library/std/src/sys/unix/net.rs - toolchain/rustc - Git at Google

 use crate::cmp;
 use crate::ffi::CStr;
 use crate::io::{self, IoSlice, IoSliceMut};
 use crate::mem;
 use crate::net::{Shutdown, SocketAddr};
 use crate::str;
 use crate::sys::fd::FileDesc;
 use crate::sys_common::net::{getsockopt, setsockopt, sockaddr_to_addr};
 use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::{Duration, Instant};

 use libc::{c_int, c_void, size_t, sockaddr, socklen_t, EAI_SYSTEM, MSG_PEEK};

 pub use crate::sys::{cvt, cvt_r};

 #[allow(unused_extern_crates)]
 pub extern crate libc as netc;

 pub type wrlen_t = size_t;

 pub struct Socket(FileDesc);

 pub fn init() {}

 pub fn cvt_gai(err: c_int) -> io::Result<()> {
     if err == 0 {
         return Ok(());
     }

     // We may need to trigger a glibc workaround. See on_resolver_failure() for details.
     on_resolver_failure();

     if err == EAI_SYSTEM {
         return Err(io::Error::last_os_error());
     }

     let detail = unsafe {
         str::from_utf8(CStr::from_ptr(libc::gai_strerror(err)).to_bytes()).unwrap().to_owned()
     };
     Err(io::Error::new(
         io::ErrorKind::Other,
         &format!("failed to lookup address information: {}", detail)[..],
     ))
 }

 impl Socket {
     pub fn new(addr: &SocketAddr, ty: c_int) -> io::Result<Socket> {
         let fam = match *addr {
             SocketAddr::V4(..) => libc::AF_INET,
             SocketAddr::V6(..) => libc::AF_INET6,
         };
         Socket::new_raw(fam, ty)
     }

     pub fn new_raw(fam: c_int, ty: c_int) -> io::Result<Socket> {
         unsafe {
             cfg_if::cfg_if! {
                 if #[cfg(any(
                     target_os = "android",
                     target_os = "dragonfly",
                     target_os = "freebsd",
                     target_os = "illumos",
                     target_os = "linux",
                     target_os = "netbsd",
                     target_os = "opensbd",
                 ))] {
                     // On platforms that support it we pass the SOCK_CLOEXEC
                     // flag to atomically create the socket and set it as
                     // CLOEXEC. On Linux this was added in 2.6.27.
                     let fd = cvt(libc::socket(fam, ty | libc::SOCK_CLOEXEC, 0))?;
                     Ok(Socket(FileDesc::new(fd)))
                 } else {
                     let fd = cvt(libc::socket(fam, ty, 0))?;
                     let fd = FileDesc::new(fd);
                     fd.set_cloexec()?;
                     let socket = Socket(fd);

                     // macOS and iOS use `SO_NOSIGPIPE` as a `setsockopt`
                     // flag to disable `SIGPIPE` emission on socket.
                     #[cfg(target_vendor = "apple")]
                     setsockopt(&socket, libc::SOL_SOCKET, libc::SO_NOSIGPIPE, 1)?;

                     Ok(socket)
                 }
             }
         }
     }

     #[cfg(not(target_os = "vxworks"))]
     pub fn new_pair(fam: c_int, ty: c_int) -> io::Result<(Socket, Socket)> {
         unsafe {
             let mut fds = [0, 0];

             cfg_if::cfg_if! {
                 if #[cfg(any(
                     target_os = "android",
                     target_os = "dragonfly",
                     target_os = "freebsd",
                     target_os = "illumos",
                     target_os = "linux",
                     target_os = "netbsd",
                     target_os = "opensbd",
                 ))] {
                     // Like above, set cloexec atomically
                     cvt(libc::socketpair(fam, ty | libc::SOCK_CLOEXEC, 0, fds.as_mut_ptr()))?;
                     Ok((Socket(FileDesc::new(fds[0])), Socket(FileDesc::new(fds[1]))))
                 } else {
                     cvt(libc::socketpair(fam, ty, 0, fds.as_mut_ptr()))?;
                     let a = FileDesc::new(fds[0]);
                     let b = FileDesc::new(fds[1]);
                     a.set_cloexec()?;
                     b.set_cloexec()?;
                     Ok((Socket(a), Socket(b)))
                 }
             }
         }
     }

