Openswan's ipsec verify fails on "Two or more interfaces found, checking IP forwarding"

Question

I'm trying to set an L2TP/IPsec VPN. I have installed openswan from the repository on Ubuntu 13.04

Section: universe/net
Architecture: amd64
Version: 1:2.6.38-1

and configured it following the community docs.

# cat /etc/ipsec.conf 
config setup
    nat_traversal=yes
    virtual_private=%v4:10.0.0.0/8,%v4:192.168.0.0/16,%v4:172.16.0.0/12,%v4:!192.168.23.0/24
    oe=off
    protostack=netkey

conn L2TP-PSK-NAT
    rightsubnet=vhost:%priv
    also=L2TP-PSK-noNAT

conn L2TP-PSK-noNAT
    authby=secret
    pfs=no
    auto=add
    keyingtries=3
    rekey=no
    # Apple iOS doesn't send delete notify so we need dead peer detection
    # to detect vanishing clients
    dpddelay=30
    dpdtimeout=120
    dpdaction=clear
    # Set ikelifetime and keylife to same defaults windows has
    ikelifetime=8h
    keylife=1h
    type=transport
    # Replace IP address with your local IP (private, behind NAT IP is okay as well)
    left=my.ip
    # For updated Windows 2000/XP clients,
    # to support old clients as well, use leftprotoport=17/%any
    leftprotoport=17/1701
    right=%any
    rightprotoport=17/%any
    #force all to be nat'ed. because of iOS
    forceencaps=yes

It starts fine but fails the verification

# ipsec verify
Checking your system to see if IPsec got installed and started correctly:
Version check and ipsec on-path                                 [OK]
Linux Openswan U2.6.38/K3.8.0-29-generic (netkey)
Checking for IPsec support in kernel                            [OK]
 SAref kernel support                                           [N/A]
 NETKEY:  Testing XFRM related proc values                      [OK]
[OK]
[OK]
Checking that pluto is running                                  [OK]
 Pluto listening for IKE on udp 500                             [OK]
 Pluto listening for NAT-T on udp 4500                          [OK]
Two or more interfaces found, checking IP forwarding            [FAILED]
Checking NAT and MASQUERADEing                                  [OK]
Checking for 'ip' command                                       [OK]
Checking /bin/sh is not /bin/dash                               [OK]
Checking for 'iptables' command                                 [OK]
Opportunistic Encryption Support                                [DISABLED]

even though forwarding seems to be enabled

# cat /proc/sys/net/ipv4/ip_forward
1

What's wrong and how do I fix it?

Answer 1

Stumbled over this while looking up the error :

I think this is the answer :

https://lists.openswan.org/pipermail/users/2009-September/017423.html

I have just upgraded to 2.6.23 and run ipsec verify and I get an unexpected error: Two or more interfaces found, checking IP forwarding [FAILED]

cat /proc/sys/net/ipv4/ip_forward gives 1 so I am confused.

If it helps eth0 is my WAN, eth1 is my normal LAN, eth1:0 is a virtual IP on eth1 to get round a problem I have been having with running Openswan on a combined gateway/file server, and eth2 is a second, unused LAN adaptor.

Then you can ignore it. It's a warning when running a subnet-subnet or subnet-host tunnel on the subnet side, where you need forwarding to go from the public side (internet) to the lan.