Re: [PATCH net-next v2 4/7] psp: add core tracked stat for outstanding tx keys

[Kiran Kella]

On Sat, Oct 10, 2026 at 2:19 AM Daniel Zahka <daniel.zahka@xxxxxxxxx> wrote:
>
> It is useful to keep track of tx_key_cnt: the number of outstanding tx
> keys from the hw's perspective. Userspace can monitor this to
> determine if there is a key leak (leak in the sense that some device
> resource like an SADB entry has been leaked, not that the crypto key
> has been exposed).
>
> It also may be of interest to userspace if a device is approaching its
> SADB capacity.
>
> Only report this stat to userspace if the driver uses an SADB.
>
> Signed-off-by: Daniel Zahka <daniel.zahka@xxxxxxxxx>
> ---
>  Documentation/netlink/specs/psp.yaml | 8 ++++++++
>  include/net/psp/types.h              | 2 ++
>  include/uapi/linux/psp.h             | 1 +
>  net/psp/psp_main.c                   | 3 +++
>  net/psp/psp_nl.c                     | 4 ++++
>  net/psp/psp_sock.c                   | 6 +++++-
>  6 files changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/netlink/specs/psp.yaml b/Documentation/netlink/specs/psp.yaml
> index f3266763c325..d14c11d09891 100644
> --- a/Documentation/netlink/specs/psp.yaml
> +++ b/Documentation/netlink/specs/psp.yaml
> @@ -190,6 +190,13 @@ attribute-sets:
>          doc: |
>            Number of PSP packets for transmission with errors.
>            Device statistic (from the PSP spec).
> +      -
> +        name: tx-key-count
> +        type: uint
> +        doc: |
> +          Current number of Tx keys installed on the device.
> +          Only visible if the driver stores keys on device.
> +          Kernel statistic.
>

Maybe it is good to have a counter that denotes the number of PSP
sessions set up on a device, which is managed in
psp_dev_tx_key_add/psp_dev_tx_key_del operations similar to the
tx-key-count. That way, even in non-SADB drivers the user can know the
scale of the PSP sessions set up on a device at any time.

>  operations:
>    list:
> @@ -316,6 +323,7 @@ operations:
>              - tx-packets
>              - tx-bytes
>              - tx-error
> +            - tx-key-count
>          pre: psp-device-get-locked
>          post: psp-device-unlock
>        dump:
> diff --git a/include/net/psp/types.h b/include/net/psp/types.h
> index 8ffc566cec2a..970801cb6502 100644
> --- a/include/net/psp/types.h
> +++ b/include/net/psp/types.h
> @@ -90,6 +90,7 @@ struct psp_assoc_dev {
>   * @stats:     statistics maintained by the core
>   * @stats.rotations:   See stats attr key-rotations
>   * @stats.stales:      See stats attr stale-events
> + * @stats.tx_key_cnt:  See stats attr tx-key-count
>   *
>   * @rcu:       RCU head for freeing the structure
>   */
> @@ -125,6 +126,7 @@ struct psp_dev {
>         struct {
>                 unsigned long rotations;
>                 unsigned long stales;
> +               unsigned long tx_key_cnt;
>         } stats;
>
>         struct rcu_head rcu;
> diff --git a/include/uapi/linux/psp.h b/include/uapi/linux/psp.h
> index 1c8899cd4da5..21810e8a7229 100644
> --- a/include/uapi/linux/psp.h
> +++ b/include/uapi/linux/psp.h
> @@ -69,6 +69,7 @@ enum {
>         PSP_A_STATS_TX_PACKETS,
>         PSP_A_STATS_TX_BYTES,
>         PSP_A_STATS_TX_ERROR,
> +       PSP_A_STATS_TX_KEY_COUNT,
>
>         __PSP_A_STATS_MAX,
>         PSP_A_STATS_MAX = (__PSP_A_STATS_MAX - 1)
> diff --git a/net/psp/psp_main.c b/net/psp/psp_main.c
> index e118b8019e7e..9f256157d88b 100644
> --- a/net/psp/psp_main.c
> +++ b/net/psp/psp_main.c
> @@ -169,6 +169,9 @@ void psp_dev_unregister(struct psp_dev *psd)
>                 list_del(&pas->assocs_list);
>         }
>
> +       WARN(psd->stats.tx_key_cnt, "psp: %s: %lu Tx keys still installed\n",
> +            netdev_name(psd->main_netdev), psd->stats.tx_key_cnt);
> +
>         list_for_each_entry_safe(entry, entry_tmp, &psd->assoc_dev_list,
>                                  dev_list) {
>                 list_del(&entry->dev_list);
> diff --git a/net/psp/psp_nl.c b/net/psp/psp_nl.c
> index cdfc2d72fb39..494022ab5a71 100644
> --- a/net/psp/psp_nl.c
> +++ b/net/psp/psp_nl.c
> @@ -934,6 +934,10 @@ psp_nl_stats_fill(struct psp_dev *psd, struct sk_buff *rsp,
>             nla_put_uint(rsp, PSP_A_STATS_TX_ERROR, stats.tx_error))
>                 goto err_cancel_msg;
>
> +       if (psp_dev_has_sadb(psd) &&
> +           nla_put_uint(rsp, PSP_A_STATS_TX_KEY_COUNT, psd->stats.tx_key_cnt))
> +               goto err_cancel_msg;
> +
>         genlmsg_end(rsp, hdr);
>         return 0;
>
> diff --git a/net/psp/psp_sock.c b/net/psp/psp_sock.c
> index d21f7afd830a..c458bc551b4b 100644
> --- a/net/psp/psp_sock.c
> +++ b/net/psp/psp_sock.c
> @@ -94,9 +94,11 @@ static int psp_dev_tx_key_add(struct psp_dev *psd, struct psp_assoc *pas,
>
>         memcpy(&dummy->tx, key, sizeof(*key));
>         err = psd->ops->tx_key_add(psd, dummy, extack);
> -       if (!err)
> +       if (!err) {
> +               psd->stats.tx_key_cnt++;
>                 memcpy(pas->drv_data, dummy->drv_data,
>                        psd->caps->assoc_drv_spc);
> +       }
>
>         kfree(dummy);
>         return err;
> @@ -105,6 +107,8 @@ static int psp_dev_tx_key_add(struct psp_dev *psd, struct psp_assoc *pas,
>  void psp_dev_tx_key_del(struct psp_dev *psd, struct psp_assoc *pas)
>  {
>         psd->ops->tx_key_del(psd, pas);
> +       if (!WARN_ON_ONCE(!psd->stats.tx_key_cnt))
> +               psd->stats.tx_key_cnt--;
>  }
>
>  static void psp_assoc_free(struct work_struct *work)
>
> --
> 2.52.0
>
>

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