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<html>
<head>
<meta http-equiv="Content-Type" content="text/html">
<title>FreeS/WAN FAQ</title>
<meta name="keywords" content="Linux, IPsec, VPN, security, FreeSWAN, FAQ">
<!--
Written by Sandy Harris for the Linux FreeS/WAN project
Freely distributable under the GNU General Public License
More information at www.freeswan.org
Feedback to users@lists.freeswan.org
CVS information:
RCS ID: $Id: faq.html,v 1.1 2004/03/15 20:35:24 as Exp $
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Revision number: $Revision: 1.1 $
CVS revision numbers do not correspond to FreeS/WAN release numbers.
-->
</head>
<body>
<h1>FreeS/WAN FAQ</h1>
<p>This is a collection of questions and answers, mostly taken from the
FreeS/WAN <a href="mail.html">mailing list</a>. See the project <a
href="http://www.freeswan.org/">web site</a> for more information. All the
FreeS/WAN documentation is online there.</p>
<p>Contributions to the FAQ are welcome. Please send them to the project <a
href="mail.html">mailing list</a>.</p>
<hr>
<h2><a name="questions">Index of FAQ questions</a></h2>
<ul>
<li><a href="#whatzit">What is FreeS/WAN?</a></li>
<li><a href="#problems">How do I report a problem or seek help?</a></li>
<li><a href="#generic">Can I get ...</a>
<ul>
<li><a href="#lemme_out">... an off-the-shelf system that includes
FreeS/WAN?</a></li>
<li><a href="#contractor">... contractors or staff who know
FreeS/WAN?</a></li>
<li><a href="#commercial">... commercial support?</a></li>
</ul>
</li>
<li><a href="#release">Release questions</a>
<ul>
<li><a href="#rel.current">What is the current release?</a></li>
<li><a href="#relwhen">When is the next release?</a></li>
<li><a href="#rel.bugs">Are there known bugs in the current
release?</a></li>
</ul>
</li>
<li><a href="mod_cons">Modifications and contributions</a>
<ul>
<li><a href="#modify.faq">Can I modify FreeS/WAN to ...?</a></li>
<li><a href="#contrib.faq">Can I contribute to the project?</a></li>
<li><a href="#ddoc.faq">Is there detailed design documentation?</a></li>
</ul>
</li>
<li><a href="#interact">Will FreeS/WAN work in my environment?</a>
<ul>
<li><a href="#interop.faq">Can FreeS/WAN talk to ... ?</a></li>
<li><a href="#old_to_new">Can different FreeS/WAN versions talk to each
other?</a></li>
<li><a href="#faq.bandwidth">Is there a limit on throughput?</a></li>
<li><a href="#faq.number">Is there a limit on number of
connections?</a></li>
<li><a href="#faq.speed">Is a ... fast enough to handle FreeS/WAN with
my loads?</a></li>
</ul>
</li>
<li><a href="#work_on">Will FreeS/WAN work on ...</a>
<ul>
<li><a href="#versions">... my version of Linux?</a></li>
<li><a href="#nonIntel.faq">... non-Intel CPUs?</a></li>
<li><a href="#multi.faq">... multiprocessors?</a></li>
<li><a href="#k.old">... an older kernel?</a></li>
<li><a href="#k.versions">... the latest kernel version?</a></li>
<li><a href="#interface.faq">... unusual network hardware?</a></li>
<li><a href="#vlan">... a VLAN (802.1q) network?</a></li>
</ul>
</li>
<li><a href="#features.faq">Does FreeS/WAN support ...</a>
<ul>
<li><a href="#VPN.faq">... site-to-site VPN applications</a></li>
<li><a href="#warrior.faq">... remote users connecting to a LAN</a></li>
<li><a href="#road.shared.possible">... remote users using shared
secret authentication?</a></li>
<li><a href="#wireless.faq">... wireless networks</a></li>
<li><a href="#PKIcert">... X.509 or other PKI certificates?</a></li>
<li><a href="#Radius">... user authentication (Radius, SecureID,
Smart Card ...)?</a></li>
<li><a href="#NATtraversal">... NAT traversal</a></li>
<li><a href="#virtID">... assigning a "virtual identity" to a remote
system?</a></li>
<li><a href="#noDES.faq">... single DES encryption?</a></li>
<li><a href="#AES.faq">... AES encryption?</a></li>
<li><a href="#other.cipher">... other encryption algorithms?</a></li>
</ul>
</li>
<li><a href="#canI">Can I ...</a>
<ul>
<li><a href="#policy.preconfig">...use policy groups along with
explicitly configured connections?</a></li>
<li><a href="#policy.off">...turn off policy groups?</a></li>
<!--
<li><a href="#policy.otherinterface">...use policy groups
on an interface other than <VAR>%defaultroute</VAR>?</a></li>
-->
<li><a href="#reload">... reload connection info without
restarting?</a></li>
<li><a href="#masq.faq">... use several masqueraded subnets?</a></li>
<li><a href="#dup_route">... use subnets masqueraded to the same
addresses?</a></li>
<li><a href="#road.masq">... assign a road warrior an address on my net
(a virtual identity)?</a></li>
<li><a href="#road.many">... support many road warriors with one
gateway?</a></li>
<li><a href="#road.PSK">... have many road warriors using shared secret
authentication?</a></li>
<li><a href="#QoS">... use Quality of Service routing with
FreeS/WAN?</a></li>
<li><a href="#deadtunnel">... recognise dead tunnels and shut them
down?</a></li>
<li><a href="#demanddial">... build IPsec tunnels over a demand-dialed
link?</a></li>
<li><a href="#GRE">... build GRE, L2TP or PPTP tunnels over IPsec?</a></li>
<li><a href="#NetBIOS">... use Network Neighborhood (Samba, NetBIOS) over IPsec?</a></li>
</ul>
</li>
<li><a href="#setup.faq">Life's little mysteries</a>
<ul>
<li><a href="#cantping">I cannot ping ....</a></li>
<li><a href="#forever">It takes forever to ...</a></li>
<li><a href="#route">I send packets to the tunnel with route(8) but
they vanish</a></li>
<li><a href="#down_route">When a tunnel goes down, packets
vanish</a></li>
<li><a href="#firewall_ate">The firewall ate my packets!</a></li>
<li><a href="#dropconn">Dropped connections</a></li>
<li><a href="#defaultroutegone">Disappearing %defaultroute</a></li>
<li><a href="#tcpdump.faq">TCPdump on the gateway shows strange
things</a></li>
<li><a href="#no_trace">Traceroute does not show anything between the
gateways</a></li>
</ul>
</li>
<li><a href="#man4debug">Testing in stages (or .... works but ...
doesn't)</a>
<ul>
<li><a href="#nomanual">Manually keyed connections don't work</a></li>
<li><a href="#spi_error">One manual connection works, but second one
fails</a></li>
<li><a href="#man_no_auto">Manual connections work, but automatic
keying doesn't</a></li>
<li><a href="#nocomp">IPsec works, but connections using compression
fail</a></li>
<li><a href="#pmtu.broken">Small packets work, but large transfers
fail</a></li>
<li><a href="#subsub">Subnet-to-subnet works, but tests from the
gateways don't</a></li>
</ul>
</li>
<li><a href="#compile.faq">Compilation problems</a>
<ul>
<li><a href="#gmp.h_missing">gmp.h: No such file or directory</a></li>
<li><a href="#noVM">... virtual memory exhausted</a></li>
</ul>
</li>
<li><a href="#error">Interpreting error messages</a>
<ul>
<li><a href="#route-client">route-client (or host) exited with status
7</a></li>
<li><a href="#unreachable">SIOCADDRT:Network is unreachable</a></li>
<li><a href="#modprobe">ipsec_setup: modprobe: Can't locate
moduleipsec</a></li>
<li><a href="#noKLIPS">ipsec_setup: Fatal error, kernel appears to lack
KLIPS</a></li>
<li><a href="#noDNS">ipsec_setup: ... failure to fetch key for ... from
DNS</a></li>
<li><a href="#dup_address">ipsec_setup: ... interfaces ... and ...
share address ...</a></li>
<li><a href="#kflags">ipsec_setup: Cannot adjust kernel flags</a></li>
<li><a href="#message_num">Message numbers (MI3, QR1, et cetera) in
Pluto messages</a></li>
<li><a href="#conn_name">Connection names in Pluto error
messages</a></li>
<li><a href="#cantorient">Pluto: ... can't orient connection</a></li>
<li><a href="#no.interface">... we have no ipsecN interface for either
end of this connection</a></li>
<li><a href="#noconn">Pluto: ... no connection is known</a></li>
<li><a href="#nosuit">Pluto: ... no suitable connection ...</a></li>
<li><a href="#noconn.auth">Pluto: ... no connection has been
authorized</a></li>
<li><a href="#noDESsupport">Pluto: ... OAKLEY_DES_CBC is not
supported.</a></li>
<li><a href="#notransform">Pluto: ... no acceptable transform</a></li>
<li><a href="#rsasigkey">rsasigkey dumps core</a></li>
<li><a href="#sig4">!Pluto failure!: ... exited with ... signal
4</a></li>
<li><a href="#econnrefused">ECONNREFUSED error message</a></li>
<li><a href="#no_eroute">klips_debug: ... no eroute!</a></li>
<li><a href="#SAused">... trouble writing to /dev/ipsec ... SA already
in use</a></li>
<li><a href="#ignore">... ignoring ... payload</a></li>
<li><a href="#unknown_rightcert">unknown parameter name "rightcert"</a></li>
</ul>
<li><a href="#spam">Why don't you restrict the mailing lists to reduce
spam?</a></li>
</ul>
<hr>
<h2><a name="whatzit">What is FreeS/WAN?</a></h2>
<p>FreeS/WAN is a Linux implementation of the <a
href="glossary.html#IPSEC">IPsec</a> protocols, providing security services
at the IP (Internet Protocol) level of the network.</p>
<p>For more detail, see our <a href="intro.html">introduction</a> document or
the FreeS/WAN project <a href="http://www.freeswan.org/">web site</a>.</p>
<p>To start setting it up, go to our <a href="quickstart.html">quickstart
guide</a>.</p>
<p>Our <a href="web.html">web links</a> document has information on <a
href="web.html#implement">IPsec for other systems</a>.</p>
<h2><a name="problems">How do I report a problem or seek help?</a></h2>
<DL>
<DT>Read our <a href="trouble.html">troubleshooting</a> document.</DT>
<DD><p>It may guide you to a solution. If not, see its
<a href="trouble.html#prob.report">problem reporting</a> section.</p>
<p>Basically, what it says is <strong>give us the output from <var>ipsec
barf</var> from both gateways</strong>. Without full information, we cannot
diagnose a problem. However, <var>ipsec barf</var> produces a lot of output.
If at all possible, <strong>please make barfs accessible via the web or
FTP</strong> rather than sending enormous mail messages.</p>
</DD>
<DT><strong>Use the <a href="mail.html">users mailing list</a> for problem
reports</strong>, rather than mailing developers directly.
</DT>
<DD>
<ul>
<li>This gives you access to more expertise, including users who may have
encountered and solved the same problems.</li>
<li>It is more likely to get a quick response. Developers may get behind on
email, or even ignore it entirely for a while, but a list message (given
a reasonable Subject: line) is certain to be read by a fair number of
people within hours.</li>
<li>It may also be important because of <a
href="politics.html#exlaw">cryptography export laws</a>. A US citizen who
provides technical assistance to foreign cryptographic work might be
charged under the arms export regulations. Such a charge would be easier
to defend if the discussion took place on a public mailing list than if
it were done in private mail.</li>
</ul>
</DD>
<DT>Try irc.freenode.net#freeswan.</DT>
<DD>
<p>FreeS/WAN developers, volunteers and users can often be found there.
Be patient and be
prepared to provide lots of information to support your question.</p>
<p>If your question was really interesting, and you found an answer,
please share that with the class by posting to the
<a href="mail.html">users mailing list</a>. That way others with the
same problem can find your answer in the archives.</p>
</DD>
<DT>Premium support is also available.</DT>
<DD>
<p>See the next several questions.</p>
</DD>
</DL>
<h2><a name="generic">Can I get ...</a></h2>
<h3><a name="lemme_out">Can I get an off-the-shelf system that includes
FreeS/WAN?</a></h3>
<p>There are a number of Linux distributions or firewall products which
include FreeS/WAN. See this <a href="intro.html#products">list</a>. Using one
of these, chosen to match your requirements and budget, may save you
considerable time and effort.</p>
<p>If you don't know your requirements, start by reading Schneier's <a
href="biblio.html#secrets">Secrets and Lies</a>. That gives the best overview
of security issues I have seen. Then consider hiring a consultant (see next
question) to help define your requirements.</p>
<h3><a name="consultant">Can I hire consultants or staff who know
FreeS/WAN?</a></h3>
<p>If you want the help of a contractor, or to hire staff with FreeS/WAN
expertise, you could:</p>
<ul>
<li>check availability in your area through your local Linux User Group (<a
href="http://lugww.counter.li.org/">LUG Index</a>)</li>
<li>try asking on our <a href="mail.html">mailing list</a></li>
</ul>
<p>For companies offerring support, see the next question.</p>
<h3><a name="commercial">Can I get commercial support?</a></h3>
<p>Many of the distributions or firewall products which include FreeS/WAN
(see this <a href="intro.html#products">list</a>) come with commercial
support or have it available as an option.</p>
<p>Various companies specialize in commercial support of open source
software. Our project leader was a founder of the first such company, Cygnus
Support. It has since been bought by <a
href="http://www.redhat.com">Redhat</a>. Another such firm is <a
href="http://www.linuxcare.com">Linuxcare</a>.</p>
<h2><a name="release">Release questions</a></h2>
<h3><a name="rel.current">What is the current release?</a></h3>
<p>The current release is the highest-numbered tarball on our <a
href="ftp://ftp.xs4all.nl/pub/crypto/freeswan">distribution site</a>. Almost
always, any of <a href="intro.html#mirrors">the mirrors</a> will have the
same file, though perhaps not for a day or so after a release.</p>
<p>Unfortunately, the web site is not always updated as quickly as it should
be.</p>
<h3><a name="relwhen">When is the next release?</a></h3>
<p>We try to do a release approximately every six to eight weeks.
