summaryrefslogtreecommitdiffstats
path: root/services/common_time/common_time_server.cpp
blob: 21e706fa0722cfb376b7409236455fe01a789782 (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
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * A service that exchanges time synchronization information between
 * a master that defines a timeline and clients that follow the timeline.
 */

#define LOG_TAG "common_time"
#include <utils/Log.h>

#include <arpa/inet.h>
#include <assert.h>
#include <fcntl.h>
#include <linux/if_ether.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <netinet/ip.h>
#include <poll.h>
#include <stdio.h>
#include <sys/eventfd.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/socket.h>

#include <common_time/local_clock.h>
#include <binder/IPCThreadState.h>
#include <binder/ProcessState.h>
#include <utils/Timers.h>

#include "common_clock_service.h"
#include "common_time_config_service.h"
#include "common_time_server.h"
#include "common_time_server_packets.h"
#include "clock_recovery.h"
#include "common_clock.h"

#define MAX_INT ((int)0x7FFFFFFF)

namespace android {

const char*    CommonTimeServer::kDefaultMasterElectionAddr = "255.255.255.255";
const uint16_t CommonTimeServer::kDefaultMasterElectionPort = 8886;
const uint64_t CommonTimeServer::kDefaultSyncGroupID = 1;
const uint8_t  CommonTimeServer::kDefaultMasterPriority = 1;
const uint32_t CommonTimeServer::kDefaultMasterAnnounceIntervalMs = 10000;
const uint32_t CommonTimeServer::kDefaultSyncRequestIntervalMs = 1000;
const uint32_t CommonTimeServer::kDefaultPanicThresholdUsec = 50000;
const bool     CommonTimeServer::kDefaultAutoDisable = true;
const int      CommonTimeServer::kSetupRetryTimeoutMs = 30000;
const int64_t  CommonTimeServer::kNoGoodDataPanicThresholdUsec = 600000000ll;
const uint32_t CommonTimeServer::kRTTDiscardPanicThreshMultiplier = 5;

// timeout value representing an infinite timeout
const int CommonTimeServer::kInfiniteTimeout = -1;

/*** Initial state constants ***/

// number of WhoIsMaster attempts sent before giving up
const int CommonTimeServer::kInitial_NumWhoIsMasterRetries = 6;

// timeout used when waiting for a response to a WhoIsMaster request
const int CommonTimeServer::kInitial_WhoIsMasterTimeoutMs = 500;

/*** Client state constants ***/

// number of sync requests that can fail before a client assumes its master
// is dead
const int CommonTimeServer::kClient_NumSyncRequestRetries = 10;

/*** Master state constants ***/

/*** Ronin state constants ***/

// number of WhoIsMaster attempts sent before declaring ourselves master
const int CommonTimeServer::kRonin_NumWhoIsMasterRetries = 20;

// timeout used when waiting for a response to a WhoIsMaster request
const int CommonTimeServer::kRonin_WhoIsMasterTimeoutMs = 500;

/*** WaitForElection state constants ***/

// how long do we wait for an announcement from a master before
// trying another election?
const int CommonTimeServer::kWaitForElection_TimeoutMs = 12500;

CommonTimeServer::CommonTimeServer()
    : Thread(false)
    , mState(ICommonClock::STATE_INITIAL)
    , mClockRecovery(&mLocalClock, &mCommonClock)
    , mSocket(-1)
    , mLastPacketRxLocalTime(0)
    , mTimelineID(ICommonClock::kInvalidTimelineID)
    , mClockSynced(false)
    , mCommonClockHasClients(false)
    , mStateChangeLog("Recent State Change Events", 30)
    , mElectionLog("Recent Master Election Traffic", 30)
    , mBadPktLog("Recent Bad Packet RX Info", 8)
    , mInitial_WhoIsMasterRequestTimeouts(0)
    , mClient_MasterDeviceID(0)
    , mClient_MasterDevicePriority(0)
    , mRonin_WhoIsMasterRequestTimeouts(0) {
    // zero out sync stats
    resetSyncStats();

    // Setup the master election endpoint to use the default.
    struct sockaddr_in* meep =
        reinterpret_cast<struct sockaddr_in*>(&mMasterElectionEP);
    memset(&mMasterElectionEP, 0, sizeof(mMasterElectionEP));
    inet_aton(kDefaultMasterElectionAddr, &meep->sin_addr);
    meep->sin_family = AF_INET;
    meep->sin_port   = htons(kDefaultMasterElectionPort);

    // Zero out the master endpoint.
    memset(&mMasterEP, 0, sizeof(mMasterEP));
    mMasterEPValid    = false;
    mBindIfaceValid   = false;
    setForceLowPriority(false);

    // Set all remaining configuration parameters to their defaults.
    mDeviceID                 = 0;
    mSyncGroupID              = kDefaultSyncGroupID;
    mMasterPriority           = kDefaultMasterPriority;
    mMasterAnnounceIntervalMs = kDefaultMasterAnnounceIntervalMs;
    mSyncRequestIntervalMs    = kDefaultSyncRequestIntervalMs;
    mPanicThresholdUsec       = kDefaultPanicThresholdUsec;
    mAutoDisable              = kDefaultAutoDisable;

    // Create the eventfd we will use to signal our thread to wake up when
    // needed.
    mWakeupThreadFD = eventfd(0, EFD_NONBLOCK);

    // seed the random number generator (used to generated timeline IDs)
    srand48(static_cast<unsigned int>(systemTime()));
}

CommonTimeServer::~CommonTimeServer() {
    shutdownThread();

    // No need to grab the lock here.  We are in the destructor; if the the user
    // has a thread in any of the APIs while the destructor is being called,
    // there is a threading problem a the application level we cannot reasonably
    // do anything about.
    cleanupSocket_l();

    if (mWakeupThreadFD >= 0) {
        close(mWakeupThreadFD);
        mWakeupThreadFD = -1;
    }
}

bool CommonTimeServer::startServices() {
    // start the ICommonClock service
    mICommonClock = CommonClockService::instantiate(*this);
    if (mICommonClock == NULL)
        return false;

    // start the ICommonTimeConfig service
    mICommonTimeConfig = CommonTimeConfigService::instantiate(*this);
    if (mICommonTimeConfig == NULL)
        return false;

    return true;
}

bool CommonTimeServer::threadLoop() {
    // Register our service interfaces.
    if (!startServices())
        return false;

    // Hold the lock while we are in the main thread loop.  It will release the
    // lock when it blocks, and hold the lock at all other times.
    mLock.lock();
    runStateMachine_l();
    mLock.unlock();

    IPCThreadState::self()->stopProcess();
    return false;
}

bool CommonTimeServer::runStateMachine_l() {
    if (!mLocalClock.initCheck())
        return false;

    if (!mCommonClock.init(mLocalClock.getLocalFreq()))
        return false;

    // Enter the initial state.
    becomeInitial("startup");

