//! Different implementations of a common async API for use in arti

//!

//! Currently only async_std, tokio and smol are provided.

#[cfg(feature = "async-std")]

pub(crate) mod async_std;

#[cfg(feature = "tokio")]

pub(crate) mod tokio;

#[cfg(feature = "smol")]

pub(crate) mod smol;

#[cfg(feature = "rustls")]

pub(crate) mod rustls;

#[cfg(feature = "native-tls")]

pub(crate) mod native_tls;

pub(crate) mod streamops;

pub(crate) mod unimpl_tls;

use tor_error::warn_report;

/// Connection backlog size to use for `listen()` calls on IP sockets.

//

// How this was chosen:

//

// 1. The rust standard library uses a backlog of 128 for TCP sockets. This matches `SOMAXCONN` on

//    most systems.

//

// 2. Mio (backend for tokio) previously used 1024. But they recently (confusingly) copied the logic

//    from the standard library's unix socket implementation, which uses different values on

//    different platforms. These values were tuned for unix sockets, so I think we should ignore

//    them and mio's implementation here.

//    https://github.com/tokio-rs/mio/pull/1896

//

// 3. Tor first tries using `INT_MAX`, and if that fails falls back to `SOMAXCONN` (using a global

//    to remember if it did the fallback for future listen() calls; see `tor_listen`).

//

// 4. On supported platforms, if you use a backlog that is too large, the system will supposedly

//    silently cap the value instead of failing.

//

//     Linux:

//     listen(2)

//     > If the backlog argument is greater than the value in /proc/sys/net/core/somaxconn, then it

//     > is silently capped to that value.

//

//     FreeBSD:

//     listen(2)

//     > The sysctl(3) MIB variable kern.ipc.soacceptqueue specifies a hard limit on backlog; if a

//     > value greater than kern.ipc.soacceptqueue or less than zero is specified, backlog is

//     > silently forced to kern.ipc.soacceptqueue.

//

//     OpenBSD:

//     listen(2)

//     > [BUGS] The backlog is currently limited (silently) to the value of the kern.somaxconn

//     > sysctl, which defaults to 128.

//

//     Windows:

//     https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-listen

//     > The backlog parameter is limited (silently) to a reasonable value as determined by the

//     > underlying service provider. Illegal values are replaced by the nearest legal value.

//

//     Mac OS:

//     Archived listen(2) docs

//     https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man2/listen.2.html

//     > [BUGS] The backlog is currently limited (silently) to 128.

//

// 5. While the rust APIs take a `u32`, the libc API uses `int`. So we shouldn't use a value larger

//    than `c_int::MAX`.

//

// 6. We should be careful not to set this too large, as supposedly some systems will truncate this to

//    16 bits. So for example a value of `65536` would cause a backlog of 1. But maybe they are just

//    referring to systems where `int` is 16 bits?

//    https://bugs.python.org/issue38699#msg357957

//

// Here we use `u16::MAX`. We assume that this will succeed on all supported platforms. Unlike tor,

// we do not try again with a smaller value since this doesn't seem to be needed on modern systems.

// We can add it if we find that it's needed.

//

// A value of `u16::MAX` is arguably too high, since a smaller value like 4096 would be large enough

// for legitimate traffic, and illegitimate traffic would be better handled by the kernel with

// something like SYN cookies. But it's easier for users to reduce the max using

// `/proc/sys/net/core/somaxconn` than to increase this max by recompiling arti.

const LISTEN_BACKLOG: i32 = u16::MAX as i32;

/// Open a listening TCP socket.

///

/// The socket will be non-blocking, and the socket handle will be close-on-exec/non-inheritable.

/// Other socket options may also be set depending on the socket type and platform.

///

/// Historically we relied on the runtime to create a listening socket, but we need some specific

/// socket options set, and not all runtimes will behave the same. It's better for us to create the

/// socket with the options we need and with consistent behaviour across all runtimes. For example

/// if each runtime were using a different `listen()` backlog size, it might be difficult to debug

/// related issues.

    use socket2::{Domain, Socket, Type};

    // `socket2::Socket::new()`:

    // > This function corresponds to `socket(2)` on Unix and `WSASocketW` on Windows.

    // >

    // > On Unix-like systems, the close-on-exec flag is set on the new socket. Additionally, on

    // > Apple platforms `SOCK_NOSIGPIPE` is set. On Windows, the socket is made non-inheritable.

        std::net::SocketAddr::V6(_) => {

            // On `cfg(unix)` systems, set `IPV6_V6ONLY` so that we can bind AF_INET and

            // AF_INET6 sockets to the same port.

            // This is `cfg(unix)` as I'm not sure what the socket option does (if anything) on

            // non-unix platforms.

            #[cfg(unix)]

                // If we see this, we should exclude more platforms.

                    e,

                );

        }

    };

    // Below we try to match what a `tokio::net::TcpListener::bind()` would do. This is a bit tricky

    // since tokio documents "Calling TcpListener::bind("127.0.0.1:8080") is equivalent to:" with

    // some provided example code, but this logic actually appears to happen in the mio crate, and

    // doesn't match exactly with tokio's documentation. So here we acknowledge that we likely do

    // deviate from `tokio::net::TcpListener::bind()` a bit.

    // The docs for `tokio::net::TcpSocket` say:

    //

    // > // On platforms with Berkeley-derived sockets, this allows to quickly

    // > // rebind a socket, without needing to wait for the OS to clean up the

    // > // previous one.

    // >

    // > // On Windows, this allows rebinding sockets which are actively in use,

    // > // which allows "socket hijacking", so we explicitly don't set it here.

    // > // https://docs.microsoft.com/en-us/windows/win32/winsock/using-so-reuseaddr-and-so-exclusiveaddruse

    //

    // This appears to be a comment that tokio copied from mio.

    //

    // So here we only set SO_REUSEADDR for `cfg(unix)` to match tokio.

    #[cfg(unix)]

/// Helper: Implement an unreachable NetProvider<unix::SocketAddr> for a given runtime.

#[cfg(not(unix))]

macro_rules! impl_unix_non_provider {

    { $for_type:ty } => {

        #[async_trait]

        impl crate::traits::NetStreamProvider<tor_general_addr::unix::SocketAddr> for $for_type {

            type Stream = crate::unimpl::FakeStream;

            type Listener = crate::unimpl::FakeListener<tor_general_addr::unix::SocketAddr>;

            async fn connect(&self, _a: &tor_general_addr::unix::SocketAddr) -> IoResult<Self::Stream> {

                Err(tor_general_addr::unix::NoAfUnixSocketSupport::default().into())

            }

            async fn listen(&self, _a: &tor_general_addr::unix::SocketAddr) -> IoResult<Self::Listener> {

                Err(tor_general_addr::unix::NoAfUnixSocketSupport::default().into())

            }

        }

    }

}

#[cfg(not(unix))]

pub(crate) use impl_unix_non_provider;