Add flag to enable logging on rejected gossip message

[saolyn]

What type of PR is this?

Feature

What does this PR do? Why is it needed?

This PR adds a new feature flag to enable logging on rejected gossip messages.

Which issues(s) does this PR fix?

Fixes #11431

Other notes for review

If we add this flag to the docs we need to make sure we add a note about the potential risks of running a node with this flag enabled as pointed out on the issue.
Essentially that this can easily become a potential DoS vector.

[prestonvanloon]

Could you add a function level comment?

What is the intended behavior of this function?

[prestonvanloon]

If you are trying to log the message as a ssz hex string, I don't think printing the *pubsub.Message would work. Could you add a test to ensure the behavior is as expected?

Edit: Here's an example of something testing a log message:

prysm/beacon-chain/state/stategen/setter_test.go

Line 191 in 805473c

require.LogsContain(t, hook, "Exiting mode to save hot states in DB")

Also see how require.LogsContain works. It should be able to read content from fields like when you do log.WithField(...), it should be able to assert that content is present.

[prestonvanloon]

If you want to match Teku's log, they also log the reason or error and topic.

https://github.com/ConsenSys/teku/blob/cdf161742a7abb091ab04fb6c23fee622b9d1df7/infrastructure/logging/src/main/java/tech/pegasys/teku/infrastructure/logging/P2PLogger.java#L50

Edit: Added "and topic". Teku logs the message, topic, and rejection reason / error

[potuz]

If you are trying to log the message as a ssz hex string, I don't think printing the *pubsub.Message would work. Could you add a test to ensure the behavior is as expected?

Yeah I think you want to convert this to a hex string that can be directly fed to a ssz marshaller. Also notice that it's mandatory to have the expected object at least, otherwise we won't know what schema to use to unmarshal

[prestonvanloon]

If you are trying to log the message as a ssz hex string, I don't think printing the *pubsub.Message would work. Could you add a test to ensure the behavior is as expected?

Yeah I think you want to convert this to a hex string that can be directly fed to a ssz marshaller. Also notice that it's mandatory to have the expected object at least, otherwise we won't know what schema to use to unmarshal

I think msg.Data is the ssz payload? It might be snappy compressed, i don't remember, but it's the raw message payload

https://pkg.go.dev/github.com/libp2p/go-libp2p-pubsub@v0.8.1/pb#Message

[nisdas]

This isnt the correct place to check for it, it needs to be in our gossip handler wrapper.

[potuz]

I think msg.Data is the ssz payload? It might be snappy compressed, i don't remember, but it's the raw message payload

https://pkg.go.dev/github.com/libp2p/go-libp2p-pubsub@v0.8.1/pb#Message

Yes but if you print a byte slice with the logger it won't print it as a hex string, and also to decode the ssz you need to know what object the message was.

[nisdas]

LGTM