Casual technical question about /etc/services

Tarek W. mailinglists1 at
Tue Mar 30 06:15:09 PST 2004

On Tue, 2004-03-30 at 06:14, Dagmar d'Surreal wrote: [snipped]
> On Mon, 2004-03-29 at 19:45, Tarek W. wrote:
> > 2) ip_conntrack is either loaded by explicitely using "-m state" in an
> > iptables rule or by manually loading it
> I generally trust that kmod will do the necessary things.  I still don't
> see why so many people's scripts forcibly load those modules, aside from
> just being too lazy to specify only the ones that have to be loaded
> manually (like the IRC and FTP masqing modules).  *sigh*

to expand on what u said, all ip_conntrack helper modules have to loaded
"manually", they aren't loaded automagically.

I think that's why sometimes u see ip_conntrack or other modules loaded
manually also, because not many people know that *only* ip_conntrack
helper modules have to be loaded manually.

> Actually, I was trying to make sure that invoking the state matching
> module explicitly for outgoing UDP traffic on particular ports wasn't
> going to increase the overhead incurred by netfilter.  It looks like
> that's not the case, but I'm sure we'll hear about it eventually if it
> is the case.  Normally, even for clients I wouldn't care unless the

actually, I can guarantee that specifying the state match (utilizing
ipt_state.o) does not incur any overhead in the ip_conntrack.o area
(loading or operation) after the former loaded. however, it is an extra
rule and some overhead will be incurred when traffic is inspected by
that rule as I'm sure u already know.

> machine weren't carrying traffic at full speed, but I don't want people
> going around making mealy-mouthed comments about how we "senselessly
> waste clockcycles" or somesuch.

I'd like to reiterate that traffic begins to deteriorate only at speeds
above 30ish mbits and for a packet size of around 512 bytes. so I
shouldn't expect any negative comments in that area from anybody.
anyway, firewall design refinement doesn't have to come this early,
security is primordial if I'm not mistaken.

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