    // run the state machine
    while (!exitPending()) {
        struct pollfd pfds[2];
        int rc, timeout;
        int eventCnt = 0;
        int64_t wakeupTime;
        uint32_t t1, t2;
        bool needHandleTimeout = false;

        // We are always interested in our wakeup FD.
        pfds[eventCnt].fd      = mWakeupThreadFD;
        pfds[eventCnt].events  = POLLIN;
        pfds[eventCnt].revents = 0;
        eventCnt++;

        // If we have a valid socket, then we are interested in what it has to
        // say as well.
        if (mSocket >= 0) {
            pfds[eventCnt].fd      = mSocket;
            pfds[eventCnt].events  = POLLIN;
            pfds[eventCnt].revents = 0;
            eventCnt++;
        }

        t1 = static_cast<uint32_t>(mCurTimeout.msecTillTimeout());
        t2 = static_cast<uint32_t>(mClockRecovery.applyRateLimitedSlew());
        timeout = static_cast<int>(t1 < t2 ? t1 : t2);

        // Note, we were holding mLock when this function was called.  We
        // release it only while we are blocking and hold it at all other times.
        mLock.unlock();
        rc          = poll(pfds, eventCnt, timeout);
        wakeupTime  = mLocalClock.getLocalTime();
        mLock.lock();

        // Is it time to shutdown?  If so, don't hesitate... just do it.
        if (exitPending())
            break;

        // Did the poll fail?  This should never happen and is fatal if it does.
        if (rc < 0) {
            ALOGE("%s:%d poll failed", __PRETTY_FUNCTION__, __LINE__);
            return false;
        }

        if (rc == 0) {
            needHandleTimeout = !mCurTimeout.msecTillTimeout();
            if (needHandleTimeout)
                mCurTimeout.setTimeout(kInfiniteTimeout);
        }

        // Were we woken up on purpose?  If so, clear the eventfd with a read.
        if (pfds[0].revents)
            clearPendingWakeupEvents_l();

        // Is out bind address dirty?  If so, clean up our socket (if any).
        // Alternatively, do we have an active socket but should be auto
        // disabled?  If so, release the socket and enter the proper sync state.
        bool droppedSocket = false;
        if (mBindIfaceDirty || ((mSocket >= 0) && shouldAutoDisable())) {
            cleanupSocket_l();
            mBindIfaceDirty = false;
            droppedSocket = true;
        }

        // Do we not have a socket but should have one?  If so, try to set one
        // up.
        if ((mSocket < 0) && mBindIfaceValid && !shouldAutoDisable()) {
            if (setupSocket_l()) {
                // Success!  We are now joining a new network (either coming
                // from no network, or coming from a potentially different
                // network).  Force our priority to be lower so that we defer to
                // any other masters which may already be on the network we are
                // joining.  Later, when we enter either the client or the
                // master state, we will clear this flag and go back to our
                // normal election priority.
                setForceLowPriority(true);
                switch (mState) {
                    // If we were in initial (whether we had a immediately
                    // before this network or not) we want to simply reset the
                    // system and start again.  Forcing a transition from
                    // INITIAL to INITIAL should do the job.
                    case CommonClockService::STATE_INITIAL:
                        becomeInitial("bound interface");
                        break;

                    // If we were in the master state, then either we were the
                    // master in a no-network situation, or we were the master
                    // of a different network and have moved to a new interface.
                    // In either case, immediately transition to Ronin at low
                    // priority.  If there is no one in the network we just
                    // joined, we will become master soon enough.  If there is,
                    // we want to be certain to defer master status to the
                    // existing timeline currently running on the network.
                    //
                    case CommonClockService::STATE_MASTER:
                        becomeRonin("leaving networkless mode");
                        break;

                    // If we were in any other state (CLIENT, RONIN, or
                    // WAIT_FOR_ELECTION) then we must be moving from one
                    // network to another.  We have lost our old master;
                    // transition to RONIN in an attempt to find a new master.
                    // If there are none out there, we will just assume
                    // responsibility for the timeline we used to be a client
                    // of.
                    default:
                        becomeRonin("bound interface");
                        break;
                }
            } else {
                // That's odd... we failed to set up our socket.  This could be
                // due to some transient network change which will work itself
                // out shortly; schedule a retry attempt in the near future.
                mCurTimeout.setTimeout(kSetupRetryTimeoutMs);
            }

            // One way or the other, we don't have any data to process at this
            // point (since we just tried to bulid a new socket).  Loop back
            // around and wait for the next thing to do.
            continue;
        } else if (droppedSocket) {
            // We just lost our socket, and for whatever reason (either no
            // config, or auto disable engaged) we are not supposed to rebuild
            // one at this time.  We are not going to rebuild our socket until
            // something about our config/auto-disabled status changes, so we
            // are basically in network-less mode.  If we are already in either
            // INITIAL or MASTER, just stay there until something changes.  If
            // we are in any other state (CLIENT, RONIN or WAIT_FOR_ELECTION),
            // then transition to either INITIAL or MASTER depending on whether
            // or not our timeline is valid.
            mStateChangeLog.log(ANDROID_LOG_INFO, LOG_TAG,
                    "Entering networkless mode interface is %s, "
                    "shouldAutoDisable = %s",
                    mBindIfaceValid ? "valid" : "invalid",
                    shouldAutoDisable() ? "true" : "false");
            if ((mState != ICommonClock::STATE_INITIAL) &&
                (mState != ICommonClock::STATE_MASTER)) {
                if (mTimelineID == ICommonClock::kInvalidTimelineID)
                    becomeInitial("network-less mode");
                else
                    becomeMaster("network-less mode");
            }

            continue;
        }

        // Time to handle the timeouts?
        if (needHandleTimeout) {
            if (!handleTimeout())
                ALOGE("handleTimeout failed");
            continue;
        }

        // Does our socket have data for us (assuming we still have one, we
        // may have RXed a packet at the same time as a config change telling us
        // to shut our socket down)?  If so, process its data.
        if ((mSocket >= 0) && (eventCnt > 1) && (pfds[1].revents)) {
            mLastPacketRxLocalTime = wakeupTime;
            if (!handlePacket())
                ALOGE("handlePacket failed");
        }
    }

    cleanupSocket_l();
    return true;
}

void CommonTimeServer::clearPendingWakeupEvents_l() {
    int64_t tmp;
    read(mWakeupThreadFD, &tmp, sizeof(tmp));
}

void CommonTimeServer::wakeupThread_l() {
    int64_t tmp = 1;
    write(mWakeupThreadFD, &tmp, sizeof(tmp));
}

void CommonTimeServer::cleanupSocket_l() {
    if (mSocket >= 0) {
        close(mSocket);
        mSocket = -1;
    }
}

void CommonTimeServer::shutdownThread() {
    // Flag the work thread for shutdown.
    this->requestExit();

    // Signal the thread in case its sleeping.
    mLock.lock();
    wakeupThread_l();
    mLock.unlock();

    // Wait for the thread to exit.
    this->join();
}

bool CommonTimeServer::setupSocket_l() {
    int rc;
    bool ret_val = false;
    struct sockaddr_in* ipv4_addr = NULL;
    char masterElectionEPStr[64];
    const int one = 1;

