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gost2307_337235's avatar
gost2307_337235
Icon for Nimbostratus rankNimbostratus
Oct 24, 2017

Replace string using stream profile from backend server to client

We have the problem to rewrite string in Stream Profile (iRule). The client is requesting the URL: "https://abc.com"; and the backend server responded with absolute URL Hostname "def.com". Because of this response we are getting failure message, so we want F5 to replace this string from "abc.com" to "def.com". We tried some different iRules but we couldn't achieve it. Please help us to find the solution. The following iRule we are using right now. 

'' when HTTP_REQUEST {
 Disable STREAM processing for request (ingress) traffic
STREAM::disable    

 Remove the Accept-Encoding header to disable server side compression
HTTP::header remove Accept-Encoding

 Replace the incoming Host header to match what the server expects
HTTP::header replace Host "defp.com"

}

when HTTP_RESPONSE {
if { [HTTP::header exists Location] } {
     If this is a redirect response, replace http://def.com with https://abc.com

    HTTP::header replace Location [string map {"http://def.com" "https://abc.com"} [HTTP::header Location]            
}

 Use a STREAM expression to remap all object references in the payload (HTML body) with the external host name
STREAM::expression {@http://def.com@https://abc.com@ }
STREAM::enable



}
application delivery
devops
iRules
LTM

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  • Stanislas_Piro2's avatar
    Stanislas_Piro2
    Icon for Cumulonimbus rankCumulonimbus
    Oct 24, 2017

    Hi,

    you can try this irule. the stream commands are in variable to support disabling stream profile and manage only 30X redirects.

    rewriting try to convert absolute URL to relative URLs if the public URL is based on the service requested. 

    when RULE_INIT {
    unset static::rewrite_table
    array set static::rewrite_table {
        "https://www.company.com"   "http://srv-internal.company.local"
        "https://www2.company.com"   "http://srv-internal2.company.local"
    }
    set static::rewrite_table_map [list]
    set static::rewrite_table_stream [list]
    foreach item [array names static::rewrite_table] {
        lappend static::rewrite_table_map $static::rewrite_table($item)/ $item/ $static::rewrite_table($item) $item/
        lappend static::rewrite_table_stream "@$static::rewrite_table($item)/@$item/@"
    }
    log local0. $static::rewrite_table_map
    log local0. $static::rewrite_table_stream
     create stream commands in variables to run them only id stream profile is enabled
    set static::stream_disable "STREAM::disable"
    set static::stream_enable "STREAM::enable"
     change stream expression to convert current site response to relative URI.
    set static::stream_expression "STREAM::expression \[string map \"\$req_proto://\$req_host/ /\" \$static::rewrite_table_stream\]"
}

when CLIENT_ACCEPTED {
     set default protocol to http. change it to https if clientssl profile is assigned to the VS.
    if { [PROFILE::exists clientssl] == 1} {
        set req_proto "https"
    } else {
        set req_proto "http"
    }
    set stream_profile_enabled [PROFILE::exists stream]
}

when HTTP_REQUEST {
     Capture request hostname
    set req_host [HTTP::host]
    if {$stream_profile_enabled} {
         Disable the stream filter for all requests
        eval $static::stream_disable

         LTM does not uncompress response content, so if the webserver has compression enabled
         we must prevent the server from send us a compressed response by changing the request
         header that indicates client support for compression (on our LTM client-side we can re-
         apply compression before the response goes across the Internet)
        HTTP::header remove "Accept-Encoding"
    }
}

when HTTP_RESPONSE {
    if { [HTTP::status]  matches "30?"} {
         This is a 302 redirect with a absolute Location URI
        HTTP::header replace Location [string map [string map "$req_proto://$req_host/ /" $static::rewrite_table_map] [HTTP::header Location]]
    } elseif {[HTTP::header value Content-Type] starts_with "text"} {
         Apply stream expression stored in RULE_INIT event
        if {$stream_profile_enabled} {
            eval $static::stream_expression

             Enable the stream filter for this response only
            eval $static::stream_enable
        }
    }
}
  • jmusci_327228's avatar
    jmusci_327228
    Icon for Nimbostratus rankNimbostratus
    Oct 24, 2017

    Did you try using an HTTP policy ? After you created you can create a RULE (not I-rule) where you rewrite URL. I tried it and i find it easier than i-rule development