[LEDE-DEV] Question regarding wan6 interface defaults

[Hans Dedecker]

On Mon, May 29, 2017 at 10:45 AM, Sebastian Moeller <moeller0 at gmx.de> wrote:
> Sear list, dear Hans,
>
> CONTEXT:
> As described in https://forum.lede-project.org/t/build-for-wndr3700v1-v2-wndr3800/64/56?u=moeller0 I had issues with using IPv6 and IPv4 DNS on my home network (deutsche Telekom, vdsl2 @BRAS link). The main symptoms were, that a) IPv6 did not work, and b) DNS even for IPv4 was very unreliable. Unfortunately, for a long time did I spent no time on the IPv6 issue (assuming that missing IPv6 is a more cosmetic thing than getting IPv4 DNS working again*). Last weekend I attempted to tackle the issue again and found your recommendation to change the wan6 iface from eth1 to @wan (see https://bugs.lede-project.org/index.php?do=details&task_id=668). And that "magically" solved all my issues, IPv6 started to work (at least all my internal hosts now get IPv6 addresses with the correct ISP assigned prefix), and more unexpected IPv4 DNS seems to work again (and DDNS also automatically started working). Jow brought up the information that the wan6 ifname default was changed a while back (see https://forum.lede-project.org/t/build-for-wndr3700v1-v2-wndr3800/64/59?u=moeller0, and c118e5edf4301dc303024603dd34d369d9926d6d for the patch and rationale). He also advised that I should bring up the issue of the wan6 default ifname with you.
>
> So, from my limited understanding, the challenge is to have a default that will work out of the box with both native IPv6 (am I right to assume that dslite is basically a sub-variant of native IPv6?) and with IPv6 managed via an IPv4 path, or PPPoE in my case. On the one hand, it makes sense to welcome the future and make native IPv6 a well-supported option, on the other hand many users, as far as I can tell, are still living in the past and are stuck with having to use say PPPoE to get IPv6 up and running.
>
> QUESTIONS:
> 0) What do you believe to currently be the best default configuration for wan6 ifname?
I understand the rationale behind the change done in commit
c118e5edf4301dc303024603dd34d369d9926d6d by Steven. It does make IPv6
independant from IPv4 as before the wan6 interface was aliased on top
of the wan interface; meaning the wan6 interface will only be started
if the wan interface got active. So if DHCP would not work in the wan
network the wan6 interface would not be started which means it's not a
loosely coupled system.
Next to that in deployment scenarios like dslite, map-t, map-e,
464xlat the wan interface is only IPv6 capable making it pointless to
alias the wan6 interface on top of the IPv4 wan interface.
>
> 1) From your perspective is there a way to either make the default configuration work for both situations gracefully?
The main issue is PPP enabled wan interfaces which behave completely
different to DHCP enabled wan interfaces making it hard to create a
default configuration working for all situations IPv6 wise. Whatever
default configuration (aliased wan interface or not) is chosen it has
drawbacks
>
> 2) Say, is there a way to auto detect non-working configurations at run-time and print a hint into the syslog, so the user has an idea how to get things working again, like changing the wan6 ifname?
I don't see an easy way to detect a non-working configuration as the
logic is spread over several subsystems making it complex to detect a
non working configuration
>
> 3) Or could switching the protocol to PPPoE maybe bring up a help text (in a modal dialog?) that informs the user to manually rename the wan6 iface in case of connectivity issues?
>
> 4) Final question, in your bug tracker response you allude to the option to completely delete the wan6 interface to get a (hopefully) working wan_6 autoconfigured; which of the two options, no wan6 or wan6.ifname set to @wan would you recommend?
Both a wan6 interface using a netdev ifname and an autoconfigured
wan_6 can coexist; so there's no need to delete the wan6 interface.
The wan6 interface will not get active when using a PPP wan interface
but the wan_6 interface created by the PPP script will. But at the
moment this will not result into IPv6 connectivity as extra config is
required to add the wan_6 interface to the wan firewall zone. Here we
can improve the user experience by automatically adding the wan_6
interface in the correct firewall zone so that it works seamless form
an end user perspective.

Hans
>
>
> Best Regards
>         Sebastian
>
>
>
> *) Please note my IPv4 DNS issues might still be unsolved, but now at least working IPv6 DNS will pick up the slack mostly.