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bc1's avatar
bc1
Icon for Nimbostratus rankNimbostratus
Mar 31, 2017

Using variables to create HTTP::respond string?

Hi there,

I've been working with f5 for only a short while and have run into an issue which I hope someone might be able to shed some light on ..

I'm trying to write a procedure which builds an HTTP response string and then uses HTTP::repond to deliver it but unless I write

Essentially I want to build a header string based on logic in the iRule something like:

 

set myStatusCode 405
set myContent "Only POSTs allowed here .."
set myHeader "time \"[clock seconds]\"
httpString = "$myStatusCode content $myContent $myHeader"

HTTP::respond $httpString

 

This isn't working in the slightest 🙂 - "expected integer but got "405 content "Only POSTs allowed here .."

Is there a way to do this or am I trying to use HTTP::respond for something it wasn't designed to do? If I write the command in with no variables as below it works fine..

 

HTTP::respond 405 "Only POSTs allowed here .." time 033576859

 

 

Many thanks!

 

bc

 

application delivery
BIG-IP
iRules
  • Vijay_E's avatar
    Vijay_E
    Icon for Cirrus rankCirrus
    Mar 31, 2017

    Try:

    HTTP::respond $myStatusCode $myContent $myHeader

    If the above works, try dropping the "content" from this variable:

    httpString = "$myStatusCode content $myContent $myHeader"

  • Kai_Wilke's avatar
    Kai_Wilke
    Icon for MVP rankMVP
    Apr 04, 2017

    Hi bc,

    the [HTTP::respond] command requires you to pass each additional header as two parameters. So you may either pass your additional headers as two variables...

     

    set statusCode 405  
set httpcontent  "Only POSTs allowed"
set extraheader_name "Connection" 
set extraheader_value "Close"

HTTP::respond $statusCode content $httpContent $extraheader_name $extraheader_value

     

    ... or you could utilize TCLs [eval] command to create and finally execute a custom TCL script during runtime.

     

    set http_respond_param "405 content \"Only POSTs allowed\" Connection Close"
eval "HTTP::respond $http_respond_param"

     

    Note: The use of [eval] to create a (non-global) TCL script should be strongly avoided. The reason is, that [eval] needs to parse and byte-code compile the provided script. This will add additional overhead to the system. In addition you have to make sure that the usage of [eval] does not introduce TCL Code-Injection attack vectors, by wrapping every user provided infomation into curly {} braces so that those information are getting hidden either from the first or second command substitution. For further information read those wiki pages.

    Information on [eval]

    http://wiki.tcl.tk/1017

    Information on TCL Code Injection Attacks

    http://wiki.tcl.tk/26499

    Cheers, Kai