Kamailio: SIP over WebSockets

There are a lot of really interesting things happening in the world of telecoms today.  One of the coolest is the work the IETF is doing on RTCWeb - that is media (audio and video) sessions between web-browsers without needing plugins.

RTCWeb is going to be a great enabler for all sorts of new types of web application (many of which haven't even been imagined yet) - but RTCWeb only focusses on the media part of communication.  In a lot of cases (particularly if telephony features or integration are required) the media alone isn't enough.  To this end Inaki Baz Castillo, Jose Luis Millan Villegas, and Victor Pascual have been working on an IETF draft, "The WebSocket Protocol as a Transport for the Session Initiation Protocol (SIP)" (draft-ietf-sipcore-sip-websocket-03).

There are now a number of implementations of SIP over WebSockets.  Servers include Asterisk, Kamailio, Mobicents SIP Servlets, OverSIP, and Repro/webrtc2sip.  Clients include jsSIP and sipML5.  This is not bad for a draft.

The Kamailio implementation of SIP over WebSockets (supporting both WebSockets (ws) and Secure WebSockets (wss)) has been available in the master branch of the SIP Router Git repository since early July 2012.  A number of people have tried using this and, aside from some configuration related issues, it appears to be working well.  I have tested (and seen others test) the Kamailio implementation with both the jsSIP and sipML5 clients.

If you want to try SIP over WebSockets, and you want to use it with a SIP server that supports lots of rich features (including scripting in Lua/Mono/Perl/Python, presence server, offline instant message handling, load-balancing, least-cost-routing, and far too many other things to list), Kamailio is an excellent place to start - there is even an example configuration file for SIP over WebSockets that is ready to go.

Updating the kernel on Fedora 17 for Raspberry Pi

I've been playing around with Fedora 17 on the Raspberry Pi for a while.  There are excellent nightly images available from http://scotland.proximity.on.ca/arm-nightlies/, but these have an old version of the 3.1.9 Raspberry Pi kernel.

I have had a few problems with this old kernel including:

• My fast (8 GB SanDisk Extreme Pro (class 10, 95 MB/s)) SD cards don't work - and the class 4 cards are just too slow for certain jobs.
• Lots of these sort of errors:
  DEBUG_ timer_callback:: Timer hc timer callback
  WARN:: hc_xfer_timeout:1740: hc_xfer_timeout: timeout on channel 5
  WARN:: hc_xfer_timeout:1742 start_hcchar_val 0x00d88a00
• Lots of these kind of errors when the root partition is on a class 4 card:
  mcc0: note - long write synce 1350000ns - 13603 its.

So tonight I decided to upgrade the kernel following the instructions from this thread http://www.raspberrypi.org/phpBB3/viewtopic.php?f=51&t=8250 (post dated 2012-06-13 9:37am).

So far this has worked brilliantly.  The errors are gone and I can use my fast SD cards now.

Kamailio for Raspberry Pi

I have recently build some RPMs of Kamailio 3.3.0-pre3 (as of yesterday) including for the Raspberry Pi (running Fedora 17).

I haven't done much testing with these yet, but if anyone wants to try them I have put them in my yum repo: http://dl.dropbox.com/u/9300853/yum/index.html

Air Video Server for Linux on Fedora 17

One of the things that stopped working when I upgraded to Fedora 17 was Air Video Server for Linux.  Fortunately, this is a quick fix - I needed to rebuild FFMpeg (step 4 in my previous procedure).

Unfortunately, the version of FFMpeg needed for Air Video Server Linux doesn't compile on Fedora 17 - but this was easy to fix.  So, if you are upgrading to Fedora 17 simply rebuild and install FFMpeg (step 4 in my previous procedure) following the instructions below.  If you have a new installation of Fedora 17 my previous procedure will mostly work but you should replace step 4 with the instructions below.


tar jxvf ffmpeg-for-2.4.5-beta6.tar.bz2
cd ffmpeg/libavcodec/x86
rm h264_qpel_mmx.c
wget http://dl.dropbox.com/u/9300853/AirVideoLinux-alpha6/h264_qpel_mmx.c
cd ../..
./configure --enable-pthreads --disable-shared --enable-static \
  --enable-gpl --enable-libx264 --enable-libmp3lame
make all
[sudo] make install
cd ..


Updated: Mon 4 Jun 2012 00:04

Upgrading to Fedora 17

I upgraded both of my Fedora 16 systems to Fedora 17 today.  I was, unfortunately, affected by four similar, but separate, grub2 bugs.  For those who don't know, grub2 is the bootloader used in Fedora and - if it goes badly wrong you can end up with a system that won't boot.

