Stumbled on a regression in the Linux Longterm 6.12.y #kernel when I upgraded some machines yesterday.

#IPv6 UDP packets were no longer being fragmented as though IPV6_DONTFRAG was set when it wasn't which broke a #Librecast test.

The regression wasn't in the mainline kernel so I spent a happy morning bisecting kernels until I found that a patch had been backported in 6.12.31 without backporting two previous related patches.

Reported to the stable maintainers with a test program. Now I wait.