Network Buffer

Overview

Network buffers are a core concept of how the networking stack (as well as the Bluetooth stack) pass data around. The API for them is defined in include/net/buf.h:.

Creating buffers

Network buffers are created by first defining a pool of them:

NET_BUF_POOL_DEFINE(pool_name, buf_count, buf_size, user_data_size, NULL);

The pool is a static variable, so if it’s needed to be exported to another module a separate pointer is needed.

Once the pool has been defined, buffers can be allocated from it with:

buf = net_buf_alloc(&pool_name, timeout);

There is no explicit initialization function for the pool or its buffers, rather this is done implicitly as net_buf_alloc() gets called.

If there is a need to reserve space in the buffer for protocol headers to be prepended later, it’s possible to reserve this headroom with:

net_buf_reserve(buf, headroom);

In addition to actual protocol data and generic parsing context, network buffers may also contain protocol-specific context, known as user data. Both the maximum data and user data capacity of the buffers is compile-time defined when declaring the buffer pool.

The buffers have native support for being passed through k_fifo kernel objects. This is a very practical feature when the buffers need to be passed from one thread to another. However, since a net_buf may have a fragment chain attached to it, instead of using the k_fifo_put() and k_fifo_get() APIs, special net_buf_put() and net_buf_get() APIs must be used when passing buffers through FIFOs. These APIs ensure that the buffer chains stay intact. The same applies for passing buffers through a singly linked list, in which case the net_buf_slist_put() and net_buf_slist_get() functions must be used instead of sys_slist_append() and sys_slist_get().

Common Operations

The network buffer API provides some useful helpers for encoding and decoding data in the buffers. To fully understand these helpers it’s good to understand the basic names of operations used with them:

Add

Add data to the end of the buffer. Modifies the data length value while leaving the actual data pointer intact. Requires that there is enough tailroom in the buffer. Some examples of APIs for adding data:

void *net_buf_add(struct net_buf *buf, size_t len);
void *net_buf_add_mem(struct net_buf *buf, const void *mem, size_t len);
u8_t *net_buf_add_u8(struct net_buf *buf, u8_t value);
void net_buf_add_le16(struct net_buf *buf, u16_t value);
void net_buf_add_le32(struct net_buf *buf, u32_t value);
Push

Prepend data to the beginning of the buffer. Modifies both the data length value as well as the data pointer. Requires that there is enough headroom in the buffer. Some examples of APIs for pushing data:

void *net_buf_push(struct net_buf *buf, size_t len);
void net_buf_push_u8(struct net_buf *buf, u8_t value);
void net_buf_push_le16(struct net_buf *buf, u16_t value);
Pull

Remove data from the beginning of the buffer. Modifies both the data length value as well as the data pointer. Some examples of APIs for pulling data:

void *net_buf_pull(struct net_buf *buf, size_t len);
void *net_buf_pull_mem(struct net_buf *buf, size_t len);
u8_t net_buf_pull_u8(struct net_buf *buf);
u16_t net_buf_pull_le16(struct net_buf *buf);
u32_t net_buf_pull_le32(struct net_buf *buf);

The Add and Push operations are used when encoding data into the buffer, whereas Pull is used when decoding data from a buffer.

Reference Counting

Each network buffer is reference counted. The buffer is initially acquired from a free buffers pool by calling net_buf_alloc(), resulting in a buffer with reference count 1. The reference count can be incremented with net_buf_ref() or decremented with net_buf_unref(). When the count drops to zero the buffer is automatically placed back to the free buffers pool.

API Reference

group net_buf

Network buffer library.

Defines

NET_BUF_SIMPLE_DEFINE(_name, _size)

Define a net_buf_simple stack variable.

This is a helper macro which is used to define a net_buf_simple object on the stack.

Parameters
  • _name: Name of the net_buf_simple object.
  • _size: Maximum data storage for the buffer.

NET_BUF_SIMPLE_DEFINE_STATIC(_name, _size)

Define a static net_buf_simple variable.

This is a helper macro which is used to define a static net_buf_simple object.

Parameters
  • _name: Name of the net_buf_simple object.
  • _size: Maximum data storage for the buffer.

NET_BUF_SIMPLE(_size)

Define a net_buf_simple stack variable and get a pointer to it.

