expose crypto/tls errors on the TransportError (#4015)

internal/qerr/errors.go

@@ -17,15 +17,16 @@ type TransportError struct {
 	FrameType    uint64
 	ErrorCode    TransportErrorCode
 	ErrorMessage string
+	error        error // only set for local errors, sometimes
 }
 
 var _ error = &TransportError{}
 
 // NewLocalCryptoError create a new TransportError instance for a crypto error
-func NewLocalCryptoError(tlsAlert uint8, errorMessage string) *TransportError {
+func NewLocalCryptoError(tlsAlert uint8, err error) *TransportError {
 	return &TransportError{
-		ErrorCode:    0x100 + TransportErrorCode(tlsAlert),
-		ErrorMessage: errorMessage,
+		ErrorCode: 0x100 + TransportErrorCode(tlsAlert),
+		error:     err,
 	}
 }
 
@@ -35,6 +36,9 @@ func (e *TransportError) Error() string {
 		str += fmt.Sprintf(" (frame type: %#x)", e.FrameType)
 	}
 	msg := e.ErrorMessage
+	if len(msg) == 0 && e.error != nil {
+		msg = e.error.Error()
+	}
 	if len(msg) == 0 {
 		msg = e.ErrorCode.Message()
 	}
@@ -48,6 +52,10 @@ func (e *TransportError) Is(target error) bool {
 	return target == net.ErrClosed
 }
 
+func (e *TransportError) Unwrap() error {
+	return e.error
+}
+
 // An ApplicationErrorCode is an application-defined error code.
 type ApplicationErrorCode uint64
 

internal/qerr/errors_test.go

@@ -2,6 +2,7 @@ package qerr
 
 import (
 	"errors"
+	"fmt"
 	"net"
 
 	"github.com/quic-go/quic-go/internal/protocol"
@@ -10,6 +11,12 @@ import (
 	. "github.com/onsi/gomega"
 )
 
+type myError int
+
+var _ error = myError(0)
+
+func (e myError) Error() string { return fmt.Sprintf("my error %d", e) }
+
 var _ = Describe("QUIC Errors", func() {
 	Context("Transport Errors", func() {
 		It("has a string representation", func() {
@@ -41,12 +48,20 @@ var _ = Describe("QUIC Errors", func() {
 
 		Context("crypto errors", func() {
 			It("has a string representation for errors with a message", func() {
-				err := NewLocalCryptoError(0x42, "foobar")
-				Expect(err.Error()).To(Equal("CRYPTO_ERROR 0x142 (local): foobar"))
+				myErr := myError(1337)
+				err := NewLocalCryptoError(0x42, myErr)
+				Expect(err.Error()).To(Equal("CRYPTO_ERROR 0x142 (local): my error 1337"))
+			})
+
+			It("unwraps errors", func() {
+				var myErr myError
+				err := NewLocalCryptoError(0x42, myError(1337))
+				Expect(errors.As(err, &myErr)).To(BeTrue())
+				Expect(myErr).To(BeEquivalentTo(1337))
 			})
 
 			It("has a string representation for errors without a message", func() {
-				err := NewLocalCryptoError(0x2a, "")
+				err := NewLocalCryptoError(0x2a, nil)
 				Expect(err.Error()).To(Equal("CRYPTO_ERROR 0x12a (local): tls: bad certificate"))
 			})
 		})