</p>
<p>If pre-release tests fail and the fix appears complex, or more generally
if the code does not appear stable when a release is scheduled, we will just
skip that release.</p>
<p>For serious bugs, we may bring out an extra bug-fix release. These get
numbers in the normal release series. For example, there was a bug found in
FreeS/WAN 1.6, so we did another release less than two weeks later. The
bug-fix release was called 1.7.</p>
<h3><a name="rel.bugs">Are there known bugs in the current release?</a></h3>
<p>Any problems we are aware of at the time of a release are documented in
the <a href="../BUGS">BUGS</a> file for that release. You should also look at
the <a href="../CHANGES">CHANGES</a> file.</p>
<p>Bugs discovered after a release are discussed on the <a
href="mail.html">mailing lists</a>. The easiest way to check for any problems
in the current code would be to peruse the
<a href="http://lists.freeswan.org/pipermail/briefs">List In Brief</a>.</p>
<h2><a name="mod_cons">Modifications and contributions</a></h2>
<h3><a name="modify.faq">Can I modify FreeS/WAN to ...?</a></h3>
<p>You are free to modify FreeS/WAN in any way. See the discussion of <a
href="intro.html#licensing">licensing</a> in our introduction document.</p>
<p>Before investing much energy in any such project, we suggest that you</p>
<ul>
<li>check the list of <a href="web.html#patch">existing patches</a></li>
<li>post something about your project to the <a href="mail.html">design
mailing list</a></li>
</ul>
<p>This may prevent duplicated effort, or lead to interesting
collaborations.</p>
<h3><a name="contrib.faq">Can I contribute to the project?</a></h3>
In general, we welcome contributions from the community. Various contributed
patches, either to fix bugs or to add features, have been incorporated into
our distribution. Other patches, not yet included in the distribution, are
listed in our <a href="web.html#patch">web links</a> section.
<p>Users have also contributed heavily to documentation, both by creating
their own <a href="intro.html#howto">HowTos</a> and by posting things on the
<a href="mail.html">mailing lists</a> which I have quoted in these HTML
docs.</p>
<p>There are, however, some caveats.</p>
<p>FreeS/WAN is being implemented in Canada, by Canadians, largely to ensure
that is it is entirely free of export restrictions. See this <a
href="politics.html#status">discussion</a>. We <strong>cannot accept code
contributions from US residents or citizens</strong>, not even one-line bugs
fixes. The reasons for this were recently discussed extensively on the
mailing list, in a thread starting <a
href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2001/01/msg00111.html">here</a>.</p>
<p>Not all contributions are of interest to us. The project has a set of
fairly ambitious and quite specific goals, described in our <a
href="intro.html#goals">introduction</a>. Contributions that lead toward
these goals are likely to be welcomed enthusiastically. Other contributions
may be seen as lower priority, or even as a distraction.</p>
<p>Discussion of possible contributions takes place on the <a
href="mail.html">design mailing list</a>.</p>
<h3><a name="ddoc.faq">Is there detailed design documentation?</a></h3>
There are:
<ul>
<li><a href="rfc.html">RFCs</a> specifying the protocols we implement</li>
<li><a href="manpages.html">man pages</a> for our utilities, library
functions and file formats</li>
<li>comments in the source code</li>
<li><a href="index.html">HTML documentation</a> written primarily for
users</li>
<li>archived discussions from the <a href="mail.html">mailing lists</a></li>
<li>other papers mentioned in our <a
href="intro.html#applied">introduction</a></li>
</ul>
<p>The only formal design documents are a few papers in the last category
above. All the other categories, however, have things to say about design as
well.</p>
<h2><a name="interact">Will FreeS/WAN work in my environment?</a></h2>
<h3><a name="interop.faq">Can FreeS/WAN talk to ...?</a></h3>
<p>The IPsec protocols are designed to support interoperation. In theory, any
two IPsec implementations should be able to talk to each other. In practice,
it is considerably more complex. We have a whole <a
href="interop.html">interoperation document</a> devoted to this problem.</p>
<p>An important part of that document is links to the many <a
href="interop.html#otherpub">user-written HowTos</a> on interoperation
between FreeS/WAN and various other implementations. Often the users know
more than the developers about these issues (and almost always more than me
:-), so these documents may be your best resource.</p>
<h3><a name="old_to_new">Can different FreeS/WAN versions talk to each
other?</a></h3>
<p>Linux FreeS/WAN can interoperate with many IPsec implementations,
including earlier versions of Linux FreeS/WAN itself.</p>
<p>In a few cases, there are some complications. See our <a
href="interop.html#oldswan">interoperation</a> document for details.</p>
<h3><a name="faq.bandwidth">Is there a limit on throughput?</a></h3>
<p>There is no hard limit, but see below.</p>
<h3><a name="faq.number">Is there a limit on number of tunnels?</a></h3>
<p>There is no hard limit, but see next question.</p>
<h3><a name="faq.speed">Is a ... fast enough to handle FreeS/WAN with my
loads?</a></h3>
<p>A quick summary:</p>
<dl>
<dt>Even a limited machine can be useful</dt>
<dd>A 486 can handle a T1, ADSL or cable link, though the machine may be
breathing hard.</dd>
<dt>A mid-range PC (say 800 MHz with good network cards) can do a lot of
IPsec</dt>
<dd>With up to roughly 50 tunnels and aggregate bandwidth of 20 Megabits
per second, it willl have cycles left over for other tasks.</dd>
<dt>There are limits</dt>
<dd>Even a high end CPU will not come close to handling a fully loaded
100 Mbit/second Ethernet link.
<p>Beyond about 50 tunnels it needs careful management.</p>
</dd>
</dl>
<p>See our <a href="performance.html">FreeS/WAN performance</a> document for
details.</p>
<h2><a name="work_on">Will FreeS/WAN work on ... ?</a></h2>
<h3><a name="versions">Will FreeS/WAN run on my version of Linux?</a></h3>
<p>We build and test on Redhat distributions, but FreeS/WAN runs just fine on
several other distributions, sometimes with minor fiddles to adapt to the
local environment. Details are in our <a
href="compat.html#otherdist">compatibility</a> document. Also, some
distributions or products come with <a href="intro.html#products">FreeS/WAN
included</a>.</p>
<h3><a name="nonIntel.faq">Will FreeS/WAN run on non-Intel CPUs?</a></h3>
<p>FreeS/WAN is <strong>intended to run on all CPUs Linux supports</strong>.
We know of it being used in production on x86, ARM, Alpha and MIPS. It has
also had successful tests on PPC and SPARC, though we don't know of actual
use there. Details are in our <a href="compat.html#CPUs">compatibility</a>
document.</p>
<h3><a name="multi.faq">Will FreeS/WAN run on multiprocessors?</a></h3>
<p>FreeS/WAN is designed to work on any SMP architecture Linux supports, and
has been tested successfully on at least dual processor Intel architecture
machines. Details are in our <a
href="compat.html#multiprocessor">compatibility</a> document.</p>
<h3><a name="k.old">Will FreeS/WAN work on an older kernel?</a></h3>
<p>It might, but we strongly recommend using a recent 2.2 or 2.4 series
kernel. Sometimes the newer versions include security fixes which can be
quite important on a gateway.</p>
<p>Also, we use recent kernels for development and testing, so those are
better tested and, if you do encounter a problem, more easily supported. If
something breaks applying recent FreeS/WAN patches to an older kernel, then
"update your kernel" is almost certain to be the first thing we suggest. It
may be the only suggestion we have.</p>
<p>The precise kernel versions supported by a particular FreeS/WAN release
are given in the <a href="XX">README</a> file of that release.</p>
<p>See the following question for more on kernels.</p>
<h3><a name="k.versions">Will FreeS/WAN run on the latest kernel
version?</a></h3>
<p>Sometimes yes, but quite often, no.</p>
<p>Kernel versions supported are given in the <a href="../README">README</a>
file of each FreeS/WAN release. Typically, they are whatever production
kernels were current at the time of our release (or shortly before; we might
release for kernel <var>n</var> just as Linus releases <var>n+1</var>). Often
FreeS/WAN will work on slightly later kernels as well, but of course this
cannot be guaranteed.</p>
<p>For example, FreeS/WAN 1.91 was released for kernels 2.2.19 or 2.4.5, the
current kernels at the time. It also worked on 2.4.6, 2.4.7 and 2.4.8, but
2.4.9 had changes that caused compilation errors if it was patched with
FreeS/WAN 1.91.</p>
<p>When such changes appear, we put a fix in the FreeS/WAN snapshots, and
distribute it with our next release. However, this is not a high priority for
us, and it may take anything from a few days to several weeks for such a
problem to find its way to the top of our kernel programmer's To-Do list. In
the meanwhile, you have two choices:</p>
<ul>
<li>either stick with a slightly older kernel, even if it is not the latest
and greatest. This is recommended for production systems; new versions
may have new bugs.</li>
<li>or fix the problem yourself and send us a patch, via the <a
href="mail.html">Users mailing list</a>.</li>
</ul>
<p>We don't even try to keep up with kernel changes outside the main 2.2 and
2.4 branches, such as the 2.4.x-ac patched versions from Alan Cox or the 2.5
series of development kernels. We'd rather work on developing the FreeS/WAN
code than on chasing these moving targets. We are, however, happy to get
patches for problems discovered there.</p>
<p>See also the <a href="install.html#choosek">Choosing a kernel</a> section
of our installation document.</p>
<h3><a name="interface.faq">Will FreeS/WAN work on unusual network
hardware?</a></h3>
<p>IPsec is designed to work over any network that IP works over, and
FreeS/WAN is intended to work over any network interface hardware that Linux
supports.</p>
<p>If you have working IP on some unusual interface -- perhaps Arcnet, Token
Ring, ATM or Gigabit Ethernet -- then IPsec should "just work".</p>
<p>That said, practice is sometimes less tractable than theory. Our testing
is done almost entirely on:</p>
<ul>
<li>10 or 100 Mbit Ethernet</li>
<li>ADSL or cable connections, with and without PPPoE</li>
<li>IEEE 802.11 wireless LANs (see <a href="#wireless.faq">below</a>)</li>
</ul>
<p>If you have some other interface, especially an uncommon one, it is
entirely possible you will get bitten either by a FreeS/WAN bug which our
testing did not turn up, or by a bug in the driver that shows up only with
our loads.</p>
<p>If IP works on your interface and FreeS/WAN doesn't, seek help on the <a
href="mail.html">mailing lists</a>.</p>
<p>Another FAQ section describes <a href="#pmtu.broken">MTU problems</a>.
These are a possibility for some interfaces.</p>
<h3><a name="vlan">Will FreeS/WAN work on a VLAN (802.1q) network?</a></h3>
<p>
Yes, FreeSwan works fine, though some network drivers have problems
with jumbo sized ethernet frames. If you used interfaces=%defaultroute
you do not need to change anything, but if you specified an interface
(eg eth0) then remember you must change that to reflect the VLAN
interface (eg eth0.2 for VLAN ID 2).
</p>
<p>
The "eepro100" module is known to be broken, use the e100 driver
for those cards instead (included in 2.4 as 'alternative driver' for
the Intel EtherExpressPro/100.
</p>
<p>
You do not need to change any MTU setting (those are workarounds
that are only needed for buggy drivers)
</p>
<p><em>This FAQ contributed by Paul Wouters.</em></p>
<h2><a name="features.faq">Does FreeS/WAN support ...</a></h2>
<p>For a discussion of which parts of the IPsec specifications FreeS/WAN does
and does not implement, see our <a href="compat.html#spec">compatibility</a>
document.</p>
<p>For information on some often-requested features, see below.</p>
<h3><a name="VPN.faq"></a>Does FreeS/WAN support site-to-site VPN
(<A HREF="glossary.html#VPN">Virtual Private Network</A>)
applications?</h3>
<p>Absolutely. See this FreeS/WAN-FreeS/WAN
<A HREF="config.html">configuration example</A>.
If only one site is using FreeS/WAN, there may be a relevant HOWTO on our
<A HREF="interop.html">interop page</A>.
</p>
<h3><a name="warrior.faq">Does FreeS/WAN support remote users connecting to a
LAN?</a></h3>
<p>Yes. We call the remote users "Road Warriors". Check out our
FreeS/WAN-FreeS/WAN
<A HREF="config.html#config.rw">Road Warrior Configuration Example</A>.</P>
<p>If your Road Warrior is a Windows or Mac PC, you may need to
install an IPsec implementation on that machine.
Our <A HREF="interop.html">interop</A> page lists many available brands,
and features links to several HOWTOs.
<h3><a name="road.shared.possible">Does FreeS/WAN support remote users using
shared secret authentication?</a></h3>
<p><strong>Yes, but</strong> there are severe restrictions, so <strong>we
strongly recommend using </strong><a
href="glossary.html#RSA"><strong>RSA</strong></a><strong> keys for
</strong> <a
href="glossary.html#authentication"><strong>authentication</strong></a>
<strong>
instead</strong>.</p>
<p>See this <a href="#road.PSK">FAQ question</a>.</p>
<h3><a name="wireless.faq">Does FreeS/WAN support wireless networks?</a></h3>
<p>Yes, it is a common practice to use IPsec over wireless networks because
their built-in encryption, <a href="glossary.html#WEP">WEP</a>, is
insecure.</p>
<p>There is some <a href="adv_config.html#wireless.config">discussion</a> in
our advanced configuration document. See also the
<A HREF="http://www.wavesec.org">WaveSEC site</A>.</p>
<h3><a name="PKIcert">Does FreeS/WAN support X.509 or other PKI
certificates?</a></h3>
<P>Vanilla FreeS/WAN does not support X.509, but Andreas Steffen
and others have provided a popular, well-supported X.509 patch.</P>
<UL>
<LI><A HREF="http://www.strongsec.com/freeswan">patch</A>
</LI>
<LI><A HREF="http://www.freeswan.ca">Super FreeS/WAN</A> incorporates
this and other user-contributed patches.
