Thursday, November 17, 2016

GNU Gatekeeper 4.3 released

I'm happy to announce the release of GNU Gatekeeper 4.3.

This new version contains a number bug fixes and some security fixes.

Fuzzy testing surfaced methods to crash GnuGk remotely, causing at least a denial of service. So all users are encouraged to update.

The most notable new feature are probably the events for Setup messages on the status port so now you can see all calls. In addition, LuaAuth has been given access to more information about received messages and can end your status port sessions with Ctrl-C now.

Important bug fixes are in the H.460 NAT traversal code where sometimes keep-alive intervals could be too long in older versions and a bug where GnuGk might have missed port re-negotiations in some cases.

The IgnoreSignaledIPs port detection code also has a few bug fixes to detect cases where it should be turned off automatically because its either not needed because the parties use another form of NAT traversal or non-symmetric ports where the detection algorithm may cause more harm than good.

You can download the new version from


Changes from GnuGk 4.2 to 4.3
  • BUGFIX(ProxyChannel.cxx, gkh235.cxx, gkauth.h) fix crashes found with PROTOS
  • new authentication policies LuaPasswordAuth, HttpPasswordAuth
  • BUGFIX( fix check for LUA 5.2 or higher
  • connection to the status port can now also be ended with Ctrl-C
  • new switch [Routing::DNS] RewriteARQDestination= to preserve URLs in ARQs
  • disable IgnoreSignaledIPs when one party is not using the same RTP ports for forward and reverse channels in same RTP session
  • BUGFIX(RasTbl.cxx) don't allow higher TTL for H.460.18 registrations  than set by H46018KeepAliveInterval= switch
  • add variables message, srcInfo and vendor to LuaAuth
  • print message on status port when Setup is received
  • BUGFIX(ProxyChannel.cxx) disregard IgnoreSignaledIPs=1 switch when caller supports some form of NAT traversal (to avoid both sides waiting for first RTP packet)
  • BUGFIX(ProxyChannel.cxx) enable H.245 tunneling for H.460.17 even when Innovaphone forgets the flag
  • BUGFIX(ProxyChannel.cxx) make sure CRV is 0 for all RAS messages when using H.460.17 even when they relate to a call
  • BUGFIX(ProxyChannel.cxx) re-do H.460.19 port detection when a new logical channel is opened on the same port
  • print number of CPU cores and thread configuration on startup
  • BUGFIX(RasTbl.cxx) fix display of H.460.17 for registrations on status port
  • BUGFIX(ProxyChannel.cxx) fix dead lock causing reroutes to fail

Saturday, October 8, 2016

Mobile H.323 endpoints revisited

If you are looking for a free H.323 endpoint to connect to the GNU Gatekeeper, mobile apps for smartphones and tablets seem to offer the widest variety of choice right now.


My personal favorite are the RealPresence apps from Polycom, available  for iOS and Android. They offer you to sign in with a Polycom account, but you can simply skip this and just register with any H.323 gatekeeper in the settings.


Collaborate Mobile is also a good choice and also available for iOS and Android from the respective app stores.


Yealink VC Mobile is relatively new, but seems to work find with GnuGk, too.


There used to be an Android version of BeedHD, but now its only available for iOS.

I have dropped Sony IPELA from the list, because their apps seem to hang up without any visible reason after a few seconds in the call.

Here is my older post about free mobile H.323 endpoints for reference.

Wednesday, June 1, 2016

GNU Gatekeeper 4.2

I'm happy to announce the release of GNU Gatekeeper 4.2.

Version 4.2 is mainly a bug fix release.

A bug in proxying H.239 connections through NAT has been fixes as well
as a number of possible crashes and a few other small bugs.

The main functional change is that GnuGk's old NAT traversal method is
now disabled by default. Everybody should use H.460.x. If you want keep
using the old NAT traversal method, you can re-enable it with



You can download the new version from

Please see the full change log below.


Changes from 4.1 to 4.2
  • BUGFIX(ProxyChannel.cxx) fix H.239 forwarding issue in call where  only one side uses H.460.19
  • BUGFIX( make sure LUA test fails for versions below 5.2
  • BUGFIX(gkh235.cxx) small fix with password auth
  • BUGFIX(ProxyChannel.cxx) apply codec filtering also to  receiveAndTransmit capabilities
  • BUGFIX(ProxyChannel.cxx) fix crash in RTP multiplexing
  • BUGFIX(ProxyChannel.cxx) fix crash when using H.245 tunneling translation
  • BUGFIX(gk.cxx) fix shutdown on NetBSD 7
  • BUGFIX(ProxyChannel.cxx) fix compile on NetBSD 7
  • new switch: [RoutedMode] FilterVideoFastUpdatePicture= to reduce the  number of update requests from endpoints
  • disable SSLv3 when using TLS
  • BUGFIX(ProxyChannel.cxx) fix crash in call cleanup
  • support ON and OFF event in LuaAcct
  • BUGFIX(sqlacct.*) implement ON and OFF event as documented
  • new switches [RoutedMode] EnableGnuGkNATTraversal=1 and [Endpoint]  EnableGnuGkNATTraversal=1 to keep GnuGk's old NAT traversal method enabled

