[strongSwan] manual bypass policy for client-server architecture using transport mode

Plevin phlevin at runbox.com
Wed Jul 13 16:53:31 CEST 2016

Hello Tobias,

Thanks much for your response.

FYI, the ipsec config you provided doesn't work without a strongSwan config change. Setting right to causes 
to swapleft and right:

> Jul 13 12:06:41 07[CFG]  received stroke: add connection 'client-1-bypass'
 > ...
> Jul 13 12:06:41 07[CFG]  left is other host, swapping ends
> Jul 13 12:06:41  07[CFG] added configuration 'client-1-bypass'

As a result, the bypass policies become inverted and they never match - all traffic goes over the non-bypassed SA.

The simple solution is to set the following strongSwan config:

   charon.plugins.allow_swap = no

I'm not sure if one would be expected to make such a change in order to get this bypass scenario to function,
but that's what worked for me.



On 7/12/2016 4:36 AM, Tobias Brunner wrote:
> Hi Plevin,
>>> conn client-1-bypass
>>>               left=
>>>               right=
>>>               rightsubnet=[tcp/5001]
>>>               leftfirewall=yes
>>>               type=passthrough
>>>               authby=secret
>>>               auto=add
> You configured this like a regular connection (left|right specified,
> leftfirewall=yes, authby=secret, auto=add).  So this might get
> established like one.  Instead you should set at least right to
> so it won't get used as responder, and configure the traffic
> selectors via left|rightsubnet (e.g. leftsubnet=,
> rightsubnet=[tcp/5001]).  leftfirewall=yes has no effect
> here, so if you need firewall rules to allow that traffic you have to
> install them yourself.  And to install the policies when the config is
> loaded use auto=route.  Same on the other host:
>>> conn server-bypass
>>>               right=
>>>               leftsubnet=[tcp/5001]
>>>               rightsubnet=
>>>               type=passthrough
>>>               auto=route
> Regards,
> Tobias

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