Handle endpoint disconnection better

src/core/transport/chttp2/parsing.c

@@ -667,6 +667,11 @@ static int init_rst_stream_parser(
                                        &transport_parsing->simple.rst_stream,
                                        transport_parsing->incoming_frame_size,
                                        transport_parsing->incoming_frame_flags);
+  transport_parsing->incoming_stream = grpc_chttp2_parsing_lookup_stream(transport_parsing,
+                                  transport_parsing->incoming_stream_id);
+  if (!transport_parsing->incoming_stream) {
+    return init_skip_frame_parser(transport_parsing, 0);
+  }
   transport_parsing->parser = grpc_chttp2_rst_stream_parser_parse;
   transport_parsing->parser_data = &transport_parsing->simple.rst_stream;
   return ok;

src/core/transport/chttp2/writing.c

@@ -144,6 +144,11 @@ void grpc_chttp2_perform_writes(
 
   GPR_ASSERT(transport_writing->outbuf.count > 0);
 
+  if (!endpoint) {
+    grpc_chttp2_terminate_writing(transport_writing, 0);
+    return;
+  }
+
   switch (grpc_endpoint_write(endpoint, transport_writing->outbuf.slices,
                               transport_writing->outbuf.count, finish_write_cb,
                               transport_writing)) {

src/core/transport/chttp2_transport.c

@@ -522,7 +522,7 @@ void grpc_chttp2_terminate_writing(
   /* leave the writing flag up on shutdown to prevent further writes in unlock()
      from starting */
   t->writing_active = 0;
-  if (!t->endpoint_reading) {
+  if (t->ep && !t->endpoint_reading) {
     grpc_endpoint_destroy(t->ep);
     t->ep = NULL;
     UNREF_TRANSPORT(t, "disconnect"); /* safe because we'll still have the ref for write */