[tor-relays] TCP: drop open request

[grarpamp]

On Fri, Oct 25, 2013 at 12:10 AM, Roger Dingledine <arma at mit.edu> wrote:
> On Fri, Oct 25, 2013 at 12:43:42PM +0900, mett wrote:
>> 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).
>
> if you're in BSD-land.

It's a Linux message. Feed it to a search engine and you'll find
several things to try depending on what the cause is. It shuts
off either because Tor is attracting the syn's or the overall count
is lower with Tor off, you'll have to tcpdump to see. Look into
syn cookies, packet filter rules, and stack tuning.