I guess I'll post my fix tool here too, since it is buried down in the
other discussion.

Here is a fix for windows servers, that doesn't require a firewall to work
http://www.wantedgov.it/page/62-srcds-query-cache/


On Sun, Sep 6, 2009 at 1:13 PM, Kaspars<[email protected]> wrote:
> 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.
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