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SubjectRe: Extremely slow network with e1000 & ip_conntrack
On Fri, Dec 05, 2003 at 12:28:19PM -0800, David S. Miller wrote:

> The culprit is net/ipv4/netfilter/ip_conntrack_standalone.c,
> in ip_refrag(), it does this:

Sorry for getting back to you so late, but as indicated before, I was
offline while travelling during the last week.

Thanks for spotting and fixing the bug.

> Some auditing is definitely necessary wrt. TSO and netfilter. In particular
> I am incredibly confident that we have issues in cases like when the FTP
> netfilter modules mangle the data. Another area for inspection are the
> cases where TCP header bits are changed and thus the checksum needs to
> be adjusted.

yes, this is certainly a problem - but not with conntrack, only with
nat. So maybe we should add a safeguard, preventing
iptables_nat/ipchains/ipfwadm from being loaded when TSO on any
interface is enabled? Or at least print a warining in syslog?

- Harald Welte <>
"Fragmentation is like classful addressing -- an interesting early
architectural error that shows how much experimentation was going
on while IP was being designed." -- Paul Vixie
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