TCP iRule to find HTTP headers

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1

I have a situation where I have an iRule that works once the user is using the HTTP protocol. Unfortunately, the same VIP handles a proprietary protocol from Oracle called T3. To use the iRule I need an HTTP profile but that will break the T3 users.

  • My idea is the parse the TCP and determine if the request is HTTP
  • If it is HTTP, add an HTTP profile and my iRule to the VIP dynamically

I would like some help. I know the a TCP header is 20 bytes and HTTP starts with the method GET or POST. So I am guessing that I have to ‘scan’ the tcp payload for a GET (for example) and if it starts with that, apply the http profile and then the iRule.

Thanks for your help and/or guidance in advance!

2

My first thoughts are something like this: (the HTTP profile will be configured on the VIP)

` when CLIENT_ACCEPTED { TCP::collect 4 } `

` when CLIENT_DATA { if { ([TCP::payload 4] contains “GET”) || ([TCP::payload 4] contains “POST”) } { HTTP::enable How to add the iRule??? } else { HTTP::disable How to remove the iRule??? } TCP::release } `

3

Another thought I had was disabling and enabling events so I can have 1 iRule: (I haven’t tested it in production yet but my preliminary test suggest that it should work)

when CLIENT_ACCEPTED {
  TCP::collect 4
}
when CLIENT_DATA {

log local0. "Before GET"

  if { [TCP::payload 4] contains "GET" } {
     HTTP::enable
     event HTTP_REQUEST enable
     event HTTP_RESPONSE enable
     rule Levi-Test

log local0. "After GET"  
     if { [PROFILE::exists http] == 1 }{
     log local0. "HTTP profile was added"
     }
    } else {
    HTTP::disable
    event HTTP_REQUEST disable
    event HTTP_RESPONSE disable
    rule none
    log local0. "HTTP profile was removed..."
}
 TCP::release
}
when HTTP_REQUEST {
my irule
}
when HTTP_RESPONSE {
my irule
}
4

I think you could limit the iRule to this:

when CLIENT_ACCEPTED {
    HTTP::disable
    TCP::collect 4
}

when CLIENT_DATA {
    if { [TCP::payload 4] contains "GET" } {
        HTTP::enable
    }
    TCP::release
}

when HTTP_REQUEST {
    my irule
}

when HTTP_RESPONSE {
    my irule
}

I’ll expect the HTTP_REQUEST and HTTP_RESPONSE events will not be triggered when the HTTP profile is disabled.

5

lgtm, only change I’d make is to assure all the request methods supported by your http app are accounted for in your conditional.

6

Thanks,

My iRule has both GET and POST.

if { ([TCP::payload 4] contains “GET”) || ([TCP::payload 4] contains “POST”) } {

Thanks guys for all your great help (Niels van Sluis & Jason Rahm). I’m very positive that this will work once I get to implement it.