</LI>
<LI>
Kai Martius' <A HREF="http://www.strongsec.com/freeswan/install.htm">X.509
Installation and Configuration Guide</A>
</LI>
</UL>
<P>
Linux FreeS/WAN features
<A HREF="quickstart.html">Opportunistic Encryption</A>, an alternative
Public Key Infrastructure based on Secure DNS.
</P>
<h3><a name="Radius">Does FreeS/WAN support user authentication (Radius,
SecureID, Smart Card...)?</a></h3>
<P>Andreas Steffen's <A HREF="http://www.strongsec.com/freeswan">X.509 patch</A> (v. 1.42+) supports Smart Cards. The patch
does not ship with vanilla FreeS/WAN, but will be incorporated into
<A HREF="http://www.freeswan.ca/">Super FreeS/WAN
2.01+</A>. The patch implements the PCKS#15
Cryptographic Token Information Format Standard, using the OpenSC smartcard
library functions.</P>
<P>Older news:</P>
<P>A user-supported patch to FreeS/WAN 1.3, for smart card style
authentication, is available on
<A HREF="http://alcatraz.webcriminals.com/~bastiaan/ipsec">Bastiaan's site</A>.
It supports skeyid and ibutton.
This patch is not part of Super FreeS/WAN.</p>
<p>For a while progress on this front was impeded by a lack of standard.
The IETF <a
href="http://www.ietf.org/html.charters/ipsra-charter.html">working group</a>
has now nearly completed its recommended solution to the problem; meanwhile
several vendors have implemented various things.</p>
<!--
<p>The <a href="web.html#patch">patches</a> section of our web links document
has links to some user work on this.</p>
-->
<p>Of course, there are various ways to avoid any requirement for user
authentication in IPsec. Consider the situation where road warriors build
IPsec tunnels to your office net and you are considering requiring user
authentication during tunnel negotiation. Alternatives include:</p>
<ul>
<li>If you can trust the road warrior machines, then set them up so that
only authorised users can create tunnels. If your road warriors use
laptops, consider the possibility of theft.</li>
<li>If the tunnel only provides access to particular servers and you can
trust those servers, then set the servers up to require user
authentication.</li>
</ul>
<p>If either of those is trustworthy, it is not clear that you need user
authentication in IPsec.</p>
<h3><a name="NATtraversal">Does FreeS/WAN support NAT traversal?</a></h3>
<p>Vanilla FreeS/WAN does not, but thanks to Mathieu Lafon and
Arkoon Network Security, there's a patch to support this.</P>
<UL>
<LI><A HREF="http://open-source.arkoon.net">patch and documentation</A>
</LI>
<LI><A HREF="http://www.freeswan.ca">Super FreeS/WAN</A> incorporates
this and other user-contributed patches.
</LI>
</UL>
<P>The NAT traversal patch has some issues with PSKs, so you may wish to
authenticate with RSA keys, or X.509 (requires a patch which is also
included in Super FreeS/WAN). Doing the latter also has
advantages when dealing with large numbers of clients who may be behind NAT;
instead of having to make an individual Roadwarrior connection for each
virtual IP, you can use the "rightsubnetwithin" parameter to specify a range.
See
<A HREF="http://www.strongsec.com/freeswan/install.htm#section_4.4">these
<VAR>rightsubnetwithin</VAR> instructions</A>.
</P>
<h3><a name="virtID">Does FreeS/WAN support assigning a "virtual identity" to
a remote system?</a></h3>
<p>Some IPsec implementations allow you to make the source address on packets
sent by a Road Warrior machine be something other than the address of its
interface to the Internet. This is sometimes described as assigning a virtual
identity to that machine.</p>
<p>FreeS/WAN does not directly support this, but it can be done. See this <a
href="#road.masq">FAQ question</a>.</p>
<h3><a name="noDES.faq">Does FreeS/WAN support single DES encryption?</a></h3>
<p><strong>No</strong>, single DES is not used either at the <a
href="glossary.html#IKE">IKE</a> level for negotiating connections or at the
<a href="glossary.html#IPsec">IPsec</a> level for actually building them.</p>
<p>Single DES is <a href="politics.html#desnotsecure">insecure</a>. As we see
it, it is more important to deliver real security than to comply with a
standard which has been subverted into allowing use of inadequate methods.
See this <a href="politics.html#weak">discussion</a>.</p>
<p>If you want to interoperate with an IPsec implementation which offers only
DES, see our <a href="interop.html#noDES">interoperation</a> document.</p>
<h3><a name="AES.faq">Does FreeS/WAN support AES encryption?</a></h3>
<p><a href="glossary.html#AES">AES</a> is a new US government <a
href="glossary.html#block">block cipher</a> standard to replace the obsolete
<a href="glossary.html#DES">DES</a>.</p>
<p>At time of writing (March 2002), the FreeS/WAN distribution does not yet
support AES but user-written <a href="web.html#patch">patches</a> are
available to add it. Our kernel programmer is working on integrating those
patches into the distribution, and there is active discussion of this on the
design mailimg list.</p>
<h3><a name="other.cipher">Does FreeS/WAN support other encryption
algorithms?</a></h3>
<p>Currently <a href="glossary.html#3DES">triple DES</a> is the only cipher
supported. AES will almost certainly be added (see previous question), and it
is likely that in the process we will also add the other two AES finalists
with open licensing, Twofish and Serpent.</p>
<p>We are extremely reluctant to add other ciphers. This would make both use
and maintenance of FreeS/WAN more complex without providing any clear
benefit. Complexity is emphatically not desirable in a security product.</p>
<p>Various users have written patches to add other ciphers. We provide <a
href="web.html#patch">links</a> to these.</p>
<h2><a name="canI">Can I ...</a></h2>
<h3><a name="policy.preconfig">Can I use policy groups along with
explicitly configured connections?</a></h3>
<p>Yes, you can, so long as you pay attention to the selection rule,
which can be summarized "the most specific
connection wins". We describe the rule in our
<A HREF="policygroups.html#policy.group.notes">policy groups</A> document,
and provide a more technical explanation in
<A HREF="manpage.d/ipsec.conf.5.html">man ipsec.conf</A>.
</p>
<p>A good guideline: If you have a regular connection defined in
<VAR>ipsec.conf</VAR>, ensure that a subset of that connection
is not listed in a less restrictive policy group. Otherwise,
FreeS/WAN will use the subset, with its more specific source/destination
pair.</p>
<p>Here's an example. Suppose you are the system administrator at 192.0.2.2.
You have this connection in ipsec.conf:
<VAR>ipsec.conf</VAR>:
<PRE>conn net-to-net
left=192.0.2.2 # you are here
right=192.0.2.8
rightsubnet=192.0.2.96/27
....
</PRE>
<p>If you then place a host or net within <VAR>rightsubnet</VAR>,
(let's say 192.0.2.98) in <VAR>private-or-clear</VAR>, you may find
that 192.0.2.2 at times communicates in the
clear with 192.0.2.98. That's consistent with the rule, but may be
contrary to your expectations.</p>
<p>On the other hand, it's safe to put a larger subnet in a less
restrictive policy group file. If <VAR>private-or-clear</VAR>
contains 192.0.2.0/24, then the more specific <VAR>net-to-net</VAR>
connection is used for any communication to 192.0.2.96/27. The
more general policy applies only to communication with hosts or subnets in
192.0.2.0/24 without a more specific policy or connection.</p>
<h3><a name="policy.off">Can I turn off policy groups?</a></h3>
<p>Yes. Use <A HREF="policygroups.html#disable_policygroups">these
instructions</A>.</p>
<!--
<h3><a name="policy.otherinterface">Can I use policy groups
on an interface other than <VAR>%defaultroute</VAR>?</a></h3>
<p>??<p>
-->
<h3><a name="reload">Can I reload connection info without restarting?</a></h3>
<p>Yes, you can do this. Here are the details, in a mailing list message from
Pluto programmer Hugh Redelmeier:</p>
<pre>| How can I reload config's without restarting all of pluto and klips? I am using
| FreeSWAN -> PGPNet in a medium sized production environment, and would like to be
| able to add new connections ( i am using include config/* ) without dropping current
| SA's.
|
| Can this be done?
|
| If not, are there plans to add this kind of feature?
ipsec auto --add whatever
This will look in the usual place (/etc/ipsec.conf) for a conn named
whatever and add it.
If you added new secrets, you need to do
ipsec auto --rereadsecrets
before Pluto needs to know those secrets.
| I have looked (perhaps not thoroughly enough tho) to see how to do this:
There may be more bits to look for, depending on what you are trying
to do.</pre>
<p>Another useful command here is <var>ipsec auto --replace
<conn_name></var> which re-reads data for a named connection.</p>
<h3><a name="masq.faq">Can I use several masqueraded subnets?</a></h3>
<p>Yes. This is done all the time. See the discussion in our <a
href="config.html#route_or_not">setup</a> document. The only restriction is
that the subnets on the two ends must not overlap. See the next question.</p>
<p>Here is a mailing list message on the topic. The user incorrectly thinks
you need a 2.4 kernel for this -- actually various people have been doing it
on 2.0 and 2.2 for quite some time -- but he has it right for 2.4.</p>
<pre>Subject: Double NAT and freeswan working :)
Date: Sun, 11 Mar 2001
From: Paul Wouters <paul@xtdnet.nl>
Just to share my pleasure, and make an entry for people who are searching
the net on how to do this. Here's the very simple solution to have a double
NAT'ed network working with freeswan. (Not sure if this is old news, but I'm
not on the list (too much spam) and I didn't read this in any HOWTO/FAQ/doc
on the freeswan site yet (Sandy, put it in! :)
10.0.0.0/24 --- 10.0.0.1 a.b.c.d ---- a.b.c.e {internet} ----+
|
10.0.1.0/24 --- 10.0.1.1 f.g.h.i ---- f.g.h.j {internet} ----+
the goal is to have the first network do a VPN to the second one, yet also
have NAT in place for connections not destinated for the other side of the
NAT. Here the two Linux security gateways have one real IP number (cable
modem, dialup, whatever.
The problem with NAT is you don't want packets from 10.*.*.* to 10.*.*.*
to be NAT'ed. While with Linux 2.2, you can't, with Linux 2.4 you can.
(This has been tested and works for 2.4.2 with Freeswan snapshot2001mar8b)
relevant parts of /etc/ipsec.conf:
left=f.g.h.i
leftsubnet=10.0.1.0/24
leftnexthop=f.g.h.j
leftfirewall=yes
leftid=@firewall.netone.nl
leftrsasigkey=0x0........
right=a.b.c.d
rightsubnet=10.0.0.0/24
rightnexthop=a.b.c.e
rightfirewall=yes
rightid=@firewall.nettwo.nl
rightrsasigkey=0x0......
# To authorize this connection, but not actually start it, at startup,
# uncomment this.
auto=add
and now the real trick. Setup the NAT correctly on both sites:
iptables -t nat -F
iptables -t nat -A POSTROUTING -o eth0 -d \! 10.0.0.0/8 -j MASQUERADE
This tells the NAT code to only do NAT for packets with destination other then
10.* networks. note the backslash to mask the exclamation mark to protect it
against the shell.
Happy painting :)
Paul</pre>
<h3><a name="dup_route">Can I use subnets masqueraded to the same
addresses?</a></h3>
<p><strong>No.</strong> The notion that IP addresses are unique is one of the
fundamental principles of the IP protocol. Messing with it is exceedingly
perilous.</p>
<p>Fairly often a situation comes up where a company has several branches,
all using the same <a href="glossary.html#non-routable">non-routable
addresses</a>, perhaps 192.168.0.0/24. This works fine as long as those nets
are kept distinct. The <a href="glossary.html#masq">IP masquerading</a> on
their firewalls ensures that packets reaching the Internet carry the firewall
address, not the private address.</p>
<p>This can break down when IPsec enters the picture. FreeS/WAN builds a
tunnel that pokes through both masquerades and delivers packets from
<var>leftsubnet</var> to <var>rightsubnet</var> and vice versa. For this to
work, the two subnets <em>must</em> be distinct.</p>
<p>There are several solutions to this problem.</p>
<p>Usually, you <strong>re-number the subnets</strong>. Perhaps the Vancouver
office becomes 192.168.101.0/24, Calgary 192.168.102.0/24 and so on.
