The old quagga AS4 patch
19.10.2007 Two days ago, I received the news that quagga AS4
is suspectible to two kinds of DOS attacks if a wrong set
of attributes or a wrongly formatted AS4_PATH is received.
Both things are only possible by a faulty bgp/rfc4893 implementation
or real malicious intend (a software that injects something like that
Although I already stated the end of the AS4 patch four days ago,
I think you are right to expect a reaction in this special case.
So, you can read the original mail about
this and download a fix for the holes quagga-AS4 has open there.
15.10.2007 As of today, quagga mainline CVS has AS4 support
built-in. So please note that quagga cvs 20071014 is the latest
quagga you can use this patch on!
The work on AS4 I have done is finished by this milestone.
I will provide one (ONE!) patch in order to have complete freedom of
asdot representation in quagga again - something which Paul dumped
because he is opposed to it and thinks asplain is the better choice.
He is not alone in that regard. But there is the other party encompassing
the RIRs and the pioneer AS4 users, who are just as keen on using asdot
as Paul et all are on asplain. So what!? There are reasons
for both, though I personally have never seen a reason to finally
choose either one (from the implemention point of view).
I do not have the time or enthusiasm to support a CLI patch for a
number representation: it is tedious, and nothing fancy is achieved
by it. By providing one patch for the already used syntax I hope
to give a final service to "my" users. CLI changes are not very common
(excepting additions ;-)) so a patch should be good for quite a while.
Do not hold your breath for this one, I see no immediate need as long
as no *big* issues are added into quagga cvs after the AS4 patch, so
I will take some time for doing this.
Having said that,
I think I have finally come to the conclusion what would have been the
right choice for adding AS4 support, but it is too late now to go that
path: Choosing *any* representation without user interaction is wrong when
there are several representations to choose from. The right way
IMHO would have been to add the whole AS4 stuff, and show only AS_TRANS
to the user in place of any 4 byte as number, and give her no way to
enter or see any AS4 number in the
CLI at all. The whole AS4 stuff could thus have been hidden totally
from the user,
who stays in the AS2 world although quagga would have been already
truly AS4 'under
the hood'. The true 4-byte as numbers a user can enter and see if and
only if she gives the command which chooses whether asplain, asdot,
or asdot+ is to be used -
which will of course then be saved in the configuration. That way, the user
has made the choice, no default forces her (or even pushes her slightly)
to use something and any incompatibilites regarding regular expressions
are completely in the users domain. That is what I think is good,
open software: The user
decides what is used, and any choice which is deemed sensible by more
than a handful of people is there. But: too late.
The best ideas you always get after you have no way to use them any more...
Patch v09 released on 13.09.2007
10.09.2007 Quagga 0.99.9 has come out, and there have been some changes since
0.99.7. 0.99.9 has not got AS4 support yet - so I will be providing
a version v09 for the quagga CVS version 0.99.9-20070909 (i.e. the
version with the many 9s), skipping v08 for purely aesthetic reasons.
Because of the changes in quagga I'll have to do some basic tests
again before releasing v09, but you can expect it in the upcoming days.
And yes, I am still living and maintaining this ;-) though other things
kept me busy for a while.
Be aware that quagga 0.99.9 and cvs before 20070918 have two
regressions - you can not announce
ipv6 routes, and if you get an ipv6 default route quagga will take down
the session it is received on.
Workaround for the second is - do not let your peer send
you the default. Bug fix for the first is in cvs20070918, which
should have no problems with the v09 patch.
I am sorry that this site was down for a while. Someone mailed me that it was down... otherwise I'd have noticed that even later :-/.
Patch v07 released on 17.05.2007
existence of patch was posted on quagga-users and nanog (by others)
- patch is listed in quagga-resources
- most search engines find this with the terms "AS4 quagga".
positive feedback received (see further down).
waiting for further feedback and/or experiences from the community.
basic AS4 handling stable through the first 6 versions,
changes were in naming and in the "add-ons"
(extended communities and MRT dumps).
First enhancements in basic AS4 handling present in v07, read further down.
One BUG present in all 07 versions, bug fix available, read further down.
All of RIPE NCCs RIS RRCs have been moved to
Quagga 0.99.6 with AS4 patch v05 today!
