Host-side virtio-net runtime.

Context

This module is the host-side half of the new networking path:

guest app
  -> guest kernel TCP/IP stack
  -> virtio-net device
  -> libkrun unix-stream bridge
  -> smolvm FrameStreamBridge
  -> shared frame queues
  -> smoltcp gateway/runtime
  -> host sockets / DNS forwarding / TCP relay
  -> external network

Main runtime components:

VirtioNetworkRuntime
├─ FrameStreamBridge
│  ├─ reader thread
│  └─ writer thread
├─ TcpPortListeners
│  └─ one non-blocking accept loop per `-p HOST:GUEST`
├─ Arc<NetworkFrameQueues>
│  ├─ guest_to_host
│  ├─ host_to_guest
│  ├─ guest_wake
│  ├─ host_wake
│  └─ relay_wake
└─ smolvm-net-poll thread
   ├─ VirtioNetworkDevice
   ├─ smoltcp Interface
   ├─ SocketSet
   └─ TcpRelayTable

Component roles:

FrameStreamBridge: translates libkrun's Unix-stream frame protocol into queue operations
TcpPortListeners: accepts host TCP connections for published ports and hands them to the poll loop
NetworkFrameQueues: handoff boundary between threads
VirtioNetworkDevice: adapts those queues to smoltcp's phy::Device
poll thread: acts as the guest-visible gateway and protocol dispatcher
TcpRelayTable: maps guest TCP flows onto host-side relay threads

This runtime is responsible for:

exchanging raw Ethernet frames with libkrun
presenting a gateway endpoint to the guest
handling DNS through a gateway UDP socket and host UDP forwarding
relaying guest TCP connections to host TcpStreams
accepting published host TCP ports and forwarding them into guest TCP connections

smolvm-network 0.8.2

Context