[strongSwan] masquerade tunneled traffic

Noel Kuntze noel at familie-kuntze.de
Wed Apr 29 07:51:41 CEST 2015


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Hello Chris,

That is because of this line:

0     0 ACCEPT     all  --  any    eth0    anywhere            !10.0.0.0/24 <http://10.0.0.0/24>          policy match dir out pol ipsec

I advise adjusting your MASQUERADE rule instead to except traffic with a matching IPsec policy from NAT.

Mit freundlichen Grüßen/Kind Regards,
Noel Kuntze

GPG Key ID: 0x63EC6658
Fingerprint: 23CA BB60 2146 05E7 7278 6592 3839 298F 63EC 6658

Am 27.04.2015 um 18:26 schrieb ch+strongswan at henniger.info:
> Hello,
>
> Hoping someone can help me:
>
> With the following LAN-LAN Setup
> Server 10.2.0.0/24 <http://10.2.0.0/24> - 1.1.1.1 --- 2.2.2.2 - 10.0.0.0/24 <http://10.0.0.0/24> Client
>
> I try to route the whole traffic from client through the server with masqueraded traffic to the public net.
>
> tcpdump on server shows the traffic is routed but not masquerade.
> (example from host (10.0.0.110) inside client net to public ip (www.heise.de <http://www.heise.de>))
>
> 17:45:47.871219 IP 10.0.0.110 > www.heise.de <http://www.heise.de>: ICMP echo request, id 20758, seq 6, length 64
>
> Thank you in advance for any advice.
>
> Chris
>
>
> My Configuration:
>
> Linux vpn 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt9-2 (2015-04-13) x86_64 GNU/Linux
> StrongSwan 5.2.1-6
>
> # cat /etc/ipsec.conf
> ---
> config setup
>
> conn %default
>         ikelifetime=60m
>         keylife=20m
>         rekeymargin=3m
>         keyingtries=1
>         authby=secret
>         keyexchange=ike
>         mobike=no
>
> conn divinus
>         left=1.1.1.1
>         leftsubnet=0.0.0.0/0 <http://0.0.0.0/0>
>         right=%any
>         rightsubnet=10.0.0.0/24 <http://10.0.0.0/24>
>         auto=add
> ---
>
>
> # ip xfrm policy
> ---                      
> src 10.0.0.0/24 <http://10.0.0.0/24> dst 10.2.0.0/24 <http://10.2.0.0/24>
>         dir fwd priority 2883 ptype main
>         tmpl src 2.2.2.2 dst 1.1.1.1
>                 proto esp reqid 1 mode tunnel
> src 10.0.0.0/24 <http://10.0.0.0/24> dst 10.2.0.0/24 <http://10.2.0.0/24>
>         dir in priority 2883 ptype main
>         tmpl src 2.2.2.2 dst 1.1.1.1
>                 proto esp reqid 1 mode tunnel
> src 10.2.0.0/24 <http://10.2.0.0/24> dst 10.0.0.0/24 <http://10.0.0.0/24>
>         dir out priority 2883 ptype main
>         tmpl src 1.1.1.1 dst 2.2.2.2
>                 proto esp reqid 1 mode tunnel
> src 0.0.0.0/0 <http://0.0.0.0/0> dst 0.0.0.0/0 <http://0.0.0.0/0>
>         socket in priority 0 ptype main
> src 0.0.0.0/0 <http://0.0.0.0/0> dst 0.0.0.0/0 <http://0.0.0.0/0>
>         socket out priority 0 ptype main
> src 0.0.0.0/0 <http://0.0.0.0/0> dst 0.0.0.0/0 <http://0.0.0.0/0>
>         socket in priority 0 ptype main
> src 0.0.0.0/0 <http://0.0.0.0/0> dst 0.0.0.0/0 <http://0.0.0.0/0>
>         socket out priority 0 ptype main
> src ::/0 dst ::/0
>         socket in priority 0 ptype main
> src ::/0 dst ::/0
>         socket out priority 0 ptype main
> src ::/0 dst ::/0
>         socket in priority 0 ptype main
> src ::/0 dst ::/0
>         socket out priority 0 ptype main
>
>
>
> # route
> Kernel-IP-Routentabelle
> Ziel            Router          Genmask         Flags Metric Ref    Use Iface
> default         1.1.1.1         0.0.0.0         UG    0      0        0 eth0
> 10.2.0.0        *               255.255.255.0   U     0      0        0 eth0
> 1.1.1.0         1.1.1.1         255.255.255.0   UG    0      0        0 eth0
> 1.1.1.0         *               255.255.255.0   U     0      0        0 eth0
>
>
>
> # cat /proc/sys/net/ipv4/ip_forward
> 1
>
>
>
> # iptables -L -v
> ---
> Chain INPUT (policy ACCEPT 9111 packets, 573K bytes)
>  pkts bytes target     prot opt in     out     source               destination        
>
> Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
>  pkts bytes target     prot opt in     out     source               destination        
>
> Chain OUTPUT (policy ACCEPT 891 packets, 128K bytes)
>  pkts bytes target     prot opt in     out     source               destination
> ---
>
>
> # iptables -t nat -L -v
> ---
> Chain PREROUTING (policy ACCEPT 3705 packets, 221K bytes)
>  pkts bytes target     prot opt in     out     source               destination        
>
> Chain INPUT (policy ACCEPT 1596 packets, 89736 bytes)
>  pkts bytes target     prot opt in     out     source               destination        
>
> Chain OUTPUT (policy ACCEPT 1700 packets, 120K bytes)
>  pkts bytes target     prot opt in     out     source               destination        
>
> Chain POSTROUTING (policy ACCEPT 8 packets, 672 bytes)
>  pkts bytes target     prot opt in     out     source               destination        
>     0     0 ACCEPT     all  --  any    eth0    anywhere            !10.0.0.0/24 <http://10.0.0.0/24>          policy match dir out pol ipsec
>     0     0 LOG        all  --  any    eth0    anywhere            !10.0.0.0/24 <http://10.0.0.0/24>          policy match dir out pol ipsec LOG level warning
>  1709  121K MASQUERADE  all  --  any    eth0    anywhere            !10.0.0.0/24 <http://10.0.0.0/24>
> ---
>
>
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