dhcpcd-discuss

Hi David

On 20/05/2017 09:55, David Williams wrote:
> I've been having a problem with router solicitations sent out by dhcpcd
> onto a ppp interface being ignored. I did some captures and found that
> dhcpcd was adding a source address option with all zeros which is
> against my understanding of RFC4861. I've patched the router
> solicitation routine to detect an all zero hardware address and omit the
> source address option in that case. Please find attached patch.
>
> As background the ppp interface was set up using pppd version 2.4.7 on
> Gentoo Linux 4.7.10-hardened.
>
> Hope this is useful.

I agree with your diagnosis, I disagree with your patch.
https://tools.ietf.org/html/rfc4861#section-6.1.1

   A router MUST silently discard any received Router Solicitation
   messages that do not satisfy all of the following validity checks:

      - If the IP source address is the unspecified address, there is no
        source link-layer address option in the message.

So by excluding the option as you do, the message is still invalid.
As such, we can't actually send a Router Solicitation.

I've created task https://dev.marples.name/T119 and a patch to work on 
this here:
https://dev.marples.name/D114

It's not PPP specific, as dhcpcd shouldn't be using these addresses for 
anything, as you point out.

But, are you saying you get a reply without the option?
Can I see some packet captures please? Ideally a binary capture I can 
see in wireshark.

Thanks

Roy