cdcc RTTs in FreeBSD Jails

Vernon Schryver
Tue Jun 1 22:16:44 UTC 2004

> From: Andy Hilker 

> Outside DCC, where the change happened. But now i think it is not
> a jail problem, because now i have some similar behaviour on other
> real servers.
> I tried a fresh install on another (real) host, maximum of 4 servers
> are working. Requests for only 4 servers are sent out.

That sounds as if a too-smart-by-half firewall is interfering somewhere
between where you run tcpdump and where you run `cdcc rtt`

> And again, by placing an arbitrary server on top (or the first ...
> entries) in map.txt, doing 
>  # rm map; cdcc "load map.txt" 
> i could get nearly every server working.  But manually adding 12
> working servers only 1, 4, 9 or 10 servers are declared as working.
> There seems to be a max # of servers per host.
> Very very strange, i know this :)

The previous `cdcc` output you sent shows that cdcc sent packets
to 12 DCC servers but heard from only 1.
Something is eating packets sent by cdcc.

> I see DNS requests and response for all dcc1-5 servers. But 6277
> requests only for the # of working servers.
> Is there a possibility to debug, to which servers cdcc tries to
> send out requests? 

I usually use breakpoints in the code.

>                     And if no query, why not?

Because some device is eating packets sent by cdcc.

> I do not understand why hosts at the same switch, with nearly the
> same configuration all have different maximum # of servers.

Is whatever you mean by "same switch" some kind of firewall?

Are you running some kind of "ipchains" or "ipfw" firewall rules?

Vernon Schryver

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