18. Null Crypto Poll Mode Driver

The Null Crypto PMD (librte_crypto_null) provides a crypto poll mode driver which provides a minimal implementation for a software crypto device. As a null device it does not modify the data in the mbuf on which the crypto operation is to operate and it only has support for a single cipher and authentication algorithm.

When a burst of mbufs is submitted to a Null Crypto PMD for processing then each mbuf in the burst will be enqueued in an internal buffer for collection on a dequeue call as long as the mbuf has a valid rte_mbuf_offload operation with a valid rte_cryptodev_session or rte_crypto_xform chain of operations.

18.1. Features

Modes:

  • RTE_CRYPTO_XFORM_CIPHER ONLY

  • RTE_CRYPTO_XFORM_AUTH ONLY

  • RTE_CRYPTO_XFORM_CIPHER THEN RTE_CRYPTO_XFORM_AUTH

  • RTE_CRYPTO_XFORM_AUTH THEN RTE_CRYPTO_XFORM_CIPHER

Cipher algorithms:

  • RTE_CRYPTO_CIPHER_NULL

Authentication algorithms:

  • RTE_CRYPTO_AUTH_NULL

18.2. Limitations

  • Only in-place is currently supported (destination address is the same as source address).

18.3. Installation

The Null Crypto PMD is enabled and built by default in both the Linux and FreeBSD builds.

18.4. Initialization

To use the PMD in an application, user must:

  • Call rte_vdev_init(“crypto_null”) within the application.

  • Use –vdev=”crypto_null” in the EAL options, which will call rte_vdev_init() internally.

The following parameters (all optional) can be provided in the previous two calls:

  • socket_id: Specify the socket where the memory for the device is going to be allocated (by default, socket_id will be the socket where the core that is creating the PMD is running on).

  • max_nb_queue_pairs: Specify the maximum number of queue pairs in the device (8 by default).

  • max_nb_sessions: Specify the maximum number of sessions that can be created (2048 by default).

Example:

./dpdk-l2fwd-crypto -l 1 -n 4 --vdev="crypto_null,socket_id=0,max_nb_sessions=128" \
-- -p 1 --cdev SW --chain CIPHER_ONLY --cipher_algo "null"