Asterisk behind Kamailio & Voicemail MWI

Once again my workaholic nature didn't let me rest this Saturday and Sunday as I kept thinking about how can the MWI indications work with Asterisk as voicemail server behind a Kamailio server. Kamailio is the REGISTRAR of SIP users.

Since SIP users register on Kamailio, so Asterisk won't trigger a NOTIFY on it's voice-message recording.

There are many methods discussed on voip-info.org page. Among the other which weren't working or required patching I worked on manual SUBSCRIBE-NOTIFY triggering method by "Andreas Granig" which is openly discussed and shared on this mailing-list post in 2004. I haven't modified anything except the IP addresses for my servers.

Since a picture is worth a thousand words so see the attached image below for the logical flow of the solution.

Kamailio and Asterisk with MWI working

Since the time the solution was posted a lot of things have changed with SER and Kamailio. I am using Kamailio 3.3 so I had to change a few variables and minor things to make this work for me.

In Kamialio configurations File

if (is_method("NOTIFY") & ds_is_from_list()) {
                route(LOCATION);
                if (!t_relay()) {
                        sl_reply_error();
                        break;
                };
};

if (method=="SUBSCRIBE") {
        # challenge/response
                if (!www_authorize("$td", "asv_sip")) {
                        www_challenge("$td", "0");
                        break;
                };
        # notify the Asterisk server to update the UAs MWI. I
        # believe most UAs that support SUBSCRIBE will
        # periodically send a SUBSCRIBE message. These cause
        # the Asterisk server to update their MWI.
            
   exec_avp("subscribe sip:$rU@192.168.2.181","$avp(s:test)");
                           sl_send_reply("200","OK");
                break;
};

where subscribe is a scrip placed in directory /usr/bin/mwi 
A symbolic link of the subscribe script is created in /usr/sbin directory as well.

subscribe

--------------------------------

#!/bin/sh

# this script simply accepts as input the subscriber URI such

# as sip:1001 at sip01.mycompany.com and "touches" a file with the

# same name. It stores the file in /var/spool/mwi/immediate

# which is later processed in a CRON job

USER=$1

# some input arguments may contain ";user=phone" so we need to

# strip it off. We also need to strip of the "sip:" piece so that

# all we are left with is "1001 at sip.mycompany.com"

IDX1=`expr index "$1" ":"`

IDX1=$(($IDX1 + 1))

IDX2=`expr index "$1" ";"`

if [ $IDX2 != 0 ]; then

  IDX2=$(($IDX2 - $IDX1))

  USER=`expr substr $1 $IDX1 $IDX2`

fi

if [ $IDX2 = 0 ]; then

  USER=`expr substr $1 $IDX1 80`

fi

echo "touch /var/spool/mwi/$USER"

touch /var/spool/mwi/$USER

--------------------------------

Once this scripts create a file for the user requesting Voicemail Notify the next script cron-subscribe transports the username to the Asterisk server which is saving the voicemails for that user. The subscribe and the cron-subcribe scripts can be merged into just one script as well.


cron-subscribe

--------------------------------

#!/bin/sh


# this script uses scp to copy the files from /var/spool/mwi/immediate
# to the Asterisk server. It is important to note that the scp works
# without being prompted for a password.
MSG_HOME=/var/spool/mwi
VM_HOME=/var/spool/mwi/immediate
for file in $MSG_HOME/*
do
  if [ -f $file ]; then
        echo $file
    scp $file 192.168.2.86:$VM_HOME
    rm -f $file
  fi
done

--------------------------------

Don;t forget to create the directory:

root#mkdir -p /var/spool/mwi/

Set in cronjob

* * * * * /usr/bin/mwi/cron-subscribe

IN ASTERISK SERVER/VOICEMAIL DIRECTORY SERVER

root#yum install sipsak

Create the following scripts in Asterisk server directory ::  /usr/bin/mwi
Don't forget to change the IP addresses accordingly in your setup.

notify.msg

---------------------

NOTIFY sip:SUBSCRIBER SIP/2.0

Via: SIP/2.0/UDP 192.168.2.86:5060

Max-Forwards: 70

Route: <sip:SUBSCRIBER>

From: "VM-MWI" <sip:VM-MWI@192.168.2.86:5060>

To: <sip:SUBSCRIBER>

Contact: <sip:VM-MWI@192.168.2.86>

Call-ID: 29320a42d73ae512NWM4OTc4ODI0YmVlNjJkMjQ1MmJmYTYyOGFlNDMzY2Y.

