5 files changed, 17 insertions, 7 deletions

diff --git a/src/core/lib/channel/channel_stack.c b/src/core/lib/channel/channel_stack.c
index 5c161652ac..bbba85d80b 100644
--- a/src/core/lib/channel/channel_stack.c
+++ b/src/core/lib/channel/channel_stack.c
@@ -106,6 +106,7 @@ void grpc_channel_stack_init(grpc_exec_ctx *exec_ctx, int initial_refs,
                              const grpc_channel_filter **filters,
                              size_t filter_count,
                              const grpc_channel_args *channel_args,
+                             grpc_transport *optional_transport,
                              const char *name, grpc_channel_stack *stack) {
   size_t call_size =
       ROUND_UP_TO_ALIGNMENT_SIZE(sizeof(grpc_call_stack)) +
@@ -127,6 +128,7 @@ void grpc_channel_stack_init(grpc_exec_ctx *exec_ctx, int initial_refs,
   for (i = 0; i < filter_count; i++) {
     args.channel_stack = stack;
     args.channel_args = channel_args;
+    args.optional_transport = optional_transport;
     args.is_first = i == 0;
     args.is_last = i == (filter_count - 1);
     elems[i].filter = filters[i];
diff --git a/src/core/lib/channel/channel_stack.h b/src/core/lib/channel/channel_stack.h
index 3ca643c893..41dd4a0d8a 100644
--- a/src/core/lib/channel/channel_stack.h
+++ b/src/core/lib/channel/channel_stack.h
@@ -60,6 +60,8 @@ typedef struct grpc_call_stack grpc_call_stack;
 typedef struct {
   grpc_channel_stack *channel_stack;
   const grpc_channel_args *channel_args;
+  /** Transport, iff it is known */
+  grpc_transport *optional_transport;
   int is_first;
   int is_last;
 } grpc_channel_element_args;
@@ -198,6 +200,7 @@ void grpc_channel_stack_init(grpc_exec_ctx *exec_ctx, int initial_refs,
                              grpc_iomgr_cb_func destroy, void *destroy_arg,
                              const grpc_channel_filter **filters,
                              size_t filter_count, const grpc_channel_args *args,
+                             grpc_transport *optional_transport,
                              const char *name, grpc_channel_stack *stack);
 /* Destroy a channel stack */
 void grpc_channel_stack_destroy(grpc_exec_ctx *exec_ctx,
diff --git a/src/core/lib/channel/channel_stack_builder.c b/src/core/lib/channel/channel_stack_builder.c
index a8646c9565..eda4968f48 100644
--- a/src/core/lib/channel/channel_stack_builder.c
+++ b/src/core/lib/channel/channel_stack_builder.c
@@ -257,8 +257,8 @@ void *grpc_channel_stack_builder_finish(grpc_exec_ctx *exec_ctx,
   // and initialize it
   grpc_channel_stack_init(exec_ctx, initial_refs, destroy,
                           destroy_arg == NULL ? result : destroy_arg, filters,
-                          num_filters, builder->args, builder->name,
-                          channel_stack);
+                          num_filters, builder->args, builder->transport,
+                          builder->name, channel_stack);
 
   // run post-initialization functions
   i = 0;
diff --git a/src/core/lib/channel/http_client_filter.c b/src/core/lib/channel/http_client_filter.c
index 2245a52599..792f0d8ae6 100644
--- a/src/core/lib/channel/http_client_filter.c
+++ b/src/core/lib/channel/http_client_filter.c
@@ -38,6 +38,7 @@
 #include "src/core/lib/profiling/timers.h"
 #include "src/core/lib/support/string.h"
 #include "src/core/lib/transport/static_metadata.h"
+#include "src/core/lib/transport/transport_impl.h"
 
 #define EXPECTED_CONTENT_TYPE "application/grpc"
 #define EXPECTED_CONTENT_TYPE_LENGTH sizeof(EXPECTED_CONTENT_TYPE) - 1
@@ -199,7 +200,8 @@ static grpc_mdelem *scheme_from_args(const grpc_channel_args *args) {
   return GRPC_MDELEM_SCHEME_HTTP;
 }
 
-static grpc_mdstr *user_agent_from_args(const grpc_channel_args *args) {
+static grpc_mdstr *user_agent_from_args(const grpc_channel_args *args,
+                                        const char *transport_name) {
   gpr_strvec v;
   size_t i;
   int is_first = 1;
@@ -221,8 +223,8 @@ static grpc_mdstr *user_agent_from_args(const grpc_channel_args *args) {
     }
   }
 
-  gpr_asprintf(&tmp, "%sgrpc-c/%s (%s)", is_first ? "" : " ",
-               grpc_version_string(), GPR_PLATFORM_STRING);
+  gpr_asprintf(&tmp, "%sgrpc-c/%s (%s; %s)", is_first ? "" : " ",
+               grpc_version_string(), GPR_PLATFORM_STRING, transport_name);
   is_first = 0;
   gpr_strvec_add(&v, tmp);
 
@@ -253,9 +255,12 @@ static void init_channel_elem(grpc_exec_ctx *exec_ctx,
                               grpc_channel_element_args *args) {
   channel_data *chand = elem->channel_data;
   GPR_ASSERT(!args->is_last);
+  GPR_ASSERT(args->optional_transport != NULL);
   chand->static_scheme = scheme_from_args(args->channel_args);
   chand->user_agent = grpc_mdelem_from_metadata_strings(
-      GRPC_MDSTR_USER_AGENT, user_agent_from_args(args->channel_args));
+      GRPC_MDSTR_USER_AGENT,
+      user_agent_from_args(args->channel_args,
+                           args->optional_transport->vtable->name));
 }
 
 /* Destructor for channel data */
diff --git a/src/core/lib/channel/http_client_filter.h b/src/core/lib/channel/http_client_filter.h
index a884b36318..47081175ea 100644
--- a/src/core/lib/channel/http_client_filter.h
+++ b/src/core/lib/channel/http_client_filter.h
@@ -1,5 +1,4 @@
 /*
- *
  * Copyright 2015, Google Inc.
  * All rights reserved.
  *
@@ -39,6 +38,7 @@
 /* Processes metadata on the client side for HTTP2 transports */
 extern const grpc_channel_filter grpc_http_client_filter;
 
+/* Channel arg to override the http2 :scheme header */
 #define GRPC_ARG_HTTP2_SCHEME "grpc.http2_scheme"
 
 #endif /* GRPC_CORE_LIB_CHANNEL_HTTP_CLIENT_FILTER_H */