Rule syntax

A filter rule definition takes the following syntax:

action───srcip───srcmask───destip───destmask───protocol───

──srcopcode───srcport───destopcode───destport───interface───

──routing───direction────┬─────┬──┬──────────┬──┬────────┬─────┤
                          └─log─┘  └─fragment─┘  └─tunnel─┘