Windows broker: guest socket() fails EIO — no SocketProvider (UnsupportedSocketProvider) #1663

Environment

• Branch: ulitebox, commit 4276ac3
• Host: Azure Standard_D4s_v5 (4 vCPU / 16 GiB), Windows 11 Pro 24H2 x64 Gen2
• Guest: Linux Python 3.12 (python:3.12-slim rootfs via litebox-packager OCI)
• Entry: litebox-broker-userland.exe --fs-initial-files .\agent-rootfs.tar
--allow-tcp-destination 10.0.2.1/32:4000
--runner litebox_runner_linux_on_windows_userland.exe

Expected

Guest socket(AF_INET, SOCK_STREAM) succeeds. Guest (10.0.2.15) can connect via host gateway 10.0.2.1 to host-loopback services per broker destination policy.

Actual

Socket creation fails immediately, before connect:

      OSError: [Errno 5] Input/output error
        File "/usr/local/lib/python3.12/socket.py", line 233, in init
          _socket.socket.init(self, family, type, proto, fileno)

Minimal repro (no agent, no network target)

      litebox-broker-userland.exe --fs-initial-files .\agent-rootfs.tar \
        --runner litebox_runner_linux_on_windows_userland.exe \
        /usr/local/bin/python3 -c 'import socket; s=socket.socket(socket.AF_INET, socket.SOCK_STREAM); print("socket ok")'

Result: same Errno 5 panic path, runner exit 101.
Success marker after fix: prints socket ok.

Root cause (from source at this commit)

• litebox_broker_userland/src/builder.rs: platform_socket_provider
returns LinuxSocketProvider only on Linux; all other targets get
litebox_broker_core::socket::UnsupportedSocketProvider.
• UnsupportedSocketProvider::create() returns
BrokerError::UnsupportedOperation (litebox_broker_core/src/socket.rs),
which guest maps to EIO.
• litebox_broker_platform_windows_userland provides only sync
primitives; no Winsock provider exists. Policy/routing layer
(SocketPolicy::guest_network, HOST_GATEWAY_IPV4_ADDRESS 10.0.2.1,
host_socket_destination loopback translation) is present but has
no Windows host provider behind it.

Suggested fix

Implement WindowsSocketProvider in litebox_broker_platform_windows_userland (Winsock, WSAPoll or IOCP reactor) satisfying SocketProvider + broker readiness, mirroring litebox_broker_platform_linux_userland/src/socket.rs (~2108 lines plus tcp.rs/udp.rs), wired in builder.rs cfg(windows).

Workaround

None on Windows. Live guest networking requires Linux host provider today.

Notes

I asked my Agent if this was valid and the answer that I got back was "yes, and here's why".