, strerror ( len ) );
  		return len;
  	}
  	if ( ( len = fetch_string_setting_copy( NULL, &reverse_password_setting,
  					     &iscsi->target_password ) ) < 0 ) {
  		DBGC ( iscsi, "iSCSI %p could not fetch reverse password: %s\n",
  		       iscsi, strerror ( len ) );
  		return len;
  	}
  
  	/* Find a suitable initiator name */
  	if ( ( len = fetch_string_setting_copy ( NULL, &initiator_iqn_setting,
  					       &iscsi->initiator_iqn ) ) < 0 ) {
  		DBGC ( iscsi, "iSCSI %p could not fetch initiator IQN: %s\n",
  		       iscsi, strerror ( len ) );
  		return len;
  	}
  	if ( iscsi->initiator_iqn )
  		return 0;
  	if ( ( len = fetch_string_setting_copy ( NULL, &hostname_setting,
  						&hostname ) ) < 0 ) {
  		DBGC ( iscsi, "iSCSI %p could not fetch hostname: %s\n",
  		       iscsi, strerror ( len ) );
  		return len;
  	}
  	if ( hostname ) {
  		len = asprintf ( &iscsi->initiator_iqn,
  				 ISCSI_DEFAULT_IQN_PREFIX ":%s", hostname );
  		free ( hostname );
  		if ( len < 0 ) {
  			DBGC ( iscsi, "iSCSI %p could not allocate initiator "
  			       "IQN\n", iscsi );
  			return -ENOMEM;
  		}
  		assert ( iscsi->initiator_iqn );
  		return 0;
  	}
  	if ( ( len = fetch_uuid_setting ( NULL, &uuid_setting, &uuid ) ) < 0 ) {
  		DBGC ( iscsi, "iSCSI %p has no suitable initiator IQN\n",
  		       iscsi );
  		return -EINVAL_NO_INITIATOR_IQN;
  	}
  	if ( ( len = asprintf ( &iscsi->initiator_iqn,
  				ISCSI_DEFAULT_IQN_PREFIX ":%s",
  				uuid_ntoa ( &uuid ) ) ) < 0 ) {
  		DBGC ( iscsi, "iSCSI %p could not allocate initiator IQN\n",
  		       iscsi );
  		return -ENOMEM;
  	}
  	assert ( iscsi->initiator_iqn );
  
  	return 0;
  }
  
  
  /**
   * Check iSCSI authentication details
   *
   * @v iscsi		iSCSI session
   * @ret rc		Return status code
   */
  static int iscsi_check_auth ( struct iscsi_session *iscsi ) {
  
  	/* Check for invalid authentication combinations */
  	if ( ( /* Initiator username without password (or vice-versa) */
  		( !! iscsi->initiator_username ) ^
  		( !! iscsi->initiator_password ) ) ||
  	     ( /* Target username without password (or vice-versa) */
  		( !! iscsi->target_username ) ^
  		( !! iscsi->target_password ) ) ||
  	     ( /* Target (reverse) without initiator (forward) */
  		( iscsi->target_username &&
  		  ( ! iscsi->initiator_username ) ) ) ) {
  		DBGC ( iscsi, "iSCSI %p invalid credentials: initiator "
  		       "%sname,%spw, target %sname,%spw\n", iscsi,
  		       ( iscsi->initiator_username ? "" : "no " ),
  		       ( iscsi->initiator_password ? "" : "no " ),
  		       ( iscsi->target_username ? "" : "no " ),
  		       ( iscsi->target_password ? "" : "no " ) );
  		return -EINVAL_BAD_CREDENTIAL_MIX;
  	}
  
  	return 0;
  }
  
  /**
   * Open iSCSI URI
   *
   * @v parent		Parent interface
   * @v uri		URI
   * @ret rc		Return status code
   */
  static int iscsi_open ( struct interface *parent, struct uri *uri ) {
  	struct iscsi_session *iscsi;
  	int rc;
  
  	/* Sanity check */
  	if ( ! uri->opaque ) {
  		rc = -EINVAL_NO_ROOT_PATH;
  		goto err_sanity_uri;
  	}
  
  	/* Allocate and initialise structure */
  	iscsi = zalloc ( sizeof ( *iscsi ) );
  	if ( ! iscsi ) {
  		rc = -ENOMEM;
  		goto err_zalloc;
  	}
  	ref_init ( &iscsi->refcnt, iscsi_free );
  	intf_init ( &iscsi->control, &iscsi_control_desc, &iscsi->refcnt );
  	intf_init ( &iscsi->data, &iscsi_data_desc, &iscsi->refcnt );
  	intf_init ( &iscsi->socket, &iscsi_socket_desc, &iscsi->refcnt );
  	process_init_stopped ( &iscsi->process, iscsi_tx_step,
  			       &iscsi->refcnt );
  
  	/* Parse root path */
  	if ( ( rc = iscsi_parse_root_path ( iscsi, uri->opaque ) ) != 0 )
  		goto err_parse_root_path;
  	/* Set fields not specified by root path */
  	if ( ( rc = iscsi_fetch_settings ( iscsi ) ) != 0 )
  		goto err_fetch_settings;
  	/* Validate authentication */
  	if ( ( rc = iscsi_check_auth ( iscsi ) ) != 0 )
  		goto err_check_auth;
  
  	/* Sanity checks */
  	if ( ! iscsi->target_address ) {
  		DBGC ( iscsi, "iSCSI %p does not yet support discovery\n",
  		       iscsi );
  		rc = -ENOTSUP_DISCOVERY;
  		goto err_sanity_address;
  	}
  	if ( ! iscsi->target_iqn ) {
  		DBGC ( iscsi, "iSCSI %p no target address supplied in %s\n",
  		       iscsi, uri->opaque );
  		rc = -EINVAL_NO_TARGET_IQN;
  		goto err_sanity_iqn;
  	}
  	DBGC ( iscsi, "iSCSI %p initiator %s\n",iscsi, iscsi->initiator_iqn );
  	DBGC ( iscsi, "iSCSI %p target %s %s\n",
  	       iscsi, iscsi->target_address, iscsi->target_iqn );
  
  	/* Open socket */
  	if ( ( rc = iscsi_open_connection ( iscsi ) ) != 0 )
  		goto err_open_connection;
  
  	/* Attach SCSI device to parent interface */
  	if ( ( rc = scsi_open ( parent, &iscsi->control,
  				&iscsi->lun ) ) != 0 ) {
  		DBGC ( iscsi, "iSCSI %p could not create SCSI device: %s\n",
  		       iscsi, strerror ( rc ) );
  		goto err_scsi_open;
  	}
  
  	/* Mortalise self, and return */
  	ref_put ( &iscsi->refcnt );
  	return 0;
  	
   err_scsi_open:
   err_open_connection:
   err_sanity_iqn:
   err_sanity_address:
   err_check_auth:
   err_fetch_settings:
   err_parse_root_path:
  	iscsi_close ( iscsi, rc );
  	ref_put ( &iscsi->refcnt );
   err_zalloc:
   err_sanity_uri:
  	return rc;
  }
  
  /** iSCSI URI opener */
  struct uri_opener iscsi_uri_opener __uri_opener = {
  	.scheme = "iscsi",
  	.open = iscsi_open,
  };
  