    // This should never be needed, but if we happened to have an old socket
    // lying around, be sure to not leak it before proceeding.
    cleanupSocket_l();

    // If we don't have a valid endpoint to bind to, then how did we get here in
    // the first place?  Regardless, we know that we are going to fail to bind,
    // so don't even try.
    if (!mBindIfaceValid)
        return false;

    sockaddrToString(mMasterElectionEP, true, masterElectionEPStr,
                     sizeof(masterElectionEPStr));
    mStateChangeLog.log(ANDROID_LOG_INFO, LOG_TAG,
                        "Building socket :: bind = %s master election = %s",
                        mBindIface.string(), masterElectionEPStr);

    // TODO: add proper support for IPv6.  Right now, we block IPv6 addresses at
    // the configuration interface level.
    if (AF_INET != mMasterElectionEP.ss_family) {
        mStateChangeLog.log(ANDROID_LOG_WARN, LOG_TAG,
                            "TODO: add proper IPv6 support");
        goto bailout;
    }

    // open a UDP socket for the timeline serivce
    mSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (mSocket < 0) {
        mStateChangeLog.log(ANDROID_LOG_ERROR, LOG_TAG,
                            "Failed to create socket (errno = %d)", errno);
        goto bailout;
    }

    // Bind to the selected interface using Linux's spiffy SO_BINDTODEVICE.
    struct ifreq ifr;
    memset(&ifr, 0, sizeof(ifr));
    snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s", mBindIface.string());
    ifr.ifr_name[sizeof(ifr.ifr_name) - 1] = 0;
    rc = setsockopt(mSocket, SOL_SOCKET, SO_BINDTODEVICE,
                    (void *)&ifr, sizeof(ifr));
    if (rc) {
        mStateChangeLog.log(ANDROID_LOG_ERROR, LOG_TAG,
                            "Failed to bind socket at to interface %s "
                            "(errno = %d)", ifr.ifr_name, errno);
        goto bailout;
    }

    // Bind our socket to INADDR_ANY and the master election port.  The
    // interface binding we made using SO_BINDTODEVICE should limit us to
    // traffic only on the interface we are interested in.  We need to bind to
    // INADDR_ANY and the specific master election port in order to be able to
    // receive both unicast traffic and master election multicast traffic with
    // just a single socket.
    struct sockaddr_in bindAddr;
    ipv4_addr = reinterpret_cast<struct sockaddr_in*>(&mMasterElectionEP);
    memcpy(&bindAddr, ipv4_addr, sizeof(bindAddr));
    bindAddr.sin_addr.s_addr = INADDR_ANY;
    rc = bind(mSocket,
              reinterpret_cast<const sockaddr *>(&bindAddr),
              sizeof(bindAddr));
    if (rc) {
        mStateChangeLog.log(ANDROID_LOG_ERROR, LOG_TAG,
                            "Failed to bind socket to port %hu (errno = %d)",
                            ntohs(bindAddr.sin_port), errno);
        goto bailout;
    }

    if (0xE0000000 == (ntohl(ipv4_addr->sin_addr.s_addr) & 0xF0000000)) {
        // If our master election endpoint is a multicast address, be sure to join
        // the multicast group.
        struct ip_mreq mreq;
        mreq.imr_multiaddr = ipv4_addr->sin_addr;
        mreq.imr_interface.s_addr = htonl(INADDR_ANY);
        rc = setsockopt(mSocket, IPPROTO_IP, IP_ADD_MEMBERSHIP,
                        &mreq, sizeof(mreq));
        if (rc == -1) {
            ALOGE("Failed to join multicast group at %s.  (errno = %d)",
                 masterElectionEPStr, errno);
            goto bailout;
        }

        // disable loopback of multicast packets
        const int zero = 0;
        rc = setsockopt(mSocket, IPPROTO_IP, IP_MULTICAST_LOOP,
                        &zero, sizeof(zero));
        if (rc == -1) {
            mStateChangeLog.log(ANDROID_LOG_ERROR, LOG_TAG,
                                "Failed to disable multicast loopback "
                                "(errno = %d)", errno);
            goto bailout;
        }
    } else
    if (ntohl(ipv4_addr->sin_addr.s_addr) == 0xFFFFFFFF) {
        // If the master election address is the broadcast address, then enable
        // the broadcast socket option
        rc = setsockopt(mSocket, SOL_SOCKET, SO_BROADCAST, &one, sizeof(one));
        if (rc == -1) {
            mStateChangeLog.log(ANDROID_LOG_ERROR, LOG_TAG,
                                "Failed to enable broadcast (errno = %d)",
                                errno);
            goto bailout;
        }
    } else {
        // If the master election address is neither broadcast, nor multicast,
        // then we are misconfigured.  The config API layer should prevent this
        // from ever happening.
        goto bailout;
    }

    // Set the TTL of sent packets to 1.  (Time protocol sync should never leave
    // the local subnet)
    rc = setsockopt(mSocket, IPPROTO_IP, IP_TTL, &one, sizeof(one));
    if (rc == -1) {
        mStateChangeLog.log(ANDROID_LOG_ERROR, LOG_TAG,
                            "Failed to set TTL to %d (errno = %d)", one, errno);
        goto bailout;
    }

    // get the device's unique ID
    if (!assignDeviceID())
        goto bailout;

    ret_val = true;

bailout:
    if (!ret_val)
        cleanupSocket_l();
    return ret_val;
}

// generate a unique device ID that can be used for arbitration
bool CommonTimeServer::assignDeviceID() {
    if (!mBindIfaceValid)
        return false;

    struct ifreq ifr;
    memset(&ifr, 0, sizeof(ifr));
    ifr.ifr_addr.sa_family = AF_INET;
    strlcpy(ifr.ifr_name, mBindIface.string(), IFNAMSIZ);

    int rc = ioctl(mSocket, SIOCGIFHWADDR, &ifr);
    if (rc) {
        ALOGE("%s:%d ioctl failed", __PRETTY_FUNCTION__, __LINE__);
        return false;
    }

    if (ifr.ifr_addr.sa_family != ARPHRD_ETHER) {
        ALOGE("%s:%d got non-Ethernet address", __PRETTY_FUNCTION__, __LINE__);
        return false;
    }

    mDeviceID = 0;
    for (int i = 0; i < ETH_ALEN; i++) {
        mDeviceID = (mDeviceID << 8) | ifr.ifr_hwaddr.sa_data[i];
    }

    return true;
}

// generate a new timeline ID
void CommonTimeServer::assignTimelineID() {
    do {
        mTimelineID = (static_cast<uint64_t>(lrand48()) << 32)
                    |  static_cast<uint64_t>(lrand48());
    } while (mTimelineID == ICommonClock::kInvalidTimelineID);
}

