This document covers several general places where you might have a problem:
This document also contains notes which expand on points made in these sections, and tips for problem reporting. If the other end of your connection is not FreeS/WAN, you'll also want to read our interoperation document.
With the RPM method:
freeswan-userland-2.00_2.4.18_3custom-0.i386.rpm
freeswan-module-2.00_2.4.18_3custom-0.i386.rpm
When installing from source, you may find these problems:
ipsec verify checks a number of FreeS/WAN essentials. Here are some hints on what do to when your system doesn't check out:
| Problem | Status | Action |
| ipsec not on-path |
Add /usr/local/sbin to your PATH. | |
| Missing KLIPS support | critical | See this FAQ. |
| No RSA private key |
Follow these instructions to create an RSA key pair for your host. RSA keys are:
| |
| pluto not running | critical |
service ipsec start |
| No port 500 hole | critical | Open port 500 for IKE negotiation. |
| Port 500 check N/A | Check that port 500 is open for IKE negotiation. | |
| Failed DNS checks | Opportunistic encryption requires information from DNS. To set this up, see our instructions. | |
| No public IP address | Check that the interface which you want to protect with IPSec is up and running. |
When you fail to bring up a tunnel, you'll need to find out:
before you can diagnose your problem .
You can see connection states (STATE_MAIN_I1 and so on) when you bring up a connection on the command line. If you have missed this, or brought up your connection automatically, use:
ipsec auto --status
The most relevant state is the last one reached.
Negotiations should proceed though various states, in the processes of:
These are done and a connection is established when you see messages like:
000 #21: "myconn" STATE_MAIN_I4 (ISAKMP SA established)...
000 #2: "myconn" STATE_QUICK_I2 (sent QI2, IPsec SA established)...
Look for the key phrases are "ISAKMP SA established" and "IPSec SA established", with the relevant connection name. Often, this happens at STATE_MAIN_I4 and STATE_QUICK_I2, respectively.
ipsec auto --status will tell you what states have been achieved, rather than the current state. Since determining the current state is rather more difficult to do, current state information is not available from Linux FreeS/WAN. If you are actively bringing a connection up, the status report's last states for that connection likely reflect its current state. Beware, though, of the case where a connection was correctly brought up but is now downed: Linux FreeS/WAN will not notice this until it attempts to rekey. Meanwhile, the last known state indicates that the connection has been established.
If your connection is stuck at STATE_MAIN_I1, skip straight to here.
Solving most errors will require you to find verbose error text, either on the command line or in the logs.
Note that you can get more detail from ipsec auto using the --verbose flag:
ipsec auto --verbose --up west-east
More complete information can be gleaned from the log files.
The amount of description you'll get here depends on ipsec.conf debug settings, klipsdebug= and plutodebug=. When troubleshooting, set at least one of these to all, and when done, reset it to none so your logs don't fill up. Note that you must have enabled the klipsdebug compile-time option for the klipsdebug configuration switch to work.
For negotiation problems plutodebug is most relevant. klipsdebug applies mainly to attempts to use an already-established connection. See also this description of the division of duties within Linux FreeS/WAN.
After raising your debug levels, restart Linux FreeS/WAN to ensure that ipsec.conf is reread, then recreate the error to generate verbose logs.
ipsec barf (8) collects a bunch of useful debugging information, including these logs Use the command
ipsec barf > barf.west
to generate one.
Search out the failure point in your logs. Are there a handful of lines which succinctly describe how things are going wrong or contrary to your expectation? Sometimes the failure point is not immediately obvious: Linux FreeS/WAN's errors are usually not marked "Error". Have a look in the FAQ for what some common failures look like.
Tip: problems snowball. Focus your efforts on the first problem, which is likely to be the cause of later errors.
Also find error text on the peer IPSec box. This gives you two perspectives on the same failure.
At times you will require information which only one side has. The peer can merely indicate the presence of an error, and its approximate point in the negotiations. If one side keeps retrying, it may be because there is a show stopper on the other side. Have a look at the other side and figure out what it doesn't like.
If the other end is not Linux FreeS/WAN, the principle is the same: replicate the error with its most verbose logging on, and capture the output to a file.
This error commonly happens because IKE (port 500) packets, needed to negotiate an IPSec connection, cannot travel freely between your IPSec gateways. See our firewall document for details.
Other errors require a bit more digging. Use the following resources:
If you have failed to solve your problem with the help of these resources, send a detailed problem report to the users list, following these guidelines.
Test your connection by sending packets through it. The simplest way to do this is with ping, but the ping needs to test the correct tunnel. See this example scenario if you don't understand this.
