Forum Discussion

Nimbostratus

May 28, 2016

Solved

HTTP Rewrite header + pool based on URI

Hi,

I need to forward traffic from external URL to one of our internal servers based on URI. That has to be transparent for the browser with no redirect messages 3xx.

Searching in the forum and using codes from other members I constructed the following iRule though based on by debug it looks like I'm getting in problems with the HTTP response header.

I'm trying to modify the header for requests coming to externalsite.com/foobar --> internalsite.com/foobar and direct these requests to specific pool named "internal_pool" The reply back should contain the original header and all that has to be done transparent to the browser.

I would very much appreciate if any one can share an idea where I'm going wrong:

Here is my iRule:

==========================

when RULE_INIT {

 Set the hostname that the client makes request to (do not include protocol)  
set external_hostname "externalsite.com"  

 Set the hostname that the BIG-IP will rewrite requests to  
set internal_hostname "internalsite.com"

when CLIENT_ACCEPTED { assign default pool to variable once 3WHS is complete. set default_pool [LB::server pool] }

when HTTP_REQUEST {

log local6.notice "External request from [IP::client_addr] -> [HTTP::host][HTTP::uri]"  
if { ([string tolower [HTTP::uri]] eq "/foobar") } {
    HTTP::header replace Host "$internal_hostname"
pool internal_pool
log local6.notice "External request header rewrite [IP::client_addr] -> [HTTP::host][HTTP::uri]"
} else { 
    pool $default_pool
}

} when HTTP_RESPONSE { if { [HTTP::status] == 302 } { switch [string tolower [HTTP::header Location]] { "$&internal_hostname" { HTTP::header replace Location "&external_hostname" } }

} }

Thank You.

Hi,

here an rule example :

when RULE_INIT {
    set external_hostname "externalsite.com"  
    set internal_hostname "internalsite.com"  
}
when CLIENT_ACCEPTED { 
    set default_pool [LB::server pool] 
} 
when HTTP_REQUEST {
     Disable the stream filter for requests
    STREAM::disable

     Remove this header to prevent server from compression response
    HTTP::header remove Accept-Encoding

    if { ([string tolower [HTTP::path]] eq "/foobar") } {
        HTTP::host [string map {$external_hostname $internal_hostname} [HTTP::host]] 
        pool internal_pool
    } else { 
        pool $default_pool
    }
}
when HTTP_RESPONSE {
     Rewrite the Location header for redirects 
    if { [HTTP::header exists Location] }{ 
        HTTP::header replace Location [string map {$external_hostname $internal_hostname} [HTTP::header Location]] 
    } 

     Rewrite the response content using a stream profile if it is text 
    if { [HTTP::header Content-Type] contains "text" } { 

         Set the stream expression with the find/replace strings 
        STREAM::expression "@xyz.company.com@abc.company.com@" 

         Enable the stream filter 
        STREAM::enable 
    } 
}

23 Replies

Vijay_E

Cirrus

May 28, 2016

Try this (untested):

when RULE_INIT {
set external_hostname "externalsite.com"  
set internal_hostname "internalsite.com"  

when CLIENT_ACCEPTED { 
set default_pool [LB::server pool] 
}

when HTTP_REQUEST {
if { ([string tolower [HTTP::uri]] eq "/foobar") } {
    HTTP::host [string map {$external_hostname $internal_hostname} [HTTP::host]] pool internal_pool
} else { 
    pool $default_pool
}

when HTTP_RESPONSE {
if { [HTTP::header values Location] contains "$internal_hostname" } {
HTTP::header replace Location [string map {$internal_hostname $external_hostname} [HTTP::header value Location]]
}
}

Yann_Desmarest_

Nacreous

May 28, 2016

Hi,

here an rule example :

when RULE_INIT {
    set external_hostname "externalsite.com"  
    set internal_hostname "internalsite.com"  
}
when CLIENT_ACCEPTED { 
    set default_pool [LB::server pool] 
} 
when HTTP_REQUEST {
     Disable the stream filter for requests
    STREAM::disable

