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| author | Pavel Machek <pavel@ucw.cz> | 2000-04-17 16:49:05 +0000 |
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| committer | Pavel Machek <pavel@ucw.cz> | 2000-04-17 16:49:05 +0000 |
| commit | f9b8bcca4eb1fdd8067a66a845b585af61335e3c (patch) | |
| tree | 9702db020d3ac81db504af5aa96d14e3d8b2d13d /doc/bird.html | |
| parent | d37f899ba4e88b56a824fd44e7d81455c099bcba (diff) | |
Bird.html will now be autogenerated.
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| -rw-r--r-- | doc/bird.html | 297 |
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diff --git a/doc/bird.html b/doc/bird.html deleted file mode 100644 index 5c157114..00000000 --- a/doc/bird.html +++ /dev/null @@ -1,297 +0,0 @@ -<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 > 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<b, a>=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 >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> |