The four problems I had were:

1. Whenever a new kernel is installed I get the error: "grubby fatal error: unable to find a suitable template"
2. When the computer boots grub2 reports "error: file '/boot/grub2/locale/en.mo.gz' not found"
3. When the computer boots I get a "signal out of range" error on my monitor, and on fixing this
4. grub2 prints "error: file not found" three times after starting to boot

The fix to these issues is simple:

# vim /etc/default/grub (add the line GRUB_TERMINAL_OUTPUT=console to the end of the file)

# grub2-mkconfig -o /boot/grub2/grub.cfg
# grub2-install /dev/sda (replace /dev/sda with the device your bootloader is installed on)

If (like me) you are paranoid you can check the fixes by reinstalling the kernel (as long as you haven't restarted your machine and are still running the old kernel) and making sure there are no errors reported:

# yum reinstall kernel


Updated: Sun 3 Jun 2012 11:53

Raspberry Pi compiling and development on Fedora 17

My last post explained how to run Fedora 17 on the Raspberry Pi.  An SD card is OK to run software from, but it is not the best configuration for doing things (like compiling software) that involve lots of random "disk" reads and writes.

If you are going to be compiling lots software it makes sense to use a USB hard-drive.  This guide explains how to boot Fedora 17 from an SD card (the Raspberry Pi must boot from an SD card) but run the root file-system from a USB hard-drive.

In addition to the assumptions in my last post, I am assuming:

• Your USB hard-drive is /dev/sdb when connected to your computer.   If your USB hard-drive is on a different device file then make sure you work out what it is and use the right file-name in the instructions below - getting this wrong could permanently lose data.

Complete steps 1 and 2 from my last post before continuing here:

1. Delete the unnecessary root filesystem from the SD card:
   # fdisk /dev/mmcblk0 (commands I entered and comments in bold below)
   
   Command (m for help): d
   Partition number (1-4): 2Command (m for help): w
   The partition table has been altered!
   
   Calling ioctl() to re-read partition table.
   Syncing disks.
2. Update the SD card so that the Raspberry Pi looks for the root file-system on a USB hard-drive:
   # mkdir /tmp/boot_pi
   # mount /dev/mmcblk0p1 /tmp/boot_pi
   # vim /tmp/boot_pi/cmdline.txt (change root=/dev/mmcblk0p2 to root=/dev/sda2 - this really is /dev/sda here as that is how it will appear on the Raspberry Pi)
   # umount /tmp/boot_pi
   # rmdir /tmp/boot_pi
3. Connect the USB hard-drive to your computer (unmount it if your computer automounts it for you) and write the image to the hard-drive:
   # xzcat f17arm-latest-arm-rpi-mmcblk0.img.xz > /dev/sdb
4. Delete the unnecessary boot partition from the hard-drive and resize the root file-system:
   # fdisk /dev/sdb (commands I entered and comments in bold below)
   
   Command (m for help): p
   
   Disk /dev/sdb: 80.0 GB, 80026361856 bytes
   81 heads, 63 sectors/track, 30629 cylinders, total 156301488 sectors
   Units = sectors of 1 * 512 = 512 bytes
   Sector size (logical/physical): 512 bytes / 512 bytes
   I/O size (minimum/optimal): 512 bytes / 512 bytes
   Disk identifier: 0x00000000
   
      Device Boot      Start         End      Blocks   Id System
   /dev/sdb1   *          63     1044224      522081    c  W9...
   /dev/sdb2         1044225     7784447     3370111+  83  Linux
   
   Command (m for help): d
   Partition number (1-4): 2
   
   Command (m for help): n
   Partition type:
      p   primary (1 primary, 0 extended, 3 free)
      e   extended
   Select (default p): p
   Partition number (1-4, default 2): 2
   The first sector must be the start sector of /dev/sdb2 (above).  This number may be different on your hard-drive.  It should be the default value here - but check it carefully anyway.
   First sector (1044225-156301488, default 1044225): 1044225
   The last sector should be the default if you want to use all available space on the hard-drive.  If the default is what you want just press return.
   Last sector, +sectors or +size{K,M,G} (1044225-156301488, default 156301488):
   Using default value 156301488
   
   Command (m for help): d
   Partition number (1-4): 1
   
   Command (m for help): w
   The partition table has been altered!
   
   Calling ioctl() to re-read partition table.
   Syncing disks.
   # e2fsck -f /dev/sdb2
   # resize2fs /dev/sdb2
   # mkdir /tmp/rootfs_pi
   # mount /dev/sdb2 /tmp/rootfs_pi
   # rm -f /tmp/rootfs_pi/etc/systemd/system/multi-user.target.wants/rootfs-resize.service
   # umount /tmp/rootfs_pi
   # rmdir /tmp/rootfs_pi
5. Now eject the SD card from your reader and disconnect your USB hard-drive, put the SD card in your Raspberry Pi and connect the USB hard-drive and power up.  Once it has booted log in as "root" using the password "fedoraarm".  (Assuming that you are connected over a wired LAN with a DHCP server) the Raspberry Pi will automatically obtain an IP address and LAN settings (I am going to assume this is the case - if not the process for configuring networking is exactly the same as it is on any other Fedora 17 machine).
6. Update your packages:
   # yum update
   
   Don't worry about the fact that a new kernel is installed - even though this new kernel is not Raspberry Pi compatible.  When a new kernel is installed using "yum update" the old one (and it's modules) are not removed.  Also, because of the way the UBOOT partition in the images works, installing a new kernel does not change the default kernel used when you boot.

