summaryrefslogtreecommitdiff
path: root/src/sys/socket/mod.rs
blob: 4ee1aceec7d241a510ad875d7b41f59a327f16c2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
//! Socket interface functions
//!
//! [Further reading](http://man7.org/linux/man-pages/man7/socket.7.html)
use {Error, Result};
use errno::Errno;
use libc::{self, c_void, c_int, socklen_t, size_t};
use std::{fmt, mem, ptr, slice};
use std::os::unix::io::RawFd;
use sys::time::TimeVal;
use sys::uio::IoVec;

mod addr;
pub mod sockopt;

/*
 *
 * ===== Re-exports =====
 *
 */

pub use self::addr::{
    AddressFamily,
    SockAddr,
    InetAddr,
    UnixAddr,
    IpAddr,
    Ipv4Addr,
    Ipv6Addr,
    LinkAddr,
};
#[cfg(any(target_os = "linux", target_os = "android"))]
pub use ::sys::socket::addr::netlink::NetlinkAddr;

pub use libc::{
    cmsghdr,
    msghdr,
    sa_family_t,
    sockaddr,
    sockaddr_in,
    sockaddr_in6,
    sockaddr_storage,
    sockaddr_un,
};

/// These constants are used to specify the communication semantics
/// when creating a socket with [`socket()`](fn.socket.html)
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
#[repr(i32)]
pub enum SockType {
    /// Provides sequenced, reliable, two-way, connection-
    /// based byte streams.  An out-of-band data transmission
    /// mechanism may be supported.
    Stream = libc::SOCK_STREAM,
    /// Supports datagrams (connectionless, unreliable
    /// messages of a fixed maximum length).
    Datagram = libc::SOCK_DGRAM,
    /// Provides a sequenced, reliable, two-way connection-
    /// based data transmission path for datagrams of fixed
    /// maximum length; a consumer is required to read an
    /// entire packet with each input system call.
    SeqPacket = libc::SOCK_SEQPACKET,
    /// Provides raw network protocol access.
    Raw = libc::SOCK_RAW,
    /// Provides a reliable datagram layer that does not
    /// guarantee ordering.
    Rdm = libc::SOCK_RDM,
}

/// Constants used in [`socket`](fn.socket.html) and [`socketpair`](fn.socketpair.html)
/// to specify the protocol to use.
#[repr(i32)]
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum SockProtocol {
    /// TCP protocol ([ip(7)](http://man7.org/linux/man-pages/man7/ip.7.html))
    Tcp = libc::IPPROTO_TCP,
    /// UDP protocol ([ip(7)](http://man7.org/linux/man-pages/man7/ip.7.html))
    Udp = libc::IPPROTO_UDP,
    /// Allows applications and other KEXTs to be notified when certain kernel events occur
    /// ([ref](https://developer.apple.com/library/content/documentation/Darwin/Conceptual/NKEConceptual/control/control.html))
    #[cfg(any(target_os = "ios", target_os = "macos"))]
    KextEvent = libc::SYSPROTO_EVENT,
    /// Allows applications to configure and control a KEXT
    /// ([ref](https://developer.apple.com/library/content/documentation/Darwin/Conceptual/NKEConceptual/control/control.html))
    #[cfg(any(target_os = "ios", target_os = "macos"))]
    KextControl = libc::SYSPROTO_CONTROL,
}

libc_bitflags!{
    /// Additional socket options
    pub struct SockFlag: c_int {
        /// Set non-blocking mode on the new socket
        #[cfg(any(target_os = "android",
                  target_os = "dragonfly",
                  target_os = "freebsd",
                  target_os = "linux",
                  target_os = "netbsd",
                  target_os = "openbsd"))]
        SOCK_NONBLOCK;
        /// Set close-on-exec on the new descriptor
        #[cfg(any(target_os = "android",
                  target_os = "dragonfly",
                  target_os = "freebsd",
                  target_os = "linux",
                  target_os = "netbsd",
                  target_os = "openbsd"))]
        SOCK_CLOEXEC;
        /// Return `EPIPE` instead of raising `SIGPIPE`
        #[cfg(target_os = "netbsd")]
        SOCK_NOSIGPIPE;
        /// For domains `AF_INET(6)`, only allow `connect(2)`, `sendto(2)`, or `sendmsg(2)`
        /// to the DNS port (typically 53)
        #[cfg(target_os = "openbsd")]
        SOCK_DNS;
    }
}

