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Tue Aug 22 12:33:54 2017 UTC (6 years, 10 months ago) by misho
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bird 1.6.3

1: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> 2: <HTML> 3: <HEAD> 4: <META NAME="GENERATOR" CONTENT="LinuxDoc-Tools 1.0.9"> 5: <TITLE>BIRD User's Guide: Introduction</TITLE> 6: <LINK HREF="bird-2.html" REL=next> 7: 8: <LINK HREF="bird.html#toc1" REL=contents> 9: </HEAD> 10: <BODY> 11: <A HREF="bird-2.html">Next</A> 12: Previous 13: <A HREF="bird.html#toc1">Contents</A> 14: <HR> 15: <H2><A NAME="intro"></A> <A NAME="s1">1.</A> <A HREF="bird.html#toc1">Introduction</A></H2> 16: 17: <H2><A NAME="what-is-bird"></A> <A NAME="ss1.1">1.1</A> <A HREF="bird.html#toc1.1">What is BIRD</A> 18: </H2> 19: 20: The name `BIRD' is actually an acronym standing for `BIRD Internet Routing 21: Daemon'. Let's take a closer look at the meaning of the name: 22:  23: BIRD: Well, we think we have already explained that. It's an acronym 24: standing for `BIRD Internet Routing Daemon', you remember, don't you? :-) 25:  26: Internet Routing: It's a program (well, a daemon, as you are going to 27: discover in a moment) which works as a dynamic router in an Internet type 28: network (that is, in a network running either the IPv4 or the IPv6 protocol). 29: Routers are devices which forward packets between interconnected networks in 30: order to allow hosts not connected directly to the same local area network to 31: communicate with each other. They also communicate with the other routers in the 32: Internet to discover the topology of the network which allows them to find 33: optimal (in terms of some metric) rules for forwarding of packets (which are 34: called routing tables) and to adapt themselves to the changing conditions such 35: as outages of network links, building of new connections and so on. Most of 36: these routers are costly dedicated devices running obscure firmware which is 37: hard to configure and not open to any changes (on the other hand, their special 38: hardware design allows them to keep up with lots of high-speed network 39: interfaces, better than general-purpose computer does). Fortunately, most 40: operating systems of the UNIX family allow an ordinary computer to act as a 41: router and forward packets belonging to the other hosts, but only according to a 42: statically configured table. 43:  44: A Routing Daemon is in UNIX terminology a non-interactive program 45: running on background which does the dynamic part of Internet routing, that is 46: it communicates with the other routers, calculates routing tables and sends them 47: to the OS kernel which does the actual packet forwarding. There already exist 48: other such routing daemons: routed (RIP only), GateD (non-free), 49: <A HREF="http://www.zebra.org">Zebra</A> and 50: <A HREF="http://sourceforge.net/projects/mrt">MRTD</A>, 51: but their capabilities are limited and they are relatively hard to configure 52: and maintain. 53:  54: BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings, 55: to support all the routing technology used in the today's Internet or planned to 56: be used in near future and to have a clean extensible architecture allowing new 57: routing protocols to be incorporated easily. Among other features, BIRD 58: supports: 59:  60: <UL> 61: <LI>both IPv4 and IPv6 protocols</LI> 62: <LI>multiple routing tables</LI> 63: <LI>the Border Gateway Protocol (BGPv4)</LI> 64: <LI>the Routing Information Protocol (RIPv2)</LI> 65: <LI>the Open Shortest Path First protocol (OSPFv2, OSPFv3)</LI> 66: <LI>the Router Advertisements for IPv6 hosts</LI> 67: <LI>a virtual protocol for exchange of routes between different 68: routing tables on a single host</LI> 69: <LI>a command-line interface allowing on-line control and inspection 70: of status of the daemon</LI> 71: <LI>soft reconfiguration (no need to use complex online commands to 72: change the configuration, just edit the configuration file and 73: notify BIRD to re-read it and it will smoothly switch itself to 74: the new configuration, not disturbing routing protocols unless 75: they are affected by the configuration changes)</LI> 76: <LI>a powerful language for route filtering</LI> 77: </UL> 78:  79: BIRD has been developed at the Faculty of Math and Physics, Charles 80: University, Prague, Czech Republic as a student project. It can be freely 81: distributed under the terms of the GNU General Public License. 82:  83: BIRD has been designed to work on all UNIX-like systems. It has been 84: developed and tested under Linux 2.0 to 2.6, and then ported to FreeBSD, NetBSD 85: and OpenBSD, porting to other systems (even non-UNIX ones) should be relatively 86: easy due to its highly modular architecture. 