Hi Roman, I think that your idea of setting a route-based MTU _should_ work, and it seems like a bug if it isn't working. There are two places in WireGuard which directly touch the MTU:
1) When we split GSO superpackets up into normal sized packets. This code is supposed to be aware of the per-route MTU you've set, so it shouldn't be a problem. This is the call to skb_gso_segment in device.c. 2) When we pad the packet payload. In this case, we pad it to the nearest multiple of 16, but we don't let it exceed the device MTU. This is skb_padding in send.c. This behavior seems like the bug in your particular case, since what matters here is the route's MTU, not the device MTU. For full 1412 size packets, the payload is presumably being padded to 1424, since that's still less than the device MTU. In order to test this theory, try setting your route MTU, as you've described in your first email, to 1408 (which is a multiple of 16). If this works, let me know, as it will be good motivation for fixing skb_padding. If not, then it means there's a problem elsewhere to investigate too. I'm CC'ing Luis on this email, as he was working on the MTU code a while back. Regards, Jason _______________________________________________ WireGuard mailing list WireGuard@lists.zx2c4.com https://lists.zx2c4.com/mailman/listinfo/wireguard