     #[cfg(target_os = "vxworks")]
     pub fn new_pair(_fam: c_int, _ty: c_int) -> io::Result<(Socket, Socket)> {
         unimplemented!()
     }

     pub fn connect_timeout(&self, addr: &SocketAddr, timeout: Duration) -> io::Result<()> {
         self.set_nonblocking(true)?;
         let r = unsafe {
             let (addrp, len) = addr.into_inner();
             cvt(libc::connect(self.0.raw(), addrp, len))
         };
         self.set_nonblocking(false)?;

         match r {
             Ok(_) => return Ok(()),
             // there's no ErrorKind for EINPROGRESS :(
             Err(ref e) if e.raw_os_error() == Some(libc::EINPROGRESS) => {}
             Err(e) => return Err(e),
         }

         let mut pollfd = libc::pollfd { fd: self.0.raw(), events: libc::POLLOUT, revents: 0 };

         if timeout.as_secs() == 0 && timeout.subsec_nanos() == 0 {
             return Err(io::Error::new_const(
                 io::ErrorKind::InvalidInput,
                 &"cannot set a 0 duration timeout",
             ));
         }

         let start = Instant::now();

         loop {
             let elapsed = start.elapsed();
             if elapsed >= timeout {
                 return Err(io::Error::new_const(io::ErrorKind::TimedOut, &"connection timed out"));
             }

             let timeout = timeout - elapsed;
             let mut timeout = timeout
                 .as_secs()
                 .saturating_mul(1_000)
                 .saturating_add(timeout.subsec_nanos() as u64 / 1_000_000);
             if timeout == 0 {
                 timeout = 1;
             }

             let timeout = cmp::min(timeout, c_int::MAX as u64) as c_int;

             match unsafe { libc::poll(&mut pollfd, 1, timeout) } {
                 -1 => {
                     let err = io::Error::last_os_error();
                     if err.kind() != io::ErrorKind::Interrupted {
                         return Err(err);
                     }
                 }
                 0 => {}
                 _ => {
                     // linux returns POLLOUT|POLLERR|POLLHUP for refused connections (!), so look
                     // for POLLHUP rather than read readiness
                     if pollfd.revents & libc::POLLHUP != 0 {
                         let e = self.take_error()?.unwrap_or_else(|| {
                             io::Error::new_const(
                                 io::ErrorKind::Other,
                                 &"no error set after POLLHUP",
                             )
                         });
                         return Err(e);
                     }

                     return Ok(());
                 }
             }
         }
     }

     pub fn accept(&self, storage: *mut sockaddr, len: *mut socklen_t) -> io::Result<Socket> {
         // Unfortunately the only known way right now to accept a socket and
         // atomically set the CLOEXEC flag is to use the `accept4` syscall on
         // platforms that support it. On Linux, this was added in 2.6.28,
         // glibc 2.10 and musl 0.9.5.
         cfg_if::cfg_if! {
             if #[cfg(any(
                 target_os = "android",
                 target_os = "dragonfly",
                 target_os = "freebsd",
                 target_os = "illumos",
                 target_os = "linux",
                 target_os = "netbsd",
                 target_os = "opensbd",
             ))] {
                 let fd = cvt_r(|| unsafe {
                     libc::accept4(self.0.raw(), storage, len, libc::SOCK_CLOEXEC)
                 })?;
                 Ok(Socket(FileDesc::new(fd)))
             } else {
                 let fd = cvt_r(|| unsafe { libc::accept(self.0.raw(), storage, len) })?;
                 let fd = FileDesc::new(fd);
                 fd.set_cloexec()?;
                 Ok(Socket(fd))
             }
         }
     }

     pub fn duplicate(&self) -> io::Result<Socket> {
         self.0.duplicate().map(Socket)
     }

     fn recv_with_flags(&self, buf: &mut [u8], flags: c_int) -> io::Result<usize> {
         let ret = cvt(unsafe {
             libc::recv(self.0.raw(), buf.as_mut_ptr() as *mut c_void, buf.len(), flags)
         })?;
         Ok(ret as usize)
     }

     pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
         self.recv_with_flags(buf, 0)
     }

     pub fn peek(&self, buf: &mut [u8]) -> io::Result<usize> {
         self.recv_with_flags(buf, MSG_PEEK)
     }

     pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
         self.0.read_vectored(bufs)
     }