This is a helper macro which is used to define a net_buf_simple object on the stack and the get a pointer to it as follows:

struct net_buf_simple *my_buf = NET_BUF_SIMPLE(10);

After creating the object it needs to be initialized by calling net_buf_simple_init().

Return
Pointer to stack-allocated net_buf_simple object.
Parameters
  • _size: Maximum data storage for the buffer.

NET_BUF_FRAGS

Flag indicating that the buffer has associated fragments. Only used internally by the buffer handling code while the buffer is inside a FIFO, meaning this never needs to be explicitly set or unset by the net_buf API user. As long as the buffer is outside of a FIFO, i.e. in practice always for the user for this API, the buf->frags pointer should be used instead.

NET_BUF_EXTERNAL_DATA

Flag indicating that the buffer’s associated data pointer, points to externally allocated memory. Therefore once ref goes down to zero, the pointed data will not need to be deallocated. This never needs to be explicitly set or unet by the net_buf API user. Such net_buf is exclusively instantiated via net_buf_alloc_with_data() function. Reference count mechanism however will behave the same way, and ref count going to 0 will free the net_buf but no the data pointer in it.

NET_BUF_POOL_HEAP_DEFINE(_name, _count, _destroy)

Define a new pool for buffers using the heap for the data.

Defines a net_buf_pool struct and the necessary memory storage (array of structs) for the needed amount of buffers. After this, the buffers can be accessed from the pool through net_buf_alloc. The pool is defined as a static variable, so if it needs to be exported outside the current module this needs to happen with the help of a separate pointer rather than an extern declaration.

The data payload of the buffers will be allocated from the heap using k_malloc, so CONFIG_HEAP_MEM_POOL_SIZE must be set to a positive value. This kind of pool does not support blocking on the data allocation, so the timeout passed to net_buf_alloc will be always treated as K_NO_WAIT when trying to allocate the data. This means that allocation failures, i.e. NULL returns, must always be handled cleanly.

If provided with a custom destroy callback, this callback is responsible for eventually calling net_buf_destroy() to complete the process of returning the buffer to the pool.

Parameters
  • _name: Name of the pool variable.
  • _count: Number of buffers in the pool.
  • _destroy: Optional destroy callback when buffer is freed.

NET_BUF_POOL_FIXED_DEFINE(_name, _count, _data_size, _destroy)

Define a new pool for buffers based on fixed-size data.

Defines a net_buf_pool struct and the necessary memory storage (array of structs) for the needed amount of buffers. After this, the buffers can be accessed from the pool through net_buf_alloc. The pool is defined as a static variable, so if it needs to be exported outside the current module this needs to happen with the help of a separate pointer rather than an extern declaration.

The data payload of the buffers will be allocated from a byte array of fixed sized chunks. This kind of pool does not support blocking on the data allocation, so the timeout passed to net_buf_alloc will be always treated as K_NO_WAIT when trying to allocate the data. This means that allocation failures, i.e. NULL returns, must always be handled cleanly.

If provided with a custom destroy callback, this callback is responsible for eventually calling net_buf_destroy() to complete the process of returning the buffer to the pool.

Parameters
  • _name: Name of the pool variable.
  • _count: Number of buffers in the pool.
  • _data_size: Maximum data payload per buffer.
  • _destroy: Optional destroy callback when buffer is freed.

NET_BUF_POOL_VAR_DEFINE(_name, _count, _data_size, _destroy)

Define a new pool for buffers with variable size payloads.

Defines a net_buf_pool struct and the necessary memory storage (array of structs) for the needed amount of buffers. After this, the buffers can be accessed from the pool through net_buf_alloc. The pool is defined as a static variable, so if it needs to be exported outside the current module this needs to happen with the help of a separate pointer rather than an extern declaration.

The data payload of the buffers will be based on a memory pool from which variable size payloads may be allocated.

If provided with a custom destroy callback, this callback is responsible for eventually calling net_buf_destroy() to complete the process of returning the buffer to the pool.

Parameters
  • _name: Name of the pool variable.
  • _count: Number of buffers in the pool.
  • _data_size: Total amount of memory available for data payloads.
  • _destroy: Optional destroy callback when buffer is freed.

NET_BUF_POOL_DEFINE(_name, _count, _size, _ud_size, _destroy)

Define a new pool for buffers.

