internal/http3: error codes

Define constants for RFC 9114 and RFC 9204 error codes.

For golang/go#70914

Change-Id: Icddaf0ef1468adc6ac8e7b8739d45c8e4400f0e4
Reviewed-on: https://go-review.googlesource.com/c/net/+/641837
Auto-Submit: Damien Neil <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>
Reviewed-by: Jonathan Amsterdam <[email protected]>

Author: neild

internal/http3/errors.go

@@ -0,0 +1,84 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.24
+
+package http3
+
+import "fmt"
+
+// http3Error is an HTTP/3 error code.
+type http3Error int
+
+const (
+	// https://www.rfc-editor.org/rfc/rfc9114.html#section-8.1
+	errH3NoError              = http3Error(0x0100)
+	errH3GeneralProtocolError = http3Error(0x0101)
+	errH3InternalError        = http3Error(0x0102)
+	errH3StreamCreationError  = http3Error(0x0103)
+	errH3ClosedCriticalStream = http3Error(0x0104)
+	errH3FrameUnexpected      = http3Error(0x0105)
+	errH3FrameError           = http3Error(0x0106)
+	errH3ExcessiveLoad        = http3Error(0x0107)
+	errH3IDError              = http3Error(0x0108)
+	errH3SettingsError        = http3Error(0x0109)
+	errH3MissingSettings      = http3Error(0x010a)
+	errH3RequestRejected      = http3Error(0x010b)
+	errH3RequestCancelled     = http3Error(0x010c)
+	errH3RequestIncomplete    = http3Error(0x010d)
+	errH3MessageError         = http3Error(0x010e)
+	errH3ConnectError         = http3Error(0x010f)
+	errH3VersionFallback      = http3Error(0x0110)
+
+	// https://www.rfc-editor.org/rfc/rfc9204.html#section-8.3
+	errQPACKDecompressionFailed = http3Error(0x0200)
+	errQPACKEncoderStreamError  = http3Error(0x0201)
+	errQPACKDecoderStreamError  = http3Error(0x0202)
+)
+
+func (e http3Error) Error() string {
+	switch e {
+	case errH3NoError:
+		return "H3_NO_ERROR"
+	case errH3GeneralProtocolError:
+		return "H3_GENERAL_PROTOCOL_ERROR"
+	case errH3InternalError:
+		return "H3_INTERNAL_ERROR"
+	case errH3StreamCreationError:
+		return "H3_STREAM_CREATION_ERROR"
+	case errH3ClosedCriticalStream:
+		return "H3_CLOSED_CRITICAL_STREAM"
+	case errH3FrameUnexpected:
+		return "H3_FRAME_UNEXPECTED"
+	case errH3FrameError:
+		return "H3_FRAME_ERROR"
+	case errH3ExcessiveLoad:
+		return "H3_EXCESSIVE_LOAD"
+	case errH3IDError:
+		return "H3_ID_ERROR"
+	case errH3SettingsError:
+		return "H3_SETTINGS_ERROR"
+	case errH3MissingSettings:
+		return "H3_MISSING_SETTINGS"
+	case errH3RequestRejected:
+		return "H3_REQUEST_REJECTED"
+	case errH3RequestCancelled:
+		return "H3_REQUEST_CANCELLED"
+	case errH3RequestIncomplete:
+		return "H3_REQUEST_INCOMPLETE"
+	case errH3MessageError:
+		return "H3_MESSAGE_ERROR"
+	case errH3ConnectError:
+		return "H3_CONNECT_ERROR"
+	case errH3VersionFallback:
+		return "H3_VERSION_FALLBACK"
+	case errQPACKDecompressionFailed:
+		return "QPACK_DECOMPRESSION_FAILED"
+	case errQPACKEncoderStreamError:
+		return "QPACK_ENCODER_STREAM_ERROR"
+	case errQPACKDecoderStreamError:
+		return "QPACK_DECODER_STREAM_ERROR"
+	}
+	return fmt.Sprintf("H3_ERROR_%v", int(e))
+}