FreeS/WAN can happily handle this. With, for example
<var>leftsubnet=192.168.101.0/24</var> and
<var>rightsubnet=192.168.102.0/24</var> in a connection description, any
machine in Calgary can talk to any machine in Vancouver. If you want to be
more restrictive and use something like
<var>leftsubnet=192.168.101.128/25</var> and
<var>rightsubnet=192.168.102.240/28</var> so only certain machines on each
end have access to the tunnel, that's fine too.</p>
<p>You could also <strong>split the subnet</strong> into smaller ones, for
example using <var>192.168.1.0/25</var> in Vancouver and
<var>rightsubnet=192.168.0.128/25</var> in Calgary.</p>
<p>Alternately, you can just <strong>give up routing</strong> directly to
machines on the subnets. Omit the <var>leftsubnet</var> and
<var>rightsubnet</var> parameters from your connection descriptions. Your
IPsec tunnels will then run between the public interfaces of the two
firewalls. Packets will be masqueraded both before they are put into tunnels
and after they emerge. Your Vancouver client machines will see only one
Calgary machine, the firewall.</p>
<h3><a name="road.masq">Can I assign a road warrior an address on my net (a
virtual identity)?</a></h3>
<p>Often it would be convenient to be able to give a Road Warrior an IP
address which appears to be on the local network. Some IPsec implementations
have support for this, sometimes calling the feature "virtual identity".</p>
<p>Currently (Sept 2002) FreeS/WAN does not support this, and we have
no definite plans to add it. The difficulty is that is not yet a standard
mechanism for it. There is an Internet Draft for a method of doing it using
<a href="#DHCP">DHCP</a> which looks promising. FreeS/WAN may support that in
a future release.</p>
<p>In the meanwhile, you can do it yourself using the Linux iproute2(8)
facilities. Details are in <a
href="http://www.av8n.com/vpn/iproute2.htm">this
paper</a>.</p>
<p>Another method has also been discussed on the mailing list.:</p>
<ul>
<li>You can use a variant of the <a
href="adv_config.html#extruded.config">extruded subnet</a> procedure.</li>
<li>You have to avoid having the road warrior's assigned address within the
range you actually use at home base. See previous question.</li>
<li>On the other hand, you want the roadwarrior's address to be within the
range that <em>seems</em> to be on your network.</li>
</ul>
<p>For example, you might have:</p>
<dl>
<dt>leftsubnet=a.b.c.0/25</dt>
<dd>head office network</dd>
<dt>rightsubnet=a.b.c.129/32</dt>
<dd>extruded to a road warrior. Note that this is not in a.b.c.0/25</dd>
<dt>a.b.c.0/24</dt>
<dd>whole network, including both the above</dd>
</dl>
<p>You then set up routing so that the office machines use the IPsec gateway
as their route to a.b.c.128/25. The leftsubnet parameter tells the road
warriors to use tunnels to reach a.b.c.0/25, so you should have two-way
communication. Depending or your network and applications, there may be some
additional work to do on DNS or Windows configuration</p>
<h3><a name="road.many">Can I support many road warriors with one
gateway?</a></h3>
<p>Yes. This is easily done, using</p>
<dl>
<dt>either RSA authentication</dt>
<dd>standard in the FreeS/WAN distribution</dd>
<dt>or X.509 certificates</dt>
<dd>requires <a href="#PKIcert">Super FreeS/WAN or a patch</a>.</dd>
</dl>
<p>In either case, each Road Warrior must have a different key or
certificate.</p>
<p>It is also possible using pre-shared key authentication,
though we don't recommend this; see the
<a href="#road.PSK">next question</a> for details.</p>
<p>If you expect to have more than a few dozen Road Warriors connecting
simultaneously, you may need a fairly powerful gateway machine. See our
document on <a href="performance.html">FreeS/WAN performance</a>.</p>
<h3><a name="road.PSK">Can I have many road warriors using shared secret
authentication?</a></h3>
<p><STRONG>Yes, but avoid it if possible</STRONG>.</p>
<p>You can have multiple Road Warriors using shared secret authentication
<strong>only if they all use the same secret</strong>. You must also
set:<p>
<PRE> uniqueids=no </PRE>
<p>in the connection definition.</p>
<p>Why it's less secure:</p>
<ul>
<li>If you have many users, it becomes almost certain the secret will
leak</li>
<li>The secret becomes quite valuable to an attacker</li>
<li>All users authenticate the same way, so the gateway cannot tell them
apart for logging or access control purposes</li>
<li>Changing the secret is difficult. You have to securely notify all
users.</li>
<li>If you find out the secret has been compromised, you can change it, but
then what? None of your users can connect without the new secret. How
will you notify them all, quickly and securely, without using the
VPN?</li>
</ul>
<p>This is a designed-in limitation of the <a
href="glossary.html#IKE">IKE</a> key negotiation protocol, not a problem with
our implementation.</p>
<p><strong>We very strongly recommend that you avoid using shared secret
authentication for multiple Road Warriors.</strong> Use RSA authentication
instead.</p>
<p>The longer story: When using shared secrets, the protocol requires
that the responding
gateway be able to determine which secret to use at a time when all it knows
about the initiator is an IP address. This works fine if you know the
initiator's address in advance and can use it to look up the appropiriate
secret. However, it fails for Road Warriors since the gateway cannot know
their IP addresses in advance.</p>
<p>With RSA signatures (or certificates) the protocol is slightly different.
The initiator provides an identifier early in the exchange and the responder
can use that identifier to look up the correct key or certificate. See <a
href="#road.many">above</a>.</p>
<h3><a name="QoS">Can I use Quality of Service routing with
FreeS/WAN?</a></h3>
<p>From project technical lead Henry Spencer:</p>
<pre>> Do QoS add to FreeS/WAN?
> For example integrating DiffServ and FreeS/WAN?
With a current version of FreeS/WAN, you will have to add hidetos=no to
the config-setup section of your configuration file. By default, the TOS
field of tunnel packets is zeroed; with hidetos=no, it is copied from the
packet inside. (This is a modest security hole, which is why it is no
longer the default.)
DiffServ does not interact well with tunneling in general. Ways of
improving this are being studied.</pre>
<p>Copying the <a href="glossary.html#TOS">TOS</a> (type of service)
information from the encapsulated packet to the outer header reveals the TOS
information to an eavesdropper. This does not tell him much, but it might be
of use in <a href="glossary.html#traffic">traffic analysis</a>. Since we do
not have to give it to him, our default is not to.</p>
<P>Even with the TOS hidden, you can still:</P>
<UL>
<LI>apply QOS rules to the tunneled (ESP) packets; for example, by
giving ESP packets a certain priority.</LI>
<LI>apply QOS rules to the packets as they enter or exit the tunnel
via an IPsec virtual interface (eg. <VAR>ipsec0</VAR>).</LI>
</UL>
<p>See <a href="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</a> for more on
the <var>hidetos=</var> parameter.</p>
<h3><a name="deadtunnel">Can I recognise dead tunnels and shut them
down?</a></h3>
<p>There is no general mechanism to do this is in the IPsec protocols.</p>
<p>From time to time, there is discussion on the IETF Working Group <a
href="mail.html#ietf">mailing list</a> of adding a "keep-alive" mechanism
(which some say should be called "make-dead"), but it is a fairly complex
problem and no consensus has been reached on whether or how it should be
done.</p>
<p>The protocol does have optional <a href="#ignore">delete-SA</a> messages
which one side can send when it closes a connection in hopes this will cause
the other side to do the same. FreeS/WAN does not currently support these. In
any case, they would not solve the problem since:</p>
<ul>
<li>a gateway that crashes or hangs would not send the messages</li>
<li>the sender is not required to send them</li>
<li>they are not authenticated, so any receiver that trusts them leaves
itself open to a <a href="glossary.html#DOS">denial of service</a>
attack</li>
<li>the receiver is not required to do anything about them</li>
<li>the receiver cannot acknowledge them; the protocol provides no
mechanism for that</li>
<li>since they are not acknowledged, the sender cannot rely on them</li>
</ul>
<p>However, connections do have limited lifetimes and you can control how
many attempts your gateway makes to rekey before giving up. For example, you
can set:</p>
<pre>conn default
keyingtries=3
keylife=30m</pre>
<p>With these settings old connections will be cleaned up. Within 30 minutes
of the other end dying, rekeying will be attempted. If it succeeds, the new
connection replaces the old one. If it fails, no new connection is created.
Either way, the old connection is taken down when its lifetime expires.</p>
<p>Here is a mailing list message on the topic from FreeS/WAN tech support
person Claudia Schmeing:</p>
<pre>You ask how to determine whether a tunnel is redundant:
> Can anybody explain the best way to determine this. Esp when a RW has
> disconnected? I thought 'ipsec auto --status' might be one way.
If a tunnel goes down from one end, Linux FreeS/WAN on the
other end has no way of knowing this until it attempts to rekey.
Once it tries to rekey and fails, it will 'know' that the tunnel is
down.
Because it doesn't have a way of knowing the state until this point,
it will also not be able to tell you the state via ipsec auto --status.
> However, comparing output from a working tunnel with that of one that
> was closed
> did not show clearly show tunnel status.
If your tunnel is down but not 'unrouted' (see man ipsec_auto), you
should not be able to ping the opposite side of the tunnel. You can
use this as an indicator of tunnel status.
On a related note, you may be interested to know that as of 1.7,
redundant tunnels caused by RW disconnections are likely to be
less of a pain. From doc/CHANGES:
There is a new configuration parameter, uniqueids, to control a new Pluto
option: when a new connection is negotiated with the same ID as an old
one, the old one is deleted immediately. This should help eliminate
dangling Road Warrior connections when the same Road Warrior reconnects.
It thus requires that IDs not be shared by hosts (a previously legal but
probably useless capability). NOTE WELL: the sample ipsec.conf now has
uniqueids=yes in its config-setup section.
Cheers,
Claudia</pre>
<h3><a name="demanddial">Can I build IPsec tunnels over a demand-dialed
link?</a></h3>
<p>This is possible, but not easy. FreeS/WAN technical lead Henry Spencer
wrote:</p>
<pre>> 5. If the ISDN link goes down in between and is reestablished, the SAs
> are still up but the eroute are deleted and the IPsec interface shows
> garbage (with ifconfig)
> 6. Only restarting IPsec will bring the VPN back online.
This one is awkward to solve. If the real interface that the IPsec
interface is mounted on goes down, it takes most of the IPsec machinery
down with it, and a restart is the only good way to recover.
The only really clean fix, right now, is to split the machines in two:
1. A minimal machine serves as the network router, and only it is aware
that the link goes up and down.
2. The IPsec is done on a separate gateway machine, which thinks it has
a permanent network connection, via the router.
This is clumsy but it does work. Trying to do both functions within a
single machine is tricky. There is a software package (diald) which will
give the illusion of a permanent connection for demand-dialed modem
connections; I don't know whether it's usable for ISDN, or whether it can
be made to cooperate properly with FreeS/WAN.
Doing a restart each time the interface comes up *does* work, although it
is a bit painful. I did that with PPP when I was running on a modem link;
it wasn't hard to arrange the PPP scripts to bring IPsec up and down at
the right times. (I'd meant to investigate diald but never found time.)
In principle you don't need to do a complete restart on reconnect, but you
do have to rebuild some things, and we have no nice clean way of doing
only the necessary parts.</pre>
<p>In the same thread, one user commented:</p>
<pre>Subject: Re: linux-ipsec: IPsec and Dial Up Connections
Date: Wed, 22 Nov 2000
From: Andy Bradford <andyb@calderasystems.com>
On Wed, 22 Nov 2000 19:47:11 +0100, Philip Reetz wrote:
> Are there any ideas what might be the cause of the problem and any way
> to work around it.
> Any help is highly appreciated.
On my laptop, when using ppp there is a ip-up script in /etc/ppp that
will be executed each time that the ppp interface is brought up.
Likewise there is an ip-down script that is called when it is taken
down. You might consider custimzing those to stop and start FreeS/WAN
with each connection. I believe that ISDN uses the same files, though
I could be wrong---there should be something similar though.</pre>
<h3><a name="GRE">Can I build GRE, L2TP or PPTP tunnels over IPsec?</a></h3>
<p>Yes. Normally this is not necessary, but it is useful in a few special
cases. For example, if you must route non-IP packets such as IPX, you
will need to use a tunneling protocol that can route these packets. IPsec
can be layered around it for extra security. Another example: you
can provide failover protection for high availability (HA) environments by
combining IPsec with other tools. Ken Bantoft describes one such setup in
<A HREF="http://www.freeswan.ca/docs/HA">Using FreeS/WAN with Linux-HA, GRE,
OSPF and BGP for enterprise grade VPN solutions</A>.</P>
<p>GRE over IPsec is covered as part of
<A HREF="http://www.freeswan.ca/docs/HA">that document</A>.
<a href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/07/msg00209.html">
Here are links</a> to other GRE resources.
Jacco de Leuw has created
<A HREF="http://www.jacco2.dds.nl/networking/">this page on L2TP over IPsec</A>
with instructions for FreeS/WAN and several other brands of IPsec software.
</P>
<P>Please let us know of other useful links via the
<A HREF="mail.html">mailing lists</A>.
<h3><a name="NetBIOS">... use Network Neighborhood (Samba, NetBIOS) over IPsec?</a></h3>
<p>Your local PC needs to know how to translate NetBIOS names to IP addresses.
It may do this either via a local LMHOSTS file, or using a local or remote
WINS server. The WINS server is preferable since it provides a centralized
source of the information to the entire network. To use a WINS server over
the <A HREF="glossary.html#VPN">VPN</A>
(or any IP-based network), you must enable "NetBIOS over TCP".</p>
<p><A HREF="http://www.samba.org">Samba</A> can emulate a WINS server
on Linux.</p>
<p>
See also several discussions in our
<A HREF="http://lists.freeswan.org/pipermail/users/2002-September/thread.html">September
2002 Users archives</A></p>
<h2><a name="setup.faq">Life's little mysteries</a></h2>
<p>FreeS/WAN is a fairly complex product. (Neither the networks it runs on
nor the protocols it uses are simple, so it could hardly be otherwise.) It
therefore sometimes exhibits behaviour which can be somewhat confusing, or
has problems which are not easy to diagnose. This section tries to explain
those problems.</p>
<p>Setup and configuration of FreeS/WAN are covered in other documentation
sections:</p>
<ul>
<li><a href="quickstart.html">basic setup and configuration</a></li>
<li><a href="adv_config.html">advanced configuration</a></li>
<li><a href="trouble.html">Troubleshooting</a></li>
</ul>
<p>However, we also list some of the commonest problems here.</p>
<h3><a name="cantping">I cannot ping ....</a></h3>
<p>This question is dealt with in the advanced configuration section under
the heading <a href="adv_config.html#multitunnel">multiple tunnels</a>.</p>
<p>The standard subnet-to-subnet tunnel protects traffic <strong>only between
the subnets</strong>. To test it, you must use pings that go from one subnet
to the other.</p>
<p>For example, suppose you have:</p>
<pre> subnet a.b.c.0/24
|
eth1 = a.b.c.1
gate1
eth0 = 192.0.2.8
|
~ internet ~
|
eth0 = 192.0.2.11
gate2
eth1 = x.y.z.1
|
subnet x.y.z.0/24</pre>
<p>and the connection description:</p>
<pre>conn abc-xyz
left=192.0.2.8
leftsubnet=a.b.c.0/24
right=192.0.2.11
rightsubnet=x.y.z.0/24</pre>
<p>You can test this connection description only by sending a ping that will
actually go through the tunnel. Assuming you have machines at addresses
a.b.c.2 and x.y.z.2, pings you might consider trying are:</p>
<dl>
<dt>ping from x.y.z.2 to a.b.c.2 or vice versa</dt>
<dd>Succeeds if tunnel is working. This is the <strong>only valid test of
the tunnel</strong>.</dd>
<dt>ping from gate2 to a.b.c.2 or vice versa</dt>
<dd><strong>Does not use tunnel</strong>. gate2 is not on protected
subnet.</dd>
<dt>ping from gate1 to x.y.z.2 or vice versa</dt>
<dd><strong>Does not use tunnel</strong>. gate1 is not on protected
subnet.</dd>
<dt>ping from gate1 to gate2 or vice versa</dt>
<dd><strong>Does not use tunnel</strong>. Neither gate is on a protected
subnet.</dd>
</dl>
<p>Only the first of these is a useful test of this tunnel. The others do not
use the tunnel. Depending on other details of your setup and routing,
they:</p>
<ul>
<li>either fail, telling you nothing about the tunnel</li>
<li>or succeed, telling you nothing about the tunnel since these packets
use some other route</li>
</ul>
<p>In some cases, you may be able to get around this. For the example network
above, you could use:</p>
<pre> ping -I a.b.c.1 x.y.z.1</pre>
<p>Both the adresses given are within protected subnets, so this should go
through the tunnel.</p>
<p>If required, you can build additional tunnels so that all the machines
involved can talk to all the others. See <a
href="adv_config.html#multitunnel">multiple tunnels</a> in the advanced
configuration document for details.</p>
<h3><a name="forever">It takes forever to ...</a></h3>
<p>Users fairly often report various problems involving long delays,
sometimes on tunnel setup and sometimes on operations done through the
tunnel, occasionally on simple things like ping or more often on more complex
operations like doing NFS or Samba through the tunnel.</p>
<p>Almost always, these turn out to involve failure of a DNS lookup. The
timeouts waiting for DNS are typically set long so that you won't time out
when a query involves multiple lookups or long paths. Genuine failures
therefore produce long delays before they are detected.</p>
<p>A mailing list message from project technical lead Henry Spencer:</p>
<pre>> ... when i run /etc/rc.d/init.d/ipsec start, i get:
> ipsec_setup: Starting FreeS/WAN IPsec 1.5...