Defines a net_buf_pool struct and the necessary memory storage (array of structs) for the needed amount of buffers. After this,the buffers can be accessed from the pool through net_buf_alloc. The pool is defined as a static variable, so if it needs to be exported outside the current module this needs to happen with the help of a separate pointer rather than an extern declaration.

If provided with a custom destroy callback this callback is responsible for eventually calling net_buf_destroy() to complete the process of returning the buffer to the pool.

Parameters
  • _name: Name of the pool variable.
  • _count: Number of buffers in the pool.
  • _size: Maximum data size for each buffer.
  • _ud_size: Amount of user data space to reserve.
  • _destroy: Optional destroy callback when buffer is freed.

net_buf_alloc(pool, timeout)

Return
New buffer or NULL if out of buffers.
Parameters
  • pool: Which pool to allocate the buffer from.
  • timeout: Affects the action taken should the pool be empty. If K_NO_WAIT, then return immediately. If K_FOREVER, then wait as long as necessary. Otherwise, wait up to the specified number of milliseconds before timing out. Note that some types of data allocators do not support blocking (such as the HEAP type). In this case it’s still possible for net_buf_alloc() to fail (return NULL) even if it was given K_FOREVER.

net_buf_reserve(buf, reserve)

Initialize buffer with the given headroom.

The buffer is not expected to contain any data when this API is called.

Parameters
  • buf: Buffer to initialize.
  • reserve: How much headroom to reserve.

net_buf_add(buf, len)

Prepare data to be added at the end of the buffer.

Increments the data length of a buffer to account for more data at the end.

Return
The original tail of the buffer.
Parameters
  • buf: Buffer to update.
  • len: Number of bytes to increment the length with.

net_buf_add_mem(buf, mem, len)

Copies the given number of bytes to the end of the buffer.

Increments the data length of the buffer to account for more data at the end.

Return
The original tail of the buffer.
Parameters
  • buf: Buffer to update.
  • mem: Location of data to be added.
  • len: Length of data to be added

net_buf_add_u8(buf, val)

Add (8-bit) byte at the end of the buffer.

Increments the data length of the buffer to account for more data at the end.

Return
Pointer to the value added
Parameters
  • buf: Buffer to update.
  • val: byte value to be added.

net_buf_add_le16(buf, val)

Add 16-bit value at the end of the buffer.

Adds 16-bit value in little endian format at the end of buffer. Increments the data length of a buffer to account for more data at the end.

Parameters
  • buf: Buffer to update.
  • val: 16-bit value to be added.

net_buf_add_be16(buf, val)

Add 16-bit value at the end of the buffer.

Adds 16-bit value in big endian format at the end of buffer. Increments the data length of a buffer to account for more data at the end.

Parameters
  • buf: Buffer to update.
  • val: 16-bit value to be added.

net_buf_add_le32(buf, val)

Add 32-bit value at the end of the buffer.

Adds 32-bit value in little endian format at the end of buffer. Increments the data length of a buffer to account for more data at the end.

Parameters
  • buf: Buffer to update.
  • val: 32-bit value to be added.

net_buf_add_be32(buf, val)

Add 32-bit value at the end of the buffer.

Adds 32-bit value in big endian format at the end of buffer. Increments the data length of a buffer to account for more data at the end.

Parameters
  • buf: Buffer to update.
  • val: 32-bit value to be added.

net_buf_push(buf, len)

Push data to the beginning of the buffer.

Modifies the data pointer and buffer length to account for more data in the beginning of the buffer.

Return
The new beginning of the buffer data.
Parameters
  • buf: Buffer to update.
  • len: Number of bytes to add to the beginning.

net_buf_push_le16(buf, val)

Push 16-bit value to the beginning of the buffer.

Adds 16-bit value in little endian format to the beginning of the buffer.

Parameters
  • buf: Buffer to update.
  • val: 16-bit value to be pushed to the buffer.

net_buf_push_be16(buf, val)

Push 16-bit value to the beginning of the buffer.

Adds 16-bit value in little endian format to the beginning of the buffer.

Parameters
  • buf: Buffer to update.
  • val: 16-bit value to be pushed to the buffer.

net_buf_push_u8(buf, val)

Push 8-bit value to the beginning of the buffer.

Adds 8-bit value the beginning of the buffer.

