implement "quic-forward-proxy" service that allows n inbound senders to use(share) staked identity

[grooviegermanikus]

Problem:

• TPU has complex logic to assign connection capacity to TPU clients; this considers stake vs unstaked connections, per peer/per node limits, QUIC stream limits
• staking nodes is a potential security problem; should be minimized
• lite-rpc nodes cannot be stateless/scaled with stake assigned

Proposed solution overview:

Architektur overview:

• many TPUs (solana validators)
• one quic-forward-proxy
• many clients
• clients connect to proxy and proxy connects to TPU

Proposed solution details:

• Implement a QUIC proxy service (independently deployable network service).
• QUIC proxy receivers transactions from its clients and forwards them to TPU via QUIC.
• dedicated protocol needs to be used between clients and the Quic Proxy.
• Service must accept multiple inbound QUIC connections.
• Clients of the proxy service might be lite-rpc instances, lite-rpc-library users or other components (e.g. bots).
• Proxy Service must use its assigned stake identity to TLS-sign the connection to the TPU target node.
• Senders must specify the TPU target node (based on leader schedule known by the client; usually be using lite-rpc-library).
• Must allow for transactions.
• expect that one instance of the service is running (or at least needs to appear as single IP-Address/peer to the TPU)
• the quic-proxy must be powerful enough to take all ingress traffic
• No streaming is required. Use quic multiplexing to connect to TPU.
• authentication: QUIC certificate whitelisting / root-CA pinning (quic-forward-proxy: authenticate clients #167)

Similar approaches:

note: there is a similar/alternative approach for client-TPU-Interaction using reverse-proxy model,
"node must advertise to gossip for inbound traffic that is designated for leader"

[grooviegermanikus]

use Rust, might run in kernel

[grooviegermanikus]

See solana code:
quic.rs, compute_max_allowed_uni_streams: l.222
"max_connections_per_peer"

[grooviegermanikus]

POC on lite-rpc branch

[grooviegermanikus]

merged - see https://github.com/blockworks-foundation/lite-rpc/tree/main/quic-forward-proxy