Revert "Send response to multicast address if requested"

This reverts commit c6d75aa8ab.

Conflicts:
	server.go

server.go

@@ -267,6 +267,8 @@ func (s *Server) handleQuestion(q dns.Question) (multicastRecs, unicastRecs []dn
 
 // sendResponse is used to send a response packet
 func (s *Server) sendResponse(resp *dns.Msg, from net.Addr, unicast bool) error {
+	// TODO(reddaly): Respect the unicast argument, and allow sending responses
+	// over multicast.
 	buf, err := resp.Pack()
 	if err != nil {
 		return err
@@ -274,27 +276,11 @@ func (s *Server) sendResponse(resp *dns.Msg, from net.Addr, unicast bool) error
 
 	// Determine the socket to send from
 	addr := from.(*net.UDPAddr)
-	var conn *net.UDPConn
 	if addr.IP.To4() != nil {
-		conn = s.ipv4List
+		_, err = s.ipv4List.WriteToUDP(buf, addr)
-	} else {
-		conn = s.ipv6List
-	}
-
-	// Determine the address to send to if not unicast
-	if !unicast {
-		if addr.IP.To4() != nil {
-			addr = ipv4Addr
-		} else {
-			addr = ipv6Addr
-		}
-	}
-
-	// Guard against a missing connection or address
-	if conn == nil || addr == nil {
-		return fmt.Errorf("Unable to respond, missing connection (%v) or address (%v)",
-			conn, addr)
-	}
-	_, err = conn.WriteToUDP(buf, addr)
 		return err
+	} else {
+		_, err = s.ipv6List.WriteToUDP(buf, addr)
+		return err
+	}
 }