     Remove this header to prevent server from compression response
    HTTP::header remove Accept-Encoding

    if { ([string tolower [HTTP::path]] eq "/foobar") } {
        HTTP::host [string map {$external_hostname $internal_hostname} [HTTP::host]] 
        pool internal_pool
    } else { 
        pool $default_pool
    }
}
when HTTP_RESPONSE {
     Rewrite the Location header for redirects 
    if { [HTTP::header exists Location] }{ 
        HTTP::header replace Location [string map {$external_hostname $internal_hostname} [HTTP::header Location]] 
    } 

     Rewrite the response content using a stream profile if it is text 
    if { [HTTP::header Content-Type] contains "text" } { 

         Set the stream expression with the find/replace strings 
        STREAM::expression "@xyz.company.com@abc.company.com@" 

         Enable the stream filter 
        STREAM::enable 
    } 
}

dihris_116090
Nimbostratus
May 28, 2016
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Hi Yann, thank you for your response. I've created stream profile and added to the VS. Installed the iRule though it does not seem to be working. As with the iRule from Odaah I do not see the header getting changed. I take it under STREAM::expression I neeed to change the find/replace string to @$internalsite.com@$externalsite.com@ ? What logging should I put to see exactly where the iRule brakes?
Yann_Desmarest_
Nacreous
May 28, 2016
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Report
Hi, you can check in the ltm log if there is some tcl errors from this irule.

Yann_Desmarest

Cirrus

May 28, 2016

Hi,

here an rule example :

when RULE_INIT {
    set external_hostname "externalsite.com"  
    set internal_hostname "internalsite.com"  
}
when CLIENT_ACCEPTED { 
    set default_pool [LB::server pool] 
} 
when HTTP_REQUEST {
     Disable the stream filter for requests
    STREAM::disable

     Remove this header to prevent server from compression response
    HTTP::header remove Accept-Encoding

    if { ([string tolower [HTTP::path]] eq "/foobar") } {
        HTTP::host [string map {$external_hostname $internal_hostname} [HTTP::host]] 
        pool internal_pool
    } else { 
        pool $default_pool
    }
}
when HTTP_RESPONSE {
     Rewrite the Location header for redirects 
    if { [HTTP::header exists Location] }{ 
        HTTP::header replace Location [string map {$external_hostname $internal_hostname} [HTTP::header Location]] 
    } 

     Rewrite the response content using a stream profile if it is text 
    if { [HTTP::header Content-Type] contains "text" } { 

         Set the stream expression with the find/replace strings 
        STREAM::expression "@xyz.company.com@abc.company.com@" 

         Enable the stream filter 
        STREAM::enable 
    } 
}

dihris_116090
Nimbostratus
May 28, 2016
Copy Link
Report
Hi Yann, thank you for your response. I've created stream profile and added to the VS. Installed the iRule though it does not seem to be working. As with the iRule from Odaah I do not see the header getting changed. I take it under STREAM::expression I neeed to change the find/replace string to @$internalsite.com@$externalsite.com@ ? What logging should I put to see exactly where the iRule brakes?
Yann_Desmarest
Cirrus
May 28, 2016
Copy Link
Report
Hi, you can check in the ltm log if there is some tcl errors from this irule.

Yann_Desmarest
Cirrus
May 28, 2016
Copy Link
Report
Hi,

In the HTTP_REQUEST event, try to replace this :

HTTP::host [string map {$external_hostname $internal_hostname} [HTTP::host]]

by

HTTP::header replace "Host" [string map "$external_hostname $internal_hostname" [HTTP::host]]
- Yann_Desmarest
  Cirrus
  May 28, 2016
  Copy Link
  Report
  or use : HTTP::header replace "Host" [string map -nocase [list $external_hostname $internal_hostname] [HTTP::host]]
- Yann_Desmarest
  Cirrus
  May 28, 2016
  Copy Link
  Report
  The issue is the support for variables in the string map
- dihris_116090
  Nimbostratus
  May 30, 2016
  Copy Link
  Report
  In both cases I'm getting TCL error: err tmm1[32619]: 01220001:3: TCL error: /Common/test_3 - can't read "external_hostname": no such variable while executing "string map "$external_hostname $internal_hostname" [HTTP::host]" ==================== err tmm1[32619]: 01220001:3: TCL error: /Common/test_3 - can't read "external_hostname": no such variable while executing "list $external_hostname $internal_hostname" I did verify that the variables I set when initiating the iRule do match. My internal host does have a bit non standard name: foo-bar-baz.qux.mycompany.io can that be creating an issue?
Yann_Desmarest_
Nacreous
May 28, 2016
Copy Link
Report
Hi,

