Forum Discussion

Magnum_IP's avatar
Magnum_IP
Icon for Nimbostratus rankNimbostratus
Sep 29, 2011

HTTP::uri returns full URL

I have had reason to log HTTP::uri while troubleshooting an error on a new Virtual Server. When I log HTTP::uri I see the full URL including protocol, for example,

 

 

http://www.domain.com/dir/file.htm

 

 

I was anticipating only seeing

 

 

/dir/file.htm

 

 

Can anybody explain what is happening here? This goes against everything I thought I understood about HTTP::uri.

 

 

Thanks

 

 

fergu5

4 Replies

  • Hi Fergu,

     

     

    An HTTP request can contain an absolute URI per RFC2616:

     

     

     

    http://tools.ietf.org/html/rfc2616section-5.1.2

     

     

    5.1.2 Request-URI

     

     

     

    The Request-URI is a Uniform Resource Identifier (section 3.2) and

     

    identifies the resource upon which to apply the request.

     

     

    Request-URI = "*" | absoluteURI | abs_path | authority

     

     

    The four options for Request-URI are dependent on the nature of the

     

    request. The asterisk "*" means that the request does not apply to a

     

    particular resource, but to the server itself, and is only allowed

     

    when the method used does not necessarily apply to a resource. One

     

    example would be

     

     

    OPTIONS * HTTP/1.1

     

     

    The absoluteURI form is REQUIRED when the request is being made to a

     

    proxy. The proxy is requested to forward the request or service it

     

    from a valid cache, and return the response. Note that the proxy MAY

     

    forward the request on to another proxy or directly to the server

     

    specified by the absoluteURI. In order to avoid request loops, a

     

    proxy MUST be able to recognize all of its server names, including

     

    any aliases, local variations, and the numeric IP address. An example

     

    Request-Line would be:

     

     

    GET http://www.w3.org/pub/WWW/TheProject.html HTTP/1.1

     

     

    To allow for transition to absoluteURIs in all requests in future

     

    versions of HTTP, all HTTP/1.1 servers MUST accept the absoluteURI

     

    form in requests, even though HTTP/1.1 clients will only generate

     

    them in requests to proxies.

     

     

     

    You can detect a relative URI by checking if HTTP::uri or HTTP::path start with "/". If not, it should be an absolute URI. You can use the URI:: commands to parse an absolute URI into the protocol, host and relative URI/path:

     

     

    http://devcentral.f5.com/wiki/iRules.URI.ashx

     

    http://devcentral.f5.com/wiki/iRules.URI__path.ashx

     

    http://devcentral.f5.com/wiki/iRules.URI__host.ashx

     

     

    Aaron
  • Hey Hoolio,

     

    Firstly, can I just say that my friend LyonsG and I are continually impresses by your seemingly endless knowledge and your everpresence on DevCentral - do you ever sleep?;-P Thanks for taking the time to help ;-)

     

     

    Secondly your excerpt from the RFC answers my question. This latest project I'm working on is to load balance some proxy servers! So the quote...

     

     

     

    The absoluteURI form is REQUIRED when the request is being made to a proxy.

    nails it;-D

     

     

    I have been writing iRules for a fair while (admittedly never in relation to proxy servers) but I have not come across this absoloute format when using HTTP::uri.

     

     

    I think the Wiki page for HTTP::uri could really do with being updated to include a reference to the quote from your previous reply or the full RFC.

     

     

    At the moment the Wiki page suggests the HTTP::uri will return something beginning with / i.e. something relative. If you read closely the Wiki page does says 'typically' but I only spotted this in hindsight and I imagine others have missed it too.

     

     

    What do you think?

     

     

    fergu5

     

  • There's an RFE for this, BZ222409. You could open a case with F5 Support and ask them to attach it to the RFE.

    For now, you can add logic to your iRule to handle relative and absolute URIs:

    http://devcentral.f5.com/Community/GroupDetails/tabid/1082223/asg/50/aft/1178966/showtab/groupforums/Default.aspx1249734

    
    when HTTP_REQUEST {
    
     Check for an absolute URI
    if {not ([HTTP::uri] starts_with "/")}{
    
    if {[scan $abs_uri {%[^/]//%[^/]%s} proto host uri] == 3}{
    
     Log the URI to a local URI
    log local0. "\$proto: $proto, \$host: $host, \$uri: $uri"
    }
    }
    }
    

    Aaron
  • spark_86682's avatar
    spark_86682
    Historic F5 Account
    That RFE is for changing HTTP::path, not HTTP::uri. You could open up a new RFE for adding a new command to get only the relative part of the URI, and I would encourage you to do so.