[asterisk-bugs] [JIRA] (ASTERISK-26100) [patch] Asterisk will reject, with a 488, subsequent T.38 reinvite to T.38 negotiation.

[Richard Mudgett (JIRA)]

     [ https://issues.asterisk.org/jira/browse/ASTERISK-26100?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Richard Mudgett updated ASTERISK-26100:
---------------------------------------

    Description: 
Hi all,

I already searched bug tracker and found similar solved bug, but no one fixed my issue.

I've the following scenario:
{noformat}
FAX (Offerer) <--> SIP Server <--> Asterisk T.38 Passthrough <--> Oracle SBC (ex Acme Packet) <--> PSTN <--> Fax (Receiver)
{noformat}

Offerer starts a Fax transmission as in-audio call (g729 coded). This call get switched by network side (Oracle SBC) as T.38 with a first invite. During fax negotiation Oracle SBC send back a second T.38 re-invite and Asterisk answer with a 488 after 5 seconds due the following code statement:
{noformat}
p->t38id = ast_sched_add(sched, 5000, sip_t38_abort, dialog_ref(p, "passing dialog ptr into sched structure based on t38id for sip_t38_abort."));
{noformat}

Reading code seems that a reinvite is not allowed, during fax transmission, after channel is placed in AST_STATE_UP.

Reading all RFCs and ITU-T specifications no one describe this scenario but  at the same times no one disallow it.

I wrote a patch for chan_sip.c to handle this behaviour. All seems to works fine for all customers that reports to me this issue and no regressions are observed.

I attached a PCAP trace (for better scenario description) and a patch.

Regards

  was:
Hi all,

I already searched bug tracker and found similar solved bug, but no one fixed my issue.

I've te following scenario:

FAX (Offerer) <--> SIP Server <--> Asterisk T.38 Passthrough <--> Oracle SBC (ex Acme Packet) <--> PSTN <--> Fax (Receiver)

Offerer starts a Fax transmission as in-audio call (g729 coded). This call get switched by network side (Oracle SBC) as T.38 with a first invite. During fax negotiation Oracle SBC send back a second T.38 re-invite and Asterisk answer with a 488 after 5 seconds due the following code statement:

p->t38id = ast_sched_add(sched, 5000, sip_t38_abort, dialog_ref(p, "passing dialog ptr into sched structure based on t38id for sip_t38_abort."));

Reading code seems that a reinvite is not allowed, during fax transmission, after channel is placed in AST_STATE_UP.

Reading all RFCs and ITU-T specifications no one describe this scenario but  at the same times no one disallow it.

I wrote a patch for chan_sip.c to handle this behaviour. All seems to works fine for all cutomers that reports to me this issue and no regressions are observed.

I attached a PCAP trace (for better scenario description) and a patch.

Regards


> [patch] Asterisk will reject, with a 488, subsequent T.38 reinvite to T.38 negotiation.
> ---------------------------------------------------------------------------------------
>
>                 Key: ASTERISK-26100
>                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-26100
>             Project: Asterisk
>          Issue Type: Bug
>      Security Level: None
>          Components: Channels/chan_sip/T.38
>    Affects Versions: 11.22.0
>         Environment: Ubuntu 14.04 LTS (asterisk is always compiled from scratch)
>            Reporter: Parantido Julius De Rica
>         Attachments: fax-trace.pcap, t38-488-reinvite.diff
>
>
> Hi all,
> I already searched bug tracker and found similar solved bug, but no one fixed my issue.
> I've the following scenario:
> {noformat}
> FAX (Offerer) <--> SIP Server <--> Asterisk T.38 Passthrough <--> Oracle SBC (ex Acme Packet) <--> PSTN <--> Fax (Receiver)
> {noformat}
> Offerer starts a Fax transmission as in-audio call (g729 coded). This call get switched by network side (Oracle SBC) as T.38 with a first invite. During fax negotiation Oracle SBC send back a second T.38 re-invite and Asterisk answer with a 488 after 5 seconds due the following code statement:
> {noformat}
> p->t38id = ast_sched_add(sched, 5000, sip_t38_abort, dialog_ref(p, "passing dialog ptr into sched structure based on t38id for sip_t38_abort."));
> {noformat}
> Reading code seems that a reinvite is not allowed, during fax transmission, after channel is placed in AST_STATE_UP.
> Reading all RFCs and ITU-T specifications no one describe this scenario but  at the same times no one disallow it.
> I wrote a patch for chan_sip.c to handle this behaviour. All seems to works fine for all customers that reports to me this issue and no regressions are observed.
> I attached a PCAP trace (for better scenario description) and a patch.
> Regards



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