WASI socket support

[tiran]

Feature or enhancement

WASI has limited support for BSD-like sockets in snapshot preview 1. tl;dr it is not possible to open new connections. The WASI runtime must pass a socket file descriptor into the process. Preview 1 supports both connected client-side socket and accept() on bound listening sockets. poll() is available as well, although limited to poll_oneoff. bind, connect, sendto / recvfrom, DNS lookup and NETDB (gethostbyname, getaddrinfo, getservbyname) etc are not available.

Let's document the missing functions and address the remaining issues to get socketserver and simple clients working.

Previous discussion

GH-95179 addressed several missing functions that prevented us to compile the socket module on WASI.

[tiran]

Related WASI / wasmtime issues

• sock_recv always fails with bad fd bytecodealliance/wasmtime#4754, addressed by Implement the remaining socket-related WASI functions. bytecodealliance/wasmtime#4776
• poll() with timeout fails with "timer subscriptions only support monotonic timer" WebAssembly/wasi-libc#318, fixed in Implement I/O timeouts that specify the REALTIME clock. bytecodealliance/wasmtime#4777
• In wasmtime CLI, passing --tcplisten argument breaks --dir bytecodealliance/wasmtime#3936

[brettcannon]

FYI this should be coming in WASI preview2.

[brettcannon]

dicej@118e9d8 shows what should be necessary once wasi-libc has socket support.

[brettcannon]

Closing as this is only possible once WASI-libc lands support.