INTRODUCTION
============

This perl script allows to setup an BGP adjacency with a BGP peer, monitor the messages and updates received from that peer, and to send out updates from a predefined set of NLRIs/attributes. BGP session and message handling is done by Net::BGP.

The script was mainly written to take a file with BGP route information (TABLE_DUMP_V2 format) and to inject these routes over a BGP adjacency. It grew a little over the time, and has some additional features to tweak and filter those routes before advertising them to the peer.

UPDATE messages received will be logged. Currently, there is no implementation of any local routing policy (except the features and sanity checks described at the NOTES section). Furthermore, no adj-rib-in and adj-rib-out databases are maintained.

Please note that you might need to patch Net::BGP to get correct handling of AGGREGATOR attributes (see the end of this file), this got fixed in Net::BGP version 0.12. 

You can redistribute and modify this script under the terms of the GNU General Public License version 3.

The script is hosted at http://bgpsimple.googlecode.com. Any bugfixes, suggestions and feature requests are more than welcome, you can reach me via email: the.einval (at) googlemail.com, or via the freenode IRC network, /msg einval. Please bear with me, im not a perl hacker.


USAGE
=====

bgp_simple.pl: Simple BGP peering and route injection script.

usage:
bgp_simple.pl: 
                -myas   ASNUMBER                # (mandatory) our AS number
                -myip   IP address              # (mandatory) our IP address to source the sesion from
                -peerip IP address              # (mandatory) peer IP address
                -peeras ASNUMBER                # (mandatory) peer AS number
                [-hide_output]                 	# (optional) completely hides ANY output to make this thing faster (printing all routes to console / ssh is overkill in most scenarios and slows this thing down)
		[-holdtime]	Seconds		# (optional) BGP hold time duration in seconds (default 60s)
		[-keepalive]	Seconds		# (optional) BGP KeepAlive timer duration in seconds (default 20s)
		[-nolisten]			# (optional) dont listen at $myip,179/tcp
                [-v]                            # (optional) provide verbose output to STDOUT, use twice to get debugs
                [-p file]                       # (optional) prefixes to advertise (bgpdump formatted)
                [-o file]                       # (optional) write all sent and received UPDATE messages to file
                [-m number]                     # (optional) maximum number of prefixes to advertise
                [-n IP address]                 # (optional) next hop self, overrides original value
                [-l number]                     # (optional) set default value for LOCAL_PREF
                [-dry]                          # (optional) dry run; dont build adjacency, but check prefix file (requires -p)
                [-f KEY=REGEX]                  # (optional) filter on input prefixes (requires -p), repeat for multiple filters
                                                        KEY is one of the following attributes (CaSE insensitive):

                                                        NEIG            originating neighbor
                                                        NLRI            NLRI/prefix(es)
                                                        ASPT            AS_PATH
                                                        ORIG            ORIGIN
                                                        NXHP            NEXT_HOP
                                                        LOCP            LOCAL_PREF
                                                        MED             MULTI_EXIT_DISC
                                                        COMM            COMMUNITY
                                                        ATOM            ATOMIC_AGGREGATE
                                                        AGG             AGGREGATOR

                                                        REGEX is a perl regular expression to be expected in a 
                                                        match statement (m/REGEX/)

Without any prefix file to import, only an adjacency is established and the received NLRIs, including their attributes, are logged.


GETTING ROUTE INFORMATION
=========================

The original intention of the script was to feed as many routes to a peer as possible for testing purposes. To get large amounts of real world prefixes, dumps from a DFZ attached peers must be retrieved. Luckily, there are some ressources that provide such dumps, for example RIPE RIS (http://www.ripe.net/projects/ris/rawdata.html). Simply fetch a full dump from http://data.ris.ripe.net/rrc00/ (bview.*). 

The script cannot work with this binary data, some conversion has to be done. To do that, get the bgpdump library/utility (http://www.ris.ripe.net/source/). Compile bgpdump, then feed the dump through it. Make sure to specify the -m option to produce the condensed format:

  zcat bview.20081221.0759.gz | bgpdump -m - > myroutes

The myroutes file now includes the information in text format, parseable by the script (-p option).

