[ovs-discuss] OVN DHCP implementation ignores broadcast bit

Numan Siddique nusiddiq at redhat.com
Wed Jul 5 03:39:48 UTC 2017


On Tue, Jul 4, 2017 at 5:48 PM, Alin Serdean <
aserdean at cloudbasesolutions.com> wrote:

> Hi Alex,
>
>
>
> You can send it to dev at openvswitch.org or create a new pull request via
> github.
>
>
>
> Thanks,
>
> Alin.
>
>
>
> *From:* ovs-discuss-bounces at openvswitch.org [mailto:ovs-discuss-bounces@
> openvswitch.org] *On Behalf Of *Alex Jones
> *Sent:* Tuesday, July 4, 2017 4:00 AM
> *To:* ovs-discuss at openvswitch.org
> *Subject:* [ovs-discuss] OVN DHCP implementation ignores broadcast bit
>
>
>
> Hi All,
>
>   I have OVN up and running (version 2.7), and it is working well except
> for one case. We have a VM which uses its own IP stack and does not accept
> unicast DHCP offers. After examining the OVN code, I found that it
> currently doesn't support the broadcast bit if set by the client.
>
>   I didn't see any bugs regarding this, so I did a patch myself. The patch
> modifies put_dhcp_options to return 2 if the broadcast bit was set in the
> DISCOVER/REQUEST, and 1 if not set (both indicate success). Then I modified
> the current logical flow to check if the return code is 1, then execute the
> current logical flow. I added a new logical flow to handle the broadcast
> bit set case. If the return value from put_dhcp_options is 2, the new flow
> is executed which sets the dest MAC and dest IP to broadcast.
>
>   I'd like to submit this. Do I just post it here?
>
> Alex
>
>
The other simpler approach could be to set "ip4.dst and eth.dst" to
broadcast addresses if broadcast bit is set, giaddr and ciaddr is 0 (as per
the RFC - https://www.ietf.org/rfc/rfc2131.txt) in the function
"pinctrl_handle_put_dhcp_opts" (in ovn/controller/pinctrl.c) and modify
ovn-northd.c to not set the eth.dst and ip4.dst fields in the
S_SWITCH_IN_DHCP_RESPONSE  pipeline.

Probably we should also set ip4.dst to giaddr (to support dhcp relay) if it
is set.

Thanks
Numan


>
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