summaryrefslogtreecommitdiff
path: root/src/socket_base.cpp
blob: 5aed0dcbb0952356e6bb12d189d43244af6f42a1 (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
/*
    Copyright (c) 2009-2012 250bpm s.r.o.
    Copyright (c) 2007-2009 iMatix Corporation
    Copyright (c) 2011 VMware, Inc.
    Copyright (c) 2007-2011 Other contributors as noted in the AUTHORS file

    This file is part of Crossroads I/O project.

    Crossroads I/O is free software; you can redistribute it and/or modify it
    under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    Crossroads is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <new>
#include <string>
#include <algorithm>

#include "platform.hpp"

#if defined XS_HAVE_WINDOWS
#include "windows.hpp"
#if defined _MSC_VER
#include <intrin.h>
#endif
#else
#include <unistd.h>
#endif
#ifdef XS_HAVE_OPENPGM
#include "pgm_socket.hpp"
#endif

#include "socket_base.hpp"
#include "tcp_listener.hpp"
#include "ipc_listener.hpp"
#include "tcp_connecter.hpp"
#include "ipc_connecter.hpp"
#include "io_thread.hpp"
#include "session_base.hpp"
#include "config.hpp"
#include "pipe.hpp"
#include "err.hpp"
#include "ctx.hpp"
#include "platform.hpp"
#include "likely.hpp"
#include "msg.hpp"

#include "pair.hpp"
#include "pub.hpp"
#include "sub.hpp"
#include "req.hpp"
#include "rep.hpp"
#include "pull.hpp"
#include "push.hpp"
#include "xreq.hpp"
#include "xrep.hpp"
#include "xpub.hpp"
#include "xsub.hpp"
#include "surveyor.hpp"
#include "xsurveyor.hpp"
#include "respondent.hpp"
#include "xrespondent.hpp"

bool xs::socket_base_t::check_tag ()
{
    return tag == 0xbaddecaf;
}

xs::socket_base_t *xs::socket_base_t::create (int type_, class ctx_t *parent_,
    uint32_t tid_, int sid_)
{
    socket_base_t *s = NULL;
    switch (type_) {

    case XS_PAIR:
        s = new (std::nothrow) pair_t (parent_, tid_, sid_);
        break;
    case XS_PUB:
        s = new (std::nothrow) pub_t (parent_, tid_, sid_);
        break;
    case XS_SUB:
        s = new (std::nothrow) sub_t (parent_, tid_, sid_);
        break;
    case XS_REQ:
        s = new (std::nothrow) req_t (parent_, tid_, sid_);
        break;
    case XS_REP:
        s = new (std::nothrow) rep_t (parent_, tid_, sid_);
        break;
    case XS_XREQ:
        s = new (std::nothrow) xreq_t (parent_, tid_, sid_);
        break;
    case XS_XREP:
        s = new (std::nothrow) xrep_t (parent_, tid_, sid_);
        break;     
    case XS_PULL:
        s = new (std::nothrow) pull_t (parent_, tid_, sid_);
        break;
    case XS_PUSH:
        s = new (std::nothrow) push_t (parent_, tid_, sid_);
        break;
    case XS_XPUB:
        s = new (std::nothrow) xpub_t (parent_, tid_, sid_);
        break;
    case XS_XSUB:
        s = new (std::nothrow) xsub_t (parent_, tid_, sid_);
        break;
    case XS_SURVEYOR:
        s = new (std::nothrow) surveyor_t (parent_, tid_, sid_);
        break;
    case XS_XSURVEYOR:
        s = new (std::nothrow) xsurveyor_t (parent_, tid_, sid_);
        break;
    case XS_RESPONDENT:
        s = new (std::nothrow) respondent_t (parent_, tid_, sid_);
        break;
    case XS_XRESPONDENT:
        s = new (std::nothrow) xrespondent_t (parent_, tid_, sid_);
        break;
    default:
        errno = EINVAL;
        return NULL;
    }
    alloc_assert (s);
    int rc = s->init ();
    if (rc != 0)
        return NULL;
    return s;
}

xs::socket_base_t::socket_base_t (ctx_t *parent_, uint32_t tid_, int sid_) :
    own_t (parent_, tid_),
    tag (0xbaddecaf),
    ctx_terminated (false),
    destroyed (false),
    initialised (false),
    last_tsc (0),
    ticks (0),
    rcvmore (false)
{
    options.socket_id = sid_;
}