Which means that all RIPE NCC
now show you true AS4 numbers (i.e. try the
regexp "\." <backslash><dot>).
And it is not only the
Looking Glasses, it is the whole RIS project, read
You are confronted with some new things when you enter the AS4 world,
and specifically when you use quagga to do this:
AS numbers which are larger than 65535.
So you need to know about
the format as numbers are in
and the related quagga configuration command.
MRT dumps which contain 4 byte AS numbers.
You need to be aware that quagga uses a new format for this, and
if you use MRT dumps.
Extended communities with 4 byte AS numbers.
The format on the wire for this is defined in
, and the CLI format you'll have to use to instruct quagga
to use this (and what to specify if you only use the old 2-byte-AS
extended communities) is described by
extended communities and quagga AS4
Sometimes, you'll want to know what happens, either just to see what's
going on or to
do some debugging, and quaggas
new as4 specific
and their output
may move you along in that case.
Basic AS4 handling.
If you really want to read the draft which defines the
basic AS4 handling, you'll have to dig into
in former times)
- but that is not necessary to use this patch.
Other AS4 background.
And if you have to much time and wonder why you have a choice
of several as number formats now, and why you as the user have
to specifiy whether to use an extended community for a 2 byte as or
the one for a 4 byte as, then you can read my
thoughts on as4.
History of this patch.
You can read about this in the log.
Things which happened in 2006 are now in the
- Patch base
The newest patch version 09 [available ASAP]
(there is NO version 08)
is based on cvs quagga 20070909, which is quite identical to
"official" 0.99.9. The only differences between v09 and v07 are:
the ibgp bug is fixed, and the patch base has changed.
If you are using 0.99.7 or older versions of quagga and want to patch
them, you are better off sticking to version v07 (with the ibgp-patch applied).
The patch 07 may even apply to earlier versions, but you are on your own
there. Applying 09 to earlier versions will run into problems.
Because of 09 being identical (AS4 semantic-wise) to 07 plus ibgp-patch, there is no
incremental patch from 07 to 09.
Be aware that there have been some changes in the internal quagga
structures between 20070430 (which v07 was based on) and 20070909, and v09 is basically
untested for now, so be careful, test it, and
please send feedback if it runs as smoothly as the other versions did.
Of course, v09 survived my small testbed ;-).
- Contents of the patch
The as4 patch changes *.[ch] files in the bgpd/ subdirectory of quagga
and a few bits in the doc/, tests/, and vtysh/ subdirectory
as everybody should have expected. No new files were added,
no file removed. Thus, no problems with the build process of
quagga - whichever one you may
use (debian package, redhat package, build with configure from source without
any packaging) - are to be expected, I hope.
- Semantics implemented
All actions implemented are defined in
in former times).
If anything shows up which is not handled as it is described in the RFC,
it is my fault: email me, and I'll try to correct the issue.
Quagga can use extended communities with 4 byte as numbers in them,
for the bits "on-the-wire".
For the syntax please refer to this documention;
you have to explicitly tell quagga to use the 4 byte wire-format.
Be aware that earlier versions used another syntax which encouraged
misinterpretations which is why I junked that.
The current available drafts for extended communities leave something open,
if you want to have some background on this, feel free to read my
thoughts on as4, but you will
need a bit of time for them.
The general one: I may have goofed in a lot of places. If you try
this patch, you do this on your own risk. This patch may
crash your quagga and all routers you peer with, but that is
entirely *your* risk. I have tried to give you something which
does not do these things, but YMMV.
A specific one: All things regarding AS_CONFED_* are
pretty much untested.
If you run a confederation you are more prone to stumble upon something
than you are if you are not running one.
- New commands
There is a new configuration command
'bgp asnum format (asdot|asdot+|asip|asplain)'
which sets the output format for as numbers.
The different formats are
The format of as numbers
has implications for your router configurations. I elaborated
a bit on that in my
thoughts on as4, but you will
need a bit of time for reading them .
There are two new debug commands
'debug bgp as4'
'debug bgp as4 segment'
which will try to fill up your logfile with hopefully useful
information if you enable them. The 'segment' debug is unsuited to
a full bgp routing table as it logs several lines for each route received,
so take care there.
