Re: [PATCH v7 4/5] nvme-tcp: Support KeyUpdate

[Hannes Reinecke]

On 3/4/26 06:34, alistair23@xxxxxxxxx wrote:
> From: Alistair Francis <alistair.francis@xxxxxxx>
>
> If the nvme_tcp_try_send() or nvme_tcp_try_recv() functions return
> EKEYEXPIRED then the underlying TLS keys need to be updated. This occurs
> on an KeyUpdate event as described in RFC8446
> https://datatracker.ietf.org/doc/html/rfc8446#section-4.6.3.
>
> If the NVMe Target (TLS server) initiates a KeyUpdate this patch will
> allow the NVMe layer to process the KeyUpdate request and forward the
> request to userspace. Userspace must then update the key to keep the
> connection alive.
>
> This patch allows us to handle the NVMe target sending a KeyUpdate
> request without aborting the connection. At this time we don't support
> initiating a KeyUpdate.
>
> Signed-off-by: Alistair Francis <alistair.francis@xxxxxxx>
> ---
> v7:
>   - Use read_sock_cmsg instead of recvmsg() to handle KeyUpdate
> v6:
>   - Don't use `struct nvme_tcp_hdr` to determine TLS_HANDSHAKE_KEYUPDATE,
>     instead look at the cmsg fields.
>   - Don't flush async_event_work
> v5:
>   - Cleanup code flow
>   - Check for MSG_CTRUNC in the msg_flags return from recvmsg
>     and use that to determine if it's a control message
> v4:
>   - Remove all support for initiating KeyUpdate
>   - Don't call cancel_work() when updating keys
> v3:
>   - Don't cancel existing handshake requests
> v2:
>   - Don't change the state
>   - Use a helper function for KeyUpdates
>   - Continue sending in nvme_tcp_send_all() after a KeyUpdate
>   - Remove command message using recvmsg
>
>   drivers/nvme/host/tcp.c | 59 ++++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 58 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
> index 8b6172dd1c0f..ade11d2ac9ef 100644
> --- a/drivers/nvme/host/tcp.c
> +++ b/drivers/nvme/host/tcp.c
> @@ -171,6 +171,7 @@ struct nvme_tcp_queue {
>   	bool			tls_enabled;
>   	u32			rcv_crc;
>   	u32			snd_crc;
> +	key_serial_t		handshake_session_id;
>   	__le32			exp_ddgst;
>   	__le32			recv_ddgst;
>   	struct completion       tls_complete;
> @@ -1361,6 +1362,59 @@ static int nvme_tcp_try_send(struct nvme_tcp_queue *queue)
>   	return ret;
>   }
>   
> +static void update_tls_keys(struct nvme_tcp_queue *queue)
> +{
> +	int qid = nvme_tcp_queue_id(queue);
> +	int ret;
> +
> +	dev_dbg(queue->ctrl->ctrl.device,
> +		"updating key for queue %d\n", qid);
> +
> +	ret = nvme_tcp_start_tls(&(queue->ctrl->ctrl),
> +				 queue, queue->ctrl->ctrl.tls_pskid,
> +				 HANDSHAKE_KEY_UPDATE_TYPE_RECEIVED);
> +
> +	if (ret < 0) {
> +		dev_err(queue->ctrl->ctrl.device,
> +			"failed to update the keys %d\n", ret);
> +		nvme_tcp_fail_request(queue->request);
> +	}
> +}
> +
> +static int nvme_tcp_recv_cmsg(read_descriptor_t *desc,
> +			      struct sk_buff *skb,
> +			      unsigned int offset, size_t len,
> +			      u8 content_type)
> +{
> +	struct nvme_tcp_queue *queue = desc->arg.data;
> +	struct socket *sock = queue->sock;
> +	struct sock *sk = sock->sk;
> +
> +	switch (content_type) {
> +	case TLS_RECORD_TYPE_HANDSHAKE:
> +		if (len == 5) {
> +			u8 header[5];
> +
> +			if (!skb_copy_bits(skb, offset, header,
> +					   sizeof(header))) {
> +				if (header[0] == TLS_HANDSHAKE_KEYUPDATE) {
> +					dev_err(queue->ctrl->ctrl.device, "KeyUpdate message\n");
> +					release_sock(sk);
> +					update_tls_keys(queue);
> +					lock_sock(sk);
> +					return 0;
> +				}
> +			}
> +		}
> +
> +		break;
> +	default:
> +		break;
> +	}

I think a simple 'if' condition would be sufficient here, or do you have
handling of other TLS record types queued somewhere?
And we should log unhandled TLS records.

> +
> +	return -EAGAIN;
> +}
> +
>   static int nvme_tcp_try_recv(struct nvme_tcp_queue *queue)
>   {
>   	struct socket *sock = queue->sock;
> @@ -1372,7 +1426,8 @@ static int nvme_tcp_try_recv(struct nvme_tcp_queue *queue)
>   	rd_desc.count = 1;
>   	lock_sock(sk);
>   	queue->nr_cqe = 0;
> -	consumed = sock->ops->read_sock(sk, &rd_desc, nvme_tcp_recv_skb);
> +	consumed = sock->ops->read_sock_cmsg(sk, &rd_desc, nvme_tcp_recv_skb,
> +					     nvme_tcp_recv_cmsg);
>   	release_sock(sk);
>   	return consumed == -EAGAIN ? 0 : consumed;
>   }
> @@ -1708,6 +1763,7 @@ static void nvme_tcp_tls_done(void *data, int status, key_serial_t pskid,
>   			ctrl->ctrl.tls_pskid = key_serial(tls_key);
>   		key_put(tls_key);
>   		queue->tls_err = 0;
> +		queue->handshake_session_id = handshake_session_id;
>   	}
>   
>   out_complete:
> @@ -1737,6 +1793,7 @@ static int nvme_tcp_start_tls(struct nvme_ctrl *nctrl,
>   		keyring = key_serial(nctrl->opts->keyring);
>   	args.ta_keyring = keyring;
>   	args.ta_timeout_ms = tls_handshake_timeout * 1000;
> +	args.ta_handshake_session_id = queue->handshake_session_id;
>   	queue->tls_err = -EOPNOTSUPP;
>   	init_completion(&queue->tls_complete);
>   	if (keyupdate == HANDSHAKE_KEY_UPDATE_TYPE_UNSPEC)

Otherwise looks good.

Cheers,

Hannes
--
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@xxxxxxx                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich