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Richard_Marsha1's avatar
Richard_Marsha1
Icon for Nimbostratus rankNimbostratus
Sep 06, 2006

http content rewrite

Hi,

 

 

I'm looking for some help writing my first iRule.

 

 

We are quering a remote domain for an xml feed, but often the returned content begins with garbage - please see example below:

 

 

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

 

bless( do{\(my $o = 136523848)}, 'Cache::FastMmap::CImpl' )

 

5|87238978

 

$HashPage-->18<--

 

$HashSlot-->142389272<--

 

 

..............

 

 

undef

 

$Flags-->0<--

 

$Found-->0<--

 

Cache::FastMmap.pm************************

 

 

etc, etc....

 

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

 

 

what I need to do is remove everything before the xml opening tags and leave the rest as it is. i only want this iRule to apply when we are talking to a particular domain to save on load - we do similar queries against a number of domains, but only one has the issue.

 

 

i have seen the iRule that strips a CC number from the content and understand parts of it, but don't get how I can modify it for my purposes. Can someone point me in the right direction, or offer some suggestions on how i can do this?

 

 

Thanks

 

 

Rich

 

 

application delivery
dev
devops
iRules

6 Replies

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  • bl0ndie_127134's avatar
    bl0ndie_127134
    Historic F5 Account
    Sep 07, 2006
    Wow, I am surprised no one jumped on this one. You should be able to do this using the new stream profile introduced in version 9.2. Check out this post for more details. Good luck!

     

     

    Click here
  • Richard_Marsha1's avatar
    Richard_Marsha1
    Icon for Nimbostratus rankNimbostratus
    Sep 08, 2006
    Hey, thanks for the reply. unfortunatly we're running 9.0 and 9.1 - f5 support hgave advised against running 9.2 yet. Can we still do something in these versions?

     

     

  • Deb_Allen_18's avatar
    Deb_Allen_18
    Historic F5 Account
    Sep 09, 2006
    Maybe something like this:

    Create a class of type string containing the hostnames for which you want the rule to run:

    class BadServers {
  "www.domain1.com"
  "www.domain2.com"
}

    to be used by this iRule:
    rule rewrite_content {
 when HTTP_REQUEST {
  if {[matchclass [HTTP::host] $::BadServers]}{
    set replace 1
 }
 when HTTP_RESPONSE {
  if {$replace}{
    if {[HTTP::header exists Content-Length]}{
      set clen [HTTP::header Content-Length]
    } else {
      set clen 4294967295
    }
    if { $clength > 0 } {
      HTTP::collect $clen
    }
  }
 }
 when HTTP_RESPONSE_DATA {
  if {$replace}{
    find beginning of data to keep
    set xml_start [string first {    if { $xml_start > 0 }{
      set newPayload [string range [HTTP::payload] $xml_start end]
      HTTP::payload replace 0 $clen $newPayload
    }
    HTTP::release
  }
 }
}

    HTH

    /deb

  • Richard_Marsha1's avatar
    Richard_Marsha1
    Icon for Nimbostratus rankNimbostratus
    Sep 11, 2006
    Hey Deb,

     

     

    Thanks for the suggestion - I will take a look at it and see what I can understand (and apply to our problem)

     

     

    Regards

     

     

    Rich
  • Richard_Marsha1's avatar
    Richard_Marsha1
    Icon for Nimbostratus rankNimbostratus
    Sep 19, 2006
    Well,

     

     

     

    I've finally managed to get the thing to compile, but I'm not currently able to test it (because it's production traffic) but i guess it should work.

     

     

    Here's the irule: where BadServers = foo.bar.com

     

     

    when HTTP_REQUEST {

     

    if { [matchclass [HTTP::host] equals $::BadServers] }{

     

    set replace 1

     

    }

     

    }

     

    when HTTP_RESPONSE {

     

    if {$replace > 0}{

     

    if {[HTTP::header exists "Content-Length"]}{

     

    set clen [HTTP::header "Content-Length"]

     

    } else {

     

    set clen 4294967295

     

    }

     

    if { $clen > 0 } {

     

    HTTP::collect $clen

     

    }

     

    }

     

    }

     

    when HTTP_RESPONSE_DATA {

     

    if {$replace}{

     

    find beginning of data to keep

     

    set xml_start [string first { if { $xml_start > 0 }{

     

    set newPayload [string range [HTTP::payload] $xml_start end]

     

    HTTP::payload replace 0 $clen $newPayload

     

    }

     

    HTTP::release

     

    Log Results

     

    log local0. "Found $xml_start replaced with $newPayload"

     

    }

     

    }
  • Joe_Pruitt's avatar
    Joe_Pruitt
    Sep 19, 2006
    I would set replace to 0 as a default in the HTTP_REQUEST event or you will get a undefined variable error when trying to access it in the other events.

    when HTTP_REQUEST {
  set replace 0
  if { [matchclass [HTTP::host] equals $::BadServers] }{
    set replace 1
  }
}

    Otherwise, it looks good to me...

    -Joe