rte_mbuf_dyn.h File Reference

#include <sys/types.h>

Go to the source code of this file.

Data Structures
struct	rte_mbuf_dynfield
struct	rte_mbuf_dynflag

Macros
#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_TX_TIMESTAMP_NAME   "rte_dynflag_tx_timestamp"

Functions
__rte_experimental int	rte_mbuf_dynfield_register (const struct rte_mbuf_dynfield *params)
__rte_experimental int	rte_mbuf_dynfield_register_offset (const struct rte_mbuf_dynfield *params, size_t offset)
__rte_experimental int	rte_mbuf_dynfield_lookup (const char *name, struct rte_mbuf_dynfield *params)
__rte_experimental int	rte_mbuf_dynflag_register (const struct rte_mbuf_dynflag *params)
__rte_experimental int	rte_mbuf_dynflag_register_bitnum (const struct rte_mbuf_dynflag *params, unsigned int bitnum)
__rte_experimental int	rte_mbuf_dynflag_lookup (const char *name, struct rte_mbuf_dynflag *params)
__rte_experimental void	rte_mbuf_dyn_dump (FILE *out)

Detailed Description

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 DEV_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:

• "rte_mbuf_dynfield_<name>" if defined in mbuf library
• "rte_<libname>_dynfield_<name>" if defined in another library
• "rte_net_<pmd>_dynfield_<name>" if defined in a in PMD
• any name that does not start with "rte_" in an application

Definition in file rte_mbuf_dyn.h.

Macro Definition Documentation

#define RTE_MBUF_DYN_NAMESIZE   64

Maximum length of the dynamic field or flag string.

Definition at line 73 of file rte_mbuf_dyn.h.

#define RTE_MBUF_DYNFIELD	(		m,
			offset,
			type
	)		((type)((uintptr_t)(m) + (offset)))

Helper macro to access to a dynamic field.

Definition at line 226 of file rte_mbuf_dyn.h.

#define RTE_MBUF_DYNFIELD_TIMESTAMP_NAME   "rte_dynfield_timestamp"

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.

After PKT_RX_TIMESTAMP flag and fixed timestamp field deprecation and obsoleting, the dedicated Rx timestamp flag is supposed to be introduced and the shared dynamic timestamp field will be used to handle the timestamps on receiving datapath as well.

Definition at line 267 of file rte_mbuf_dyn.h.

#define RTE_MBUF_DYNFLAG_TX_TIMESTAMP_NAME   "rte_dynflag_tx_timestamp"

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 282 of file rte_mbuf_dyn.h.

Function Documentation

__rte_experimental int rte_mbuf_dynfield_register

(

const struct rte_mbuf_dynfield *

params

)

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.

__rte_experimental int rte_mbuf_dynfield_register_offset	(	const struct rte_mbuf_dynfield *	params,
		size_t	offset
	)

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.

__rte_experimental int rte_mbuf_dynfield_lookup	(	const char *	name,
		struct rte_mbuf_dynfield *	params
	)

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.

__rte_experimental int rte_mbuf_dynflag_register

(

const struct rte_mbuf_dynflag *

params

)

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.

__rte_experimental int rte_mbuf_dynflag_register_bitnum	(	const struct rte_mbuf_dynflag *	params,
		unsigned int	bitnum
	)

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.

__rte_experimental int rte_mbuf_dynflag_lookup	(	const char *	name,
		struct rte_mbuf_dynflag *	params
	)

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.

__rte_experimental void rte_mbuf_dyn_dump

(

FILE *

out

)

Dump the status of dynamic fields and flags.

Parameters

out	The stream where the status is displayed.