Commit Graph

3758 Commits

Author SHA1 Message Date
Joshua Colp
693c06f8a3 bridge: Change participant SFU streams when source streams change.
Some endpoints do not like a stream being reused for a new
media stream. The frame/jitterbuffer can rely on underlying
attributes of the media stream in order to order the packets.
When a new stream takes its place without any notice the
buffer can get confused and the media ends up getting dropped.

This change uses the SSRC change to determine that a new source
is reusing an existing stream and then bridge_softmix renegotiates
each participant such that they see a new media stream. This
causes the frame/jitterbuffer to start fresh and work as expected.

ASTERISK-27277

Change-Id: I30ccbdba16ca073d7f31e0e59ab778c153afae07
2017-09-21 17:18:25 +00:00
Jean Aunis
47b41bd3ae bridge : Fix one-way direct-media when early bridging with native_rtp
When two channels were early bridged in a native_rtp bridge, the RTP description
on one side was not updated when the other side answered.
This patch forbids non-answered channels to enter a native_rtp bridge, and
triggers a bridge reconfiguration when an ANSWER frame is received.

ASTERISK-27257

Change-Id: If1aaee1b4ed9658a1aa91ab715ee0a6413b878df
2017-09-20 10:19:26 -05:00
George Joseph
752f0533dd res_pjsip: Add handling for incoming unsolicited MWI NOTIFY
A new endpoint parameter "incoming_mwi_mailbox" allows Asterisk to
receive unsolicited MWI NOTIFY requests and make them available to
other modules via the stasis message bus.

res_pjsip_pubsub has a new handler "pubsub_on_rx_mwi_notify_request"
that parses a simple-message-summary body and, if
endpoint->incoming_mwi_account is set, calls ast_publish_mwi_state
with the voice-message counts from the message.

Change-Id: I08bae3d16e77af48fcccc2c936acce8fc0ef0f3c
2017-09-13 08:24:14 -06:00
George Joseph
a824fcc8e8 stasis/control: Fix possible deadlock with swap channel
If an error occurs during a bridge impart it's possible that
the "bridge_after" callback might try to run before
control_swap_channel_in_bridge has been signalled to continue.
Since control_swap_channel_in_bridge is holding the control lock
and the callback needs it, a deadlock will occur.

* control_swap_channel_in_bridge now only holds the control
  lock while it's actually modifying the control structure and
  releases it while the bridge impart is running.
* bridge_after_cb is now tolerant of impart failures.

Change-Id: Ifd239aa93955b3eb475521f61e284fcb0da2c3b3
2017-09-06 13:00:42 -05:00
Walter Doekes
329e111947 res/res_pjsip: Standardize/fix localnet checks across pjsip.
In 2dee95cc (ASTERISK-27024) and 776ffd77 (ASTERISK-26879) there was
confusion about whether the transport_state->localnet ACL has ALLOW or
DENY semantics.

For the record: the localnet has DENY semantics, meaning that "not in
the list" means ALLOW, and the local nets are in the list.

Therefore, checks like this look wrong, but are right:

    /* See if where we are sending this request is local or not, and if
       not that we can get a Contact URI to modify */
    if (ast_apply_ha(transport_state->localnet, &addr) != AST_SENSE_ALLOW) {
        ast_debug(5, "Request is being sent to local address, "
                     "skipping NAT manipulation\n");

(In the list == localnet == DENY == skip NAT manipulation.)

And conversely, other checks that looked right, were wrong.

This change adds two macro's to reduce the confusion and uses those
instead:

    ast_sip_transport_is_nonlocal(transport_state, addr)
    ast_sip_transport_is_local(transport_state, addr)

ASTERISK-27248 #close

Change-Id: Ie7767519eb5a822c4848e531a53c0fd054fae934
2017-09-05 09:17:24 -05:00
Corey Farrell
0372157a48 AST-2017-006: Fix app_minivm application MinivmNotify command injection
An admin can configure app_minivm with an externnotify program to be run
when a voicemail is received.  The app_minivm application MinivmNotify
uses ast_safe_system() for this purpose which is vulnerable to command
injection since the Caller-ID name and number values given to externnotify
can come from an external untrusted source.

* Add ast_safe_execvp() function.  This gives modules the ability to run
external commands with greater safety compared to ast_safe_system().
Specifically when some parameters are filled by untrusted sources the new
function does not allow malicious input to break argument encoding.  This
may be of particular concern where CALLERID(name) or CALLERID(num) may be
used as a parameter to a script run by ast_safe_system() which could
potentially allow arbitrary command execution.