You will find all the messages which are logged if you use
these debug commands as well as errors logged by the AS4 handling documented
If you find such, tell me, I'll try to find a solution.
But feed only as4 related bugs to me, please. And do test this thing
before going productive with it, and also tell me if you have no problems
at all (as soon as this patch is in quagga mainline, no further
positive feedbacks will be necessary).
Send any feedback by email. Success stories would be very welcome ;-).
If you do not mind it specifically when giving feedback, I'll put
relevant feedback right here on this web page.
I gave a presentation regarding quagga and the AS4 patch at
Tallinn on May 11th, 2007. The presentation is available via the
RIPE website, but you can also
directly download it (296674 Bytes).
The webcast of the presentation can also be downloaded from the RIPE website.
- DE-CIX technical meeting 20th September, 2007
I gave another presentation regarding RFC 4893 and the quagga AS4 patch
at the DE-CIX technical meeting on 20th September 2007. That presentation
is more-or-less the same as the Tallinn one, a bit beefed up and updated -
and you may download the slides as pdf here.
Feedback and/or bugs/enhancements in released version(s) of the patch itself
I am busy putting together v09, based on cvs20070909, which will
also be usable for official 0.99.9. In order to have more "9"s, I have
skipped number 08: there is and will be no version v08 ;-).
Coming back from my summer holidays on the Outer Hebrides I met Paul
Jakma in Glasgow and we had a nice afternoon talking about quagga.
The right way to go regarding as number representation in quagga with
AS4 is still debated between us, but we know (and have always
known - just so that nobody gets other ideas) that we both want to
have the "best" solution for the users. "Best" is very, very shady
if you look upon the representation. There may be no best solution
at all... That said, Paul had also already started the integration effort
into mainline - so that is in the works, too - but do not hold your breath.
Incoming bug report.
There is a setup in which the as-path synthesizing
(or do you call it reconciliation) dumps core. Found and reported by
Katsuyasu Toyama, who also supplied a correct patch for correcting
the problem which was found by his collegue Arifumi Matsumoto:
Bug (all patch version affected): if an AS4 quagga is talking with iBGP inside an AS to AS2 speakers (the AS the iBGP is taking place being an AS2)
and one of the AS2 speakers has an AS4 as an external neighbor, quagga
AS4 dumps core.
Reason: Access to uninitialized memory (yuck!). The corresponding
excaped me during coding and testing - and it took a while to hit someone,
this patch (1683 Bytes) to your AS4 quagga sources!
Should patch cleanly into version 07,
and you may ignore any conflict in the Changes files for other versions.
Workaround: Let an AS4 capable quagga speak to the external AS4 directly and
let all AS4 capable quaggas talk to each other (i.e. not "over" a non-AS4
positive feedback from Gert Doering,
who is currently involved in setting
up his AS3.3 on FreeBSD.
Version v07 released. This release makes the first real changes
in the core AS4 routines, and is thus based on the same CVS release as
version v06 to have things plainly in sight.
There are two changes: burn less memory, and send attributes in
Burn less memory
Versions 01-06 had extended the attribute structure by the AS4 values
as4_path, as4_aggragator and as4_aggregator_address - which increased
the structure by 12 bytes. Because the AS4 path was always freed
after all the necessary work was done the AS4 path never needed more
memory than that.
But the AS4 path handling does not need the
remaining 12 bytes either, so I chucked
them out of the structure again. This is in step with Paul's effords to
save memory where possible, and will make it easier to re-base the AS4 patch
after Pauls attribute structure changes because the AS4 patch now needs no
changes in the structure at all. And, if you have 500000 routes with
attributes in memory (say, full DFZ from two places), this will save
6 meg memory!
Send attributes in ascending order
Versions 01-06 send the AS4_PATH directly after AS_PATH, and AS4_AGGREGATOR
directly after AS_AGGREGATOR. This was done because the fact that AS4
stuff was to be send is determined when the AS2 counterparts are dealt with
RFC4271 states that "the sender of an
UPDATE message SHOULD order path attributes
within the UPDATE message in ascending order of attribute type",
something which quagga did not do in doing it as it did. Of course,
that is only a "SHOULD", not a must, so the implementation had the
freedom to do it as it did (no violation of the RFC, but using
Because it is not a big change to send the attributes in ascending
order of attribute type I changed the code to do just that.