libc_bitflags!{
    /// Flags for send/recv and their relatives
    pub struct MsgFlags: c_int {
        /// Sends or requests out-of-band data on sockets that support this notion
        /// (e.g., of type [`Stream`](enum.SockType.html)); the underlying protocol must also
        /// support out-of-band data.
        MSG_OOB;
        /// Peeks at an incoming message. The data is treated as unread and the next
        /// [`recv()`](fn.recv.html)
        /// or similar function shall still return this data.
        MSG_PEEK;
        /// Enables nonblocking operation; if the operation would block,
        /// `EAGAIN` or `EWOULDBLOCK` is returned.  This provides similar
        /// behavior to setting the `O_NONBLOCK` flag
        /// (via the [`fcntl`](../../fcntl/fn.fcntl.html)
        /// `F_SETFL` operation), but differs in that `MSG_DONTWAIT` is a per-
        /// call option, whereas `O_NONBLOCK` is a setting on the open file
        /// description (see [open(2)](http://man7.org/linux/man-pages/man2/open.2.html)),
        /// which will affect all threads in
        /// the calling process and as well as other processes that hold
        /// file descriptors referring to the same open file description.
        MSG_DONTWAIT;
        /// Receive flags: Control Data was discarded (buffer too small)
        MSG_CTRUNC;
        /// For raw ([`Packet`](addr/enum.AddressFamily.html)), Internet datagram
        /// (since Linux 2.4.27/2.6.8),
        /// netlink (since Linux 2.6.22) and UNIX datagram (since Linux 3.4)
        /// sockets: return the real length of the packet or datagram, even
        /// when it was longer than the passed buffer. Not implemented for UNIX
        /// domain ([unix(7)](https://linux.die.net/man/7/unix)) sockets.
        ///
        /// For use with Internet stream sockets, see [tcp(7)](https://linux.die.net/man/7/tcp).
        MSG_TRUNC;
        /// Terminates a record (when this notion is supported, as for
        /// sockets of type [`SeqPacket`](enum.SockType.html)).
        MSG_EOR;
        /// This flag specifies that queued errors should be received from
        /// the socket error queue. (For more details, see
        /// [recvfrom(2)](https://linux.die.net/man/2/recvfrom))
        #[cfg(any(target_os = "linux", target_os = "android"))]
        MSG_ERRQUEUE;
        /// Set the `close-on-exec` flag for the file descriptor received via a UNIX domain
        /// file descriptor using the `SCM_RIGHTS` operation (described in
        /// [unix(7)](https://linux.die.net/man/7/unix)).
        /// This flag is useful for the same reasons as the `O_CLOEXEC` flag of
        /// [open(2)](http://pubs.opengroup.org/onlinepubs/9699919799/functions/open.html).
        ///
        /// Only used in [`recvmsg`](fn.recvmsg.html) function.
        #[cfg(any(target_os = "android",
                  target_os = "dragonfly",
                  target_os = "freebsd",
                  target_os = "linux",
                  target_os = "netbsd",
                  target_os = "openbsd"))]
        MSG_CMSG_CLOEXEC;
    }
}

cfg_if! {
    if #[cfg(any(target_os = "android", target_os = "linux"))] {
        /// Unix credentials of the sending process.
        ///
        /// This struct is used with the `SO_PEERCRED` ancillary message for UNIX sockets.
        #[repr(C)]
        #[derive(Clone, Copy)]
        pub struct UnixCredentials(libc::ucred);

        impl UnixCredentials {
            /// Returns the process identifier
            pub fn pid(&self) -> libc::pid_t {
                self.0.pid
            }

            /// Returns the user identifier
            pub fn uid(&self) -> libc::uid_t {
                self.0.uid
            }

            /// Returns the group identifier
            pub fn gid(&self) -> libc::gid_t {
                self.0.gid
            }
        }

        impl PartialEq for UnixCredentials {
            fn eq(&self, other: &Self) -> bool {
                self.0.pid == other.0.pid && self.0.uid == other.0.uid && self.0.gid == other.0.gid
            }
        }
        impl Eq for UnixCredentials {}

        impl From<libc::ucred> for UnixCredentials {
            fn from(cred: libc::ucred) -> Self {
                UnixCredentials(cred)
            }
        }

        impl Into<libc::ucred> for UnixCredentials {
            fn into(self) -> libc::ucred {
                self.0
            }
        }

        impl fmt::Debug for UnixCredentials {
            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                f.debug_struct("UnixCredentials")
                    .field("pid", &self.0.pid)
                    .field("uid", &self.0.uid)
                    .field("gid", &self.0.gid)
                    .finish()
            }
        }
    }
}

/// Request for multicast socket operations
///
/// This is a wrapper type around `ip_mreq`.
#[repr(C)]
#[derive(Clone, Copy)]
pub struct IpMembershipRequest(libc::ip_mreq);

impl IpMembershipRequest {
    /// Instantiate a new `IpMembershipRequest`
    ///
    /// If `interface` is `None`, then `Ipv4Addr::any()` will be used for the interface.
    pub fn new(group: Ipv4Addr, interface: Option<Ipv4Addr>) -> Self {
        IpMembershipRequest(libc::ip_mreq {
            imr_multiaddr: group.0,
            imr_interface: interface.unwrap_or_else(Ipv4Addr::any).0,
        })
    }
}

impl PartialEq for IpMembershipRequest {
    fn eq(&self, other: &Self) -> bool {
        self.0.imr_multiaddr.s_addr == other.0.imr_multiaddr.s_addr
            && self.0.imr_interface.s_addr == other.0.imr_interface.s_addr
    }
}
impl Eq for IpMembershipRequest {}

impl fmt::Debug for IpMembershipRequest {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("IpMembershipRequest")
            .field("imr_multiaddr", &self.0.imr_multiaddr.s_addr)
            .field("imr_interface", &self.0.imr_interface.s_addr)
            .finish()
    }
}

