On 8/26/25 16:03, Petr Menšík via Dnsmasq-discuss wrote:
Hello!
I were just debugging one of our old tests, which tested whether dnsmasq
--dhcp-relay worked. Both for IPv6 and IPv4 addresses. But that test
were written with dhclient originally and worked fined with that.
But you might know ISC dhcp client is deprecated and unsupported. There
is a nice alternative still supported, dhcpcd. But it requires on
difference and that is presence of Router Advertisement Managed flag set.
dnsmasq has support for --enable-ra to send exactly such advertisements,
which will then dhcpcd use to query DHCP server. The problem I see is it
requires configured --dhcp-range for the network.
But using --dhcp-relay and --dhcp-range do not make sense on the same
network, right?
Right.
Unfortunately dhcpcd just won't even try to send DHCP
request to multicast address, until it has indication from the network
it should try it.
I think it would make sense to extend --enable-ra to send RA also from
local addresses specified by --dhcp-relay address.
Agreed.
Or at least have it
explicitly enabled by --ra-param=<device>. The similar problem seems to
have --dhcp-range=::,static. That won't be used by dhcpcd also, because
it did not match correct network.
The --dhcp-range=::,static problem, I don't understand. More explanation
would be good.
Would be patches implementing this desired? Do you know any different
option, how to test dnsmasq --dhcp-relay with dhcpcd?
Definitely will look at patches. I just looked at what needs to be done,
and came up with a five-line addition that looked good, but then
realised that all the timer infrastructure supporting unsolicited RAs is
predicated on having a struct dhcp_context.
The simplest way to fix that might be to add a struct dhcp_relay * to
struct dhcp_context and create a context for each relay address with a
flag set to avoid it's being used anywhere else than in the RA code.
It's a bit messy. I'll keep working on it unless you'd like to have a go.
If you're working on testing dhcp relay, maybe have a look at the new
--dhcp-split-relay option that's in the bleeding edge code. That's IPv4
only.
Cheers,
Simon.
Cheers,
Petr
_______________________________________________
Dnsmasq-discuss mailing list
[email protected]
https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss
