DOKK / manpages / debian 13 / dpdk-doc / rte_mbuf_dynfield_lookup.3.en
rte_mbuf_dyn.h(3) Library Functions Manual rte_mbuf_dyn.h(3)

rte_mbuf_dyn.h

#include <stdio.h>
#include <stdint.h>


struct rte_mbuf_dynfield
struct rte_mbuf_dynflag


#define RTE_MBUF_DYN_NAMESIZE 64
#define RTE_MBUF_DYNFIELD(m, offset, type) ((type)((uintptr_t)(m) + (offset)))
#define RTE_MBUF_DYNFIELD_TIMESTAMP_NAME 'rte_dynfield_timestamp'
#define RTE_MBUF_DYNFLAG_RX_TIMESTAMP_NAME 'rte_dynflag_rx_timestamp'
#define RTE_MBUF_DYNFLAG_TX_TIMESTAMP_NAME 'rte_dynflag_tx_timestamp'
#define RTE_MBUF_DYNFIELD_IP_REASSEMBLY_NAME 'rte_dynfield_ip_reassembly'


int rte_mbuf_dynfield_register (const struct rte_mbuf_dynfield *params)
int rte_mbuf_dynfield_register_offset (const struct rte_mbuf_dynfield *params, size_t offset)
int rte_mbuf_dynfield_lookup (const char *name, struct rte_mbuf_dynfield *params)
int rte_mbuf_dynflag_register (const struct rte_mbuf_dynflag *params)
int rte_mbuf_dynflag_register_bitnum (const struct rte_mbuf_dynflag *params, unsigned int bitnum)
int rte_mbuf_dynflag_lookup (const char *name, struct rte_mbuf_dynflag *params)
void rte_mbuf_dyn_dump (FILE *out)
int rte_mbuf_dyn_rx_timestamp_register (int *field_offset, uint64_t *rx_flag)
int rte_mbuf_dyn_tx_timestamp_register (int *field_offset, uint64_t *tx_flag)

RTE Mbuf dynamic fields and flags

Many DPDK features require to store data inside the mbuf. As the room in mbuf structure is limited, it is not possible to have a field for each feature. Also, changing fields in the mbuf structure can break the API or ABI.

This module addresses this issue, by enabling the dynamic registration of fields or flags:

  • a dynamic field is a named area in the rte_mbuf structure, with a given size (>= 1 byte) and alignment constraint.
  • a dynamic flag is a named bit in the rte_mbuf structure, stored in mbuf->ol_flags.

The placement of the field or flag can be automatic, in this case the zones that have the smallest size and alignment constraint are selected in priority. Else, a specific field offset or flag bit number can be requested through the API.

The typical use case is when a specific offload feature requires to register a dedicated offload field in the mbuf structure, and adding a static field or flag is not justified.

Example of use:

  • A rte_mbuf_dynfield structure is defined, containing the parameters of the dynamic field to be registered: const struct rte_mbuf_dynfield rte_dynfield_my_feature = { ... };
  • The application initializes the PMD, and asks for this feature at port initialization by passing RTE_ETH_RX_OFFLOAD_MY_FEATURE in rxconf. This will make the PMD to register the field by calling rte_mbuf_dynfield_register(&rte_dynfield_my_feature). The PMD stores the returned offset.
  • The application that uses the offload feature also registers the field to retrieve the same offset.
  • When the PMD receives a packet, it can set the field: *RTE_MBUF_DYNFIELD(m, offset, <type *>) = value;
  • In the main loop, the application can retrieve the value with the same macro.

To avoid wasting space, the dynamic fields or flags must only be reserved on demand, when an application asks for the related feature.

The registration can be done at any moment, but it is not possible to unregister fields or flags for now.

A dynamic field can be reserved and used by an application only. It can for instance be a packet mark.

To avoid namespace collisions, the dynamic mbuf field or flag names have to be chosen with care. It is advised to use the same conventions than function names in dpdk:

  • any name that does not start with 'rte_' in an application

Definition in file rte_mbuf_dyn.h.

Maximum length of the dynamic field or flag string.

Definition at line 80 of file rte_mbuf_dyn.h.

Helper macro to access to a dynamic field.

Definition at line 227 of file rte_mbuf_dyn.h.

The timestamp dynamic field provides some timing information, the units and time references (initial phase) are not explicitly defined but are maintained always the same for a given port. Some devices allow to query rte_eth_read_clock() that will return the current device timestamp. The dynamic Tx timestamp flag tells whether the field contains actual timestamp value for the packets being sent, this value can be used by PMD to schedule packet sending.

Definition at line 262 of file rte_mbuf_dyn.h.

Indicate that the timestamp field in the mbuf was filled by the driver.

Definition at line 268 of file rte_mbuf_dyn.h.

When PMD sees the RTE_MBUF_DYNFLAG_TX_TIMESTAMP_NAME flag set on the packet being sent it tries to synchronize the time of packet appearing on the wire with the specified packet timestamp. If the specified one is in the past it should be ignored, if one is in the distant future it should be capped with some reasonable value (in range of seconds).

