std/sys/net/connection/socket/
unix.rs

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1use libc::{MSG_PEEK, c_int, c_void, size_t, sockaddr, socklen_t};
2
3use crate::ffi::CStr;
4use crate::io::{self, BorrowedBuf, BorrowedCursor, IoSlice, IoSliceMut};
5use crate::net::{Shutdown, SocketAddr};
6use crate::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, RawFd};
7use crate::sys::fd::FileDesc;
8use crate::sys::net::{getsockopt, setsockopt};
9use crate::sys::pal::IsMinusOne;
10use crate::sys_common::{AsInner, FromInner, IntoInner};
11use crate::time::{Duration, Instant};
12use crate::{cmp, mem};
13
14cfg_if::cfg_if! {
15    if #[cfg(target_vendor = "apple")] {
16        use libc::SO_LINGER_SEC as SO_LINGER;
17    } else {
18        use libc::SO_LINGER;
19    }
20}
21
22pub(super) use libc as netc;
23
24use super::{socket_addr_from_c, socket_addr_to_c};
25pub use crate::sys::{cvt, cvt_r};
26
27#[expect(non_camel_case_types)]
28pub type wrlen_t = size_t;
29
30pub struct Socket(FileDesc);
31
32pub fn init() {}
33
34pub fn cvt_gai(err: c_int) -> io::Result<()> {
35    if err == 0 {
36        return Ok(());
37    }
38
39    // We may need to trigger a glibc workaround. See on_resolver_failure() for details.
40    on_resolver_failure();
41
42    #[cfg(not(any(target_os = "espidf", target_os = "nuttx")))]
43    if err == libc::EAI_SYSTEM {
44        return Err(io::Error::last_os_error());
45    }
46
47    #[cfg(not(any(target_os = "espidf", target_os = "nuttx")))]
48    let detail = unsafe {
49        // We can't always expect a UTF-8 environment. When we don't get that luxury,
50        // it's better to give a low-quality error message than none at all.
51        CStr::from_ptr(libc::gai_strerror(err)).to_string_lossy()
52    };
53
54    #[cfg(any(target_os = "espidf", target_os = "nuttx"))]
55    let detail = "";
56
57    Err(io::Error::new(
58        io::ErrorKind::Uncategorized,
59        &format!("failed to lookup address information: {detail}")[..],
60    ))
61}
62
63impl Socket {
64    pub fn new(addr: &SocketAddr, ty: c_int) -> io::Result<Socket> {
65        let fam = match *addr {
66            SocketAddr::V4(..) => libc::AF_INET,
67            SocketAddr::V6(..) => libc::AF_INET6,
68        };
69        Socket::new_raw(fam, ty)
70    }
71
72    pub fn new_raw(fam: c_int, ty: c_int) -> io::Result<Socket> {
73        unsafe {
74            cfg_if::cfg_if! {
75                if #[cfg(any(
76                    target_os = "android",
77                    target_os = "dragonfly",
78                    target_os = "freebsd",
79                    target_os = "illumos",
80                    target_os = "hurd",
81                    target_os = "linux",
82                    target_os = "netbsd",
83                    target_os = "openbsd",
84                    target_os = "nto",
85                    target_os = "solaris",
86                ))] {
87                    // On platforms that support it we pass the SOCK_CLOEXEC
88                    // flag to atomically create the socket and set it as
89                    // CLOEXEC. On Linux this was added in 2.6.27.
90                    let fd = cvt(libc::socket(fam, ty | libc::SOCK_CLOEXEC, 0))?;
91                    let socket = Socket(FileDesc::from_raw_fd(fd));
92
93                    // DragonFlyBSD, FreeBSD and NetBSD use `SO_NOSIGPIPE` as a `setsockopt`
94                    // flag to disable `SIGPIPE` emission on socket.
95                    #[cfg(any(target_os = "freebsd", target_os = "netbsd", target_os = "dragonfly"))]
96                    setsockopt(&socket, libc::SOL_SOCKET, libc::SO_NOSIGPIPE, 1)?;
97
98                    Ok(socket)
99                } else {
100                    let fd = cvt(libc::socket(fam, ty, 0))?;
101                    let fd = FileDesc::from_raw_fd(fd);
102                    fd.set_cloexec()?;
103                    let socket = Socket(fd);
104
105                    // macOS and iOS use `SO_NOSIGPIPE` as a `setsockopt`
106                    // flag to disable `SIGPIPE` emission on socket.
