hostname rewrite

There isn't a host header in responses. The app would potentially include absolute references to the hostname in HTTP headers and the payload.

 

 

If the ProxyPass iRule is overkill for your scenario, you might be able to take a stripped down version and adapt it for your requirements. This Codeshare example is for rewriting the URI, but you could adapt it for external/internal hostnames in your scenario.

 

 

http://devcentral.f5.com/wiki/default.aspx/iRules/Uri_Version_Mapping.html

 

 

Here is a version that assumes the application does not include absolute references to the "internal" hostname in response content:

 

 

iRule to change host headers

 

http://devcentral.f5.com/Default.aspx?tabid=53&forumid=5&tpage=1&view=topic&postid=19917

 

 

Aaron

Hi hoolio, thanks for the response. I will take a look at the links you provided.

HI hoolio, I wrote up the iRule I think that should work (I have not tested this yet...I'm hoping to test this early next week).

In a nutshell, on HTTP_REQUEST..I'm going to rewrite the HTTP host header from aaa.company.com to bbb.company.com and on the HTTP_REQUEST, if HTTP header "Location" exists, I'm going to rewrite Location value from bbb.company.com to aaa.company.com (Is that a valid task to rewrite the Location? Do I need to rewrite the hostname anywhere else?). Again, I don't know if this is going to work or not...

 
  when RULE_INIT {        
 set ::external_hostname "aaa.company.com"         
 set ::internal_hostname "bbb.company.net"    
  Enable debug logging to /var/log/ltm.  1 = yes, 0 = no 
 set ::hostname_rewrite_debug 0 
 }    
  
  
 when HTTP_REQUEST {                
 if {$::hostname_rewrite_debug}{log local0. "Original URL: [HTTP::host][HTTP::uri]"} 
  
 HTTP::header replace "Host" $::internal_hostname        
  
 if {$::hostname_rewrite_debug}{log local0. "New URL: [HTTP::host][HTTP::uri]"} 
 }    
  
  
 when HTTP_RESPONSE {         
 if { [HTTP::header value "Location"] starts_with "$::internal_hostname" }{ 
  
 if {$::hostname_rewrite_debug}{log local0. "Inside of HTTP::header location, orig HTTP location equals: [HTTP::header location]"} 
  
 set ::location [HTTP::header location] 
  
 HTTP::header replace location $::external_hostname 
  
 if {$::hostname_rewrite_debug}{log local0. "Inside of HTTP::header location, new HTTP location equals: [HTTP::header location]"} 
 } 
 }   
 

Hi Frisco,

A few notes:

- This line won't log the updated host header value as the HTTP::host value is cached within the same event and event priority. If you want to log the Host header update, you can add a second HTTP_REQUEST event after the first:

 
 when HTTP_REQUEST priority 501 { 
    if {$::hostname_rewrite_debug}{log local0. "New URL: [HTTP::host][HTTP::uri]"}  
 } 
 

- The Location header value is normally an absolute URL like http://www.example.com/path/to/file.ext. So you would want to check for a Location header value which starts with http://$::internal_hostname or https://$::internal_hostname. Also, when rewriting the Location header value, you would want to do an in place replacement of $::internal_hostname for $::external_hostname--not just replace the Location header value with $::external_hostname. You can do this using:

HTTP::header replace Location [string map -nocase "$::internal_hostname $::external_hostname" [HTTP::header Location]]

The internal hostname might be included in links or other references in the response content. If that's the case, you would want to use a stream profile and STREAM::expression based iRule to rewrite the response payload. The wiki page for STREAM::expression has some examples for this.

Aaron

Interesting use case. Was there ever a solution that you don't mind sharing?

 

Thanks.