Parameters
  • buf: Buffer to update.
  • val: 8-bit value to be pushed to the buffer.

net_buf_pull(buf, len)

Remove data from the beginning of the buffer.

Removes data from the beginning of the buffer by modifying the data pointer and buffer length.

Return
New beginning of the buffer data.
Parameters
  • buf: Buffer to update.
  • len: Number of bytes to remove.

net_buf_pull_mem(buf, len)

Remove data from the beginning of the buffer.

Removes data from the beginning of the buffer by modifying the data pointer and buffer length.

Return
Pointer to the old beginning of the buffer data.
Parameters
  • buf: Buffer to update.
  • len: Number of bytes to remove.

net_buf_pull_u8(buf)

Remove a 8-bit value from the beginning of the buffer.

Same idea as with net_buf_pull(), but a helper for operating on 8-bit values.

Return
The 8-bit removed value
Parameters
  • buf: A valid pointer on a buffer.

net_buf_pull_le16(buf)

Remove and convert 16 bits from the beginning of the buffer.

Same idea as with net_buf_pull(), but a helper for operating on 16-bit little endian data.

Return
16-bit value converted from little endian to host endian.
Parameters
  • buf: A valid pointer on a buffer.

net_buf_pull_be16(buf)

Remove and convert 16 bits from the beginning of the buffer.

Same idea as with net_buf_pull(), but a helper for operating on 16-bit big endian data.

Return
16-bit value converted from big endian to host endian.
Parameters
  • buf: A valid pointer on a buffer.

net_buf_pull_le32(buf)

Remove and convert 32 bits from the beginning of the buffer.

Same idea as with net_buf_pull(), but a helper for operating on 32-bit little endian data.

Return
32-bit value converted from little endian to host endian.
Parameters
  • buf: A valid pointer on a buffer.

net_buf_pull_be32(buf)

Remove and convert 32 bits from the beginning of the buffer.

Same idea as with net_buf_pull(), but a helper for operating on 32-bit big endian data.

Return
32-bit value converted from big endian to host endian.
Parameters
  • buf: A valid pointer on a buffer

net_buf_tailroom(buf)

Check buffer tailroom.

Check how much free space there is at the end of the buffer.

Return
Number of bytes available at the end of the buffer.
Parameters
  • buf: A valid pointer on a buffer

net_buf_headroom(buf)

Check buffer headroom.

Check how much free space there is in the beginning of the buffer.

buf A valid pointer on a buffer

Return
Number of bytes available in the beginning of the buffer.

net_buf_tail(buf)

Get the tail pointer for a buffer.

Get a pointer to the end of the data in a buffer.

Return
Tail pointer for the buffer.
Parameters
  • buf: Buffer.

Typedefs

typedef net_buf_allocator_cb

Network buffer allocator callback.

The allocator callback is called when net_buf_append_bytes needs to allocate a new net_buf.

Return
pointer to allocated net_buf or NULL on error.
Parameters
  • timeout: Affects the action taken should the net buf pool be empty. If K_NO_WAIT, then return immediately. If K_FOREVER, then wait as long as necessary. Otherwise, wait up to the specified number of milliseconds before timing out.
  • user_data: The user data given in net_buf_append_bytes call.

Functions

static void net_buf_simple_init(struct net_buf_simple *buf, size_t reserve_head)

Initialize a net_buf_simple object.

This needs to be called after creating a net_buf_simple object using the NET_BUF_SIMPLE macro.

Parameters
  • buf: Buffer to initialize.
  • reserve_head: Headroom to reserve.

static void net_buf_simple_reset(struct net_buf_simple *buf)

Reset buffer.

Reset buffer data so it can be reused for other purposes.

Parameters
  • buf: Buffer to reset.

void *net_buf_simple_add(struct net_buf_simple *buf, size_t len)

Prepare data to be added at the end of the buffer.

Increments the data length of a buffer to account for more data at the end.

Return
The original tail of the buffer.
Parameters
  • buf: Buffer to update.
  • len: Number of bytes to increment the length with.

void *net_buf_simple_add_mem(struct net_buf_simple *buf, const void *mem, size_t len)

Copy given number of bytes from memory to the end of the buffer.

Increments the data length of the buffer to account for more data at the end.