107                    #[cfg(target_vendor = "apple")]
108                    setsockopt(&socket, libc::SOL_SOCKET, libc::SO_NOSIGPIPE, 1)?;
109
110                    Ok(socket)
111                }
112            }
113        }
114    }
115
116    #[cfg(not(target_os = "vxworks"))]
117    pub fn new_pair(fam: c_int, ty: c_int) -> io::Result<(Socket, Socket)> {
118        unsafe {
119            let mut fds = [0, 0];
120
121            cfg_if::cfg_if! {
122                if #[cfg(any(
123                    target_os = "android",
124                    target_os = "dragonfly",
125                    target_os = "freebsd",
126                    target_os = "illumos",
127                    target_os = "linux",
128                    target_os = "hurd",
129                    target_os = "netbsd",
130                    target_os = "openbsd",
131                    target_os = "nto",
132                ))] {
133                    // Like above, set cloexec atomically
134                    cvt(libc::socketpair(fam, ty | libc::SOCK_CLOEXEC, 0, fds.as_mut_ptr()))?;
135                    Ok((Socket(FileDesc::from_raw_fd(fds[0])), Socket(FileDesc::from_raw_fd(fds[1]))))
136                } else {
137                    cvt(libc::socketpair(fam, ty, 0, fds.as_mut_ptr()))?;
138                    let a = FileDesc::from_raw_fd(fds[0]);
139                    let b = FileDesc::from_raw_fd(fds[1]);
140                    a.set_cloexec()?;
141                    b.set_cloexec()?;
142                    Ok((Socket(a), Socket(b)))
143                }
144            }
145        }
146    }
147
148    #[cfg(target_os = "vxworks")]
149    pub fn new_pair(_fam: c_int, _ty: c_int) -> io::Result<(Socket, Socket)> {
150        unimplemented!()
151    }
152
153    pub fn connect(&self, addr: &SocketAddr) -> io::Result<()> {
154        let (addr, len) = socket_addr_to_c(addr);
155        loop {
156            let result = unsafe { libc::connect(self.as_raw_fd(), addr.as_ptr(), len) };
157            if result.is_minus_one() {
158                let err = crate::sys::os::errno();
159                match err {
160                    libc::EINTR => continue,
161                    libc::EISCONN => return Ok(()),
162                    _ => return Err(io::Error::from_raw_os_error(err)),
163                }
164            }
165            return Ok(());
166        }
167    }
168
169    pub fn connect_timeout(&self, addr: &SocketAddr, timeout: Duration) -> io::Result<()> {
170        self.set_nonblocking(true)?;
171        let r = unsafe {
172            let (addr, len) = socket_addr_to_c(addr);
173            cvt(libc::connect(self.as_raw_fd(), addr.as_ptr(), len))
174        };
175        self.set_nonblocking(false)?;
176
177        match r {
178            Ok(_) => return Ok(()),
179            // there's no ErrorKind for EINPROGRESS :(
180            Err(ref e) if e.raw_os_error() == Some(libc::EINPROGRESS) => {}
181            Err(e) => return Err(e),
182        }
183
184        let mut pollfd = libc::pollfd { fd: self.as_raw_fd(), events: libc::POLLOUT, revents: 0 };
185
186        if timeout.as_secs() == 0 && timeout.subsec_nanos() == 0 {
187            return Err(io::Error::ZERO_TIMEOUT);
188        }
189
190        let start = Instant::now();
191
192        loop {
193            let elapsed = start.elapsed();
194            if elapsed >= timeout {
195                return Err(io::const_error!(io::ErrorKind::TimedOut, "connection timed out"));
196            }
197
198            let timeout = timeout - elapsed;
199            let mut timeout = timeout
200                .as_secs()
201                .saturating_mul(1_000)
202                .saturating_add(timeout.subsec_nanos() as u64 / 1_000_000);
203            if timeout == 0 {
204                timeout = 1;
205            }
206
207            let timeout = cmp::min(timeout, c_int::MAX as u64) as c_int;
208
209            match unsafe { libc::poll(&mut pollfd, 1, timeout) } {
210                -1 => {
211                    let err = io::Error::last_os_error();
212                    if !err.is_interrupted() {
213                        return Err(err);
214                    }
215                }
216                0 => {}
217                _ => {
218                    if cfg!(target_os = "vxworks") {
219                        // VxWorks poll does not return  POLLHUP or POLLERR in revents. Check if the
220                        // connection actually succeeded and return ok only when the socket is
221                        // ready and no errors were found.
