[tor-relays] TCP: drop open request

Hi! Since yesterday, the kern.log of the relay I'm running is flooded with "TCP: drop open request from". I first thought it was a kind of DDOS on our servers but it seems to be related to Tor (When I stop Tor, kernel doesn't complain anymore). Does somebody have an idea of why this is happening and what to do to mitigate it? Thanks a lot.