Bird.html will now be autogenerated.

author: Pavel Machek <pavel@ucw.cz> 2000-04-17 18:49:05 +0200
committer: Pavel Machek <pavel@ucw.cz> 2000-04-17 18:49:05 +0200
commit: f9b8bcca4eb1fdd8067a66a845b585af61335e3c (patch)
tree: 9702db020d3ac81db504af5aa96d14e3d8b2d13d /doc
parent: d37f899ba4e88b56a824fd44e7d81455c099bcba (diff)
download: bird-f9b8bcca4eb1fdd8067a66a845b585af61335e3c.tar
bird-f9b8bcca4eb1fdd8067a66a845b585af61335e3c.zip
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-<HTML><HEAD><TITLE>Bird</TITLE></HEAD><BODY>
-
-<!-- This is bird documentation system. It looks like html, but it is _not_ html: nonstandard
-    extensions are in use in order to auto-generate nice tex source. Use TT tag to markup short
-    texts that should be rendered in fixed-space font, and further specify what kind of text this
-    is. Currently TT file and TT conf are being used. For multi-line texts, use PRE section, again
-    with option saying what kind of section this is. Use DL conf for definition of configuration
-    keywords.
-
-    (set-fill-column 100)
-
-    Copyright 1999 Pavel Machek <pavel@ucw.cz>, distribute under GPL version 2 or later.
-
-  -->
-
-<TEX t="Insert nice, hand-generated title page here">
-
-<h1>Introduction</h1>
-
-<h2>What is bird</h2>
-
-<p>You may wonder what 'bird' means. It is acronym of 'Basic Internet Routing Daemon', and we think
-that's cool name. Its task is similar to what firmware of Cisco routers does, or what <A
-HREF="fixme">gated</A> does. However, you can not run Cisco's firmware on "normal" computer and
-gated is really hard to configure and comes under wrong license. Bird is being developed on Charles
-University, Prague, and can be freely distributed under terms of GNU General Public License. Bird is
-designed to run on unix and unix-like systems, it is primarily developed on Linux.
-
-<h2>About this documentation</h2>
-
-<p>This documentation can have 4 forms: extended html (this is master copy), html with stripped
-extensions, ascii text (generated from html) and dvi/postscript (generated from html using
-html2latex and latex). You should always edit master copy; if you do so be sure to read comment at
-beggining of file. If you want to view documentation, you can either launch your www browser at
-master copy (and hope that browser does not have incompatible extensions from our), or you can
-generate nice printed copy.
-
-<h1>Configuration</h1>
-
-<p>Bird is configured using text configuration file. At startup, bird reads <TT file>bird.conf</TT>
-(unless -c command line parameter is given). Really simple configuration file might look like this:
-
-<PRE conf>
-
-protocol kernel {
-	persist;		# Don't remove routes on bird shutdown
-	scan time 20;		# Scan kernel routing table every 20 seconds
-	export all;		# Default is export none
-}
-
-protocol device {
-	scan time 10;		# Scan interfaces every 10 seconds
-}
-
-protocol rip {
-	export all;
-	import all;
-}
-</PRE>
-
-<p>You can find example of more complicated configuration file in <TT file>doc/bird.conf.example</TT>.
-
-<h1>Filters</h1>
-
-<h2>Introduction</h2>
-
-<p>Bird contains rather simple programming language. (No, it can not yet read mail :-). There are
-two objects in this language: filters and functions. Filters are called by bird core when route is
-being passed between protocol and main routing table, and filters may call functions. Functions may
-call other functions but recursion is not allowed. Filter language contains control structures such
-as if's and switches, but it allows no loops. Filters are
-interpretted. Filter using many features can be found in <TT file>filter/test.conf</TT>. 
-
-<p>There's one strange thing with filter language: it does not permit you to create loops. There's
-no equivalent of while() or for() command, and recursive functions are not permitted.
-
-<p pgm>You can find sources of filters language in <TT file>filter/</TT> directory. <TT
-file>filter/config.Y</TT> contains filter gramar, and basically translates source from user into
-tree of <TT c>f_inst</TT> structures. These trees are later interpreted using code in <TT
-file>filter/filter.c</TT>. Filters internally work with values/variables in <TT c>struct f_val</TT>,
-which contains type of value and value.
-
-<p>Filter basically looks like this:
-
-<PRE filt>
-filter not_too_far
-int var;
-{
-	if defined( rip_metric ) then
-		var = rip_metric;
-	else {
-		var = 1;
-		rip_metric = 1;
-	}
-	if rip_metric &gt; 10 then
-		reject "RIP metric is too big";
-	else
-		accept "ok";
-}
-</PRE>
-
-<p>As you can see, filter has a header, list of local variables, and body. Header consists of <TT
-filt>filter</TT> keyword, followed by (unique) name of filter. List of local variables consists of
-pairs <TT filt><I>type name</I>;</TT>, where each pair defines one local variable. Body consists of
-<TT filt> { <I>statments</I> }</TT>. Statements are terminated by <TT filt>;</TT>. You can group
-several statments into one by <TT filt>{ <I>statments</I> }</TT> construction, that is usefull if
-you want to make bigger block of code conditional.
