Sven, Amazing. I applied your patch (applied cleanly to 2023.3), recompiled my firmware (I had to modify the package to use 2023.3, and to exclude outdated patches -- your jumbo-frames patch is the only one I applied), and so far it's working great I can see that bat0 is able to take an MTU of 1504, which is what I wanted.
I didn't try to violate the MTU "space" by reducing my hard-if MTU, and I don't use NC or the other suspect cases you suggested needed testing, but I'm willing to give back and try some additional configurations, if you can give me a list of test cases (and what you want to see). Thank you so much for maintaining this project, and for your prompt and helpful reply. I'd love to help close this issue, as it looks to me like you likely have created a good patch. I naively don't see any likely reasons why it won't always work. The logic seems right to me. Respectfully, Rich
