[ovs-discuss] In 'OVS Faucet Tutorial', router does not work as expected at 'Step 4: Router Broadcasts ARP Request'

[Brad Cowie]

Hi Robin,

I'm part of the faucet team and we reproduced your issue at our end and
have produced a fix/workaround.

What happened is that in faucet 1.6.12 we added a bunch of new packet
handling sanity checks to help improve security of faucet's packet
handling. Packets made by ofproto/trace -generate will have a zero-length
payload which trips some of our sanity checks which will cause us to drop
the packet.

We have added a new flag for disabling this check for cases like the OVS
tutorial where we don't care about security as much as simplicity, this
patch will be included in faucet 1.6.15 which is due to be released in 3
days:

https://github.com/faucetsdn/faucet/pull/1459

I have also submitted a patch to upstream OVS to update the tutorial:

https://mail.openvswitch.org/pipermail/ovs-dev/2018-January/342689.html

Thanks for your find! Hope you find this flag gets everything working again.

Brad

On 25 December 2017 at 14:18, Robin Lee <robinlee.sysu at gmail.com> wrote:

> Hi,
>
> I am new to OVS and just doing 'OVS Faucet Tutorial'.
>
> But everything is OK until 'Step 4: Router Broadcasts ARP Request',
> the router does not send ARP broadcast requrest in my environment.
>
> After I run:
> ovs-appctl ofproto/trace br0 in_port=p1,dl_src=00:01:02:03:
> 04:05,dl_dst=ff:ff:ff:ff:ff:ff,dl_type=0x806,arp_spa=10.
> 100.0.1,arp_tpa=10.100.0.254,arp_sha=00:01:02:03:04:05,arp_tha=ff:ff:ff:ff:ff:ff,arp_op=1
> -generate
>
> ovs-appctl ofproto/trace br0 in_port=p1,dl_src=00:01:02:03:
> 04:05,dl_dst=0e:00:00:00:00:01,udp,nw_src=10.100.0.1,nw_dst=10.200.0.1,nw_ttl=64
> -generate
>
> The sandbox/p4.pcap does not received any ARP request broadcast.
>
>
> My environment is also prepared following the tutorial.
>
> OVS is instalded from Fedora 27 repo:
> Step 4: Router Broadcasts ARP Request'
> and run with tutorial/ovs-sandbox in the git repo.
>
> Faucet is 1.6.14 and run in docker as instructed.
>
> -robin
>
> _______________________________________________
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> discuss at openvswitch.org
> https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
>
>
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