222                        if let Some(e) = self.take_error()? {
223                            return Err(e);
224                        }
225                    } else {
226                        // linux returns POLLOUT|POLLERR|POLLHUP for refused connections (!), so look
227                        // for POLLHUP or POLLERR rather than read readiness
228                        if pollfd.revents & (libc::POLLHUP | libc::POLLERR) != 0 {
229                            let e = self.take_error()?.unwrap_or_else(|| {
230                                io::const_error!(
231                                    io::ErrorKind::Uncategorized,
232                                    "no error set after POLLHUP",
233                                )
234                            });
235                            return Err(e);
236                        }
237                    }
238
239                    return Ok(());
240                }
241            }
242        }
243    }
244
245    pub fn accept(&self, storage: *mut sockaddr, len: *mut socklen_t) -> io::Result<Socket> {
246        // Unfortunately the only known way right now to accept a socket and
247        // atomically set the CLOEXEC flag is to use the `accept4` syscall on
248        // platforms that support it. On Linux, this was added in 2.6.28,
249        // glibc 2.10 and musl 0.9.5.
250        cfg_if::cfg_if! {
251            if #[cfg(any(
252                target_os = "android",
253                target_os = "dragonfly",
254                target_os = "freebsd",
255                target_os = "illumos",
256                target_os = "linux",
257                target_os = "hurd",
258                target_os = "netbsd",
259                target_os = "openbsd",
260            ))] {
261                unsafe {
262                    let fd = cvt_r(|| libc::accept4(self.as_raw_fd(), storage, len, libc::SOCK_CLOEXEC))?;
263                    Ok(Socket(FileDesc::from_raw_fd(fd)))
264                }
265            } else {
266                unsafe {
267                    let fd = cvt_r(|| libc::accept(self.as_raw_fd(), storage, len))?;
268                    let fd = FileDesc::from_raw_fd(fd);
269                    fd.set_cloexec()?;
270                    Ok(Socket(fd))
271                }
272            }
273        }
274    }
275
276    pub fn duplicate(&self) -> io::Result<Socket> {
277        self.0.duplicate().map(Socket)
278    }
279
280    fn recv_with_flags(&self, mut buf: BorrowedCursor<'_>, flags: c_int) -> io::Result<()> {
281        let ret = cvt(unsafe {
282            libc::recv(
283                self.as_raw_fd(),
284                buf.as_mut().as_mut_ptr() as *mut c_void,
285                buf.capacity(),
286                flags,
287            )
288        })?;
289        unsafe {
290            buf.advance_unchecked(ret as usize);
291        }
292        Ok(())
293    }
294
295    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
296        let mut buf = BorrowedBuf::from(buf);
297        self.recv_with_flags(buf.unfilled(), 0)?;
298        Ok(buf.len())
299    }
300
301    pub fn peek(&self, buf: &mut [u8]) -> io::Result<usize> {
302        let mut buf = BorrowedBuf::from(buf);
303        self.recv_with_flags(buf.unfilled(), MSG_PEEK)?;
304        Ok(buf.len())
305    }
306
307    pub fn read_buf(&self, buf: BorrowedCursor<'_>) -> io::Result<()> {
308        self.recv_with_flags(buf, 0)
309    }
310
311    pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
312        self.0.read_vectored(bufs)
313    }
314
315    #[inline]
316    pub fn is_read_vectored(&self) -> bool {
317        self.0.is_read_vectored()
318    }
319
320    fn recv_from_with_flags(
321        &self,
322        buf: &mut [u8],
323        flags: c_int,
324    ) -> io::Result<(usize, SocketAddr)> {
325        let mut storage: libc::sockaddr_storage = unsafe { mem::zeroed() };
326        let mut addrlen = mem::size_of_val(&storage) as libc::socklen_t;
327
328        let n = cvt(unsafe {
329            libc::recvfrom(
330                self.as_raw_fd(),
331                buf.as_mut_ptr() as *mut c_void,
332                buf.len(),
333                flags,
334                (&raw mut storage) as *mut _,
335                &mut addrlen,
336            )
337        })?;
