Stream: git-wasmtime

Topic: wasmtime / issue #12475 p3: Inconsistent behavior in sock...

Wasmtime GitHub notifications bot (Jan 29 2026 at 22:19):

saulecabrera opened issue #12475:

Test Case

With the latest Wasmtime dev version, the following test:

async fn test_wrong_address_family(family: IpAddressFamily) {
    let sock = UdpSocket::create(family).unwrap();

    let addr = match family {
        IpAddressFamily::Ipv4 => IpSocketAddress::localhost(IpAddressFamily::Ipv6, 0),
        IpAddressFamily::Ipv6 => IpSocketAddress::localhost(IpAddressFamily::Ipv4, 0),
    };

    let result = sock.send(vec![0; 1], Some(addr)).await;
    assert!(matches!(result, Err(ErrorCode::InvalidArgument)));
}

Passes on macOS, but fails on Ubuntu/Windows.

According to the spec: invalid-argument should be returned if the remote-address has the wrong address family. (EAFNOSUPPORT)

Wasmtime GitHub notifications bot (Jan 29 2026 at 22:19):

saulecabrera added the bug label to Issue #12475.

Wasmtime GitHub notifications bot (Jan 29 2026 at 22:19):

saulecabrera added the wasi label to Issue #12475.

Wasmtime GitHub notifications bot (Jan 29 2026 at 22:20):

saulecabrera edited issue #12475:

With the latest Wasmtime dev version, the following test:

async fn test_wrong_address_family(family: IpAddressFamily) {
    let sock = UdpSocket::create(family).unwrap();

    let addr = match family {
        IpAddressFamily::Ipv4 => IpSocketAddress::localhost(IpAddressFamily::Ipv6, 0),
        IpAddressFamily::Ipv6 => IpSocketAddress::localhost(IpAddressFamily::Ipv4, 0),
    };

    let result = sock.send(vec![0; 1], Some(addr)).await;
    assert!(matches!(result, Err(ErrorCode::InvalidArgument)));
}

Passes on macOS, but fails on Ubuntu/Windows.

According to the spec: invalid-argument should be returned if the remote-address has the wrong address family. (EAFNOSUPPORT)

Wasmtime GitHub notifications bot (Jan 29 2026 at 22:38):

saulecabrera commented on issue #12475:

For completeness, this is the error on Ubuntu:

[src/bin/sockets-udp-send.rs:21:5] &result = Err(
    ErrorCode {
        code: 2,
        name: "not-supported",
        message: "The operation is not supported.\n\n          POSIX equivalent: EOPNOTSUPP",
    },
)

Wasmtime GitHub notifications bot (Jan 30 2026 at 19:24):

alexcrichton commented on issue #12475:

Should this perhaps be a case where the spec is changed to allow more error codes for this situation? I never quite know how to best thread the needle but translating a native EAFNOSUPPORT to not-supported here doesn't seem entirely unreasonable to me

Wasmtime GitHub notifications bot (Jan 30 2026 at 19:38):

bjorn3 commented on issue #12475:

I believe on macOS an ipv6 socket can actually connect to ipv4 addresses (and by default listening on an ipv6 socket will also listen on ipv4) The IPV6_V6ONLY option disables this behavior.

Wasmtime GitHub notifications bot (Jun 04 2026 at 16:05):

rvolosatovs commented on issue #12475:

I believe on macOS an ipv6 socket can actually connect to ipv4 addresses (and by default listening on an ipv6 socket will also listen on ipv4) The IPV6_V6ONLY option disables this behavior.

IPV6_V6ONLY behavior is actually the spec requirement: https://github.com/WebAssembly/WASI/blob/a1fc383d01eabaf3fac01de03c0ab1a01bfdd099/proposals/sockets/wit-0.3.0-draft/types.wit#L178-L180

   /// Similar to `socket(AF_INET or AF_INET6, SOCK_STREAM, IPPROTO_TCP)`
   /// in POSIX. On IPv6 sockets, IPV6_V6ONLY is enabled by default and
   /// can't be configured otherwise.

Wasmtime GitHub notifications bot (Jun 04 2026 at 16:11):

bjorn3 commented on issue #12475:

That was added a month after my comment in https://github.com/WebAssembly/WASI/pull/884.

Wasmtime GitHub notifications bot (Jun 09 2026 at 19:08):

alexcrichton closed issue #12475:

With the latest Wasmtime dev version, the following test:

async fn test_wrong_address_family(family: IpAddressFamily) {
    let sock = UdpSocket::create(family).unwrap();

    let addr = match family {
        IpAddressFamily::Ipv4 => IpSocketAddress::localhost(IpAddressFamily::Ipv6, 0),
        IpAddressFamily::Ipv6 => IpSocketAddress::localhost(IpAddressFamily::Ipv4, 0),
    };

    let result = sock.send(vec![0; 1], Some(addr)).await;
    assert!(matches!(result, Err(ErrorCode::InvalidArgument)));
}

Passes on macOS, but fails on Ubuntu/Windows.

According to the spec: invalid-argument should be returned if the remote-address has the wrong address family. (EAFNOSUPPORT)

Wasmtime GitHub notifications bot (Jun 13 2026 at 08:35):

badeend commented on issue #12475:

That was added a month after my comment WebAssembly/WASI#884.

FWIW, the IPV6_V6ONLY requirement was already part of the spec before that. That PR only reformats the documentation.

---

The reason why the OP's issue surfaces now is for the same reason as https://github.com/bytecodealliance/wasmtime/issues/12568; the validation was missing in the P3 implementation. And the validation was hiding the fact that we didn't set IPV6_V6ONLY correctly.

Last updated: Jul 29 2026 at 05:03 UTC