     #[inline]
     pub fn is_read_vectored(&self) -> bool {
         self.0.is_read_vectored()
     }

     fn recv_from_with_flags(
         &self,
         buf: &mut [u8],
         flags: c_int,
     ) -> io::Result<(usize, SocketAddr)> {
         let mut storage: libc::sockaddr_storage = unsafe { mem::zeroed() };
         let mut addrlen = mem::size_of_val(&storage) as libc::socklen_t;

         let n = cvt(unsafe {
             libc::recvfrom(
                 self.0.raw(),
                 buf.as_mut_ptr() as *mut c_void,
                 buf.len(),
                 flags,
                 &mut storage as *mut _ as *mut _,
                 &mut addrlen,
             )
         })?;
         Ok((n as usize, sockaddr_to_addr(&storage, addrlen as usize)?))
     }

     pub fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
         self.recv_from_with_flags(buf, 0)
     }

     #[cfg(any(
         target_os = "android",
         target_os = "dragonfly",
         target_os = "emscripten",
         target_os = "freebsd",
         target_os = "linux",
         target_os = "netbsd",
         target_os = "openbsd",
     ))]
     pub fn recv_msg(&self, msg: &mut libc::msghdr) -> io::Result<usize> {
         let n = cvt(unsafe { libc::recvmsg(self.0.raw(), msg, libc::MSG_CMSG_CLOEXEC) })?;
         Ok(n as usize)
     }

     pub fn peek_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
         self.recv_from_with_flags(buf, MSG_PEEK)
     }

     pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
         self.0.write(buf)
     }

     pub fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
         self.0.write_vectored(bufs)
     }

     #[inline]
     pub fn is_write_vectored(&self) -> bool {
         self.0.is_write_vectored()
     }

     #[cfg(any(
         target_os = "android",
         target_os = "dragonfly",
         target_os = "emscripten",
         target_os = "freebsd",
         target_os = "linux",
         target_os = "netbsd",
         target_os = "openbsd",
     ))]
     pub fn send_msg(&self, msg: &mut libc::msghdr) -> io::Result<usize> {
         let n = cvt(unsafe { libc::sendmsg(self.0.raw(), msg, 0) })?;
         Ok(n as usize)
     }

     pub fn set_timeout(&self, dur: Option<Duration>, kind: libc::c_int) -> io::Result<()> {
         let timeout = match dur {
             Some(dur) => {
                 if dur.as_secs() == 0 && dur.subsec_nanos() == 0 {
                     return Err(io::Error::new_const(
                         io::ErrorKind::InvalidInput,
                         &"cannot set a 0 duration timeout",
                     ));
                 }

                 let secs = if dur.as_secs() > libc::time_t::MAX as u64 {
                     libc::time_t::MAX
                 } else {
                     dur.as_secs() as libc::time_t
                 };
                 let mut timeout = libc::timeval {
                     tv_sec: secs,
                     tv_usec: dur.subsec_micros() as libc::suseconds_t,
                 };
                 if timeout.tv_sec == 0 && timeout.tv_usec == 0 {
                     timeout.tv_usec = 1;
                 }
                 timeout
             }
             None => libc::timeval { tv_sec: 0, tv_usec: 0 },
         };
         setsockopt(self, libc::SOL_SOCKET, kind, timeout)
     }

     pub fn timeout(&self, kind: libc::c_int) -> io::Result<Option<Duration>> {
         let raw: libc::timeval = getsockopt(self, libc::SOL_SOCKET, kind)?;
         if raw.tv_sec == 0 && raw.tv_usec == 0 {
             Ok(None)
         } else {
             let sec = raw.tv_sec as u64;
             let nsec = (raw.tv_usec as u32) * 1000;
             Ok(Some(Duration::new(sec, nsec)))
         }
     }

     pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
         let how = match how {
             Shutdown::Write => libc::SHUT_WR,
             Shutdown::Read => libc::SHUT_RD,
             Shutdown::Both => libc::SHUT_RDWR,
         };
         cvt(unsafe { libc::shutdown(self.0.raw(), how) })?;
         Ok(())
     }

     pub fn set_nodelay(&self, nodelay: bool) -> io::Result<()> {
         setsockopt(self, libc::IPPROTO_TCP, libc::TCP_NODELAY, nodelay as c_int)
     }

     pub fn nodelay(&self) -> io::Result<bool> {
         let raw: c_int = getsockopt(self, libc::IPPROTO_TCP, libc::TCP_NODELAY)?;
         Ok(raw != 0)
     }

     #[cfg(any(target_os = "android", target_os = "linux",))]
     pub fn set_passcred(&self, passcred: bool) -> io::Result<()> {
         setsockopt(self, libc::SOL_SOCKET, libc::SO_PASSCRED, passcred as libc::c_int)
     }

     #[cfg(any(target_os = "android", target_os = "linux",))]
     pub fn passcred(&self) -> io::Result<bool> {
         let passcred: libc::c_int = getsockopt(self, libc::SOL_SOCKET, libc::SO_PASSCRED)?;
         Ok(passcred != 0)
     }

     #[cfg(not(any(target_os = "solaris", target_os = "illumos")))]
     pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
         let mut nonblocking = nonblocking as libc::c_int;
         cvt(unsafe { libc::ioctl(*self.as_inner(), libc::FIONBIO, &mut nonblocking) }).map(drop)
     }

     #[cfg(any(target_os = "solaris", target_os = "illumos"))]
     pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
         // FIONBIO is inadequate for sockets on illumos/Solaris, so use the
         // fcntl(F_[GS]ETFL)-based method provided by FileDesc instead.
         self.0.set_nonblocking(nonblocking)
     }

     pub fn take_error(&self) -> io::Result<Option<io::Error>> {
         let raw: c_int = getsockopt(self, libc::SOL_SOCKET, libc::SO_ERROR)?;
         if raw == 0 { Ok(None) } else { Ok(Some(io::Error::from_raw_os_error(raw as i32))) }
     }
 }

 impl AsInner<c_int> for Socket {
     fn as_inner(&self) -> &c_int {
         self.0.as_inner()
     }
 }

 impl FromInner<c_int> for Socket {
     fn from_inner(fd: c_int) -> Socket {
         Socket(FileDesc::new(fd))
     }
 }

 impl IntoInner<c_int> for Socket {
     fn into_inner(self) -> c_int {
         self.0.into_raw()
     }
 }

 // In versions of glibc prior to 2.26, there's a bug where the DNS resolver
 // will cache the contents of /etc/resolv.conf, so changes to that file on disk
 // can be ignored by a long-running program. That can break DNS lookups on e.g.
 // laptops where the network comes and goes. See
 // https://sourceware.org/bugzilla/show_bug.cgi?id=984. Note however that some
 // distros including Debian have patched glibc to fix this for a long time.
 //
 // A workaround for this bug is to call the res_init libc function, to clear
 // the cached configs. Unfortunately, while we believe glibc's implementation
 // of res_init is thread-safe, we know that other implementations are not
 // (https://github.com/rust-lang/rust/issues/43592). Code here in libstd could
 // try to synchronize its res_init calls with a Mutex, but that wouldn't
 // protect programs that call into libc in other ways. So instead of calling
 // res_init unconditionally, we call it only when we detect we're linking
 // against glibc version < 2.26. (That is, when we both know its needed and
 // believe it's thread-safe).
 #[cfg(all(target_env = "gnu", not(target_os = "vxworks")))]
 fn on_resolver_failure() {
     use crate::sys;

     // If the version fails to parse, we treat it the same as "not glibc".
     if let Some(version) = sys::os::glibc_version() {
         if version < (2, 26) {
             unsafe { libc::res_init() };
         }
     }
 }