There is no any packet reordering according to timestamps is supposed, neither for packet within the burst, nor for the whole bursts, it is an entirely application responsibility to generate packets and its timestamps in desired order. The timestamps might be put only in the first packet in the burst providing the entire burst scheduling.

Definition at line 301 of file rte_mbuf_dyn.h.

For the PMDs which support IP reassembly of packets, PMD will update the packet with RTE_MBUF_DYNFLAG_IP_REASSEMBLY_INCOMPLETE_NAME to denote that IP reassembly is incomplete and application can retrieve the packets back using RTE_MBUF_DYNFIELD_IP_REASSEMBLY_NAME.

Definition at line 327 of file rte_mbuf_dyn.h.

Register space for a dynamic field in the mbuf structure.

If the field is already registered (same name and parameters), its offset is returned.

Parameters

params A structure containing the requested parameters (name, size, alignment constraint and flags).

Returns

The offset in the mbuf structure, or -1 on error. Possible values for rte_errno:
  • EINVAL: invalid parameters (size, align, or flags).
  • EEXIST: this name is already register with different parameters.
  • EPERM: called from a secondary process.
  • ENOENT: not enough room in mbuf.
  • ENOMEM: allocation failure.
  • ENAMETOOLONG: name does not ends with \0.

Register space for a dynamic field in the mbuf structure at offset.

If the field is already registered (same name, parameters and offset), the offset is returned.

Parameters

params A structure containing the requested parameters (name, size, alignment constraint and flags).
offset The requested offset. Ignored if SIZE_MAX is passed.

Returns

The offset in the mbuf structure, or -1 on error. Possible values for rte_errno:
  • EINVAL: invalid parameters (size, align, flags, or offset).
  • EEXIST: this name is already register with different parameters.
  • EBUSY: the requested offset cannot be used.
  • EPERM: called from a secondary process.
  • ENOENT: not enough room in mbuf.
  • ENOMEM: allocation failure.
  • ENAMETOOLONG: name does not ends with \0.

Lookup for a registered dynamic mbuf field.

Parameters

name A string identifying the dynamic field.
params If not NULL, and if the lookup is successful, the structure is filled with the parameters of the dynamic field.

Returns

The offset of this field in the mbuf structure, or -1 on error. Possible values for rte_errno:
•
ENOENT: no dynamic field matches this name.

Register a dynamic flag in the mbuf structure.

If the flag is already registered (same name and parameters), its bitnum is returned.

Parameters

params A structure containing the requested parameters of the dynamic flag (name and options).

Returns

The number of the reserved bit, or -1 on error. Possible values for rte_errno:
  • EINVAL: invalid parameters (size, align, or flags).
  • EEXIST: this name is already register with different parameters.
  • EPERM: called from a secondary process.
  • ENOENT: no more flag available.
  • ENOMEM: allocation failure.
  • ENAMETOOLONG: name is longer than RTE_MBUF_DYN_NAMESIZE - 1.

Register a dynamic flag in the mbuf structure specifying bitnum.

If the flag is already registered (same name, parameters and bitnum), the bitnum is returned.

Parameters

params A structure containing the requested parameters of the dynamic flag (name and options).
bitnum The requested bitnum. Ignored if UINT_MAX is passed.

Returns

The number of the reserved bit, or -1 on error. Possible values for rte_errno:
  • EINVAL: invalid parameters (size, align, or flags).
  • EEXIST: this name is already register with different parameters.
  • EBUSY: the requested bitnum cannot be used.
  • EPERM: called from a secondary process.
  • ENOENT: no more flag available.
  • ENOMEM: allocation failure.
  • ENAMETOOLONG: name is longer than RTE_MBUF_DYN_NAMESIZE - 1.

Lookup for a registered dynamic mbuf flag.

Parameters

name A string identifying the dynamic flag.
params If not NULL, and if the lookup is successful, the structure is filled with the parameters of the dynamic flag.

Returns

The offset of this flag in the mbuf structure, or -1 on error. Possible values for rte_errno:
•
ENOENT: no dynamic flag matches this name.

Dump the status of dynamic fields and flags.

Parameters

out The stream where the status is displayed.

Register dynamic mbuf field and flag for Rx timestamp.

Parameters

field_offset Pointer to the offset of the registered mbuf field, can be NULL. The same field is shared for Rx and Tx timestamp.
rx_flag Pointer to the mask of the registered offload flag, can be NULL.

Returns

0 on success, -1 otherwise. Possible values for rte_errno:
  • EEXIST: already registered with different parameters.
  • EPERM: called from a secondary process.
  • ENOENT: no more field or flag available.
  • ENOMEM: allocation failure.

Register dynamic mbuf field and flag for Tx timestamp.

Parameters

field_offset Pointer to the offset of the registered mbuf field, can be NULL. The same field is shared for Rx and Tx timestamp.
tx_flag Pointer to the mask of the registered offload flag, can be NULL.

Returns

0 on success, -1 otherwise. Possible values for rte_errno:
  • EEXIST: already registered with different parameters.
  • EPERM: called from a secondary process.
  • ENOENT: no more field or flag available.
  • ENOMEM: allocation failure.

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