This RFC contains a proposal to add a new packet type query API to DPDK.
Motivation
==========
In current DPDK implementation, when received one packet, driver will lookup
the packet type mapping table and transmit the result value to struct mbuf.
Appilcation will analyze the mbuf->packet_type only when user want to show the
packet type name. It will waste a lot of cycles, because sometimes user don't
care what the packet type is, but the look-up will always exist. We think the
packet type name is not needed all the time and the look-up is not needed
neither. So we will add a flag, when enable the flag, the ptype value in
descriptor will be passed through to mbuf->packet_type directly. So a new API
to get packet name by values is added also, it will be called when user want to
know what the packet type name is. So we can use the flag to control which
value will transmit to mbuf(direct ptype value or ptype name value).
The current ptype expression depend on bit width(max 32 bit, used 28bit
already), if we support more packet type in future, like next generation NIC
support flexible pipeline, it will introduce some new packet types, the
remaining bit may not enough. So I suppose to use the rte_flow items to present
packet type. The advantage of rte_flow item are:
1. It's generic enough, every NIC can use these items to present their packet;
2. it's flexible, can add new items unlimited to support new packet type.
Proposed solution
================
The new API used to query the exact packet type name with packet type value
from descriptor.
/** Packet type name structure */
struct rte_eth_ptype_name {
uint64_t ptype_value;
enum *name;
}
/**
* Query the exact packet type name with packet type values
*
* @param port_id Port identifier of Ethernet device.
* @param names Pointer to packet type name buffer.
* @param size The size of ptype_values array (number of element).
* @param ptype_values Pointer to a table of ptype values.
* @return
* - On success returns zero
* - On failure returns non-zero
*/
int rte_eth_ptype_name_get_by_value (uint8_t port_id, struct rte_eth_ptype_name
*names, int size, uint64_t *ptype_values);
Add a new flag 'enable_ptype_direct' in structure rte_eth_rxmode to enable
packet type get direct mode. The direct mode means the packet type value will
pass through directly from HW to driver without lookup ptype mapping table.
User can call function rte_eth_ptype_name_get_by_value to query what the
packet type value means when they need.
struct rte_eth_rxmode {
??? ???
uint16_t header_split : 1, /**< Header Split enable. */
hw_ip_checksum : 1, /**< IP/UDP/TCP checksum offload enable.
*/
hw_vlan_filter : 1, /**< VLAN filter enable. */
hw_vlan_strip : 1, /**< VLAN strip enable. */
hw_vlan_extend : 1, /**< Extended VLAN enable. */
jumbo_frame : 1, /**< Jumbo Frame Receipt enable. */
hw_strip_crc : 1, /**< Enable CRC stripping by hardware. */
enable_scatter : 1, /**< Enable scatter packets rx handler */
+ enable_ptype_direct :1, /** < Enable packet type get direct
mode. */
enable_lro : 1; /**< Enable LRO */
};
This flag will be configured in dev_configure(), and can be queried by user
through dev->data->dev_conf.rxmode.enable_ptype_direct. In receive function,
driver will store HW's packet type value in mbuf->packet_type if direct mode is
enabled, If not, maintain the existing code.
Driver maintains a new ptype_value and rte_flow item mapping table, when
download a profile and support new packet type, the SW mapping table will be
updated according to the ptype information analyzed from profile.
Future work
===========
Support to configure the packet type direct mode per queue.
