Re: [REGRESSION] IPv6 RA default router advertisement fails after kernel 6.12.42 updates

Hi Greg,

Thanks for the quick reply.

This regression has been reproduced on Linux 6.12.42 as shipped with
OpenWrt. Currently, OpenWrt only provides kernels from the 6.12.y
stable series, so I was only able to verify on 6.12.42.

I am looping in the networking/IPv6 maintainers so the right people
can take a look at this issue.

Best regards,
gongzi miao

Greg KH [off-list ref] 于2025年8月18日周一 20:25写道：

On Mon, Aug 18, 2025 at 08:03:00PM +0800, 喵公子 wrote:

quoted

Hi,

While testing Linux kernel 6.12.42 on OpenWrt, we observed a
regression in IPv6 Router Advertisement (RA) handling for the default
router.

Affected commits

The following commits appear related and may have introduced the issue:

ipv6: fix possible infinite loop in fib6_info_uses_dev()：
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.12.42&id=db65739d406c72776fbdbbc334be827ef05880d2

ipv6: prevent infinite loop in rt6_nlmsg_size()：
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.12.42&id=cd8d8bbd9ced4cc5d06d858f67d4aa87745e8f38

ipv6: annotate data-races around rt->fib6_nsiblings：
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.12.42&id=0c58f74f8aa991c2a63bb58ff743e1ff3d584b62

Does this also happen on the latest kernel releases?

Also, please always include the developers/maintainers/mailing list of
the subsystem where you find an issue with.  Otherwise you are not going
to reach the developers who can help you out.

thanks,

greg k-h