Could you use the firewall to rate limit using "-m limit --limit 1/s --limit-burst 10" or similar?
Maybe something like this? iptables -t nat -A PREROUTING -p udp -d SERVER_IP --dport SERVER_PORT -m string --algo kmp --string 'TSource Engine Query' -m length --length 53 -m limit --limit 1/s --limit-burst 10 -j REDIRECT --to-port 21015 Maybe won't even need the proxy if the firewall is limiting the DOS packets? I have not tried the above. } -----Original Message----- } From: [email protected] [mailto:hlds_linux- } [email protected]] On Behalf Of Kaspars } Sent: Sunday, September 06, 2009 9:43 AM } To: Half-Life dedicated Linux server mailing list } Subject: Re: [hlds_linux] A2S_INFO DDOS fix } } firewall rule could be adjusted to this: } iptables -t nat -A PREROUTING -p udp -d SERVER_IP --dport SERVER_PORT -m } string --algo kmp --string 'TSource Engine Query' -m length --length 53 -j } REDIRECT --to-port 21015 } } As for the rate limit... I don't think this is a good idea, because } setting } such a limit will make the server disappear from the browser list for } legit } clients. And if you have a good connection, you probably will not notice } the } traffic increase anyway. } } } 2009/9/6 Ronny Schedel <[email protected]> } } > } > I forgot an important part, your query proxy has still no rate limit. It } > can } > be used to flood spoofed IP's. } > } > } > > Hi, } > > } > > If you are on the hlds windows mailing list, then you probably already } > > know } > > about A2S_INFO DDOS attacks. I have mistakenly posted a *fix* on the } list } > > for *nix servers which I should have posted here. } > > } > > In short: } > > If your server gets ddosed with A2S_INFO packets, it will get really } > > laggy. } > > Setting sv_max_queries_sec to a low value will make the server } disappear } > > from the server browser list. I'm providing you with a UDP Caching } Proxy } > > which will query the server with A2S_INFO requests not more than once } in } > a } > > five seconds and respond to the client with the cached data. } > > } > > Setup: } > > 1. Get the source from http://www.gign.lv/tmp/querycache.c } > > 2. Compile with gcc querycache.c -o querycache } > > 3. Open an UDP port in firewall for the proxy server, lets say 21015 } > > 4. Make sure you have iptables NAT, REDIRECT and string match support } > > compiled into kernel or as modules } > > 5. execute: iptables -t nat -A PREROUTING -p udp -d } > > YOUR_EXTERNAL_TF2_SERVER_IP --dport YOUR_SERVER_PORT -m string --algo } kmp } > > --string 'TSource Engine Query' -j REDIRECT --to-port 21015 } > > 6. Run querycache (probably under screen, so you can detach from it) } > > } > > I've been ddosed with about 300req/sec and it works good, however I } don't } > > give any warranty that it will work for you. } > > _______________________________________________ } > > To unsubscribe, edit your list preferences, or view the list archives, } > > please visit: } > > http://list.valvesoftware.com/mailman/listinfo/hlds_linux } > > } > } > } > _______________________________________________ } > To unsubscribe, edit your list preferences, or view the list archives, } > please visit: } > http://list.valvesoftware.com/mailman/listinfo/hlds_linux } > } _______________________________________________ } To unsubscribe, edit your list preferences, or view the list archives, } please visit: } http://list.valvesoftware.com/mailman/listinfo/hlds_linux _______________________________________________ To unsubscribe, edit your list preferences, or view the list archives, please visit: http://list.valvesoftware.com/mailman/listinfo/hlds_linux
