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
#[cfg(all(test, not(target_os = "emscripten")))]
mod tests;

use crate::cmp::Ordering;
use crate::fmt;
use crate::hash;
use crate::io::{self, Write};
use crate::iter;
use crate::mem;
use crate::net::{IpAddr, Ipv4Addr, Ipv6Addr};
use crate::option;
use crate::slice;
use crate::sys::net::netc as c;
use crate::sys_common::net::LookupHost;
use crate::sys_common::{FromInner, IntoInner};
use crate::vec;

/// An internet socket address, either IPv4 or IPv6.
///
/// Internet socket addresses consist of an [IP address], a 16-bit port number, as well
/// as possibly some version-dependent additional information. See [`SocketAddrV4`]'s and
/// [`SocketAddrV6`]'s respective documentation for more details.
///
/// The size of a `SocketAddr` instance may vary depending on the target operating
/// system.
///
/// [IP address]: IpAddr
///
/// # Examples
///
/// ```
/// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
///
/// let socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
///
/// assert_eq!("127.0.0.1:8080".parse(), Ok(socket));
/// assert_eq!(socket.port(), 8080);
/// assert_eq!(socket.is_ipv4(), true);
/// ```
#[derive(Copy, Clone, PartialEq, Eq, Hash, PartialOrd, Ord)]
#[stable(feature = "rust1", since = "1.0.0")]
pub enum SocketAddr {
    /// An IPv4 socket address.
    #[stable(feature = "rust1", since = "1.0.0")]
    V4(#[stable(feature = "rust1", since = "1.0.0")] SocketAddrV4),
    /// An IPv6 socket address.
    #[stable(feature = "rust1", since = "1.0.0")]
    V6(#[stable(feature = "rust1", since = "1.0.0")] SocketAddrV6),
}

/// An IPv4 socket address.
///
/// IPv4 socket addresses consist of an [`IPv4` address] and a 16-bit port number, as
/// stated in [IETF RFC 793].
///
/// See [`SocketAddr`] for a type encompassing both IPv4 and IPv6 socket addresses.
///
/// The size of a `SocketAddrV4` struct may vary depending on the target operating
/// system. Do not assume that this type has the same memory layout as the underlying
/// system representation.
///
/// [IETF RFC 793]: https://tools.ietf.org/html/rfc793
/// [`IPv4` address]: Ipv4Addr
///
/// # Examples
///
/// ```
/// use std::net::{Ipv4Addr, SocketAddrV4};
///
/// let socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
///
/// assert_eq!("127.0.0.1:8080".parse(), Ok(socket));
/// assert_eq!(socket.ip(), &Ipv4Addr::new(127, 0, 0, 1));
/// assert_eq!(socket.port(), 8080);
/// ```
#[derive(Copy, Clone, Eq, PartialEq)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct SocketAddrV4 {
    ip: Ipv4Addr,
    port: u16,
}

/// An IPv6 socket address.
///
/// IPv6 socket addresses consist of an [`IPv6` address], a 16-bit port number, as well
/// as fields containing the traffic class, the flow label, and a scope identifier
/// (see [IETF RFC 2553, Section 3.3] for more details).
///
/// See [`SocketAddr`] for a type encompassing both IPv4 and IPv6 socket addresses.
///
/// The size of a `SocketAddrV6` struct may vary depending on the target operating
/// system. Do not assume that this type has the same memory layout as the underlying
/// system representation.
///
/// [IETF RFC 2553, Section 3.3]: https://tools.ietf.org/html/rfc2553#section-3.3
/// [`IPv6` address]: Ipv6Addr
///
/// # Examples
///
/// ```
/// use std::net::{Ipv6Addr, SocketAddrV6};
///
/// let socket = SocketAddrV6::new(Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
///
/// assert_eq!("[2001:db8::1]:8080".parse(), Ok(socket));
/// assert_eq!(socket.ip(), &Ipv6Addr::new(0x2001, 0xdb8, 0, 0, 0, 0, 0, 1));
/// assert_eq!(socket.port(), 8080);
/// ```
#[derive(Copy, Clone, Eq, PartialEq)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct SocketAddrV6 {
    ip: Ipv6Addr,
    port: u16,
    flowinfo: u32,
    scope_id: u32,
}