* Changed app_minivm.c:run_externnotify() to use the new ast_safe_execvp()
instead of ast_safe_system() to avoid command injection.

* Document code injection potential from untrusted data sources for other
shell commands that are under user control.

ASTERISK-27103

Change-Id: I7552472247a84cde24e1358aaf64af160107aef1
2017-08-30 18:42:58 +00:00
Torrey Searle
c5b89a390c res/res_pjsip_session: allow SDP answer to be regenerated
If an SDP answer hasn't been sent yet, it's legal to change it.
This is required for PJSIP_DTMF_MODE to work correctly, and can
also have use in the future for updating codecs too.

ASTERISK-27209 #close

Change-Id: Idbbfb7cb3f72fbd96c94d10d93540f69bd51e7a1
2017-08-25 14:19:55 +02:00
Richard Mudgett
efa6262814 bridge: Fix softmix bridge deadlock.
* Fix deadlock in
bridge_softmix.c:softmix_bridge_stream_topology_changed() between
bridge_channel and channel locks.

* The new bridge technology topology change callbacks must be called with
the bridge locked.  The callback references the bridge channel list, the
bridge technology could change, and the bridge stream mapping is updated.

ASTERISK-27212

Change-Id: Ide4360ab853607e738ad471721af3f561ddd83be
2017-08-22 11:57:21 -05:00
Richard Mudgett
6c555891eb channel: Fix topology API locking.
* ast_channel_request_stream_topology_change() must not be called with any
channel locks held.

* ast_channel_stream_topology_changed() must be called with only the
passed channel lock held.

ASTERISK-27212

Change-Id: I843de7956d9f1cc7cc02025aea3463d8fe19c691
2017-08-22 11:57:21 -05:00
Richard Mudgett
b9f6697f06 res_pjsip: Remove ephemeral registered contacts on transport shutdown.
The fix for the issue is broken up into three parts.

This is part two which handles the server side of REGISTER requests when
rewrite_contact is enabled.  Any registered reliable transport contact
becomes invalid when the transport connection becomes disconnected.

* Monitor the rewrite_contact's reliable transport REGISTER contact for
shutdown.  If it is shutdown then the contact must be removed because it
is no longer valid.  Otherwise, when the client attempts to re-REGISTER it
may be blocked because the invalid contact is there.  Also if we try to
send a call to the endpoint using the invalid contact then the endpoint is
not likely to see the request.  The endpoint either won't be listening on
that port for new connections or a NAT/firewall will block it.

* Prune any rewrite_contact's registered reliable transport contacts on
boot.  The reliable transport no longer exists so the contact is invalid.

* Websockets always rewrite the REGISTER contact address and the transport
needs to be monitored for shutdown.

* Made the websocket transport set a unique name since that is what we use
as the ao2 container key.  Otherwise, we would not know which transport we
find when one of them shuts down.  The names are also used for PJPROJECT
debug logging.

* Made the websocket transport post the PJSIP_TP_STATE_CONNECTED state
event.  Now the global keep_alive_interval option, initially idle shutdown
timer, and the server REGISTER contact monitor can work on wetsocket
transports.

* Made the websocket transport set the PJSIP_TP_DIR_INCOMING direction.
Now initially idle websockets will automatically shutdown.

ASTERISK-27147

Change-Id: I397a5e7d18476830f7ffe1726adf9ee6c15964f4
2017-08-10 12:18:28 -05:00
Richard Mudgett
0de033c9c6 res_pjsip: PJSIP Transport state monitor refactor.
The fix for the issue is broken up into three parts.

This is part one which refactors the transport state monitor code to allow
more modules to be able to monitor transports.

* Pull the management of PJPROJECT's transport state callback code from
res_pjsip_transport_management.c into res_pjsip.  Now other modules can
dynamically add and remove themselves from transport monitoring without
worrying about breaking PJPROJECT's callback chain.

* Add the ability for other modules to get a callback whenever a specific
transport is shutdown.