// Select a preference between the device IDs of two potential masters.
// Returns true if the first ID wins, or false if the second ID wins.
bool CommonTimeServer::arbitrateMaster(
        uint64_t deviceID1, uint8_t devicePrio1,
        uint64_t deviceID2, uint8_t devicePrio2) {
    return ((devicePrio1 >  devicePrio2) ||
           ((devicePrio1 == devicePrio2) && (deviceID1 > deviceID2)));
}

static void hexDumpToString(const uint8_t* src, size_t src_len,
                            char* dst, size_t dst_len) {
    size_t offset = 0;
    size_t i;

    for (i = 0; (i < src_len) && (offset < dst_len); ++i) {
        int res;
        if (0 == (i % 16)) {
            res = snprintf(dst + offset, dst_len - offset, "\n%04x :", i);
            if (res < 0)
                break;
            offset += res;
            if (offset >= dst_len)
                break;
        }

        res = snprintf(dst + offset, dst_len - offset, " %02x", src[i]);
        if (res < 0)
            break;
        offset += res;
    }

    dst[dst_len - 1] = 0;
}

bool CommonTimeServer::handlePacket() {
    uint8_t buf[256];
    struct sockaddr_storage srcAddr;
    socklen_t srcAddrLen = sizeof(srcAddr);

    ssize_t recvBytes = recvfrom(
            mSocket, buf, sizeof(buf), 0,
            reinterpret_cast<const sockaddr *>(&srcAddr), &srcAddrLen);

    if (recvBytes < 0) {
        mBadPktLog.log(ANDROID_LOG_ERROR, LOG_TAG,
                       "recvfrom failed (res %d, errno %d)",
                       recvBytes, errno);
        return false;
    }

    UniversalTimeServicePacket pkt;
    if (pkt.deserializePacket(buf, recvBytes, mSyncGroupID) < 0) {
        char hex[256];
        char srcEPStr[64];

        hexDumpToString(buf, static_cast<size_t>(recvBytes), hex, sizeof(hex));
        sockaddrToString(srcAddr, true, srcEPStr, sizeof(srcEPStr));

        mBadPktLog.log("Failed to parse %d byte packet from %s.%s",
                       recvBytes, srcEPStr, hex);
        return false;
    }

    bool result;
    switch (pkt.packetType) {
        case TIME_PACKET_WHO_IS_MASTER_REQUEST:
            result = handleWhoIsMasterRequest(&pkt.p.who_is_master_request,
                                              srcAddr);
            break;

        case TIME_PACKET_WHO_IS_MASTER_RESPONSE:
            result = handleWhoIsMasterResponse(&pkt.p.who_is_master_response,
                                               srcAddr);
            break;

        case TIME_PACKET_SYNC_REQUEST:
            result = handleSyncRequest(&pkt.p.sync_request, srcAddr);
            break;

        case TIME_PACKET_SYNC_RESPONSE:
            result = handleSyncResponse(&pkt.p.sync_response, srcAddr);
            break;

        case TIME_PACKET_MASTER_ANNOUNCEMENT:
            result = handleMasterAnnouncement(&pkt.p.master_announcement,
                                              srcAddr);
            break;

        default: {
            char srcEPStr[64];
            sockaddrToString(srcAddr, true, srcEPStr, sizeof(srcEPStr));

            mBadPktLog.log(ANDROID_LOG_WARN, LOG_TAG,
                           "unknown packet type (%d) from %s",
                           pkt.packetType, srcEPStr);

            result = false;
        } break;
    }

    return result;
}

bool CommonTimeServer::handleTimeout() {
    // If we have no socket, then this must be a timeout to retry socket setup.
    if (mSocket < 0)
        return true;

    switch (mState) {
        case ICommonClock::STATE_INITIAL:
            return handleTimeoutInitial();
        case ICommonClock::STATE_CLIENT:
            return handleTimeoutClient();
        case ICommonClock::STATE_MASTER:
            return handleTimeoutMaster();
        case ICommonClock::STATE_RONIN:
            return handleTimeoutRonin();
        case ICommonClock::STATE_WAIT_FOR_ELECTION:
            return handleTimeoutWaitForElection();
    }

    return false;
}

bool CommonTimeServer::handleTimeoutInitial() {
    if (++mInitial_WhoIsMasterRequestTimeouts ==
            kInitial_NumWhoIsMasterRetries) {
        // none of our attempts to discover a master succeeded, so make
        // this device the master
        return becomeMaster("initial timeout");
    } else {
        // retry the WhoIsMaster request
        return sendWhoIsMasterRequest();
    }
}

bool CommonTimeServer::handleTimeoutClient() {
    if (shouldPanicNotGettingGoodData())
        return becomeInitial("timeout panic, no good data");

    if (mClient_SyncRequestPending) {
        mClient_SyncRequestPending = false;

        if (++mClient_SyncRequestTimeouts < kClient_NumSyncRequestRetries) {
            // a sync request has timed out, so retry
            return sendSyncRequest();
        } else {
            // The master has failed to respond to a sync request for too many
            // times in a row.  Assume the master is dead and start electing
            // a new master.
            return becomeRonin("master not responding");
        }
    } else {
        // initiate the next sync request
        return sendSyncRequest();
    }
}

bool CommonTimeServer::handleTimeoutMaster() {
    // send another announcement from the master
    return sendMasterAnnouncement();
}

bool CommonTimeServer::handleTimeoutRonin() {
    if (++mRonin_WhoIsMasterRequestTimeouts == kRonin_NumWhoIsMasterRetries) {
        // no other master is out there, so we won the election
        return becomeMaster("no better masters detected");
    } else {
        return sendWhoIsMasterRequest();
    }
}

bool CommonTimeServer::handleTimeoutWaitForElection() {
    return becomeRonin("timeout waiting for election conclusion");
}

bool CommonTimeServer::handleWhoIsMasterRequest(
        const WhoIsMasterRequestPacket* request,
        const sockaddr_storage& srcAddr) {
    // Skip our own messages which come back via broadcast loopback.
    if (request->senderDeviceID == mDeviceID)
        return true;

    char srcEPStr[64];
    sockaddrToString(srcAddr, true, srcEPStr, sizeof(srcEPStr));
    mElectionLog.log("RXed WhoIs master request while in state %s.  "
                     "src %s reqTID %016llx ourTID %016llx",
                     stateToString(mState), srcEPStr,
                     request->timelineID, mTimelineID);

    if (mState == ICommonClock::STATE_MASTER) {
        // is this request related to this master's timeline?
        if (request->timelineID != ICommonClock::kInvalidTimelineID &&
            request->timelineID != mTimelineID)
            return true;