338        Ok((n as usize, unsafe { socket_addr_from_c(&storage, addrlen as usize)? }))
339    }
340
341    pub fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
342        self.recv_from_with_flags(buf, 0)
343    }
344
345    #[cfg(any(target_os = "android", target_os = "linux"))]
346    pub fn recv_msg(&self, msg: &mut libc::msghdr) -> io::Result<usize> {
347        let n = cvt(unsafe { libc::recvmsg(self.as_raw_fd(), msg, libc::MSG_CMSG_CLOEXEC) })?;
348        Ok(n as usize)
349    }
350
351    pub fn peek_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
352        self.recv_from_with_flags(buf, MSG_PEEK)
353    }
354
355    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
356        self.0.write(buf)
357    }
358
359    pub fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
360        self.0.write_vectored(bufs)
361    }
362
363    #[inline]
364    pub fn is_write_vectored(&self) -> bool {
365        self.0.is_write_vectored()
366    }
367
368    #[cfg(any(target_os = "android", target_os = "linux"))]
369    pub fn send_msg(&self, msg: &mut libc::msghdr) -> io::Result<usize> {
370        let n = cvt(unsafe { libc::sendmsg(self.as_raw_fd(), msg, 0) })?;
371        Ok(n as usize)
372    }
373
374    pub fn set_timeout(&self, dur: Option<Duration>, kind: libc::c_int) -> io::Result<()> {
375        let timeout = match dur {
376            Some(dur) => {
377                if dur.as_secs() == 0 && dur.subsec_nanos() == 0 {
378                    return Err(io::Error::ZERO_TIMEOUT);
379                }
380
381                let secs = if dur.as_secs() > libc::time_t::MAX as u64 {
382                    libc::time_t::MAX
383                } else {
384                    dur.as_secs() as libc::time_t
385                };
386                let mut timeout = libc::timeval {
387                    tv_sec: secs,
388                    tv_usec: dur.subsec_micros() as libc::suseconds_t,
389                };
390                if timeout.tv_sec == 0 && timeout.tv_usec == 0 {
391                    timeout.tv_usec = 1;
392                }
393                timeout
394            }
395            None => libc::timeval { tv_sec: 0, tv_usec: 0 },
396        };
397        setsockopt(self, libc::SOL_SOCKET, kind, timeout)
398    }
399
400    pub fn timeout(&self, kind: libc::c_int) -> io::Result<Option<Duration>> {
401        let raw: libc::timeval = getsockopt(self, libc::SOL_SOCKET, kind)?;
402        if raw.tv_sec == 0 && raw.tv_usec == 0 {
403            Ok(None)
404        } else {
405            let sec = raw.tv_sec as u64;
406            let nsec = (raw.tv_usec as u32) * 1000;
407            Ok(Some(Duration::new(sec, nsec)))
408        }
409    }
410
411    pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
412        let how = match how {
413            Shutdown::Write => libc::SHUT_WR,
414            Shutdown::Read => libc::SHUT_RD,
415            Shutdown::Both => libc::SHUT_RDWR,
416        };
417        cvt(unsafe { libc::shutdown(self.as_raw_fd(), how) })?;
418        Ok(())
419    }
420
421    pub fn set_linger(&self, linger: Option<Duration>) -> io::Result<()> {
422        let linger = libc::linger {
423            l_onoff: linger.is_some() as libc::c_int,
424            l_linger: linger.unwrap_or_default().as_secs() as libc::c_int,
425        };
426
427        setsockopt(self, libc::SOL_SOCKET, SO_LINGER, linger)
428    }
429
430    pub fn linger(&self) -> io::Result<Option<Duration>> {
431        let val: libc::linger = getsockopt(self, libc::SOL_SOCKET, SO_LINGER)?;
432
433        Ok((val.l_onoff != 0).then(|| Duration::from_secs(val.l_linger as u64)))
434    }
435
436    pub fn set_nodelay(&self, nodelay: bool) -> io::Result<()> {
437        setsockopt(self, libc::IPPROTO_TCP, libc::TCP_NODELAY, nodelay as c_int)
438    }
439
440    pub fn nodelay(&self) -> io::Result<bool> {
441        let raw: c_int = getsockopt(self, libc::IPPROTO_TCP, libc::TCP_NODELAY)?;
442        Ok(raw != 0)
443    }
444
445    #[cfg(any(target_os = "android", target_os = "linux",))]
446    pub fn set_quickack(&self, quickack: bool) -> io::Result<()> {
447        setsockopt(self, libc::IPPROTO_TCP, libc::TCP_QUICKACK, quickack as c_int)
448    }
449
450    #[cfg(any(target_os = "android", target_os = "linux",))]
451    pub fn quickack(&self) -> io::Result<bool> {
