[Openswan dev] Phase 2 Negotiation Reliability

Michael Richardson mcr at sandelman.ottawa.on.ca
Thu Sep 16 10:27:27 CEST 2004


>>>>> "Herbert" == Herbert Xu <herbert at gondor.apana.org.au> writes:
    Herbert> Well since a modified DPD will solve the problem as well
    Herbert> (along with some other problems, e.g., phase 2 rekeyed,
    Herbert> responder reboots, phase 1 rekeyed due to normal expiration

    >> I don't agree that it is as easy to implement.
    >> The idea is to send ESP packets in the IPsec SA periodically.

    Herbert> I was thinking of something slightly different.

    Herbert> Based on a vendor ID, we can modify the DPD NOTIFYs to
    Herbert> carry information that identified a particular phase 2 SA.
    Herbert> That way we can directly verify its liveliness.

  I think that this can be done.
  We can actually just add an additional notify that contains the list
of current phase 2 SAs. 
  Unless I'm mis-thinking, each phase 2 has its own set of cookies, and
the DPD messages use the phase 1 cookies. 
  So, we could simply list the phase 2 cookies that we think are active.

  Alternatively, each end could list the IPsec SAs that are active for
incoming traffic. I would propose a notify that looks like:

         |  ver=4 |proto=50|       SPI#      |
         |    SPI#         |  IP dest of SPI |   
         | IP dest of SPI  |continues for v6 |

  I.e. a 10 byte structure for IPv4, and a 22 byte structure for IPv6.

  Upon receiption of such a notify, look up each SPI# and see if we are
using it. If we are *not* using it then send a delete.

  The assumption is that if one delete's the SAs that didn't get created
properly that they should get rekeyed.  This is the lazy version.

  A more active version would check to see if we have a hanging phase 2,
then attempt a rekey.
  I was also thinking ... why is it that message 2 of the phase 2 isn't
getting retransmitted longer when message 3 gets lost. The original
thread had some comments from about only 3 retransmits... 
  Can anyone suggest any netfilter modules that might help to build a
test case? I.e. something that will drop the first n-packets of a
stream. Or maybe I should use QoS for that.
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