        WhoIsMasterResponsePacket pkt;
        pkt.initHeader(mTimelineID, mSyncGroupID);
        pkt.deviceID = mDeviceID;
        pkt.devicePriority = effectivePriority();

        mElectionLog.log("TXing WhoIs master resp to %s while in state %s.  "
                         "ourTID %016llx ourGID %016llx ourDID %016llx "
                         "ourPrio %u",
                         srcEPStr, stateToString(mState),
                         mTimelineID, mSyncGroupID,
                         pkt.deviceID, pkt.devicePriority);

        uint8_t buf[256];
        ssize_t bufSz = pkt.serializePacket(buf, sizeof(buf));
        if (bufSz < 0)
            return false;

        ssize_t sendBytes = sendto(
                mSocket, buf, bufSz, 0,
                reinterpret_cast<const sockaddr *>(&srcAddr),
                sizeof(srcAddr));
        if (sendBytes == -1) {
            ALOGE("%s:%d sendto failed", __PRETTY_FUNCTION__, __LINE__);
            return false;
        }
    } else if (mState == ICommonClock::STATE_RONIN) {
        // if we hear a WhoIsMaster request from another device following
        // the same timeline and that device wins arbitration, then we will stop
        // trying to elect ourselves master and will instead wait for an
        // announcement from the election winner
        if (request->timelineID != mTimelineID)
            return true;

        if (arbitrateMaster(request->senderDeviceID,
                            request->senderDevicePriority,
                            mDeviceID,
                            effectivePriority()))
            return becomeWaitForElection("would lose election");

        return true;
    } else if (mState == ICommonClock::STATE_INITIAL) {
        // If a group of devices booted simultaneously (e.g. after a power
        // outage) and all of them are in the initial state and there is no
        // master, then each device may time out and declare itself master at
        // the same time.  To avoid this, listen for
        // WhoIsMaster(InvalidTimeline) requests from peers.  If we would lose
        // arbitration against that peer, reset our timeout count so that the
        // peer has a chance to become master before we time out.
        if (request->timelineID == ICommonClock::kInvalidTimelineID &&
                arbitrateMaster(request->senderDeviceID,
                                request->senderDevicePriority,
                                mDeviceID,
                                effectivePriority())) {
            mInitial_WhoIsMasterRequestTimeouts = 0;
        }
    }

    return true;
}

bool CommonTimeServer::handleWhoIsMasterResponse(
        const WhoIsMasterResponsePacket* response,
        const sockaddr_storage& srcAddr) {
    // Skip our own messages which come back via broadcast loopback.
    if (response->deviceID == mDeviceID)
        return true;

    char srcEPStr[64];
    sockaddrToString(srcAddr, true, srcEPStr, sizeof(srcEPStr));
    mElectionLog.log("RXed WhoIs master response while in state %s.  "
                     "src %s respTID %016llx respDID %016llx respPrio %u "
                     "ourTID %016llx",
                     stateToString(mState), srcEPStr,
                     response->timelineID,
                     response->deviceID,
                     static_cast<uint32_t>(response->devicePriority),
                     mTimelineID);

    if (mState == ICommonClock::STATE_INITIAL || mState == ICommonClock::STATE_RONIN) {
        return becomeClient(srcAddr,
                            response->deviceID,
                            response->devicePriority,
                            response->timelineID,
                            "heard whois response");
    } else if (mState == ICommonClock::STATE_CLIENT) {
        // if we get multiple responses because there are multiple devices
        // who believe that they are master, then follow the master that
        // wins arbitration
        if (arbitrateMaster(response->deviceID,
                            response->devicePriority,
                            mClient_MasterDeviceID,
                            mClient_MasterDevicePriority)) {
            return becomeClient(srcAddr,
                                response->deviceID,
                                response->devicePriority,
                                response->timelineID,
                                "heard whois response");
        }
    }

    return true;
}

bool CommonTimeServer::handleSyncRequest(const SyncRequestPacket* request,
                                         const sockaddr_storage& srcAddr) {
    SyncResponsePacket pkt;
    pkt.initHeader(mTimelineID, mSyncGroupID);

    if ((mState == ICommonClock::STATE_MASTER) &&
        (mTimelineID == request->timelineID)) {
        int64_t rxLocalTime = mLastPacketRxLocalTime;
        int64_t rxCommonTime;

        // If we are master on an actual network and have actual clients, then
        // we are no longer low priority.
        setForceLowPriority(false);

        if (OK != mCommonClock.localToCommon(rxLocalTime, &rxCommonTime)) {
            return false;
        }

        int64_t txLocalTime = mLocalClock.getLocalTime();;
        int64_t txCommonTime;
        if (OK != mCommonClock.localToCommon(txLocalTime, &txCommonTime)) {
            return false;
        }

        pkt.nak = 0;
        pkt.clientTxLocalTime  = request->clientTxLocalTime;
        pkt.masterRxCommonTime = rxCommonTime;
        pkt.masterTxCommonTime = txCommonTime;
    } else {
        pkt.nak = 1;
        pkt.clientTxLocalTime  = 0;
        pkt.masterRxCommonTime = 0;
        pkt.masterTxCommonTime = 0;
    }

    uint8_t buf[256];
    ssize_t bufSz = pkt.serializePacket(buf, sizeof(buf));
    if (bufSz < 0)
        return false;

    ssize_t sendBytes = sendto(
            mSocket, &buf, bufSz, 0,
            reinterpret_cast<const sockaddr *>(&srcAddr),
            sizeof(srcAddr));
    if (sendBytes == -1) {
        ALOGE("%s:%d sendto failed", __PRETTY_FUNCTION__, __LINE__);
        return false;
    }

    return true;
}

bool CommonTimeServer::handleSyncResponse(
        const SyncResponsePacket* response,
        const sockaddr_storage& srcAddr) {
    if (mState != ICommonClock::STATE_CLIENT)
        return true;

    assert(mMasterEPValid);
    if (!sockaddrMatch(srcAddr, mMasterEP, true)) {
        char srcEP[64], expectedEP[64];
        sockaddrToString(srcAddr, true, srcEP, sizeof(srcEP));
        sockaddrToString(mMasterEP, true, expectedEP, sizeof(expectedEP));
        ALOGI("Dropping sync response from unexpected address."
             " Expected %s Got %s", expectedEP, srcEP);
        return true;
    }

    if (response->nak) {
        // if our master is no longer accepting requests, then we need to find
        // a new master
        return becomeRonin("master NAK'ed");
    }

    mClient_SyncRequestPending = 0;
    mClient_SyncRequestTimeouts = 0;
    mClient_PacketRTTLog.logRX(response->clientTxLocalTime,
                               mLastPacketRxLocalTime);

    bool result;
    if (!(mClient_SyncRespsRXedFromCurMaster++)) {
        // the first request/response exchange between a client and a master
        // may take unusually long due to ARP, so discard it.
        result = true;
    } else {
        int64_t clientTxLocalTime  = response->clientTxLocalTime;
        int64_t clientRxLocalTime  = mLastPacketRxLocalTime;
        int64_t masterTxCommonTime = response->masterTxCommonTime;
        int64_t masterRxCommonTime = response->masterRxCommonTime;

        int64_t rtt       = (clientRxLocalTime - clientTxLocalTime);
        int64_t avgLocal  = (clientTxLocalTime + clientRxLocalTime) >> 1;
        int64_t avgCommon = (masterTxCommonTime + masterRxCommonTime) >> 1;

