How to add missing Content-Length header to an HTTP POST request?

Thanks Jason

I did not spend much time on this on the layered VS, tested a bit, until gave up, so, unfortunately I did not document the testing much, but I try to recall what I found:

• The APM HTTP Auth object did not put any content length header into the custom POST request to the layered VS, unless it was not specifically added via the GUI
• with an iRule at the layered VS, I tried HTTP::collect in the when HTTP_REQUEST event with no or different content length parameter values (longer, smaller, actual), also tried adding HTTP::release..
• The when HTTP_REQUEST_DATA did not fire at all

So, for me, there was no option to read HTTP::payload and calculate the actual length with for example [string length HTTP::payload] command within the when HTTP_REQUEST_DATA event.. Setting of Content-Length header in that event did not succeed, either. Actually the connection hanged in most configs.. Tried the same in when HTTP_REQUEST event, calculate the length and set the header, similar results or even tcl scope problems..

After a few of hours of trying, I gave up and proceeded with my alternative option and succeeded.

The only way I got the Content-Length header set up and my target auth application accepting it, was explicitly adding the header in the HTTP Auth custom POST configuration page:

Two alternatives: either putting the explicit actual value there or using a session variable

So I ended up with an additional iRule event prior the HTTP Auth in the VPE flow:

• preparing and putting the payload into an APM session variable (with other session variables inside the payload) and
• calculating the length with [string length..] and putting that into another session variable
• then calling those variables in the HTTP Auth custom POST configuration page: payload in the custom body and length with add header Content-Length

The content length actually needed to be 4 bytes longer than the previously calculated value (the HTTP Auth custom POST config seems to add something to the body (perhaps 2xCRLF in the end?). There is a problem of debugging this, as I could not find a way to tcpdump traffic between the HTTP Auth and the layered VS (have raised a support case on this, but haven't got any answer...).

So my problem is sorted out but not the way I wanted it originally..