DDNS option www.tunnelbroker.net doesn't work

[ColinTaylor]

When setting up a 6in4 tunnel from Hurricane Electric it is suggested to also configure DDNS to keep the IPv4 endpoint address updated in case it changes.

This DDNS option doesn't work because it is looking at the WAN interface (i.e. eth0). IIRC in the past the IPv6 address was associated with the WAN interface but that is no longer the case. The firmware now creates a new interface called v6tun0 resulting in the following message repeating in the log.

Feb 27 20:57:24 watchdog: start ddns.
Feb 27 20:57:24 ddns: eth0 has not yet obtained an WAN IPv6 address.(1)
Feb 27 20:57:24 ddns: IP address, server and hostname have not changed since the last update.

I'm guessing that this could be worked around by using a custom DDNS configuration rather than the www.tunnelbroker.net option in the firmware. However, I'm not sure where to get the correct tunnel interface name from. It doesn't seem to appear anywhere in NVRAM. Is it safe to assume that it's always going to be v6tun0?

There is conflicting information in the Merlin wiki about IPv6 and custom DDNS generally. But most of that was posted over ten years ago.

EDIT: Thinking about it a bit more, I guess it doesn't matter what interface is used for IPv6 as we're only actually interested in the IPv4 address changing. Doh!

 

[dave14305]

I guess it could be 0 or 1 (wan unit)?

asuswrt-merlin.ng/release/src/router/shared/rtstate.c at 21d30a367f9c0fb36e813b41f2efedee0671fe42 · RMerl/asuswrt-merlin.ng

Third party firmware for Asus routers (newer codebase) - RMerl/asuswrt-merlin.ng

github.com

 

[Ripshod]

You're right. DDNS client only looks at eth0. Fine and dandy for IPv4, but when it comes to IPv6 it should be looking at br0 (rather than WAN0/1). A particular bug bear of mine and has been rearing it's head on the forums recently.
Glad you sorted it.

 

[ColinTaylor]

Glad you sorted it.

Well I haven't yet. I've just come to realise that I'm overthinking this.

I should ignore the whole "interface name" issue an create a simple custom DDNS script that issues the appropriate CURL update command.