/// Request for ipv6 multicast socket operations
///
/// This is a wrapper type around `ipv6_mreq`.
#[repr(C)]
#[derive(Clone, Copy)]
pub struct Ipv6MembershipRequest(libc::ipv6_mreq);

impl Ipv6MembershipRequest {
    /// Instantiate a new `Ipv6MembershipRequest`
    pub fn new(group: Ipv6Addr) -> Self {
        Ipv6MembershipRequest(libc::ipv6_mreq {
            ipv6mr_multiaddr: group.0,
            ipv6mr_interface: 0,
        })
    }
}

impl PartialEq for Ipv6MembershipRequest {
    fn eq(&self, other: &Self) -> bool {
        self.0.ipv6mr_multiaddr.s6_addr == other.0.ipv6mr_multiaddr.s6_addr &&
            self.0.ipv6mr_interface == other.0.ipv6mr_interface
    }
}
impl Eq for Ipv6MembershipRequest {}

impl fmt::Debug for Ipv6MembershipRequest {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Ipv6MembershipRequest")
            .field("ipv6mr_multiaddr", &self.0.ipv6mr_multiaddr.s6_addr)
            .field("ipv6mr_interface", &self.0.ipv6mr_interface)
            .finish()
    }
}

/// Copy the in-memory representation of `src` into the byte slice `dst`.
///
/// Returns the remainder of `dst`.
///
/// Panics when `dst` is too small for `src` (more precisely, panics if
/// `mem::size_of_val(src) >= dst.len()`).
///
/// Unsafe because it transmutes `src` to raw bytes, which is only safe for some
/// types `T`. Refer to the [Rustonomicon] for details.
///
/// [Rustonomicon]: https://doc.rust-lang.org/nomicon/transmutes.html
unsafe fn copy_bytes<'a, T: ?Sized>(src: &T, dst: &'a mut [u8]) -> &'a mut [u8] {
    let srclen = mem::size_of_val(src);
    ptr::copy_nonoverlapping(
        src as *const T as *const u8,
        dst[..srclen].as_mut_ptr(),
        srclen
    );

    &mut dst[srclen..]
}

/// Fills `dst` with `len` zero bytes and returns the remainder of the slice.
///
/// Panics when `len >= dst.len()`.
fn pad_bytes(len: usize, dst: &mut [u8]) -> &mut [u8] {
    for pad in &mut dst[..len] {
        *pad = 0;
    }

    &mut dst[len..]
}

cfg_if! {
    // Darwin and DragonFly BSD always align struct cmsghdr to 32-bit only.
    if #[cfg(any(target_os = "dragonfly", target_os = "ios", target_os = "macos"))] {
        type align_of_cmsg_data = u32;
    } else {
        type align_of_cmsg_data = size_t;
    }
}

/// A structure used to make room in a cmsghdr passed to recvmsg. The
/// size and alignment match that of a cmsghdr followed by a T, but the
/// fields are not accessible, as the actual types will change on a call
/// to recvmsg.
///
/// To make room for multiple messages, nest the type parameter with
/// tuples:
///
/// ```
/// use std::os::unix::io::RawFd;
/// use nix::sys::socket::CmsgSpace;
/// let cmsg: CmsgSpace<([RawFd; 3], CmsgSpace<[RawFd; 2]>)> = CmsgSpace::new();
/// ```
#[repr(C)]
#[allow(missing_debug_implementations)]
pub struct CmsgSpace<T> {
    _hdr: cmsghdr,
    _pad: [align_of_cmsg_data; 0],
    _data: T,
}

impl<T> CmsgSpace<T> {
    /// Create a CmsgSpace<T>. The structure is used only for space, so
    /// the fields are uninitialized.
    pub fn new() -> Self {
        // Safe because the fields themselves aren't accessible.
        unsafe { mem::uninitialized() }
    }
}

#[derive(Debug)]
pub struct RecvMsg<'a> {
    // The number of bytes received.
    pub bytes: usize,
    cmsg_buffer: &'a [u8],
    pub address: Option<SockAddr>,
    pub flags: MsgFlags,
}

impl<'a> RecvMsg<'a> {
    /// Iterate over the valid control messages pointed to by this
    /// msghdr.
    pub fn cmsgs(&self) -> CmsgIterator {
        CmsgIterator {
            buf: self.cmsg_buffer,
        }
    }
}

#[derive(Debug)]
pub struct CmsgIterator<'a> {
    /// Control message buffer to decode from. Must adhere to cmsg alignment.
    buf: &'a [u8],
}

impl<'a> Iterator for CmsgIterator<'a> {
    type Item = ControlMessage<'a>;

    // The implementation loosely follows CMSG_FIRSTHDR / CMSG_NXTHDR,
    // although we handle the invariants in slightly different places to
    // get a better iterator interface.
    fn next(&mut self) -> Option<ControlMessage<'a>> {
        if self.buf.len() == 0 {
            // The iterator assumes that `self.buf` always contains exactly the
            // bytes we need, so we're at the end when the buffer is empty.
            return None;
        }

        // Safe if: `self.buf` is `cmsghdr`-aligned.
        let cmsg: &'a cmsghdr = unsafe {
            &*(self.buf[..mem::size_of::<cmsghdr>()].as_ptr() as *const cmsghdr)
        };

        let cmsg_len = cmsg.cmsg_len as usize;

        // Advance our internal pointer.
        let cmsg_data = &self.buf[cmsg_align(mem::size_of::<cmsghdr>())..cmsg_len];
        self.buf = &self.buf[cmsg_align(cmsg_len)..];

