Re: why does netfilter make upload very slow? (was: Re: e1000 ->82540EM on linux 2.6.0-test[45] very slow in one direction)

From: Florian Zwoch
Date: Wed Oct 15 2003 - 03:30:50 EST


Harald Welte wrote:
Would somebody like to explain why netfilter (in kernel, but not in use)
makes upload go very slow? I am by no means a network guru, but eager to
learn :-)


let's get this straight. There are five possible cases

a) CONFIG_NETFILTER disabled. you won't even have the netfilter hooks
in the network stack (so certainly no netfilter-using modules loaded)

no problem

b) CONFIG_NETFILTER enabled, but _no_ modules (iptable_filter,
ip_conntrack, ...) attached to the netfilter hook

no problem

c) CONFIG_NETFILTER enabled and iptable_filter.o (which pulls ip_tables.o)
loaded, NO RULES in the table

no problem

d) CONFIG_NETFILTER enabled and iptable_filter.o (which pulls ip_tables.o)
loaded, RULES in the table

no problem (as long as i dont load any rules that require ip_conntrack)

e) CONFIG_NETFILTER enabled and ip_conntrack.o loaded, iptable_filter
loaded or not, rules or not

*boink*

whenever i try to load ip_conntrack the nic performance drops from 5mb/s to 200k/s.

still using 2.6.0-test6.

regards,
Florian


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