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SubjectRe: tcp_keepalive crash - more data, speculations - masq tie?
Date
Good morning. System still standing. So it now seems most likely (> 90%) 
that what the tcp_timer code does "if (elapsed >=
sysctl_tcp_keepalive_time)" occassions the crash. It would be a small
convenience if setting tcp_keepalive_time to 0, rather than to an absurdly
high value, also caused that code to be skipped (zero - it's not just for
booleans anymore).

I've also run across a reference to Linux masquerading not working
compatibly with keepalives:

http://x28.deja.com/[ST_rn=ps]/getdoc.xp?AN=587356272&CONTEXT=951840031.1168572471&hitnum=14

Not sure how that could fit here, but the box in question is
masquerading. It might explain why you're not seeing more reports on this,
if the problem only surfaces when the firewall/masq box is also an Apache
&c. server. The other less-common aspect of this setup, as I've mentioned,
is its DSL-bridged connection.

There's also a report you may be aware of from 1/1/2000 on comp.os.linux
about keepalive itself not functioning correctly on 2.2 kernels (and I've
seen a few others reports elsewhere to the same effect but didn't save the
references) . Could this help triangulate the problem?:

http://x28.deja.com/[ST_rn=ps]/getdoc.xp?AN=567044038&CONTEXT=951840031.1168572471&hitnum=77

I also continue to see no hanging tcp sockets for keepalive to be
concerned with killing, so if it thought it was seeing something > 2 hours
old to deal with before in that spot of code, it may well have been in
error to think it saw that - and the majority of the crashes have
happenned with no masqueraded systems connected, when Apache, sendmail and
DNS amounted to the whole of the outside traffic - all of which are
handling their sockets fine on their own.

Whit

On Mon, 28 Feb 2000, Whit Blauvelt wrote:
> I set /proc/sys/net/ipv4/tcp_keepalive_time to
> 30 days (2592000) rather than 2 hours yesterday morning, and so far no
> crash.
>
> If this does turn out to stop the crashes, then having changed this value
> means that the condition in tcp_timer.c of
>
> if (elapsed >= sysctl_tcp_keepalive_time)
>
> will never be met in the real world, with the implication that it's
> something that happens when it is that triggers the seizure.

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