GRO/GSO on Linux

[M0dEx]

Currently, with high throughput workloads, the Linux implementation struggles to get beyond ~ 1.3 Gbps of throughput (could be marginally more with nothing but rust-tun).

This could be improved by implementing GRO and GSO for TCP and UDP packets, which has been added and benchmarked by Tailscale in the TUN driver of wireguard-go, leading to significant improvements in throughput, as described in the following articles:

• https://tailscale.com/blog/throughput-improvements/
• https://tailscale.com/blog/more-throughput/

This would be a non-trivial change, but I might take it on later this year, as I would really love to use it in quincy, which uses rust-tun.

This relates to M0dEx/quincy#10

[GyulyVGC]

This is a feature I'm really interested in as well!