87:  88: BIRD supports either IPv4 or IPv6 protocol, but have to be compiled separately 89: for each one. Therefore, a dualstack router would run two instances of BIRD (one 90: for IPv4 and one for IPv6), with completely separate setups (configuration 91: files, tools ...). 92:  93:  94: <H2><A NAME="install"></A> <A NAME="ss1.2">1.2</A> <A HREF="bird.html#toc1.2">Installing BIRD</A> 95: </H2> 96: 97: On a recent UNIX system with GNU development tools (GCC, binutils, m4, make) 98: and Perl, installing BIRD should be as easy as: 99:  100: <HR> 101: <PRE> 102: ./configure 103: make 104: make install 105: vi /usr/local/etc/bird.conf 106: bird 107: </PRE> 108: <HR> 109:  110: You can use <CODE>./configure --help</CODE> to get a list of configure 111: options. The most important ones are: <CODE>--enable-ipv6</CODE> which enables building 112: of an IPv6 version of BIRD, <CODE>--with-protocols=</CODE> to produce a slightly smaller 113: BIRD executable by configuring out routing protocols you don't use, and 114: <CODE>--prefix=</CODE> to install BIRD to a place different from <CODE>/usr/local</CODE>. 115:  116:  117: <H2><A NAME="argv"></A> <A NAME="ss1.3">1.3</A> <A HREF="bird.html#toc1.3">Running BIRD</A> 118: </H2> 119: 120: You can pass several command-line options to bird: 121:  122: <DL> 123: <DT><CODE> 124: <A NAME="argv-config"></A> -c config name</CODE><DD>use given configuration file instead of prefix<CODE>/etc/bird.conf</CODE>. 125:  126: <DT><CODE> 127: <A NAME="argv-debug"></A> -d</CODE><DD>enable debug messages and run bird in foreground. 128:  129: <DT><CODE> 130: <A NAME="argv-log-file"></A> -D filename of debug log</CODE><DD>log debugging information to given file instead of stderr. 131:  132: <DT><CODE> 133: <A NAME="argv-foreground"></A> -f</CODE><DD>run bird in foreground. 134:  135: <DT><CODE> 136: <A NAME="argv-group"></A> -g group</CODE><DD>use that group ID, see the next section for details. 137:  138: <DT><CODE> 139: <A NAME="argv-help"></A> -h, --help</CODE><DD>display command-line options to bird. 140:  141: <DT><CODE> 142: <A NAME="argv-local"></A> -l</CODE><DD>look for a configuration file and a communication socket in the current 143: working directory instead of in default system locations. However, paths 144: specified by options <CODE>-c</CODE>, <CODE>-s</CODE> have higher priority. 145:  146: <DT><CODE> 147: <A NAME="argv-parse"></A> -p</CODE><DD>just parse the config file and exit. Return value is zero if the config 148: file is valid, nonzero if there are some errors. 149:  150: <DT><CODE> 151: <A NAME="argv-pid"></A> -P name of PID file</CODE><DD>create a PID file with given filename. 152:  153: <DT><CODE> 154: <A NAME="argv-recovery"></A> -R</CODE><DD>apply graceful restart recovery after start. 155:  156: <DT><CODE> 157: <A NAME="argv-socket"></A> -s name of communication socket</CODE><DD>use given filename for a socket for communications with the client, 158: default is prefix<CODE>/var/run/bird.ctl</CODE>. 159:  160: <DT><CODE> 161: <A NAME="argv-user"></A> -u user</CODE><DD>drop privileges and use that user ID, see the next section for details. 162:  163: <DT><CODE> 164: <A NAME="argv-version"></A> --version</CODE><DD>display bird version. 165: </DL> 166:  167: BIRD writes messages about its work to log files or syslog (according to config). 168:  169:  170: <H2><A NAME="privileges"></A> <A NAME="ss1.4">1.4</A> <A HREF="bird.html#toc1.4">Privileges</A> 171: </H2> 172: 173: BIRD, as a routing daemon, uses several privileged operations (like setting 174: routing table and using raw sockets). Traditionally, BIRD is executed and runs 175: with root privileges, which may be prone to security problems. The recommended 176: way is to use a privilege restriction (options <CODE>-u</CODE>, <CODE>-g</CODE>). In that case 177: BIRD is executed with root privileges, but it changes its user and group ID to 178: an unprivileged ones, while using Linux capabilities to retain just required 179: privileges (capabilities CAP_NET_*). Note that the control socket is created 180: before the privileges are dropped, but the config file is read after that. The 181: privilege restriction is not implemented in BSD port of BIRD. 182:  183: An unprivileged user (as an argument to <CODE>-u</CODE> options) may be the user 184: <CODE>nobody</CODE>, but it is suggested to use a new dedicated user account (like 185: <CODE>bird</CODE>). The similar considerations apply for the group option, but there is 186: one more condition -- the users in the same group can use <CODE>birdc</CODE> to 187: control BIRD. 188:  189: Finally, there is a possibility to use external tools to run BIRD in an 190: environment with restricted privileges. This may need some configuration, but it 191: is generally easy -- BIRD needs just the standard library, privileges to read 192: the config file and create the control socket and the CAP_NET_* capabilities. 193:  194:  195: <HR> 196: <A HREF="bird-2.html">Next</A> 197: Previous 198: <A HREF="bird.html#toc1">Contents</A> 199: </BODY> 200: </HTML>