In the HTTP_REQUEST event, try to replace this :

HTTP::host [string map {$external_hostname $internal_hostname} [HTTP::host]]

by

HTTP::header replace "Host" [string map "$external_hostname $internal_hostname" [HTTP::host]]
- Yann_Desmarest_
  Nacreous
  May 28, 2016
  Copy Link
  Report
  or use : HTTP::header replace "Host" [string map -nocase [list $external_hostname $internal_hostname] [HTTP::host]]
- Yann_Desmarest_
  Nacreous
  May 28, 2016
  Copy Link
  Report
  The issue is the support for variables in the string map
- dihris_116090
  Nimbostratus
  May 30, 2016
  Copy Link
  Report
  In both cases I'm getting TCL error: err tmm1[32619]: 01220001:3: TCL error: /Common/test_3 - can't read "external_hostname": no such variable while executing "string map "$external_hostname $internal_hostname" [HTTP::host]" ==================== err tmm1[32619]: 01220001:3: TCL error: /Common/test_3 - can't read "external_hostname": no such variable while executing "list $external_hostname $internal_hostname" I did verify that the variables I set when initiating the iRule do match. My internal host does have a bit non standard name: foo-bar-baz.qux.mycompany.io can that be creating an issue?

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Set the hostname that the client makes request to (do not include protocol) \nset external_hostname \"externalsite.com\" \n\n Set the hostname that the BIG-IP will rewrite requests to \nset internal_hostname \"internalsite.com\" \n

log local6.notice \"External request from [IP::client_addr] -> [HTTP::host][HTTP::uri]\" \nif { ([string tolower [HTTP::uri]] eq \"/foobar\") } {\n HTTP::header replace Host \"$internal_hostname\"\npool internal_pool\nlog local6.notice \"External request header rewrite [IP::client_addr] -> [HTTP::host][HTTP::uri]\"\n} else { \n pool $default_pool\n}\n

when RULE_INIT {\nset external_hostname \"externalsite.com\" \nset internal_hostname \"internalsite.com\" \n\nwhen CLIENT_ACCEPTED { \nset default_pool [LB::server pool] \n}\n\nwhen HTTP_REQUEST {\nif { ([string tolower [HTTP::uri]] eq \"/foobar\") } {\n HTTP::host [string map {$external_hostname $internal_hostname} [HTTP::host]] pool internal_pool\n} else { \n pool $default_pool\n}\n\nwhen HTTP_RESPONSE {\nif { [HTTP::header values Location] contains \"$internal_hostname\" } {\nHTTP::header replace Location [string map {$internal_hostname $external_hostname} [HTTP::header value Location]]\n}\n}\n

when RULE_INIT {\n set external_hostname \"externalsite.com\" \n set internal_hostname \"internalsite.com\" \n}\nwhen CLIENT_ACCEPTED { \n set default_pool [LB::server pool] \n} \nwhen HTTP_REQUEST {\n Disable the stream filter for requests\n STREAM::disable\n\n Remove this header to prevent server from compression response\n HTTP::header remove Accept-Encoding\n\n if { ([string tolower [HTTP::path]] eq \"/foobar\") } {\n HTTP::host [string map {$external_hostname $internal_hostname} [HTTP::host]] \n pool internal_pool\n } else { \n pool $default_pool\n }\n}\nwhen HTTP_RESPONSE {\n Rewrite the Location header for redirects \n if { [HTTP::header exists Location] }{ \n HTTP::header replace Location [string map {$external_hostname $internal_hostname} [HTTP::header Location]] \n } \n\n Rewrite the response content using a stream profile if it is text \n if { [HTTP::header Content-Type] contains \"text\" } { \n\n Set the stream expression with the find/replace strings \n STREAM::expression \"@xyz.company.com@abc.company.com@\" \n\n Enable the stream filter \n STREAM::enable \n } \n}\n

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HTTP Rewrite header + pool based on URI

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