1 filter-rule = [ insert ] action in-out [ options ] [ tos ] [ ttl ]
2 [ proto ] [ ip ] [ group ].
4 insert = "@" decnumber .
5 action = block | "pass" | log | "count" | skip | auth | call .
6 in-out = "in" | "out" .
7 options = [ log ] [ "quick" ] [ "on" interface-name [ dup ] [ froute ] ] .
8 tos = "tos" decnumber | "tos" hexnumber .
9 ttl = "ttl" decnumber .
10 proto = "proto" protocol .
11 ip = srcdst [ flags ] [ with withopt ] [ icmp ] [ keep ] .
12 group = [ "head" decnumber ] [ "group" decnumber ] .
14 block = "block" [ icmp [return-code] | "return-rst" ] .
15 auth = "auth" | "preauth" .
16 log = "log" [ "body" ] [ "first" ] [ "or-block" ] [ "level" loglevel ] .
17 call = "call" [ "now" ] function-name .
18 skip = "skip" decnumber .
19 dup = "dup-to" interface-name[":"ipaddr] .
20 froute = "fastroute" | "to" interface-name .
21 protocol = "tcp/udp" | "udp" | "tcp" | "icmp" | decnumber .
22 srcdst = "all" | fromto .
23 fromto = "from" object "to" object .
25 icmp = "return-icmp" | "return-icmp-as-dest" .
26 loglevel = facility"."priority | priority .
27 object = addr [ port-comp | port-range ] .
28 addr = "any" | nummask | host-name [ "mask" ipaddr | "mask" hexnumber ] .
29 port-comp = "port" compare port-num .
30 port-range = "port" port-num range port-num .
31 flags = "flags" flag { flag } [ "/" flag { flag } ] .
32 with = "with" | "and" .
33 icmp = "icmp-type" icmp-type [ "code" decnumber ] .
34 return-code = "("icmp-code")" .
35 keep = "keep" "state" | "keep" "frags" .
37 nummask = host-name [ "/" decnumber ] .
38 host-name = ipaddr | hostname | "any" .
39 ipaddr = host-num "." host-num "." host-num "." host-num .
40 host-num = digit [ digit [ digit ] ] .
41 port-num = service-name | decnumber .
43 withopt = [ "not" | "no" ] opttype [ withopt ] .
44 opttype = "ipopts" | "short" | "frag" | "opt" ipopts .
45 optname = ipopts [ "," optname ] .
46 ipopts = optlist | "sec-class" [ secname ] .
47 secname = seclvl [ "," secname ] .
48 seclvl = "unclass" | "confid" | "reserv-1" | "reserv-2" | "reserv-3" |
49 "reserv-4" | "secret" | "topsecret" .
50 icmp-type = "unreach" | "echo" | "echorep" | "squench" | "redir" |
51 "timex" | "paramprob" | "timest" | "timestrep" | "inforeq" |
52 "inforep" | "maskreq" | "maskrep" | "routerad" |
53 "routersol" | decnumber .
54 icmp-code = decumber | "net-unr" | "host-unr" | "proto-unr" | "port-unr" |
55 "needfrag" | "srcfail" | "net-unk" | "host-unk" | "isolate" |
56 "net-prohib" | "host-prohib" | "net-tos" | "host-tos" |
57 "filter-prohib" | "host-preced" | "cutoff-preced" .
58 optlist = "nop" | "rr" | "zsu" | "mtup" | "mtur" | "encode" | "ts" | "tr" |
59 "sec" | "lsrr" | "e-sec" | "cipso" | "satid" | "ssrr" | "addext" |
60 "visa" | "imitd" | "eip" | "finn" .
61 facility = "kern" | "user" | "mail" | "daemon" | "auth" | "syslog" |
62 "lpr" | "news" | "uucp" | "cron" | "ftp" | "authpriv" |
63 "audit" | "logalert" | "local0" | "local1" | "local2" |
64 "local3" | "local4" | "local5" | "local6" | "local7" .
65 priority = "emerg" | "alert" | "crit" | "err" | "warn" | "notice" |
68 hexnumber = "0" "x" hexstring .
69 hexstring = hexdigit [ hexstring ] .
70 decnumber = digit [ decnumber ] .
72 compare = "=" | "!=" | "<" | ">" | "<=" | ">=" | "eq" | "ne" | "lt" | "gt" |
75 hexdigit = digit | "a" | "b" | "c" | "d" | "e" | "f" .
76 digit = "0" | "1" | "2" | "3" | "4" | "5" | "6" | "7" | "8" | "9" .
77 flag = "F" | "S" | "R" | "P" | "A" | "U" .