I developed a program to capture live probe-request packets over the network using libpcap library.
I also used a filter "type mgt subtype probe-req" which worked fine.

Now on my laptop the packets were encapsulated under RADIOTAP HEADER.
but on a router(ie Linksys WRT54g running White Russian, working on monitor mode providing me a prism0 interface) the encapsulation i get is PRISM HEADER.

when I run my program on router it gives me error "Error Compiling filter"

so what filter string should i use so that i scan only the probe request packets over the network.
also can anybody tell me the prism header structure if any so that i can use it in  my program.