> and it just sits there, doesn't give back my bash prompt.
Almost certainly, the problem is that you're using DNS names in your
ipsec.conf, but DNS lookups are not working for some reason. You will
get your prompt back... eventually. But the DNS timeouts are long.
Doing something about this is on our list, but it is not easy.</pre>
<p>In the meanwhile, we recommend that connection descriptions in <a
href="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</a> use numeric IP addresses
rather than names which will require a DNS lookup.</p>
<p>Names that do not require a lookup are fine. For example:</p>
<ul>
<li>a road warrior might use the identity
<var>rightid=@lancelot.example.org</var></li>
<li>the gateway might use <var>leftid=@camelot.example.org</var></li>
</ul>
<p>These are fine. The @ sign prevents any DNS lookup. However, do not
attempt to give the gateway address as <var>left=camelot.example.org</var>.
That requires a lookup.</p>
<p>A post from one user after solving a problem with long delays:</p>
<pre>Subject: Final Answer to Delay!!!
Date: Mon, 19 Feb 2001
From: "Felippe Solutions" <felippe@solutionstecnologia.com.br>
Sorry people, but seems like the Delay problem had nothing to do with
freeswan.
The problem was DNS as some people sad from the beginning, but not the way
they thought it was happening. Samba, ssh, telnet and other apps try to
reverse lookup addresses when you use IP numbers (Stupid that ahh).
I could ping very fast because I always ping with "-n" option, but I don't
know the option on the other apps to stop reverse addressing so I don't use
it.</pre>
<p>This post is fairly typical. These problems are often tricky and
frustrating to diagnose, and most turn out to be DNS-related.</p>
<p>One suggestion for diagnosis: test with both names and addresses if
possible. For example, try all of:</p>
<ul>
<li>ping <var>address</var></li>
<li>ping -n <var>address</var></li>
<li>ping <var>name</var></li>
</ul>
<p>If these behave differently, the problem must be DNS-related since the
three commands do exactly the same thing except for DNS lookups.</p>
<h3><a name="route">I send packets to the tunnel with route(8) but they
vanish</a></h3>
<p>IPsec connections are designed to carry only packets travelling between
pre-defined connection endpoints. As project technical lead Henry Spencer put
it:</p>
<blockquote>
IPsec tunnels are not just virtual wires; they are virtual wires with
built-in access controls. Negotiation of an IPsec tunnel includes
negotiation of access rights for it, which don't include packets to/from
other IP addresses. (The protocols themselves are quite inflexible about
this, so there are limits to what we can do about it.)</blockquote>
<p>For fairly obvious security reasons, and to comply with the IPsec RFCs, <a
href="glossary.html#KLIPS">KLIPS</a> drops any packets it receives that are
not allowed on the tunnels currently defined. So if you send it packets with
<var>route(8)</var>, and suitable tunnels are not defined, the packets
vanish. Whether this is reported in the logs depends on the setting of
<var>klipsdebug</var> in your <a
href="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</a> file.</p>
<p>To rescue vanishing packets, you must ensure that suitable tunnels for
them exist, by editing the connection descriptions in <a
href="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</a>. For example, supposing
you have a simple setup:</p>
<pre> leftsubnet -- leftgateway === internet === roadwarrior</pre>
<p>If you want to give the roadwarrior access to some resource that is
located behind the left gateway but is not in the currently defined left
subnet, then the usual procedure is to define an additional tunnel for those
packets by creating a new connection description.</p>
<p>In some cases, it may be easier to alter an existing connection
description, enlarging the definition of <var>leftsubnet</var>. For example,
instead of two connection descriptions with 192.168.8.0/24 and 192.168.9.0/24
as their <var>leftsubnet</var> parameters, you can use a single description
with 192.168.8.0/23.</p>
<p>If you have multiple endpoints on each side, you need to ensure that there
is a route for each pair of endpoints. See this <a
href="adv_config.html#multitunnel">example</a>.</p>
<h3><a name="down_route">When a tunnel goes down, packets vanish</a></h3>
<p>This is a special case of the vanishing packet problem described in the
previous question. Whenever KLIPS sees packets for which it does not have a
tunnel, it drops them.</p>
<p>When a tunnel goes away, either because negotiations with the other
gateway failed or because you gave an <var>ipsec auto --down</var> command,
the route to its other end is left pointing into KLIPS, and KLIPS will drop
packets it has no tunnel for.</p>
<p>This is a documented design decision, not a bug. FreeS/WAN must not
automatically adjust things to send packets via another route. The other
route might be insecure.</p>
<p>Of course, re-routing may be necessary in many cases. In those cases, you
have to do it manually or via scripts. We provide the <var>ipsec auto
--unroute</var> command for these cases.</p>
<p>From <a href="manpage.d/ipsec_auto.8.html">ipsec_auto(8)</a>:</p>
<blockquote>
Normally, pluto establishes a route to the destination specified for a
connection as part of the --up operation. However, the route and only
the route can be established with the --route operation. Until and unless
an actual connection is established, this discards any packets sent
there, which may be preferable to having them sent elsewhere based on a
more general route (e.g., a default route).</blockquote>
<blockquote>
Normally, pluto's route to a destination remains in place when a --down
operation is used to take the connection down (or if connection setup, or
later automatic rekeying, fails). This permits establishing a new
connection (perhaps using a different specification; the route is altered
as necessary) without having a ``window'' in which packets might go
elsewhere based on a more general route. Such a route can be removed
using the --unroute operation (and is implicitly removed by
--delete).</blockquote>
<p>See also this mailing list <a
href="http://www.sandelman.ottawa.on.ca/linux-ipsec/html/2000/11/msg00523.html">message</a>.</p>
<h3><a name="firewall_ate">The firewall ate my packets!</a></h3>
<p>If firewalls filter out:</p>
<ul>
<li>either the UDP port 500 packets used in IKE negotiations</li>
<li>or the ESP and AH (protocols 50 and 51) packets used to implement the
IPsec tunnel</li>
</ul>
<p>then IPsec cannot work. The first thing to check if packets seem to be
vanishing is the firewall rules on the two gateway machines and any other
machines along the path that you have access to.</p>
<p>For details, see our document on <a href="firewall.html">firewalls</a>.</p>
<p>Some advice from technical lead Henry Spencer on diagnosing such
problems:</p>
<pre>> > Packets vanishing between the hardware interface and the ipsecN interface
> > is usually the result of firewalls not being configured to let them in...
>
> Thanks for the suggestion. If only it were that simple! My ipchains startup
> script does take care of that, but just in case I manually inserted rules
> accepting everything from london on dublin. No difference.
The other thing to check is whether the "RX packets dropped" count on the
ipsecN interface (run "ifconfig ipsecN", for N=1 or whatever, to see the
counts) is rising. If so, then there's some sort of configuration mismatch
between the two ends, and IPsec itself is rejecting them. If none of the
ipsecN counts is rising, then the packets are never reaching the IPsec
machinery, and the problem is almost certainly in firewalls etc.</pre>
<h3><a name="dropconn">Dropped connections</a></h3>
<p>Networks being what they are, IPsec connections can be broken for any
number of reasons, ranging from hardware failures to various software
problems such as the path MTU problems discussed <a
href="#pmtu.broken">elsewhere in the FAQ</a>. Fortunately, various diagnostic
tools exist that help you sort out many of the possible problems.</p>
<p>There is one situation, however, where FreeS/WAN (using default settings)
may destroy a connection for no readily apparent reason. This occurs when
things are <strong>misconfigured</strong> so that <strong>two
tunnels</strong> from the same gateway expect <strong>the same subnet on the
far end</strong>.</p>
<p>In this situation, the first tunnel comes up fine and works until the
second is established. At that point, because of the way we track connections
internally, the first tunnel ceases to exist as far as this gateway is
concerned. Of course the far end does not know that, and a storm of error
messages appears on both systems as it tries to use the tunnel.</p>
<p>If the far end gives up, goes back to square one and negotiates a new
tunnel, then that wipes out the second tunnel and ...</p>
<p>The solution is simple. <strong>Do not build multiple conn descriptions
with the same remote subnet</strong>.</p>
<p>This is actually intended to be a feature, rather than a bug. Consider the
situation where a single remote system goes down, then comes back up and
reconnects to the gateway. It is useful to have the gateway tear down the old
tunnel and recover resources when the reconnection is made. It recognises
that situation by checking the remote subnet for each tunnel it builds and
discarding duplicates. This works fine as long as you don't configure
multiple tunnels with the same remote subnet.</p>
<p>If this behaviour is inconvenient for you, you can disable it by setting
<var>uniqueids=no</var> in <a
href="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</a>.</p>
<h3><a name="defaultroutegone">Disappearing %defaultroute</a></h3>
<p>When an underlying connection (eg. ppp) goes down, FreeS/WAN will not
recover properly without a little help. Here are the symptoms that FreeS/WAN
user Michael Carmody noticed:
<pre>
> After about 24 hours the freeswan connection takes over the default route.
>
> i.e instead of deafult gateway pointing to the router via eth0, it becomes a
> pointer to the router via ipsec0.
> All internet access is then lost as all replies (and not just the link I
> wanted) are routed out ipsec0 and the router doesn't respond to the ipsec
> traffic.
</pre>
<p>If you're using a
FreeS/WAN 2.x/KLIPS system, simply re-attach the IPsec virtual
interface with <em>ipsec tnconfig</em> command such as:</p>
<pre> ipsec tnconfig --attach --virtual ipsec0 --physical ppp0</pre>
<p>In your command, name the physical and virtual interfaces as they
appear paired on your system during regular uptime. For a system with several
physical/virtual interface pairs on flaky links, you'll need more than
one such command.
If you're using FreeS/WAN 1.x, you must restart FreeS/WAN, which is more time
consuming.</p>
<p>
<A href="http://lists.freeswan.org/pipermail/design/2002-July/003070.html">Here</A>
is a script which can help to automate the process of FreeS/WAN restart at
need.
It could easily be adapted to use tnconfig instead.</p>
<h3><a name="tcpdump.faq">TCPdump on the gateway shows strange things</a></h3>
As another user pointed out, keeping the connect
<p>Attempting to look at IPsec packets by running monitoring tools on the
IPsec gateway machine can produce silly results. That machine is mangling the
packets for IPsec, and possibly for firewall or NAT purposes as well. If the
internals of the machine's IP stack are not what the monitoring tool expects,
then the tool can misinterpret them and produce nonsense output.</p>
<p>See our <a href="testing.html#tcpdump.test">testing</a> document for more
detail.</p>
<h3><a name="no_trace">Traceroute does not show anything between the
gateways</a></h3>
<p>As far as traceroute can see, the two gateways are one hop apart; the data
packet goes directly from one to the other through the tunnel. Of course the
outer packets that implement the tunnel pass through whatever lies between
the gateways, but those packets are built and dismantled by the gateways.
Traceroute does not see them and cannot report anything about their path.</p>
<p>Here is a mailing list message with more detail.</p>
<pre>Date: Mon, 14 May 2001
To: linux-ipsec@freeswan.org
From: "John S. Denker" <jsd@research.att.com<
Subject: Re: traceroute: one virtual hop
At 02:20 PM 5/14/01 -0400, Claudia Schmeing wrote:
>
>> > A bonus question: traceroute in subnet to subnet enviroment looks like:
>> >
>> > traceroute to andris.dmz (172.20.24.10), 30 hops max, 38 byte packets
>> > 1 drama (172.20.1.1) 0.716 ms 0.942 ms 0.434 ms
>> > 2 * * *
>> > 3 andris.dmz (172.20.24.10) 73.576 ms 78.858 ms 79.434 ms
>> >
>> > Why aren't there the other hosts which take part in the delivery during
> * * * ?
>
>If there is an ipsec tunnel between GateA and Gate B, this tunnel forms a
>'virtual wire'. When it is tunneled, the original packet becomes an inner
>packet, and new ESP and/or AH headers are added to create an outer packet
>around it. You can see an example of how this is done for AH at
>doc/ipsec.html#AH . For ESP it is similar.
>
>Think about the packet's path from the inner packet's perspective.