        // if the RTT of the packet is significantly larger than the panic
        // threshold, we should simply discard it.  Its better to do nothing
        // than to take cues from a packet like that.
        int rttCommon = mCommonClock.localDurationToCommonDuration(rtt);
        if (rttCommon > (static_cast<int64_t>(mPanicThresholdUsec) * 
                         kRTTDiscardPanicThreshMultiplier)) {
            ALOGV("Dropping sync response with RTT of %lld uSec", rttCommon);
            mClient_ExpiredSyncRespsRXedFromCurMaster++;
            if (shouldPanicNotGettingGoodData())
                return becomeInitial("RX panic, no good data");
        } else {
            result = mClockRecovery.pushDisciplineEvent(avgLocal, avgCommon, rttCommon);
            mClient_LastGoodSyncRX = clientRxLocalTime;

            if (result) {
                // indicate to listeners that we've synced to the common timeline
                notifyClockSync();
            } else {
                ALOGE("Panic!  Observed clock sync error is too high to tolerate,"
                        " resetting state machine and starting over.");
                notifyClockSyncLoss();
                return becomeInitial("panic");
            }
        }
    }

    mCurTimeout.setTimeout(mSyncRequestIntervalMs);
    return result;
}

bool CommonTimeServer::handleMasterAnnouncement(
        const MasterAnnouncementPacket* packet,
        const sockaddr_storage& srcAddr) {
    uint64_t newDeviceID   = packet->deviceID;
    uint8_t  newDevicePrio = packet->devicePriority;
    uint64_t newTimelineID = packet->timelineID;

    // Skip our own messages which come back via broadcast loopback.
    if (newDeviceID == mDeviceID)
        return true;

    char srcEPStr[64];
    sockaddrToString(srcAddr, true, srcEPStr, sizeof(srcEPStr));
    mElectionLog.log("RXed master announcement while in state %s.  "
                     "src %s srcDevID %lld srcPrio %u srcTID %016llx",
                     stateToString(mState), srcEPStr,
                     newDeviceID, static_cast<uint32_t>(newDevicePrio),
                     newTimelineID);

    if (mState == ICommonClock::STATE_INITIAL ||
        mState == ICommonClock::STATE_RONIN ||
        mState == ICommonClock::STATE_WAIT_FOR_ELECTION) {
        // if we aren't currently following a master, then start following
        // this new master
        return becomeClient(srcAddr,
                            newDeviceID,
                            newDevicePrio,
                            newTimelineID,
                            "heard master announcement");
    } else if (mState == ICommonClock::STATE_CLIENT) {
        // if the new master wins arbitration against our current master,
        // then become a client of the new master
        if (arbitrateMaster(newDeviceID,
                            newDevicePrio,
                            mClient_MasterDeviceID,
                            mClient_MasterDevicePriority))
            return becomeClient(srcAddr,
                                newDeviceID,
                                newDevicePrio,
                                newTimelineID,
                                "heard master announcement");
    } else if (mState == ICommonClock::STATE_MASTER) {
        // two masters are competing - if the new one wins arbitration, then
        // cease acting as master
        if (arbitrateMaster(newDeviceID, newDevicePrio,
                            mDeviceID, effectivePriority()))
            return becomeClient(srcAddr, newDeviceID,
                                newDevicePrio, newTimelineID,
                                "heard master announcement");
    }

    return true;
}

bool CommonTimeServer::sendWhoIsMasterRequest() {
    assert(mState == ICommonClock::STATE_INITIAL || mState == ICommonClock::STATE_RONIN);

    // If we have no socket, then we must be in the unconfigured initial state.
    // Don't report any errors, just don't try to send the initial who-is-master
    // query.  Eventually, our network will either become configured, or we will
    // be forced into network-less master mode by higher level code.
    if (mSocket < 0) {
        assert(mState == ICommonClock::STATE_INITIAL);
        return true;
    }

    bool ret = false;
    WhoIsMasterRequestPacket pkt;
    pkt.initHeader(mSyncGroupID);
    pkt.senderDeviceID = mDeviceID;
    pkt.senderDevicePriority = effectivePriority();

    uint8_t buf[256];
    ssize_t bufSz = pkt.serializePacket(buf, sizeof(buf));
    if (bufSz >= 0) {
        char dstEPStr[64];
        sockaddrToString(mMasterElectionEP, true, dstEPStr, sizeof(dstEPStr));
        mElectionLog.log("TXing WhoIs master request to %s while in state %s.  "
                         "ourTID %016llx ourGID %016llx ourDID %016llx "
                         "ourPrio %u",
                         dstEPStr, stateToString(mState),
                         mTimelineID, mSyncGroupID,
                         pkt.senderDeviceID, pkt.senderDevicePriority);

        ssize_t sendBytes = sendto(
                mSocket, buf, bufSz, 0,
                reinterpret_cast<const sockaddr *>(&mMasterElectionEP),
                sizeof(mMasterElectionEP));
        if (sendBytes < 0)
            ALOGE("WhoIsMaster sendto failed (errno %d)", errno);
        ret = true;
    }

    if (mState == ICommonClock::STATE_INITIAL) {
        mCurTimeout.setTimeout(kInitial_WhoIsMasterTimeoutMs);
    } else {
        mCurTimeout.setTimeout(kRonin_WhoIsMasterTimeoutMs);
    }

    return ret;
}

bool CommonTimeServer::sendSyncRequest() {
    // If we are sending sync requests, then we must be in the client state and
    // we must have a socket (when we have no network, we are only supposed to
    // be in INITIAL or MASTER)
    assert(mState == ICommonClock::STATE_CLIENT);
    assert(mSocket >= 0);

    bool ret = false;
    SyncRequestPacket pkt;
    pkt.initHeader(mTimelineID, mSyncGroupID);
    pkt.clientTxLocalTime = mLocalClock.getLocalTime();

    if (!mClient_FirstSyncTX)
        mClient_FirstSyncTX = pkt.clientTxLocalTime;

    mClient_PacketRTTLog.logTX(pkt.clientTxLocalTime);

    uint8_t buf[256];
    ssize_t bufSz = pkt.serializePacket(buf, sizeof(buf));
    if (bufSz >= 0) {
        ssize_t sendBytes = sendto(
                mSocket, buf, bufSz, 0,
                reinterpret_cast<const sockaddr *>(&mMasterEP),
                sizeof(mMasterEP));
        if (sendBytes < 0)
            ALOGE("SyncRequest sendto failed (errno %d)", errno);
        ret = true;
    }

    mClient_SyncsSentToCurMaster++;
    mCurTimeout.setTimeout(mSyncRequestIntervalMs);
    mClient_SyncRequestPending = true;

    return ret;
}

bool CommonTimeServer::sendMasterAnnouncement() {
    bool ret = false;
    assert(mState == ICommonClock::STATE_MASTER);