Return
The original tail of the buffer.
Parameters
  • buf: Buffer to update.
  • mem: Location of data to be added.
  • len: Length of data to be added

u8_t *net_buf_simple_add_u8(struct net_buf_simple *buf, u8_t val)

Add (8-bit) byte at the end of the buffer.

Increments the data length of the buffer to account for more data at the end.

Return
Pointer to the value added
Parameters
  • buf: Buffer to update.
  • val: byte value to be added.

void net_buf_simple_add_le16(struct net_buf_simple *buf, u16_t val)

Add 16-bit value at the end of the buffer.

Adds 16-bit value in little endian format at the end of buffer. Increments the data length of a buffer to account for more data at the end.

Parameters
  • buf: Buffer to update.
  • val: 16-bit value to be added.

void net_buf_simple_add_be16(struct net_buf_simple *buf, u16_t val)

Add 16-bit value at the end of the buffer.

Adds 16-bit value in big endian format at the end of buffer. Increments the data length of a buffer to account for more data at the end.

Parameters
  • buf: Buffer to update.
  • val: 16-bit value to be added.

void net_buf_simple_add_le32(struct net_buf_simple *buf, u32_t val)

Add 32-bit value at the end of the buffer.

Adds 32-bit value in little endian format at the end of buffer. Increments the data length of a buffer to account for more data at the end.

Parameters
  • buf: Buffer to update.
  • val: 32-bit value to be added.

void net_buf_simple_add_be32(struct net_buf_simple *buf, u32_t val)

Add 32-bit value at the end of the buffer.

Adds 32-bit value in big endian format at the end of buffer. Increments the data length of a buffer to account for more data at the end.

Parameters
  • buf: Buffer to update.
  • val: 32-bit value to be added.

void *net_buf_simple_push(struct net_buf_simple *buf, size_t len)

Push data to the beginning of the buffer.

Modifies the data pointer and buffer length to account for more data in the beginning of the buffer.

Return
The new beginning of the buffer data.
Parameters
  • buf: Buffer to update.
  • len: Number of bytes to add to the beginning.

void net_buf_simple_push_le16(struct net_buf_simple *buf, u16_t val)

Push 16-bit value to the beginning of the buffer.

Adds 16-bit value in little endian format to the beginning of the buffer.

Parameters
  • buf: Buffer to update.
  • val: 16-bit value to be pushed to the buffer.

void net_buf_simple_push_be16(struct net_buf_simple *buf, u16_t val)

Push 16-bit value to the beginning of the buffer.

Adds 16-bit value in big endian format to the beginning of the buffer.

Parameters
  • buf: Buffer to update.
  • val: 16-bit value to be pushed to the buffer.

void net_buf_simple_push_u8(struct net_buf_simple *buf, u8_t val)

Push 8-bit value to the beginning of the buffer.

Adds 8-bit value the beginning of the buffer.

Parameters
  • buf: Buffer to update.
  • val: 8-bit value to be pushed to the buffer.

void *net_buf_simple_pull(struct net_buf_simple *buf, size_t len)

Remove data from the beginning of the buffer.

Removes data from the beginning of the buffer by modifying the data pointer and buffer length.

Return
New beginning of the buffer data.
Parameters
  • buf: Buffer to update.
  • len: Number of bytes to remove.

void *net_buf_simple_pull_mem(struct net_buf_simple *buf, size_t len)

Remove data from the beginning of the buffer.

Removes data from the beginning of the buffer by modifying the data pointer and buffer length.

Return
Pointer to the old location of the buffer data.
Parameters
  • buf: Buffer to update.
  • len: Number of bytes to remove.

u8_t net_buf_simple_pull_u8(struct net_buf_simple *buf)

Remove a 8-bit value from the beginning of the buffer.

Same idea as with net_buf_simple_pull(), but a helper for operating on 8-bit values.

Return
The 8-bit removed value
Parameters
  • buf: A valid pointer on a buffer.

u16_t net_buf_simple_pull_le16(struct net_buf_simple *buf)

Remove and convert 16 bits from the beginning of the buffer.

Same idea as with net_buf_simple_pull(), but a helper for operating on 16-bit little endian data.

Return
16-bit value converted from little endian to host endian.
Parameters
  • buf: A valid pointer on a buffer.

u16_t net_buf_simple_pull_be16(struct net_buf_simple *buf)

Remove and convert 16 bits from the beginning of the buffer.

