[ovs-dev] OVS2.6+dpdk IPv6 Conntrack support

[Sridhar Gaddam]

Thanks. We will avoid sending the ND packets to conntrack. In the long run,
its good to fix this inconsistency as Jarno suggested.

On Sat, Dec 17, 2016 at 2:55 AM, Jarno Rajahalme <jarno at ovn.org> wrote:

>
> > On Dec 16, 2016, at 9:12 AM, Sridhar Gaddam <sgaddam at redhat.com> wrote:
> >
> > ​​
> >
> >
> > On Tue, Dec 13, 2016 at 1:12 PM, Daniele Di Proietto <
> diproiettod at ovn.org>
> > wrote:
> >
> >> 2016-12-12 3:21 GMT-08:00 Sridhar Gaddam <sgaddam at redhat.com>:
> >>> Hello,
> >>>
> >>> In our setup, we are using OVS 2.6+dpdk and are noticing that conntrack
> >> for
> >>> IPv6 traffic is NOT working.
> >>> However, the same use-case works fine for Ipv4 traffic.
> >>>
> >>> We had a look at OVS 2.6 release notes[1], and it mentions that "Basic
> >>> connection tracking for the user space datapath (no ALG, fragmentation
> or
> >>> NAT support yet) is supported".
> >>> There is no explicit mention of IPv6. So, can someone please confirm if
> >>> conntrack for IPv6 is supported in OVS2.6+dpdk?
> >>>
> >>> [1] https://github.com/openvswitch/ovs/blob/master/NEWS
> >>
> >> IPv6 should be supported.  There are a few testcases in the system
> >> userspace testsuite (`make check-system-userspace`) that cover that.
> >>
> >> Could you tell us more about your setup?
> >>
> >
> > ​
> > Sorry for the delay in response. I do not have a local setup to reproduce
> > the issue, so was trying to gather some details from the team that
> > originally noticed this.
> >
> > Basically we are seeing this issue in OpenDaylight use-case when using
> > OVS2.6+dpdk along with conntrack.
> >
> > A simplified view of the use-case is as follows.
> > 1. We have a VM spawned with MAC of "fa:16:3e:6e:9f:b0" and it is sending
> > out a Neighbor Solicitation for another VM on the same network.
> > 2. We use conntrack for tracking the connections, so the Neighbor
> > Solicitation packets initially hit flow (a) in table40, and in table41
> the
> > ct_state matches to "+inv" and are getting dropped (flow e).
> > 3. This behavior (i.e., ct_state=+inv+trk) is seen for ICMPv6 Neighbor
> > Solicitation messages and not for other IPv6 TCP/UDP traffic.
> > 4. Also, this behavior is NOT seen when using OVS kernel datapath (i.e.,
> in
> > table 41, we see that ct_state matches to +new+trk instead of +inv+trk)
> >
>
> This seems to be an inconsistency in handling packets that are not
> tracked. Even Linux kernel conntrack does not track neighbor discovery for
> obvious reasons, but it still attaches a special “notrack” entry with the
> packet and reports it as “NEW”. Flagging ND traffic as “+inv” is probably
> not the right thing to do, but the workaround for now is to not send ND
> packets to conntrack in the first place.
>
>   Jarno
>
> > Srikanth, who is noticing this issue, was also informed by his switch
> team
> > that OVS
> > ​conntrack ​
> > explicitly treats the IPv6 Neighbor Solicitation as an invalid
> connection.
> > For more details, please see the email thread [*] where this issue is
> > discussed.
> >
> > We are trying to see if we should bypass conntrack for NDP packets. In
> the
> > meantime, if you know the specific reason why NS packets are treated this
> > way, can you please let us know?
> >
> > Sample flows:
> > a) table=40, n_packets=246, n_bytes=21156, priority=61010,ipv6,dl_src=fa:
> > 16:3e:6e:9f:b0,ipv6_src=2001:db8:1234:0:f816:3eff:fe6e:9fb0
> > actions=ct(table=41,zone=5002)
> > b) table=41, n_packets=0, n_bytes=0,
> > priority=62020,ct_state=-new+est-rel-inv+trk
> > actions=resubmit(,17)
> > c) table=41, n_packets=0, n_bytes=0,
> > priority=62020,ct_state=-new-est+rel-inv+trk
> > actions=resubmit(,17)
> > d) table=41, n_packets=0, n_bytes=0, priority=12806,ct_state=+new+
> > trk,ipv6,metadata=0x19a80000000000/0x1fffff0000000000
> > actions=ct(commit,zone=5002),resubmit(,17)
> > e) table=41, n_packets=246, n_bytes=21156, priority=62020,ct_state=+inv+
> trk
> > actions=drop
> >
> > [*] https://lists.opendaylight.org/pipermail/netvirt-dev/
> > 2016-December/002527.html
> >
> > Thanks,
> > --Sridhar.​
> >
> >
> >>
> >>>
> >>> Thank you,
> >>> --Sridhar.
> >>> _______________________________________________
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> >>> dev at openvswitch.org
> >>> https://mail.openvswitch.org/mailman/listinfo/ovs-dev
> >>
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>