    // If we are being asked to send a master announcement, but we have no
    // socket, we must be in network-less master mode.  Don't bother to send the
    // announcement, and don't bother to schedule a timeout.  When the network
    // comes up, the work thread will get poked and start the process of
    // figuring out who the current master should be.
    if (mSocket < 0) {
        mCurTimeout.setTimeout(kInfiniteTimeout);
        return true;
    }

    MasterAnnouncementPacket pkt;
    pkt.initHeader(mTimelineID, mSyncGroupID);
    pkt.deviceID = mDeviceID;
    pkt.devicePriority = effectivePriority();

    uint8_t buf[256];
    ssize_t bufSz = pkt.serializePacket(buf, sizeof(buf));
    if (bufSz >= 0) {
        char dstEPStr[64];
        sockaddrToString(mMasterElectionEP, true, dstEPStr, sizeof(dstEPStr));
        mElectionLog.log("TXing Master announcement to %s while in state %s.  "
                         "ourTID %016llx ourGID %016llx ourDID %016llx "
                         "ourPrio %u",
                         dstEPStr, stateToString(mState),
                         mTimelineID, mSyncGroupID,
                         pkt.deviceID, pkt.devicePriority);

        ssize_t sendBytes = sendto(
                mSocket, buf, bufSz, 0,
                reinterpret_cast<const sockaddr *>(&mMasterElectionEP),
                sizeof(mMasterElectionEP));
        if (sendBytes < 0)
            ALOGE("MasterAnnouncement sendto failed (errno %d)", errno);
        ret = true;
    }

    mCurTimeout.setTimeout(mMasterAnnounceIntervalMs);
    return ret;
}

bool CommonTimeServer::becomeClient(const sockaddr_storage& masterEP,
                                    uint64_t masterDeviceID,
                                    uint8_t  masterDevicePriority,
                                    uint64_t timelineID,
                                    const char* cause) {
    char newEPStr[64], oldEPStr[64];
    sockaddrToString(masterEP, true, newEPStr, sizeof(newEPStr));
    sockaddrToString(mMasterEP, mMasterEPValid, oldEPStr, sizeof(oldEPStr));

    mStateChangeLog.log(ANDROID_LOG_INFO, LOG_TAG,
            "%s --> CLIENT (%s) :%s"
            " OldMaster: %02x-%014llx::%016llx::%s"
            " NewMaster: %02x-%014llx::%016llx::%s",
            stateToString(mState), cause,
            (mTimelineID != timelineID) ? " (new timeline)" : "",
            mClient_MasterDevicePriority, mClient_MasterDeviceID,
            mTimelineID, oldEPStr,
            masterDevicePriority, masterDeviceID,
            timelineID, newEPStr);

    if (mTimelineID != timelineID) {
        // start following a new timeline
        mTimelineID = timelineID;
        mClockRecovery.reset(true, true);
        notifyClockSyncLoss();
    } else {
        // start following a new master on the existing timeline
        mClockRecovery.reset(false, true);
    }

    mMasterEP = masterEP;
    mMasterEPValid = true;

    // If we are on a real network as a client of a real master, then we should
    // no longer force low priority.  If our master disappears, we should have
    // the high priority bit set during the election to replace the master
    // because this group was a real group and not a singleton created in
    // networkless mode.
    setForceLowPriority(false);

    mClient_MasterDeviceID = masterDeviceID;
    mClient_MasterDevicePriority = masterDevicePriority;
    resetSyncStats();

    setState(ICommonClock::STATE_CLIENT);

    // add some jitter to when the various clients send their requests
    // in order to reduce the likelihood that a group of clients overload
    // the master after receiving a master announcement
    usleep((lrand48() % 100) * 1000);

    return sendSyncRequest();
}

bool CommonTimeServer::becomeMaster(const char* cause) {
    uint64_t oldTimelineID = mTimelineID;
    if (mTimelineID == ICommonClock::kInvalidTimelineID) {
        // this device has not been following any existing timeline,
        // so it will create a new timeline and declare itself master
        assert(!mCommonClock.isValid());

        // set the common time basis
        mCommonClock.setBasis(mLocalClock.getLocalTime(), 0);

        // assign an arbitrary timeline iD
        assignTimelineID();

        // notify listeners that we've created a common timeline
        notifyClockSync();
    }

    mStateChangeLog.log(ANDROID_LOG_INFO, LOG_TAG,
            "%s --> MASTER (%s) : %s timeline %016llx",
            stateToString(mState), cause,
            (oldTimelineID == mTimelineID) ? "taking ownership of"
                                           : "creating new",
            mTimelineID);

    memset(&mMasterEP, 0, sizeof(mMasterEP));
    mMasterEPValid = false;
    mClient_MasterDevicePriority = effectivePriority();
    mClient_MasterDeviceID = mDeviceID;
    mClockRecovery.reset(false, true);
    resetSyncStats();

    setState(ICommonClock::STATE_MASTER);
    return sendMasterAnnouncement();
}

bool CommonTimeServer::becomeRonin(const char* cause) {
    // If we were the client of a given timeline, but had never received even a
    // single time sync packet, then we transition back to Initial instead of
    // Ronin.  If we transition to Ronin and end up becoming the new Master, we
    // will be unable to service requests for other clients because we never
    // actually knew what time it was.  By going to initial, we ensure that
    // other clients who know what time it is, but would lose master arbitration
    // in the Ronin case, will step up and become the proper new master of the
    // old timeline.

    char oldEPStr[64];
    sockaddrToString(mMasterEP, mMasterEPValid, oldEPStr, sizeof(oldEPStr));
    memset(&mMasterEP, 0, sizeof(mMasterEP));
    mMasterEPValid = false;

    if (mCommonClock.isValid()) {
        mStateChangeLog.log(ANDROID_LOG_INFO, LOG_TAG,
             "%s --> RONIN (%s) : lost track of previously valid timeline "
             "%02x-%014llx::%016llx::%s (%d TXed %d RXed %d RXExpired)",
             stateToString(mState), cause,
             mClient_MasterDevicePriority, mClient_MasterDeviceID,
             mTimelineID, oldEPStr,
             mClient_SyncsSentToCurMaster,
             mClient_SyncRespsRXedFromCurMaster,
             mClient_ExpiredSyncRespsRXedFromCurMaster);

        mRonin_WhoIsMasterRequestTimeouts = 0;
        setState(ICommonClock::STATE_RONIN);
        return sendWhoIsMasterRequest();
    } else {
        mStateChangeLog.log(ANDROID_LOG_INFO, LOG_TAG,
             "%s --> INITIAL (%s) : never synced timeline "
             "%02x-%014llx::%016llx::%s (%d TXed %d RXed %d RXExpired)",
             stateToString(mState), cause,
             mClient_MasterDevicePriority, mClient_MasterDeviceID,
             mTimelineID, oldEPStr,
             mClient_SyncsSentToCurMaster,
             mClient_SyncRespsRXedFromCurMaster,
             mClient_ExpiredSyncRespsRXedFromCurMaster);

        return becomeInitial("ronin, no timeline");
    }
}

bool CommonTimeServer::becomeWaitForElection(const char* cause) {
    mStateChangeLog.log(ANDROID_LOG_INFO, LOG_TAG,
         "%s --> WAIT_FOR_ELECTION (%s) : dropping out of election,"
         " waiting %d mSec for completion.",
         stateToString(mState), cause, kWaitForElection_TimeoutMs);

    setState(ICommonClock::STATE_WAIT_FOR_ELECTION);
    mCurTimeout.setTimeout(kWaitForElection_TimeoutMs);
    return true;
}

bool CommonTimeServer::becomeInitial(const char* cause) {
    mStateChangeLog.log(ANDROID_LOG_INFO, LOG_TAG,
                        "Entering INITIAL (%s), total reset.",
                        cause);

    setState(ICommonClock::STATE_INITIAL);

