Network Buffer
[Network Devices]

Collaboration diagram for Network Buffer:

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Detailed Description

Network buffer support.

The network buffer handling is designed to make life easy when it comes to handling ISO-layered communications. By this we're thinking about communications structures that are hierarchically organized.

The idea is that network buffer structures are allocated every time a new packet is either received or ready for sending. The various fields of the network buffer are then handled by matching layers within the appropriate protocol stack.

Linked list of NETBUF structures:

Data Structures
struct	_NBDATA
	Data part of a network buffer structure. More...
struct	_NETBUF
	Network buffer structure. More...
struct	_NBDATA
	Data part of a network buffer structure. More...
struct	_NETBUF
	Network buffer structure. More...
Defines
#define	NBAF_DATALINK   0x10
	Datalink buffer allocated flag.
#define	NBAF_NETWORK   0x20
	Network buffer allocated flag.
#define	NBAF_TRANSPORT   0x40
	Transport buffer allocated flag.
#define	NBAF_APPLICATION   0x80
	Application buffer allocated flag.
#define	NBAF_ALL   0xf0
	Masks allocated buffer flags flag.
Typedefs
typedef _NETBUF	NETBUF
	Network buffer type.
typedef _NBDATA	NBDATA
	Network buffer data type.
Functions
NETBUF *	NutNetBufAlloc (NETBUF *nb, u_char type, u_short size)
	Allocate or re-allocate a network buffer part.
NETBUF *	NutNetBufClone (NETBUF *nb)
	Create a copy of an existing network buffer structure.
int	NutNetBufFree (NETBUF *nb)
	Release a network buffer structure.

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Function Documentation

NETBUF* NutNetBufAlloc (  NETBUF *  nb, u_char  type, u_short  size )

Allocate or re-allocate a network buffer part. Parameters: nb  Points to an existing network buffer structure or NULL, if a new structure should be created. An existing buffer must not be used any further if this function returns a null pointer. type  Part of the buffer to be allocated. This can be any of the following: NBAF_DATALINK NBAF_NETWORK NBAF_TRANSPORT NBAF_APPLICATION size  Size of the part to be allocated. Returns: Pointer to the allocated network buffer structure. A null pointer is returned if not enough memory is available and the whole structure is released.

NETBUF* NutNetBufClone (  NETBUF *  nb  )

Create a copy of an existing network buffer structure. Parameters: nb  Points to an existing network buffer structure, previously allocated by NutNetBufAlloc(). Returns: Pointer to a newly allocated copy.

int NutNetBufFree (  NETBUF *  nb  )

Release a network buffer structure. Returns all memory previously allocated by a network buffer to the available heap space. Parameters: nb  Points to an existing network buffer structure, previously allocated by NutNetBufAlloc(). Returns: 0 if successfull or -1 if the structure contains previously released memory space.

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