2. IPsec Packet Processing Library

DPDK provides a library for IPsec data-path processing. The library utilizes the existing DPDK crypto-dev and security API to provide the application with a transparent and high performant IPsec packet processing API. The library is concentrated on data-path protocols processing (ESP and AH), IKE protocol(s) implementation is out of scope for this library.

2.1. SA level API

This API operates on the IPsec Security Association (SA) level. It provides functionality that allows user for given SA to process inbound and outbound IPsec packets.

To be more specific:

for inbound ESP/AH packets perform decryption, authentication, integrity checking, remove ESP/AH related headers
for outbound packets perform payload encryption, attach ICV, update/add IP headers, add ESP/AH headers/trailers,
setup related mbuf fields (ol_flags, tx_offloads, etc.).
initialize/un-initialize given SA based on user provided parameters.

The SA level API is based on top of crypto-dev/security API and relies on them to perform actual cipher and integrity checking.

Due to the nature of the crypto-dev API (enqueue/dequeue model) the library introduces an asynchronous API for IPsec packets destined to be processed by the crypto-device.

The expected API call sequence for data-path processing would be:

/* enqueue for processing by crypto-device */
rte_ipsec_pkt_crypto_prepare(...);
rte_cryptodev_enqueue_burst(...);
/* dequeue from crypto-device and do final processing (if any) */
rte_cryptodev_dequeue_burst(...);
rte_ipsec_pkt_crypto_group(...); /* optional */
rte_ipsec_pkt_process(...);

For packets destined for inline processing no extra overhead is required and the synchronous API call: rte_ipsec_pkt_process() is sufficient for that case.

Note

For more details about the IPsec API, please refer to the DPDK API Reference.

The current implementation supports all four currently defined rte_security types:

2.1.1. RTE_SECURITY_ACTION_TYPE_NONE

In that mode the library functions perform

for inbound packets:
- check SQN
- prepare rte_crypto_op structure for each input packet
- verify that integrity check and decryption performed by crypto device completed successfully
- check padding data
- remove outer IP header (tunnel mode) / update IP header (transport mode)
- remove ESP header and trailer, padding, IV and ICV data
- update SA replay window
for outbound packets:
- generate SQN and IV
- add outer IP header (tunnel mode) / update IP header (transport mode)
- add ESP header and trailer, padding and IV data
- prepare rte_crypto_op structure for each input packet
- verify that crypto device operations (encryption, ICV generation) were completed successfully

2.1.2. RTE_SECURITY_ACTION_TYPE_CPU_CRYPTO

In that mode the library functions perform same operations as in RTE_SECURITY_ACTION_TYPE_NONE. The only difference is that crypto operations are performed with CPU crypto synchronous API.

2.1.3. RTE_SECURITY_ACTION_TYPE_INLINE_CRYPTO

In that mode the library functions perform

for inbound packets:
- verify that integrity check and decryption performed by rte_security device completed successfully
- check SQN
- check padding data
- remove outer IP header (tunnel mode) / update IP header (transport mode)
- remove ESP header and trailer, padding, IV and ICV data
- update SA replay window
for outbound packets:
- generate SQN and IV
- add outer IP header (tunnel mode) / update IP header (transport mode)
- add ESP header and trailer, padding and IV data
- update ol_flags inside struct rte_mbuf to indicate that inline-crypto processing has to be performed by HW on this packet
- invoke rte_security device specific set_pkt_metadata() to associate security device specific data with the packet

2.1.4. RTE_SECURITY_ACTION_TYPE_INLINE_PROTOCOL

In that mode the library functions perform

for inbound packets:
- verify that integrity check and decryption performed by rte_security device completed successfully
for outbound packets:
- update ol_flags inside struct rte_mbuf to indicate that inline-crypto processing has to be performed by HW on this packet
- invoke rte_security device specific set_pkt_metadata() to associate security device specific data with the packet

2.1.5. RTE_SECURITY_ACTION_TYPE_LOOKASIDE_PROTOCOL

In that mode the library functions perform

for inbound packets:
- prepare rte_crypto_op structure for each input packet
- verify that integrity check and decryption performed by crypto device completed successfully
for outbound packets:
- prepare rte_crypto_op structure for each input packet
- verify that crypto device operations (encryption, ICV generation) were completed successfully

To accommodate future custom implementations function pointers model is used for both crypto_prepare and process implementations.

2.2. SA database API

SA database(SAD) is a table with <key, value> pairs.

Value is an opaque user provided pointer to the user defined SA data structure.

According to RFC4301 each SA can be uniquely identified by a key which is either:

security parameter index(SPI)

or SPI and destination IP(DIP)

or SPI, DIP and source IP(SIP)

In case of multiple matches, longest matching key will be returned.

2.2.1. Create/destroy

librte_ipsec SAD implementation provides ability to create/destroy SAD tables.