int xs::socket_base_t::init ()
{
    xs_assert (!initialised);
    int rc = mailbox_init (&mailbox);
    if (rc != 0) {
        destroyed = true;
        delete this;
        return -1;
    }
    initialised = true;
    return 0;
}

xs::socket_base_t::~socket_base_t ()
{
    xs_assert (destroyed);

    if (initialised)
        mailbox_close (&mailbox);
}

xs::mailbox_t *xs::socket_base_t::get_mailbox ()
{
    return &mailbox;
}

void xs::socket_base_t::stop ()
{
    //  Called by ctx when it is terminated (xs_term).
    //  'stop' command is sent from the threads that called xs_term to
    //  the thread owning the socket. This way, blocking call in the
    //  owner thread can be interrupted.
    send_stop ();
}

int xs::socket_base_t::parse_uri (const char *uri_,
    std::string &protocol_, std::string &address_)
{
    xs_assert (uri_ != NULL);

    std::string uri (uri_);
    std::string::size_type pos = uri.find ("://");
    if (pos == std::string::npos) {
        errno = EINVAL;
        return -1;
    }
    protocol_ = uri.substr (0, pos);
    address_ = uri.substr (pos + 3);
    if (protocol_.empty () || address_.empty ()) {
        errno = EINVAL;
        return -1;
    }
    return 0;
}

int xs::socket_base_t::check_protocol (const std::string &protocol_)
{
    //  First check out whether the protcol is something we are aware of.
    if (protocol_ != "inproc" && protocol_ != "ipc" && protocol_ != "tcp" &&
          protocol_ != "pgm" && protocol_ != "epgm") {
        errno = EPROTONOSUPPORT;
        return -1;
    }

    //  If Crossroads is not compiled with OpenPGM, pgm and epgm transports
    //  are not avaialble.
#if !defined XS_HAVE_OPENPGM
    if (protocol_ == "pgm" || protocol_ == "epgm") {
        errno = EPROTONOSUPPORT;
        return -1;
    }
#endif

    //  IPC transport is not available on Windows and OpenVMS.
#if defined XS_HAVE_WINDOWS || defined XS_HAVE_OPENVMS
    if (protocol_ == "ipc") {
        //  Unknown protocol.
        errno = EPROTONOSUPPORT;
        return -1;
    }
#endif

    //  Check whether socket type and transport protocol match.
    //  Specifically, multicast protocols can't be combined with
    //  bi-directional messaging patterns (socket types).
    if ((protocol_ == "pgm" || protocol_ == "epgm") &&
          options.type != XS_PUB && options.type != XS_SUB &&
          options.type != XS_XPUB && options.type != XS_XSUB) {
        errno = ENOCOMPATPROTO;
        return -1;
    }

    //  Protocol is available.
    return 0;
}

void xs::socket_base_t::attach_pipe (pipe_t *pipe_, bool icanhasall_)
{
    //  First, register the pipe so that we can terminate it later on.
    pipe_->set_event_sink (this);
    pipes.push_back (pipe_);
    
    //  Let the derived socket type know about new pipe.
    xattach_pipe (pipe_, icanhasall_);

    //  If the socket is already being closed, ask any new pipes to terminate
    //  straight away.
    if (is_terminating ()) {
        register_term_acks (1);
        pipe_->terminate (false);
    }
}

int xs::socket_base_t::setsockopt (int option_, const void *optval_,
    size_t optvallen_)
{
    if (unlikely (ctx_terminated)) {
        errno = ETERM;
        return -1;
    }

    //  First, check whether specific socket type overloads the option.
    int rc = xsetsockopt (option_, optval_, optvallen_);
    if (rc == 0 || errno != EINVAL)
        return rc;

