Decouple filter selection from channel construction

Allow plugins to extend the set of filters used by gRPC core:
- plugins at construction time can register against the 'channel_init' system to be allowed to mutate a new channel_stack_builder type
- channel_stack_builder provides a central and rather dynamic place to construct the list of filters required by a channel stack
- ultimately we construct the channel stack in the fashion we always have

This is also a prerequisite step to allowing filters to be implemented from wrapped languages.

2 files changed, 6 insertions, 2 deletions

diff --git a/src/core/transport/chttp2_transport.c b/src/core/transport/chttp2_transport.c
index 617d98875c..1901307d94 100644
--- a/src/core/transport/chttp2_transport.c
+++ b/src/core/transport/chttp2_transport.c
@@ -1713,8 +1713,9 @@ static char *chttp2_get_peer(grpc_exec_ctx *exec_ctx, grpc_transport *t) {
 }
 
 static const grpc_transport_vtable vtable = {
-    sizeof(grpc_chttp2_stream), init_stream, set_pollset, perform_stream_op,
-    perform_transport_op, destroy_stream, destroy_transport, chttp2_get_peer};
+    sizeof(grpc_chttp2_stream), "chttp2", init_stream, set_pollset,
+    perform_stream_op, perform_transport_op, destroy_stream, destroy_transport,
+    chttp2_get_peer};
 
 grpc_transport *grpc_create_chttp2_transport(
     grpc_exec_ctx *exec_ctx, const grpc_channel_args *channel_args,
diff --git a/src/core/transport/transport_impl.h b/src/core/transport/transport_impl.h
index 40bfb4b13a..16f7fd4d32 100644
--- a/src/core/transport/transport_impl.h
+++ b/src/core/transport/transport_impl.h
@@ -41,6 +41,9 @@ typedef struct grpc_transport_vtable {
      layers and initialized by the transport */
   size_t sizeof_stream; /* = sizeof(transport stream) */
 
+  /* name of this transport implementation */
+  const char *name;
+
   /* implementation of grpc_transport_init_stream */
   int (*init_stream)(grpc_exec_ctx *exec_ctx, grpc_transport *self,
                      grpc_stream *stream, grpc_stream_refcount *refcount,