QUIC connection migration

[Sergey Kandaurov]

> On 1 Jun 2023, at 00:28, claire liu <claireecf at gmail.com> wrote:
> 
> Hi dev team,
> I am testing the QUIC connection migration feature. Whether I turn on or off 'quic_bpf', it supports connection migration. Are there any other configurations to control QUIC connection migration? Thanks in advance.
> 

quic_bpf allows connection migration to work with multiple worker
processes, it doesn't affect connection migration itself.
In early development, there was a directive to disable migration.
It was used to send a corresponding QUIC transport parameter
"disable_active_migration" to signal it is not supported by server
and also to drop incoming packets from an unknown path.
Later, it was reconsidered to always allow connection migration.
Specification is a bit vague on this point: although disabled,
it still can be allowed to accept packets from new paths,
see RFC 9000, section 9:
: the endpoint MUST either drop the incoming packets on that path
: without generating a Stateless Reset or proceed with path validation
: and allow the peer to migrate.
Later the directive was removed to simplify configuration, and also
because connection migration is supported.
Though, it might be used for fine-tuning configurations with multiple
worker processes to disable migration where quic_bpf isn't available.

-- 
Sergey Kandaurov