Teku is sending exited validators to MEV-Boost but should only send active or pending ones

[jclapis]

Description

I recently set up MEV-Boost for Goerli/Prater. I have several exited validators on Prater (such as https://prater.beaconcha.in/validator/0xb00c002d0770d507af4b4d61d259ae44432745b7a9d693d167efbdc7e39e4c012f584c40d866cacf4557a08e86284e31) and during Teku's validator registration process, it sends this validator over to MEV-Boost which causes it to fail.

According to the official spec, only active or pending validators should be sent to the builder during validator registration.

Here are MEV-Boost's logs:

mev-boost_1      | time="2022-08-12T18:22:12Z" level=info msg="http: GET /eth/v1/builder/status 200" duration=0.059087851 method=GET module=service path=/eth/v1/builder/status status=200
mev-boost_1      | time="2022-08-12T18:22:24Z" level=warning msg="error calling registerValidator on relay" error="HTTP error response: 400 / {\"code\":400,\"message\":\"not a known validator: 0xb00c002d0770d507af4b4d61d259ae44432745b7a9d693d167efbdc7e39e4c012f584c40d866cacf4557a08e86284e31\"}\n" method=registerValidator module=service numRegistrations=36 ua=okhttp/4.9.2 url="https://builder-relay-goerli.flashbots.net/eth/v1/builder/validators?id=rocketpool"
mev-boost_1      | time="2022-08-12T18:22:24Z" level=info msg="http: POST /eth/v1/builder/validators 502" duration=0.131684409 method=POST module=service path=/eth/v1/builder/validators status=502

Unfortunately, Teku's BN doesn't log this failure at all so it was purely a coincidence that I noticed it while investigating the behavior of other clients. I would advise adding logs on validator registration failures.

I will note that this used a Teku BN with a remotely-connected Lighthouse VC (v2.5.1). Not sure if that matters here.

I reported this to Flashbots, who pointed me to the builder API spec above.

This issue is also present in Lighthouse and Nimbus.

Steps to Reproduce (Bug)

• Exit a validator
• Start Teku, which will load the keys for the exited validator
• Connect to MEV-boost as the block builder
• Observe the above behavior

Expected behavior:
Teku should only register active and pending validators

Actual behavior:
Teku is registering every connected validator

Frequency:
100% of the time

Versions (Add all that apply)

• Software version: v22.8.0
• Java version: Whatever the Docker container uses
• OS Name & Version: Debian 11 x64
• Docker Version: 20.10.17
• Cloud VM, type, size: N/A

[rolfyone]

Thanks for raising this, I did comment on the builder issue as well, but just for context here:

Added a comment to flashbots/mev-boost#245 - its possible to filter based on the head state from the BN (on the BN side before we call the builder api), but it's likely a better solution that the builder api is a little tolerant.
I filled in some context about active and pending statuses, and noted that active includes active_slashed which will not be doing any duties either.
If only active and pending is a fixed requirement on the builder side, we may need to update ProposersDataManager.updateValidatorRegistrations, and we'd likely want to clarify some of the behaviours in the rest api potentially.