Help: how to only discard the first packet?

Hi

 

I'm trying to use the dynamic IP to do SNAT.

 

I setup a virtual server as 0.0.0.0:7070 with pool member "sourcetest".

 

 

When the client request, client should first send an IP to BIGIP in the format "IP=x.x.x.x&". If BIGIP captures IP x.x.x.x, it will use this IP to do SNAT. If BIGIP captures only "null", it will use 192.168.0.1 to do SNAT.

 

 

The problem I met is, when I use "discard" to discard the packet contains IP info, it fails. "discard" will not drop the packet but the connection. It causes the client cannot access to the server.

 

 

If I removed "discard" from iRule, BIGIP will also forward the "IP=x.x.x.x&" to the server. This packet is meaningless to server and sometimes will cause the connection dropped.

 

 

 

when CLIENT_ACCEPTED {

 

set source 0

 

log local0. "7070 connected"

 

TCP::collect 19

 

}

 

when CLIENT_DATA {

 

if { $source == 0 } {

 

if { [findstr [TCP::payload] "IP=" 3 "&"] equals "null" } {

 

set source 1

 

log local0. "No client ip found."

 

} else {

 

set source [findstr [TCP::payload] "IP=" 3 "&"]

 

log local0. "Found client ip=$source"

 

}

 

discard

 

}

 

if { $source == 1 } {

 

snat 192.168.0.1

 

log local0. "snat 192"

 

} else {

 

snat $source

 

log local0. "snat with source"

 

}

 

pool sourcetest

 

TCP::release

 

}

 

 

 

In DevCentral, I found the description of "discard":

 

Causes the current packet or connection (depending on the context of the event) to be discarded.

 

 

My question is, how can I let "discard" only discard the first packet?