    //  If the socket type doesn't support the option, pass it to
    //  the generic option parser.
    rc = options.setsockopt (option_, optval_, optvallen_);
    return rc;
}

int xs::socket_base_t::getsockopt (int option_, void *optval_,
    size_t *optvallen_)
{
    if (unlikely (ctx_terminated)) {
        errno = ETERM;
        return -1;
    }

    if (option_ == XS_RCVMORE) {
        if (*optvallen_ < sizeof (int)) {
            errno = EINVAL;
            return -1;
        }
        *((int*) optval_) = rcvmore ? 1 : 0;
        *optvallen_ = sizeof (int);
        return 0;
    }

    if (option_ == XS_FD) {
        if (*optvallen_ < sizeof (fd_t)) {
            errno = EINVAL;
            return -1;
        }
        *((fd_t*) optval_) = mailbox_fd (&mailbox);
        *optvallen_ = sizeof (fd_t);
        return 0;
    }

    if (option_ == XS_EVENTS) {
        if (*optvallen_ < sizeof (int)) {
            errno = EINVAL;
            return -1;
        }
        int rc = process_commands (0, false);
        if (rc != 0 && (errno == EINTR || errno == ETERM))
            return -1;
        errno_assert (rc == 0);
        *((int*) optval_) = 0;
        if (has_out ())
            *((int*) optval_) |= XS_POLLOUT;
        if (has_in ())
            *((int*) optval_) |= XS_POLLIN;
        *optvallen_ = sizeof (int);
        return 0;
    }

    return options.getsockopt (option_, optval_, optvallen_);
}

int xs::socket_base_t::bind (const char *addr_)
{
    if (unlikely (ctx_terminated)) {
        errno = ETERM;
        return -1;
    }

    //  Parse addr_ string.
    std::string protocol;
    std::string address;
    int rc = parse_uri (addr_, protocol, address);
    if (rc != 0)
        return -1;

    rc = check_protocol (protocol);
    if (rc != 0)
        return -1;

    if (protocol == "inproc") {
        endpoint_t endpoint = {this, options};
        rc = register_endpoint (addr_, endpoint);
        if (rc != 0)
            return -1;

        //  Endpoint IDs for inproc transport are not implemented at the
        //  moment. Thus we return 0 to the user.
        return 0;
    }

    if (protocol == "pgm" || protocol == "epgm") {

        //  For convenience's sake, bind can be used interchageable with
        //  connect for PGM and EPGM transports.
        rc = connect (addr_);
        return rc;
    }

    //  Remaining trasnports require to be run in an I/O thread, so at this
    //  point we'll choose one.
    io_thread_t *thread = choose_io_thread (options.affinity);
    xs_assert (thread);

    if (protocol == "tcp") {
        tcp_listener_t *listener = new (std::nothrow) tcp_listener_t (
            thread, this, options);
        alloc_assert (listener);
        rc = listener->set_address (address.c_str ());
        if (rc != 0) {
            delete listener;
            return -1;
        }
        launch_child (listener);
        return add_endpoint (listener);
    }

#if !defined XS_HAVE_WINDOWS && !defined XS_HAVE_OPENVMS
    if (protocol == "ipc") {
        ipc_listener_t *listener = new (std::nothrow) ipc_listener_t (
            thread, this, options);
        alloc_assert (listener);
        rc = listener->set_address (address.c_str ());
        if (rc != 0) {
            delete listener;
            return -1;
        }
        launch_child (listener);
        return add_endpoint (listener);
    }
#endif

    xs_assert (false);
    return -1;
}

int xs::socket_base_t::connect (const char *addr_)
{
    if (unlikely (ctx_terminated)) {
        errno = ETERM;
        return -1;
    }

    //  Parse addr_ string.
    std::string protocol;
    std::string address;
    int rc = parse_uri (addr_, protocol, address);
    if (rc != 0)
        return -1;

    rc = check_protocol (protocol);
    if (rc != 0)
        return -1;

    if (protocol == "inproc") {

        //  TODO: inproc connect is specific with respect to creating pipes
        //  as there's no 'reconnect' functionality implemented. Once that
        //  is in place we should follow generic pipe creation algorithm.

