[strongSwan-dev] Adding support for subnets in transport mode (Feature #196)

Stuart Daniel stuartd at lexmark.com
Thu Jul 16 22:03:46 CEST 2015


On Thu, Jul 16, 2015 at 8:56 AM, Tobias Brunner <tobias at strongswan.org>

> Hi Stuart,
> > I've been looking at adding support for subnets when using transport
> > mode. In our use case, it will be far more efficient to allow users to
> > specify
> >     right=
> > instead of having to create a separate connection config for each host.
> > It appears that there has been some prior interest and work in this area:
> >   https://wiki.strongswan.org/issues/196
> I've updated the trap-any branch (based on the trap-acquire-tracking
> branch).  Due to the changes in 5.3.0 (reqids don't identify CHILD_SAs
> anymore) no additional reqids are required and no awkward SA deletion is
> needed anymore.  So that removes one of the reservations I had about the
> previous iteration of the patch.
> And with the above patch it is actually already possible to limit the
> remote hosts to specific subnets/IPs.  Just set `rightsubnet`
> accordingly.  I added a test scenario (ikev2/trap-any) in that branch
> that illustrates this (see host dave).
> Let me know if that works for you.

Thanks for the update; that works for our use case. I've tried the updated
trap-any branch, and it works well (in very limited testing) so far with
one caveat. If you specify
then things work as expected. If the administrator uses
however, the proposed traffic selector is for both sides instead
of This blocks traffic to *all* hosts, not just the
selected range, and leads to charon trying to initiate IKE even with hosts
that are not in the specified range.

This could be construed as a misconfiguration, but my reading of the
documentation implies that it is valid to specify a range for right. I
implemented a solution in my earlier patch, and can update it if needed to
base off this branch. The basic fix I went with was to catch the
substitution of any for the actual subnet in the trap_manager install
method, and use the subnet for the traffic selector later.


-- Stuart
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