Filter determines whether a packet satisfies
      specified condition.  Actually Filter is
      wrapper for bpf_program.  For details of filter
      expression, see tcpdump(1).
    Objectcompile(expr, capture[, optimize[, netmask]])
new(expr, capture[, optimize[, netmask]])
            Create a new Filter object.
            expr is a filter string.  capture
            is a Capture object.  optimize
            controls optimization of resulting code.
            netmask specifies the netmask of the local net.
          
            Created Filter can be applied to packets
            captured via capture.
          
            If libpcap-0.5 or later
            used, one of following values can be specified
            instead of capture:
            
[snaplen, datalink]- an array containing required parameters
- omitted (or
nil)- Ethernet default (
[68,)DLT_EN10MB]
self === packet
self =~ packet
Return true if packet matches this filter.
~ self
          Return a Filter which represents
          "not self".
        
self | other
          Return a Filter which represents
          "self or other".
        
self & other
          Return a Filter which represents
          "self and other".
        
source
Returns the orginal string from which the filter is constructed.