Same idea as with net_buf_simple_pull(), but a helper for operating on 16-bit big endian data.

Return
16-bit value converted from big endian to host endian.
Parameters
  • buf: A valid pointer on a buffer.

u32_t net_buf_simple_pull_le32(struct net_buf_simple *buf)

Remove and convert 32 bits from the beginning of the buffer.

Same idea as with net_buf_simple_pull(), but a helper for operating on 32-bit little endian data.

Return
32-bit value converted from little endian to host endian.
Parameters
  • buf: A valid pointer on a buffer.

u32_t net_buf_simple_pull_be32(struct net_buf_simple *buf)

Remove and convert 32 bits from the beginning of the buffer.

Same idea as with net_buf_simple_pull(), but a helper for operating on 32-bit big endian data.

Return
32-bit value converted from big endian to host endian.
Parameters
  • buf: A valid pointer on a buffer.

static u8_t *net_buf_simple_tail(struct net_buf_simple *buf)

Get the tail pointer for a buffer.

Get a pointer to the end of the data in a buffer.

Return
Tail pointer for the buffer.
Parameters
  • buf: Buffer.

size_t net_buf_simple_headroom(struct net_buf_simple *buf)

Check buffer headroom.

Check how much free space there is in the beginning of the buffer.

buf A valid pointer on a buffer

Return
Number of bytes available in the beginning of the buffer.

size_t net_buf_simple_tailroom(struct net_buf_simple *buf)

Check buffer tailroom.

Check how much free space there is at the end of the buffer.

Return
Number of bytes available at the end of the buffer.
Parameters
  • buf: A valid pointer on a buffer

static void net_buf_simple_save(struct net_buf_simple *buf, struct net_buf_simple_state *state)

Save the parsing state of a buffer.

Saves the parsing state of a buffer so it can be restored later.

Parameters
  • buf: Buffer from which the state should be saved.
  • state: Storage for the state.

static void net_buf_simple_restore(struct net_buf_simple *buf, struct net_buf_simple_state *state)

Restore the parsing state of a buffer.

Restores the parsing state of a buffer from a state previously stored by net_buf_simple_save().

Parameters
  • buf: Buffer to which the state should be restored.
  • state: Stored state.

struct net_buf_pool *net_buf_pool_get(int id)

Looks up a pool based on its ID.

Return
Pointer to pool.
Parameters
  • id: Pool ID (e.g. from buf->pool_id).

int net_buf_id(struct net_buf *buf)

Get a zero-based index for a buffer.

This function will translate a buffer into a zero-based index, based on its placement in its buffer pool. This can be useful if you want to associate an external array of meta-data contexts with the buffers of a pool.

Return
Zero-based index for the buffer.
Parameters
  • buf: Network buffer.

struct net_buf *net_buf_alloc_fixed(struct net_buf_pool *pool, s32_t timeout)

Allocate a new fixed buffer from a pool.

Return
New buffer or NULL if out of buffers.
Parameters
  • pool: Which pool to allocate the buffer from.
  • timeout: Affects the action taken should the pool be empty. If K_NO_WAIT, then return immediately. If K_FOREVER, then wait as long as necessary. Otherwise, wait up to the specified number of milliseconds before timing out. Note that some types of data allocators do not support blocking (such as the HEAP type). In this case it’s still possible for net_buf_alloc() to fail (return NULL) even if it was given K_FOREVER.

struct net_buf *net_buf_alloc_len(struct net_buf_pool *pool, size_t size, s32_t timeout)

Allocate a new variable length buffer from a pool.

Return
New buffer or NULL if out of buffers.
Parameters
  • pool: Which pool to allocate the buffer from.
  • size: Amount of data the buffer must be able to fit.
  • timeout: Affects the action taken should the pool be empty. If K_NO_WAIT, then return immediately. If K_FOREVER, then wait as long as necessary. Otherwise, wait up to the specified number of milliseconds before timing out. Note that some types of data allocators do not support blocking (such as the HEAP type). In this case it’s still possible for net_buf_alloc() to fail (return NULL) even if it was given K_FOREVER.

struct net_buf *net_buf_alloc_with_data(struct net_buf_pool *pool, void *data, size_t size, s32_t timeout)

Allocate a new buffer from a pool but with external data pointer.