452        let raw: c_int = getsockopt(self, libc::IPPROTO_TCP, libc::TCP_QUICKACK)?;
453        Ok(raw != 0)
454    }
455
456    // bionic libc makes no use of this flag
457    #[cfg(target_os = "linux")]
458    pub fn set_deferaccept(&self, accept: u32) -> io::Result<()> {
459        setsockopt(self, libc::IPPROTO_TCP, libc::TCP_DEFER_ACCEPT, accept as c_int)
460    }
461
462    #[cfg(target_os = "linux")]
463    pub fn deferaccept(&self) -> io::Result<u32> {
464        let raw: c_int = getsockopt(self, libc::IPPROTO_TCP, libc::TCP_DEFER_ACCEPT)?;
465        Ok(raw as u32)
466    }
467
468    #[cfg(any(target_os = "freebsd", target_os = "netbsd"))]
469    pub fn set_acceptfilter(&self, name: &CStr) -> io::Result<()> {
470        if !name.to_bytes().is_empty() {
471            const AF_NAME_MAX: usize = 16;
472            let mut buf = [0; AF_NAME_MAX];
473            for (src, dst) in name.to_bytes().iter().zip(&mut buf[..AF_NAME_MAX - 1]) {
474                *dst = *src as libc::c_char;
475            }
476            let mut arg: libc::accept_filter_arg = unsafe { mem::zeroed() };
477            arg.af_name = buf;
478            setsockopt(self, libc::SOL_SOCKET, libc::SO_ACCEPTFILTER, &mut arg)
479        } else {
480            setsockopt(
481                self,
482                libc::SOL_SOCKET,
483                libc::SO_ACCEPTFILTER,
484                core::ptr::null_mut() as *mut c_void,
485            )
486        }
487    }
488
489    #[cfg(any(target_os = "freebsd", target_os = "netbsd"))]
490    pub fn acceptfilter(&self) -> io::Result<&CStr> {
491        let arg: libc::accept_filter_arg =
492            getsockopt(self, libc::SOL_SOCKET, libc::SO_ACCEPTFILTER)?;
493        let s: &[u8] =
494            unsafe { core::slice::from_raw_parts(arg.af_name.as_ptr() as *const u8, 16) };
495        let name = CStr::from_bytes_with_nul(s).unwrap();
496        Ok(name)
497    }
498
499    #[cfg(any(target_os = "android", target_os = "linux",))]
500    pub fn set_passcred(&self, passcred: bool) -> io::Result<()> {
501        setsockopt(self, libc::SOL_SOCKET, libc::SO_PASSCRED, passcred as libc::c_int)
502    }
503
504    #[cfg(any(target_os = "android", target_os = "linux",))]
505    pub fn passcred(&self) -> io::Result<bool> {
506        let passcred: libc::c_int = getsockopt(self, libc::SOL_SOCKET, libc::SO_PASSCRED)?;
507        Ok(passcred != 0)
508    }
509
510    #[cfg(target_os = "netbsd")]
511    pub fn set_local_creds(&self, local_creds: bool) -> io::Result<()> {
512        setsockopt(self, 0 as libc::c_int, libc::LOCAL_CREDS, local_creds as libc::c_int)
513    }
514
515    #[cfg(target_os = "netbsd")]
516    pub fn local_creds(&self) -> io::Result<bool> {
517        let local_creds: libc::c_int = getsockopt(self, 0 as libc::c_int, libc::LOCAL_CREDS)?;
518        Ok(local_creds != 0)
519    }
520
521    #[cfg(target_os = "freebsd")]
522    pub fn set_local_creds_persistent(&self, local_creds_persistent: bool) -> io::Result<()> {
523        setsockopt(
524            self,
525            libc::AF_LOCAL,
526            libc::LOCAL_CREDS_PERSISTENT,
527            local_creds_persistent as libc::c_int,
528        )
529    }
530
531    #[cfg(target_os = "freebsd")]
532    pub fn local_creds_persistent(&self) -> io::Result<bool> {
533        let local_creds_persistent: libc::c_int =
534            getsockopt(self, libc::AF_LOCAL, libc::LOCAL_CREDS_PERSISTENT)?;
535        Ok(local_creds_persistent != 0)
536    }
537
538    #[cfg(not(any(target_os = "solaris", target_os = "illumos", target_os = "vita")))]
539    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
540        let mut nonblocking = nonblocking as libc::c_int;
541        cvt(unsafe { libc::ioctl(self.as_raw_fd(), libc::FIONBIO, &mut nonblocking) }).map(drop)
542    }
543
544    #[cfg(target_os = "vita")]
545    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
546        let option = nonblocking as libc::c_int;
547        setsockopt(self, libc::SOL_SOCKET, libc::SO_NONBLOCK, option)
548    }
549
550    #[cfg(any(target_os = "solaris", target_os = "illumos"))]
551    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
552        // FIONBIO is inadequate for sockets on illumos/Solaris, so use the
553        // fcntl(F_[GS]ETFL)-based method provided by FileDesc instead.
