Manipulating SIP msg string

I am using a VoIP provider using SIP signalling for setup, i know that they restricted logins based on your user-agent string. Which means I have to use their hardware/softphone. I'm quite keen to run X-lite from xten on mac osx, or even kphone or similiar on linux, but as there any tool or way in linux i can manipulate the user-agent field string in the msgs? Thanks

First thing comes to mind is "netsed".

thanks unspawn. I download rpm for fedora core 4 version netsed 0.01b. I used the command to run it listening to udp port

netsed udp 5060 serveriphere 5060 's/kphone/X-Pro/1'
netsed 0.01b by Michal Zalewski <lcamtuf@ids.pl>[*] Parsing rule s/kphone/X-Pro/1...
[+] Loaded 1 rules...
[-] Error: cannot listen on the socket (strange)
netsed: exiting.

I find that it fails to listen to any udp ports, but i can listen to tcp ports...

any ideas why? are there any other progs like netsed that can do the job for me?

Error: cannot listen on the socket
Check w netstat: prolly your app to be using it for incoming requests. Choose different local port for rerouting through Netsed. If you can't redirect traffic, check README for transparent proxying.

Did you try your version to listen to any UDP port? Mine just doesnt work..so I checked his source code and found some parts of it were hard coded to use TCP functions..eg. using accept() instead of recvfrom() method for UDP. What version of netsed are you running if it works listening to any UDP port? So after changing the source code, this is what I'm getting:

./netsed udp 5060 someip 5060 s/3700/1600/1
netsed 0.01b by Michal Zalewski <lcamtuf@ids.pl>[*] Parsing rule s/3700/1600/1...
[+] Loaded 1 rules...
[+] Listening on port 5060/udp.
[+] Using fixed forwarding to someip:5060.
[+] Got incoming connection from 127.0.0.1:33211 to 127.0.0.1:33211[*] Forwarding connection to someip:5060
[-] Client or server disconnect (14168).
[+] Got incoming connection from 127.0.0.1:33211 to 127.0.0.1:33211[*] Forwarding connection to someip:5060
[-] Client or server disconnect (14211).
[+] Got incoming connection from 127.0.0.1:33211 to 127.0.0.1:33211[*] Forwarding connection to someip:5060
[-] Client or server disconnect (14215).

I'm going to double check if it actually replaces the strings in my rules.

Did you try your version to listen to any UDP port?
No.


Mine just doesnt work..so I checked his source code and found some parts of it were hard coded to use TCP functions..eg. using accept() instead of recvfrom() method for UDP.
Great. I'm sure Lcamtuf will accept your patch.