[interface] Convert all data-xfer interfaces to generic interfaces

Remove data-xfer as an interface type, and replace data-xfer
interfaces with generic interfaces supporting the data-xfer methods.

Filter interfaces (as used by the TLS layer) are handled using the
generic pass-through interface capability.  A side-effect of this is
that deliver_raw() no longer exists as a data-xfer method.  (In
practice this doesn't lose any efficiency, since there are no
instances within the current codebase where xfer_deliver_raw() is used
to pass data to an interface supporting the deliver_raw() method.)

Signed-off-by: Michael Brown <mcb30@ipxe.org>

4 files changed, 121 insertions, 195 deletions

diff --git a/src/net/tcp/ftp.c b/src/net/tcp/ftp.c
index 58794c8b2..957f05cc8 100644
--- a/src/net/tcp/ftp.c
+++ b/src/net/tcp/ftp.c
@@ -8,6 +8,7 @@
 #include <ipxe/socket.h>
 #include <ipxe/tcpip.h>
 #include <ipxe/in.h>
+#include <ipxe/iobuf.h>
 #include <ipxe/xfer.h>
 #include <ipxe/open.h>
 #include <ipxe/uri.h>
@@ -48,14 +49,14 @@ struct ftp_request {
 	/** Reference counter */
 	struct refcnt refcnt;
 	/** Data transfer interface */
-	struct xfer_interface xfer;
+	struct interface xfer;
 
 	/** URI being fetched */
 	struct uri *uri;
 	/** FTP control channel interface */
-	struct xfer_interface control;
+	struct interface control;
 	/** FTP data channel interface */
-	struct xfer_interface data;
+	struct interface data;
 
 	/** Current state */
 	enum ftp_state state;
@@ -95,12 +96,9 @@ static void ftp_done ( struct ftp_request *ftp, int rc ) {
 	DBGC ( ftp, "FTP %p completed (%s)\n", ftp, strerror ( rc ) );
 
 	/* Close all data transfer interfaces */
-	xfer_nullify ( &ftp->xfer );
-	xfer_close ( &ftp->xfer, rc );
-	xfer_nullify ( &ftp->control );
-	xfer_close ( &ftp->control, rc );
-	xfer_nullify ( &ftp->data );
-	xfer_close ( &ftp->data, rc );
+	intf_shutdown ( &ftp->data, rc );
+	intf_shutdown ( &ftp->control, rc );
+	intf_shutdown ( &ftp->xfer, rc );
 }
 
 /*****************************************************************************
@@ -167,26 +165,6 @@ static struct ftp_control_string ftp_strings[] = {
 };
 
 /**
- * Handle control channel being closed
- *
- * @v control		FTP control channel interface
- * @v rc		Reason for close
- *
- * When the control channel is closed, the data channel must also be
- * closed, if it is currently open.
- */
-static void ftp_control_close ( struct xfer_interface *control, int rc ) {
-	struct ftp_request *ftp =
-		container_of ( control, struct ftp_request, control );
-
-	DBGC ( ftp, "FTP %p control connection closed: %s\n",
-	       ftp, strerror ( rc ) );
-
-	/* Complete FTP operation */
-	ftp_done ( ftp, rc );
-}
-
-/**
  * Parse FTP byte sequence value
  *
  * @v text		Text string
@@ -298,23 +276,25 @@ static void ftp_reply ( struct ftp_request *ftp ) {
 /**
  * Handle new data arriving on FTP control channel
  *
- * @v control		FTP control channel interface
- * @v data		New data
- * @v len		Length of new data
+ * @v ftp		FTP request
+ * @v iob		I/O buffer
+ * @v meta		Data transfer metadata
+ * @ret rc		Return status code
  *
  * Data is collected until a complete line is received, at which point
  * its information is passed to ftp_reply().
  */
-static int ftp_control_deliver_raw ( struct xfer_interface *control,
-				     const void *data, size_t len ) {
-	struct ftp_request *ftp =
-		container_of ( control, struct ftp_request, control );
+static int ftp_control_deliver ( struct ftp_request *ftp,
+				 struct io_buffer *iobuf,
+				 struct xfer_metadata *meta __unused ) {
+	char *data = iobuf->data;
+	size_t len = iob_len ( iobuf );
 	char *recvbuf = ftp->recvbuf;
 	size_t recvsize = ftp->recvsize;
 	char c;
 	
