Dropping reply received on <downstream interface> when using -iu/-id

[Brian J. Murrell]

On Tue, 2017-12-12 at 09:54 -0500, Brian J. Murrell wrote:
> I want to use the -iu/-id options with dhcrelay to prevent relays
> from
> relaying (and thus duplicating) requests coming from the network that
> the DHCP server is on[1]:
> 
> # /usr/sbin/dhcrelay -4 -d -pf /var/run/dhcrelay4.pid -id br-guest
> -iu br-lan 10.75.22.247
> 
> When I do this, DHCP Discover requests coming from clients on the br-
> guest interface have their Relay agent IP address set to the address
> of
> the br-guest interface.  When the DHCP server sends back an DHCP
> Offer
> it sends it to the IP address of the br-guest interface on the relay
> machine.  dhcrelay then proceeds to drop that reply:
> 
> Dropping reply received on br-guest
> 
> Is there something I am misunderstanding about how -iu/-id are
> supposed
> to work?
> 
> Cheers,
> b.
> 
> [1] I'm surprised this is not implicit to be honest.  The relay knows
> which network the server is on.  Why is it relaying requests that
> come
> from that network to that network?

Any ideas about this?

b.
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