        // Safe if: `cmsg_data` contains the expected (amount of) content. This
        // is verified by the kernel.
        unsafe {
            Some(ControlMessage::decode_from(cmsg, cmsg_data))
        }
    }
}

/// A type-safe wrapper around a single control message. More types may
/// be added to this enum; do not exhaustively pattern-match it.
/// [Further reading](http://man7.org/linux/man-pages/man3/cmsg.3.html)
#[allow(missing_debug_implementations)]
pub enum ControlMessage<'a> {
    /// A message of type `SCM_RIGHTS`, containing an array of file
    /// descriptors passed between processes.
    ///
    /// See the description in the "Ancillary messages" section of the
    /// [unix(7) man page](http://man7.org/linux/man-pages/man7/unix.7.html).
    ///
    /// Using multiple `ScmRights` messages for a single `sendmsg` call isn't recommended since it
    /// causes platform-dependent behaviour: It might swallow all but the first `ScmRights` message
    /// or fail with `EINVAL`. Instead, you can put all fds to be passed into a single `ScmRights`
    /// message.
    ScmRights(&'a [RawFd]),
    /// A message of type `SCM_CREDENTIALS`, containing the pid, uid and gid of
    /// a process connected to the socket.
    ///
    /// This is similar to the socket option `SO_PEERCRED`, but requires a
    /// process to explicitly send its credentials. A process running as root is
    /// allowed to specify any credentials, while credentials sent by other
    /// processes are verified by the kernel.
    ///
    /// For further information, please refer to the
    /// [`unix(7)`](http://man7.org/linux/man-pages/man7/unix.7.html) man page.
    // FIXME: When `#[repr(transparent)]` is stable, use it on `UnixCredentials`
    // and put that in here instead of a raw ucred.
    #[cfg(any(target_os = "android", target_os = "linux"))]
    ScmCredentials(&'a libc::ucred),
    /// A message of type `SCM_TIMESTAMP`, containing the time the
    /// packet was received by the kernel.
    ///
    /// See the kernel's explanation in "SO_TIMESTAMP" of
    /// [networking/timestamping](https://www.kernel.org/doc/Documentation/networking/timestamping.txt).
    ///
    /// # Examples
    ///
    // Disable this test on FreeBSD i386
    // https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=222039
    #[cfg_attr(not(all(target_os = "freebsd", target_arch = "x86")), doc = " ```")]
    #[cfg_attr(all(target_os = "freebsd", target_arch = "x86"), doc = " ```no_run")]
    /// use nix::sys::socket::*;
    /// use nix::sys::uio::IoVec;
    /// use nix::sys::time::*;
    /// use std::time::*;
    ///
    /// // Set up
    /// let message1 = "Ohayō!".as_bytes();
    /// let message2 = "Jā ne".as_bytes();
    /// let in_socket = socket(AddressFamily::Inet, SockType::Datagram, SockFlag::empty(), None).unwrap();
    /// setsockopt(in_socket, sockopt::ReceiveTimestamp, &true).unwrap();
    /// bind(in_socket, &SockAddr::new_inet(InetAddr::new(IpAddr::new_v4(127, 0, 0, 1), 0))).unwrap();
    /// let address = if let Ok(address) = getsockname(in_socket) { address } else { unreachable!() };
    ///
    /// // Send both
    /// assert!(Ok(message1.len()) == sendmsg(in_socket, &[IoVec::from_slice(message1)], &[], MsgFlags::empty(), Some(&address)));
    /// let time = SystemTime::now();
    /// std::thread::sleep(Duration::from_millis(250));
    /// assert!(Ok(message2.len()) == sendmsg(in_socket, &[IoVec::from_slice(message2)], &[], MsgFlags::empty(), Some(&address)));
    /// let delay = time.elapsed().unwrap();
    ///
    /// // Receive the first
    /// let mut buffer1 = vec![0u8; message1.len() + message2.len()];
    /// let mut time1: CmsgSpace<TimeVal> = CmsgSpace::new();
    /// let received1 = recvmsg(in_socket, &[IoVec::from_mut_slice(&mut buffer1)], Some(&mut time1), MsgFlags::empty()).unwrap();
    /// let mut time1 = if let Some(ControlMessage::ScmTimestamp(&time1)) = received1.cmsgs().next() { time1 } else { panic!("Unexpected or no control message") };
    ///
    /// // Receive the second
    /// let mut buffer2 = vec![0u8; message1.len() + message2.len()];
    /// let mut time2: CmsgSpace<TimeVal> = CmsgSpace::new();
    /// let received2 = recvmsg(in_socket, &[IoVec::from_mut_slice(&mut buffer2)], Some(&mut time2), MsgFlags::empty()).unwrap();
    /// let mut time2 = if let Some(ControlMessage::ScmTimestamp(&time2)) = received2.cmsgs().next() { time2 } else { panic!("Unexpected or no control message") };
    ///
    /// // Swap if needed; UDP is unordered
    /// match (received1.bytes, received2.bytes, message1.len(), message2.len()) {
    ///     (l1, l2, m1, m2) if l1 == m1 && l2 == m2 => {},
    ///     (l2, l1, m1, m2) if l1 == m1 && l2 == m2 => {
    ///         std::mem::swap(&mut time1, &mut time2);
    ///         std::mem::swap(&mut buffer1, &mut buffer2);
    ///     },
    ///     _ => panic!("Wrong packets"),
    /// };
    ///
    /// // Compare results
    /// println!("{:?} @ {:?}, {:?} @ {:?}, {:?}", buffer1, time1, buffer2, time2, delay);
    /// assert!(message1 == &buffer1[0..(message1.len())], "{:?} == {:?}", message1, buffer1);
    /// assert!(message2 == &buffer2[0..(message2.len())], "{:?} == {:?}", message2, buffer2);
    /// let time = time2 - time1;
    /// let time = Duration::new(time.num_seconds() as u64, time.num_nanoseconds() as u32);
    /// let difference = if delay < time { time - delay } else { delay - time };
    /// assert!(difference.subsec_nanos() < 5_000_000, "{}ns < 5ms", difference.subsec_nanos());
    /// assert!(difference.as_secs() == 0);
    ///
    /// // Close socket
    /// nix::unistd::close(in_socket).unwrap();
    /// ```
    ScmTimestamp(&'a TimeVal),
    /// Catch-all variant for unimplemented cmsg types.
    #[doc(hidden)]
    Unknown(UnknownCmsg<'a>),
}

// An opaque structure used to prevent cmsghdr from being a public type
#[doc(hidden)]
#[allow(missing_debug_implementations)]
pub struct UnknownCmsg<'a>(&'a cmsghdr, &'a [u8]);

// Round `len` up to meet the platform's required alignment for
// `cmsghdr`s and trailing `cmsghdr` data.  This should match the
// behaviour of CMSG_ALIGN from the Linux headers and do the correct
// thing on other platforms that don't usually provide CMSG_ALIGN.
#[inline]
fn cmsg_align(len: usize) -> usize {
    let align_bytes = mem::size_of::<align_of_cmsg_data>() - 1;
    (len + align_bytes) & !align_bytes
}

impl<'a> ControlMessage<'a> {
    /// The value of CMSG_SPACE on this message.
    fn space(&self) -> usize {
        cmsg_align(self.len())
    }

    /// The value of CMSG_LEN on this message.
    fn len(&self) -> usize {
        cmsg_align(mem::size_of::<cmsghdr>()) + match *self {
            ControlMessage::ScmRights(fds) => {
                mem::size_of_val(fds)
            },
            #[cfg(any(target_os = "android", target_os = "linux"))]
            ControlMessage::ScmCredentials(creds) => {
                mem::size_of_val(creds)
            }
            ControlMessage::ScmTimestamp(t) => {
                mem::size_of_val(t)
            },
            ControlMessage::Unknown(UnknownCmsg(_, bytes)) => {
                mem::size_of_val(bytes)
            }
        }
    }

    /// Returns the value to put into the `cmsg_type` field of the header.
    fn cmsg_type(&self) -> libc::c_int {
        match *self {
            ControlMessage::ScmRights(_) => libc::SCM_RIGHTS,
            #[cfg(any(target_os = "android", target_os = "linux"))]
            ControlMessage::ScmCredentials(_) => libc::SCM_CREDENTIALS,
            ControlMessage::ScmTimestamp(_) => libc::SCM_TIMESTAMP,
            ControlMessage::Unknown(ref cmsg) => cmsg.0.cmsg_type,
        }
    }

    // Unsafe: start and end of buffer must be cmsg_align'd. Updates
    // the provided slice; panics if the buffer is too small.
    unsafe fn encode_into(&self, buf: &mut [u8]) {
        let final_buf = if let ControlMessage::Unknown(ref cmsg) = *self {
            let &UnknownCmsg(orig_cmsg, bytes) = cmsg;

            let buf = copy_bytes(orig_cmsg, buf);

            let padlen = cmsg_align(mem::size_of_val(&orig_cmsg)) -
                mem::size_of_val(&orig_cmsg);
            let buf = pad_bytes(padlen, buf);

            copy_bytes(bytes, buf)
        } else {
            let cmsg = cmsghdr {
                cmsg_len: self.len() as _,
                cmsg_level: libc::SOL_SOCKET,
                cmsg_type: self.cmsg_type(),
                ..mem::zeroed() // zero out platform-dependent padding fields
            };
            let buf = copy_bytes(&cmsg, buf);

            let padlen = cmsg_align(mem::size_of_val(&cmsg)) -
                mem::size_of_val(&cmsg);
            let buf = pad_bytes(padlen, buf);

            match *self {
                ControlMessage::ScmRights(fds) => {
                    copy_bytes(fds, buf)
                },
                #[cfg(any(target_os = "android", target_os = "linux"))]
                ControlMessage::ScmCredentials(creds) => {
                    copy_bytes(creds, buf)
                }
                ControlMessage::ScmTimestamp(t) => {
                    copy_bytes(t, buf)
                },
                ControlMessage::Unknown(_) => unreachable!(),
            }
        };

        let padlen = self.space() - self.len();
        pad_bytes(padlen, final_buf);
    }

