While the the meaning of the "inbound" flag on the kernel_interface->add_sa()
call is not very clear, we still need that update logic to allow installation of
inbound SAs without SPI allocation. This is used in the HA plugin as a passive
node.
This reverts commit 698ed656.
As we now use the same reqid for multiple CHILD_SAs with the same selectors,
having marks based on the reqid makes not that much sense anymore. Instead we
use unique marks that use a custom identifier. This identifier is reused during
rekeying, keeping the marks constant for any rule relying on it (for example
installed by updown).
This also simplifies handling of reqid allocation, as we do not have to query
the marks that is not yet assigned for an unknown reqid.
The kernel backend uses an inbound parameter these days, where it makes
no sense to pass the update flag. The kernel backend decides itself how
it handles SA installation based on the inbound flag.
While we can handle the first selector only in BEET mode in kernel-netlink,
passing the full list gives the backend more flexibility how to handle this
information.
The reqid is not strictly required, as we set the reqid with the update
call when installing the negotiated SA.
If we don't need a reqid at this stage, we can later allocate the reqid in
the kernel backend once the SA parameters have been fully negotaited. This
allows us to assign the same reqid for the same selectors to avoid conflicts
on backends this is necessary.
While the outbound SA actually does not need a replay window, the kernel rejects
zero replay windows on SAs using ESN. The ESN flag is required to use the full
sequence number in ICV calculation, hence we set the replay window.
This restores the behavior we had before 30c009c2.
This will be useful if the kernel backend has to know how many policies
follow an SA install, for example if it must install all policies concurrently.
When we have a trap installed, but a CHILD_SA gets established for the same
config from the peer, we should reuse the same reqid. Otherwise we would have
two identical policies using different reqids, what we can't handle in our
kernel backend.
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.
If the installation failed the state is not CHILD_ROUTED which means the
wrong priority is used to uninstall the policies. This is a problem for
kernel interfaces that keep track of installed policies as now the proper
policy is not found (if the priority is considered).
During the update of a CHILD_SA (e.g. caused by MOBIKE) the old policy
is first uninstalled and then the new one is installed. In the short
time in between, where no policy is available in the kernel, unencrypted
packets could have been transmitted.
This allows to unroute a connection while the same connection is
currently established. In this case both CHILD_SAs share the same
reqid but the installed policies have different priorities.
This fixes several test cases in IKEv2_Self_Test (part of the IPv6 Ready
Logo Program) which is required for USGv6 certification, namely:
- IKEv2.EN.I.1.1.7.1, IKEv2.EN.I.1.1.7.1: Narrowing the range of members
of the set of traffic selectors
- IKEv2.EN.R.1.1.7.3: Narrowing multiple traffic selector
When traffic selectors of a triggered SA are narrowed by the responder, the
installed policy and the broader trap policy share the same reqid. Without
selectors on the IPsec SA packets matching the trap policy, but not the
narrowed policy, would incorrectly be handled by that IPsec SA. Since only
one selector can be specified per IPsec SA, there is currently no solution
for tunnel mode SAs.
Martin Willi