This may help people out there who have routers which have a problem if
attributes do not arrive sorted the right way.
Kevin Loch and SUZUKI Shinsuke have informed me that
the AS4 patch is acting against this
"SHOULD" in the first sentence of this part of RFC4271:
"The sender of an UPDATE message SHOULD order path attributes
within the UPDATE message in ascending order of attribute type.
The receiver of an UPDATE message MUST be prepared to handle path
attributes within UPDATE messages that are out of order."
Interestingly, this has pointed out some routers violating the MUST
in the second sentence.
I'll handle this very useful feedback as a feature request: the next
version of the quagga AS4 patch will send AS4_PATH and
AS4_AGGREGATOR at the correct place.
I'll also provide for an 'update patch' to correct older versions of
already AS4 patched quagga sources in regard to that.
The current sending position of these
attributes has been motivated by implementation simplicity only, but there
is no deeper reason why quagga should continue to ignore the "SHOULD".
The changes are pretty straightforward, so I expect no difficulities
in resolving the issue. Expect version v07 pretty soon.
But this means: if you start using the AS4 patch in a
version up to and including v06 and one of your peers becomes unstable
at that time, you
may have the same problem: a peer (router) which relies on the order
of attributes and can not cope with attributes coming in not quite sorted.
Version v06 released. Mainly a re-base onto quagga cvs 20070430,
which mostly resembles quagga-0.99.7; on top of the re-base, the
"statsbugfix" (see below) is included and some left-overs of the term
"...as4_aspath..." have been
changed to "...as4_path...". So, the reason for releasing this
as a new version is a more or less to provide a "clean" patch when
you start with 0.99.7.
There were a some changes in the cvs version of bgpd in the last weeks
resulting in a lot of offsets if you use v05 on it, and I try to make your life as easy as possible.
There is an incremental patch from v05 to v06 here, too: remember that the
incremental patches DO NOT upgrade you to a current cvs version or to the
0.99.7 version. The incremental patches encompass changes in the AS4 stuff ONLY.
"32-bit AS numbers in the wild" is an article on
which links back to this site.
Note that Geoffs route (188.8.131.52/24 from 2.2) vanished only
for a few days - probably collecting Easter eggs ;-).
Btw, the re-appearing has been noticed by Jac Kloots
who also provides
a mrtg statistics on AS4
originated ipv4 prefixes present in the DFZ.
Jac Kloots tells nanog
that SURFnet is using AS4 quagga and is doing probably the
first ipv6 announcement originating from a 4 byte AS.
Cosmetical bug in all versions (found by Jac Kloots,
who will also
start announcing an ipv6 prefix
from 3.5 soon):
'sh ip bgp unicast statistics' always shows the Highest public ASN in asplain.
Reason: That there is an ASN in the statistics completely
eluded me - in fact it is stored in something called "counts", so no way
to grep for this ASN output...
My fault, no excuses ;-).
Solution: available, use v06 or later.
Or use this interim
short patch to update any
earlier version regading this.
A feedback update from
Jac Kloots arrived: He changed filters, and the SURFnet
is now visible worldwide as coming from 3.5.
He also says that "it
seems all works fine until now."
There are now 3 routes visible worldwide originating from
4 byte as numbers (listed here in the order they appeared):
Hm, Geoff said he
switched to quagga so it is
quite possible that
all three prefixes are quagga-originated!
- Geoffs beacon (184.108.40.206/24 from 2.2),
- SURFnets /20 (220.127.116.11/20 from 3.5), and
- RIPE NCCs beacon (18.104.22.168/24 from 3.7).
Erik Romijn tells me he has switched
all of RIPE NCCs RIS boxes to
quagga 0.99.6 with AS4 patch v05,
and "everything seems to be working fine".
If this runs without problems for some weeks we can all be sure
that the AS4 patch is solid as a rock - I hope so, of cause ;-).
Jac Kloots made an
out of the implicit one I mentioned on 09.03.2007. Many thanks for the
Version v05 released. Fixes the uncleanliness in extended community handling,
the hackiness of the mrt dumps,
and some other unclean thingies.
Solves: semantic impact of as number input format for extended communities,
non-draft (aka non-standard) MRT dump format.