    /// Decodes a `ControlMessage` from raw bytes.
    ///
    /// This is only safe to call if the data is correct for the message type
    /// specified in the header. Normally, the kernel ensures that this is the
    /// case. "Correct" in this case includes correct length, alignment and
    /// actual content.
    unsafe fn decode_from(header: &'a cmsghdr, data: &'a [u8]) -> ControlMessage<'a> {
        match (header.cmsg_level, header.cmsg_type) {
            (libc::SOL_SOCKET, libc::SCM_RIGHTS) => {
                ControlMessage::ScmRights(
                    slice::from_raw_parts(data.as_ptr() as *const _,
                                          data.len() / mem::size_of::<RawFd>()))
            },
            #[cfg(any(target_os = "android", target_os = "linux"))]
            (libc::SOL_SOCKET, libc::SCM_CREDENTIALS) => {
                ControlMessage::ScmCredentials(
                    &*(data.as_ptr() as *const _)
                )
            }
            (libc::SOL_SOCKET, libc::SCM_TIMESTAMP) => {
                ControlMessage::ScmTimestamp(
                    &*(data.as_ptr() as *const _))
            },
            (_, _) => {
                ControlMessage::Unknown(UnknownCmsg(header, data))
            }
        }
    }
}


/// Send data in scatter-gather vectors to a socket, possibly accompanied
/// by ancillary data. Optionally direct the message at the given address,
/// as with sendto.
///
/// Allocates if cmsgs is nonempty.
pub fn sendmsg<'a>(fd: RawFd, iov: &[IoVec<&'a [u8]>], cmsgs: &[ControlMessage<'a>], flags: MsgFlags, addr: Option<&'a SockAddr>) -> Result<usize> {
    let mut capacity = 0;
    for cmsg in cmsgs {
        capacity += cmsg.space();
    }
    // Note that the resulting vector claims to have length == capacity,
    // so it's presently uninitialized.
    let mut cmsg_buffer = unsafe {
        let mut vec = Vec::<u8>::with_capacity(capacity);
        vec.set_len(capacity);
        vec
    };
    {
        let mut ofs = 0;
        for cmsg in cmsgs {
            let ptr = &mut cmsg_buffer[ofs..];
            unsafe {
                cmsg.encode_into(ptr);
            }
            ofs += cmsg.space();
        }
    }

    let (name, namelen) = match addr {
        Some(addr) => { let (x, y) = unsafe { addr.as_ffi_pair() }; (x as *const _, y) }
        None => (ptr::null(), 0),
    };

    let cmsg_ptr = if capacity > 0 {
        cmsg_buffer.as_ptr() as *const c_void
    } else {
        ptr::null()
    };

    let mhdr = unsafe {
        let mut mhdr: msghdr = mem::uninitialized();
        mhdr.msg_name =  name as *mut _;
        mhdr.msg_namelen =  namelen;
        mhdr.msg_iov =  iov.as_ptr() as *mut _;
        mhdr.msg_iovlen =  iov.len() as _;
        mhdr.msg_control =  cmsg_ptr as *mut _;
        mhdr.msg_controllen =  capacity as _;
        mhdr.msg_flags =  0;
        mhdr
    };
    let ret = unsafe { libc::sendmsg(fd, &mhdr, flags.bits()) };

    Errno::result(ret).map(|r| r as usize)
}

/// Receive message in scatter-gather vectors from a socket, and
/// optionally receive ancillary data into the provided buffer.
/// If no ancillary data is desired, use () as the type parameter.
pub fn recvmsg<'a, T>(fd: RawFd, iov: &[IoVec<&mut [u8]>], cmsg_buffer: Option<&'a mut CmsgSpace<T>>, flags: MsgFlags) -> Result<RecvMsg<'a>> {
    let mut address: sockaddr_storage = unsafe { mem::uninitialized() };
    let (msg_control, msg_controllen) = match cmsg_buffer {
        Some(cmsg_buffer) => (cmsg_buffer as *mut _, mem::size_of_val(cmsg_buffer)),
        None => (ptr::null_mut(), 0),
    };
    let mut mhdr = unsafe {
        let mut mhdr: msghdr = mem::uninitialized();
        mhdr.msg_name =  &mut address as *mut _ as *mut _;
        mhdr.msg_namelen =  mem::size_of::<sockaddr_storage>() as socklen_t;
        mhdr.msg_iov =  iov.as_ptr() as *mut _;
        mhdr.msg_iovlen =  iov.len() as _;
        mhdr.msg_control =  msg_control as *mut _;
        mhdr.msg_controllen =  msg_controllen as _;
        mhdr.msg_flags =  0;
        mhdr
    };
    let ret = unsafe { libc::recvmsg(fd, &mut mhdr, flags.bits()) };

    let cmsg_buffer = if msg_controllen > 0 {
        // got control message(s)
        debug_assert!(!mhdr.msg_control.is_null());
        unsafe {
            // Safe: The pointer is not null and the length is correct as part of `recvmsg`s
            // contract.
            slice::from_raw_parts(mhdr.msg_control as *const u8,
                                  mhdr.msg_controllen as usize)
        }
    } else {
        // No control message, create an empty buffer to avoid creating a slice from a null pointer
        &[]
    };

    Ok(unsafe { RecvMsg {
        bytes: try!(Errno::result(ret)) as usize,
        cmsg_buffer,
        address: sockaddr_storage_to_addr(&address,
                                          mhdr.msg_namelen as usize).ok(),
        flags: MsgFlags::from_bits_truncate(mhdr.msg_flags),
    } })
}


