Wrap handshake errors in a temporary net.Error().

Fixes bug #14135.

socks.go

@@ -48,6 +48,21 @@ const (
 // Put a sanity timeout on how long we wait for a SOCKS request.
 const socksRequestTimeout = 5 * time.Second
 
+// socksError wraps connection errors in a temporary net.Error interface.
+type socksError string
+
+func (e socksError) Error() string {
+	return string(e)
+}
+
+func (e socksError) Timeout() bool {
+	return false
+}
+
+func (e socksError) Temporary() bool {
+	return true
+}
+
 // SocksRequest describes a SOCKS request.
 type SocksRequest struct {
 	// The endpoint requested by the client as a "host:port" string.
@@ -166,27 +181,35 @@ func (ln *SocksListener) Accept() (net.Conn, error) {
 // 		}
 // 		go handleConn(conn)
 // 	}
-func (ln *SocksListener) AcceptSocks() (*SocksConn, error) {
-	c, err := ln.Listener.Accept()
-	if err != nil {
+func (ln *SocksListener) AcceptSocks() (conn *SocksConn, err error) {
+	conn = new(SocksConn)
+	if conn.Conn, err = ln.Listener.Accept(); err != nil {
 		return nil, err
 	}
-	conn := new(SocksConn)
-	conn.Conn = c
-	err = conn.SetDeadline(time.Now().Add(socksRequestTimeout))
-	if err != nil {
-		return nil, err
+
+	// All errors occur past this point net.Error or not, have absolutely
+	// nothing to do with the SocksListener or the Accept() call, and
+	// instead are errors generated by the handshake process.  Thus, all
+	// errors that occur are wrapped in a net.Error implementation whos
+	// Temporary() always returns true.
+	defer func() {
+		if err != nil {
+			if conn != nil {
+				conn.Close()
+				conn = nil
+			}
+			err = socksError(err.Error())
+		}
+	}()
+
+	if err = conn.SetDeadline(time.Now().Add(socksRequestTimeout)); err != nil {
+		return
 	}
-	conn.Req, err = socks5Handshake(conn)
-	if err != nil {
-		conn.Close()
-		return nil, err
+	if conn.Req, err = socks5Handshake(conn); err != nil {
+		return
 	}
 	err = conn.SetDeadline(time.Time{})
-	if err != nil {
-		return nil, err
-	}
-	return conn, nil
+	return
 }
 
 // Returns "socks5", suitable to be included in a call to Cmethod.
@@ -501,4 +524,5 @@ func socksReadByteVerify(rw *bufio.ReadWriter, descr string, expected byte) erro
 	return nil
 }
 
+var _ net.Error = (socksError)("")
 var _ net.Listener = (*SocksListener)(nil)