Forum Discussion
Greg_91698
Nimbostratus
NimbostratusiRule only runs once
I have a BigIP 3400 running BIG-IP 9.4.8 Build 355.0 Final. I am trying to do some payload replacement. I contacted tech support and they told me to ask here. I would have thought they would know the answer. I first tried using a Stream Profile to do a simple replace of www.xyz.com with www3.xyz.com. The home page would load, but any links off the home page would only load a finite amount of data. Very frustrating. So, I decided to write an iRule. After some research I came up with the following:
when HTTP_REQUEST {
Don't allow data to be chunked
if { [HTTP::version] eq "1.1" } {
if { [HTTP::header is_keepalive] } {
HTTP::header replace "Connection" "Keep-Alive"
}
HTTP::version "1.0"
}
}
when HTTP_RESPONSE {
First, check to see if there's a Content-Length header
if {[info exists [HTTP::header Content-Length]] } {
If there is, we'll collect that much data
set clen [HTTP::header "Content-Length"]
} else {
Otherwise we collect the max
set clen 4294967295
}
if { $clen > 0 } {
HTTP::collect $clen
}
}
when HTTP_RESPONSE_DATA {
set find "www.xyz.com"
set replace "www3.xyz.com"
set payload [HTTP::payload]
log local0. "Test"
if {[regsub -all $find $payload $replace new_response] > 0} {
log local0. "Replacing www with www3."
HTTP::payload replace 0 [HTTP::payload length] $new_response
}
HTTP::release
}
This rule ONLY fires 1 time. Any subsequent refreshes or links I follow result in the rule not matching again. When I say the rule only fires 1 time the log entry of "Test" only shows up 1 time. I have to uninstall the iRule and then put it back to get it to work again. Like I said, I've asked Tech Support, but they were no help at all. Could someone please point me in the right direction? Thank you.
clazbaHi,
You should be able to achieve this relatively easily using the STREAM::replace command. Have a look at the example below.when HTTP_REQUEST { Collects the entire payload as per content lenght HTTP::collect [HTTP::header Content-Length] } when HTTP_REQUEST_DATA Sets var to string set string_to_find [findstr [HTTP::payload] TAG 4 <] log local0. "String $string_to_find identified in Request payload" Release payload HTTP::release } when HTTP_RESPONSE { Disable the stream filter by default STREAM::disable You can use strings or Regexs to match string (this one matches email addresses) STREAM::expression {@[a-z0-9._%+-]+\@[a-z0-9.-]+\.[a-z]{2,6}@@} Reenables the stream filter STREAM::enable } when STREAM_MATCHED { Sets data to replace set data_to_replace "something" Replaces string with var STREAM::replace $data_to_replace }
Cheers,
Claud
hoolioCirrostratus
Hi Greg,
Sorry to hear that you haven't been able to get concrete help with this yet. As Claud said, I would actually suggest you go back to the stream profile option and use a STREAM::expression based iRule to do this replacement in the HTTP response payloads.
http://devcentral.f5.com/wiki/default.aspx/iRules/stream__expression
You don't need to do the HTTP request payload collection in his example. But the response stream profile config should work well:Example which replaces http:// with https:// in response content Prevents server compression in responses when HTTP_REQUEST { Disable the stream filter for all requests STREAM::disable LTM does not uncompress response content, so if the server has compression enabled and it cannot be disabled on the server, we can prevent the server from sending a compressed response by removing the compression offerings from the client HTTP::header remove "Accept-Encoding" } when HTTP_RESPONSE { Check if response type is text if {[HTTP::header value Content-Type] contains "text"}{ Replace www.xyz.com with www3.xyz.com STREAM::expression {@www\.xyz\.com@www3.xyz.com@} Enable the stream filter for this response only STREAM::enable } }
Aaron
Greg_91698Thanks for the help. I'll look into the STREAM::expression function. I was basing my iRule off of some of the examples found here on DevCentral, but they all used HTTP::payload. I'll let you know what I come up with. Thanks again.- Greg_91698Ok, the stream replace irule is doing the exact same thing the Stream Profile did. You can see what I mean by going to www3.msstate.edu and then go to www3.msstate.edu/president/
- hoolioDo you have a custom HTTP profile with response chunking set to rechunk configured on the virtual server?
Aaron - Greg_91698It's inheriting from the default http profile. It's set to "preserve".
- Greg_91698Posted By hoolio on 03/10/2011 02:30 PM
Do you have a custom HTTP profile with response chunking set to rechunk configured on the virtual server?
Aaron
Ok, this made me look at the http profile. I changed the Response Chunking to "selective". That fixed it. I then scrapped the iRule and and just used the Stream Profile. Works like a champ now. Thanks everyone for all of your help. This community rocks! - hoolioI'd still use the iRule as it's more efficient to only apply the stream filter to text responses. When just using a stream profile, the stream filter is applied to all request and response payloads. So you can get errant matches on request payloads and waste resources on non-text replies with just a stream profile.
Aaron