 	while ( len-- ) {
-		c = * ( ( char * ) data++ );
+		c = *(data++);
 		switch ( c ) {
 		case '\r' :
 		case '\n' :
@@ -351,19 +331,22 @@ static int ftp_control_deliver_raw ( struct xfer_interface *control,
 	ftp->recvbuf = recvbuf;
 	ftp->recvsize = recvsize;
 
+	/* Free I/O buffer */
+	free_iob ( iobuf );
+
 	return 0;
 }
 
-/** FTP control channel operations */
-static struct xfer_interface_operations ftp_control_operations = {
-	.close		= ftp_control_close,
-	.vredirect	= xfer_vreopen,
-	.window		= unlimited_xfer_window,
-	.alloc_iob	= default_xfer_alloc_iob,
-	.deliver_iob	= xfer_deliver_as_raw,
-	.deliver_raw	= ftp_control_deliver_raw,
+/** FTP control channel interface operations */
+static struct interface_operation ftp_control_operations[] = {
+	INTF_OP ( xfer_deliver, struct ftp_request *, ftp_control_deliver ),
+	INTF_OP ( intf_close, struct ftp_request *, ftp_done ),
 };
 
+/** FTP control channel interface descriptor */
+static struct interface_descriptor ftp_control_desc =
+	INTF_DESC ( struct ftp_request, control, ftp_control_operations );
+
 /*****************************************************************************
  *
  * FTP data channel
@@ -373,7 +356,7 @@ static struct xfer_interface_operations ftp_control_operations = {
 /**
  * Handle FTP data channel being closed
  *
- * @v data		FTP data channel interface
+ * @v ftp		FTP request
  * @v rc		Reason for closure
  *
  * When the data channel is closed, the control channel should be left
@@ -382,9 +365,7 @@ static struct xfer_interface_operations ftp_control_operations = {
  *
  * If the data channel is closed due to an error, we abort the request.
  */
-static void ftp_data_closed ( struct xfer_interface *data, int rc ) {
-	struct ftp_request *ftp =
-		container_of ( data, struct ftp_request, data );
+static void ftp_data_closed ( struct ftp_request *ftp, int rc ) {
 
 	DBGC ( ftp, "FTP %p data connection closed: %s\n",
 	       ftp, strerror ( rc ) );
@@ -400,16 +381,14 @@ static void ftp_data_closed ( struct xfer_interface *data, int rc ) {
 /**
  * Handle data delivery via FTP data channel
  *
- * @v xfer		FTP data channel interface
+ * @v ftp		FTP request
  * @v iobuf		I/O buffer
  * @v meta		Data transfer metadata
  * @ret rc		Return status code
  */
-static int ftp_data_deliver_iob ( struct xfer_interface *data,
-				  struct io_buffer *iobuf,
-				  struct xfer_metadata *meta __unused ) {
-	struct ftp_request *ftp =
-		container_of ( data, struct ftp_request, data );
+static int ftp_data_deliver ( struct ftp_request *ftp,
+			      struct io_buffer *iobuf,
+			      struct xfer_metadata *meta __unused ) {
 	int rc;
 
 	if ( ( rc = xfer_deliver_iob ( &ftp->xfer, iobuf ) ) != 0 ) {
@@ -421,48 +400,31 @@ static int ftp_data_deliver_iob ( struct xfer_interface *data,
 	return 0;
 }
 
-/** FTP data channel operations */
-static struct xfer_interface_operations ftp_data_operations = {
-	.close		= ftp_data_closed,
-	.vredirect	= xfer_vreopen,
-	.window		= unlimited_xfer_window,
-	.alloc_iob	= default_xfer_alloc_iob,
-	.deliver_iob	= ftp_data_deliver_iob,
-	.deliver_raw	= xfer_deliver_as_iob,
+/** FTP data channel interface operations */
+static struct interface_operation ftp_data_operations[] = {
+	INTF_OP ( xfer_deliver, struct ftp_request *, ftp_data_deliver ),
+	INTF_OP ( intf_close, struct ftp_request *, ftp_data_closed ),
 };
 
