gfe-relnote: Change QuicRstStream::ietf_error_code to 64 bits and move it out of the union with error_code.  Behavior change in IETF QUIC only, protected by gfe2_reloadable_flag_quic_enable_version_draft_25_v3 and gfe2_reloadable_flag_quic_enable_version_draft_27.

Multiple tests rely on ietf_error_code being set to the value of error_code.
However, if they stay in a union, and ietf_error_code is changed to 64 bits,
then the upper bits will be unitialized, because error_code has fewer bits.
Fortunately I was planning to move them out of the union so that upper layers
can still interact with QuicRstStreamErrorCode regardless of QUIC version.

PiperOrigin-RevId: 305870819
Change-Id: Iae47ede459094ade6f9dc7fddfc9acadb82fa417

quic/core/frames/quic_rst_stream_frame.cc

diff --git a/quic/core/frames/quic_rst_stream_frame.cc b/quic/core/frames/quic_rst_stream_frame.cc
index 63cf6ea..d9e14b7 100644
--- a/quic/core/frames/quic_rst_stream_frame.cc
+++ b/quic/core/frames/quic_rst_stream_frame.cc
@@ -20,15 +20,8 @@
     : control_frame_id(control_frame_id),
       stream_id(stream_id),
       error_code(error_code),
-      byte_offset(bytes_written) {}
-
-QuicRstStreamFrame::QuicRstStreamFrame(QuicControlFrameId control_frame_id,
-                                       QuicStreamId stream_id,
-                                       uint16_t ietf_error_code,
-                                       QuicStreamOffset bytes_written)
-    : control_frame_id(control_frame_id),
-      stream_id(stream_id),
-      ietf_error_code(ietf_error_code),
+      // TODO(b/124216424): Translate QuicRstStreamErrorCode to IETF error code.
+      ietf_error_code(error_code),
       byte_offset(bytes_written) {}
 
 std::ostream& operator<<(std::ostream& os,

quic/core/frames/quic_rst_stream_frame.h

diff --git a/quic/core/frames/quic_rst_stream_frame.h b/quic/core/frames/quic_rst_stream_frame.h
index 9a9ed56..6239123 100644
--- a/quic/core/frames/quic_rst_stream_frame.h
+++ b/quic/core/frames/quic_rst_stream_frame.h
@@ -18,10 +18,6 @@
                      QuicStreamId stream_id,
                      QuicRstStreamErrorCode error_code,
                      QuicStreamOffset bytes_written);
-  QuicRstStreamFrame(QuicControlFrameId control_frame_id,
-                     QuicStreamId stream_id,
-                     uint16_t ietf_error_code,
-                     QuicStreamOffset bytes_written);
 
   friend QUIC_EXPORT_PRIVATE std::ostream& operator<<(
       std::ostream& os,
@@ -33,15 +29,12 @@
 
   QuicStreamId stream_id;
 
-  // Caller must know whether IETF- or Google- QUIC is in use and
-  // set the appropriate error code.
-  union {
-    QuicRstStreamErrorCode error_code;
-    // In IETF QUIC the code is up to the app on top of quic, so is
-    // more general than QuicRstStreamErrorCode allows.
-    // TODO(fkastenholz): Upgrade to uint64_t
-    uint16_t ietf_error_code;
-  };
+  // Used for Google QUIC only.
+  // TODO(b/124216424): Consider using meaningful values when using IETF QUIC.
+  QuicRstStreamErrorCode error_code;
+
+  // Used for IETF QUIC only.
+  uint64_t ietf_error_code;
 
   // Used to update flow control windows. On termination of a stream, both
   // endpoints must inform the peer of the number of bytes they have sent on

quic/core/quic_framer.cc

diff --git a/quic/core/quic_framer.cc b/quic/core/quic_framer.cc
index dd880d7..da5d4c5 100644
--- a/quic/core/quic_framer.cc
+++ b/quic/core/quic_framer.cc
@@ -5765,18 +5765,14 @@
     return false;
   }
 
-  uint64_t error_code;
-  if (!reader->ReadVarInt62(&error_code)) {
+  if (!reader->ReadVarInt62(&frame->ietf_error_code)) {
     set_detailed_error("Unable to read rst stream error code.");
     return false;
   }
-  if (error_code > 0xffff) {
-    frame->ietf_error_code = 0xffff;
-    QUIC_DLOG(ERROR) << "Reset stream error code (" << error_code
-                     << ") > 0xffff";
-  } else {
-    frame->ietf_error_code = static_cast<uint16_t>(error_code);
-  }
+
+  // TODO(b/124216424): Translate IETF error code to QuicRstStreamErrorCode.
+  frame->error_code =
+      static_cast<QuicRstStreamErrorCode>(frame->ietf_error_code);
 
   if (!reader->ReadVarInt62(&frame->byte_offset)) {
     set_detailed_error("Unable to read rst stream sent byte offset.");