impl SocketAddr {
    /// Creates a new socket address from an [IP address] and a port number.
    ///
    /// [IP address]: IpAddr
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// assert_eq!(socket.ip(), IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)));
    /// assert_eq!(socket.port(), 8080);
    /// ```
    #[stable(feature = "ip_addr", since = "1.7.0")]
    #[must_use]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn new(ip: IpAddr, port: u16) -> SocketAddr {
        match ip {
            IpAddr::V4(a) => SocketAddr::V4(SocketAddrV4::new(a, port)),
            IpAddr::V6(a) => SocketAddr::V6(SocketAddrV6::new(a, port, 0, 0)),
        }
    }

    /// Returns the IP address associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// assert_eq!(socket.ip(), IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)));
    /// ```
    #[must_use]
    #[stable(feature = "ip_addr", since = "1.7.0")]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn ip(&self) -> IpAddr {
        match *self {
            SocketAddr::V4(ref a) => IpAddr::V4(*a.ip()),
            SocketAddr::V6(ref a) => IpAddr::V6(*a.ip()),
        }
    }

    /// Changes the IP address associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let mut socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// socket.set_ip(IpAddr::V4(Ipv4Addr::new(10, 10, 0, 1)));
    /// assert_eq!(socket.ip(), IpAddr::V4(Ipv4Addr::new(10, 10, 0, 1)));
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    pub fn set_ip(&mut self, new_ip: IpAddr) {
        // `match (*self, new_ip)` would have us mutate a copy of self only to throw it away.
        match (self, new_ip) {
            (&mut SocketAddr::V4(ref mut a), IpAddr::V4(new_ip)) => a.set_ip(new_ip),
            (&mut SocketAddr::V6(ref mut a), IpAddr::V6(new_ip)) => a.set_ip(new_ip),
            (self_, new_ip) => *self_ = Self::new(new_ip, self_.port()),
        }
    }

    /// Returns the port number associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// assert_eq!(socket.port(), 8080);
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn port(&self) -> u16 {
        match *self {
            SocketAddr::V4(ref a) => a.port(),
            SocketAddr::V6(ref a) => a.port(),
        }
    }

    /// Changes the port number associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let mut socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// socket.set_port(1025);
    /// assert_eq!(socket.port(), 1025);
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    pub fn set_port(&mut self, new_port: u16) {
        match *self {
            SocketAddr::V4(ref mut a) => a.set_port(new_port),
            SocketAddr::V6(ref mut a) => a.set_port(new_port),
        }
    }

    /// Returns [`true`] if the [IP address] in this `SocketAddr` is an
    /// [`IPv4` address], and [`false`] otherwise.
    ///
    /// [IP address]: IpAddr
    /// [`IPv4` address]: IpAddr::V4
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv4Addr, SocketAddr};
    ///
    /// let socket = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 8080);
    /// assert_eq!(socket.is_ipv4(), true);
    /// assert_eq!(socket.is_ipv6(), false);
    /// ```
    #[must_use]
    #[stable(feature = "sockaddr_checker", since = "1.16.0")]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn is_ipv4(&self) -> bool {
        matches!(*self, SocketAddr::V4(_))
    }

    /// Returns [`true`] if the [IP address] in this `SocketAddr` is an
    /// [`IPv6` address], and [`false`] otherwise.
    ///
    /// [IP address]: IpAddr
    /// [`IPv6` address]: IpAddr::V6
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{IpAddr, Ipv6Addr, SocketAddr};
    ///
    /// let socket = SocketAddr::new(IpAddr::V6(Ipv6Addr::new(0, 0, 0, 0, 0, 65535, 0, 1)), 8080);
    /// assert_eq!(socket.is_ipv4(), false);
    /// assert_eq!(socket.is_ipv6(), true);
    /// ```
    #[must_use]
    #[stable(feature = "sockaddr_checker", since = "1.16.0")]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn is_ipv6(&self) -> bool {
        matches!(*self, SocketAddr::V6(_))
    }
}

impl SocketAddrV4 {
    /// Creates a new socket address from an [`IPv4` address] and a port number.
    ///
    /// [`IPv4` address]: Ipv4Addr
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV4, Ipv4Addr};
    ///
    /// let socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[must_use]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn new(ip: Ipv4Addr, port: u16) -> SocketAddrV4 {
        SocketAddrV4 { ip, port }
    }

    /// Returns the IP address associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV4, Ipv4Addr};
    ///
    /// let socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
    /// assert_eq!(socket.ip(), &Ipv4Addr::new(127, 0, 0, 1));
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn ip(&self) -> &Ipv4Addr {
        &self.ip
    }

    /// Changes the IP address associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV4, Ipv4Addr};
    ///
    /// let mut socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
    /// socket.set_ip(Ipv4Addr::new(192, 168, 0, 1));
    /// assert_eq!(socket.ip(), &Ipv4Addr::new(192, 168, 0, 1));
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    pub fn set_ip(&mut self, new_ip: Ipv4Addr) {
        self.ip = new_ip;
    }

    /// Returns the port number associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV4, Ipv4Addr};
    ///
    /// let socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
    /// assert_eq!(socket.port(), 8080);
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn port(&self) -> u16 {
        self.port
    }

    /// Changes the port number associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV4, Ipv4Addr};
    ///
    /// let mut socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
    /// socket.set_port(4242);
    /// assert_eq!(socket.port(), 4242);
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    pub fn set_port(&mut self, new_port: u16) {
        self.port = new_port;
    }
}

impl SocketAddrV6 {
    /// Creates a new socket address from an [`IPv6` address], a 16-bit port number,
    /// and the `flowinfo` and `scope_id` fields.
    ///
    /// For more information on the meaning and layout of the `flowinfo` and `scope_id`
    /// parameters, see [IETF RFC 2553, Section 3.3].
    ///
    /// [IETF RFC 2553, Section 3.3]: https://tools.ietf.org/html/rfc2553#section-3.3
    /// [`IPv6` address]: Ipv6Addr
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
    /// ```
    #[stable(feature = "rust1", since = "1.0.0")]
    #[must_use]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn new(ip: Ipv6Addr, port: u16, flowinfo: u32, scope_id: u32) -> SocketAddrV6 {
        SocketAddrV6 { ip, port, flowinfo, scope_id }
    }

    /// Returns the IP address associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
    /// assert_eq!(socket.ip(), &Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1));
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn ip(&self) -> &Ipv6Addr {
        &self.ip
    }

    /// Changes the IP address associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let mut socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
    /// socket.set_ip(Ipv6Addr::new(76, 45, 0, 0, 0, 0, 0, 0));
    /// assert_eq!(socket.ip(), &Ipv6Addr::new(76, 45, 0, 0, 0, 0, 0, 0));
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    pub fn set_ip(&mut self, new_ip: Ipv6Addr) {
        self.ip = new_ip;
    }

    /// Returns the port number associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
    /// assert_eq!(socket.port(), 8080);
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn port(&self) -> u16 {
        self.port
    }

    /// Changes the port number associated with this socket address.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let mut socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 0);
    /// socket.set_port(4242);
    /// assert_eq!(socket.port(), 4242);
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    pub fn set_port(&mut self, new_port: u16) {
        self.port = new_port;
    }

