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Posted to commits@guacamole.apache.org by "Michael Jumper (JIRA)" <ji...@apache.org> on 2017/03/24 04:08:41 UTC
[jira] [Resolved] (GUACAMOLE-239) Disconnects due to 'backwards'
running time
[ https://issues.apache.org/jira/browse/GUACAMOLE-239?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Michael Jumper resolved GUACAMOLE-239.
--------------------------------------
Resolution: Fixed
Fix Version/s: 0.9.13-incubating
> Disconnects due to 'backwards' running time
> -------------------------------------------
>
> Key: GUACAMOLE-239
> URL: https://issues.apache.org/jira/browse/GUACAMOLE-239
> Project: Guacamole
> Issue Type: Bug
> Reporter: Roman Stoffel
> Assignee: Michael Jumper
> Fix For: 0.9.13-incubating
>
> Attachments: backwards-running-time.PNG
>
>
> h3. Short version:
> We had Azure guacd running on an Azure Linux, Ubuntu 16.04 instance.
> This causes disconnects, since the protocol implementation does not expect backward running time.
> Changing the timestamp.c to use CLOCK_MONOTONIC fixes this issue.
> Pull request: https://github.com/apache/incubator-guacamole-server/pull/74
> h3. Details investigation:
> We observed frequent disconnects on our Azure running guacd instance.
> When monitoring the traffic between the web-socket-server and guacd, we discovered backward running time:
> !backwards-running-time.PNG|width=100%!
> This caused the condition in __guac_handle_sync to fail:
>
> {code:none}
> int __guac_handle_sync(guac_user* user, int argc, char** argv) {
> int frame_duration;
> guac_timestamp current = guac_timestamp_current();
> guac_timestamp timestamp = __guac_parse_int(argv[0]);
> /* Error if timestamp is in future */
> if (timestamp > user->client->last_sent_timestamp)
> return -1;
> {code}
> So, instrumented the timestamp.c, guac_timestamp_current:
> {code:none}
> #ifdef HAVE_CLOCK_GETTIME
> struct timespec current;
> /* Get current time */
> clock_gettime(CLOCK_REALTIME, ¤t);
> /* Calculate milliseconds */
> guac_timestamp ts = (guac_timestamp) current.tv_sec * 1000 + current.tv_nsec / 1000000;
> printf("TS clock_gettime %lld\n", (long long)ts);
> return ts;
> #else
> struct timeval current;
> /* Get current time */
> gettimeofday(¤t, NULL);
> /* Calculate milliseconds */
> guac_timestamp ts = (guac_timestamp) current.tv_sec * 1000 + current.tv_usec / 1000;
> printf("TS gettimeofday %lld\n", (long long)ts);
> return ts;
> #endif
> {code}
> This, indeed yielded 'backwards' running time, with connection failure on it:
> {code:none}
> TS clock_gettime 1489106020137
> TS clock_gettime 1489106020137 <-- Send out
> TS clock_gettime 1489106020077
> TS clock_gettime 1489106020077
> TS clock_gettime 1489106020077
> TS clock_gettime 1489106020088 <-- Send out, now expect's this time. Causing failure when client answers with 1489106020137
> TS clock_gettime 14guacd[7]: DEBUG: Sending ts 1489106020042
> guacd[7]: DEBUG: Expect 1489106020010 <= 1489106020042
> guacd[7]: DEBUG: Sync time is ok.
> guacd[7]: DEBUG: Sending ts 1489106020074
> guacd[7]: DEBUG: Expect 1489106020042 <= 1489106020074
> guacd[7]: DEBUG: Sync time is ok.
> guacd[7]: DEBUG: Sending ts 1489106020104
> guacd[7]: DEBUG: Expect 1489106020074 <= 1489106020104
> guacd[7]: DEBUG: Sync time is ok.
> guacd[7]: DEBUG: Sending ts 1489106020137
> guacd[7]: DEBUG: Expect 1489106020104 <= 1489106020137
> guacd[7]: DEBUG: Sync time is ok.
> guacd[7]: DEBUG: Sending ts 1489106020088
> guacd[7]: DEBUG: Expect 1489106020137 <= 1489106020088
> guacd[7]: DEBUG: Sync time is out of order.
> guacd[7]: WARNING: Connection aborted
> guacd[7]: DEBUG: Failing instruction handler in client was "sync"
> guacd[7]: DEBUG: Sending ts 1489106020125
> guacd[7]: DEBUG: Output thread terminated.
> guacd[7]: INFO: Client disconnected
> 89106020042
> TS clock_gettime 1489106020043
> TS clock_gettime 1489106020063
> TS clock_gettime 1489106020063
> TS clock_gettime 1489106020063
> TS clock_gettime 1489106020074
> TS clock_gettime 1489106020074
> TS clock_gettime 1489106020093
> TS clock_gettime 1489106020094
> TS clock_gettime 1489106020094
> TS clock_gettime 1489106020104
> TS clock_gettime 1489106020105
> TS clock_gettime 1489106020126
> TS clock_gettime 1489106020126
> TS clock_gettime 1489106020126
> TS clock_gettime 1489106020137
> TS clock_gettime 1489106020137
> TS clock_gettime 1489106020077
> TS clock_gettime 1489106020077
> TS clock_gettime 1489106020077
> TS clock_gettime 1489106020088
> TS clock_gettime 1489106020088
> TS clock_gettime 1489106020114
> TS clock_gettime 1489106020115
> TS clock_gettime 1489106020115
> TS clock_gettime 1489106020125
> TS clock_gettime 1489106020126
> TS clock_gettime 1489106020529
> {code}
> Using clock_gettime(CLOCK_MONOTONIC,..) instead of clock_gettime(CLOCK_REALTIME,..) fixed this issue.
> From the man pages, the CLOCK_MONOTONIC is precisely to ensure that time never runs backwards.
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