+/** FTP data channel interface descriptor */
+static struct interface_descriptor ftp_data_desc =
+	INTF_DESC ( struct ftp_request, data, ftp_data_operations );
+
 /*****************************************************************************
  *
  * Data transfer interface
  *
  */
 
-/**
- * Close FTP data transfer interface
- *
- * @v xfer		FTP data transfer interface
- * @v rc		Reason for close
- */
-static void ftp_xfer_closed ( struct xfer_interface *xfer, int rc ) {
-	struct ftp_request *ftp =
-		container_of ( xfer, struct ftp_request, xfer );
-
-	DBGC ( ftp, "FTP %p data transfer interface closed: %s\n",
-	       ftp, strerror ( rc ) );
-	
-	ftp_done ( ftp, rc );
-}
-
 /** FTP data transfer interface operations */
-static struct xfer_interface_operations ftp_xfer_operations = {
-	.close		= ftp_xfer_closed,
-	.vredirect	= ignore_xfer_vredirect,
-	.window		= unlimited_xfer_window,
-	.alloc_iob	= default_xfer_alloc_iob,
-	.deliver_iob	= xfer_deliver_as_raw,
-	.deliver_raw	= ignore_xfer_deliver_raw,
+static struct interface_operation ftp_xfer_operations[] = {
+	INTF_OP ( intf_close, struct ftp_request *, ftp_done ),
 };
 
+/** FTP data transfer interface descriptor */
+static struct interface_descriptor ftp_xfer_desc =
+	INTF_DESC ( struct ftp_request, xfer, ftp_xfer_operations );
+
 /*****************************************************************************
  *
  * URI opener
@@ -476,7 +438,7 @@ static struct xfer_interface_operations ftp_xfer_operations = {
  * @v uri		Uniform Resource Identifier
  * @ret rc		Return status code
  */
-static int ftp_open ( struct xfer_interface *xfer, struct uri *uri ) {
+static int ftp_open ( struct interface *xfer, struct uri *uri ) {
 	struct ftp_request *ftp;
 	struct sockaddr_tcpip server;
 	int rc;
@@ -492,10 +454,10 @@ static int ftp_open ( struct xfer_interface *xfer, struct uri *uri ) {
 	if ( ! ftp )
 		return -ENOMEM;
 	ref_init ( &ftp->refcnt, ftp_free );
-	xfer_init ( &ftp->xfer, &ftp_xfer_operations, &ftp->refcnt );
+	intf_init ( &ftp->xfer, &ftp_xfer_desc, &ftp->refcnt );
+	intf_init ( &ftp->control, &ftp_control_desc, &ftp->refcnt );
+	intf_init ( &ftp->data, &ftp_data_desc, &ftp->refcnt );
 	ftp->uri = uri_get ( uri );
-	xfer_init ( &ftp->control, &ftp_control_operations, &ftp->refcnt );
-	xfer_init ( &ftp->data, &ftp_data_operations, &ftp->refcnt );
 	ftp->recvbuf = ftp->status_text;
 	ftp->recvsize = sizeof ( ftp->status_text ) - 1;
 
@@ -510,7 +472,7 @@ static int ftp_open ( struct xfer_interface *xfer, struct uri *uri ) {
 		goto err;
 
 	/* Attach to parent interface, mortalise self, and return */
-	xfer_plug_plug ( &ftp->xfer, xfer );
+	intf_plug_plug ( &ftp->xfer, xfer );
 	ref_put ( &ftp->refcnt );
 	return 0;
 
diff --git a/src/net/tcp/http.c b/src/net/tcp/http.c
index d6a9fad7e..13c500d50 100644
--- a/src/net/tcp/http.c
+++ b/src/net/tcp/http.c
@@ -64,12 +64,12 @@ struct http_request {
 	/** Reference count */
 	struct refcnt refcnt;
 	/** Data transfer interface */
-	struct xfer_interface xfer;
+	struct interface xfer;
 