        //  Find the peer endpoint.
        endpoint_t peer = find_endpoint (addr_);
        if (!peer.socket)
            return -1;

        // The total HWM for an inproc connection should be the sum of
        // the binder's HWM and the connector's HWM.
        int  sndhwm;
        int  rcvhwm;
        if (options.sndhwm == 0 || peer.options.rcvhwm == 0)
            sndhwm = 0;
        else
            sndhwm = options.sndhwm + peer.options.rcvhwm;
        if (options.rcvhwm == 0 || peer.options.sndhwm == 0)
            rcvhwm = 0;
        else
            rcvhwm = options.rcvhwm + peer.options.sndhwm;

        //  Create a bi-directional pipe to connect the peers.
        object_t *parents [2] = {this, peer.socket};
        pipe_t *ppair [2] = {NULL, NULL};
        int hwms [2] = {sndhwm, rcvhwm};
        bool delays [2] = {options.delay_on_disconnect, options.delay_on_close};
        rc = pipepair (parents, ppair, hwms, delays, options.protocol);
        errno_assert (rc == 0);

        //  Attach local end of the pipe to this socket object.
        attach_pipe (ppair [0]);

        //  If required, send the identity of the local socket to the peer.
        if (options.send_identity) {
            msg_t id;
            rc = id.init_size (options.identity_size);
            errno_assert (rc == 0);
            memcpy (id.data (), options.identity, options.identity_size);
            id.set_flags (msg_t::identity);
            bool written = ppair [0]->write (&id);
            xs_assert (written);
            pipes [0]->flush ();
        }

        //  If required, send the identity of the peer to the local socket.
        if (peer.options.send_identity) {
            msg_t id;
            rc = id.init_size (peer.options.identity_size);
            errno_assert (rc == 0);
            memcpy (id.data (), peer.options.identity,
                peer.options.identity_size);
            id.set_flags (msg_t::identity);
            bool written = ppair [1]->write (&id);
            xs_assert (written);
            ppair [1]->flush ();
        }

        //  Attach remote end of the pipe to the peer socket. Note that peer's
        //  seqnum was incremented in find_endpoint function. We don't need it
        //  increased here.
        send_bind (peer.socket, ppair [1], false);

        //  Inproc endpoints are not yet implemented thus we return 0.
        return 0;
    }

    //  Choose the I/O thread to run the session in.
    io_thread_t *thread = choose_io_thread (options.affinity);
    xs_assert (thread);

    if (protocol == "tcp") {
        tcp_connecter_t connecter (thread, NULL, options, false);
        int rc = connecter.set_address (address.c_str());
        if (rc != 0) {
            return -1;
        }
    }

#if !defined XS_HAVE_WINDOWS && !defined XS_HAVE_OPENVMS
    if (protocol == "ipc") {
        ipc_connecter_t connecter (thread, NULL, options, false);
        int rc = connecter.set_address (address.c_str());
        if (rc != 0) {
            return -1;
        }
    }
#endif

#ifdef XS_HAVE_OPENPGM
    if (protocol == "pgm" || protocol == "epgm") {
        struct pgm_addrinfo_t *res = NULL;
        uint16_t port_number = 0;
        int rc = pgm_socket_t::init_address(address.c_str(), &res, &port_number);
        if (res != NULL)
            pgm_freeaddrinfo (res);
        if (rc != 0 || port_number == 0)
            return -1;
    }
#endif

    //  Create session.
    session_base_t *session = session_base_t::create (thread, true, this,
        options, protocol.c_str (), address.c_str ());
    errno_assert (session);

    //  Create a bi-directional pipe.
    object_t *parents [2] = {this, session};
    pipe_t *ppair [2] = {NULL, NULL};
    int hwms [2] = {options.sndhwm, options.rcvhwm};
    bool delays [2] = {options.delay_on_disconnect, options.delay_on_close};
    rc = pipepair (parents, ppair, hwms, delays, options.protocol);
    errno_assert (rc == 0);

    // PGM does not support subscription forwarding; ask for all data to be
    // sent to this pipe.
    bool icanhasall = false;
    if (protocol == "pgm" || protocol == "epgm")
        icanhasall = true;

    //  Attach local end of the pipe to the socket object.
    attach_pipe (ppair [0], icanhasall);

    //  Attach remote end of the pipe to the session object later on.
    session->attach_pipe (ppair [1]);

    //  Activate the session. Make it a child of this socket.
    launch_child (session);
    return add_endpoint (session);
}

int xs::socket_base_t::shutdown (int how_)
{
    //  Check whether the library haven't been shut down yet.
    if (unlikely (ctx_terminated)) {
        errno = ETERM;
        return -1;
    }