>It leaves the subnet, goes into the tunnel, and re-emerges in the second
>subnet. This perspective is also the only one available to the
>'traceroute' command when the IPSec tunnel is up.
Claudia got this exactly right. Let me just expand on a couple of points:
*) GateB is exactly one (virtual) hop away from GateA. This is how it
would be if there were a physically private wire from A to B. The
virtually private connection should work the same, and it does.
*) While the information is in transit from GateA to GateB, the hop count
of the outer header (the "envelope") is being decremented. The hop count
of the inner header (the "contents" of the envelope) is not decremented and
should not be decremented. The hop count of the outer header is not
derived from and should not be derived from the hop count of the inner header.
Indeed, even if the packets did time out in transit along the tunnel, there
would be no way for traceroute to find out what happened. Just as
information cannot leak _out_ of the tunnel to the outside, information
cannot leak _into_ the tunnel from outside, and this includes ICMP messages
from routers along the path.
There are some cases where one might wish for information about what is
happening at the IP layer (below the tunnel layer) -- but the protocol
makes no provision for this. This raises all sorts of conceptual issues.
AFAIK nobody has ever cared enough to really figure out what _should_
happen, let alone implement it and standardize it.
*) I consider the "* * *" to be a slight bug. One might wish for it to be
replaced by "GateB GateB GateB". It has to do with treating host-to-subnet
traffic different from subnet-to-subnet traffic (and other gory details).
I fervently hope KLIPS2 will make this problem go away.
*) If you want to ask questions about the link from GateA to GateB at the
IP level (below the tunnel level), you have to ssh to GateA and launch a
traceroute from there.</pre>
<h2><a name="man4debug">Testing in stages</a></h2>
<p>It is often useful in debugging to test things one at a time:</p>
<ul>
<li>disable IPsec entirely, for example by turning it off with
chkconfig(8), and make sure routing works</li>
<li>Once that works, try a manually keyed connection. This does not require
key negotiation between Pluto and the key daemon on the other end.</li>
<li>Once that works, try automatically keyed connections</li>
<li>Once IPsec works, add packet compression</li>
<li>Once everything seems to work, try stress tests with large transfers,
many connections, frequent re-keying, ...</li>
</ul>
<p>FreeS/WAN releases are tested for all of these, so you can be reasonably
certain they <em>can</em> do them all. Of course, that does not mean they
<em>will</em> on the first try, especially if you have some unusual
configuration.</p>
<p>The rest of this section gives information on diagnosing the problem when
each of the above steps fails.</p>
<h3><a name="nomanual">Manually keyed connections don't work</a></h3>
<p>Suspect one of:</p>
<ul>
<li>mis-configuration of IPsec system in the /etc/ipsec.conf file<br>
common errors are incorrect interface or next hop information</li>
<li>mis-configuration of manual connection in the /etc/ipsec.conf file</li>
<li>routing problems causing IPsec packets to be lost</li>
<li>bugs in KLIPS</li>
<li>mismatch between the transforms we support and those another IPsec
implementation offers.</li>
</ul>
<h3><a name="spi_error">One manual connection works, but second one
fails</a></h3>
<p>This is a fairly common problem when attempting to configure multiple
manually keyed connections from a single gateway.</p>
<p>Each connection must be identified by a unique <a
href="glossary.html#SPI">SPI</a> value. For automatic connections, these
values are assigned automatically. For manual connections, you must set them
with <var>spi=</var> statements in <a
href="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</a>.</p>
<p>Each manual connection must have a unique SPI value in the range 0x100 to
0x999. Two or more with the same value will fail. For details, see our doc
section <a href="adv_config.html#prodman">Using manual keying in
production</a> and the man page <a
href="manpage.d/ipsec.conf.5.html">ipsec.conf(5)</a>.</p>
<h3><a name="man_no_auto">Manual connections work, but automatic keying
doesn't</a></h3>
<p>The most common reason for this behaviour is a firewall dropping the UDP
port 500 packets used in key negotiation.</p>
<p>Other possibilities:</p>
<ul>
<li>mis-configuration of auto connection in the /etc/ipsec.conf file.
<p>One common configuration error is forgetting that you need
<var>auto=add</var> to load the connection description on the receiving
end so it recognises the connection when the other end asks for it.</p>
</li>
<li>error in shared secret in /etc/ipsec.secrets</li>
<li>one gateway lacks a route to the other so Pluto's UDP packets are
lost</li>
<li>bugs in Pluto</li>
<li>incompatibilities between Pluto's <a href="glossary.html#IKE">IKE</a>
implementation and the IKE at the other end of the tunnel.
<p>Some possibile problems are discussed in out <a
href="interop.html#interop.problem">interoperation</a> document.</p>
</li>
</ul>
<h3><a name="nocomp">IPsec works, but connections using compression
fail</a></h3>
<p>When we first added compression, we saw some problems:</p>
<ul>
<li>compatibility issues with other implementations. We followed the RFCs
and omitted some extra material that many compression libraries add by
default. Some other implementations left the extras in</li>
<li>bugs in assembler compression routines on non-Intel CPUs. The
workaround is to use C code instead of possibly problematic
assembler.</li>
</ul>
<p>We have not seen either problem in some time (at least six months as I
write in March 2002), but if you have some unusual configuration then you may
see them.</p>
<h3><a name="pmtu.broken">Small packets work, but large transfers
fail</a></h3>
<p>If tests with ping(1) and a small packet size succeed, but tests or
transfers with larger packet sizes fail, suspect problems with packet
fragmentation and perhaps <a href="glossary.html#pathMTU">path MTU
discovery</a>.</p>
<p>Our <a href="trouble.html#bigpacket">troubleshooting document</a> covers
these problems. Information on the underlying mechanism is in our <a
href="background.html#MTU.trouble">background</a> document.</p>
<h3><a name="subsub">Subnet-to-subnet works, but tests from the gateways
don't</a></h3>
<p>This is described under <a href="#cantping">I cannot ping...</a> above.</p>
<h2><a name="compile.faq">Compilation problems</a></h2>
<h3><a name="gmp.h_missing">gmp.h: No such file or directory</a></h3>
<p>Pluto needs the GMP (<strong>G</strong>NU</p>
<p><strong>M</strong>ulti-<strong>P</strong>recision) library for the large
integer calculations it uses in <a href="glossary.html#public">public key</a>
cryptography. This error message indicates a failure to find the library. You
must install it before Pluto will compile.</p>
<p>The GMP library is included in most Linux distributions. Typically, there
are two RPMs, libgmp and libgmp-devel, You need to <em>install both</em>,
either from your distribution CDs or from your vendor's web site.</p>
<p>On Debian, a mailing list message reports that the command to give is
<var>apt-get install gmp2</var>.</p>
<p>For more information and the latest version, see the <a
href="http://www.swox.com/gmp/">GMP home page</a>.</p>
<h3><a name="noVM">... virtual memory exhausted</a></h3>
<p>We have had several reports of this message appearing, all on SPARC Linux.
Here is a mailing message on a solution:</p>
<pre>> ipsec_sha1.c: In function `SHA1Transform':
> ipsec_sha1.c:95: virtual memory exhausted
I'm seeing exactly the same problem on an Ultra with 256MB ram and 500
MB swap. Except I am compiling version 1.5 and its Red Hat 6.2.
I can get around this by using -O instead of -O2 for the optimization
level. So it is probably a bug in the optimizer on the sparc complier.
I'll try and chase this down on the sparc lists.</pre>
<h2><a name="error">Interpreting error messages</a></h2>
<h3><a name="route-client">route-client (or host) exited with status
7</a></h3>
<p>Here is a discussion of this error from FreeS/WAN "listress" (mailing list
tech support person) Claudia Schmeing. The "FAQ on the network unreachable
error" which she refers to is the next question below.</p>
<pre>> I reached the point where the two boxes (both on dial-up connections, but
> treated as static IPs by getting the IP and editing ipsec.conf after the
> connection is established) to the point where they exchange some info, but I
> get an error like "route-client command exited with status 7 \n internal
> error".
> Where can I find a description of this error?
In general, if the FAQ doesn't cover it, you can search the mailing list
archives - I like to use
http://www.sandelman.ottawa.on.ca/linux-ipsec/
but you can see doc/mail.html for different archive formats.
Your error comes from the _updown script, which performs some
routing and firewall functions to help Linux FreeS/WAN. More info
is available at doc/firewall.html and man ipsec.conf. Its routing
is integral to the health of Linux FreeS/WAN; it also provides facility
to insert custom firewall rules to be executed when you create or destroy
a connection.
Yours is, of course, a routing error. You can be fairly sure the routing
machinery is saying "network is unreachable". There's a FAQ on the
"network is unreachable" error, but more information is available now; read on.
If your _updown script is recent (for example if it shipped with
Linux FreeS/WAN 1.91), you will see another debugging line in your logs
that looks something like this:
> output: /usr/local/lib/ipsec/_updown: `route add -net 128.174.253.83
> netmask 255.255.255.255 dev ipsec0 gw 66.92.93.161' failed
This is, of course, the system route command that exited with status 7,
(ie. failed). Man route for details. Seeing the command typed out yields
more information. If your _updown script is older, you may wish to update
it to show the command explicitly.
Three parameters fed to the route command: net, netmask and gw [gateway]
are derived from things you've put in ipsec.conf.
Net and netmask are derived from the peer's IP and mask. In more detail:
You may see a routing error when routing to a client (ie. subnet), or
to a host (IPSec gateway or freestanding host; a box that does IPSec for
itself). In _updown, the "route-client" section is responsible to set up
the route for IPSec'd (usually, read 'tunneled') packets headed to a
peer subnet. Similarly, route-host routes IPSec'd packets to a peer host
or IPSec gateway.
When routing to a 'client', net and netmask are ipsec.conf's left- or
rightsubnet (whichever is not local). Similarly, when routing to a
'host' the net is left or right. Host netmask is always /32, indicating a
single machine.
Gw is nexthop's value. Again, the value in question is left- or rightnexthop,
whichever is local. Where left/right or left-/rightnexthop has the special
value %defaultroute (described in man ipsec.conf), gw will automagically get
the value of the next hop on the default route.
Q: "What's a nexthop and why do I need one?"
A: 'nexthop' is a routing kluge; its value is the next hop away
from the machine that's doing IPSec, and toward your IPSec peer.
You need it to get the processed packets out of the local system and
onto the wire. While we often route other packets through the machine
that's now doing IPSec, and are done with it, this does not suffice here.
After packets are processed with IPSec, this machine needs to know where
they go next. Of course using the 'IPSec gateway' as their routing gateway
would cause an infinite loop! [To visualize this, see the packet flow
diagram at doc/firewall.html.] To avoid this, we route packets through
the next hop down their projected path.
Now that you know the background, consider:
1. Did you test routing between the gateways in the absence of Linux
FreeS/WAN, as recommended? You need to ensure the two machines that
will be running Linux FreeS/WAN can route to one another before trying to
make a secure connection.
2. Is there anything obviously wrong with the sense of your route command?
Normally, this problem is caused by an incorrect local nexthop parameter.
Check out the use of %defaultroute, described in man ipsec.conf. This is
a simple way to set nexthop for most people. To figure nexthop out by hand,
traceroute in-the-clear to your IPSec peer. Nexthop is the traceroute's
first hop after your IPSec gateway.</pre>
<h3><a name="unreachable">SIOCADDRT:Network is unreachable</a></h3>
<p>This message is not from FreeS/WAN, but from the Linux IP stack itself.
That stack is seeing packets it has no route for, either because your routing
was broken before FreeS/WAN started or because FreeS/WAN's changes broke
it.</p>
<p>Here is a message from Claudia suggesting ways to diagnose and fix such
problems:</p>
<pre>You write,
> I have correctly installed freeswan-1.8 on RH7.0 kernel 2.2.17, but when
> I setup a VPN connection with the other machine(RH5.2 Kernel 2.0.36
> freeswan-1.0, it works well.) it told me that
> "SIOCADDRT:Network is unreachable"! But the network connection is no
> problem.
Often this error is the result of a misconfiguration.
Be sure that you can route successfully in the absence of Linux
FreeS/WAN. (You say this is no problem, so proceed to the next step.)
Use a custom copy of the default updownscript. Do not change the route
commands, but add a diagnostic message revealing the exact text of the
route command. Is there a problem with the sense of the route command
that you can see? If so, then re-examine those ipsec.conf settings
that are being sent to the route command.
You may wish to use the ipsec auto --route and --unroute commands to
troubleshoot the problem. See man ipsec_auto for details.</pre>
<p>Since the above message was written, we have modified the updown script to
provide a better diagnostic for this problem. Check
<var>/var/log/messages</var>.</p>
<p>See also the FAQ question <a href="#route-client">route-client (or host)
exited with status 7</a>.</p>
<h3><a name="modprobe">ipsec_setup: modprobe: Can't locate module
ipsec</a></h3>
<h3><a name="noKLIPS">ipsec_setup: Fatal error, kernel appears to lack
KLIPS</a></h3>
<p>These messages indicate an installation failure. The kernel you are
running does not contain the <a href="glossary.html#KLIPS">KLIPS (kernel
IPsec)</a> code.</p>
<p>Note that the "modprobe: Can't locate module ipsec" message appears even
if you are not using modules. If there is no KLIPS in your kernel, FreeS/WAN
tries to load it as a module. If that fails, you get this message.</p>
<p>Commands you can quickly try are:</p>
<dl>
<dt><var>uname -a</var></dt>
<dd>to get details, including compilation date and time, of the currently
running kernel</dd>
<dt><var>ls /</var></dt>
<dt><var>ls /boot</var></dt>
<dd>to ensure a new kernel is where it should be. If kernel compilation
puts it in <var>/</var> but <var>lilo</var> wants it in
<var>/boot</var>, then you should uncomment the
<var>INSTALL_PATH=/boot</var> line in the kernel
<var>Makefile</var>.</dd>
<dt><var>more /etc/lilo.conf</var></dt>
<dd>to see that <var>lilo</var> has correct information</dd>
<dt><var>lilo</var></dt>
<dd>to ensure that information in <var>/etc/lilo.conf</var> has been
transferred to the boot sector</dd>
</dl>
<p>If those don't find the problem, you have to go back and check through the
<a href="install.html">install</a> procedure to see what was missed.</p>
<p>Here is one of Claudia's messages on the topic:</p>
<pre>> I tried to install freeswan 1.8 on my mandrake 7.2 test box. ...