 	/** URI being fetched */
 	struct uri *uri;
 	/** Transport layer interface */
-	struct xfer_interface socket;
+	struct interface socket;
 
 	/** TX process */
 	struct process process;
@@ -125,10 +125,8 @@ static void http_done ( struct http_request *http, int rc ) {
 	process_del ( &http->process );
 
 	/* Close all data transfer interfaces */
-	xfer_nullify ( &http->socket );
-	xfer_close ( &http->socket, rc );
-	xfer_nullify ( &http->xfer );
-	xfer_close ( &http->xfer, rc );
+	intf_shutdown ( &http->socket, rc );
+	intf_shutdown ( &http->xfer, rc );
 }
 
 /**
@@ -349,16 +347,14 @@ static int http_rx_data ( struct http_request *http,
 /**
  * Handle new data arriving via HTTP connection
  *
- * @v socket		Transport layer interface
+ * @v http		HTTP request
  * @v iobuf		I/O buffer
  * @v meta		Data transfer metadata
  * @ret rc		Return status code
  */
-static int http_socket_deliver_iob ( struct xfer_interface *socket,
-				     struct io_buffer *iobuf,
-				     struct xfer_metadata *meta __unused ) {
-	struct http_request *http =
-		container_of ( socket, struct http_request, socket );
+static int http_socket_deliver ( struct http_request *http,
+				 struct io_buffer *iobuf,
+				 struct xfer_metadata *meta __unused ) {
 	struct http_line_handler *lh;
 	char *line;
 	ssize_t len;
@@ -469,58 +465,25 @@ static void http_step ( struct process *process ) {
 	}
 }
 
-/**
- * HTTP connection closed by network stack
- *
- * @v socket		Transport layer interface
- * @v rc		Reason for close
- */
-static void http_socket_close ( struct xfer_interface *socket, int rc ) {
-	struct http_request *http =
-		container_of ( socket, struct http_request, socket );
-
-	DBGC ( http, "HTTP %p socket closed: %s\n",
-	       http, strerror ( rc ) );
-	
-	http_done ( http, rc );
-}
-
-/** HTTP socket operations */
-static struct xfer_interface_operations http_socket_operations = {
-	.close		= http_socket_close,
-	.vredirect	= xfer_vreopen,
-	.window		= unlimited_xfer_window,
-	.alloc_iob	= default_xfer_alloc_iob,
-	.deliver_iob	= http_socket_deliver_iob,
-	.deliver_raw	= xfer_deliver_as_iob,
+/** HTTP socket interface operations */
+static struct interface_operation http_socket_operations[] = {
+	INTF_OP ( xfer_deliver, struct http_request *, http_socket_deliver ),
+	INTF_OP ( intf_close, struct http_request *, http_done ),
 };
 
-/**
- * Close HTTP data transfer interface
- *
- * @v xfer		Data transfer interface
- * @v rc		Reason for close
- */
-static void http_xfer_close ( struct xfer_interface *xfer, int rc ) {
-	struct http_request *http =
-		container_of ( xfer, struct http_request, xfer );
-
-	DBGC ( http, "HTTP %p interface closed: %s\n",
-	       http, strerror ( rc ) );
-
-	http_done ( http, rc );
-}
+/** HTTP socket interface descriptor */
+static struct interface_descriptor http_socket_desc =
+	INTF_DESC ( struct http_request, socket, http_socket_operations );
 
 /** HTTP data transfer interface operations */
-static struct xfer_interface_operations http_xfer_operations = {
-	.close		= http_xfer_close,
-	.vredirect	= ignore_xfer_vredirect,
-	.window		= unlimited_xfer_window,
-	.alloc_iob	= default_xfer_alloc_iob,
-	.deliver_iob	= xfer_deliver_as_raw,
-	.deliver_raw	= ignore_xfer_deliver_raw,
+static struct interface_operation http_xfer_operations[] = {
+	INTF_OP ( intf_close, struct http_request *, http_done ),
 };
 
