Re: [Users] Using dynamic Dialin with 2 IPSEC-Interfaces ???

From: D. Hugh Redelmeier (hugh_at_mimosa.com)
Date: Sat Jan 11 2003 - 19:59:43 CET


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| From: Michael Niehren <michael_at_niehren.de>

[It is good to keep your email text narrower than 80 or even 72
columns: that makes quoting work better. Of course you should not
break lines from logs and so on.]

| i tried out ipsec whack --listen, but that wasn't the solution. I got
| the same error. Maybe i can describe a simpler Setup, that you can
| evaluate too.

The first rule is: when interfaces change, you must restart freeswan.

You want to break that rule. That should be possible, with a great
deal of cunning. If I understood your early mail, you were really
close to getting this working. But remember: it is outside the design
of the system. I thought that I was giving you the last piece of the
puzzle.

I've never tried this myself, but it would be great if we could come
up with a recipe that would work.

Here is what I this needed to repair a changed interface:

- - I assume that external mechanisms get the physical interface right

- - the corresponding ipsec interface (ipsecN) needs to be ifconfigged
  with the correct address.

- - the interfaces need to be associated via an "ipsec tncfg" command.

- - once those steps are done, Pluto needs to rediscover the available
  interfaces: "ipsec whack --listen"
  Note: pluto doesn't directly care about the interfaces= setting
  in /etc/ipsec.conf.

- - the %defaultroute mechanism may need fixing. If you are not using
  it, let's not worry about it.

- - I think that SAs that used the interface that changed are broken
  by the change. Pluto may not know this. Probably the right fix
  is to do an additional "ipsec whack --listen" after the interface
  has gone down but before it is restored. Some experimentation
  would be useful.
  

| Ok,
| first you must have an Dialup Internet Connection (maybe ISDN or DSL).
|
| After the connection was established, adapt your new dynamic IP-Address
| and Gateway and starting your VPN-Connection. Everything is ok. So, now
| stopping your Internet-Connection without stopping the VPN, do only make
| an ipsec auto --down <connectionname> and ipsec auto --delete
| <connectionname>.

I recommend doing an "ipsec whack --listen" here so Pluto discovers
that the interface is down.

| Then do establish your Internet-Connection again, you got a different
| dynamic IP.

This is the point at which you need to either "ipsec setup restart" or
the tricky steps I outlined above:
- - ifconfigging the ipsecN device,
- - ipsec tncfg
- - and:
| I do an ipsec whack --listen,

Maybe this will work. Remember: I've not tried this, it is pure
theory.

| but the output is only
| [root_at_server ipsec]# ipsec whack --listen
| 002 listening for IKE messages
| 003 no public interfaces found

Right. Because you missed a few steps (ones that you had described in
earlier messages, so I thought you knew to do them).

This is interesting stuff. It would be good to figure out if this
technique works.

Hugh Redelmeier
hugh_at_mimosa.com voice: +1 416 482-8253

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