introduce GoAwayError type

const.go

@@ -5,71 +5,6 @@ import (
 	"fmt"
 )
 
-type Error struct {
-	msg                string
-	timeout, temporary bool
-}
-
-func (ye *Error) Error() string {
-	return ye.msg
-}
-
-func (ye *Error) Timeout() bool {
-	return ye.timeout
-}
-
-func (ye *Error) Temporary() bool {
-	return ye.temporary
-}
-
-var (
-	// ErrInvalidVersion means we received a frame with an
-	// invalid version
-	ErrInvalidVersion = &Error{msg: "invalid protocol version"}
-
-	// ErrInvalidMsgType means we received a frame with an
-	// invalid message type
-	ErrInvalidMsgType = &Error{msg: "invalid msg type"}
-
-	// ErrSessionShutdown is used if there is a shutdown during
-	// an operation
-	ErrSessionShutdown = &Error{msg: "session shutdown"}
-
-	// ErrStreamsExhausted is returned if we have no more
-	// stream ids to issue
-	ErrStreamsExhausted = &Error{msg: "streams exhausted"}
-
-	// ErrDuplicateStream is used if a duplicate stream is
-	// opened inbound
-	ErrDuplicateStream = &Error{msg: "duplicate stream initiated"}
-
-	// ErrReceiveWindowExceeded indicates the window was exceeded
-	ErrRecvWindowExceeded = &Error{msg: "recv window exceeded"}
-
-	// ErrTimeout is used when we reach an IO deadline
-	ErrTimeout = &Error{msg: "i/o deadline reached", timeout: true, temporary: true}
-
-	// ErrStreamClosed is returned when using a closed stream
-	ErrStreamClosed = &Error{msg: "stream closed"}
-
-	// ErrUnexpectedFlag is set when we get an unexpected flag
-	ErrUnexpectedFlag = &Error{msg: "unexpected flag"}
-
-	// ErrRemoteGoAway is used when we get a go away from the other side
-	ErrRemoteGoAway = &Error{msg: "remote end is not accepting connections"}
-
-	// ErrStreamReset is sent if a stream is reset. This can happen
-	// if the backlog is exceeded, or if there was a remote GoAway.
-	ErrStreamReset = &Error{msg: "stream reset"}
-
-	// ErrConnectionWriteTimeout indicates that we hit the "safety valve"
-	// timeout writing to the underlying stream connection.
-	ErrConnectionWriteTimeout = &Error{msg: "connection write timeout", timeout: true}
-
-	// ErrKeepAliveTimeout is sent if a missed keepalive caused the stream close
-	ErrKeepAliveTimeout = &Error{msg: "keepalive timeout", timeout: true}
-)
-
 const (
 	// protoVersion is the only version we support
 	protoVersion uint8 = 0

errors.go

@@ -0,0 +1,102 @@
+package yamux
+
+import "fmt"
+
+type Error struct {
+	msg                string
+	timeout, temporary bool
+}
+
+func (ye *Error) Error() string {
+	return ye.msg
+}
+
+func (ye *Error) Timeout() bool {
+	return ye.timeout
+}
+
+func (ye *Error) Temporary() bool {
+	return ye.temporary
+}
+
+type GoAwayError struct {
+	Remote    bool
+	ErrorCode uint32
+}
+
+func (e *GoAwayError) Error() string {
+	if e.Remote {
+		return fmt.Sprintf("remote sent go away, code: %d", e.ErrorCode)
+	}
+	return fmt.Sprintf("sent go away, code: %d", e.ErrorCode)
+}
+
+func (e *GoAwayError) Timeout() bool {
+	return false
+}
+
+func (e *GoAwayError) Temporary() bool {
+	return false
+}
+
+func (e *GoAwayError) Is(target error) bool {
+	// to maintain compatibility with errors returned by previous versions
+	if e.Remote && target == ErrRemoteGoAway {
+		return true
+	} else if !e.Remote && target == ErrSessionShutdown {
+		return true
+	}
+
+	if err, ok := target.(*GoAwayError); ok {
+		return *e == *err
+	}
+	return false
+}
+
+var (
+	// ErrInvalidVersion means we received a frame with an
+	// invalid version
+	ErrInvalidVersion = &Error{msg: "invalid protocol version"}
+
+	// ErrInvalidMsgType means we received a frame with an
+	// invalid message type
+	ErrInvalidMsgType = &Error{msg: "invalid msg type"}
+
+	// ErrSessionShutdown is used if there is a shutdown during
+	// an operation
+	ErrSessionShutdown = &Error{msg: "session shutdown"}
+
+	// ErrStreamsExhausted is returned if we have no more
+	// stream ids to issue
+	ErrStreamsExhausted = &Error{msg: "streams exhausted"}
+
+	// ErrDuplicateStream is used if a duplicate stream is
+	// opened inbound
+	ErrDuplicateStream = &Error{msg: "duplicate stream initiated"}
+
+	// ErrReceiveWindowExceeded indicates the window was exceeded
+	ErrRecvWindowExceeded = &Error{msg: "recv window exceeded"}
+
+	// ErrTimeout is used when we reach an IO deadline
+	ErrTimeout = &Error{msg: "i/o deadline reached", timeout: true, temporary: true}
+
+	// ErrStreamClosed is returned when using a closed stream
+	ErrStreamClosed = &Error{msg: "stream closed"}
+
+	// ErrUnexpectedFlag is set when we get an unexpected flag
+	ErrUnexpectedFlag = &Error{msg: "unexpected flag"}
+
+	// ErrRemoteGoAway is used when we get a go away from the other side
+	ErrRemoteGoAway = &Error{msg: "remote end is not accepting connections"}
+
+	// ErrStreamReset is sent if a stream is reset. This can happen
+	// if the backlog is exceeded, or if there was a remote GoAway.
+	ErrStreamReset = &Error{msg: "stream reset"}
+
+	// ErrConnectionWriteTimeout indicates that we hit the "safety valve"
+	// timeout writing to the underlying stream connection.
+	ErrConnectionWriteTimeout = &Error{msg: "connection write timeout", timeout: true}
+
+	// ErrKeepAliveTimeout is sent if a missed keepalive caused the stream close
+	ErrKeepAliveTimeout = &Error{msg: "keepalive timeout", timeout: true}
+)