BNF.ipnat revision 302408 
1ipmap :: = mapblock | redir | map .
2
3map ::= mapit ifname ipmask "->" ipmask [ mapport | mapicmpid ] .
4map ::= mapit ifname fromto "->" ipmask [ mapport | mapicmpid ] .
5mapblock ::= "map-block" ifname ipmask "->" ipmask [ ports ] .
6redir ::= "rdr" ifname ipmask dport "->" ip [ "," ip ] [ ports ] options .
7
8dport ::= "port" portnum [ "-" portnum ] .
9ports ::= "ports" numports | "auto" .
10mapit ::= "map" | "bimap" .
11fromto ::= "from" object "to" object .
12ipmask ::= ip "/" bits | ip "/" mask | ip "netmask" mask .
13mapport ::= "portmap" tcpudp portnumber ":" portnumber .
14mapicmpid ::= "icmpidmap" icmp idnumber ":" idnumber .
15options ::= [ tcpudp ] [ rr ] .
16
17object  = addr [ port-comp | port-range ] .
18addr    = "any" | nummask | host-name [ "mask" ipaddr | "mask" hexnumber ] .
19port-comp = "port" compare port-num .
20port-range = "port" port-num range port-num .
21
22rr ::= "round-robin" .
23tcpudp ::= "tcp" | "udp" | "tcp/udp" .
24portnumber ::= number { numbers } | "auto" .
25idnumber ::= number { numbers } .
26ifname ::= 'A' - 'Z' { 'A' - 'Z' } numbers .
27
28numbers ::= '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' .
29