TcpSocket: add set_linger method

inspired by how it was done in net2

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>

src/net/tcp/socket.rs

@@ -4,6 +4,7 @@ use crate::sys;
 use std::io;
 use std::mem;
 use std::net::SocketAddr;
+use std::time::Duration;
 #[cfg(unix)]
 use std::os::unix::io::{AsRawFd, RawFd, FromRawFd};
 #[cfg(windows)]
@@ -80,6 +81,11 @@ impl TcpSocket {
     pub fn set_reuseaddr(&self, reuseaddr: bool) -> io::Result<()> {
         sys::tcp::set_reuseaddr(self.sys, reuseaddr)
     }
+
+    /// Sets the value of `SO_LINGER` on this socket.
+    pub fn set_linger(&self, dur: Option<Duration>) -> io::Result<()> {
+        sys::tcp::set_linger(self.sys, dur)
+    }
 }
 
 impl Drop for TcpSocket {

src/sys/shell/tcp.rs

@@ -1,5 +1,6 @@
 use std::io;
 use std::net::{self, SocketAddr};
+use std::time::Duration;
 
 pub(crate) type TcpSocket = i32;
 
@@ -31,6 +32,10 @@ pub(crate) fn set_reuseaddr(_: TcpSocket, _: bool) -> io::Result<()> {
     os_required!();
 }
 
+pub(crate) fn set_linger(_: TcpSocket, _: Option<Duration>) -> io::Result<()> {
+    os_required!();
+}
+
 pub fn accept(_: &net::TcpListener) -> io::Result<(net::TcpStream, SocketAddr)> {
     os_required!();
 }

src/sys/unix/tcp.rs

@@ -1,6 +1,7 @@
 use std::io;
 use std::mem::{size_of, MaybeUninit};
 use std::net::{self, SocketAddr};
+use std::time::Duration;
 use std::os::unix::io::{AsRawFd, FromRawFd};
 
 use crate::sys::unix::net::{new_socket, socket_addr, to_socket_addr};
@@ -58,6 +59,21 @@ pub(crate) fn set_reuseaddr(socket: TcpSocket, reuseaddr: bool) -> io::Result<()
     Ok(())
 }
 
+pub(crate) fn set_linger(socket: TcpSocket, dur: Option<Duration>) -> io::Result<()> {
+    let val: libc::linger = libc::linger {
+        l_onoff: if dur.is_some() { 1 } else { 0 },
+        l_linger: dur.map(|dur| dur.as_secs() as libc::c_int).unwrap_or_default(),
+    };
+    syscall!(setsockopt(
+        socket,
+        libc::SOL_SOCKET,
+        libc::SO_LINGER,
+        &val as *const libc::linger as *const libc::c_void,
+        size_of::<libc::linger>() as libc::socklen_t,
+    ))?;
+    Ok(())
+}
+
 pub fn accept(listener: &net::TcpListener) -> io::Result<(net::TcpStream, SocketAddr)> {
     let mut addr: MaybeUninit<libc::sockaddr_storage> = MaybeUninit::uninit();
     let mut length = size_of::<libc::sockaddr_storage>() as libc::socklen_t;

src/sys/windows/tcp.rs

@@ -1,5 +1,6 @@
 use std::io;
 use std::net::{self, SocketAddr};
+use std::time::Duration;
 use std::os::windows::io::FromRawSocket;
 use std::os::windows::raw::SOCKET as StdSocket; // winapi uses usize, stdlib uses u32/u64.
 
@@ -89,6 +90,29 @@ pub(crate) fn set_reuseaddr(socket: TcpSocket, reuseaddr: bool) -> io::Result<()
     }
 }
 
+pub(crate) fn set_linger(socket: TcpSocket, dur: Option<Duration>) -> io::Result<()> {
+    use winapi::ctypes::{c_char, c_int, c_ushort};
+    use winapi::um::winsock2::{linger, setsockopt, SOCKET_ERROR, SO_LINGER, SOL_SOCKET};
+    use std::mem::size_of;
+
+    let val: linger = linger {
+        l_onoff: if dur.is_some() { 1 } else { 0 },
+        l_linger: dur.map(|dur| dur.as_secs() as c_ushort).unwrap_or_default(),
+    };
+
+    match unsafe { setsockopt(
+        socket,
+        SOL_SOCKET,
+        SO_LINGER,
+        &val as *const _ as *const c_char,
+        size_of::<linger>() as c_int,
+    ) } {
+        0 => Ok(()),
+        SOCKET_ERROR => Err(io::Error::last_os_error()),
+        _ => panic!("unexpected return value"),
+    }
+}
+
 pub(crate) fn accept(listener: &net::TcpListener) -> io::Result<(net::TcpStream, SocketAddr)> {
     // The non-blocking state of `listener` is inherited. See
     // https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-accept#remarks.