ASTERISK-27147

Change-Id: I7d9a31371eb1487c9b7050cf82a9af5180a57912
2017-08-10 12:18:28 -05:00
Torrey Searle
be8cb75dd2 res_rtp_asterisk: Make P2P bridge Asymmetric codec aware
Introduce a new property to rtp-engine to make it aware of
the desire for assymetric codecs or not.  If asymmetric codecs
is not allowed, the bridge will compare read/write formats
and shut down the p2p bridge if needed

ASTERISK-26745 #close

Change-Id: I0d9c83e5356df81661e58d40a8db565833501a6f
2017-08-09 15:54:45 +02:00
Kevin Harwell
09995fae53 res_pjsip_session/_sdp_rtp: Handling of 'msid' is incorrect
Currently, the handling of the msid attribute is not quite right. According to
the spec the msid's between the offer/answer are not dependent upon one another.
Meaning the same msid's given in an offer do not have to be returned in the
answer for a given stream. And they probably shouldn't be (copied/reused) since
this can potentially cause some browser side confusion.

This patch generates new msids when both an offer and answer are sent from
Asterisk. However, Asterisk does reuse the original msid it sent out for a
reinvite. Also audio+video streams are paired together by sharing the same
stream id, but a different track id.

ASTERISK-27179 #close

Change-Id: Ifaec06dc7e65ad841633a24ebec8c8a9302d6643
2017-08-04 17:16:25 -05:00
Joshua Colp
448317ddc7 res_pjsip: Add support for dnsmgr to external_media_address.
The "external_media_address" option on transports is now
resolved using dnsmgr. This allows it to be automatically
refreshed regularly if refreshes are enabled in dnsmgr.
If the system is using a dynamic IP address a dynamic DNS
hostname can be provided to keep the IP address up to
date.

Change-Id: Ia54771720dff0105bde55d5bbb81a3ba437e05b2
2017-08-01 15:39:25 -06:00
Torrey Searle
c24cdbf4ae chan_pjsip: add a new function PJSIP_DTMF_MODE
This function is a replica of SIPDtmfMode, allowing the DTMF mode of a
PJSIP call to be modified on a per-call basis

ASTERISK-27085 #close

Change-Id: I20eef5da3e5d1d3e58b304416bc79683f87e7612
2017-08-01 15:33:38 -06:00
Joshua Colp
1c07c80eef Merge "bridge_softmix / res_rtp_asterisk: Fix packet loss and renegotiation issues." into 15 2017-07-26 10:48:19 -05:00
Jenkins2
fab609deeb Merge "Core: Add support for systemd socket activation." into 15 2017-07-26 08:59:58 -05:00
Joshua Colp
451d86d62e bridge_softmix / res_rtp_asterisk: Fix packet loss and renegotiation issues.
This change does a few things to improve packet loss and renegotiation:

1. On outgoing RTP streams we will now properly reflect out of order
packets and packet loss in the sequence number. This allows the
remote jitterbuffer to better reorder things.

2. Video updates can now be discarded for a period of time
after one has been sent to prevent flooding of clients.

3. For declined and removed streams we will now release any
media session resources associated with them. This was not
previously done and caused an issue where old state was being
used for a new stream.

4. RTP bundling was not actually removing bundled RTP instances
from the parent. This has been resolved by removing based on
the RTP instance itself and not the SSRC.

5. The code did not properly handle explicitly unbundling an
RTP instance from its parent. This now works as expected.

ASTERISK-27143

Change-Id: Ibd91362f0e4990b6129638e712bc8adf0899fd45
2017-07-26 06:00:56 -05:00
Joshua Colp
927fc6bbd9 core: Add VP9 passthrough support.
This change adds VP9 as a known codec and creates a cached
"vp9" media format for use.

Change-Id: I025a93ed05cf96153d66f36db1839109cc24c5cc
2017-07-24 13:51:12 -05:00
Matthew Fredrickson
9aa4942a49 format.h: Fix a few minor errors in comments.
A few minor problems were found in comments in format.h.  This patch fixes them.

Change-Id: I07f0bdb47b93359b361c4c3d8ecc87cd3199dd94
2017-07-24 09:29:27 -05:00
Corey Farrell
eea9da2f42 Core: Add support for systemd socket activation.
This change adds support for socket activation of certain SOCK_STREAM
listeners in Asterisk:
* AMI / AMI over TLS
* CLI
* HTTP / HTTPS

Example systemd units are provided.  This support extends to any socket
which is initialized using ast_tcptls_server_start, so any unknown
modules using this function will support socket activation.

Asterisk continues to function as normal if socket activation is not
enabled or if systemd development headers are not available during
build.

