Make max acceptable client hello size configurable via TlsInspector proto

[eziskind]

This change allows configuring the maximum size of the ClientHello that the TLS inspector will process via the TlsInspector proto configuration. The default value is 16KiB. The initial_read_buffer_size now defaults to this configurable maximum size. No change to current behavior if the field is unset.

Risk Level: low
Testing: unit tests

[repokitteh-read-only]

CC @envoyproxy/api-shepherds: Your approval is needed for changes made to (api/envoy/|docs/root/api-docs/).
envoyproxy/api-shepherds assignee is @markdroth
CC @envoyproxy/api-watchers: FYI only for changes made to (api/envoy/|docs/root/api-docs/).

🐱

Caused by: #42278 was opened by eziskind.

see: more, trace.

[botengyao]

Just catches this from my another PR, thanks for adding this support!

/wait

[agrawroh]

I am curious what's the motivation behind making this configurable. The current value is per the RFC specs. In what cases do we wanna change this?

[eziskind]

I am curious what's the motivation behind making this configurable. The current value is per the RFC specs. In what cases do we wanna change this?

We want to be able to use a lower default value to limit abuse (eg. from DoS attacks) and only allow higher values (up to the RFC spec of 16K) when valid use-cases arise.

[agrawroh]

I am curious what's the motivation behind making this configurable. The current value is per the RFC specs. In what cases do we wanna change this?

We want to be able to use a lower default value to limit abuse (eg. from DoS attacks) and only allow higher values (up to the RFC spec of 16K) when valid use-cases arise.

Make sense. Thanks for sharing.

[KBaichoo]

LGTM. Thank you!

[agrawroh]

This still needs an API LGTM.
cc @abeyad @ggreenway