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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/bird.sgml | 33 |
1 files changed, 27 insertions, 6 deletions
diff --git a/doc/bird.sgml b/doc/bird.sgml index a7cda82..2114151 100644 --- a/doc/bird.sgml +++ b/doc/bird.sgml @@ -508,12 +508,33 @@ incompatible with each other (that is to prevent you from shooting in the foot). Filters recognize four types of sets. Sets are similar to strings: you can pass them around but you can't modify them. Literals of type <cf>set int</cf> look like <cf> [ 1, 2, 5..7 ]</cf>. As you can see, both simple values and ranges are permitted in - sets. Sets of prefixes are special: you can specify which prefix lengths should match them by - using <cf>[ 1.0.0.0/8+, 2.0.0.0/8-, 3.0.0.0/8{5,6} ]</cf>. <cf>3.0.0.0/8{5,6}</cf> matches - prefixes <cf/3.X.X.X/ whose prefix length is 5 to 6. <cf><m>address</m>/<m>num</m>+</cf> is a shorthand for <cf><m>address</m>/{0,<m/num/}</cf>, - <cf><m>address</m>/<m/num/-</cf> is a shorthand for <cf><m>address</m>/{0,<m/num-1/}</cf>. For example, - <cf>1.2.0.0/16 ˜ [ 1.0.0.0/8{ 15 , 17 } ]</cf> is true, but - <cf>1.0.0.0/8 ˜ [ 1.0.0.0/8- ]</cf> is false. + sets. + + Sets of prefixes are special: their literals does not allow ranges, but allows + prefix patterns that are written as <cf><M>ipaddress</M>/<M>pxlen</M>{<M>low</M>,<M>high</M>}</cf>. + Prefix <cf><m>ip1</m>/<m>len1</m></cf> matches prefix pattern <cf><m>ip2</m>/<m>len2</m>{<m>l</m>, <m>h</m>}</cf> iff + the first <cf>min(len1, len2)</cf> bits of <cf/ip1/> and <cf/ip2/ are identical and <cf>len1 ≤ ip1 ≤ len2</cf>. + A valid prefix pattern has to satisfy <cf/low ≤ high/, but <cf/pxlen> is not constrained by <cf/low/ + or <cf/high/. Obviously, a prefix matches a prefix set literal iff it matches any prefix pattern in the + prefix set literal. + + There are also two shorthands for prefix patterns: <cf><m>address</m>/<m/len/+</cf> is a shorthand for + <cf><m>address</m>/<m/len/{<m/len/,<m/maxlen/}</cf> (where <cf><m>maxlen</m></c> is 32 for IPv4 and 128 for IPv6), + that means prefix <cf><m>address</m>/<m/len/</cf> and all its subprefixes. <cf><m>address</m>/<m/len/-</cf> + is a shorthand for <cf><m>address</m>/<m/len/{0,<m/len/}</cf>, that means prefix <cf><m>address</m>/<m/len/</cf> + and all its superprefixes (prefixes that contain it). + + For example, <cf>[ 1.0.0.0/8, 2.0.0.0/8+, 3.0.0.0/8-, 4.0.0.0/8{16,24} ]</cf> matches + prefix <cf>1.0.0.0/8</cf>, all subprefixes of <cf>2.0.0.0/8</cf>, all superprefixes of <cf>3.0.0.0/8</cf> and prefixes + <cf/4.X.X.X/ whose prefix length is 16 to 24. <cf>[ 0.0.0.0/0{20,24} ]</cf> matches all prefixes (regardless of + IP address) whose prefix length is 20 to 24, <cf>[ 1.2.3.4/32- ]</cf> matches any prefix that contains IP address + <cf>1.2.3.4</cf>. <cf>1.2.0.0/16 ˜ [ 1.0.0.0/8{ 15 , 17 } ]</cf> is true, + but <cf>1.0.0.0/16 ˜ [ 1.0.0.0/8- ]</cf> is false. + + Cisco-style patterns like <cf>10.0.0.0/8 ge 16 le 24</cf> can be expressed + in Bird as <cf>10.0.0.0/8{16,24}</cf>, <cf>192.168.0.0/16 le 24</cf> as + <cf>192.168.0.0/16{16,24}</cf> and <cf>192.168.0.0/16 ge 24</cf> as + <cf>192.168.0.0/16{24,32}</cf>. <tag/enum/ Enumeration types are fixed sets of possibilities. You can't define your own |