ASTERISK-27063 #close

Change-Id: Id814ee6a892f4b80d018365c8ad8d89063474f4d
2017-07-21 14:04:33 -05:00
George Joseph
3e8d628c0e Update AMI and ARI versions for master/15 and update UPDATE.txt
AMI goes from 3.2.0 to 4.0.0
ARI goes from 2.0.0 to 3.0.0

Copied UPGRADE.txt -> UPGRADE-15.txt
Created new UPGRADE.txt
Removed a log file that was accidentally checked in a while ago

Change-Id: I1c794f910038459b13e16f9c3a12c44e56f142f7
2017-07-20 10:05:48 -06:00
Joshua Colp
f43fc91911 Merge "core: Add digit filtering to ast_waitfordigit_full" 2017-07-19 13:09:56 -05:00
Jenkins2
62c381afdb Merge "core: Add PARSE_TIMELEN support to ast_parse_arg and ACO." 2017-07-19 09:25:59 -05:00
Jenkins2
594c7a50af Merge "bridge/core_unreal: Fix SFU bugs with forwarding frames." 2017-07-17 17:59:32 -05:00
Kevin Harwell
7da6ddda30 res_pjsip: Add "webrtc" configuration option
This patch creates a new configuration option called "webrtc". When enabled it
defaults and enables the following options that are needed in order for webrtc
to work in Asterisk:

  rtcp-mux, use_avpf, ice_support, and use_received_transport=enabled
  media_encryption=dtls
  dtls_verify=fingerprint
  dtls_setup=actpass

When "webrtc" is enabled, this patch also parses the "msid" media level
attribute from an SDP. It will also appropriately add it onto the outgoing
session when applicable.

Lastly, when "webrtc" is enabled h264 RTCP FIR feedback frames are now sent.

ASTERISK-27119 #close

Change-Id: I5ec02e07c5d5b9ad86a34fdf31bf2f9da9aac6fd
2017-07-13 18:19:35 -05:00
Jenkins2
0f45c979a3 Merge "res_rtp_asterisk / res_pjsip: Add support for BUNDLE." 2017-07-13 14:40:11 -05:00
Corey Farrell
78a50b0343 core: Add PARSE_TIMELEN support to ast_parse_arg and ACO.
This adds support for parsing timelen values from config files.  This
includes support for all flags which apply to PARSE_INT32.  Support for
this parser is added to ACO via the OPT_TIMELEN_T option type.

Fixes an issue where extra characters provided to ast_app_parse_timelen
were ignored, they now cause an error.

Testing is included.

ASTERISK-27117 #close

Change-Id: I6b333feca7e3f83b4ef5bf2636fc0fd613742554
2017-07-13 11:44:14 -04:00
Joshua Colp
065c3005ad res_rtp_asterisk / res_pjsip: Add support for BUNDLE.
BUNDLE is a specification used in WebRTC to allow multiple
streams to use the same underlying transport. This reduces
the number of ICE and DTLS negotiations that has to occur
to 1 normally.

This change implements this by adding support for it to
the RTP SDP module in PJSIP. BUNDLE can be turned on using
the "bundle" option and on an offer we will offer to
bundle streams together. On an answer we will accept any
bundle groups provided. Once accepted each stream is bundled
to another RTP instance for transport.

For the res_rtp_asterisk changes the ability to bundle
an RTP instance to another based on the SSRC received
from the remote side has been added. For outgoing traffic
if an RTP instance is bundled to another we will use the
other RTP instance for any transport related things. For
incoming traffic received from the transport instance we
look up the correct instance based on the SSRC and use it
for any non-transport related data.

ASTERISK-27118

Change-Id: I96c0920b9f9aca7382256484765a239017973c11
2017-07-13 14:47:50 +00:00
Corey Farrell
6b138046e7 core: Add digit filtering to ast_waitfordigit_full
This adds a parameter to ast_waitfordigit_full which can be used to only
stop waiting when certain expected digits are received.  Any unexpected
DTMF digits are simply ignored.

This also creates a new dialplan application WaitDigit.

ASTERISK-27129 #close

Change-Id: Id233935ea3d13e71c75a0861834c5936c3700ef9
2017-07-12 19:08:23 -04:00
Joshua Colp
7f09fd2c2f bridge/core_unreal: Fix SFU bugs with forwarding frames.
This change fixes a few things uncovered during SFU testing.

