`/eth/v1/node/peers` returns null ENR for all peers

[eth2353]

Describe the bug

Hey team, I seem to be getting "enr": null for all peers when calling this endpoint. I tried on multiple instances (v1.40+) across different networks with the same result. (Also tried on one v1.41.0-rc.0 node)

The peer_id and last_seen_p2p_address do have values, it's just the ENR that seems not to be getting filled properly.

Expected behavior

The enr field value is filled with the peer's ENR for every peer.

Steps to reproduce

curl http://lodestar/eth/v1/node/peers

Additional context

No response

Operating system

Linux

Lodestar version or commit hash

v1.40.0

[eth2353]

@lodekeeper mind taking a look at this?

[nflaig]

for reference, this is a known issue and has been the case for at least 5 years, I don't think we ever returned the ENR

lodestar/packages/beacon-node/src/api/impl/node/utils.ts

Lines 12 to 13 in 6a85a50

	// TODO: figure out how to get enr of peer
	enr: null,

[lodekeeper]

Fix is up in #9046 — the ENR field in /eth/v1/node/peers will now be populated from the discv5 discovery cache and routing table.

Tested locally with a mainnet beacon node (checkpoint sync + engineMock): 37/37 connected peers (100%) returned a valid ENR. Peers discovered through discv5 (the common case for outbound connections) will have their ENR populated; inbound-only peers not seen through discv5 will still return null per the spec.

PR is awaiting CI + review.