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Message-Id: <201104112301.46776.hans@schillstrom.com>
Date: Mon, 11 Apr 2011 23:01:46 +0200
From: Hans Schillstrom <hans@...illstrom.com>
To: netdev@...r.kernel.org, Daniel Lezcano <daniel.lezcano@...e.fr>,
"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Race condition when creating multiple namespaces?
Hello
I'v been strugling with this for some time now
When creating multiple namespaces using lxc-start, un-initialized network namespace parts will be called by the new process in the namespace.
ex. when using conntrack or ipvsadm to quickly, (a sleep 2 "solves" the problem).
(From what I can see syscall clone() is used in lx-start i.e. do_fork will be called later on.)
Actually I was debugging ip_vs when closing multiple ns when I fell into this one.
I have a loop that create 33 containers whith lxc-start ... -- test.sh
the first thing the new conatiner does in test.sh is
#!/bin/bash
iptables -t mangle -A PREROUTING -m conntrack --ctstate RELATED,ESTABLISHED -j CONNMARK --restore-mark
nc -l -p1234
This results in NULL ptr in ip_conntrack_net_init(struct *net)
and in anoither test test.sh looks like this
#!/bin/bash
ipvsadm --start-daemon=master --mcast-interface=lo
nc -l -p1234
And this results in an uniitialized spinlock in ip_vs_sync
I put a printk in nsproxy: copy_namespaces() and could see a dozens of them
before anything appears from ipvs or conntrack.
My feeling is that when you start up user processes in a new name space,
all kernel related init should have been done (you should not need to add a sleep to get it working)
All test made by using todays net-next-2.6 (2.6.39-rc1)
Note:
That neither conntrack or ip_vs modules where loaded,
if modules where loaded before creating new namespaces it all works...
Finally the question,
Should it really work to load modules within a namespace ,
that is a part of netns ?
--
Mvh
Hasse Schillstrom
070-699 7150
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