A-12 APPENDIX A: PACKET FILTER OPCODES, EXAMPLES, AND SYNTAX ERRORS
Address GroupFilter This filter accepts only frames whose source and destination address are in the same group.name “Forward Same Source and Destination”
pushSAGM # Get source address group mask
pushDAGM # Get destination address group
# mask
and # Compare if source and
destination # groups are common members of
# an address group (result is
# either zero or non-zero)
# address group masks
pushLiteral.l 0 # Put a zero on the stack
ne # If not equal, returns a “one”
# to stack, resulting in packet
# forwarded
Port Group Filter This filter discards all frames sourced from a port in either group three or eight.name “Discard Port Groups 3 and 8”
pushSPGM # Get source port group mask
pushLiteral.l 0x0084 # Select bits 3 and 8
and # If port group bits 3 & 8 are
# common with SPGM, then
# non-zero value is
# pushed onto stack
pushLiteral.l 0 # Push zero
eq # Only if SPGM is not in port
# groups corresponding to bits
# 3 & 8, then packet is
# forwarded