diff --git a/rapide/rapide.go b/rapide/rapide.go
index 6d76a9254b..c5f34fbdca 100644
--- a/rapide/rapide.go
+++ b/rapide/rapide.go
@@ -28,6 +28,24 @@ type ClosableBlockIterator interface {
 	blocks.BlockIterator
 }
 
+type ClientDrivenDownloader interface {
+	// Download must be asynchronous. It schedule a block to be downloaded and
+	// callback to be called when either it failed or succeeded.
+	// Clients need to callback when they have blocks or error.
+	// In the callback either []byte != nil and error == nil or error != nil and []byte == nil.
+	// When a callback for a cid is called the CID is cancel regardless of the success.
+	// The callback is expected to be really fast and should be called synchronously.
+	// All callbacks are threadsafe and may be called concurrently. But consumers
+	// must not go out of their way to call them concurrently. Just do whatever
+	// your underlying impl already do.
+	Download(cid.Cid, func([]byte, error))
+
+	// Cancel indicates that we are no longer intrested in a particular block.
+	// The callback is still allowed to be called again but that really not advised.
+	// It would be nice if consumers freed the callback in the short term after this is called.
+	Cancel(cid.Cid)
+}
+
 // A Client is a collection of routers and protocols that can be used to do requests.
 type Client struct {
 	ServerDrivenDownloaders []ServerDrivenDownloader