    /// Returns the flow information associated with this address.
    ///
    /// This information corresponds to the `sin6_flowinfo` field in C's `netinet/in.h`,
    /// as specified in [IETF RFC 2553, Section 3.3].
    /// It combines information about the flow label and the traffic class as specified
    /// in [IETF RFC 2460], respectively [Section 6] and [Section 7].
    ///
    /// [IETF RFC 2553, Section 3.3]: https://tools.ietf.org/html/rfc2553#section-3.3
    /// [IETF RFC 2460]: https://tools.ietf.org/html/rfc2460
    /// [Section 6]: https://tools.ietf.org/html/rfc2460#section-6
    /// [Section 7]: https://tools.ietf.org/html/rfc2460#section-7
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 10, 0);
    /// assert_eq!(socket.flowinfo(), 10);
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn flowinfo(&self) -> u32 {
        self.flowinfo
    }

    /// Changes the flow information associated with this socket address.
    ///
    /// See [`SocketAddrV6::flowinfo`]'s documentation for more details.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let mut socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 10, 0);
    /// socket.set_flowinfo(56);
    /// assert_eq!(socket.flowinfo(), 56);
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    pub fn set_flowinfo(&mut self, new_flowinfo: u32) {
        self.flowinfo = new_flowinfo;
    }

    /// Returns the scope ID associated with this address.
    ///
    /// This information corresponds to the `sin6_scope_id` field in C's `netinet/in.h`,
    /// as specified in [IETF RFC 2553, Section 3.3].
    ///
    /// [IETF RFC 2553, Section 3.3]: https://tools.ietf.org/html/rfc2553#section-3.3
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 78);
    /// assert_eq!(socket.scope_id(), 78);
    /// ```
    #[must_use]
    #[stable(feature = "rust1", since = "1.0.0")]
    #[rustc_const_unstable(feature = "const_socketaddr", issue = "82485")]
    pub const fn scope_id(&self) -> u32 {
        self.scope_id
    }

    /// Changes the scope ID associated with this socket address.
    ///
    /// See [`SocketAddrV6::scope_id`]'s documentation for more details.
    ///
    /// # Examples
    ///
    /// ```
    /// use std::net::{SocketAddrV6, Ipv6Addr};
    ///
    /// let mut socket = SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), 8080, 0, 78);
    /// socket.set_scope_id(42);
    /// assert_eq!(socket.scope_id(), 42);
    /// ```
    #[stable(feature = "sockaddr_setters", since = "1.9.0")]
    pub fn set_scope_id(&mut self, new_scope_id: u32) {
        self.scope_id = new_scope_id;
    }
}

impl FromInner<c::sockaddr_in> for SocketAddrV4 {
    fn from_inner(addr: c::sockaddr_in) -> SocketAddrV4 {
        SocketAddrV4 { ip: Ipv4Addr::from_inner(addr.sin_addr), port: u16::from_be(addr.sin_port) }
    }
}

impl FromInner<c::sockaddr_in6> for SocketAddrV6 {
    fn from_inner(addr: c::sockaddr_in6) -> SocketAddrV6 {
        SocketAddrV6 {
            ip: Ipv6Addr::from_inner(addr.sin6_addr),
            port: u16::from_be(addr.sin6_port),
            flowinfo: addr.sin6_flowinfo,
            scope_id: addr.sin6_scope_id,
        }
    }
}

impl IntoInner<c::sockaddr_in> for SocketAddrV4 {
    fn into_inner(self) -> c::sockaddr_in {
        c::sockaddr_in {
            sin_family: c::AF_INET as c::sa_family_t,
            sin_port: self.port.to_be(),
            sin_addr: self.ip.into_inner(),
            ..unsafe { mem::zeroed() }
        }
    }
}

impl IntoInner<c::sockaddr_in6> for SocketAddrV6 {
    fn into_inner(self) -> c::sockaddr_in6 {
        c::sockaddr_in6 {
            sin6_family: c::AF_INET6 as c::sa_family_t,
            sin6_port: self.port.to_be(),
            sin6_addr: self.ip.into_inner(),
            sin6_flowinfo: self.flowinfo,
            sin6_scope_id: self.scope_id,
            ..unsafe { mem::zeroed() }
        }
    }
}

#[stable(feature = "ip_from_ip", since = "1.16.0")]
impl From<SocketAddrV4> for SocketAddr {
    /// Converts a [`SocketAddrV4`] into a [`SocketAddr::V4`].
    fn from(sock4: SocketAddrV4) -> SocketAddr {
        SocketAddr::V4(sock4)
    }
}

#[stable(feature = "ip_from_ip", since = "1.16.0")]
impl From<SocketAddrV6> for SocketAddr {
    /// Converts a [`SocketAddrV6`] into a [`SocketAddr::V6`].
    fn from(sock6: SocketAddrV6) -> SocketAddr {
        SocketAddr::V6(sock6)
    }
}

#[stable(feature = "addr_from_into_ip", since = "1.17.0")]
impl<I: Into<IpAddr>> From<(I, u16)> for SocketAddr {
    /// Converts a tuple struct (Into<[`IpAddr`]>, `u16`) into a [`SocketAddr`].
    ///
    /// This conversion creates a [`SocketAddr::V4`] for an [`IpAddr::V4`]
    /// and creates a [`SocketAddr::V6`] for an [`IpAddr::V6`].
    ///
    /// `u16` is treated as port of the newly created [`SocketAddr`].
    fn from(pieces: (I, u16)) -> SocketAddr {
        SocketAddr::new(pieces.0.into(), pieces.1)
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Display for SocketAddr {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match *self {
            SocketAddr::V4(ref a) => a.fmt(f),
            SocketAddr::V6(ref a) => a.fmt(f),
        }
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for SocketAddr {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(self, fmt)
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Display for SocketAddrV4 {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // Fast path: if there's no alignment stuff, write to the output buffer
        // directly
        if f.precision().is_none() && f.width().is_none() {
            write!(f, "{}:{}", self.ip(), self.port())
        } else {
            const IPV4_SOCKET_BUF_LEN: usize = (3 * 4)  // the segments
                + 3  // the separators
                + 1 + 5; // the port
            let mut buf = [0; IPV4_SOCKET_BUF_LEN];
            let mut buf_slice = &mut buf[..];

            // Unwrap is fine because writing to a sufficiently-sized
            // buffer is infallible
            write!(buf_slice, "{}:{}", self.ip(), self.port()).unwrap();
            let len = IPV4_SOCKET_BUF_LEN - buf_slice.len();

            // This unsafe is OK because we know what is being written to the buffer
            let buf = unsafe { crate::str::from_utf8_unchecked(&buf[..len]) };
            f.pad(buf)
        }
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for SocketAddrV4 {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(self, fmt)
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Display for SocketAddrV6 {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        // Fast path: if there's no alignment stuff, write to the output
        // buffer directly
        if f.precision().is_none() && f.width().is_none() {
            match self.scope_id() {
                0 => write!(f, "[{}]:{}", self.ip(), self.port()),
                scope_id => write!(f, "[{}%{}]:{}", self.ip(), scope_id, self.port()),
            }
        } else {
            const IPV6_SOCKET_BUF_LEN: usize = (4 * 8)  // The address
            + 7  // The colon separators
            + 2  // The brackets
            + 1 + 10 // The scope id
            + 1 + 5; // The port

            let mut buf = [0; IPV6_SOCKET_BUF_LEN];
            let mut buf_slice = &mut buf[..];

            match self.scope_id() {
                0 => write!(buf_slice, "[{}]:{}", self.ip(), self.port()),
                scope_id => write!(buf_slice, "[{}%{}]:{}", self.ip(), scope_id, self.port()),
            }
            // Unwrap is fine because writing to a sufficiently-sized
            // buffer is infallible
            .unwrap();
            let len = IPV6_SOCKET_BUF_LEN - buf_slice.len();

            // This unsafe is OK because we know what is being written to the buffer
            let buf = unsafe { crate::str::from_utf8_unchecked(&buf[..len]) };
            f.pad(buf)
        }
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for SocketAddrV6 {
    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(self, fmt)
    }
}

#[stable(feature = "socketaddr_ordering", since = "1.45.0")]
impl PartialOrd for SocketAddrV4 {
    fn partial_cmp(&self, other: &SocketAddrV4) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

#[stable(feature = "socketaddr_ordering", since = "1.45.0")]
impl PartialOrd for SocketAddrV6 {
    fn partial_cmp(&self, other: &SocketAddrV6) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

#[stable(feature = "socketaddr_ordering", since = "1.45.0")]
impl Ord for SocketAddrV4 {
    fn cmp(&self, other: &SocketAddrV4) -> Ordering {
        self.ip().cmp(other.ip()).then(self.port().cmp(&other.port()))
    }
}

#[stable(feature = "socketaddr_ordering", since = "1.45.0")]
impl Ord for SocketAddrV6 {
    fn cmp(&self, other: &SocketAddrV6) -> Ordering {
        self.ip().cmp(other.ip()).then(self.port().cmp(&other.port()))
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl hash::Hash for SocketAddrV4 {
    fn hash<H: hash::Hasher>(&self, s: &mut H) {
        (self.port, self.ip).hash(s)
    }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl hash::Hash for SocketAddrV6 {
    fn hash<H: hash::Hasher>(&self, s: &mut H) {
        (self.port, &self.ip, self.flowinfo, self.scope_id).hash(s)
    }
}

/// A trait for objects which can be converted or resolved to one or more
/// [`SocketAddr`] values.
///
/// This trait is used for generic address resolution when constructing network
/// objects. By default it is implemented for the following types:
///
///  * [`SocketAddr`]: [`to_socket_addrs`] is the identity function.
///
///  * [`SocketAddrV4`], [`SocketAddrV6`], <code>([IpAddr], [u16])</code>,
///    <code>([Ipv4Addr], [u16])</code>, <code>([Ipv6Addr], [u16])</code>:
///    [`to_socket_addrs`] constructs a [`SocketAddr`] trivially.
///
///  * <code>(&[str], [u16])</code>: <code>&[str]</code> should be either a string representation
///    of an [`IpAddr`] address as expected by [`FromStr`] implementation or a host
///    name. [`u16`] is the port number.
///
///  * <code>&[str]</code>: the string should be either a string representation of a
///    [`SocketAddr`] as expected by its [`FromStr`] implementation or a string like
///    `<host_name>:<port>` pair where `<port>` is a [`u16`] value.
///
/// This trait allows constructing network objects like [`TcpStream`] or
/// [`UdpSocket`] easily with values of various types for the bind/connection
/// address. It is needed because sometimes one type is more appropriate than
/// the other: for simple uses a string like `"localhost:12345"` is much nicer
/// than manual construction of the corresponding [`SocketAddr`], but sometimes
/// [`SocketAddr`] value is *the* main source of the address, and converting it to
/// some other type (e.g., a string) just for it to be converted back to
/// [`SocketAddr`] in constructor methods is pointless.
///
/// Addresses returned by the operating system that are not IP addresses are
/// silently ignored.
///
/// [`FromStr`]: crate::str::FromStr "std::str::FromStr"
/// [`TcpStream`]: crate::net::TcpStream "net::TcpStream"
/// [`to_socket_addrs`]: ToSocketAddrs::to_socket_addrs
/// [`UdpSocket`]: crate::net::UdpSocket "net::UdpSocket"
///
/// # Examples
///
/// Creating a [`SocketAddr`] iterator that yields one item:
///
/// ```
/// use std::net::{ToSocketAddrs, SocketAddr};
///
/// let addr = SocketAddr::from(([127, 0, 0, 1], 443));
/// let mut addrs_iter = addr.to_socket_addrs().unwrap();
///
/// assert_eq!(Some(addr), addrs_iter.next());
/// assert!(addrs_iter.next().is_none());
/// ```
///
/// Creating a [`SocketAddr`] iterator from a hostname:
///
/// ```no_run
/// use std::net::{SocketAddr, ToSocketAddrs};
///
/// // assuming 'localhost' resolves to 127.0.0.1
/// let mut addrs_iter = "localhost:443".to_socket_addrs().unwrap();
/// assert_eq!(addrs_iter.next(), Some(SocketAddr::from(([127, 0, 0, 1], 443))));
/// assert!(addrs_iter.next().is_none());
///
/// // assuming 'foo' does not resolve
/// assert!("foo:443".to_socket_addrs().is_err());
/// ```
///
/// Creating a [`SocketAddr`] iterator that yields multiple items:
///
/// ```
/// use std::net::{SocketAddr, ToSocketAddrs};
///
/// let addr1 = SocketAddr::from(([0, 0, 0, 0], 80));
/// let addr2 = SocketAddr::from(([127, 0, 0, 1], 443));
/// let addrs = vec![addr1, addr2];
///
/// let mut addrs_iter = (&addrs[..]).to_socket_addrs().unwrap();
///
/// assert_eq!(Some(addr1), addrs_iter.next());
/// assert_eq!(Some(addr2), addrs_iter.next());
/// assert!(addrs_iter.next().is_none());
/// ```
///
/// Attempting to create a [`SocketAddr`] iterator from an improperly formatted
/// socket address `&str` (missing the port):
///
/// ```
/// use std::io;
/// use std::net::ToSocketAddrs;
///
/// let err = "127.0.0.1".to_socket_addrs().unwrap_err();
/// assert_eq!(err.kind(), io::ErrorKind::InvalidInput);
/// ```
///
/// [`TcpStream::connect`] is an example of an function that utilizes
/// `ToSocketAddrs` as a trait bound on its parameter in order to accept
/// different types:
///
/// ```no_run
/// use std::net::{TcpStream, Ipv4Addr};
///
/// let stream = TcpStream::connect(("127.0.0.1", 443));
/// // or
/// let stream = TcpStream::connect("127.0.0.1:443");
/// // or
/// let stream = TcpStream::connect((Ipv4Addr::new(127, 0, 0, 1), 443));
/// ```
///
/// [`TcpStream::connect`]: crate::net::TcpStream::connect
#[stable(feature = "rust1", since = "1.0.0")]
pub trait ToSocketAddrs {
    /// Returned iterator over socket addresses which this type may correspond
    /// to.
    #[stable(feature = "rust1", since = "1.0.0")]
    type Iter: Iterator<Item = SocketAddr>;

    /// Converts this object to an iterator of resolved [`SocketAddr`]s.
    ///
    /// The returned iterator might not actually yield any values depending on the
    /// outcome of any resolution performed.
    ///
    /// Note that this function may block the current thread while resolution is
    /// performed.
    #[stable(feature = "rust1", since = "1.0.0")]
    fn to_socket_addrs(&self) -> io::Result<Self::Iter>;
}

#[stable(feature = "rust1", since = "1.0.0")]
impl ToSocketAddrs for SocketAddr {
    type Iter = option::IntoIter<SocketAddr>;
    fn to_socket_addrs(&self) -> io::Result<option::IntoIter<SocketAddr>> {
        Ok(Some(*self).into_iter())
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl ToSocketAddrs for SocketAddrV4 {
    type Iter = option::IntoIter<SocketAddr>;
    fn to_socket_addrs(&self) -> io::Result<option::IntoIter<SocketAddr>> {
        SocketAddr::V4(*self).to_socket_addrs()
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl ToSocketAddrs for SocketAddrV6 {
    type Iter = option::IntoIter<SocketAddr>;
    fn to_socket_addrs(&self) -> io::Result<option::IntoIter<SocketAddr>> {
        SocketAddr::V6(*self).to_socket_addrs()
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl ToSocketAddrs for (IpAddr, u16) {
    type Iter = option::IntoIter<SocketAddr>;
    fn to_socket_addrs(&self) -> io::Result<option::IntoIter<SocketAddr>> {
        let (ip, port) = *self;
        match ip {
            IpAddr::V4(ref a) => (*a, port).to_socket_addrs(),
            IpAddr::V6(ref a) => (*a, port).to_socket_addrs(),
        }
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl ToSocketAddrs for (Ipv4Addr, u16) {
    type Iter = option::IntoIter<SocketAddr>;
    fn to_socket_addrs(&self) -> io::Result<option::IntoIter<SocketAddr>> {
        let (ip, port) = *self;
        SocketAddrV4::new(ip, port).to_socket_addrs()
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl ToSocketAddrs for (Ipv6Addr, u16) {
    type Iter = option::IntoIter<SocketAddr>;
    fn to_socket_addrs(&self) -> io::Result<option::IntoIter<SocketAddr>> {
        let (ip, port) = *self;
        SocketAddrV6::new(ip, port, 0, 0).to_socket_addrs()
    }
}

