Validators should not serve BlockRequests

[DrZoltanFazekas]

Syncing nodes can't distinguish the current validators from other nodes since their latest block contains an outdated validator set. But they can advertise that they don't have any blocks so that nodes don't send them request for blocks that they want to download.

[shawn-zil]

@DrZoltanFazekas
If I understood this issue, it is that nodes which are busy catching up (syncing), should not be queried for blocks, since their database is incomplete anyway. The requestor distributes the requests across different peers, and does not know which ones are syncing.

Is this right?

Also, am I correct in thinking that nodes which are busy syncing, should probably not participate in other requests (e.g. voting) either since they're still syncing.