> It does show version and some output for whack.
Yes, because the Pluto (daemon) part of ipsec is installed correctly, but
as we see below the kernel portion is not.
> However, I get the following from /var/log/messages:
>
> Mar 11 22:11:55 pavillion ipsec_setup: Starting FreeS/WAN IPsec 1.8...
> Mar 11 22:12:02 pavillion ipsec_setup: modprobe: Can't locate module ipsec
> Mar 11 22:12:02 pavillion ipsec_setup: Fatal error, kernel appears to lack
> KLIPS.
This is your problem. You have not successfully installed a kernel with
IPSec machinery in it.
Did you build Linux FreeS/WAN as a module? If so, you need to ensure that
your new module has been installed in the directory where your kernel
loader normally finds your modules. If not, you need to ensure
that the new IPSec-enabled kernel is being loaded correctly.
See also doc/install.html, and INSTALL in the distro.</pre>
<h3><a name="noDNS">ipsec_setup: ... failure to fetch key for ... from
DNS</a></h3>
<p>Quoting Henry:</p>
<pre>Note that by default, FreeS/WAN is now set up to
(a) authenticate with RSA keys, and
(b) fetch the public key of the far end from DNS.
Explicit attention to ipsec.conf will be needed if you want
to do something different.</pre>
<p>and Claudia, responding to the same user:</p>
<pre>You write,
> My current setup in ipsec.conf is leftrsasigkey=%dns I have
> commented this and authby=rsasig out. I am able to get ipsec running,
> but what I find is that the documentation only specifies for %dns are
> there any other values that can be placed in this variable other than
> %dns and the key? I am also assuming that this is where I would place
> my public key for the left and right side as well is this correct?
Valid values for authby= are rsasig and secret, which entail authentication
by RSA signature or by shared secret, respectively. Because you have
commented authby=rsasig out, you are using the default value of authby=secret.
When using RSA signatures, there are two ways to get the public key for the
IPSec peer: either copy it directly into *rsasigkey= in ipsec.conf, or
fetch it from dns. The magic value %dns for *rsasigkey parameters says to
try to fetch the peer's key from dns.
For any parameters, you may find their significance and special values in
man ipsec.conf. If you are setting up keys or secrets, be sure also to
reference man ipsec.secrets.</pre>
<h3><a name="dup_address">ipsec_setup: ... interfaces ... and ... share
address ...</a></h3>
<p>This is a fatal error. FreeS/WAN cannot cope with two or more interfaces
using the same IP address. You must re-configure to avoid this.</p>
<p>A mailing list message on the topic from Pluto developer Hugh
Redelmeier:</p>
<pre>| I'm trying to get freeswan working between two machine where one has a ppp
| interface.
| I've already suceeded with two machines with ethernet ports but the ppp
| interface is causing me problems.
| basically when I run ipsec start i get
| ipsec_setup: Starting FreeS/WAN IPsec 1.7...
| ipsec_setup: 003 IP interfaces ppp1 and ppp0 share address 192.168.0.10!
| ipsec_setup: 003 IP interfaces ppp1 and ppp2 share address 192.168.0.10!
| ipsec_setup: 003 IP interfaces ppp0 and ppp2 share address 192.168.0.10!
| ipsec_setup: 003 no public interfaces found
|
| followed by lots of cannot work out interface for connection messages
|
| now I can specify the interface in ipsec.conf to be ppp0 , but this does
| not affect the above behaviour. A quick look in server.c indicates that the
| interfaces value is not used but some sort of raw detect happens.
|
| I guess I could prevent the formation of the extra ppp interfaces or
| allocate them different ip but I'd rather not. if at all possible. Any
| suggestions please.
Pluto won't touch an interface that shares an IP address with another.
This will eventually change, but it probably won't happen soon.
For now, you will have to give the ppp1 and ppp2 different addresses.</pre>
<h3><a name="kflags">ipsec_setup: Cannot adjust kernel flags</a></h3>
<p>A mailing list message form technical lead Henry Spencer:</p>
<pre>> When FreeS/WAN IPsec 1.7 is starting on my 2.0.38 Linux kernel the following
> error message is generated:
> ipsec_setup: Cannot adjust kernel flags, no /proc/sys/net/ipsec directory!
> What is supposed to create this directory and how can I fix this problem?
I think that directory is a 2.2ism, although I'm not certain (I don't have
a 2.0.xx system handy any more for testing). Without it, some of the
ipsec.conf config-setup flags won't work, but otherwise things should
function. </pre>
<p>You also need to enable the <var>/proc</var> filesystem in your kernel
configuration for these operations to work.</p>
<h3><a name="message_num">Message numbers (MI3, QR1, et cetera) in Pluto
messages</a></h3>
<p>Pluto messages often indicate where Pluto is in the IKE protocols. The
letters indicate <strong>M</strong>ain mode or <strong>Q</strong>uick mode
and <strong>I</strong>nitiator or <strong>R</strong>esponder. The numerals
are message sequence numbers. For more detail, see our <a
href="ipsec.html#sequence">IPsec section</a>.</p>
<h3><a name="conn_name">Connection names in Pluto error messages</a></h3>
<p>From Pluto programmer Hugh Redelmeier:</p>
<pre>| Jan 17 16:21:10 remus Pluto[13631]: "jumble" #1: responding to Main Mode from Road Warrior 130.205.82.46
| Jan 17 16:21:11 remus Pluto[13631]: "jumble" #1: no suitable connection for peer @banshee.wittsend.com
|
| The connection "jumble" has nothing to do with the incoming
| connection requests, which were meant for the connection "banshee".
You are right. The message tells you which Connection Pluto is
currently using, which need not be the right one. It need not be the
right one now for the negotiation to eventually succeed! This is
described in ipsec_pluto(8) in the section "Road Warrior Support".
There are two times when Pluto will consider switching Connections for
a state object. Both are in response to receiving ID payloads (one in
Phase 1 / Main Mode and one in Phase 2 / Quick Mode). The second is
not unique to Road Warriors. In fact, neither is the first any more
(two connections for the same pair of hosts could differ in Phase 1 ID
payload; probably nobody else has tried this).</pre>
<h3><a name="cantorient">Pluto: ... can't orient connection</a></h3>
<p>Older versions of FreeS/WAN used this message. The same error now gives
the "we have no ipsecN ..." error described just below.</p>
<h3><a name="no.interface">... we have no ipsecN interface for either end of
this connection</a></h3>
<p>Your tunnel has no IP address which matches the IP
address of any of the available IPsec interfaces. Either you've
misconfigured the connection, or you need to define an appropriate
IPsec interface connection. <VAR>interfaces=%defaultroute</VAR> works
in many cases.</p>
<p>A longer story: Pluto needs to know whether it is running on
the machine which the
connection description calls <var>left</var> or on <var>right</var>. It
figures that out by:</p>
<ul>
<li>looking at the interfaces given in <var>interfaces=</var> lines in the
<var>config setup</var> section</li>
<li>discovering the IP addresses for those interfaces</li>
<li>searching for a match between those addresses and the ones given in
<var>left=</var> or <var>right=</var> lines.</li>
</ul>
<p>Normally a match is found. Then Pluto knows where it is and can set up
other things (for example, if it is <var>left</var>) using parameters such as
<var>leftsubnet</var> and <var>leftnexthop</var>, and sending its outgoing
packets to <var>right</var>.</p>
<p>If no match is found, it emits the above error message.</p>
<h3><a name="noconn">Pluto: ... no connection is known</a></h3>
<p>This error message occurs when a remote system attempts to negotiate a
connection and Pluto does not have a connection description that matches what
the remote system has requested. The most common cause is a configuration
error on one end or the other.</p>
<p>Parameters involved in this match are <var>left</var>, <var>right</var>,
<var>leftsubnet</var> and <var>rightsubnet</var>.</p>
<p><strong>The match must be exact</strong>. For example, if your left subnet
is a.b.c.0/24 then neither a single machine in that net nor a smaller subnet
such as a.b.c.64/26 will be considered a match.</p>
<p>The message can also occur when an appropriate description exists but
Pluto has not loaded it. Use an <var>auto=add</var> statement in the
connection description, or an <var>ipsec auto --add <conn_name></var>
command, to correct this.</p>
<p>An explanation from the Pluto developer:</p>
<pre>| Jul 12 15:00:22 sohar58 Pluto[574]: "corp_road" #2: cannot respond to IPsec
| SA request because no connection is known for
| 216.112.83.112/32===216.112.83.112...216.67.25.118
This is the first message from the Pluto log showing a problem. It
means that PGPnet is trying to negotiate a set of SAs with this
topology:
216.112.83.112/32===216.112.83.112...216.67.25.118
^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^ ^^^^^^^^^^^^^
client on our side our host PGPnet host, no client
None of the conns you showed look like this.
Use
ipsec auto --status
to see a snapshot of what connections are in pluto, what
negotiations are going on, and what SAs are established.
The leftsubnet= (client) in your conn is 216.112.83.64/26. It must
exactly match what pluto is looking for, and it does not.</pre>
<h3><a name="nosuit">Pluto: ... no suitable connection ...</a></h3>
<p>This is similar to the <a href="#noconn">no connection known</a> error,
but occurs at a different point in Pluto processing.</p>
<p>Here is one of Claudia's messages explaining the problem:</p>
<pre>You write,
> What could be the reason of the following error?
> "no suitable connection for peer '@xforce'"
When a connection is initiated by the peer, Pluto must choose which entry in
the conf file best matches the incoming connection. A preliminary choice is
made on the basis of source and destination IPs, since that information is
available at that time.
A payload containing an ID arrives later in the negotiation. Based on this
id and the *id= parameters, Pluto refines its conn selection. ...
The message "no suitable connection" indicates that in this refining step,
Pluto does not find a connection that matches that ID.
Please see "Selecting a connection when responding" in man ipsec_pluto for
more details.</pre>
<p>See also <a href="#conn_name">Connection names in Pluto error
messages</a>.</p>
<h3><a name="noconn.auth">Pluto: ... no connection has been
authorized</a></h3>
<p>Here is one of Claudia's messages discussing this problem:</p>
<pre>You write,
> May 22 10:46:31 debian Pluto[25834]: packet from x.y.z.p:10014:
> initial Main Mode message from x.y.z.p:10014
but no connection has been authorized
This error occurs early in the connection negotiation process,
at the first step of IKE negotiation (Main Mode), which is itself the
first of two negotiation phases involved in creating an IPSec connection.
Here, Linux FreeS/WAN receives a packet from a potential peer, which
requests that they begin discussing a connection.
The "no connection has been authorized" means that there is no connection
description in Linux FreeS/WAN's internal database that can be used to
link your ipsec interface with that peer.
"But of course I configured that connection!"
It may be that the appropriate connection description exists in ipsec.conf
but has not been added to the database with ipsec auto --add myconn or the
auto=add method. Or, the connection description may be misconfigured.
The only parameters that are relevant in this decision are left= and right= .
Local and remote ports are also taken into account -- we see that the port
is printed in the message above -- but there is no way to control these
in ipsec.conf.
Failure at "no connection has been authorized" is similar to the
"no connection is known for..." error in the FAQ, and the "no suitable
connection" error described in the snapshot's FAQ. In all three cases,
Linux FreeS/WAN is trying to match parameters received in the
negotiation with the connection description in the local config file.
As it receives more information, its matches take more parameters into
account, and become more precise: first the pair of potential peers,
then the peer IDs, then the endpoints (including any subnets).
The "no suitable connection for peer *" occurs toward the end of IKE
(Main Mode) negotiation, when the IDs are matched.
"no connection is known for a/b===c...d" is seen at the beginning of IPSec
(Quick Mode, phase 2) negotiation, when the connections are matched using
left, right, and any information about the subnets.</pre>
<h3><a name="noDESsupport">Pluto: ... OAKLEY_DES_CBC is not
supported.</a></h3>
<p>This message occurs when the other system attempts to negotiate a
connection using <a href="glossary.html#DES">single DES</a>, which we do not
support because it is <a href="politics.html#desnotsecure">insecure</a>.</p>
<p>Our interoperation document has suggestions for <a
href="interop.html#noDES">how to deal with</a> systems that attempt to use
single DES.</p>
<h3><a name="notransform">Pluto: ... no acceptable transform</a></h3>
<p>This message means that the other gateway has made a proposal for
connection parameters, but nothing they proposed is acceptable to Pluto.
Possible causes include:</p>
<ul>
<li>misconfiguration on either end</li>
<li>policy incompatibilities, for example we require encrypted connections
but they are trying to create one with just authentication</li>
<li>interoperation problems, for example they offer only single DES and
FreeS/WAN does not support that. See <a
href="interop.html#interop.problem">discussion</a> in our interoperation
document.</li>
</ul>
<p>A more detailed explanation, from Pluto programmer Hugh Redelmeier:</p>
<pre>Background:
When one IKE system (for example, Pluto) is negotiating with another
to create an SA, the Initiator proposes a bunch of choices and the
Responder replies with one that it has selected.
The structure of the choices is fairly complicated. An SA payload
contains a list of lists of "Proposals". The outer list is a set of
choices: the selection must be from one element of this list.
Each of these elements is a list of Proposals. A selection must be
made from each of the elements of the inner list. In other words,
*all* of them apply (that is how, for example, both AH and ESP can
apply at once).
Within each of these Proposals is a list of Transforms. For each
Proposal selected, one Transform must be selected (in other words,
each Proposal provides a choice of Transforms).
Each Transform is made up of a list of Attributes describing, well,
attributes. Such as lifetime of the SA. Such as algorithm to be
used. All the Attributes apply to a Transform.
You will have noticed a pattern here: layers alternate between being
disjunctions ("or") and conjunctions ("and").
For Phase 1 / Main Mode (negotiating an ISAKMP SA), this structure is
cut back. There must be exactly one Proposal. So this degenerates to
a list of Transforms, one of which must be chosen.