+/** HTTP data transfer interface descriptor */
+static struct interface_descriptor http_xfer_desc =
+	INTF_DESC ( struct http_request, xfer, http_xfer_operations );
+
 /**
  * Initiate an HTTP connection, with optional filter
  *
@@ -530,13 +493,13 @@ static struct xfer_interface_operations http_xfer_operations = {
  * @v filter		Filter to apply to socket, or NULL
  * @ret rc		Return status code
  */
-int http_open_filter ( struct xfer_interface *xfer, struct uri *uri,
+int http_open_filter ( struct interface *xfer, struct uri *uri,
 		       unsigned int default_port,
-		       int ( * filter ) ( struct xfer_interface *xfer,
-					  struct xfer_interface **next ) ) {
+		       int ( * filter ) ( struct interface *xfer,
+					  struct interface **next ) ) {
 	struct http_request *http;
 	struct sockaddr_tcpip server;
-	struct xfer_interface *socket;
+	struct interface *socket;
 	int rc;
 
 	/* Sanity checks */
@@ -548,9 +511,9 @@ int http_open_filter ( struct xfer_interface *xfer, struct uri *uri,
 	if ( ! http )
 		return -ENOMEM;
 	ref_init ( &http->refcnt, http_free );
-	xfer_init ( &http->xfer, &http_xfer_operations, &http->refcnt );
+	intf_init ( &http->xfer, &http_xfer_desc, &http->refcnt );
        	http->uri = uri_get ( uri );
-	xfer_init ( &http->socket, &http_socket_operations, &http->refcnt );
+	intf_init ( &http->socket, &http_socket_desc, &http->refcnt );
 	process_init ( &http->process, http_step, &http->refcnt );
 
 	/* Open socket */
@@ -567,7 +530,7 @@ int http_open_filter ( struct xfer_interface *xfer, struct uri *uri,
 		goto err;
 
 	/* Attach to parent interface, mortalise self, and return */
-	xfer_plug_plug ( &http->xfer, xfer );
+	intf_plug_plug ( &http->xfer, xfer );
 	ref_put ( &http->refcnt );
 	return 0;
 
@@ -586,7 +549,7 @@ int http_open_filter ( struct xfer_interface *xfer, struct uri *uri,
  * @v uri		Uniform Resource Identifier
  * @ret rc		Return status code
  */
-static int http_open ( struct xfer_interface *xfer, struct uri *uri ) {
+static int http_open ( struct interface *xfer, struct uri *uri ) {
 	return http_open_filter ( xfer, uri, HTTP_PORT, NULL );
 }
 
diff --git a/src/net/tcp/https.c b/src/net/tcp/https.c
index b738f4167..805d108bb 100644
--- a/src/net/tcp/https.c
+++ b/src/net/tcp/https.c
@@ -40,7 +40,7 @@ FEATURE ( FEATURE_PROTOCOL, "HTTPS", DHCP_EB_FEATURE_HTTPS, 1 );
  * @v uri		Uniform Resource Identifier
  * @ret rc		Return status code
  */
-static int https_open ( struct xfer_interface *xfer, struct uri *uri ) {
+static int https_open ( struct interface *xfer, struct uri *uri ) {
 	return http_open_filter ( xfer, uri, HTTPS_PORT, add_tls );
 }
 
diff --git a/src/net/tcp/iscsi.c b/src/net/tcp/iscsi.c
index 24cbda2c5..80c63a6b1 100644
--- a/src/net/tcp/iscsi.c
+++ b/src/net/tcp/iscsi.c
@@ -27,6 +27,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #include <byteswap.h>
 #include <ipxe/vsprintf.h>
 #include <ipxe/socket.h>
+#include <ipxe/iobuf.h>
 #include <ipxe/xfer.h>
 #include <ipxe/open.h>
 #include <ipxe/scsi.h>
@@ -199,7 +200,7 @@ static int iscsi_open_connection ( struct iscsi_session *iscsi ) {
 static void iscsi_close_connection ( struct iscsi_session *iscsi, int rc ) {
 