    //  Endpoint ID means 'shutdown not implemented'.
    if (how_ <= 0) {
        errno = ENOTSUP;
        return -1;
    }

    //  Find the endpoint corresponding to the ID.
    endpoints_t::iterator it = endpoints.find (how_);
    if (it == endpoints.end ()) {
        errno = EINVAL;
        return -1;
    }

    process_term_req (it->second);
    endpoints.erase (it);
    return 0;
}

int xs::socket_base_t::send (msg_t *msg_, int flags_)
{
    //  Check whether the library haven't been shut down yet.
    if (unlikely (ctx_terminated)) {
        errno = ETERM;
        return -1;
    }

    //  Check whether message passed to the function is valid.
    if (unlikely (!msg_ || !msg_->check ())) {
        errno = EFAULT;
        return -1;
    }

    //  Process pending commands, if any.
    int rc = process_commands (0, true);
    if (unlikely (rc != 0))
        return -1;

    //  Clear any user-visible flags that are set on the message.
    msg_->reset_flags (msg_t::more);

    //  At this point we impose the flags on the message.
    if (flags_ & XS_SNDMORE)
        msg_->set_flags (msg_t::more);

    //  Try to send the message.
    rc = xsend (msg_, flags_);
    if (rc == 0)
        return 0;
    if (unlikely (errno != EAGAIN))
        return -1;

    int timeout = sndtimeo ();
    if (flags_ & XS_DONTWAIT || timeout == 0) {

        //  It looks like pipe is full. However, previous process_commands may
        //  have done nothing because of the throttling. Thus, let's give it
        //  last try and force commands to be processed. Then try to re-send
        //  the message.
        rc = process_commands (0, false);
        if (unlikely (rc != 0))
            return -1;
        return xsend (msg_, flags_);
    }

    //  Compute the time when the timeout should occur.
    //  If the timeout is infite, don't care. 
    uint64_t end = timeout < 0 ? 0 : (clock.now_ms () + timeout);

    //  Oops, we couldn't send the message. Wait for the next
    //  command, process it and try to send the message again.
    //  If timeout is reached in the meantime, return EAGAIN.
    while (true) {
        if (unlikely (process_commands (timeout, false) != 0))
            return -1;
        rc = xsend (msg_, flags_);
        if (rc == 0)
            break;
        if (unlikely (errno != EAGAIN))
            return -1;
        if (timeout > 0) {
            timeout = (int) (end - clock.now_ms ());
            if (timeout <= 0) {
                errno = EAGAIN;
                return -1;
            }
        }
    }

    return 0;
}

int xs::socket_base_t::recv (msg_t *msg_, int flags_)
{
    //  Check whether the library haven't been shut down yet.
    if (unlikely (ctx_terminated)) {
        errno = ETERM;
        return -1;
    }

    //  Check whether message passed to the function is valid.
    if (unlikely (!msg_ || !msg_->check ())) {
        errno = EFAULT;
        return -1;
    }

    //  Get the message.
    int rc = xrecv (msg_, flags_);
    if (unlikely (rc != 0 && errno != EAGAIN))
        return -1;

    //  Once every inbound_poll_rate messages check for signals and process
    //  incoming commands. This happens only if we are not polling altogether
    //  because there are messages available all the time. If poll occurs,
    //  ticks is set to zero and thus we avoid this code.
    //
    //  Note that 'recv' uses different command throttling algorithm (the one
    //  described above) from the one used by 'send'. This is because counting
    //  ticks is more efficient than doing RDTSC all the time.
    if (++ticks == inbound_poll_rate) {
        if (unlikely (process_commands (0, false) != 0))
            return -1;
        ticks = 0;
    }

    //  If we have the message, return immediately.
    if (rc == 0) {
        extract_flags (msg_);
        return 0;
    }

    //  If the message cannot be fetched immediately, there are two scenarios.
    //  For non-blocking recv, commands are processed in case there's an
    //  activate_reader command already waiting int a command pipe.
    //  If it's not, return EAGAIN.
    int timeout = rcvtimeo ();
    if (flags_ & XS_DONTWAIT || timeout == 0) {
        if (unlikely (process_commands (0, false) != 0))
            return -1;
        ticks = 0;

        rc = xrecv (msg_, flags_);
        if (rc < 0)
            return rc;

        extract_flags (msg_);
        return 0;
    }

    //  Compute the time when the timeout should occur.
    //  If the timeout is infite, don't care. 
    uint64_t end = timeout < 0 ? 0 : (clock.now_ms () + timeout);