Implicit feedback: Yesterday I saw one of the routes Jac Kloots
was talking about last month in the RIS looking glasses as coming
from AS_TRANS (second route in the world doing that). So I'd presume
SURFnets "3.5" has entered the real world using quagga.
Erik Romijn and Geoff Huston are busy testing AS4 in relation to RIS.
Geoff did some inter-operation AS4 testing with quagga and openBGPD,
and provided this
openBGPD has problems coping when presented with
a full routing table, but quagga has not.
Jac Kloots (SURFnet) tells me that SURFnet has got AS 3.5 from RIPE NCC,
and he is setting up an AS4 patched quagga which will start advertising
a route soon.
- 09.02.2007 (found by Erik Romijn, RIPE NCC):
Bug in versions v01-v03 of this patch: vtysh
can not cope with 'router bgp ASNUMBER' for all asnumbers possible.
Reason: Left vtysh completely alone when coding the patch. And that command must be dealt with in vtysh, too.
Solution: available, patch version 4, posted 2007-02-12
Workaround for versions 1-3: Do not use vtysh for bgp configuration, use telnet to bgpd directly.
Erik Romijn, RIPE NCC, provided a first
feedback for the patch
- 16.01.2007 (found by myself, after a related question from Erik Romijn):
Bug in v01 and v02 of this patch: The commands 'ip extcommunity-list <1-99>|standard' do not have ASN in their syntax, they have the old 'aa' there.
Further bug: Printing out an extcommunity list gets
rid of "0." if you define an asn32 extcommunity with an asn16 in it,
so asn32 extcommunities can not be differentiated from asn16 ones.
Saved configurations will then loose the information that an asn32
extcommunity has been supplied. (But, who will use an asn32 extcommunity
when the as number in question is smaller than 65536?) Another solution
would be to enforce an asn16 ecommunity when an asn16 is given with
leading "0." on input (would be logical). Guess a completely different
syntax (third solution) or even doing some more groundwork for extcommunities
would be best - something to
discuss! You will find some more explanation about what I am ranting
about here in my (rather longish)
thoughts on as4.
Reason: Forgot to code that :-(
Solution: available (force asdot+ output for asn32
extcommunities), patch version 3, posted 20070118
Better solution: available (change syntax for
extended commmunites), patch version 5, posted 20070314
- 11.01.2007 (found by Erik Romijn, RIPE NCC):
Bug in v01 of this patch: MRT dumps do not work, wrong data in as numbers.
(One) Reason: bgp_dump.c still handels as numbers as only 16 bit.
(Another) Reason: bgp_dump.c does not set the right message types for the 32bit things. Actually, some needed values are not officially defined yet... At least, that is an excuse for me not providing something working in the first place for this ;-)
Solution: available, patch version 2, posted 20070115.
Be aware that the MRT patches are still a bit preliminary. 32bittiness is hacked into the dumps
in the afi-fields, which is very ugly. A discussion has been started on the GROW wg (the mailing
and as soon as there are results, you will probably find another patch version here.
From the operational point of view this is sugar... but with this hacked version we will
probably have only libbgpdump which is able to read this format. Well, as far as we know
there is noone else who implemented asn32 dump reading anyway.
And a note for the folks knowing nothing whatsoever about MRT dumps: this whole MRT dump stuff
has no relationship with the basic asn32 semantics, it is only
for dumping bgp information(s) to file.
Newer solution: available (follow the new version of the corresponding draft), patch version 5, posted 20070314.
The patch is here (was expected on 2006-11-19,
but released on 2006-11-17 11:00h CET)!
Review and test, please!
Remember that the patch base is the stated cvs snapshot version of
quagga, not "the 0.99.6 version" or "the 0.99.7 version". Having said
that, official 0.99.6
resembles cvs version 20061208 and official 0.99.7 *mostly* resembles
version 20070430. As long as no big changes appear
in the bgpd subdirectory of cvs quagga, you will probably get away
with minor things like conflicts in Changelogs or such if you use the
newest patch on plain 0.99.7.
To apply a patch, change into the directory of a quagga version, and
call 'patch -p0 < PATCHFILE', where PATCHFILE is the patch you
Version 05 of the patch changes the syntax for extended
community values, so please read this.
