RPC vulnerable to DoS

[rob-solana]

Problem

RPC is unauthenticated, free, and probably not hardened against DoS attacks, like slow clients, infinite requests, infinite connections, etc.

Proposed Solution

audit and fix? add authentication to RPC?

[mvines]

For now we mitigate this by recommending that staked validators not expose an RPC port, and instead provide RPC from an unstaked "api node"