 #[cfg(any(not(target_env = "gnu"), target_os = "vxworks"))]
 fn on_resolver_failure() {}
	use crate::cmp;
	use crate::ffi::CStr;
	use crate::io::{self, IoSlice, IoSliceMut};
	use crate::mem;
	use crate::net::{Shutdown, SocketAddr};
	use crate::str;
	use crate::sys::fd::FileDesc;
	use crate::sys_common::net::{getsockopt, setsockopt, sockaddr_to_addr};
	use crate::sys_common::{AsInner, FromInner, IntoInner};
	use crate::time::{Duration, Instant};

	use libc::{c_int, c_void, size_t, sockaddr, socklen_t, EAI_SYSTEM, MSG_PEEK};

	pub use crate::sys::{cvt, cvt_r};

	#[allow(unused_extern_crates)]
	pub extern crate libc as netc;

	pub type wrlen_t = size_t;

	pub struct Socket(FileDesc);

	pub fn init() {}

	pub fn cvt_gai(err: c_int) -> io::Result<()> {
	if err == 0 {
	return Ok(());
	}

	// We may need to trigger a glibc workaround. See on_resolver_failure() for details.
	on_resolver_failure();

	if err == EAI_SYSTEM {
	return Err(io::Error::last_os_error());
	}

	let detail = unsafe {
	str::from_utf8(CStr::from_ptr(libc::gai_strerror(err)).to_bytes()).unwrap().to_owned()
	};
	Err(io::Error::new(
	io::ErrorKind::Other,
	&format!("failed to lookup address information: {}", detail)[..],
	))
	}

	impl Socket {
	pub fn new(addr: &SocketAddr, ty: c_int) -> io::Result<Socket> {
	let fam = match *addr {
	SocketAddr::V4(..) => libc::AF_INET,
	SocketAddr::V6(..) => libc::AF_INET6,
	};
	Socket::new_raw(fam, ty)
	}

	pub fn new_raw(fam: c_int, ty: c_int) -> io::Result<Socket> {
	unsafe {
	cfg_if::cfg_if! {
	if #[cfg(any(
	target_os = "android",
	target_os = "dragonfly",
	target_os = "freebsd",
	target_os = "illumos",
	target_os = "linux",
	target_os = "netbsd",
	target_os = "opensbd",
	))] {
	// On platforms that support it we pass the SOCK_CLOEXEC
	// flag to atomically create the socket and set it as
	// CLOEXEC. On Linux this was added in 2.6.27.
	let fd = cvt(libc::socket(fam, ty \| libc::SOCK_CLOEXEC, 0))?;
	Ok(Socket(FileDesc::new(fd)))
	} else {
	let fd = cvt(libc::socket(fam, ty, 0))?;
	let fd = FileDesc::new(fd);
	fd.set_cloexec()?;
	let socket = Socket(fd);

	// macOS and iOS use `SO_NOSIGPIPE` as a `setsockopt`
	// flag to disable `SIGPIPE` emission on socket.
	#[cfg(target_vendor = "apple")]
	setsockopt(&socket, libc::SOL_SOCKET, libc::SO_NOSIGPIPE, 1)?;

	Ok(socket)
	}
	}
	}
	}

	#[cfg(not(target_os = "vxworks"))]
	pub fn new_pair(fam: c_int, ty: c_int) -> io::Result<(Socket, Socket)> {
	unsafe {
	let mut fds = [0, 0];

	cfg_if::cfg_if! {
	if #[cfg(any(
	target_os = "android",
	target_os = "dragonfly",
	target_os = "freebsd",
	target_os = "illumos",
	target_os = "linux",
	target_os = "netbsd",
	target_os = "opensbd",
	))] {
	// Like above, set cloexec atomically
	cvt(libc::socketpair(fam, ty \| libc::SOCK_CLOEXEC, 0, fds.as_mut_ptr()))?;
	Ok((Socket(FileDesc::new(fds[0])), Socket(FileDesc::new(fds[1]))))
	} else {
	cvt(libc::socketpair(fam, ty, 0, fds.as_mut_ptr()))?;
	let a = FileDesc::new(fds[0]);
	let b = FileDesc::new(fds[1]);
	a.set_cloexec()?;
	b.set_cloexec()?;
	Ok((Socket(a), Socket(b)))
	}
	}
	}
	}

