[interface] Allow for non-pass-through interface methods

xfer_vredirect() should not be allowed to propagate to a pass-through
interface.  For example, when an HTTPS connection is opened, the
redirect message should cause the TLS layer to reopen the TCP socket,
rather than causing the HTTP layer to disconnect from the TLS layer.

Fix by allowing for non-pass-through interface methods, and setting
xfer_vredirect() to be one such method.

This is slightly ugly, in that it complicates the notion of an
interface method call by adding a "pass-through" / "non-pass-through"
piece of metadata.  However, the only current user of xfer_vredirect()
is iscsi.c, which uses it only because we don't yet have an
ioctl()-style call for retrieving the underlying socket address.
The new interface infrastructure allows for such a call to be created,
at which time this sole user of xfer_vredirect() can be removed,
xfer_vredirect() can cease to be an interface method and become simply
a wrapper around xfer_vreopen(), and the concept of a non-pass-through
interface method can be reverted.

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

src/core/interface.c

 }
 
 /**
- * Get object interface destination and operation method
+ * Get object interface destination and operation method (without pass-through)
  *
  * @v intf		Object interface
  * @v type		Operation type
  * @ret dest		Destination interface
  * @ret func		Implementing method, or NULL
  */
-void * intf_get_dest_op_untyped ( struct interface *intf, void *type,
-				  struct interface **dest ) {
+void * intf_get_dest_op_no_passthru_untyped ( struct interface *intf,
+					      void *type,
+					      struct interface **dest ) {
 	struct interface_descriptor *desc;
 	struct interface_operation *op;
 	unsigned int i;
 
+	*dest = intf_get ( intf->dest );
+	desc = (*dest)->desc;
+	for ( i = desc->num_op, op = desc->op ; i ; i--, op++ ) {
+		if ( op->type == type )
+			return op->func;
+	}
+
+	return NULL;
+}
+
+/**
+ * Get object interface destination and operation method
+ *
+ * @v intf		Object interface
+ * @v type		Operation type
+ * @ret dest		Destination interface
+ * @ret func		Implementing method, or NULL
+ */
+void * intf_get_dest_op_untyped ( struct interface *intf, void *type,
+				  struct interface **dest ) {
+	void *func;
+
 	while ( 1 ) {
+
 		/* Search for an implementing method provided by the
 		 * current destination interface.
 		 */
-		*dest = intf_get ( intf->dest );
-		desc = (*dest)->desc;
-		for ( i = desc->num_op, op = desc->op ; i ; i--, op++ ) {
-			if ( op->type == type )
-				return op->func;
-		}
+		func = intf_get_dest_op_no_passthru_untyped( intf, type, dest );
+		if ( func )
+			return func;
 
 		/* Pass through to the underlying interface, if applicable */
 		if ( ! ( intf = intf_get_passthru ( *dest ) ) )

src/core/xfer.c

 int xfer_vredirect ( struct interface *intf, int type, va_list args ) {
 	struct interface *dest;
 	xfer_vredirect_TYPE ( void * ) *op =
-		intf_get_dest_op ( intf, xfer_vredirect, &dest );
+		intf_get_dest_op_no_passthru ( intf, xfer_vredirect, &dest );
 	void *object = intf_object ( dest );
 	int rc;
 

src/include/ipxe/interface.h

 extern struct interface * intf_get ( struct interface *intf );
 extern void intf_put ( struct interface *intf );
 extern void * __attribute__ (( pure )) intf_object ( struct interface *intf );
+extern void * intf_get_dest_op_no_passthru_untyped ( struct interface *intf,
+						     void *type,
+						     struct interface **dest );
 extern void * intf_get_dest_op_untyped ( struct interface *intf, void *type,
 					 struct interface **dest );
 
 		.desc = &(descriptor),		\
 	}
 
+/**
+ * Get object interface destination and operation method (without pass-through)
+ *
+ * @v intf		Object interface
+ * @v type		Operation type
+ * @ret dest		Destination interface
+ * @ret func		Implementing method, or NULL
+ */
+#define intf_get_dest_op_no_passthru( intf, type, dest )		\
+	( ( type ## _TYPE ( void * ) * )				\
+	  intf_get_dest_op_no_passthru_untyped ( intf, type, dest ) )
+
 /**
  * Get object interface destination and operation method
  *