    //  In blocking scenario, commands are processed over and over again until
    //  we are able to fetch a message.
    bool block = (ticks != 0);
    while (true) {
        if (unlikely (process_commands (block ? timeout : 0, false) != 0))
            return -1;
        rc = xrecv (msg_, flags_);
        if (rc == 0) {
            ticks = 0;
            break;
        }
        if (unlikely (errno != EAGAIN))
            return -1;
        block = true;
        if (timeout > 0) {
            timeout = (int) (end - clock.now_ms ());
            if (timeout <= 0) {
                errno = EAGAIN;
                return -1;
            }
        }
    }

    extract_flags (msg_);
    return 0;
}

int xs::socket_base_t::close ()
{
    //  Mark the socket as dead.
    tag = 0xdeadbeef;

    //  Transfer the ownership of the socket from this application thread
    //  to the reaper thread which will take care of the rest of shutdown
    //  process.
    send_reap (this);

    return 0;
}

bool xs::socket_base_t::has_in ()
{
    bool ret = xhas_in ();
    return ret;
}

bool xs::socket_base_t::has_out ()
{
    bool ret = xhas_out ();
    return ret;
}

void xs::socket_base_t::start_reaping (io_thread_t *io_thread_)
{
    //  Plug the socket to the reaper thread.
    io_thread = io_thread_;
    handle = io_thread->add_fd (mailbox_fd (&mailbox), this);
    io_thread->set_pollin (handle);

    //  Initialise the termination and check whether it can be deallocated
    //  immediately.
    terminate ();
    check_destroy ();
}

int xs::socket_base_t::process_commands (int timeout_, bool throttle_)
{
    int rc;
    command_t cmd;
    if (timeout_ != 0) {

        //  If we are asked to wait, simply ask mailbox to wait.
        rc = mailbox_recv (&mailbox, &cmd, timeout_);
    }
    else {

        //  If we are asked not to wait, check whether we haven't processed
        //  commands recently, so that we can throttle the new commands.
        //  This doesn't apply when the throttling is turned off.
        if (throttle_) {

            //  Get the CPU's tick counter. If 0, the counter is not available.
            uint64_t tsc = xs::clock_t::rdtsc ();

            //  Optimised version of command processing - it doesn't have to
            //  check for incoming commands each time. It does so only if
            //  certain time elapsed since last command processing. Command
            //  delay varies depending on CPU speed: With max_command_delay set
            //  to 3000000 it's ~1ms on 3GHz CPU, ~2ms on 1.5GHz CPU etc.
            //  The optimisation makes sense only on platforms where getting 
            //  timestamp is a very cheap operation (tens of nanoseconds).
            if (tsc) {

                //  Check whether TSC haven't jumped backwards (in case of
                //  migration between CPU cores) and whether certain time have
                //  elapsed since last command processing. If it didn't do
                //  nothing.
                if (tsc >= last_tsc && tsc - last_tsc <= max_command_delay)
                    return 0;
                last_tsc = tsc;
            }
        }

        //  Check whether there are any commands pending for this thread.
        rc = mailbox_recv (&mailbox, &cmd, 0);
    }

    //  Process all the commands available at the moment.
    while (true) {
        if (rc == -1 && errno == EAGAIN)
            break;
        if (rc == -1 && errno == EINTR)
            return -1;
        errno_assert (rc == 0);
        cmd.destination->process_command (cmd);
        rc = mailbox_recv (&mailbox, &cmd, 0);
     }

    if (ctx_terminated) {
        errno = ETERM;
        return -1;
    }

    return 0;
}

void xs::socket_base_t::process_stop ()
{
    //  Here, someone have called xs_term while the socket was still alive.
    //  We'll remember the fact so that any blocking call is interrupted and any
    //  further attempt to use the socket will return ETERM. The user is still
    //  responsible for calling xs_close on the socket though!
    ctx_terminated = true;
}

void xs::socket_base_t::process_bind (pipe_t *pipe_)
{
    attach_pipe (pipe_);
}

void xs::socket_base_t::process_unplug ()
{
}

void xs::socket_base_t::process_term (int linger_)
{
    //  Unregister all inproc endpoints associated with this socket.
    //  Doing this we make sure that no new pipes from other sockets (inproc)
    //  will be initiated.
    unregister_endpoints (this);

