set

This keyword sets bits to group for a particular flow. When no group specified, set the default group. This keyword always returns true.

Syntax:
    flowbits:set,bats[,group]
Usage:  
    flowbits:set,bit1,doc;
    flowbits:set,bit2&bit3,doc;
    First rule sets bit1 in doc group, second rule sets bit2 and bit3 in doc group. 
    So doc group has bit 1, bit2 and bit3 set