IPv6 prefix delegation not working with 24.7.1-.3

[Context0881]

Issue persist with 24.7.8 with erratic IPv6 prefix avaibility

[lostcontrol]

Not sure if this is 100% related but I'm also such with 24.7.5_3 because this is the last version that works with IPv6 for me. Somehow I never get a correct IPv6 gateway with > 24.7.5_3. I suspect it is related to some changes in dhcp6c since a newer version was released with 24.7.6. I didn't have time to look closer at the issue so far unfortunately.

[Bash5244]

I am very certain the breakage is introduced by this code.

https://github.com/opnsense/dhcp6c/compare/v20240919...v20241008

I gonna do this revert (back to 0919 release) as long as there is no newer release (newer than 1008)from the dhcp6c.

opnsense-revert -r 24.7.5 dhcp6c    # take you back to dhcp6c 0919 version

[franco]

Well if you see any of those messages in the log and then it stops then maybe. If you don't see the log messages code that isn't executed is likely not the issue. Every change was confirmed by the respective reporter, too. It feels like playing whac-a-mole: fix one provider break another, but then again it has always been this way.

I still think the random number changes are the culprit (from "random" static to actually random as per RFC), but for the right reasons and not the wrong ones. If anyone wants to poke at this be my guest. Most I have seen is ISPs not repying meaning that they probably don't like the timings which is unfortunate but impossible to debug from the client side.


Cheers,
Franco

[lostcontrol]

Not sure if this is 100% related but I'm also such with 24.7.5_3 because this is the last version that works with IPv6 for me. Somehow I never get a correct IPv6 gateway with > 24.7.5_3. I suspect it is related to some changes in dhcp6c since a newer version was released with 24.7.6. I didn't have time to look closer at the issue so far unfortunately.

I took some time to look into my issue. I reverted dhcp6c as proposed but this didn't change the problem for me. Doing some googling, I realized that the default gateway setting is not propagated via DHCPv6 but RA. I checked for RA using tcpdump and noticed that I got some from fe80::c28c:8802:a581:8b62 which was the gateway OPNsense used when my IPv6 connectivity was broken. Looking at the NDP I noticed that the corresponding MAC address was the one of... my Draytek DSL modem :o The modem is configured in bridge mode and somehow sent RA to the router!? RA from my ISP somehow didn't make it through with > 24.7.5_3!? Long story short, I disabled IPv6 on the Draytek modem, reverted to my 24.7.8 snapshot and tada... IPv6 works :)

I will be migrated to FTTH next month so this would have solved itself eventually but I learned a lot by debugging this.