Bird.html will now be autogenerated.
This commit is contained in:
Pavel Machek
parent
d37f899ba4
commit
f9b8bcca4e
1 changed files with 0 additions and 297 deletions
297
doc/bird.html
297
doc/bird.html
|
|
@ -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>
|
||||
Loading…
Reference in a new issue