Example of such an input file (modified to show error handling):
$ head -5 myroutes
TABLE_DUMP2|1229846392|B|80.81.192.242|7575|3.0.0.0/88|7575 15412 9304 80|IGP|80.81.192.242|0|284|7575:1002 7575:2020 7575:6003 7575:8003|NAG||
TABLE_DUMP2|1229846392|B|80.81.192.242|7575|4.0.0.0/8|7575 2914 3356|IGP|80.81.192.242|0|284|7575:1003 7575:2019 7575:6003|AG|3356 4.69.130.2|
TABLE_DUMP2|1229846392|B|80.81.192.242|7575|4.0.0.0/9|7575 2914 3356|IGP|80.81.192.242|0|284|7575:1003 7575:2019 7575:6003|AG|3356 4.69.130.2|
TABLE_DUMP2|1229846392|B|80.81.192.242|7575|4.21.103.0/24|7575 2914 3549 46133|IGP|80.81.192.242|0|284|7575:1003 7575:02019 7575:6003|NAG||
TABLE_DUMP2|1229846392|B|80.81.192.242|7575|4.23.88.0/23|7575 2914 7018 46164|IGP|80.81.192.242|0|284|7575:1003 7575:2019 7575:6003|NAG||


NOTES
=====

The CLI options are pretty much self explaining. Without giving a file that includes NLRIs and attributes, the script will only establish an adjacency and print out UPDATE and NOTIFICATION messages received from the peer.

It is possible to do a test run (-dry), enabling to see what the script does without an BGP peering established.

Verbose output can be generated by specifying -v, use -v -v to get debug information.

Some attributes are currently ignored, including AS_SET. 32bit ASNs are ignored.

You can specify an upper limit on the amount of prefixes that should be advertised to the peer (-m), to ensure your peer doesnt run out of resources.

The script isnt daemonized, it always runs in the foreground. If a peering is reset, it automatically tries to reinitiate it. If a new adjacency comes up, updates will be sent again.

Beside some sanity checks, the script does not implement any sort of best route selection. The dumps usually include multiple route information for a prefix, because they contain data from some peerings (neighbors).

This means that the script will advertise all of them as an UPDATE message in a sequential order. The peer treats each UPDATE for a prefix as new, because it is expected that a single BGP peer only sends a single UPDATE about a prefix at a given time (its best route). This means that the last line in the prefix file will be the one that gets installed by the receiving peer. 

It is possible to specify filters to limit the scope of routes to advertise (-f option). You can specify multiple filters, but each KEY is expected only once.

-f NEIG='x.x.x.x' -f ASPT='^65500' is a valid combination, where -f NEIG='x.x.x.x' -f NEIG='y.y.y.y' will be accepted, but only the last key is respected then. -f NEIG='x.x.x.x|y.y.y.y' is valid, on the other hand.

The script tries to be a little predictive about what to send, depending on the peering type (iBGP/eBGP). For example, "artificial" LOCAL_PREF with the value 0 gets advertised to an iBGP peer, even if the source file doesnt provide this information (override with -l).

NEXT_HOP gets always altered for eBGP peerings, or for iBGP peerings that have the -n option set. When the -n option doesnt have an IP address specified, NEXT_HOP is set to "myip".


EXAMPLES
========

Simple iBGP peering (dry run), advertise up to 200 prefix lines from the file myroutes, spoof next hop address.

$ sudo ./bgp_simple.pl -myas 65500 -myip 192.168.10.1 -peerip 192.168.10.254 -peeras 65500 -p src/bgp/bgp_data/myroutes -dry -m 10 -n -v
---------------------------------------- CONFIG SUMMARY --------------------------------------------------
Configured for an iBGP session between me (ASN65500, 192.168.10.1) and peer (ASN65500, 192.168.10.254).
Generating verbose output, level 1.
Will use prefixes from file src/bgp/bgp_data/myroutes.
Maximum number of prefixes to be advertised: 10.
Will spoof next hop address to 192.168.10.1.
----------------------------------------------------------------------------------------------------------
Starting dry run.
Generated Update (not sent): prfx [20.137.0.0/21] aspath [2857 8928 3257 3549 21877 {4237}] locprf [0] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Generated Update (not sent): prfx [20.137.0.0/21] aspath [25560 3257 3549 21877 {4237}] locprf [0] comm [25560:49 25560:4001] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Generated Update (not sent): prfx [20.137.0.0/21] aspath [6695 12731 3549 21877 {4237}] locprf [0] comm [3549:4351 3549:30840] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Generated Update (not sent): prfx [20.137.0.0/21] aspath [12989 3549 21877 {4237}] locprf [0] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Generated Update (not sent): prfx [20.137.0.0/21] aspath [6762 3549 21877 {4237}] locprf [0] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Generated Update (not sent): prfx [20.137.0.0/21] aspath [30890 3356 3356 3549 21877 {4237}] locprf [0] comm [3356:2 3356:22 3356:86 3356:501 3356:666 3356:2065 30890:5999 30890:31666 30890:50003] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Generated Update (not sent): prfx [20.137.0.0/21] aspath [19151 19895 3257 3549 21877 {4237}] locprf [0] comm [3257:30072 3257:50001 3257:54400 3257:54401 19151:4000 19151:64001 19151:65050] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Generated Update (not sent): prfx [20.137.0.0/21] aspath [4589 3549 21877 {4237}] locprf [0] med [10000] comm [3549:4351 3549:30840 4589:2 4589:575 4589:13306] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Generated Update (not sent): prfx [20.137.0.0/21] aspath [29686 3257 3549 21877 {4237}] locprf [0] comm [29686:600 29686:603 29686:801] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Generated Update (not sent): prfx [20.137.0.0/21] aspath [6695 12731 3549 21877 {4237}] locprf [0] comm [3549:4351 3549:30840] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Dry run done, exiting.