/// Create an endpoint for communication
///
/// The `protocol` specifies a particular protocol to be used with the
/// socket.  Normally only a single protocol exists to support a
/// particular socket type within a given protocol family, in which case
/// protocol can be specified as `None`.  However, it is possible that many
/// protocols may exist, in which case a particular protocol must be
/// specified in this manner.
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/socket.html)
pub fn socket<T: Into<Option<SockProtocol>>>(domain: AddressFamily, ty: SockType, flags: SockFlag, protocol: T) -> Result<RawFd> {
    let protocol = match protocol.into() {
        None => 0,
        Some(p) => p as c_int,
    };

    // SockFlags are usually embedded into `ty`, but we don't do that in `nix` because it's a
    // little easier to understand by separating it out. So we have to merge these bitfields
    // here.
    let mut ty = ty as c_int;
    ty |= flags.bits();

    let res = unsafe { libc::socket(domain as c_int, ty, protocol) };

    Errno::result(res)
}

/// Create a pair of connected sockets
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/socketpair.html)
pub fn socketpair<T: Into<Option<SockProtocol>>>(domain: AddressFamily, ty: SockType, protocol: T,
                  flags: SockFlag) -> Result<(RawFd, RawFd)> {
    let protocol = match protocol.into() {
        None => 0,
        Some(p) => p as c_int,
    };

    // SockFlags are usually embedded into `ty`, but we don't do that in `nix` because it's a
    // little easier to understand by separating it out. So we have to merge these bitfields
    // here.
    let mut ty = ty as c_int;
    ty |= flags.bits();

    let mut fds = [-1, -1];

    let res = unsafe { libc::socketpair(domain as c_int, ty, protocol, fds.as_mut_ptr()) };
    Errno::result(res)?;

    Ok((fds[0], fds[1]))
}

/// Listen for connections on a socket
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/listen.html)
pub fn listen(sockfd: RawFd, backlog: usize) -> Result<()> {
    let res = unsafe { libc::listen(sockfd, backlog as c_int) };

    Errno::result(res).map(drop)
}

/// Bind a name to a socket
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/bind.html)
pub fn bind(fd: RawFd, addr: &SockAddr) -> Result<()> {
    let res = unsafe {
        let (ptr, len) = addr.as_ffi_pair();
        libc::bind(fd, ptr, len)
    };

    Errno::result(res).map(drop)
}

/// Accept a connection on a socket
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/accept.html)
pub fn accept(sockfd: RawFd) -> Result<RawFd> {
    let res = unsafe { libc::accept(sockfd, ptr::null_mut(), ptr::null_mut()) };

    Errno::result(res)
}

/// Accept a connection on a socket
///
/// [Further reading](http://man7.org/linux/man-pages/man2/accept.2.html)
#[cfg(any(target_os = "android",
          target_os = "freebsd",
          target_os = "linux",
          target_os = "openbsd"))]
pub fn accept4(sockfd: RawFd, flags: SockFlag) -> Result<RawFd> {
    let res = unsafe { libc::accept4(sockfd, ptr::null_mut(), ptr::null_mut(), flags.bits()) };

    Errno::result(res)
}

/// Initiate a connection on a socket
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/connect.html)
pub fn connect(fd: RawFd, addr: &SockAddr) -> Result<()> {
    let res = unsafe {
        let (ptr, len) = addr.as_ffi_pair();
        libc::connect(fd, ptr, len)
    };

    Errno::result(res).map(drop)
}

/// Receive data from a connection-oriented socket. Returns the number of
/// bytes read
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/recv.html)
pub fn recv(sockfd: RawFd, buf: &mut [u8], flags: MsgFlags) -> Result<usize> {
    unsafe {
        let ret = libc::recv(
            sockfd,
            buf.as_ptr() as *mut c_void,
            buf.len() as size_t,
            flags.bits());

        Errno::result(ret).map(|r| r as usize)
    }
}

/// Receive data from a connectionless or connection-oriented socket. Returns
/// the number of bytes read and the socket address of the sender.
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/recvfrom.html)
pub fn recvfrom(sockfd: RawFd, buf: &mut [u8]) -> Result<(usize, SockAddr)> {
    unsafe {
        let addr: sockaddr_storage = mem::zeroed();
        let mut len = mem::size_of::<sockaddr_storage>() as socklen_t;

        let ret = try!(Errno::result(libc::recvfrom(
            sockfd,
            buf.as_ptr() as *mut c_void,
            buf.len() as size_t,
            0,
            mem::transmute(&addr),
            &mut len as *mut socklen_t)));

        sockaddr_storage_to_addr(&addr, len as usize)
            .map(|addr| (ret as usize, addr))
    }
}

/// Send a message to a socket
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/sendto.html)
pub fn sendto(fd: RawFd, buf: &[u8], addr: &SockAddr, flags: MsgFlags) -> Result<usize> {
    let ret = unsafe {
        let (ptr, len) = addr.as_ffi_pair();
        libc::sendto(fd, buf.as_ptr() as *const c_void, buf.len() as size_t, flags.bits(), ptr, len)
    };

    Errno::result(ret).map(|r| r as usize)
}

/// Send data to a connection-oriented socket. Returns the number of bytes read
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/send.html)
pub fn send(fd: RawFd, buf: &[u8], flags: MsgFlags) -> Result<usize> {
    let ret = unsafe {
        libc::send(fd, buf.as_ptr() as *const c_void, buf.len() as size_t, flags.bits())
    };