	#[cfg(target_os = "vxworks")]
	pub fn new_pair(_fam: c_int, _ty: c_int) -> io::Result<(Socket, Socket)> {
	unimplemented!()
	}

	pub fn connect_timeout(&self, addr: &SocketAddr, timeout: Duration) -> io::Result<()> {
	self.set_nonblocking(true)?;
	let r = unsafe {
	let (addrp, len) = addr.into_inner();
	cvt(libc::connect(self.0.raw(), addrp, len))
	};
	self.set_nonblocking(false)?;

	match r {
	Ok(_) => return Ok(()),
	// there's no ErrorKind for EINPROGRESS :(
	Err(ref e) if e.raw_os_error() == Some(libc::EINPROGRESS) => {}
	Err(e) => return Err(e),
	}

	let mut pollfd = libc::pollfd { fd: self.0.raw(), events: libc::POLLOUT, revents: 0 };

	if timeout.as_secs() == 0 && timeout.subsec_nanos() == 0 {
	return Err(io::Error::new_const(
	io::ErrorKind::InvalidInput,
	&"cannot set a 0 duration timeout",
	));
	}

	let start = Instant::now();

	loop {
	let elapsed = start.elapsed();
	if elapsed >= timeout {
	return Err(io::Error::new_const(io::ErrorKind::TimedOut, &"connection timed out"));
	}

	let timeout = timeout - elapsed;
	let mut timeout = timeout
	.as_secs()
	.saturating_mul(1_000)
	.saturating_add(timeout.subsec_nanos() as u64 / 1_000_000);
	if timeout == 0 {
	timeout = 1;
	}

	let timeout = cmp::min(timeout, c_int::MAX as u64) as c_int;

	match unsafe { libc::poll(&mut pollfd, 1, timeout) } {
	-1 => {
	let err = io::Error::last_os_error();
	if err.kind() != io::ErrorKind::Interrupted {
	return Err(err);
	}
	}
	0 => {}
	_ => {
	// linux returns POLLOUT\|POLLERR\|POLLHUP for refused connections (!), so look
	// for POLLHUP rather than read readiness
	if pollfd.revents & libc::POLLHUP != 0 {
	let e = self.take_error()?.unwrap_or_else(\|\| {
	io::Error::new_const(
	io::ErrorKind::Other,
	&"no error set after POLLHUP",
	)
	});
	return Err(e);
	}

	return Ok(());
	}
	}
	}
	}

	pub fn accept(&self, storage: mut sockaddr, len: mut socklen_t) -> io::Result<Socket> {
	// Unfortunately the only known way right now to accept a socket and
	// atomically set the CLOEXEC flag is to use the `accept4` syscall on
	// platforms that support it. On Linux, this was added in 2.6.28,
	// glibc 2.10 and musl 0.9.5.
	cfg_if::cfg_if! {
	if #[cfg(any(
	target_os = "android",
	target_os = "dragonfly",
	target_os = "freebsd",
	target_os = "illumos",
	target_os = "linux",
	target_os = "netbsd",
	target_os = "opensbd",
	))] {
	let fd = cvt_r(\|\| unsafe {
	libc::accept4(self.0.raw(), storage, len, libc::SOCK_CLOEXEC)
	})?;
	Ok(Socket(FileDesc::new(fd)))
	} else {
	let fd = cvt_r(\|\| unsafe { libc::accept(self.0.raw(), storage, len) })?;
	let fd = FileDesc::new(fd);
	fd.set_cloexec()?;
	Ok(Socket(fd))
	}
	}
	}

	pub fn duplicate(&self) -> io::Result<Socket> {
	self.0.duplicate().map(Socket)
	}

	fn recv_with_flags(&self, buf: &mut [u8], flags: c_int) -> io::Result<usize> {
	let ret = cvt(unsafe {
	libc::recv(self.0.raw(), buf.as_mut_ptr() as *mut c_void, buf.len(), flags)
	})?;
	Ok(ret as usize)
	}

	pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
	self.recv_with_flags(buf, 0)
	}

	pub fn peek(&self, buf: &mut [u8]) -> io::Result<usize> {
	self.recv_with_flags(buf, MSG_PEEK)
	}

	pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
	self.0.read_vectored(bufs)
	}