In your case, no proposal was considered acceptable to Pluto (the
Responder). So negotiation ceased. Pluto logs the reason it rejects
each Transform. So look back in the log to see what is going wrong.</pre>
<h3><a name="rsasigkey">rsasigkey dumps core</a></h3>
A comment on this error from Henry:
<pre>On Fri, 29 Jun 2001, Rodrigo Gruppelli wrote:
> ...Well, it seem that there's
> another problem with it. When I try to generate a pair of RSA keys,
> rsasigkey cores dump...
*That* is a neon sign flashing "GMP LIBRARY IS BROKEN". Rsasigkey calls
GMP a lot, and our own library a little bit, and that's very nearly all it
does. Barring bugs in its code or our library -- which have happened, but
not very often -- a problem in rsasigkey is a problem in GMP.</pre>
<p>See the next question for how to deal with GMP errors.</p>
<h3><a name="sig4">!Pluto failure!: ... exited with ... signal 4</a></h3>
<p>Pluto has died. Signal 4 is SIGILL, illegal instruction.</p>
<p>The most likely cause is that your <a href="glossary.html#GMP">GMP</a>
(GNU multi-precision) library is compiled for a different processor than what
you are running on. Pluto uses that library for its public key
calculations.</p>
<p>Try getting the GMP sources and recompile for your processor type. Most
Linux distributions will include this source, or you can download it from the
<a href="http://www.swox.com/gmp/">GMP home page</a>.</p>
<h3><a name="econnrefused">ECONNREFUSED error message</a></h3>
<p>From John Denker, on the mailing list:</p>
<pre>1) The log message
some IKE message we sent has been rejected with
ECONNREFUSED (kernel supplied no details)
is much more suitable than the previous version. Thanks.
2) Minor suggestion for further improvement: it might be worth mentioning
that the command
tcpdump -i eth1 icmp[0] != 8 and icmp[0] != 0
is useful for tracking down the details in question. We shouldn't expect
all IPsec users to figure that out on their own. The log message might
even provide a hint as to where to look in the docs.</pre>
<p>Reply From Pluto developer Hugh Redelmeier</p>
<pre>Good idea.
I've added a bit pluto(8)'s BUGS section along these lines.
I didn't have the heart to lengthen this message.</pre>
<h3><a name="no_eroute">klips_debug: ... no eroute!</a></h3>
<p>This message means <a href="glossary.html#KLIPS">KLIPS</a> has received a
packet for which no IPsec tunnel has been defined.</p>
<p>Here is a more detailed duscussion from the team's tech support person
Claudia Schmeing, responding to a query on the mailing list:</p>
<pre>> Why ipsec reports no eroute! ???? IP Masq... is disabled.
In general, more information is required so that people on the list may
give you informed input. See doc/prob.report.</pre>
<p>The document she refers to has since been replaced by a <a
href="trouble.html#prob.report">section</a> of the troubleshooting
document.</p>
<pre>However, I can make some general comments on this type of error.
This error usually looks something like this (clipped from an archived
message):
> ttl:64 proto:1 chk:45459 saddr:192.168.1.2 daddr:192.168.100.1
> ... klips_debug:ipsec_findroute: 192.168.1.2->192.168.100.1
> ... klips_debug:rj_match: * See if we match exactly as a host destination
> ... klips_debug:rj_match: ** try to match a leaf, t=0xc1a260b0
> ... klips_debug:rj_match: *** start searching up the tree, t=0xc1a260b0
> ... klips_debug:rj_match: **** t=0xc1a260c8
> ... klips_debug:rj_match: **** t=0xc1fe5960
> ... klips_debug:rj_match: ***** not found.
> ... klips_debug:ipsec_tunnel_start_xmit: Original head/tailroom: 2, 28
> ... klips_debug:ipsec_tunnel_start_xmit: no eroute!: ts=47.3030, dropping.
What does this mean?
- --------------------
"eroute" stands for "extended route", and is a special type of route
internal to Linux FreeS/WAN. For more information about this type of route,
see the section of man ipsec_auto on ipsec auto --route.
"no eroute!" here means, roughly, that Linux FreeS/WAN cannot find an
appropriate tunnel that should have delivered this packet. Linux
FreeS/WAN therefore drops the packet, with the message "no eroute! ...
dropping", on the assumption that this packet is not a legitimate
transmission through a properly constructed tunnel.
How does this situation come about?
- -----------------------------------
Linux FreeS/WAN has a number of connection descriptions defined in
ipsec.conf. These must be successfully brought "up" to form actual tunnels.
(see doc/setup.html's step 15, man ipsec.conf and man ipsec_auto
for details).
Such connections are often specific to the endpoints' IPs. However, in
some cases they may be more general, for example in the case of
Road Warriors where left or right is the special value %any.
When Linux FreeS/WAN receives a packet, it verifies that the packet has
come through a legitimate channel, by checking that there is an
appropriate tunnel through which this packet might legitimately have
arrived. This is the process we see above.
First, it checks for an eroute that exactly matches the packet. In the
example above, we see it checking for a route that begins at 192.168.1.2
and ends at 192.168.100.1. This search favours the most specific match that
would apply to the route between these IPs. So, if there is a connection
description exactly matching these IPs, the search will end there. If not,
the code will search for a more general description matching the IPs.
If there is no match, either specific or general, the packet will be
dropped, as we see, above.
Unless you are working with Road Warriors, only the first, specific part
of the matching process is likely to be relevant to you.
"But I defined the tunnel, and it came up, why do I have this error?"
- ---------------------------------------------------------------------
One of the most common causes of this error is failure to specify enough
connection descriptions to cover all needed tunnels between any two
gateways and their respective subnets. As you have noticed, troubleshooting
this error may be complicated by the use of IP Masq. However, this error is
not limited to cases where IP Masq is used.
See doc/configuration.html#multitunnel for a detailed example of the
solution to this type of problem.</pre>
<p>The documentation section she refers to is now <a
href="adv_config.html#multitunnel">here</a>.</p>
<h3><a name="SAused">... trouble writing to /dev/ipsec ... SA already in
use</a></h3>
<p>This error message occurs when two manual connections are set up with the
same SPI value. </p>
<p>See the FAQ for <a href="#spi_error">One manual connection works, but
second one fails</a>.</p>
<h3><a name="ignore">... ignoring ... payload</a></h3>
<p>This message is harmless. The IKE protocol provides for a number of
optional messages types:</p>
<ul>
<li>delete SA</li>
<li>initial contact</li>
<li>vendor ID</li>
<li>...</li>
</ul>
<p>An implementation is never required to send these, but they are allowed
to. The receiver is not required to do anything with them. FreeS/WAN ignores
them, but notifies you via the logs.</p>
<p>For the "ignoring delete SA Payload" message, see also our discussion of
cleaning up <a href="#deadtunnel">dead tunnels</a>.</p>
<h3><a name="unknown_rightcert">unknown parameter name "rightcert"</a></h3>
<P>This message can appear when you've upgraded an X.509-enabled
Linux FreeS/WAN with a vanilla Linux FreeS/WAN. To use your X.509 configs
you will need to overwrite the new install with
<A HREF="http://www.freeswan.ca">Super FreeS/WAN</A>, or add the
<A HREF="http://www.strongsec.ca/freeswan">X.509 patch</A> by hand.
</P>
<h2><a name="spam">Why don't you restrict the mailing lists to reduce
spam?</a></h2>
<p>As a matter of policy, some of our <a href="mail.html">mailing lists</a>
need to be open to non-subscribers. Project management feel strongly that
maintaining this openness is more important than blocking spam.</p>
<ul>
<li>Users should be able to get help or report bugs without
subscribing.</li>
<li>Even a user who is subscribed may not have access to his or her
subscribed account when he or she needs help, miles from home base in the
middle of setting up a client's gateway.</li>
<li>There is arguably a legal requirement for this policy. A US resident or
citizen could be charged under munitions export laws for providing
technical assistance to a foreign cryptographic project. Such a charge
would be more easily defended if the discussion takes place in public, on
an open list.</li>
</ul>
<p>This has been discussed several times at some length on the list. See the
<a href="mail.html#archive">list archives</a>. Bringing the topic up again is
unlikely to be useful. Please don't. Or at the very least, please don't
without reading the archives and being certain that whatever you are about to
suggest has not yet been discussed.</p>
<p>Project technical lead Henry Spencer summarised one discussion:</p>
<blockquote>
For the third and last time: this list *will* *not* do address-based
filtering. This is a policy decision, not an implementation problem. The
decision is final, and is not open to discussion. This needs to be
communicated better to people, and steps are being taken to do
that.</blockquote>
<p>Adding this FAQ section is one of the steps he refers to.</p>
<p>You have various options other than just putting up with the spam,
filtering it yourself, or unsubscribing:</p>
<ul>
<li>subscribe only to one or both of our lists with restricted posting
rules:
<ul>
<li><a
href="mailto:briefs@lists.freeswan.org?body=subscribe">briefs</a>,
weekly list summaries</li>
<li><a
href="mailto:announce@lists.freeswan.org?body=subscribe">announce</a>,
project-related announcements</li>
</ul>
</li>
<li>read the other lists via the <a
href="mail.html#archive">archives</a></li>
</ul>
<p>A number of tools are available to filter mail.</p>
<ul>
<li>Many mail readers include some filtering capability.</li>
<li>Many Linux distributions include <a
href="http://www.procmail.org/">procmail(8)</a> for server-side
filtering.</li>
<li>The <a href="http://www.spambouncer.org/">Spam Bouncer</a> is a set of
procmail(8) filters designed to combat spam.</li>
<li>Roaring Penguin have a <a
href="http://www.roaringpenguin.com/mimedefang/">MIME defanger</a> that
removes potentially dangerous attachments.</li>
</ul>
<p>If you use your ISP's mail server rather than running your own, consider
suggesting to the ISP that they tag suspected spam as <a
href="http://www.msen.com/1997/spam.html#SUSPECTED">this ISP</a> does. They
could just refuse mail from dubious sources, but that is tricky and runs some
risk of losing valuable mail or senselessly annoying senders and their
admins. However, they can safely tag and deliver dubious mail. The tags can
greatly assist your filtering.</p>
<p>For information on tracking down spammers, see these <a
href="http://www.rahul.net/falk/#howtos">HowTos</a>, or the <a
href="http://www.sputum.com/index2.html">Sputum</a> site. Sputum have a Linux
anti-spam screensaver available for download.</p>
<p>Here is a more detailed message from Henry:</p>
<pre>On Mon, 15 Jan 2001, Jay Vaughan wrote:
> I know I'm flogging a dead horse here, but I'm curious as to the reasons for
> an aversion for a subscriber-only mailing list?
Once again: for legal reasons, it is important that discussions of these
things be held in a public place -- the list -- and we do not want to
force people to subscribe to the list just to ask one question, because
that may be more than merely inconvenient for them. There are also real
difficulties with people who are temporarily forced to use alternate
addresses; that is precisely the time when they may be most in need of
help, yet a subscribers-only policy shuts them out.
These issues do not apply to most mailing lists, but for a list that is
(necessarily) the primary user support route for a crypto package, they
are very important. This is *not* an ordinary mailing list; it has to
function under awkward constraints that make various simplistic solutions
inapplicable or undesirable.
> We're *ALL* sick of hearing about list management problems, not just you
> old-timers, so why don't you DO SOMETHING EFFECTIVE ABOUT IT...
Because it's a lot harder than it looks, and many existing "solutions"
have problems when examined closely.
> A suggestion for you, based on 10 years of experience with management of my
> own mailing lists would be to use mailman, which includes pretty much every
> feature under the sun that you guys need and want, plus some. The URL for
> mailman...
I assure you, we're aware of mailman. Along with a whole bunch of others,
including some you almost certainly have never heard of (I hadn't!).
> As for the argument that the list shouldn't be configured to enforce
> subscription - I contend that it *SHOULD* AT LEAST require manual address
> verification in order for posts to be redirected.
You do realize, I hope, that interposing such a manual step might cause
your government to decide that this is not truly a public forum, and thus
you could go to jail if you don't get approval from them before mailing to
it? If you think this sounds irrational, your government is noted for
making irrational decisions in this area; we can't assume that they will
suddenly start being sensible. See above about awkward constraints. You
may be willing to take the risk, but we can't, in good conscience, insist
that all users with problems do so.
Henry Spencer
henry@spsystems.net</pre>
<p>and a message on the topic from project leader John Gilmore:</p>
<pre>Subject: Re: The linux-ipsec list's topic
Date: Sat, 30 Dec 2000
From: John Gilmore <gnu@toad.com>
I'll post this single message, once only, in this discussion, and then
not burden the list with any further off-topic messages. I encourage
everyone on the list to restrain themself from posting ANY off-topic
messages to the linux-ipsec list.
The topic of the linux-ipsec mailing list is the FreeS/WAN software.
I frequently see "discussions about spam on a list" overwhelm the
volume of "actual spam" on a list. BOTH kinds of messages are
off-topic messages. Twenty anti-spam messages take just as long to
detect and discard as twenty spam messages.
The Linux-ipsec list encourages on-topic messages from people who have
not joined the list itself. We will not censor messages to the list
based on where they originate, or what return address they contain.
In other words, non-subscribers ARE allowed to post, and this will not
change. My own valid contributions have been rejected out-of-hand by
too many other mailing lists for me to want to impose that censorship
on anybody else's contributions. And every day I see the damage that
anti-spam zeal is causing in many other ways; that zeal is far more
damaging to the culture of the Internet than the nuisance of spam.
In general, it is the responsibility of recipients to filter,
prioritize, or otherwise manage the handling of email that comes to
them. It is not the responsibility of the rest of the Internet
community to refrain from sending messages to recipients that they
might not want to see. If your software infrastructure for managing
your incoming email is insufficient, then improve it. If you think
the signal-to-noise ratio on linux-ipsec is too poor, then please
unsubscribe. But don't further increase the noise by posting to the
linux-ipsec list about those topics.
John Gilmore
founder & sponsor, FreeS/WAN project</pre>
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