-
-<h2>Data types</h2>
-
-<p>Each variable and each value has certain type. Unlike C, filters distinguish between integers and
-booleans (that is to prevent you from shooting in the foot).
-
-<DL filt>
-	<DT>bool
-	  <DD>this is boolean type, it can have only two values, <TT filt>TRUE</TT> and <TT
-	  filt>FALSE</TT>. Boolean is not compatible with integer and is the only type you can use
-	  in if statments.
-
-	<DT>int
-	  <DD>this is common integer, you can expect it to store signed values from -2000000000 to
-	  +2000000000.
-
-	<DT>pair
-	  <DD>this is pair of two short integers. Each component can have values from 0 to
-	  65535. Constant of this type is written as <TT filt>(1234,5678)</TT>.
-
-	<DT>string
-	  <DD>this is string of characters. There are no ways to modify strings in filters. You can
-	  pass them between functions, assign to variable of type string, print such variables, but
-	  you can not concatenate two strings (for example). String constants are written as <TT
-	  filt>"This is string constant"</TT>.
-
-	<DT>ip
-	  <DD>this type can hold single ip address. Depending on version of bird you are using, it
-	  can be ipv4 or ipv6 address. Ipv4 addresses addresses are written (as you would expect) as
-	  <TT filt>1.2.3.4</TT>. You can apply special operator <TT filt>.mask(<I>num</I>)</TT>
-	  on values of type ip. It masks out all but first <TT filt><I>num</I></TT> bits from ip
-	  address. So <TT filt>1.2.3.4.mask(8) = 1.0.0.0</TT> is true.
-
-	<DT>prefix
-	  <DD>this type can hold ip address, prefix len pair. Prefixes are written as <TT filt><I>ip
-	  address</I>/<I>px len</I></TT>. There are two special operators on prefix: <TT
-	  filt>.ip</TT>, which separates ip address from the pair, and <TT filt>.len</TT>, which
-	  separates prefix len from the pair.
-
-	<DT>set int|ip|prefix|pair
-	  <DD>filters know four types of sets. Sets are similar to strings: you can pass them around
-	  but you can not modify them. Constant of type <TT filt>set int</TT> looks like <TT filt>
-	  [ 1, 2, 5..7 ]</TT>. As you can see, both simple values and ranges are permitted in
-	  sets. Sets of prefixes are special: you can specify which prefixes should match them by
-	  using <TT filt>[ 1.0.0.0/8+, 2.0.0.0/8-, 3.0.0.0/8{5,6} ]</TT>. 3.0.0.0/8{5,6} matches
-	  prefixes 3.X.X.X, whose prefixlength is 5 to 6. 3.0.0.0/8+ is shorthand for 3.0.0.0/{0,8},
-	  3.0.0.0/8- is shorthand for 3.0.0.0/{0,7}.
-
-	<DT>enum
-	  <DD>enumerational types are halfway-internal in the bird. You can not define your own
-	  variable of enumerational type, but some pre-defined variables are of enumerational
-	  type. Enumerational types are incompatible with each other, again, its for your
-	  protection.
-</DL>
-
-<h2>Operations</h2>
-
-<p>Filter language supports common integer operations (+,-,*,/), parenthesis (a*(b+c)), comparation
-(a=b, a!=b, a&lt;b, a&gt;=b). Special operators include ~ for "in" operation. In operation can be
-used on element and set of that elements, or on ip and prefix, or on prefix and prefix. Its result
-is true if element is in given set or if ip adress is inside given prefix.
-
-<h2>Functions</h2>
-
-<p>Bird supports functions, so that you don't have to repeat same blocks of code over and
-over. Functions can have zero or more parameters, and can have local variables. Function basically
-looks like this:
-
-<PRE filt>
-function name ()
-int local_variable;
-{
-	local_variable = 5;
-}
-
-function with_parameters (int parameter)
-{
-	print parameter;
-}
-</PRE>
-
-<p>Unlike C, variables are declared after function line but before first {. You can not declare
-variables in nested blocks. Functions are called like in C: <TT filt>name(); with_parameters(5);</TT>.
-
-<p>Filters are declared in similar way to functions, except they can not have explicit
-parameters. They get route table entry as implicit parameter.