1. Unreal channels incorrectly forwarded video frames when
no video stream was present on them. This caused a crash when
they were read as the core requires a stream to exist for the
underlying media type. The Unreal channel will now ensure a
stream exists for the media type before forwarding the frame
and if no stream exists then the frame is dropped.

2. Mapping of frames during bridging from the stream number of
the underlying channel to the stream number of the bridge was
done in the wrong location. This resulted in the frame getting
dropped. This mapping now occurs on reading of the frame from
the channel.

3. Bridging was using the wrong ast_read function resulting in
it living in a non-multistream world.

4. In bridge_softmix when adding new streams to existing channels
the wrong stream topology was copied resulting in no streams
being added.

Change-Id: Ib7445722c3219951d6740802a0feddf2908c18c8
2017-07-11 23:47:32 +00:00
Jenkins2
d6c08cc559 Merge "core: Remove 'Data Retrieval API'" 2017-07-07 15:42:56 -05:00
George Joseph
7a306468f4 Merge "bridge_native_rtp: Keep rtp instance refs on bridge_channel" 2017-07-05 17:03:28 -05:00
Sean Bright
325eeced6a core: Remove 'Data Retrieval API'
This API was not actively maintained, was not added to new modules
(such as res_pjsip), and there exist better alternatives to acquire the
same information, such as the ARI.

Change-Id: I4b2185a83aeb74798b4ad43ff8f89f971096aa83
2017-07-05 11:25:58 -05:00
Torrey Searle
fb7247c57c res_pjsip: Add DTMF INFO Failback mode
The existing auto dtmf mode reverts to inband if 4733 fails to be
negotiated.  This patch adds a new mode auto_info which will
switch to INFO instead of inband if 4733 is not available.

ASTERISK-27066 #close

Change-Id: Id185b11e84afd9191a2f269e8443019047765e91
2017-06-29 07:57:01 -06:00
Mark Michelson
45df25a579 chan_pjsip: Add support for multiple streams of the same type.
The stream topology (list of streams and order) is now stored with the
configured PJSIP endpoints and used during the negotiation process.

Media negotiation state information has been changed to be stored
in a separate object. Two of these objects exist at any one time
on a session. The active media state information is what was previously
negotiated and the pending media state information is what the
media state will become if negotiation succeeds. Streams and other
state information is stored in this object using the index (or
position) of each individual stream for easy lookup.

The ability for a media type handler to specify a callback for
writing has been added as well as the ability to add file
descriptors with a callback which is invoked when data is available
to be read on them. This allows media logic to live outside of
the chan_pjsip module.

Direct media has been changed so that only the first audio and
video stream are directly connected. In the future once the RTP
engine glue API has been updated to know about streams each individual
stream can be directly connected as appropriate.

Media negotiation itself will currently answer all the provided streams
on an offer within configured limits and on an offer will use the
topology created as a result of the disallow/allow codec lines.

If a stream has been removed or declined we will now mark it as such
within the resulting SDP.

Applications can now also request that the stream topology change.
If we are told to do so we will limit any provided formats to the ones
configured on the endpoint and send a re-invite with the new topology.

Two new configuration options have also been added to PJSIP endpoints:

max_audio_streams: determines the maximum number of audio streams to
offer/accept from an endpoint. Defaults to 1.

max_video_streams: determines the maximum number of video streams to
offer/accept from an endpoint. Defaults to 1.

ASTERISK-27076

Change-Id: I8afd8dd2eb538806a39b887af0abd046266e14c7
2017-06-28 18:36:29 +00:00
George Joseph
80e11bd79b bridge_native_rtp: Keep rtp instance refs on bridge_channel
There have been reports of deadlocks caused by an attempt to send a frame
to a channel's rtp instance after the channel has left the native bridge
and been destroyed.  This patch effectively causes the bridge channel to
keep a reference to the glue and both the audio and video rtp instances
so what gets started will get stopped.

ASTERISK-26978 #close
Reported-by: Ross Beer

Change-Id: I9e1ac49fa4af68d64826ccccd152593cf8cdb21a
2017-06-27 11:20:36 -05:00
Kevin Harwell
27dae55fb6 core_local: local channel data not being properly unref'ed and unlocked
In an earlier version of Asterisk a local channel [un]lock all functions were
added in order to keep a crash from occurring when a channel hung up too early
during an attended transfer. Unfortunately, when a transfer failure occurs and
depending on the timing, the local channels sometime do not get properly
unlocked and deref'ed after being locked and ref'ed. This happens because the
underlying local channel structure gets NULLed out before unlocking.