Wednesday, February 17, 2016

GNU Gatekeeper 4.1

I'm happy to announce the availability of GNU Gatekeeper 4.1.

This is mainly a bug fix release. If you are using GnuGk as a server in
a traversal zone or if you do H.239 presentations with Avaya endpoints,
you are strongly encouraged to update. This version also fixes a memory
leak that mainly affects long running gatekeepers with a lot of RAS
traffic. Some of the bugs were long standing, so if you skipped some
previous releases, this is really a good time to update.

The main new feature in this release is expanded LUA support.
Besides LUA authentication and LUA routing, there is now a LuaAcct
module that allows you to run a script on every accounting event of your
choice. Please see the updated manual for details.

You can download the new version from

Please see the full change log below.

My support website also got a face lift.
Please check it out as well.


Changes from 4.0 to 4.1

  • BUGFIX(ProxyChannel.cxx) fix crash processing Setup
  • BUGFIX(RasSrv.cxx) update IP/port of traversal neighbor on every SCI,  not only on IP changes
  • new status port command: PrintNeighbors
  • BUGFIX(ProxyChannel.cxx) fix H.239 inside multiplePayloadStream from  Avaya XT5000 with H.460.19
  • new accounting module: LuaAcct
  • LUA: new library "gnugk" to allow access to GnuGk functionality
  • BUGFIX(configure) set all detected options in gnugkbuildopts.h on Unix
  • BUGFIX(ProxyChannel.cxx) removing H.235 capabilities might have skipped items
  • BUGFIX(lua.cxx) initialize all LUA variables for LUA routing
  • status port configuration (MaxStatusClients, StatusEventBacklog, StatusEventBacklogRegex) now changable at runtime
  • BUGFIX(GkStatus.cxx) fix StatusEventBacklogRegex for patterns that start at the beginning of the event line
  • BUGFIX(ProxyChannel.cxx) use RealPresence Group 0-Byte keep-alive for IgnoreSignaledH239PrivateIPs (needs LARGE_FDSET to work)
  • new switches to set database connect and read timeout (only used by  MySQL for now)
  • new switch to set worker thread idle timeout: [Gatekeeper::Main] WorkerThreadIdleTimeout=
  • BUGFIX(gk.cxx) better test for gatekeeper shutdown
  • BUGFIX(Routing.cxx) fix fromIP for ARQ and LRQ RouteRequests
  • BUGFIX(gkauth.cxx) only call Q.931 checks when activated
  • BUGFIX(Routing.cxx) fix RouteRequest from unregistered caller who  doesn't provide any alias
  • new switch: [RoutedMode] DisableSettingUDPSourceIP=1

Friday, January 29, 2016

Getting H.323 through Firewalls and NAT by using the free GNU Gatekeeper

The H.323 protocol places IP numbers inside the signaling messages and establishes multiple TCP and UDP connections for a single call. You can't even be sure beforehand of the direction in which some of these connections are established. This makes it harder to get
H.323 through a NAT than other protocols.

To get through firewalls and NATs, the GNU Gatekeeper supports a lot of different traversal methods and protocols. The combination of H.460.18 and H.460.19 (usually called "H.460 NAT traversal" for short) is by far the most common NAT traversal protocol and is supported by virtually all H.323 endpoints today.

The best approach is to place a GNU Gatekeeper on a public IP address in front of your firewall and enable H.460.18 NAT traversal. You don't have to open any inbound port - just allow outgoing connections in your firewall, which is usually the default anyway.

If not all of your endpoints support H.460.18 or if you have a lot of internal calls, you can place a 2nd GnuGk inside your firewall and let it tunnel calls out for all internal endpoints combined. This called a "traversal zone". See Chapter 10 in the GNU Gatekeeper manual how to configure the outside GnuGk as traversal server and the GnuGk inside the firewall as traversal client.

A simple, one gatekeeper configuration for NAT traversal looks like this:




Register all your endpoints with the gatekeeper, whether they are inside or outside the firewall, and you should be able to make calls in and out.