CSeq: 103 NOTIFY

User-Agent: Vocemail-MWI Server

Event: message-summary

Content-Type: application/simple-message-summary

Subscription-State: active

Content-Length: CONTENT_LENGTH

Messages-Waiting: HAS_MESSAGE

Message-Account: sip:*97@mysipserver.mycompany.com

Voice-Message: NEW_COUNT/OLD_COUNT (0/0)

-----------------------

notify.msg is the sample file which will get called in cron-mwi-immediate file and all variables will be replaced there and this NOTIFY will be sent out to Kamailio server.

mwi-immediate

-----------------------

#!/bin/sh

# this script "touches" files in the spool directory which a

# cron jobs later processes. The cron job is where we actually

# send the SIP NOTIFY back to the UAs

CONTEXT=$1

EXTENSION=$2

VM_COUNT=$3

touch /var/spool/mwi/immediate/$EXTENSION

-------------------

mwi-immediate script is used from within the dialplan. Once we receive a voicemail we can execute this script from asterisk dialplan to send out a NOTIFY after receiving the message.

cron-mwi-immediate

-------------------

#!/bin/sh

# This script sends the SIP NOTIFY message to UAs. The NOTIFY message

# can either enable or disable the UA message indicator. The script

# looks for any file in $VM_HOME and creates the NOTIFY message via

# the template in $TEMPLATE.

#

# The actual NOTIFY message is sent to the SIP proxy by the sipsak

# utilty. After the message is send we delete the processed file

# from VM_HOME so we don't keep resending the same message. Most

# UAs will periodically send a SUBSCRIBE message to the SIP proxy.

# When this occurs the SIP proxy will place a file in the location

# /var/spool/mwi/delay and a less frequent CRON job will process it.

                                                                        #

# ALSO NOTE: I am not using the Asterisk "telnet API". I can't

# remember what it's called, but I think looking for voice mail

# files on disk is quicker. I do not know if this is 100% safe since

# I am totally bypassing Asterisk in order to determine if a user has

# new voice mail messages. Can anyone verify this as a good way to

# handle this?

VM_ROOT=/var/spool/asterisk/voicemail/default

VM_HOME=/var/spool/mwi/immediate

TEMPLATE=/usr/bin/mwi/notify.msg

cd $VM_HOME

for file in *

do

        #echo $file

        LEN=`expr length $file`

        IDX1=`expr index "$file" \@`

        IDX2=$(($IDX1 + 1))

        IDX1=$(($IDX1 - 1))

        MAILBOX=`expr substr $file 1 $IDX1`

        DOMAIN=`expr substr $file $IDX2 $LEN`

        TOTAL_MESSAGES=`find $VM_ROOT/$MAILBOX -name "*.txt" |

                        wc -l | sed 's/^ *\(.*\) *$/\1/'`

#       echo $TOTAL_MESSAGES

        NEW_MESSAGES=`find $VM_ROOT/$MAILBOX/INBOX -name "*.txt" |

                        wc -l | sed 's/^ *\(.*\) *$/\1/'`

        #echo $NEW_MESSAGES

        OLD_MESSAGES=$(($TOTAL_MESSAGES - $NEW_MESSAGES))

        #echo $OLD_MESSAGES

        if [ "$NEW_MESSAGES" == "0" ]; then

                HAS_NEW="no"

        else

                HAS_NEW="yes"

        fi

        CONTENT_LENGTH=$((84 + `expr length $HAS_NEW` +

                               `expr length $NEW_MESSAGES` +

                               `expr length $OLD_MESSAGES`))

        #echo $CONTENT_LENGTH

        CMD="s/SUBSCRIBER/$file/g;s/MAILBOX/$MAILBOX/g;s/CONTENT_LENGTH/$CONTENT_LENGTH/g;s/HAS_MESSAGE/$HAS_NEW/g;s/NEW_COUNT/$NEW_MESSAGES/g;s/OLD_COUNT/$OLD_MESSAGES/g"

        cat /usr/bin/mwi/notify.msg | sed -e $CMD > /tmp/mwi-immediate

        #echo "Notifying $file"

        `sipsak shoot -a number4 -f /tmp/mwi-immediate -s sip:$file`

       rm $file

done

----------------------------------------------------

This cron-mwi-immediate is the heart of the logic. This script search the directories of the required user and if there are newer messgaes waiting then it takes in the file "notify.msg" and fill in the variables accordingly and shoot out the NOTIFY towards the Kamailio server.

This NOTIFY is already handled in kamailio configuration.

root#mkdir -p /var/spool/mwi/immediate

Set in crontab
 * * * * /usr/bin/mwi/cron-mwi-immediate

Thats all... now you'r MWI should work. :)

Hope this was a helpful post for the needy one's.

REF LINK: http://lists.iptel.org/pipermail/serusers/2004-September/011552.html
http://www.voip-info.org/wiki/view/Asterisk+at+large