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symtex_22198's avatar
symtex_22198
Icon for Nimbostratus rankNimbostratus
Jul 23, 2009

modify SIP contact header param

Hi,

 

 

we are using a location server which basically gets SIP invites from a SIP proxy then sends 302 redirect messages.

 

 

I have been trying to modify the IP address parameter in the Contact header which is in the 302 message. this IP address will vary, but I want to set it statically

 

 

the contact header will have a URI in the format of number xxxxxxxxxxxxx@172.24.103.10. since this is my first irule. I'm struggling.

 

 

here is what I've been trying with no success.

 

 

when SIP_RESPONSE {

 

set contact [ SIP::header Contact ]

 

set telephone 0

 

set bind 0

 

regexp {[0-9]{13}} $contact telephone

 

regexp {[0-9]{8}} $contact bind

 

SIP::header insert [format \"$bind\"

 

 

the header just returns a 0 or a 1... maybe I should try the -inline switch with regexp???
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  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Jul 23, 2009
    Hi,

     

     

    What's the name and format of the value of the header you want to insert? Or do you just want to insert the 5060 port in the existing Contact header?

     

     

    I imagine you can check for the 302 response using 'SIP::response code' (Click here) and then use getfield (Click here) or scan (Click here) to parse the string without depending on the more resource intensive regexp command.

     

     

    Aaron
  • symtex_22198's avatar
    symtex_22198
    Icon for Nimbostratus rankNimbostratus
    Jul 23, 2009
    within a 302 SIP message is a "Contact" field

     

    The contact field will contain the redirected telephone in the format of a uri like this

     

    Contact: "16601003"

     

     

    I only need to replace the IP address, which will vary with every 302 from the server. I want to set it statically to an IP address I want.

     

     

    at first I tried to use UDP::payload and replace the hex values using the offset, but the offset varies too... so now I'm trying it this way... let me repost the the irule there are some small details missing...

     

     

    when SIP_RESPONSE {

     

    set contact [ SIP::header Contact ]

     

    set telephone 0

     

    set bind 0

     

    regexp {[0-9]{13}} $contact telephone

     

    regexp {[0-9]{8}} $contact bind

     

    SIP::header remove Contact

     

    SIP::header insert [format \"$bind\"

     

    }

     

  • symtex_22198's avatar
    symtex_22198
    Icon for Nimbostratus rankNimbostratus
    Jul 23, 2009
    oops, reposted the irule incorrectly again

     

     

    when SIP_RESPONSE {

     

    set contact [ SIP::header Contact ]

     

    set telephone 0

     

    set bind 0

     

    regexp {[0-9]{13}} $contact telephone

     

    regexp {[0-9]{8}} $contact bind

     

    SIP::header remove Contact

     

    SIP::header insert [format \"$bind\"

     

    }

     

  • symtex_22198's avatar
    symtex_22198
    Icon for Nimbostratus rankNimbostratus
    Jul 23, 2009
    BTW I want to add this is my first irule and I'm fairly excited. I worked with other ADCs and was always curious about F5 and iRules. I could see myself really getting into this, iRules rule!!
  • symtex_22198's avatar
    symtex_22198
    Icon for Nimbostratus rankNimbostratus
    Jul 23, 2009
    i was looking into getfield but I was unsure if it would copy everything before the "@" character. I used a regexp to just concentrate on the lengh of the number from the field. I think it would work if I could somehow get regexp to get the regexp result and put it into a variable that I can later outupt in SIP::header
  • symtex_22198's avatar
    symtex_22198
    Icon for Nimbostratus rankNimbostratus
    Jul 23, 2009
    the amount of traffic is minimal and it doesn't seem like a very resource intensive regexp operation. is regexp known to be very resource intensive on TMOS?
  • hooleylist's avatar
    hooleylist
    Icon for Cirrostratus rankCirrostratus
    Jul 23, 2009
    Here is what I was thinking might work. I tested the scan command, but not the iRule.

     

     

     
 when SIP_RESPONSE { 
  
     Check for 302 responses 
    if {[SIP::response code] == 302}{ 
  
        Parse the Contact header value "16601003" using scan 
        http://www.tcl.tk/man/tcl8.4/TclCmd/scan.htm 
          start reading everything not a @ into 'a' 
          then read everything not a : into 'b' 
          finally read the rest into 'c' 
        Example using tclsh: 
          % scan {"16601003"} {%[^@]@%[^:]:%s} a b c 
          3 
          % puts "$a $b $c" 
          "16601003" 
       if {[scan [SIP::header value "Contact"] {%[^@]@%[^:]:%s} a b c] == 3}{ 
  
           We parsed three strings into a b c 
          log local0. "Parsed [SIP::header value "Contact"] into $a, $b, $c" 
  
           Remove existing Contact header 
          SIP::header remove "Contact" 
  
           Insert new Contact header with 1.1.1.1 set as a static IP address 
          SIP::header insert "Contact" "${a}@1.1.1.1:${c}" 
  
          log local0. "Inserting new Contact header: ${a}@1.1.1.1:${c}" 
       } 
    } 
 }

     

     

    Aaron
  • symtex_22198's avatar
    symtex_22198
    Icon for Nimbostratus rankNimbostratus
    Jul 23, 2009
    that worked!!!! except there is a problem, the telephony people told me this is what they needed. now they're telling me it's ok but erase the first part of the field so

     

     

    modify

     

    Contact: "16601003"

     

    to

     

    Contact:

     

     

    how can I modify the scan command to do this?
  • symtex_22198's avatar
    symtex_22198
    Icon for Nimbostratus rankNimbostratus
    Jul 23, 2009
    NEVERMIND I GOT IT I GOT IT!!!! i got the scan command

     

    just modified

     

    scan {"16601003"} {%[^<]%[^@]@%[^:]:%s} a b c d

     

     

    I was a perl/sh programmer, this tcl stuff is awesome

     

    AWESOME