Allocate a new buffer from a pool, where the data pointer comes from the user and not from the pool.

Return
New buffer or NULL if out of buffers.
Parameters
  • pool: Which pool to allocate the buffer from.
  • data: External data pointer
  • size: Amount of data the pointed data buffer if able to fit.
  • timeout: Affects the action taken should the pool be empty. If K_NO_WAIT, then return immediately. If K_FOREVER, then wait as long as necessary. Otherwise, wait up to the specified number of milliseconds before timing out. Note that some types of data allocators do not support blocking (such as the HEAP type). In this case it’s still possible for net_buf_alloc() to fail (return NULL) even if it was given K_FOREVER.

struct net_buf *net_buf_get(struct k_fifo *fifo, s32_t timeout)

Get a buffer from a FIFO.

Return
New buffer or NULL if the FIFO is empty.
Parameters
  • fifo: Which FIFO to take the buffer from.
  • timeout: Affects the action taken should the FIFO be empty. If K_NO_WAIT, then return immediately. If K_FOREVER, then wait as long as necessary. Otherwise, wait up to the specified number of milliseconds before timing out.

static void net_buf_destroy(struct net_buf *buf)

Destroy buffer from custom destroy callback.

This helper is only intended to be used from custom destroy callbacks. If no custom destroy callback is given to NET_BUF_POOL_*_DEFINE() then there is no need to use this API.

Parameters
  • buf: Buffer to destroy.

void net_buf_reset(struct net_buf *buf)

Reset buffer.

Reset buffer data and flags so it can be reused for other purposes.

Parameters
  • buf: Buffer to reset.

void net_buf_simple_reserve(struct net_buf_simple *buf, size_t reserve)

Initialize buffer with the given headroom.

The buffer is not expected to contain any data when this API is called.

Parameters
  • buf: Buffer to initialize.
  • reserve: How much headroom to reserve.

void net_buf_slist_put(sys_slist_t *list, struct net_buf *buf)

Put a buffer into a list.

If the buffer contains follow-up fragments this function will take care of inserting them as well into the list.

Parameters
  • list: Which list to append the buffer to.
  • buf: Buffer.

struct net_buf *net_buf_slist_get(sys_slist_t *list)

Get a buffer from a list.

If the buffer had any fragments, these will automatically be recovered from the list as well and be placed to the buffer’s fragment list.

Return
New buffer or NULL if the FIFO is empty.
Parameters
  • list: Which list to take the buffer from.

void net_buf_put(struct k_fifo *fifo, struct net_buf *buf)

Put a buffer to the end of a FIFO.

If the buffer contains follow-up fragments this function will take care of inserting them as well into the FIFO.

Parameters
  • fifo: Which FIFO to put the buffer to.
  • buf: Buffer.

void net_buf_unref(struct net_buf *buf)

Decrements the reference count of a buffer.

The buffer is put back into the pool if the reference count reaches zero.

Parameters
  • buf: A valid pointer on a buffer

struct net_buf *net_buf_ref(struct net_buf *buf)

Increment the reference count of a buffer.

Return
the buffer newly referenced
Parameters
  • buf: A valid pointer on a buffer

struct net_buf *net_buf_clone(struct net_buf *buf, s32_t timeout)

Clone buffer.

Duplicate given buffer including any data and headers currently stored.

Return
Cloned buffer or NULL if out of buffers.
Parameters
  • buf: A valid pointer on a buffer
  • timeout: Affects the action taken should the pool be empty. If K_NO_WAIT, then return immediately. If K_FOREVER, then wait as long as necessary. Otherwise, wait up to the specified number of milliseconds before timing out.

static void *net_buf_user_data(const struct net_buf *buf)

Get a pointer to the user data of a buffer.

Return
Pointer to the user data of the buffer.
Parameters
  • buf: A valid pointer on a buffer

struct net_buf *net_buf_frag_last(struct net_buf *frags)

Find the last fragment in the fragment list.

Return
Pointer to last fragment in the list.

void net_buf_frag_insert(struct net_buf *parent, struct net_buf *frag)

Insert a new fragment to a chain of bufs.

Insert a new fragment into the buffer fragments list after the parent.

