Handle RST_STREAM messages when writing H2 responses

lib/bandit/http2/errors.ex

@@ -36,11 +36,17 @@ defmodule Bandit.HTTP2.Errors do
     http_1_1_requires: 0xD
   }
 
+  @spec to_reason(integer()) :: atom()
+
   for {name, value} <- error_codes do
     @spec unquote(name)() :: unquote(Macro.var(name, Elixir)) :: unquote(value)
     def unquote(name)(), do: unquote(value)
+
+    def to_reason(unquote(value)), do: unquote(name)
   end
 
+  def to_reason(_), do: :unknown
+
   # Represents a stream error as defined in RFC9113§5.4.2
   defmodule StreamError do
     defexception [:message, :error_code]

lib/bandit/http2/stream.ex

@@ -380,8 +380,18 @@ defmodule Bandit.HTTP2.Stream do
     end
 
     @spec do_recv_rst_stream!(term(), term()) :: no_return()
-    defp do_recv_rst_stream!(_stream, error_code),
-      do: raise("Client sent RST_STREAM with error code #{error_code}")
+    defp do_recv_rst_stream!(_stream, error_code) do
+      case Bandit.HTTP2.Errors.to_reason(error_code) do
+        reason when reason in [:no_error, :cancel] ->
+          raise(Bandit.TransportError, message: "Client reset stream normally", error: :closed)
+
+        reason ->
+          raise(Bandit.TransportError,
+            message: "Received RST_STREAM from client: #{reason} (#{error_code})",
+            error: reason
+          )
+      end
+    end
 
     @spec do_stream_closed_error!(term()) :: no_return()
     defp do_stream_closed_error!(msg), do: stream_error!(msg, Bandit.HTTP2.Errors.stream_closed())
@@ -418,6 +428,7 @@ defmodule Bandit.HTTP2.Stream do
       stream =
         receive do
           {:send_window_update, delta} -> do_recv_send_window_update(stream, delta)
+          {:rst_stream, error_code} -> do_recv_rst_stream!(stream, error_code)
         after
           0 -> stream
         end

test/bandit/http2/protocol_test.exs

@@ -1997,7 +1997,7 @@ defmodule HTTP2ProtocolTest do
       assert output =~ "(Bandit.HTTP2.Errors.ConnectionError) Received RST_STREAM in idle state"
     end
 
-    test "raises an error on upon receipt of an RST_STREAM frame", context do
+    test "raises an error upon receipt of an RST_STREAM frame during reading", context do
       socket = SimpleH2Client.setup_connection(context)
 
       errors =
@@ -2007,12 +2007,65 @@ defmodule HTTP2ProtocolTest do
           Process.sleep(100)
         end)
 
-      assert errors =~ "Client sent RST_STREAM with error code 99"
+      assert errors =~ "(Bandit.TransportError) Received RST_STREAM from client: unknown (99)"
     end
 
     def expect_reset(conn) do
       read_body(conn)
     end
+
+    test "raises an error upon receipt of an RST_STREAM frame during writing", context do
+      socket = SimpleH2Client.setup_connection(context)
+
+      errors =
+        capture_log(fn ->
+          SimpleH2Client.send_simple_headers(socket, 1, :get, "/write_after_delay", context.port)
+          SimpleH2Client.send_rst_stream(socket, 1, 99)
+          Process.sleep(200)
+        end)
+
+      assert errors =~ "(Bandit.TransportError) Received RST_STREAM from client: unknown (99)"
+    end
+
+    def write_after_delay(conn) do
+      Process.sleep(100)
+      send_resp(conn, 200, "OK")
+    end
+
+    test "considers :no_error RST_STREAM frame as a normal closure during chunk writing",
+         context do
+      socket = SimpleH2Client.setup_connection(context)
+
+      errors =
+        capture_log(fn ->
+          SimpleH2Client.send_simple_headers(socket, 1, :get, "/expect_chunk_error", context.port)
+          SimpleH2Client.send_rst_stream(socket, 1, 0)
+          Process.sleep(200)
+        end)
+
+      assert errors == ""
+    end
+
+    test "considers :cancel RST_STREAM frame as a normal closure during chunk writing",
+         context do
+      socket = SimpleH2Client.setup_connection(context)
+
+      errors =
+        capture_log(fn ->
+          SimpleH2Client.send_simple_headers(socket, 1, :get, "/expect_chunk_error", context.port)
+          SimpleH2Client.send_rst_stream(socket, 1, 8)
+          Process.sleep(200)
+        end)
+
+      assert errors == ""
+    end
+
+    def expect_chunk_error(conn) do
+      conn = send_chunked(conn, 200)
+      Process.sleep(100)
+      {:error, :closed} = chunk(conn, "CHUNK")
+      conn
+    end
   end
 
   describe "SETTINGS frames" do