fn resolve_socket_addr(lh: LookupHost) -> io::Result<vec::IntoIter<SocketAddr>> {
    let p = lh.port();
    let v: Vec<_> = lh
        .map(|mut a| {
            a.set_port(p);
            a
        })
        .collect();
    Ok(v.into_iter())
}

#[stable(feature = "rust1", since = "1.0.0")]
impl ToSocketAddrs for (&str, u16) {
    type Iter = vec::IntoIter<SocketAddr>;
    fn to_socket_addrs(&self) -> io::Result<vec::IntoIter<SocketAddr>> {
        let (host, port) = *self;

        // try to parse the host as a regular IP address first
        if let Ok(addr) = host.parse::<Ipv4Addr>() {
            let addr = SocketAddrV4::new(addr, port);
            return Ok(vec![SocketAddr::V4(addr)].into_iter());
        }
        if let Ok(addr) = host.parse::<Ipv6Addr>() {
            let addr = SocketAddrV6::new(addr, port, 0, 0);
            return Ok(vec![SocketAddr::V6(addr)].into_iter());
        }

        resolve_socket_addr((host, port).try_into()?)
    }
}

#[stable(feature = "string_u16_to_socket_addrs", since = "1.46.0")]
impl ToSocketAddrs for (String, u16) {
    type Iter = vec::IntoIter<SocketAddr>;
    fn to_socket_addrs(&self) -> io::Result<vec::IntoIter<SocketAddr>> {
        (&*self.0, self.1).to_socket_addrs()
    }
}

// accepts strings like 'localhost:12345'
#[stable(feature = "rust1", since = "1.0.0")]
impl ToSocketAddrs for str {
    type Iter = vec::IntoIter<SocketAddr>;
    fn to_socket_addrs(&self) -> io::Result<vec::IntoIter<SocketAddr>> {
        // try to parse as a regular SocketAddr first
        if let Ok(addr) = self.parse() {
            return Ok(vec![addr].into_iter());
        }

        resolve_socket_addr(self.try_into()?)
    }
}

#[stable(feature = "slice_to_socket_addrs", since = "1.8.0")]
impl<'a> ToSocketAddrs for &'a [SocketAddr] {
    type Iter = iter::Cloned<slice::Iter<'a, SocketAddr>>;

    fn to_socket_addrs(&self) -> io::Result<Self::Iter> {
        Ok(self.iter().cloned())
    }
}

#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ToSocketAddrs + ?Sized> ToSocketAddrs for &T {
    type Iter = T::Iter;
    fn to_socket_addrs(&self) -> io::Result<T::Iter> {
        (**self).to_socket_addrs()
    }
}

#[stable(feature = "string_to_socket_addrs", since = "1.16.0")]
impl ToSocketAddrs for String {
    type Iter = vec::IntoIter<SocketAddr>;
    fn to_socket_addrs(&self) -> io::Result<vec::IntoIter<SocketAddr>> {
        (&**self).to_socket_addrs()
    }
}