peer reputation

[qcdll]

geth has it, parity has it, py-evm does not have it (yet) we want it

peer reputation should be stateful, and limited to local cluster, ie. we should not convey reputation over the p2p wire, which means clusters have to figure out who to trust on their own

a preliminary implementation is to store currently connected peers and prefer them when restarted this requires the client to store states other than the chain itself

[qizhou]

bitcoin will blacklist a node if it fails to process a command (we could just use close_with_error)

https://github.com/bitcoin/bitcoin/blob/b3f82284ba9035411b3d2d83b507549a4b12cfc8/src/net_processing.cpp#L3273

https://github.com/bitcoin/bitcoin/blob/b3f82284ba9035411b3d2d83b507549a4b12cfc8/src/net_processing.cpp#L3122