This patch reworks those [un]lock functions and makes sure the values that get
locked and ref'ed later get unlocked and deref'ed.

ASTERISK-27074 #close

Change-Id: Ice96653e29bd9d6674ed5f95feb6b448ab148b09
2017-06-21 16:18:13 -05:00
George Joseph
3f5bf287a2 Merge "SDP: Add get/set option calls for RTP sched context per type." 2017-06-19 09:27:43 -05:00
Jenkins2
317234bdc6 Merge "res_pjsip: New endpoint option "notify_early_inuse_ringing"" 2017-06-19 09:09:58 -05:00
Jenkins2
d81293a5dd Merge changes from topic 'sdp_api_adjustments'
* changes:
  SDP: Set the remote c= line in RTP instance.
  SDP: Add t= line in sdp_create_from_state()
  stream: Ignore declined streams for some topology calls.
2017-06-16 11:51:41 -05:00
Jenkins2
2f684eb6a5 Merge "stream: Add ast_stream_topology_del_stream() and unit test." 2017-06-16 11:50:32 -05:00
Alexei Gradinari
7a46309d3d res_pjsip: New endpoint option "notify_early_inuse_ringing"
This option was added to control whether to notify dialog-info state
'early' or 'confirmed' on Ringing when already INUSE.
The value "yes" is useful for some SIP phones (Cisco SPA)
to be able to indicate and pick up ringing devices.

ASTERISK-26919 #close

Change-Id: Ie050bc30023543c7dfb4365c5be3ce58c738c711
2017-06-16 11:25:07 -05:00
George Joseph
1ac0096512 res_ari: Add "module loaded" check to ari stubs
The recent change to make the use of LOAD_DECLINE more consistent
caused res_ari to unload itself before declining if the ari.conf
file wasn't found.  The ari stubs though still tried to use the
configuration resulting in segfaults.

This patch creates a new CHECK_ARI_MODULE_LOADED macro which tests
to see if res_ari is actually loaded and causes the stubs to also
decline if it isn't.  The macro was then added to the mustache
template's "load_module" function.

ASTERISK-27026 #close
Reported-by: Ronald Raikes

Change-Id: I263d56efa628ee3c411bdcd16d49af6260c6c91d
2017-06-15 19:34:03 -05:00
Joshua Colp
1f2ab6e72a Merge "bridge: Add a deferred queue." 2017-06-15 15:02:26 -05:00
Richard Mudgett
e563a1920e SDP: Add get/set option calls for RTP sched context per type.
Change-Id: I82dc75c63c48904e9e5a49e2205dcc06e88487e4
2017-06-15 09:42:15 -05:00
Richard Mudgett
a95584d079 SDP: Set the remote c= line in RTP instance.
Change-Id: I23b646392082deab65bedeb19b12dcbcb9216d0c
2017-06-15 09:42:15 -05:00
Richard Mudgett
06265b8c8a stream: Add ast_stream_topology_del_stream() and unit test.
Change-Id: If07e3c716a2e3ff85ae905c17572ea6ec3cdc1f9
2017-06-15 09:42:15 -05:00
Richard Mudgett
4797a8bb81 stream: Ignore declined streams for some topology calls.
* Made ast_format_cap_from_stream_topology() not include any formats from
declined streams.

* Made ast_stream_topology_get_first_stream_by_type() ignore declined
streams to return the first active stream of the type.

* Updated unit tests to check these changes have the expected effect.

Change-Id: Iabbc6a3e8edf263a25fd3056c3c614407c7897df
2017-06-15 09:42:15 -05:00
Joshua Colp
d6386a8f0c bridge: Add a deferred queue.
This change adds a deferred queue to bridging. If a bridge
technology determines that a frame can not be written and
should be deferred it can indicate back to bridging to do so.
Bridging will then requeue any deferred frames upon a new
channel joining the bridge.

This change has been leveraged for T.38 request negotiate
control frames. Without the deferred queue there is a race
condition between the bridge receiving the T.38 request
negotiate and the second channel joining and being in the
bridge. If the channel is not yet in the bridge then the T.38
negotiation fails.

A unit test has also been added that confirms that a T.38
request negotiate control frame is deferred when no other
channel is in the bridge and that it is requeued when a new
channel joins the bridge.

ASTERISK-26923

Change-Id: Ie05b08523f399eae579130f4a5f562a344d2e415
2017-06-13 17:06:15 -05:00