-
-<h2>Control structures</h2>
-
-<p>Filters support two control structures: if/then/else and case. Syntax of if/then/else is <TT
-filt>if <I>expression</I> then <I>command</I>; else <I>command</I>;<TT> and you can use <TT filt>{
-<I>command_1</I>; <I>command_2</I>; <I>...</I> }</TT> instead of one or both commands. <TT
-filt>else</TT> clause may be ommited. Case is used like this:
-
-<PRE filt>
-        case <I>argument</I> {
-        2: print "dva"; print "jeste jednou dva";
-        3 .. 5: print "tri az pet";
-        else: print "neco jineho";
-        }
-</PRE>
-
-where <I>argument</I> is any argument that can be on the left side of ~ operator, and anything that
-could be member of set is allowed before :. Multiple commands are allowed without {} grouping. If
-argument matches neither of : clauses, else: clause is used. (Case is actually implemented as set
-matching, internally.)
-
-<h1>Protocols</h1>
-
-<h2>Rip</h2>
-
-<h3>Introduction</h3>
-
-<p>Rip protocol (sometimes called Rest In Pieces) is simple protocol, where each router broadcasts
-distances to all networks he can reach. When router hears distance to other network, it increments
-it and broadcasts it back. Broadcasts are done in regular intervals. Therefore, if some network goes
-unreachable, routers keep telling each other that distance is old distance plus 1 (actually, plus
-interface metric, which is usually one). After some time, distance reaches infinity (that's 15 in
-rip) and all routers know that network is unreachable. Rip tries to minimize situations where
-counting to infinity is neccessary, because it is slow. Due to infinity being 16, you can not use
-rip on networks where maximal distance is bigger than 15 hosts. You can read more about rip at <A
-HREF="fixme">rfc1234</A>.
-
-<h3>Configuration</h3>
-
-<p>In addition to options generic to other protocols, rip supports following options:
-
-<DL conf>
-	<DT>authentication none|password|md5
-	  <DD>selects authenticaion method to use. None means that packets are not authenticated at
-	  all, password means that plaintext password is embedded into each packet, and md5 means
-	  that packets are authenticated using md5 cryptographics hash. See <A
-	  HREF="fixme">rfc1234</A>. If you set authentication to non-none, it is good idea to add
-	  <TT conf>passwords { }</TT> section.
-</DL>
-
-<p>There are two options that can be specified per-interface. First is <TT conf>metric</TT>, with
-default one.  Second is <TT conf>mode broadcast|quiet|nolisten|version1</TT>, it selects mode for
-rip to work in. If nothing is specified, rip runs in multicasts mode. <TT conf>version1</TT> is
-currently equivalent to <TT conf>broadcast</TT>, and it makes rip talk at broadcast address even
-through multicast mode is possible. <TT conf>quiet</TT> option means that rip will not transmit
-periodic messages onto this interface and <TT conf>nolisten</TT> means that rip will talk to this
-interface but not listen on it.
-
-<p>Following options generally override specified behaviour from rfc. If you use any of these
-options, bird will no longer be rfc-compatible, which means it will not be able to talk to anything
-other than equally (mis-)configured bird. I warned you.
-
-<DL conf>
-	<DT>port <I>number</I>
-	  <DD>selects IP port to operate on, default 520. (This is usefull when testing bird, if you
-	  set this to address &gt;1024, you will not need to run bird with uid==0).
-
-	<DT>infinity <I>number</I>
-	  <DD>select value of infinity, default 16. Bigger values will make protocol convergence
-	  even slower.
-
-	<DT>period <I>number</I>
-	  <DD>specifies number of seconds between periodic updates. Default is 30 seconds. Lower
-	  number will mean faster convergence but bigger network load.
-
-	<DT>timeouttime <I>number</I>
-	  <DD>specifies how old route has to be to be considered unreachable. Default is 4*period.
-
-	<DT>garbagetime <I>number</I>
-	  <DD>specifies how old route has to be to be discarded. Default is 10*period.
-</DL>
-
-<p>In addition, rip defines two filter variables, both of type it. <TT filt>rip_metric</TT> is rip
-metric of current route, <TT filt>rip_tag</TT> is tag of current route.
-
-<pre conf>
-
-protocol rip MyRIP_test {
-        debug all;
-        port 1520;
-        period 7;
-        garbagetime 60;
-        interface "*";
-        honour neighbour;
-        passwords { password "ahoj" from 0 to 10;
-                password "nazdar" from 10;
-        }
-        authentication none;
-        import filter { print "importing"; accept; };
-        export filter { print "exporting"; accept; };
-}
-</pre>
-
-</BODY></HTML>
author	Pavel Machek <pavel@ucw.cz>	2000-04-17 18:49:05 +0200
committer	Pavel Machek <pavel@ucw.cz>	2000-04-17 18:49:05 +0200
commit	f9b8bcca4eb1fdd8067a66a845b585af61335e3c (patch)
tree	9702db020d3ac81db504af5aa96d14e3d8b2d13d /doc
parent	d37f899ba4e88b56a824fd44e7d81455c099bcba (diff)
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