[ovs-discuss] [ovn] Broken ovs localport flow for ovnmeta namespaces created by neutron

Thu Dec 17 10:05:03 UTC 2020

On Tue, Dec 15, 2020 at 11:39 AM Krzysztof Klimonda <
kklimonda at syntaxhighlighted.com> wrote:

> Hi,
>
> Just as a quick update - I've updated our ovn version to 20.12.0 snapshot
> (d8bc0377c) and so far the problem hasn't yet reoccurred after over 24
> hours of tempest testing.
>

We could reproduce the issue with 20.12 and master. Also this is not
related exclusively to localports but to any port potentially.
Dumitru posted a fix for this:

http://patchwork.ozlabs.org/project/ovn/patch/1608197000-637-1-git-send-email-dceara@redhat.com/

Thanks!
daniel

>
> Best Regards,
> -Chris
>
>
> On Tue, Dec 15, 2020, at 11:13, Daniel Alvarez Sanchez wrote:
>
> Hey Krzysztof,
>
> On Fri, Nov 20, 2020 at 1:17 PM Krzysztof Klimonda <
> kklimonda at syntaxhighlighted.com> wrote:
>
> Hi,
>
> Doing some tempest runs on our pre-prod environment (stable/ussuri with
> ovn 20.06.2 release) I've noticed that some network connectivity tests were
> failing randomly. I've reproduced that by conitnously rescuing and
> unrescuing instance - network connectivity from and to VM works in general
> (dhcp is fine, access from outside is fine), however VM has no access to
> its metadata server (via 169.254.169.254 ip address). Tracing packet from
> VM to metadata via:
>
> ----8<----8<----8<----
> ovs-appctl ofproto/trace br-int
> in_port=tapa489d406-91,dl_src=fa:16:3e:2c:b0:fd,dl_dst=fa:16:3e:8b:b5:39
> ----8<----8<----8<----
>
> ends with
>
> ----8<----8<----8<----
> 65. reg15=0x1,metadata=0x97e, priority 100, cookie 0x15ec4875
>     output:1187
>      >> Nonexistent output port
> ----8<----8<----8<----
>
> And I can verify that there is no flow for the actual ovnmeta tap
> interface (tap67731b0a-c0):
>
> ----8<----8<----8<----
> # docker exec -it openvswitch_vswitchd ovs-ofctl dump-flows br-int |grep
> -E output:'("tap67731b0a-c0"|1187)'
>  cookie=0x15ec4875, duration=1868.378s, table=65, n_packets=524,
> n_bytes=40856, priority=100,reg15=0x1,metadata=0x97e actions=output:1187
> #
> ----8<----8<----8<----
>
> From ovs-vswitchd.log it seems the interface tap67731b0a-c0 was added with
> index 1187, then deleted, and re-added with index 1189 - that's probably
> due to the fact that that is the only VM in that network and I'm constantly
> hard rebooting it via rescue/unrescue:
>
> ----8<----8<----8<----
> 2020-11-20T11:41:18.347Z|08043|bridge|INFO|bridge br-int: added interface
> tap67731b0a-c0 on port 1187
> 2020-11-20T11:41:30.813Z|08044|bridge|INFO|bridge br-int: deleted
> interface tapa489d406-91 on port 1186
> 2020-11-20T11:41:30.816Z|08045|bridge|WARN|could not open network device
> tapa489d406-91 (No such device)
> 2020-11-20T11:41:31.040Z|08046|bridge|INFO|bridge br-int: deleted
> interface tap67731b0a-c0 on port 1187
> 2020-11-20T11:41:31.044Z|08047|bridge|WARN|could not open network device
> tapa489d406-91 (No such device)
> 2020-11-20T11:41:31.050Z|08048|bridge|WARN|could not open network device
> tapa489d406-91 (No such device)
> 2020-11-20T11:41:31.235Z|08049|connmgr|INFO|br-int<->unix#31: 2069
> flow_mods in the last 43 s (858 adds, 814 deletes, 397 modifications)
> 2020-11-20T11:41:33.057Z|08050|bridge|INFO|bridge br-int: added interface
> tapa489d406-91 on port 1188
> 2020-11-20T11:41:33.582Z|08051|bridge|INFO|bridge br-int: added interface
> tap67731b0a-c0 on port 1189
> 2020-11-20T11:42:31.235Z|08052|connmgr|INFO|br-int<->unix#31: 168
> flow_mods in the 2 s starting 59 s ago (114 adds, 10 deletes, 44
> modifications)
> ----8<----8<----8<----
>
> Once I restart ovn-controller it recalculates local ovs flows and the
> problem is fixed so I'm assuming it's a local problem and not related to NB
> and SB databases.
>
>
> I have seen exactly the same which with 20.09, for the same port input and
> output ofports do not match:
>
> bash-4.4# ovs-ofctl dump-flows br-int table=0 | grep 745
>  cookie=0x38937d8e, duration=40387.372s, table=0, n_packets=1863,
> n_bytes=111678, idle_age=1, priority=100,in_port=745
> actions=load:0x4b->NXM_NX_REG13[],load:0x6a->NXM_NX_REG11[],load:0x69->NXM_NX_REG12[],load:0x18d->OXM_OF_METADATA[],load:0x1->NXM_NX_REG14[],resubmit(,8)
>
>
> bash-4.4# ovs-ofctl dump-flows br-int table=65 | grep 8937d8e
>  cookie=0x38937d8e, duration=40593.699s, table=65, n_packets=1848,
> n_bytes=98960, idle_age=2599, priority=100,reg15=0x1,metadata=0x18d
> actions=output:737
>
>
> In table=0, the ofport is fine (745) but in the output stage it is using a
> different one (737).
>
> By checking the OVS database transaction history, that port, at some
> point, had the id 737:
>
> record 6516: 2020-12-14 22:22:54.184
>
>   table Interface row "tap71a5dfc1-10" (073801e2):
>     ofport=737
>   table Open_vSwitch row 1d9566c8 (1d9566c8):
>     cur_cfg=2023
>
> So it looks like ovn-controller is not updating the ofport in the physical
> flows for the output stage.
>
> We'll try to figure out if this happens also in master.
>
> Thanks,
> daniel
>
>
> --
>   Krzysztof Klimonda
>   kklimonda at syntaxhighlighted.com
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>
>
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