    // reset clock recovery
    mClockRecovery.reset(true, true);

    // reset internal state bookkeeping.
    mCurTimeout.setTimeout(kInfiniteTimeout);
    memset(&mMasterEP, 0, sizeof(mMasterEP));
    mMasterEPValid = false;
    mLastPacketRxLocalTime = 0;
    mTimelineID = ICommonClock::kInvalidTimelineID;
    mClockSynced = false;
    mInitial_WhoIsMasterRequestTimeouts = 0;
    mClient_MasterDeviceID = 0;
    mClient_MasterDevicePriority = 0;
    mRonin_WhoIsMasterRequestTimeouts = 0;
    resetSyncStats();

    // send the first request to discover the master
    return sendWhoIsMasterRequest();
}

void CommonTimeServer::notifyClockSync() {
    if (!mClockSynced) {
        mClockSynced = true;
        mICommonClock->notifyOnTimelineChanged(mTimelineID);
    }
}

void CommonTimeServer::notifyClockSyncLoss() {
    if (mClockSynced) {
        mClockSynced = false;
        mICommonClock->notifyOnTimelineChanged(
                ICommonClock::kInvalidTimelineID);
    }
}

void CommonTimeServer::setState(ICommonClock::State s) {
    mState = s;
}

const char* CommonTimeServer::stateToString(ICommonClock::State s) {
    switch(s) {
        case ICommonClock::STATE_INITIAL:
            return "INITIAL";
        case ICommonClock::STATE_CLIENT:
            return "CLIENT";
        case ICommonClock::STATE_MASTER:
            return "MASTER";
        case ICommonClock::STATE_RONIN:
            return "RONIN";
        case ICommonClock::STATE_WAIT_FOR_ELECTION:
            return "WAIT_FOR_ELECTION";
        default:
            return "unknown";
    }
}

void CommonTimeServer::sockaddrToString(const sockaddr_storage& addr,
                                        bool addrValid,
                                        char* buf, size_t bufLen) {
    if (!bufLen || !buf)
        return;

    if (addrValid) {
        switch (addr.ss_family) {
            case AF_INET: {
                const struct sockaddr_in* sa =
                    reinterpret_cast<const struct sockaddr_in*>(&addr);
                unsigned long a = ntohl(sa->sin_addr.s_addr);
                uint16_t      p = ntohs(sa->sin_port);
                snprintf(buf, bufLen, "%lu.%lu.%lu.%lu:%hu",
                        ((a >> 24) & 0xFF), ((a >> 16) & 0xFF),
                        ((a >>  8) & 0xFF),  (a        & 0xFF), p);
            } break;

            case AF_INET6: {
                const struct sockaddr_in6* sa =
                    reinterpret_cast<const struct sockaddr_in6*>(&addr);
                const uint8_t* a = sa->sin6_addr.s6_addr;
                uint16_t       p = ntohs(sa->sin6_port);
                snprintf(buf, bufLen,
                        "%02X%02X:%02X%02X:%02X%02X:%02X%02X:"
                        "%02X%02X:%02X%02X:%02X%02X:%02X%02X port %hd",
                        a[0], a[1], a[ 2], a[ 3], a[ 4], a[ 5], a[ 6], a[ 7],
                        a[8], a[9], a[10], a[11], a[12], a[13], a[14], a[15],
                        p);
            } break;

            default:
                snprintf(buf, bufLen,
                         "<unknown sockaddr family %d>", addr.ss_family);
                break;
        }
    } else {
        snprintf(buf, bufLen, "<none>");
    }

    buf[bufLen - 1] = 0;
}

bool CommonTimeServer::sockaddrMatch(const sockaddr_storage& a1,
                                     const sockaddr_storage& a2,
                                     bool matchAddressOnly) {
    if (a1.ss_family != a2.ss_family)
        return false;

    switch (a1.ss_family) {
        case AF_INET: {
            const struct sockaddr_in* sa1 =
                reinterpret_cast<const struct sockaddr_in*>(&a1);
            const struct sockaddr_in* sa2 =
                reinterpret_cast<const struct sockaddr_in*>(&a2);

            if (sa1->sin_addr.s_addr != sa2->sin_addr.s_addr)
                return false;

            return (matchAddressOnly || (sa1->sin_port == sa2->sin_port));
        } break;

        case AF_INET6: {
            const struct sockaddr_in6* sa1 =
                reinterpret_cast<const struct sockaddr_in6*>(&a1);
            const struct sockaddr_in6* sa2 =
                reinterpret_cast<const struct sockaddr_in6*>(&a2);

            if (memcmp(&sa1->sin6_addr, &sa2->sin6_addr, sizeof(sa2->sin6_addr)))
                return false;

            return (matchAddressOnly || (sa1->sin6_port == sa2->sin6_port));
        } break;

        // Huh?  We don't deal in non-IPv[46] addresses.  Not sure how we got
        // here, but we don't know how to comapre these addresses and simply
        // default to a no-match decision.
        default: return false;
    }
}

bool CommonTimeServer::shouldPanicNotGettingGoodData() {
    if (mClient_FirstSyncTX) {
        int64_t now = mLocalClock.getLocalTime();
        int64_t delta = now - (mClient_LastGoodSyncRX
                             ? mClient_LastGoodSyncRX
                             : mClient_FirstSyncTX);
        int64_t deltaUsec = mCommonClock.localDurationToCommonDuration(delta);

        if (deltaUsec >= kNoGoodDataPanicThresholdUsec)
            return true;
    }

    return false;
}

void CommonTimeServer::PacketRTTLog::logTX(int64_t txTime) {
    txTimes[wrPtr] = txTime;
    rxTimes[wrPtr] = 0;
    wrPtr = (wrPtr + 1) % RTT_LOG_SIZE;
    if (!wrPtr)
        logFull = true;
}

void CommonTimeServer::PacketRTTLog::logRX(int64_t txTime, int64_t rxTime) {
    if (!logFull && !wrPtr)
        return;

    uint32_t i = logFull ? wrPtr : 0;
    do {
        if (txTimes[i] == txTime) {
            rxTimes[i] = rxTime;
            break;
        }
        i = (i + 1) % RTT_LOG_SIZE;
    } while (i != wrPtr);
}

}  // namespace android