Same example, but now a real session (notice the updates received from the peer):

$ sudo ./bgp_simple.pl -myas 65500 -myip 192.168.10.1 -peerip 192.168.10.254 -peeras 65500 -p src/bgp/bgp_data/myroutes -m 10 -n -v
---------------------------------------- CONFIG SUMMARY --------------------------------------------------
Configured for an iBGP session between me (ASN65500, 192.168.10.1) and peer (ASN65500, 192.168.10.254).
Generating verbose output, level 1.
Will use prefixes from file src/bgp/bgp_data/myroutes.
Maximum number of prefixes to be advertised: 10.
Will spoof next hop address to 192.168.10.1.
----------------------------------------------------------------------------------------------------------
Connection established with peer 192.168.10.254, AS 65500.
Update received from peer [192.168.10.254], ASN [65500]: prfx [192.168.0.0/16] aspath [] locprf [300] med [5000] comm [65535:65281 65535:65282] orig [IGP] agg [65500 192.168.10.254] nxthp [192.168.10.254]
Update received from peer [192.168.10.254], ASN [65500]: prfx [79.247.174.120/32 217.0.118.231/32] aspath [] locprf [300] med [5000] comm [65535:65281 65535:65282] orig [IGP] agg [] nxthp [192.168.10.254]
Sending full update.
Send Update: prfx [20.137.0.0/21] aspath [2857 8928 3257 3549 21877 {4237}] locprf [0] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.0.0/21] aspath [25560 3257 3549 21877 {4237}] locprf [0] comm [25560:49 25560:4001] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.0.0/21] aspath [6695 12731 3549 21877 {4237}] locprf [0] comm [3549:4351 3549:30840] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.0.0/21] aspath [12989 3549 21877 {4237}] locprf [0] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.0.0/21] aspath [6762 3549 21877 {4237}] locprf [0] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.0.0/21] aspath [30890 3356 3356 3549 21877 {4237}] locprf [0] comm [3356:2 3356:22 3356:86 3356:501 3356:666 3356:2065 30890:5999 30890:31666 30890:50003] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.0.0/21] aspath [19151 19895 3257 3549 21877 {4237}] locprf [0] comm [3257:30072 3257:50001 3257:54400 3257:54401 19151:4000 19151:64001 19151:65050] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.0.0/21] aspath [4589 3549 21877 {4237}] locprf [0] med [10000] comm [3549:4351 3549:30840 4589:2 4589:575 4589:13306] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.0.0/21] aspath [29686 3257 3549 21877 {4237}] locprf [0] comm [29686:600 29686:603 29686:801] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.0.0/21] aspath [6695 12731 3549 21877 {4237}] locprf [0] comm [3549:4351 3549:30840] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Full update sent.
^C

Still the same example, but with debug output and filters applied:

$ sudo ./bgp_simple.pl -myas 65500 -myip 192.168.10.1 -peerip 192.168.10.254 -peeras 65500 -p src/bgp/bgp_data/myroutes -m 10 -n -v -v -f ASPT='(^25560)|3491'
---------------------------------------- CONFIG SUMMARY --------------------------------------------------
Configured for an iBGP session between me (ASN65500, 192.168.10.1) and peer (ASN65500, 192.168.10.254).
Generating verbose output, level 2.
Will use prefixes from file src/bgp/bgp_data/myroutes.
Maximum number of prefixes to be advertised: 10.
Will spoof next hop address to 192.168.10.1.
Will apply filter to input file:
	ASPT =~ /(^25560)|3491/
----------------------------------------------------------------------------------------------------------
Connection established with peer 192.168.10.254, AS 65500.
Keepalive received from peer 192.168.10.254, AS 65500.
Update received from peer [192.168.10.254], ASN [65500]: prfx [192.168.0.0/16] aspath [] locprf [300] med [5000] comm [65535:65281 65535:65282] orig [IGP] agg [65500 192.168.10.254] nxthp [192.168.10.254]
Update received from peer [192.168.10.254], ASN [65500]: prfx [79.247.174.120/32 217.0.118.231/32] aspath [] locprf [300] med [5000] comm [65535:65281 65535:65282] orig [IGP] agg [] nxthp [192.168.10.254]
Keepalive received from peer 192.168.10.254, AS 65500.
Sending full update.
Line [1], Prefix [20.137.0.0/21] skipped due to ASPT filter (value was: 2857 8928 3257 3549 21877 {4237}).
Line [2], Prefix [20.137.0.0/21] - doesnt contain valid LOCAL_PREF value but we peer via iBGP (value forced to 0).
Send Update: prfx [20.137.0.0/21] aspath [25560 3257 3549 21877 {4237}] locprf [0] comm [25560:49 25560:4001] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Line [3], Prefix [20.137.0.0/21] skipped due to ASPT filter (value was: 6695 12731 3549 21877 {4237}).
Line [4], Prefix [20.137.0.0/21] skipped due to ASPT filter (value was: 12989 3549 21877 {4237}).

[...output skipped...]

Send Update: prfx [20.137.112.0/20] aspath [25560 3257 3549 206 {4237}] locprf [0] comm [25560:49 25560:4001] orig [IGP] agg [206 20.137.127.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.144.0/20] aspath [25560 3257 3549 206 {4237}] locprf [0] comm [25560:49 25560:4001] orig [IGP] agg [206 20.137.149.255] nxthp [192.168.10.1]
Send Update: prfx [20.137.160.0/20] aspath [25560 3257 3549 206 4237 {25784}] locprf [0] comm [25560:49 25560:4001] orig [INCOMPLETE] agg [4237 20.137.161.251] nxthp [192.168.10.1]
Send Update: prfx [20.137.176.0/20] aspath [25560 3257 3549 21877 {4237}] locprf [0] comm [25560:49 25560:4001] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.137.208.0/20] aspath [25560 3257 3549 3360 {4237}] locprf [0] comm [25560:49 25560:4001] orig [IGP] agg [3360 20.137.216.255] nxthp [192.168.10.1]
Send Update: prfx [20.137.240.0/20] aspath [25560 3257 3549 21877 {4237}] locprf [0] comm [25560:49 25560:4001] orig [IGP] agg [21877 20.137.31.194] nxthp [192.168.10.1]
Send Update: prfx [20.139.64.0/20] aspath [8881 3491 9583 17916 4237 {25784}] locprf [0] orig [INCOMPLETE] agg [4237 20.139.66.251] nxthp [192.168.10.1]
Full update sent.
Nothing to do.
Keepalive received from peer 192.168.10.254, AS 65500.
Nothing to do.
Nothing to do.
Nothing to do.
^C

DIFF FOR NET::BGP::Update
=========================

Net::BGP versions earlier than 0.12 need a patch for Update.pm to correctly construct updates that contain the AGGREGATOR attribute (CPAN BugID #42226):

$ diff -u /usr/local/share/perl/5.10.0/Net/BGP/Update_orig.pm /usr/local/share/perl/5.10.0/Net/BGP/Update.pm
--- /usr/local/share/perl/5.10.0/Net/BGP/Update_orig.pm 2008-06-21 06:42:00.000000000 +0200
+++ /usr/local/share/perl/5.10.0/Net/BGP/Update.pm      2008-12-25 23:05:17.000000000 +0100
@@ -642,10 +642,12 @@
 sub _encode_aggregator
 {
     my $this = shift();
-    $this->_encode_attr(BGP_PATH_ATTR_AGGREGATOR,
-                        pack('Cn',
-                             $this->{_aggregator}->[0],
-                             inet_aton($this->{_aggregator}->[1])));
+    my $buffer;
+
+    $buffer =  pack('n', $this->{_aggregator}->[0]);
+    $buffer .= inet_aton($this->{_aggregator}->[1]);
+
+    $this->_encode_attr(BGP_PATH_ATTR_AGGREGATOR, $buffer);
 }
 
 sub _encode_communities