Userspace networking had been around for quite a few years, yet didn't seem to have taken off, despite all the great benchmarks... I think the main blocker is that you cannot make apps use it without hacks. It looks like Snap requires a custom library that probably doesn't even have to implement BSD sockets, since that's something you don't have to care about at Google.

Some years ago I recall looking into this, and it looked kernel had limitations in higher speed ethernet (must had been 50GbE at the time), and it came down to single-threaded nature of the TCP/IP stack in the kernel at the time. So that's been one of the drivers for experiments in userspace. Looks like that might now be the case now [1], but if someone has more specific info I'd be quite curious to hear.

[1]: https://www.phoronix.com/scan.php?page=news_item&px=Broadcom...