[asterisk-bugs] [JIRA] (ASTERISK-24894) iax2_poke_noanswer expiration timer too short

[Rusty Newton (JIRA)]

     [ https://issues.asterisk.org/jira/browse/ASTERISK-24894?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Rusty Newton updated ASTERISK-24894:
------------------------------------

    Status: Open  (was: Triage)

> iax2_poke_noanswer expiration timer too short
> ---------------------------------------------
>
>                 Key: ASTERISK-24894
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-24894
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/chan_iax2
>    Affects Versions: 13.2.0
>            Reporter: Y Ateya
>            Assignee: Rusty Newton
>         Attachments: poke_noanswer_duration.diff
>
>
> POKE is used to check for peer availability, but it is not given enough time to retry in case of packet loss (if qualify time is high).
> If qualify time is set to 10 seconds ({{qualify = 1000}} in iax.conf); peer will be UNREACHABLE due to single packet loss.
> Here is the code snippet which start timer for poke_noasnwer
> {code}
> 	/* Speed up retransmission times for this qualify call */
> 	iaxs[peer->callno]->pingtime = peer->maxms / 4 + 1;
> 	iaxs[peer->callno]->peerpoke = peer;
> 	if (peer->pokeexpire > -1) {
> 		if (!AST_SCHED_DEL(sched, peer->pokeexpire)) {
> 			peer->pokeexpire = -1;
> 			peer_unref(peer);
> 		}
> 	}
> 	/* Queue up a new task to handle no reply */
> 	/* If the host is already unreachable then use the unreachable interval instead */
> 	if (peer->lastms < 0)
> 		peer->pokeexpire = iax2_sched_add(sched, peer->pokefreqnotok, iax2_poke_noanswer, peer_ref(peer));
> 	else
> 		peer->pokeexpire = iax2_sched_add(sched, DEFAULT_MAXMS * 2, iax2_poke_noanswer, peer_ref(peer));
> {code}
> In this code, if {{peer->lastms}} is more than 0 (i.e last ping or poke succeeded), {{iax2_poke_noanswer}} will be called if we didn't get POKE reply before {{DEFAULT_MAXMS * 2}} (i.e. 4 seconds).
> ping time value {noformat}iaxs[peer->callno]->pingtime = peer->maxms / 4 + 1;{noformat} will be {{10000 / 4 + 1}} (i.e 2.5 seconds).
> Since IAX frames are retried {{fr->retrytime = pvt->pingtime * 2;}}, so POKE frame will be retried every 5 seconds!
> So a single POKE packet loss will make the peer UNREACHABLE.
> To fix this, iax2_poke_noanswer timer shall be {{iaxs[peer->callno]->pingtime * 2 * max_retries}} to allow for proper retries for POKE packet.



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