If an IPsec SA is actually replaced with a rekeying its entry in the
manager is freed. That means that when the hard expire is triggered a
new entry might be found at the cached pointer location. So we have
to make sure we trigger the expire only if we found the right SA.
We could use SPI and addresses for the lookup, but this here requires
a bit less memory and is just a small change. Another option would be to
somehow cancel the queued job, but our scheduler doesn't allow that at
the moment.
Fixes#2399.
RFC 4303 reserves the SPIs between 1 and 255 for future use. This also
avoids an overflow and a division by zero if spi_min is 0 and spi_max is
0xffffffff.
This new flag gives the kernel-interface a hint how it should priorize the
use of newly installed SAs during rekeying.
Consider the following rekey procedure in IKEv2:
Initiator --- Responder
I1 -------CREATE-------> R1
I2 <------CREATE--------
-------DELETE-------> R2
I3 <------DELETE--------
SAs are always handled as pairs, the following happens at the SA level:
* Initiator starts the exchange at I1
* Responder installs new SA pair at R1
* Initiator installs new SA pair at I2
* Responder removes old SA pair at R2
* Initiator removes old SA pair at I3
This makes sure SAs get installed/removed overlapping during rekeying. However,
to avoid any packet loss, it is crucial that the new outbound SA gets
activated at the correct position:
* as exchange initiator, in I2
* as exchange responder, in R2
This should guarantee that we don't use the new outbound SA before the peer
could install its corresponding inbound SA.
The new parameter allows the kernel backend to install the new SA with
appropriate priorities, i.e. it should:
* as exchange inititator, have the new outbound SA installed with higher
priority than the old SA
* as exchange responder, have the new outbound SA installed with lower
priority than the old SA
While we could split up the SA installation at the responder, this approach
has another advantage: it allows the kernel backend to switch SAs based on
other criteria, for example when receiving traffic on the new inbound SA.
Tobias Brunner