Furthermore, version 05 is now able to do MRT dumps as defined in
, which came out on 20070307, so we
are very up-to-date regarding this.
Always use the newest version, the older versions are only here for
Whichever version you use (hopefully v07), you must also download
this bug fix patch (1683 Bytes)
to get no known bad surprises inside your running AS2 (see the bug
| Full Patch || if applied to|| expect || Remarks
quagga-cvs20061024-to-asn32-v01.patch (98358 Bytes)
Quagga CVS 20061024
1 offset of -1 line in
Quagga CVS 20061120
quagga-cvs20061201-asn32-v01.patch (100000 Bytes)
Quagga CVS 20061201
No functional changes.
Changed Changelogs (left virgin in first version, oups).
Cleaned conflict in bgp_debug.c due to other added debug command in cvs.
quagga-cvs20061208-asn32-v01.patch (98999 Bytes)
Quagga CVS 20061208
No functional changes in asn32 handling.
Re-based on CVS20061208.
'Stuck in closing' bug now solved in CVS base, got rid of it in this patch.
Quagga CVS 20061211
Quagga CVS 20070110
1 offset of -1 line in
1 conflict in bgpd/ChangeLog - may be ignored or easily resolved (no effects when compiling quagga)
quagga-cvs20070110-asn32-v02.patch (103423 Bytes)
Quagga CVS 20070110
1 offset of -1 line in
Re-based on CVS20070110.
Changes mostly in bgp_dump.[ch] in order to care for MRT dumps.
quagga-cvs20070110-asn32-v03.patch (104675 Bytes)
Quagga CVS 20070110
Some comments and the CLI prompt for ecommunity lists corrected.
Forced asdot+ output for asn32 ecommunity values (something to discuss).
1 offset of -1 line in
1 offset of -8 lines in
Renamed everything NEW* to AS4*, follow AS4 naming convention
(introduced by version 13 of the as4bytes draft) throughout the patch.
Fixed 'router bgp ASNUMBER' in vtysh.
Added two missing includes.
Quagga CVS 20070307
Re-based on CVS20070307.
Some more renames and minor cleanups.
New MRT handling by Erik Romijn.
New extended community handling.
Quagga CVS 20070430
Re-based on CVS20070430.
Rename the last AS4_ASPATHs to AS4_PATHs.
Fix statistics output "hightest public ASN" to use asnumber output format.
Quagga official 0.99.7
Quagga CVS 20070430
Removed AS4 stuff out of the attribute structure (no need to save it).
Changed order of sending attributes in UPDATE messages to be ascending again.
Quagga official 0.99.7
Quagga CVS 20070909
Put ibgp patch into main patch.
Re-base the patch on new cvs version.
Quagga official 0.99.9
The incremental patches are for the people who have already started to work with this.
If you would rather patch in the missing things than starting again with a CVS quagga,
you can upgrade your version with these patches.
Be aware that you miss changes between the cvs versions of quagga
when the cvs patch base changes between two patch
versions (i.e. from 04 to 05). This may or may not be what you want.
There is no incremental patch from v07 to v09, because there were changes
in quagga from 0.99.7 to 0.99.9 which changed structures, so you can not
use the changes from v07 to v09 without going from 0.99.7 to 0.99.9 anyway.
Encountered bugs in quagga cvs
Bugs encountered during development can be
found here. Interestingly, these bugs
are in the cvs code base and do not hit us in real life. At least,
we have the cause and a solution for one, and the cause of another one
- Provide more documentation:
Say something about the MRT patches, i.e. put the relevant parts of GROW
somewhere, so people know the format they are in.
- Change patch to a format suitable for inclusion into
Clean out comments big way, do not clutter the code e.g. with parts of
the draft or loud thoughts.
This will probably cause the patch to shrink to half its size.
Brush up some of the #defines - some usages are unreadable as-is.
Try to break this whole thing into pieces,
extcommunities and the MRT part can be done
in their own patches (they have no influence to the basic AS4 awareness).
Go to one representation of as numbers anywhere, leave no choice. Can
be done as soon (as late!) as the whole world agrees on what to use. (This
basically puts inclusion into mainstream quagga quite far in the future.)
The log of all actions taken when developing this was getting a bit
longish. So it now is here .
Feedback: j.kammer (at) eurodata.de