Quiche for QUIC

[Masakazu Kitajo <ma...@apache.org>]

Hi all,

At the ATS Summit last week, the participants reached an agreement that we
should use an external library, Quiche, to support QUIC. I'd like to share
the reasons and make a formal (but lazy) consensus here on this list.

Main reasons to use Quiche:
- We don't have enough resource to implement QUIC protocol by ourselves
right now
- Quiche is actively maintained and used by big players, and it has a large
community
- Instant QUIC support by using an external library is good for making ATS
competitive

What we do:
- Make a feature branch for Quiche support
- Keep our existing QUIC implementation so we can switch back to it in the
future in case we need more flexibility
- Use our existing HTTP/3 implementation over the new QUIC implementation
- Keep Quiche source code out of our repository (use Quiche like
OpenSSL/BoringSSL)

I already have code that handles 100 multiplexed HTTP/3 requests with
Quiche. I'm going to share the code on a feature branch and restart working
on QUIC support if there are no objections or concerns raised.

Thanks,
Masakazu