[interface] Provide intf_insert() to insert a filter interface

Generalise the filter interface insertion logic from block_translate()
and expose as intf_insert(), allowing a filter interface to be
inserted on any existing interface.

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

3 files changed, 20 insertions, 3 deletions

diff --git a/src/core/blocktrans.c b/src/core/blocktrans.c
index 3f32f9c..f9dcb95 100644
--- a/src/core/blocktrans.c
+++ b/src/core/blocktrans.c
@@ -242,9 +242,7 @@ int block_translate ( struct interface *block, userptr_t buffer, size_t size ) {
 	}
 
 	/* Attach to interfaces, mortalise self, and return */
-	assert ( block->dest != &null_intf );
-	intf_plug_plug ( &blktrans->xfer, block->dest );
-	intf_plug_plug ( &blktrans->block, block );
+	intf_insert ( block, &blktrans->block, &blktrans->xfer );
 	ref_put ( &blktrans->refcnt );
 
 	DBGC2 ( blktrans, "BLKTRANS %p created", blktrans );
diff --git a/src/core/interface.c b/src/core/interface.c
index 05e7e47..34a4180 100644
--- a/src/core/interface.c
+++ b/src/core/interface.c
@@ -391,6 +391,23 @@ void intfs_restart ( int rc, ... ) {
 }
 
 /**
+ * Insert a filter interface
+ *
+ * @v intf		Object interface
+ * @v upper		Upper end of filter
+ * @v lower		Lower end of filter
+ */
+void intf_insert ( struct interface *intf, struct interface *upper,
+		   struct interface *lower ) {
+	struct interface *dest = intf->dest;
+
+	intf_get ( dest );
+	intf_plug_plug ( intf, upper );
+	intf_plug_plug ( lower, dest );
+	intf_put ( dest );
+}
+
+/**
  * Poke an object interface
  *
  * @v intf		Object interface
diff --git a/src/include/ipxe/interface.h b/src/include/ipxe/interface.h
index 9281aee..19f58a4 100644
--- a/src/include/ipxe/interface.h
+++ b/src/include/ipxe/interface.h
@@ -169,6 +169,8 @@ extern void intfs_shutdown ( int rc, ... ) __attribute__ (( sentinel ));
 extern void intf_restart ( struct interface *intf, int rc );
 extern void intfs_vrestart ( va_list intfs, int rc );
 extern void intfs_restart ( int rc, ... ) __attribute__ (( sentinel ));
+extern void intf_insert ( struct interface *intf, struct interface *upper,
+			  struct interface *lower );
 
 extern void intf_poke ( struct interface *intf,
 			void ( type ) ( struct interface *intf ) );