554        self.0.set_nonblocking(nonblocking)
555    }
556
557    #[cfg(any(target_os = "linux", target_os = "freebsd", target_os = "openbsd"))]
558    pub fn set_mark(&self, mark: u32) -> io::Result<()> {
559        #[cfg(target_os = "linux")]
560        let option = libc::SO_MARK;
561        #[cfg(target_os = "freebsd")]
562        let option = libc::SO_USER_COOKIE;
563        #[cfg(target_os = "openbsd")]
564        let option = libc::SO_RTABLE;
565        setsockopt(self, libc::SOL_SOCKET, option, mark as libc::c_int)
566    }
567
568    pub fn take_error(&self) -> io::Result<Option<io::Error>> {
569        let raw: c_int = getsockopt(self, libc::SOL_SOCKET, libc::SO_ERROR)?;
570        if raw == 0 { Ok(None) } else { Ok(Some(io::Error::from_raw_os_error(raw as i32))) }
571    }
572
573    // This is used by sys_common code to abstract over Windows and Unix.
574    pub fn as_raw(&self) -> RawFd {
575        self.as_raw_fd()
576    }
577}
578
579impl AsInner<FileDesc> for Socket {
580    #[inline]
581    fn as_inner(&self) -> &FileDesc {
582        &self.0
583    }
584}
585
586impl IntoInner<FileDesc> for Socket {
587    fn into_inner(self) -> FileDesc {
588        self.0
589    }
590}
591
592impl FromInner<FileDesc> for Socket {
593    fn from_inner(file_desc: FileDesc) -> Self {
594        Self(file_desc)
595    }
596}
597
598impl AsFd for Socket {
599    fn as_fd(&self) -> BorrowedFd<'_> {
600        self.0.as_fd()
601    }
602}
603
604impl AsRawFd for Socket {
605    #[inline]
606    fn as_raw_fd(&self) -> RawFd {
607        self.0.as_raw_fd()
608    }
609}
610
611impl IntoRawFd for Socket {
612    fn into_raw_fd(self) -> RawFd {
613        self.0.into_raw_fd()
614    }
615}
616
617impl FromRawFd for Socket {
618    unsafe fn from_raw_fd(raw_fd: RawFd) -> Self {
619        Self(FromRawFd::from_raw_fd(raw_fd))
620    }
621}
622
623// In versions of glibc prior to 2.26, there's a bug where the DNS resolver
624// will cache the contents of /etc/resolv.conf, so changes to that file on disk
625// can be ignored by a long-running program. That can break DNS lookups on e.g.
626// laptops where the network comes and goes. See
627// https://sourceware.org/bugzilla/show_bug.cgi?id=984. Note however that some
628// distros including Debian have patched glibc to fix this for a long time.
629//
630// A workaround for this bug is to call the res_init libc function, to clear
631// the cached configs. Unfortunately, while we believe glibc's implementation
632// of res_init is thread-safe, we know that other implementations are not
633// (https://github.com/rust-lang/rust/issues/43592). Code here in std could
634// try to synchronize its res_init calls with a Mutex, but that wouldn't
635// protect programs that call into libc in other ways. So instead of calling
636// res_init unconditionally, we call it only when we detect we're linking
637// against glibc version < 2.26. (That is, when we both know its needed and
638// believe it's thread-safe).
639#[cfg(all(target_os = "linux", target_env = "gnu"))]
640fn on_resolver_failure() {
641    use crate::sys;
642
643    // If the version fails to parse, we treat it the same as "not glibc".
644    if let Some(version) = sys::os::glibc_version() {
645        if version < (2, 26) {
646            unsafe { libc::res_init() };
647        }
648    }
649}
650
651#[cfg(not(all(target_os = "linux", target_env = "gnu")))]
652fn on_resolver_failure() {}
std/sys/net/connection/socket/unix.rs

std/sys/net/connection/socket/
unix.rs