	#[inline]
	pub fn is_read_vectored(&self) -> bool {
	self.0.is_read_vectored()
	}

	fn recv_from_with_flags(
	&self,
	buf: &mut [u8],
	flags: c_int,
	) -> io::Result<(usize, SocketAddr)> {
	let mut storage: libc::sockaddr_storage = unsafe { mem::zeroed() };
	let mut addrlen = mem::size_of_val(&storage) as libc::socklen_t;

	let n = cvt(unsafe {
	libc::recvfrom(
	self.0.raw(),
	buf.as_mut_ptr() as *mut c_void,
	buf.len(),
	flags,
	&mut storage as mut _ as mut _,
	&mut addrlen,
	)
	})?;
	Ok((n as usize, sockaddr_to_addr(&storage, addrlen as usize)?))
	}

	pub fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
	self.recv_from_with_flags(buf, 0)
	}

	#[cfg(any(
	target_os = "android",
	target_os = "dragonfly",
	target_os = "emscripten",
	target_os = "freebsd",
	target_os = "linux",
	target_os = "netbsd",
	target_os = "openbsd",
	))]
	pub fn recv_msg(&self, msg: &mut libc::msghdr) -> io::Result<usize> {
	let n = cvt(unsafe { libc::recvmsg(self.0.raw(), msg, libc::MSG_CMSG_CLOEXEC) })?;
	Ok(n as usize)
	}

	pub fn peek_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
	self.recv_from_with_flags(buf, MSG_PEEK)
	}

	pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
	self.0.write(buf)
	}

	pub fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
	self.0.write_vectored(bufs)
	}

	#[inline]
	pub fn is_write_vectored(&self) -> bool {
	self.0.is_write_vectored()
	}

	#[cfg(any(
	target_os = "android",
	target_os = "dragonfly",
	target_os = "emscripten",
	target_os = "freebsd",
	target_os = "linux",
	target_os = "netbsd",
	target_os = "openbsd",
	))]
	pub fn send_msg(&self, msg: &mut libc::msghdr) -> io::Result<usize> {
	let n = cvt(unsafe { libc::sendmsg(self.0.raw(), msg, 0) })?;
	Ok(n as usize)
	}

	pub fn set_timeout(&self, dur: Option<Duration>, kind: libc::c_int) -> io::Result<()> {
	let timeout = match dur {
	Some(dur) => {
	if dur.as_secs() == 0 && dur.subsec_nanos() == 0 {
	return Err(io::Error::new_const(
	io::ErrorKind::InvalidInput,
	&"cannot set a 0 duration timeout",
	));
	}

	let secs = if dur.as_secs() > libc::time_t::MAX as u64 {
	libc::time_t::MAX
	} else {
	dur.as_secs() as libc::time_t
	};
	let mut timeout = libc::timeval {
	tv_sec: secs,
	tv_usec: dur.subsec_micros() as libc::suseconds_t,
	};
	if timeout.tv_sec == 0 && timeout.tv_usec == 0 {
	timeout.tv_usec = 1;
	}
	timeout
	}
	None => libc::timeval { tv_sec: 0, tv_usec: 0 },
	};
	setsockopt(self, libc::SOL_SOCKET, kind, timeout)
	}

	pub fn timeout(&self, kind: libc::c_int) -> io::Result<Option<Duration>> {
	let raw: libc::timeval = getsockopt(self, libc::SOL_SOCKET, kind)?;
	if raw.tv_sec == 0 && raw.tv_usec == 0 {
	Ok(None)
	} else {
	let sec = raw.tv_sec as u64;
	let nsec = (raw.tv_usec as u32) * 1000;
	Ok(Some(Duration::new(sec, nsec)))
	}
	}

	pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
	let how = match how {
	Shutdown::Write => libc::SHUT_WR,
	Shutdown::Read => libc::SHUT_RD,
	Shutdown::Both => libc::SHUT_RDWR,
	};
	cvt(unsafe { libc::shutdown(self.0.raw(), how) })?;
	Ok(())
	}

	pub fn set_nodelay(&self, nodelay: bool) -> io::Result<()> {
	setsockopt(self, libc::IPPROTO_TCP, libc::TCP_NODELAY, nodelay as c_int)
	}

	pub fn nodelay(&self) -> io::Result<bool> {
	let raw: c_int = getsockopt(self, libc::IPPROTO_TCP, libc::TCP_NODELAY)?;
	Ok(raw != 0)
	}

	#[cfg(any(target_os = "android", target_os = "linux",))]
	pub fn set_passcred(&self, passcred: bool) -> io::Result<()> {
	setsockopt(self, libc::SOL_SOCKET, libc::SO_PASSCRED, passcred as libc::c_int)
	}

	#[cfg(any(target_os = "android", target_os = "linux",))]
	pub fn passcred(&self) -> io::Result<bool> {
	let passcred: libc::c_int = getsockopt(self, libc::SOL_SOCKET, libc::SO_PASSCRED)?;
	Ok(passcred != 0)
	}

	#[cfg(not(any(target_os = "solaris", target_os = "illumos")))]
	pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
	let mut nonblocking = nonblocking as libc::c_int;
	cvt(unsafe { libc::ioctl(*self.as_inner(), libc::FIONBIO, &mut nonblocking) }).map(drop)
	}

	#[cfg(any(target_os = "solaris", target_os = "illumos"))]
	pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
	// FIONBIO is inadequate for sockets on illumos/Solaris, so use the
	// fcntl(F_[GS]ETFL)-based method provided by FileDesc instead.
	self.0.set_nonblocking(nonblocking)
	}

	pub fn take_error(&self) -> io::Result<Option<io::Error>> {
	let raw: c_int = getsockopt(self, libc::SOL_SOCKET, libc::SO_ERROR)?;
	if raw == 0 { Ok(None) } else { Ok(Some(io::Error::from_raw_os_error(raw as i32))) }
	}
	}

	impl AsInner<c_int> for Socket {
	fn as_inner(&self) -> &c_int {
	self.0.as_inner()
	}
	}

	impl FromInner<c_int> for Socket {
	fn from_inner(fd: c_int) -> Socket {
	Socket(FileDesc::new(fd))
	}
	}

	impl IntoInner<c_int> for Socket {
	fn into_inner(self) -> c_int {
	self.0.into_raw()
	}
	}

	// In versions of glibc prior to 2.26, there's a bug where the DNS resolver
	// will cache the contents of /etc/resolv.conf, so changes to that file on disk
	// can be ignored by a long-running program. That can break DNS lookups on e.g.
	// laptops where the network comes and goes. See
	// https://sourceware.org/bugzilla/show_bug.cgi?id=984. Note however that some
	// distros including Debian have patched glibc to fix this for a long time.
	//
	// A workaround for this bug is to call the res_init libc function, to clear
	// the cached configs. Unfortunately, while we believe glibc's implementation
	// of res_init is thread-safe, we know that other implementations are not
	// (https://github.com/rust-lang/rust/issues/43592). Code here in libstd could
	// try to synchronize its res_init calls with a Mutex, but that wouldn't
	// protect programs that call into libc in other ways. So instead of calling
	// res_init unconditionally, we call it only when we detect we're linking
	// against glibc version < 2.26. (That is, when we both know its needed and
	// believe it's thread-safe).
	#[cfg(all(target_env = "gnu", not(target_os = "vxworks")))]
	fn on_resolver_failure() {
	use crate::sys;

	// If the version fails to parse, we treat it the same as "not glibc".
	if let Some(version) = sys::os::glibc_version() {
	if version < (2, 26) {
	unsafe { libc::res_init() };
	}
	}
	}

	#[cfg(any(not(target_env = "gnu"), target_os = "vxworks"))]
	fn on_resolver_failure() {}