    //  Ask all attached pipes to terminate.
    for (pipes_t::size_type i = 0; i != pipes.size (); ++i)
        pipes [i]->terminate (false);
    register_term_acks ((int) pipes.size ());

    //  Continue the termination process immediately.
    own_t::process_term (linger_);
}

void xs::socket_base_t::process_destroy ()
{
    destroyed = true;
}

int xs::socket_base_t::xsetsockopt (int option_, const void *optval_,
    size_t optvallen_)
{
    errno = EINVAL;
    return -1;
}

bool xs::socket_base_t::xhas_out ()
{
    return false;
}

int xs::socket_base_t::xsend (msg_t *msg_, int flags_)
{
    errno = ENOTSUP;
    return -1;
}

bool xs::socket_base_t::xhas_in ()
{
    return false;
}

int xs::socket_base_t::xrecv (msg_t *msg_, int flags_)
{
    errno = ENOTSUP;
    return -1;
}

void xs::socket_base_t::xread_activated (pipe_t *pipe_)
{
    xs_assert (false);
}
void xs::socket_base_t::xwrite_activated (pipe_t *pipe_)
{
    xs_assert (false);
}

void xs::socket_base_t::xhiccuped (pipe_t *pipe_)
{
    xs_assert (false);
}

void xs::socket_base_t::in_event (fd_t fd_)
{
    //  This function is invoked only once the socket is running in the context
    //  of the reaper thread. Process any commands from other threads/sockets
    //  that may be available at the moment. Ultimately, the socket will
    //  be destroyed.
    process_commands (0, false);
    check_destroy ();
}

void xs::socket_base_t::out_event (fd_t fd_)
{
    xs_assert (false);
}

void xs::socket_base_t::timer_event (handle_t handle_)
{
    xs_assert (false);
}

void xs::socket_base_t::check_destroy ()
{
    //  If the object was already marked as destroyed, finish the deallocation.
    if (destroyed) {

        //  Remove the socket from the reaper's I/O thread.
        io_thread->rm_fd (handle);

        //  Remove the socket from the context.
        destroy_socket (this);

        //  Notify the reaper about the fact.
        send_reaped ();

        //  Deallocate.
        own_t::process_destroy ();
    }
}

void xs::socket_base_t::read_activated (pipe_t *pipe_)
{
    xread_activated (pipe_);
}

void xs::socket_base_t::write_activated (pipe_t *pipe_)
{
    xwrite_activated (pipe_);
}

void xs::socket_base_t::hiccuped (pipe_t *pipe_)
{
    xhiccuped (pipe_);
}

void xs::socket_base_t::terminated (pipe_t *pipe_)
{
    //  Notify the specific socket type about the pipe termination.
    xterminated (pipe_);

    //  Remove the pipe from the list of attached pipes and confirm its
    //  termination if we are already shutting down.
    pipes.erase (pipe_);
    if (is_terminating ())
        unregister_term_ack ();
}

void xs::socket_base_t::extract_flags (msg_t *msg_)
{
    //  Test whether IDENTITY flag is valid for this socket type.
    //  TODO: Connection should be closed here!
    if (unlikely (msg_->flags () & msg_t::identity))
        xs_assert (options.recv_identity);
  
    //  Remove MORE flag.
    rcvmore = msg_->flags () & msg_t::more ? true : false;
}

int xs::socket_base_t::rcvtimeo ()
{
    return options.rcvtimeo;
}

int xs::socket_base_t::sndtimeo ()
{
    return options.sndtimeo;
}

uint64_t xs::socket_base_t::now_ms ()
{
    return clock.now_ms ();
}

int xs::socket_base_t::add_endpoint (own_t *endpoint_)
{
    //  Get a unique endpoint ID.
    int id = 1;
    for (endpoints_t::iterator it = endpoints.begin (); it != endpoints.end ();
          ++it, ++id)
        if (it->first != id)
            break;

    //  Remember the endpoint.
    endpoints.insert (std::make_pair (id, endpoint_));
    return id;
}