If your ping returns, test any other connections you've brought u all check out, great. You may wish to test with large packets for MTU problems.
If your ping fails to return, generate an ipsec barf debugging report on each IPSec gateway. On a non-Linux FreeS/WAN implementation, gather equivalent information. Use this, and the tips in the next sections, to troubleshoot. Are you sure that both endpoints are capable of hearing and responding to ping?
IPSec may be dropping your ping packets since they do not belong in the tunnels you have constructed:
In either case, you will often see a message like:
klipsdebug... no eroute
which we discuss in this FAQ.
Note:
If you've confirmed your configuration assumptions, the problem is almost certainly with routing or firewalling. Isolate the problem using interface statistics, firewall statistics, or a packet sniffer.
Interface reports and firewall statistics can help you track down lost packets at a glance.
Check any firewall statistics you may be keeping on your IPSec gateways, for dropped packets.
Both cat /proc/net/dev and ifconfig display interface statistics, and both are included in ipsec barf. Use either to check if any interface has dropped packets. If you find that one has, test whether this is related to your ping. While you ping continuously, print that interface's statistics several times. Does its drop count increase in proportion to the ping? If so, check why the packets are dropped there.
To do this, look at the firewall rules that apply to that interface. If the interface is an IPSec interface, more information may be available in the log. Grep for the word "drop" in a log which was created with klipsdebug=all as the error happened.
See also this discussion on interpreting ifconfig statistics.
If you have checked configuration assumptions, routing, and firewall rules, and your interface statistics yield no clue, it remains for you to investigate the mystery of the lost packet by the most thorough method: with a packet sniffer (providing, of course, that this is legal where you are working).
In order to detect packets on the ipsec virtual interfaces, you will need an up-to-date sniffer (tcpdump, ethereal, ksnuffle) on your IPSec gateway machines. You may also find it useful to sniff the ping endpoints.
Ping, and examine each interface along the projected path, checking for your ping's arrival. If it doesn't get to the the next stop, you have narrowed down where to look for it. In this way, you can isolate a problem area, and narrow your troubleshooting focus.
Within a machine running Linux FreeS/WAN, this packet flow diagram will help you anticipate a packet's path.
Note that:
Once you isolate where the packet is lost, take a closer look at firewall rules, routing and configuration assumptions as they affect that specific area. If the packet is lost on an IPSec gateway, comb through klipsdebug output for anomalies.
If the packet goes through both gateways successfully and reaches the ping target, but does not return, suspect routing. Check that the ping target routes packets back to the IPSec gateway.
Here, too, log information can be useful. Start with the guidelines above.
For connection use problems, set klipsdebug=all. Note that you must have enabled the klipsdebug compile-time option to do this. Restart Linux FreeS/WAN so that it rereads ipsec.conf, then recreate the error condition. When searching through klipsdebug data, look especially for the keywords "drop" (as in dropped packets) and "error".
Often the problem with connection use is not software error, but rather that the software is behaving contrary to expectation.
To interpret the Linux FreeS/WAN log text you've found, use the same resources as indicated for troubleshooting connection negotiation: the FAQ , our background document, and the list archives. Looking in the KLIPS code is only for the very brave.
If you are still stuck, send a detailed problem report to the users' list.
If each of your connections passed the ping test, you may wish to test by pinging with large packets (2000 bytes or larger). If it does not return, suspect MTU issues, and see this discussion.
In most users' view, a simple ping test, and perhaps a large-packet ping test suffice to indicate a working IPSec connection.
Some people might like to do additional stress tests prior to production use. They may be interested in this testing protocol we use at interoperation conferences, aka "bakeoffs". We also have a testing directory that ships with the release.
Ask for troubleshooting help on the users' mailing list, users@lists.freeswan.org. While sometimes an initial query with a quick description of your intent and error will twig someone's memory of a similar problem, it's often necessary to send a second mail with a complete problem report.
The essay How to Report Bugs Effectively contains good guidelines.
When reporting problems to the mailing list(s), please include:
To report a problem, send mail about it to the users' list. If you are certain that you have found a bug, report it to the bugs list. If you encounter a problem while doing your own coding on the Linux FreeS/WAN codebase and think it is of interest to the design team, notify the design list. When in doubt, default to the users' list. More information about the mailing lists is found here.
For a number of reasons -- including export-control regulations affecting almost any private discussion of encryption software -- we prefer that problem reports and discussions go to the lists, not directly to the team. Beware that the list goes worldwide; US citizens, read this important information about your export laws. If you're using this software, you really should be on the lists. To get onto them, visit lists.freeswan.org.
