add listener message validation based on semantic

[lambdai]

We have tcp listener, udp listener, api listener in the same Listener message ,
and I am adding another internal listener.

These listeners have their own feature set. e.g. connection_balance_config should not be used by udp listener, filter_chains should only be used by tcp listener (and quic ?), not all sock options are for udp, vice versa.

We don't have adequate validation for the above implicit rules for now.

It's probably good to warn the user upon receiving listener config, starting from "some fields are contradicting or ignored" and eventually reject inconsistent config.

WDYT?

[mattklein123]

Really the entire listener API is broken and in a perfect world needs to get redone, into essentially:

1. Common fields for all listener types
2. oneof of each actual listener type

If you want to start working towards this that would be great. cc @envoyproxy/api-shepherds

[htuch]

+1, this is one of those places that being able to make a more substantial refactor at proto level would be great, but I think we have to live with what we can in the constraints of v3.

[lambdai]

I am adding more data point (or tech debt 😄 ) to this issue is #15376

+1, this is one of those places that being able to make a more substantial refactor at proto level would be great, but I think we have to live with what we can in the constraints of v3.

That being said a validator is a low-hanging fruit under api v3. And the validator might have value in v4 if the proto annotation doesn't provide completeness.

[mattklein123]

IMO we don't need to wait until v4 (since at this point v4 is in the too far in the future / never category in my brain). We can start by adding a oneof for the new listener type and then we can reorganize via deprecations with the minor version proposal and get there over a few years. I will comment on the other PR.

[soulxu]

@lambdai do you need any volunteers on this? I'm looking for task :)

[lambdai]

@lambdai do you need any volunteers on this? I'm looking for task :)

Thank you! Go for it!

[daixiang0]

@soulxu do you still work for this?

[soulxu]

@daixiang0 yea, I'm working on it.