Re: [PATCH net-next v2 0/7] psp: support rekeying psp protected tcp connections

[Daniel Zahka]

On Fri Oct 9, 2026 at 4:46 PM EDT, Daniel Zahka wrote:
> The PSP architecture spec states the need for rekeying connections in
> the event of a device key rotation. After a device key rotation has
> occurred, a new rx derived key needs to be generated and sent out to the
> other end of the connection sometime before the next device key rotation
> occurs.
>
> Because PSP connections involve two different keys at each endpoint,
> one for decrypting ingress traffic, and one for encrypting egress
> traffic, there are two types of rekeying events that need to be
> supported. From the perspective of one endpoint of the connection:
>
> 1. rx rekey: we need to allocate a new spi + decryption key pair to
>    provide to our peer.
>
> 2. tx rekey: our peer has provided us with a new spi + encryption key
>    pair which we should use for encrypting traffic immediately.
>
> In the case of rx rekeying, there is a period where it makes sense to
> accept packets authenticated from either the previous or current spi. To
> deal with that, we allow a psp_assoc to remember the last spi that was
> valid on a socket due to a rekey. If authentication state does not match
> the most recent assoc, the stored state from the previous assoc will be
> tried.
>
> In the case of tx rekeying, as soon as we install the new tx key, we
> have no use for the previous one, and it can be disposed of immediately.
> The only catch is in the case where hw uses a key handle in tx
> descriptor state, as opposed to inlining the key directly. In this
> case, psp core needs to be sure that any of these unaccounted for
> references to key state are gone by the time it tries to sync a deleted
> key to hw.
>
> To deal with this race condition, we introduce a different path to key
> deletion for psp_assocs removed from the socket during a tx rekey. psp
> core will use bql byte counters filled out by the driver to determine a
> conservative grace period where key handles can be disposed of.
>
> Lastly, some test cases for rekeying are included that go through key
> rotations and rekeying.
>
> There are some packetdrill tests that are queued for upstreaming [1].
>
> [1]: https://github.com/danieldzahka/packetdrill/commits/psp-rekey/
>
> Signed-off-by: Daniel Zahka <daniel.zahka@xxxxxxxxx>

pw-bot: cr

Sorry, I should have tagged this myself for clarity. I'm planning to
send a v3 when net-next reopens to address some of the low level
complaints, as well as a CI issue introduced by the rekey drain test.