Re: [Xen-devel] More on networking hang

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

Looks as though perhaps the connection-tracking table is full. :-)

If you are churning through a lot of TCP connections then the
conntrack table may be full of defunct TCBs in TIME WAIT (2MSL)
state. 

Not sure what the best solution is: when we were doing evaluation
tests for our paper we disabled connection tracking (which means that
things like NAT are unavailable). I haven't looked around, but there
may well be a way to tell Linux to reuse TCBs in TIME WAIT state.

This would exaplain networking drop-outs. No more connections can be
made until some old TCBs are garbage collected, after a 120s timeout.

 -- Keir

> ip_conntrack: table full, dropping packet.
> ip_conntrack: table full, dropping packet.
> ip_conntrack: table full, dropping packet.
> ip_conntrack: table full, dropping packet.
> ip_conntrack: table full, dropping packet.
> ip_conntrack: table full, dropping packet.
> ip_conntrack: table full, dropping packet.
> ip_conntrack: table full, dropping packet.
> ip_conntrack: table full, dropping packet.
> ip_conntrack: table full, dropping packet.
> NET: 481 messages suppressed.
> ip_conntrack: table full, dropping packet.
> NET: 532 messages suppressed.
> ip_conntrack: table full, dropping packet.
> NET: 547 messages suppressed.
> ip_conntrack: table full, dropping packet.
> NET: 393 messages suppressed.
> ip_conntrack: table full, dropping packet.
> NET: 25 messages suppressed.
> ip_conntrack: table full, dropping packet.
> NET: 23 messages suppressed.
> ip_conntrack: table full, dropping packet.
> NET: 33 messages suppressed.
> ip_conntrack: table full, dropping packet.


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