Relay (#678)

Co-authored-by: Wade Simmons <wsimmons@slack-corp.com>

udp/udp_generic.go

@@ -86,6 +86,6 @@ func (u *Conn) ListenOut(r EncReader, lhf LightHouseHandlerFunc, cache *firewall
 
 		udpAddr.IP = rua.IP
 		udpAddr.Port = uint16(rua.Port)
-		r(udpAddr, plaintext[:0], buffer[:n], h, fwPacket, lhf, nb, q, cache.Get(u.l))
+		r(udpAddr, nil, plaintext[:0], buffer[:n], h, fwPacket, lhf, nb, q, cache.Get(u.l))
 	}
 }