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    SubjectRe: NET_NS: unregister_netdevice: waiting for lo to become free (after using openvpn)
    On Thu, 05 Aug 2010 02:51:29 -0700
    ebiederm@xmission.com (Eric W. Biederman) wrote:

    > Michael Leun <lkml20100708@newton.leun.net> writes:
    >
    > > Hi,
    > >
    > > On Wed, 04 Aug 2010 17:12:29 -0700
    > > ebiederm@xmission.com (Eric W. Biederman) wrote:
    > >
    > > First, thank you very much for picking that up (and, of course, for
    > > your work at linux in general).
    > >
    > >
    > >> > # > unshare -n /bin/bash
    > >> > # > # how to setup veth device pair to get connectivity into
    > >> > namespace not shown here # > openvpn --config some.config
    > >> > [ running some traffic over vpn device not shown here ]
    > >> > ^c # stopping openvpn
    > >> > # > lsof -i
    > >> > # > netstat -an
    > >> > Active Internet connections (servers and established)
    > >> > Proto Recv-Q Send-Q Local Address Foreign Address
    > >> > State Active UNIX domain sockets (servers and established)
    > >> > Proto RefCnt Flags Type State I-Node Path
    > >> > # > ps ax|grep openvpn|grep -v grep
    > >> > # > # cannot find anything that suggests there is anything left
    > >> > from that openvpn session # > exit # logging out from shell in
    > >> > network namespace
    > >> >
    > >> > Now I get
    > >> >
    > >> > Jul 10 20:02:36 doris kernel: unregister_netdevice: waiting for
    > >> > lo to become free. Usage count = 3 [repeated]
    > >>
    > >> How many times?
    > >
    > > Unfortunately looks like indefinitely. Never watched longer so far
    > > (rebooted soon), but I'm seeing this message now repeated every 10
    > > secs for ~10 minutes on a idle system.
    >
    > Ugh. A real bug then. These can be a pain to track down and fix. I
    > think the last one of these I tracked down took a couple of weeks. I
    > will start digging in when I get back from vacation.

    As I said, if I can do anything to support you, testing or so, please
    let me know.

    Until then: Have a great vacation!

    > > Additionally when testing this I found another one (by accident
    > > started my firewall script in that namespace...) - using netfilter
    > > RECENT makes it barf. Stripped down to the essentials it looks like
    > > this:
    >
    > Micheal this is on 2.6.35?

    Yup - almost vanilla 2.6.35, only patches for aufs (union filesystem)
    got in.

    > Alexey can you look at this BUG_ON? It looks like there has been a
    > regression or you missed something when you did the netns conversion
    > of xt_recent.
    >
    >
    > >> # unshare -n /bin/bash
    > >> # iptables -I INPUT -d 1.2.3.4 -m recent --name BLA --set
    > >> # exit
    > >
    > > Aug 5 11:19:47 doris kernel: [ 218.420238] ------------[ cut
    > > here ]------------ Aug 5 11:19:47 doris kernel: [ 218.420256]
    > > kernel BUG at net/netfilter/xt_recent.c:609! Aug 5 11:19:47 doris
    [...]

    --
    MfG,

    Michael Leun



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