dhcpcd-discuss

On 07/12/2017 22:59, Neal P. Murphy wrote:
> With respect to linx config bits, this might be helpful:
>    http://tldp.org/HOWTO/html_single/Linux+IPv6-HOWTO/#proc-sys-net-ipv6.
> In short, if multiple IFs are used and forwarding is turned on (i.e., the system is a router), the kernel ignores RAs and performs no autoconfig; Smoothwall is a router and has forwarding turned on (double-checked). I don't see anything in the kernel config (either 3.16 running or 3.4 headers) that would mess this up; but I could be blind today.

autoconfig also affects the link-local address which it would still need 
for any IPv6 communication. That is what dhcpcd is trying to disable so 
it can use stable private addresses for link-local.

So if you're correct and this message is because it's a router then imho 
that's a kernel bug and dhcpcd is just reporting it.
I think I'll just leave this as it is for now, you only see the message 
when debugging is enabled and it's still valid.

> I pulled and built master. Good news: -4 now properly doesn't listen on IPv6.

Yay!

> dhcpcd doesn't report that it assigned ...:960::1/64 to eth3 or that it added the route, but it does report that it completed DAD for eth3. Nor does it report removing these things when exiting. Is it possible that dhcpcd somehow doesn't track this? Or doesn't track it in *my* case because I'm doing something odd?

Correct.
dhcpcd won't remove addresses or routes it didn't add, unless they will 
conflict with what it wants to add (which on Linux isn't that too much 
thanks to route metrics).

Now if dhcpcd loses track of something - like say you restarted it 
without dropping prior and you get a different delegation, then this 
won't be cleaned up as dhcpcd has stopped tracking it. I don't intend to 
fix that case because it could potentially do something nasty as it 
would be guesswork.

> Curious. When I 'ip link set dev eth3 down', it detects lost carrier and *does* remove everything (all routes, all global addresses, and doesn't touch the LL routes). Nice and clean. But when I 'ip link set dev eth3 up'; it restores everything *except* the /64 delegated to eth3 and the route for it.

That's the linux kernel un-helpfully doing that.

So I think that's all the problems resolved now yes?
I did just solve a problem where the non debug case spammed syslog each 
DHCP6 reply when there was a prefix delegation if you're interested in that.

Roy