    Errno::result(ret).map(|r| r as usize)
}

/*
 *
 * ===== Socket Options =====
 *
 */

/// The protocol level at which to get / set socket options. Used as an
/// argument to `getsockopt` and `setsockopt`.
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/setsockopt.html)
#[repr(i32)]
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum SockLevel {
    Socket = libc::SOL_SOCKET,
    Tcp = libc::IPPROTO_TCP,
    Ip = libc::IPPROTO_IP,
    Ipv6 = libc::IPPROTO_IPV6,
    Udp = libc::IPPROTO_UDP,
    #[cfg(any(target_os = "android", target_os = "linux"))]
    Netlink = libc::SOL_NETLINK,
}

/// Represents a socket option that can be accessed or set. Used as an argument
/// to `getsockopt`
pub trait GetSockOpt : Copy {
    type Val;

    #[doc(hidden)]
    fn get(&self, fd: RawFd) -> Result<Self::Val>;
}

/// Represents a socket option that can be accessed or set. Used as an argument
/// to `setsockopt`
pub trait SetSockOpt : Copy {
    type Val;

    #[doc(hidden)]
    fn set(&self, fd: RawFd, val: &Self::Val) -> Result<()>;
}

/// Get the current value for the requested socket option
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/getsockopt.html)
pub fn getsockopt<O: GetSockOpt>(fd: RawFd, opt: O) -> Result<O::Val> {
    opt.get(fd)
}

/// Sets the value for the requested socket option
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/setsockopt.html)
pub fn setsockopt<O: SetSockOpt>(fd: RawFd, opt: O, val: &O::Val) -> Result<()> {
    opt.set(fd, val)
}

/// Get the address of the peer connected to the socket `fd`.
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/getpeername.html)
pub fn getpeername(fd: RawFd) -> Result<SockAddr> {
    unsafe {
        let addr: sockaddr_storage = mem::uninitialized();
        let mut len = mem::size_of::<sockaddr_storage>() as socklen_t;

        let ret = libc::getpeername(fd, mem::transmute(&addr), &mut len);

        try!(Errno::result(ret));

        sockaddr_storage_to_addr(&addr, len as usize)
    }
}

/// Get the current address to which the socket `fd` is bound.
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/getsockname.html)
pub fn getsockname(fd: RawFd) -> Result<SockAddr> {
    unsafe {
        let addr: sockaddr_storage = mem::uninitialized();
        let mut len = mem::size_of::<sockaddr_storage>() as socklen_t;

        let ret = libc::getsockname(fd, mem::transmute(&addr), &mut len);

        try!(Errno::result(ret));

        sockaddr_storage_to_addr(&addr, len as usize)
    }
}

/// Return the appropriate `SockAddr` type from a `sockaddr_storage` of a certain
/// size.  In C this would usually be done by casting.  The `len` argument
/// should be the number of bytes in the `sockaddr_storage` that are actually
/// allocated and valid.  It must be at least as large as all the useful parts
/// of the structure.  Note that in the case of a `sockaddr_un`, `len` need not
/// include the terminating null.
pub unsafe fn sockaddr_storage_to_addr(
    addr: &sockaddr_storage,
    len: usize) -> Result<SockAddr> {

    if len < mem::size_of_val(&addr.ss_family) {
        return Err(Error::Sys(Errno::ENOTCONN));
    }

    match addr.ss_family as c_int {
        libc::AF_INET => {
            assert!(len as usize == mem::size_of::<sockaddr_in>());
            let ret = *(addr as *const _ as *const sockaddr_in);
            Ok(SockAddr::Inet(InetAddr::V4(ret)))
        }
        libc::AF_INET6 => {
            assert!(len as usize == mem::size_of::<sockaddr_in6>());
            Ok(SockAddr::Inet(InetAddr::V6(*(addr as *const _ as *const sockaddr_in6))))
        }
        libc::AF_UNIX => {
            let sun = *(addr as *const _ as *const sockaddr_un);
            let pathlen = len - offset_of!(sockaddr_un, sun_path);
            Ok(SockAddr::Unix(UnixAddr(sun, pathlen)))
        }
        #[cfg(any(target_os = "linux", target_os = "android"))]
        libc::AF_NETLINK => {
            use libc::sockaddr_nl;
            Ok(SockAddr::Netlink(NetlinkAddr(*(addr as *const _ as *const sockaddr_nl))))
        }
        af => panic!("unexpected address family {}", af),
    }
}


#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub enum Shutdown {
    /// Further receptions will be disallowed.
    Read,
    /// Further  transmissions will be disallowed.
    Write,
    /// Further receptions and transmissions will be disallowed.
    Both,
}

/// Shut down part of a full-duplex connection.
///
/// [Further reading](http://pubs.opengroup.org/onlinepubs/9699919799/functions/shutdown.html)
pub fn shutdown(df: RawFd, how: Shutdown) -> Result<()> {
    unsafe {
        use libc::shutdown;

        let how = match how {
            Shutdown::Read  => libc::SHUT_RD,
            Shutdown::Write => libc::SHUT_WR,
            Shutdown::Both  => libc::SHUT_RDWR,
        };

        Errno::result(shutdown(df, how)).map(drop)
    }
}