To create SAD table user has to specify how many entries of each key type is required and IP protocol type (IPv4/IPv6). As an example:

struct rte_ipsec_sad *sad;
struct rte_ipsec_sad_conf conf;

conf.socket_id = -1;
conf.max_sa[RTE_IPSEC_SAD_SPI_ONLY] = some_nb_rules_spi_only;
conf.max_sa[RTE_IPSEC_SAD_SPI_DIP] = some_nb_rules_spi_dip;
conf.max_sa[RTE_IPSEC_SAD_SPI_DIP_SIP] = some_nb_rules_spi_dip_sip;
conf.flags = RTE_IPSEC_SAD_FLAG_RW_CONCURRENCY;

sad = rte_ipsec_sad_create("test", &conf);

Note

for more information please refer to ipsec library API reference

2.2.2. Add/delete rules

Library also provides methods to add or delete key/value pairs from the SAD. To add user has to specify key, key type and a value which is an opaque pointer to SA. The key type reflects a set of tuple fields that will be used for lookup of the SA. As mentioned above there are 3 types of a key and the representation of a key type is:

RTE_IPSEC_SAD_SPI_ONLY,
RTE_IPSEC_SAD_SPI_DIP,
RTE_IPSEC_SAD_SPI_DIP_SIP,

As an example, to add new entry into the SAD for IPv4 addresses:

struct rte_ipsec_sa *sa;
union rte_ipsec_sad_key key;

key.v4.spi = rte_cpu_to_be_32(spi_val);
if (key_type >= RTE_IPSEC_SAD_SPI_DIP) /* DIP is optional*/
    key.v4.dip = rte_cpu_to_be_32(dip_val);
if (key_type == RTE_IPSEC_SAD_SPI_DIP_SIP) /* SIP is optional*/
    key.v4.sip = rte_cpu_to_be_32(sip_val);

rte_ipsec_sad_add(sad, &key, key_type, sa);

Note

By performance reason it is better to keep spi/dip/sip in net byte order to eliminate byteswap on lookup

To delete user has to specify key and key type.

Delete code would look like:

union rte_ipsec_sad_key key;

key.v4.spi = rte_cpu_to_be_32(necessary_spi);
if (key_type >= RTE_IPSEC_SAD_SPI_DIP) /* DIP is optional*/
    key.v4.dip = rte_cpu_to_be_32(necessary_dip);
if (key_type == RTE_IPSEC_SAD_SPI_DIP_SIP) /* SIP is optional*/
    key.v4.sip = rte_cpu_to_be_32(necessary_sip);

rte_ipsec_sad_del(sad, &key, key_type);

2.2.3. Lookup

Library provides lookup by the given {SPI,DIP,SIP} tuple of inbound ipsec packet as a key.

The search key is represented by:

union rte_ipsec_sad_key {
    struct rte_ipsec_sadv4_key  v4;
    struct rte_ipsec_sadv6_key  v6;
};

where v4 is a tuple for IPv4:

struct rte_ipsec_sadv4_key {
    uint32_t spi;
    uint32_t dip;
    uint32_t sip;
};

and v6 is a tuple for IPv6:

struct rte_ipsec_sadv6_key {
    uint32_t spi;
    struct rte_ipv6_addr dip;
    struct rte_ipv6_addr sip;
};

As an example, lookup related code could look like that:

int i;
union rte_ipsec_sad_key keys[BURST_SZ];
const union rte_ipsec_sad_key *keys_p[BURST_SZ];
void *vals[BURST_SZ];

for (i = 0; i < BURST_SZ_MAX; i++) {
    keys[i].v4.spi = esp_hdr[i]->spi;
    keys[i].v4.dip = ipv4_hdr[i]->dst_addr;
    keys[i].v4.sip = ipv4_hdr[i]->src_addr;
    keys_p[i] = &keys[i];
}
rte_ipsec_sad_lookup(sad, keys_p, vals, BURST_SZ);

for (i = 0; i < BURST_SZ_MAX; i++) {
    if (vals[i] == NULL)
        printf("SA not found for key index %d\n", i);
    else
        printf("SA pointer is %p\n", vals[i]);
}

2.3. Supported features

ESP protocol tunnel mode both IPv4/IPv6.
ESP protocol transport mode both IPv4/IPv6.
ESN and replay window.
NAT-T / UDP encapsulated ESP.
TSO (only for inline crypto mode)
algorithms: 3DES-CBC, AES-CBC, AES-CTR, AES-GCM, AES_CCM, CHACHA20_POLY1305, AES_GMAC, HMAC-SHA1, NULL.

2.4. Telemetry support

Telemetry support implements SA details and IPsec packet add data counters statistics. Per SA telemetry statistics can be enabled using rte_ipsec_telemetry_sa_add and disabled using rte_ipsec_telemetry_sa_del. Note that these calls are not thread safe.

2.5. Stateless IPsec packet processing

Support for stateless IPsec packet processing allows use of custom sequence number to be used for IPsec outbound processing.

rte_ipsec_pkt_stateless_prepare() takes as input the state parameter from the application and prepares the packet for IPsec processing.

2.6. Limitations

The following features are not properly supported in the current version:

Hard/soft limit for SA lifetime (time interval/byte count).