[transport] Make transport types derive from Transport (#36454)

This is a first step to making transports speak various forms of CallDestination, and also solidifying the future world where things talk in terms of `ClientTransport` or `ServerTransport` throughout the rest of the stack.

Closes #36454

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/36454 from ctiller:transport-refs 4d25347023
PiperOrigin-RevId: 628432909

src/core/ext/transport/binder/transport/binder_transport.h

@@ -41,8 +41,7 @@ struct grpc_binder_stream;
 // depends on what style we want to follow)
 // TODO(mingcl): Decide casing for this class name. Should we use C-style class
 // name here or just go with C++ style?
-struct grpc_binder_transport final : public grpc_core::Transport,
-                                     public grpc_core::FilterStackTransport {
+struct grpc_binder_transport final : public grpc_core::FilterStackTransport {
   explicit grpc_binder_transport(
       std::unique_ptr<grpc_binder::Binder> binder, bool is_client,
       std::shared_ptr<grpc::experimental::binder::SecurityPolicy>

src/core/ext/transport/chaotic_good/client_transport.h

@@ -65,8 +65,7 @@
 namespace grpc_core {
 namespace chaotic_good {
 
-class ChaoticGoodClientTransport final : public Transport,
-                                         public ClientTransport {
+class ChaoticGoodClientTransport final : public ClientTransport {
  public:
   ChaoticGoodClientTransport(
       PromiseEndpoint control_endpoint, PromiseEndpoint data_endpoint,

src/core/ext/transport/chaotic_good/server_transport.h

@@ -78,8 +78,7 @@
 namespace grpc_core {
 namespace chaotic_good {
 
-class ChaoticGoodServerTransport final : public Transport,
-                                         public ServerTransport {
+class ChaoticGoodServerTransport final : public ServerTransport {
  public:
   ChaoticGoodServerTransport(
       const ChannelArgs& args, PromiseEndpoint control_endpoint,

src/core/ext/transport/chttp2/transport/internal.h

@@ -224,8 +224,7 @@ typedef enum {
 } grpc_chttp2_keepalive_state;
 
 struct grpc_chttp2_transport final
-    : public grpc_core::Transport,
-      public grpc_core::FilterStackTransport,
+    : public grpc_core::FilterStackTransport,
       public grpc_core::RefCounted<grpc_chttp2_transport,
                                    grpc_core::NonPolymorphicRefCount>,
       public grpc_core::KeepsGrpcInitialized {

src/core/ext/transport/cronet/transport/cronet_transport.cc

@@ -119,8 +119,7 @@ static bidirectional_stream_callback cronet_callbacks = {
     on_canceled};
 
 // Cronet transport object
-struct grpc_cronet_transport final : public grpc_core::Transport,
-                                     public grpc_core::FilterStackTransport {
+struct grpc_cronet_transport final : public grpc_core::FilterStackTransport {
   FilterStackTransport* filter_stack_transport() override { return this; }
   grpc_core::ClientTransport* client_transport() override { return nullptr; }
   grpc_core::ServerTransport* server_transport() override { return nullptr; }

src/core/ext/transport/inproc/inproc_transport.cc

@@ -34,7 +34,6 @@ namespace grpc_core {
 
 namespace {
 class InprocServerTransport final : public RefCounted<InprocServerTransport>,
-                                    public Transport,
                                     public ServerTransport {
  public:
   void SetAcceptor(Acceptor* acceptor) override {
@@ -108,7 +107,7 @@ class InprocServerTransport final : public RefCounted<InprocServerTransport>,
       "inproc_server_transport", GRPC_CHANNEL_CONNECTING};
 };
 
-class InprocClientTransport final : public Transport, public ClientTransport {
+class InprocClientTransport final : public ClientTransport {
  public:
   void StartCall(CallHandler call_handler) override {
     call_handler.SpawnGuarded(

src/core/ext/transport/inproc/legacy_inproc_transport.cc

@@ -101,8 +101,7 @@ struct shared_mu {
   gpr_refcount refs;
 };
 
-struct inproc_transport final : public grpc_core::Transport,
-                                public grpc_core::FilterStackTransport {
+struct inproc_transport final : public grpc_core::FilterStackTransport {
   inproc_transport(shared_mu* mu, bool is_client)
       : mu(mu),
         is_client(is_client),

src/core/lib/transport/transport.h

@@ -498,7 +498,40 @@ std::string grpc_transport_op_string(grpc_transport_op* op);
 
 namespace grpc_core {
 
-class FilterStackTransport {
+class FilterStackTransport;
+class ClientTransport;
+class ServerTransport;
+
+class Transport : public Orphanable {
+ public:
+  struct RawPointerChannelArgTag {};
+  static absl::string_view ChannelArgName() { return GRPC_ARG_TRANSPORT; }
+
+  virtual FilterStackTransport* filter_stack_transport() = 0;
+  virtual ClientTransport* client_transport() = 0;
+  virtual ServerTransport* server_transport() = 0;
+
+  // name of this transport implementation
+  virtual absl::string_view GetTransportName() const = 0;
+
+  // implementation of grpc_transport_set_pollset
+  virtual void SetPollset(grpc_stream* stream, grpc_pollset* pollset) = 0;
+
+  // implementation of grpc_transport_set_pollset
+  virtual void SetPollsetSet(grpc_stream* stream,
+                             grpc_pollset_set* pollset_set) = 0;
+
+  void SetPollingEntity(grpc_stream* stream,
+                        grpc_polling_entity* pollset_or_pollset_set);
+
+  // implementation of grpc_transport_perform_op
+  virtual void PerformOp(grpc_transport_op* op) = 0;
+
+  // implementation of grpc_transport_get_endpoint
+  virtual grpc_endpoint* GetEndpoint() = 0;
+};
+
+class FilterStackTransport : public Transport {
  public:
   // Memory required for a single stream element - this is allocated by upper
   // layers and initialized by the transport
@@ -536,18 +569,18 @@ class FilterStackTransport {
                              grpc_closure* then_schedule_closure) = 0;
 
  protected:
-  ~FilterStackTransport() = default;
+  ~FilterStackTransport() override = default;
 };
 
-class ClientTransport {
+class ClientTransport : public Transport {
  public:
   virtual void StartCall(CallHandler call_handler) = 0;
 
  protected:
-  ~ClientTransport() = default;
+  ~ClientTransport() override = default;
 };
 
-class ServerTransport {
+class ServerTransport : public Transport {
  public:
   // Acceptor helps transports create calls.
   class Acceptor {
@@ -569,36 +602,7 @@ class ServerTransport {
   virtual void SetAcceptor(Acceptor* acceptor) = 0;
 
  protected:
-  ~ServerTransport() = default;
-};
-
-class Transport : public Orphanable {
- public:
-  struct RawPointerChannelArgTag {};
-  static absl::string_view ChannelArgName() { return GRPC_ARG_TRANSPORT; }
-
-  virtual FilterStackTransport* filter_stack_transport() = 0;
-  virtual ClientTransport* client_transport() = 0;
-  virtual ServerTransport* server_transport() = 0;
-
-  // name of this transport implementation
-  virtual absl::string_view GetTransportName() const = 0;
-
-  // implementation of grpc_transport_set_pollset
-  virtual void SetPollset(grpc_stream* stream, grpc_pollset* pollset) = 0;
-
-  // implementation of grpc_transport_set_pollset
-  virtual void SetPollsetSet(grpc_stream* stream,
-                             grpc_pollset_set* pollset_set) = 0;
-
-  void SetPollingEntity(grpc_stream* stream,
-                        grpc_polling_entity* pollset_or_pollset_set);
-
-  // implementation of grpc_transport_perform_op
-  virtual void PerformOp(grpc_transport_op* op) = 0;
-
-  // implementation of grpc_transport_get_endpoint
-  virtual grpc_endpoint* GetEndpoint() = 0;
+  ~ServerTransport() override = default;
 };
 
 }  // namespace grpc_core