Reimplementation of prefix sets.

Prefix sets were broken beyond any repair and have to be reimplemented.
They are reimplemented using a trie with bitmasks in nodes.
There is also change in the interpretation of minus prefix pattern,
but the old interpretation was already inconsistent with
the documentation and broken.

There is also some bugfixes in filter code related to set variables.

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 &tilde; [ 1.0.0.0/8{ 15 , 17 } ]</cf> is true, but
-	  <cf>1.0.0.0/8 &tilde; [ 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 &le; ip1 &le; len2</cf>.
+	  A valid prefix pattern has to satisfy <cf/low &le; 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 &tilde; [ 1.0.0.0/8{ 15 , 17 } ]</cf> is true,
+	  but <cf>1.0.0.0/16 &tilde; [ 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