Job done.  You now have a perfectly usable and up-to-date Fedora 17 Raspberry Pi SD card and USB hard-drive combination.

Fedora 17 on Raspberry Pi

I received my Raspberry Pi this week and set about installing Fedora, my operating system of choice, on it.  Unfortunately, Fedora 14 is regarded as unstable on the Raspberry Pi and Fedora 17 isn't quite ready for it yet.

However, there are some very good nightly snapshots of Fedora 17 (http://scotland.proximity.on.ca/arm-nightlies/) for Raspberry Pi available.  I thought I would put together a short guide on using these.

This guide assumes:

• You are logged in as root on a Linux computer
• Your SD card is /dev/mmcblk0 when inserted into your SD card reader.  If your SD card is on a different device file then make sure you work out what it is and use the right file-name in the instructions below - getting this wrong could permanently lose data.

The first thing to do is to select the image you want to install.  The nightly builds come in three flavours:

1. Console only (this is the one I use and referred to in the rest of the instructions)
2. Minimal X Windows
3. XFCE

Once you have chosen your image the process is:

1. Download the software (replace the URL here with the one for the image you have selected):
   # wget http://scotland.proximity.on.ca/arm-nightlies/vault/f17arm-latest-arm-rpi-mmcblk0.img.xz
2. Insert your SD card (unmount it if your computer automounts it for you) and write the image to the card:
   # xzcat f17arm-latest-arm-rpi-mmcblk0.img.xz > /dev/mmcblk0
3. When your Raspberry Pi boots this image for the first time it will resize the root file-system to use up the whole card.  Waiting for this is tedious and it gets in the way of using your Raspberry Pi right away.  Fortunately, on a Linux PC, you can do this manually (and quickly):
   # fdisk /dev/mmcblk0 (commands I entered and comments in bold below)
   
   Command (m for help): p
   
   Disk /dev/mmcblk0: 7822 MB, 7822376960 bytes
   4 heads, 16 sectors/track, 238720 cylinders, total 15278080 sectors
   Units = sectors of 1 * 512 = 512 bytes
   Sector size (logical/physical): 512 bytes / 512 bytes
   I/O size (minimum/optimal): 512 bytes / 512 bytes
   Disk identifier: 0x00000000
   
           Device Boot      Start         End      Blocks   Id  System
   /dev/mmcblk0p1   *          63     1044224      522081    c  W9...
   /dev/mmcblk0p2         1044225     7784447     3370111+  83  Linux
   
   Command (m for help): d
   Partition number (1-4): 2
   
   Command (m for help): n
   Partition type:
      p   primary (1 primary, 0 extended, 3 free)
      e   extended
   Select (default p): p
   Partition number (1-4, default 2): 2
   The first sector must be the start sector of /dev/mmcblk0p2 (above).  This number may be different on your SD card.  It should be the default value here - but check it carefully anyway.
   First sector (1044225-15278079, default 1044225): 1044225
   The last sector should be the default if you want to use all available space on the SD card.  If the default is what you want just press return.
   Last sector, +sectors or +size{K,M,G} (1044225-15278079, default 15278079):
   Using default value 15278079
   
   Command (m for help): w
   The partition table has been altered!
   
   Calling ioctl() to re-read partition table.
   Syncing disks.
   # e2fsck -f /dev/mmcblk0p2
   # resize2fs /dev/mmcblk0p2
   # mkdir /tmp/rootfs_pi
   # mount /dev/mmcblk0p2 /tmp/rootfs_pi
   # rm -f /tmp/rootfs_pi/etc/systemd/system/multi-user.target.wants/rootfs-resize.service
   # umount /tmp/rootfs_pi
   # rmdir /tmp/rootfs_pi
4. Now eject the SD card from your reader, put it in your Raspberry Pi and power up.  Once it has booted log in as "root" using the password "fedoraarm".  (Assuming that you are connected over a wired LAN with a DHCP server) the Raspberry Pi will automatically obtain an IP address and LAN settings (I am going to assume this is the case - if not the process for configuring networking is exactly the same as it is on any other Fedora 17 machine).
5. Update your packages:
   # yum update
   
   Don't worry about the fact that a new kernel is installed - even though this new kernel is not Raspberry Pi compatible.  When a new kernel is installed using "yum update" the old one (and it's modules) are not removed.  Also, because of the way the UBOOT partition in the images works, installing a new kernel does not change the default kernel used when you boot.

Job done.  You now have a perfectly usable and up-to-date Fedora 17 Raspberry Pi SD card.