[Swan] releasing old connection to free the route

[Christoph Litauer]

Hi,

I use libreswan 3.29 on an Ubuntu 20.04.3 LTS.

Until now we had a l2tp-setup using openswan 2.6.49 on an ubuntu 16.04.7. No problems, we had hundreds of users in parallel. Some of these users by accident use the same local ip address.

For security we have to upgrade to Ubuntu 20 and thus had to change to libreswan. Setup is nearly identical. But now we have a serious problem: 
- User A uses local ip 192.168.55.45 behind NAT. Public IP is 87.156.203.224 
- User B uses local ip 192.168.55.45 behind NAT. Public IP is 185.66.195.84

A starts the tunnel. As soon es B starts his tunnel, the tunnel for A is terminated and vice versa.

The log contains messages like this

Jan 24 13:50:18 l2tpnew pluto[21143]: "ikev1-nat"[109] 185.66.195.84 #137: route to peer's client conflicts with "ikev1-nat"[108] 87.156.203.224 87.156.203.224; releasing old connection to free the route

Jan 24 13:50:20 l2tpnew pluto[21143]: "ikev1-nat"[110] 87.156.203.224 #138: route to peer's client conflicts with "ikev1-nat"[109] 185.66.195.84 185.66.195.84; releasing old connection to free the route

We never had this kind of problem using 2.6.49. Seems as if it isn’t possible to use the same local ip in two connections, but this will happen very often in reality. Is there any help available?

Please don’t hesitate to ask for more logs or configuration files. As I am not very familiar with libreswan I didn’t know what would be of interest to solve the problem. Thanks a lot in advance!

-- 
Kind regards
Christoph
_________________________________________
Christoph Litauer
Uni Koblenz, Computing Centre, Office A 022    
Postfach 201602, 56016 Koblenz     
Fon: +49 261 287-1311, Fax: -100 1311