| filter-rule = [ insert ] action in-out [ options ] [ tos ] [ ttl ] |
| [ proto ] [ ip ] [ group ] [ tag ] [ pps ] . |
| |
| insert = "@" decnumber . |
| action = block | "pass" | log | "count" | auth | call . |
| in-out = "in" | "out" . |
| options = [ log ] [ "quick" ] [ onif [ dup ] [ froute ] ] . |
| tos = "tos" decnumber | "tos" hexnumber . |
| ttl = "ttl" decnumber . |
| proto = "proto" protocol . |
| ip = srcdst [ flags ] [ with withopt ] [ icmp ] [ keep ] . |
| group = [ "head" decnumber ] [ "group" decnumber ] . |
| pps = "pps" decnumber . |
| |
| onif = "on" interface-name [ "out-via" interface-name ] . |
| block = "block" [ return-icmp[return-code] | "return-rst" ] . |
| auth = "auth" | "preauth" . |
| log = "log" [ "body" ] [ "first" ] [ "or-block" ] [ "level" loglevel ] . |
| tag = "tag" tagid . |
| call = "call" [ "now" ] function-name "/" decnumber. |
| dup = "dup-to" interface-name[":"ipaddr] . |
| froute = "fastroute" | "to" interface-name . |
| replyto = "reply-to" interface-name [ ":" ipaddr ] . |
| protocol = "tcp/udp" | "udp" | "tcp" | "icmp" | decnumber . |
| srcdst = "all" | fromto . |
| fromto = "from" object "to" object . |
| |
| return-icmp = "return-icmp" | "return-icmp-as-dest" . |
| loglevel = facility"."priority | priority . |
| object = addr [ port-comp | port-range ] . |
| addr = "any" | nummask | host-name [ "mask" ipaddr | "mask" hexnumber ] . |
| port-comp = "port" compare port-num . |
| port-range = "port" port-num range port-num . |
| flags = "flags" flag { flag } [ "/" flag { flag } ] . |
| with = "with" | "and" . |
| icmp = "icmp-type" icmp-type [ "code" decnumber ] . |
| return-code = "("icmp-code")" . |
| keep = "keep" "state" [ "limit" number ] | "keep" "frags" . |
| |
| nummask = host-name [ "/" decnumber ] . |
| host-name = ipaddr | hostname | "any" . |
| ipaddr = host-num "." host-num "." host-num "." host-num . |
| host-num = digit [ digit [ digit ] ] . |
| port-num = service-name | decnumber . |
| |
| withopt = [ "not" | "no" ] opttype [ [ "," ] withopt ] . |
| opttype = "ipopts" | "short" | "nat" | "bad-src" | "lowttl" | "frag" | |
| "mbcast" | "opt" ipopts . |
| optname = ipopts [ "," optname ] . |
| ipopts = optlist | "sec-class" [ secname ] . |
| secname = seclvl [ "," secname ] . |
| seclvl = "unclass" | "confid" | "reserv-1" | "reserv-2" | "reserv-3" | |
| "reserv-4" | "secret" | "topsecret" . |
| icmp-type = "unreach" | "echo" | "echorep" | "squench" | "redir" | |
| "timex" | "paramprob" | "timest" | "timestrep" | "inforeq" | |
| "inforep" | "maskreq" | "maskrep" | "routerad" | |
| "routersol" | decnumber . |
| icmp-code = decumber | "net-unr" | "host-unr" | "proto-unr" | "port-unr" | |
| "needfrag" | "srcfail" | "net-unk" | "host-unk" | "isolate" | |
| "net-prohib" | "host-prohib" | "net-tos" | "host-tos" | |
| "filter-prohib" | "host-preced" | "cutoff-preced" . |
| optlist = "nop" | "rr" | "zsu" | "mtup" | "mtur" | "encode" | "ts" | "tr" | |
| "sec" | "lsrr" | "e-sec" | "cipso" | "satid" | "ssrr" | "addext" | |
| "visa" | "imitd" | "eip" | "finn" . |
| facility = "kern" | "user" | "mail" | "daemon" | "auth" | "syslog" | |
| "lpr" | "news" | "uucp" | "cron" | "ftp" | "authpriv" | |
| "audit" | "logalert" | "local0" | "local1" | "local2" | |
| "local3" | "local4" | "local5" | "local6" | "local7" . |
| priority = "emerg" | "alert" | "crit" | "err" | "warn" | "notice" | |
| "info" | "debug" . |
| |
| hexnumber = "0" "x" hexstring . |
| hexstring = hexdigit [ hexstring ] . |
| decnumber = digit [ decnumber ] . |
| |
| compare = "=" | "!=" | "<" | ">" | "<=" | ">=" | "eq" | "ne" | "lt" | "gt" | |
| "le" | "ge" . |
| range = "<>" | "><" . |
| hexdigit = digit | "a" | "b" | "c" | "d" | "e" | "f" . |
| digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" . |
| flag = "F" | "S" | "R" | "P" | "A" | "U" | "C" | "W" . |