Optimize Guest

[lacraig2]

This PR does the following:

• switches the guest to use a single-threaded tokio engine
• switches the guest to use copy_bidirectional
• adds a sleep in a hot path in the host
• pins our csv to an older version because of rust version restrictions (relevant for MIPS)

[Copilot]

Pull Request Overview

This PR refactors the UDP proxying implementation from per-client vsock streams to a multiplexed architecture where a single vsock stream handles all UDP clients for a given service. The changes also optimize the guest runtime to use a single-threaded executor instead of multi-threaded.

Key changes:

• Introduced UdpMuxPacket structure to multiplex UDP packets over a single vsock stream with client address information
• Replaced HostRequest::Forward with separate ForwardTcp and ForwardUdpMux variants to distinguish between TCP and UDP multiplexed forwarding
• Changed guest runtime from multi-threaded to single-threaded for better resource efficiency

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/main.rs	Added UdpMuxPacket struct, split HostRequest::Forward into ForwardTcp and ForwardUdpMux, changed guest runtime to single-threaded, added EOF check in read_event
src/host.rs	Refactored UDP proxy from per-client to multiplexed architecture, updated TCP forwarding to use new ForwardTcp variant, added sleep on empty line reads
src/guest.rs	Implemented multiplexed UDP proxy with per-client task spawning, replaced manual TCP forwarding with tokio::io::copy, updated to handle new request variants
Cargo.toml	Pinned dependency versions and added serde_bytes for efficient binary serialization

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[Copilot]

When a send fails to an existing client, the client is removed but the packet data is lost. This could lead to dropped packets. Consider either logging the dropped packet or attempting to recreate the client handler to process the packet.

Suggested change

	if tx.send(packet.data).await.is_err() {
	if tx.send(packet.data).await.is_err() {
	error!(
	client = %client_addr,
	size = packet.data.len(),
	"Dropped packet: failed to send to client, removing client handler"
	);

[Copilot]

Using an exact version requirement (=1.3.0) prevents patch updates that could include bug fixes. Consider using a more flexible version specifier like '1.3' or '~1.3.0' unless there's a specific reason to pin to this exact version.

Suggested change

	csv = "=1.3.0"
	csv = "1.3"