Note: This function takes ownership of the fragment reference so the caller is not required to unref.

Parameters
  • parent: Parent buffer/fragment.
  • frag: Fragment to insert.

struct net_buf *net_buf_frag_add(struct net_buf *head, struct net_buf *frag)

Add a new fragment to the end of a chain of bufs.

Append a new fragment into the buffer fragments list.

Note: This function takes ownership of the fragment reference so the caller is not required to unref.

Return
New head of the fragment chain. Either head (if head was non-NULL) or frag (if head was NULL).
Parameters
  • head: Head of the fragment chain.
  • frag: Fragment to add.

struct net_buf *net_buf_frag_del(struct net_buf *parent, struct net_buf *frag)

Delete existing fragment from a chain of bufs.

Return
Pointer to the buffer following the fragment, or NULL if it had no further fragments.
Parameters
  • parent: Parent buffer/fragment, or NULL if there is no parent.
  • frag: Fragment to delete.

size_t net_buf_linearize(void *dst, size_t dst_len, struct net_buf *src, size_t offset, size_t len)

Copy bytes from net_buf chain starting at offset to linear buffer.

Copy (extract) len bytes from src net_buf chain, starting from offset in it, to a linear buffer dst. Return number of bytes actually copied, which may be less than requested, if net_buf chain doesn’t have enough data, or destination buffer is too small.

Return
number of bytes actually copied
Parameters
  • dst: Destination buffer
  • dst_len: Destination buffer length
  • src: Source net_buf chain
  • offset: Starting offset to copy from
  • len: Number of bytes to copy

size_t net_buf_append_bytes(struct net_buf *buf, size_t len, const void *value, s32_t timeout, net_buf_allocator_cb allocate_cb, void *user_data)

Append data to a list of net_buf.

Append data to a net_buf. If there is not enough space in the net_buf then more net_buf will be added, unless there are no free net_buf and timeout occurs.

Return
Length of data actually added. This may be less than input length if other timeout than K_FOREVER was used, and there were no free fragments in a pool to accommodate all data.
Parameters
  • buf: Network buffer.
  • len: Total length of input data
  • value: Data to be added
  • timeout: Timeout is passed to the net_buf allocator callback.
  • allocate_cb: When a new net_buf is required, use this callback.
  • user_data: A user data pointer to be supplied to the allocate_cb. This pointer is can be anything from a mem_pool or a net_pkt, the logic is left up to the allocate_cb function.

static struct net_buf *net_buf_skip(struct net_buf *buf, size_t len)

Skip N number of bytes in a net_buf.

Skip N number of bytes starting from fragment’s offset. If the total length of data is placed in multiple fragments, this function will skip from all fragments until it reaches N number of bytes. Any fully skipped buffers are removed from the net_buf list.

Return
Pointer to the fragment or NULL and pos is 0 after successful skip, NULL and pos is 0xffff otherwise.
Parameters
  • buf: Network buffer.
  • len: Total length of data to be skipped.

static size_t net_buf_frags_len(struct net_buf *buf)

Calculate amount of bytes stored in fragments.

Calculates the total amount of data stored in the given buffer and the fragments linked to it.

Return
Number of bytes in the buffer and its fragments.
Parameters
  • buf: Buffer to start off with.

struct net_buf_simple
#include <buf.h>

Simple network buffer representation.

This is a simpler variant of the net_buf object (in fact net_buf uses net_buf_simple internally). It doesn’t provide any kind of reference counting, user data, dynamic allocation, or in general the ability to pass through kernel objects such as FIFOs.

The main use of this is for scenarios where the meta-data of the normal net_buf isn’t needed and causes too much overhead. This could be e.g. when the buffer only needs to be allocated on the stack or when the access to and lifetime of the buffer is well controlled and constrained.

struct net_buf_simple_state
#include <buf.h>

Parsing state of a buffer.

This is used for temporarily storing the parsing state of a buffer while giving control of the parsing to a routine which we don’t control.

struct net_buf
#include <buf.h>

Network buffer representation.

This struct is used to represent network buffers. Such buffers are normally defined through the NET_BUF_POOL_*_DEFINE() APIs and allocated using the net_buf_alloc() API.

struct net_buf_pool
#include <buf.h>

Network buffer pool representation.

This struct is used to represent a pool of network buffers.