If you do send private mail to our coders or want a private reply from them, please make sure that the return address on your mail (From or Reply-To header) is a valid one. They have more important things to do than to unravel addresses that have been mangled in an attempt to confuse spammers.
The following sections supplement the Guide: information available on your system; testing between security gateways; ifconfig reports for KLIPS debugging; using GDB on Pluto.
Linux FreeS/WAN logs to:
Check both places to get full information. If you find nothing, check your syslogd.conf(5) to see where your /etc/syslog.conf or equivalent is directing authpriv messages.
Other man pages are on this list and in
Sometimes you need to test a subnet-subnet tunnel. This is a tunnel between two security gateways, which protects traffic on behalf of the subnets behind these gateways. On this network:
Sunset==========West------------------East=========Sunrise
IPSec gateway IPSec gateway
local net untrusted net local net
you might name this tunnel sunset-sunrise. You can test this tunnel by having a machine behind one gateway ping a machine behind the other gateway, but this is not always convenient or even possible.
Simply pinging one gateway from the other is not useful. Such a ping does not normally go through the tunnel. The tunnel handles traffic between the two protected subnets, not between the gateways . Depending on the routing in place, a ping might
Neither event tells you anything about the tunnel. You can explicitly create an eroute to force such packets through the tunnel, or you can create additional tunnels as described in our configuration document, but those may be unnecessary complications in your situation.
The trick is to explicitly test between both gateways' private-side IP addresses. Since the private-side interfaces are on the protected subnets, the resulting packets do go via the tunnel. Use either ping -I or traceroute -i, both of which allow you to specify a source interface. (Note: unsupported on older Linuxes). The same principles apply for a road warrior (or other) case where only one end of your tunnel is a subnet.
When diagnosing problems using ifconfig statistics, you may wonder what type of activity increments a particular counter for an ipsecN device. Here's an index, posted by KLIPS developer Richard Guy Briggs:
Here is a catalogue of the types of errors that can occur for which
statistics are kept when transmitting and receiving packets via klips.
I notice that they are not necessarily logged in the right counter.
. . .
Sources of ifconfig statistics for ipsec devices
rx-errors:
- packet handed to ipsec_rcv that is not an ipsec packet.
- ipsec packet with payload length not modulo 4.
- ipsec packet with bad authenticator length.
- incoming packet with no SA.
- replayed packet.
- incoming authentication failed.
- got esp packet with length not modulo 8.
tx_dropped:
- cannot process ip_options.
- packet ttl expired.
- packet with no eroute.
- eroute with no SA.
- cannot allocate sk_buff.
- cannot allocate kernel memory.
- sk_buff internal error.
The standard counters are:
struct enet_statistics
{
int rx_packets; /* total packets received */
int tx_packets; /* total packets transmitted */
int rx_errors; /* bad packets received */
int tx_errors; /* packet transmit problems */
int rx_dropped; /* no space in linux buffers */
int tx_dropped; /* no space available in linux */
int multicast; /* multicast packets received */
int collisions;
/* detailed rx_errors: */
int rx_length_errors;
int rx_over_errors; /* receiver ring buff overflow */
int rx_crc_errors; /* recved pkt with crc error */
int rx_frame_errors; /* recv'd frame alignment error */
int rx_fifo_errors; /* recv'r fifo overrun */
int rx_missed_errors; /* receiver missed packet */
/* detailed tx_errors */
int tx_aborted_errors;
int tx_carrier_errors;
int tx_fifo_errors;
int tx_heartbeat_errors;
int tx_window_errors;
};
of which I think only the first 6 are useful.
You may need to use the GNU debugger, gdb(1), on Pluto. This should be necessary only in unusual cases, for example if you encounter a problem which the Pluto developer cannot readily reproduce or if you are modifying Pluto.
Here are the Pluto developer's suggestions for doing this:
Can you get a core dump and use gdb to find out what Pluto was doing
when it died?
To get a core dump, you will have to set dumpdir to point to a
suitable directory (see ipsec.conf(5)).
To get gdb to tell you interesting stuff:
$ script
$ cd dump-directory-you-chose
$ gdb /usr/local/lib/ipsec/pluto core
(gdb) where
(gdb) quit
$ exit
The resulting output will have been captured by the script command in
a file called "typescript". Send it to the list.
Do not delete the core file. I may need to ask you to print out some
more relevant stuff.
Note that the dumpdir parameter takes effect only when the IPsec subsystem is restarted -- reboot or ipsec setup restart.