 	/* Close all data transfer interfaces */
-	xfer_close ( &iscsi->socket, rc );
+	intf_restart ( &iscsi->socket, rc );
 
 	/* Clear connection status */
 	iscsi->status = 0;
@@ -1435,9 +1436,9 @@ static int iscsi_rx_data ( struct iscsi_session *iscsi, const void *data,
 /**
  * Receive new data
  *
- * @v socket		Transport layer interface
- * @v data		Received data
- * @v len		Length of received 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
@@ -1447,10 +1448,9 @@ static int iscsi_rx_data ( struct iscsi_session *iscsi, const void *data,
  * 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 );
+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 );
@@ -1483,48 +1483,52 @@ static int iscsi_socket_deliver_raw ( struct xfer_interface *socket,
 			break;
 		default:
 			assert ( 0 );
-			return -EINVAL;
+			rc = -EINVAL;
+			goto done;
 		}
 
 		frag_len = iscsi->rx_len - iscsi->rx_offset;
-		if ( frag_len > len )
-			frag_len = len;
+		if ( frag_len > iob_len ( iobuf ) )
+			frag_len = iob_len ( iobuf );
 		remaining = iscsi->rx_len - iscsi->rx_offset - frag_len;
-		if ( ( rc = rx ( iscsi, data, frag_len, remaining ) ) != 0 ) {
+		if ( ( rc = rx ( iscsi, iobuf->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;
+			goto done;
 		}
 
 		iscsi->rx_offset += frag_len;
-		data += frag_len;
-		len -= 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 )
-			return 0;
+		if ( iscsi->rx_offset != iscsi->rx_len ) {
+			rc = 0;
+			goto done;
+		}
 
 		iscsi->rx_state = next_state;
 		iscsi->rx_offset = 0;
 	}
 
-	return 0;
+ done:
+	/* Free I/O buffer */
+	free_iob ( iobuf );
+	return rc;
 }
 
 /**
  * Handle stream connection closure
  *
- * @v socket		Transport layer interface
+ * @v iscsi		iSCSI session
  * @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 );
+static void iscsi_socket_close ( struct iscsi_session *iscsi, int rc ) {
 
 	/* Even a graceful close counts as an error for iSCSI */
 	if ( ! rc )
@@ -1552,15 +1556,13 @@ static void iscsi_socket_close ( struct xfer_interface *socket, int rc ) {
 /**
  * Handle redirection event
  *
- * @v socket		Transport layer interface
+ * @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 xfer_interface *socket, int type,
+static int iscsi_vredirect ( struct iscsi_session *iscsi, int type,
 			     va_list args ) {
-	struct iscsi_session *iscsi =
-		container_of ( socket, struct iscsi_session, socket );
 	va_list tmp;
 	struct sockaddr *peer;
 
@@ -1578,20 +1580,20 @@ static int iscsi_vredirect ( struct xfer_interface *socket, int type,
 		va_end ( tmp );
 	}
 
-	return xfer_vreopen ( socket, type, args );
+	return xfer_vreopen ( &iscsi->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 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_socket_close ),
 };
 
+/** iSCSI socket interface descriptor */
+static struct interface_descriptor iscsi_socket_desc =
+	INTF_DESC ( struct iscsi_session, socket, iscsi_socket_operations );
 
 /****************************************************************************
  *
@@ -1641,7 +1643,6 @@ 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;
@@ -1793,7 +1794,7 @@ int iscsi_attach ( struct scsi_device *scsi, const char *root_path ) {
 	if ( ! iscsi )
 		return -ENOMEM;
 	ref_init ( &iscsi->refcnt, iscsi_free );
-	xfer_init ( &iscsi->socket, &iscsi_socket_operations, &iscsi->refcnt );
+	intf_init ( &iscsi->socket, &iscsi_socket_desc, &iscsi->refcnt );
 	process_init ( &iscsi->process, iscsi_tx_step, &iscsi->refcnt );
 
 	/* Parse root path */