Rewriting RTSP response

I am running 9.2.4 on a 1500 with an EA license. I have an RTSP VIP that is NAT'd to an external IP address. Because RTSP is not NAT-friendly, I am using Darwin Streaming Server's alt_transport_src_ipaddr setting so that the external address of the VIP is embedded in the RTSP packets instead of the internal address of the Darwin servers.

 

 

The problem I am having is that the Big IP replaces the external VIP address in the packets with the internal VIP address, and this behavior doesn't seem to be configurable. I created a stream profile to replace the internal address with the external one but it doesn't affect the RTSP packets for some reason (order of operations?) So I'm trying to accomplish this with an iRule. Here's what I have:

 

 

when RTSP_RESPONSE {

 

regsub -all "1.1.1.1" [RTSP::payload] "2.2.2.2" fixeddata

 

RTSP::payload replace 0 [RTSP::payload length] $fixeddata

 

RTSP::release

 

}

 

 

But this doesn't compile. I get the following:

 

 

011c0003:3: Rule checker ::tclCheck::checkScript did not complete (invalid command name "allow").

 

 

Again, I am running with the EA license so I do have access to the RTSP functionality. Any ideas why my iRule doesn't work or if there is another way to accomplish this?