net: add cygwin support (#7393)

Cargo.toml

@@ -30,4 +30,5 @@ unexpected_cfgs = { level = "warn", check-cfg = [
   'cfg(tokio_taskdump)',
   'cfg(tokio_unstable)',
   'cfg(tokio_uring)',
+  'cfg(target_os, values("cygwin"))',
 ] }

tokio/src/net/tcp/socket.rs

@@ -276,10 +276,20 @@ impl TcpSocket {
     ///     Ok(())
     /// }
     /// ```
-    #[cfg(all(unix, not(target_os = "solaris"), not(target_os = "illumos")))]
+    #[cfg(all(
+        unix,
+        not(target_os = "solaris"),
+        not(target_os = "illumos"),
+        not(target_os = "cygwin"),
+    ))]
     #[cfg_attr(
         docsrs,
-        doc(cfg(all(unix, not(target_os = "solaris"), not(target_os = "illumos"))))
+        doc(cfg(all(
+            unix,
+            not(target_os = "solaris"),
+            not(target_os = "illumos"),
+            not(target_os = "cygwin"),
+        )))
     )]
     pub fn set_reuseport(&self, reuseport: bool) -> io::Result<()> {
         self.inner.set_reuse_port(reuseport)
@@ -311,10 +321,20 @@ impl TcpSocket {
     ///     Ok(())
     /// }
     /// ```
-    #[cfg(all(unix, not(target_os = "solaris"), not(target_os = "illumos")))]
+    #[cfg(all(
+        unix,
+        not(target_os = "solaris"),
+        not(target_os = "illumos"),
+        not(target_os = "cygwin"),
+    ))]
     #[cfg_attr(
         docsrs,
-        doc(cfg(all(unix, not(target_os = "solaris"), not(target_os = "illumos"))))
+        doc(cfg(all(
+            unix,
+            not(target_os = "solaris"),
+            not(target_os = "illumos"),
+            not(target_os = "cygwin"),
+        )))
     )]
     pub fn reuseport(&self) -> io::Result<bool> {
         self.inner.reuse_port()

tokio/src/net/unix/ucred.rs

@@ -36,7 +36,8 @@ impl UCred {
     target_os = "redox",
     target_os = "android",
     target_os = "openbsd",
-    target_os = "haiku"
+    target_os = "haiku",
+    target_os = "cygwin"
 ))]
 pub(crate) use self::impl_linux::get_peer_cred;
 
@@ -69,7 +70,8 @@ pub(crate) use self::impl_noproc::get_peer_cred;
     target_os = "redox",
     target_os = "android",
     target_os = "openbsd",
-    target_os = "haiku"
+    target_os = "haiku",
+    target_os = "cygwin"
 ))]
 pub(crate) mod impl_linux {
     use crate::net::unix::{self, UnixStream};
@@ -83,7 +85,8 @@ pub(crate) mod impl_linux {
         target_os = "linux",
         target_os = "redox",
         target_os = "android",
-        target_os = "haiku"
+        target_os = "haiku",
+        target_os = "cygwin"
     ))]
     use libc::ucred;