[ovs-dev] [PATCH ovn v4] Broadcast DHCPREPLY when BROADCAST flag is set

Ben Pfaff blp at ovn.org
Thu Mar 5 20:15:45 UTC 2020

On Thu, Mar 05, 2020 at 02:56:17PM -0500, Ihar Hrachyshka wrote:
> As per RFC2131, section 4.1:
>    A server or relay agent sending or relaying a DHCP message directly
>    to a DHCP client (i.e., not to a relay agent specified in the
>    'giaddr' field) SHOULD examine the BROADCAST bit in the 'flags'
>    field.  If this bit is set to 1, the DHCP message SHOULD be sent as
>    an IP broadcast using an IP broadcast address (preferably 0xffffffff)
>    as the IP destination address and the link-layer broadcast address as
>    the link-layer destination address.
> This patch changes destination IP address to when client
> set BROADCAST flag in their DHCPREQUEST. Note: the offered IP address is
> still part of the DHCP payload.
> Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=1801006
> Signed-off-by: Ihar Hrachyshka <ihrachys at redhat.com>

Does the reply actually get broadcast to all the VMs in the logical
network?  Or is it just the IP destination that gets changed and it's
actually unicast just to the requester?  The latter is what I'm inclined
to prefer.

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