lwIP  2.0.2
Lightweight IP stack
pbuf.h File Reference
#include "lwip/opt.h"
#include "lwip/err.h"

Data Structures

struct  pbuf
struct  pbuf_rom
struct  pbuf_custom


#define PBUF_FLAG_PUSH   0x01U
#define PBUF_FLAG_IS_CUSTOM   0x02U
#define PBUF_FLAG_LLBCAST   0x08U
#define PBUF_FLAG_LLMCAST   0x10U
#define PBUF_FLAG_TCP_FIN   0x20U


typedef void(* pbuf_free_custom_fn) (struct pbuf *p)


enum  pbuf_layer {
enum  pbuf_type { PBUF_RAM, PBUF_ROM, PBUF_REF, PBUF_POOL }


struct pbufpbuf_alloc (pbuf_layer l, u16_t length, pbuf_type type)
struct pbufpbuf_alloced_custom (pbuf_layer l, u16_t length, pbuf_type type, struct pbuf_custom *p, void *payload_mem, u16_t payload_mem_len)
void pbuf_realloc (struct pbuf *p, u16_t size)
u8_t pbuf_header (struct pbuf *p, s16_t header_size)
u8_t pbuf_header_force (struct pbuf *p, s16_t header_size)
void pbuf_ref (struct pbuf *p)
u8_t pbuf_free (struct pbuf *p)
u16_t pbuf_clen (const struct pbuf *p)
void pbuf_cat (struct pbuf *head, struct pbuf *tail)
void pbuf_chain (struct pbuf *head, struct pbuf *tail)
struct pbufpbuf_dechain (struct pbuf *p)
err_t pbuf_copy (struct pbuf *p_to, const struct pbuf *p_from)
u16_t pbuf_copy_partial (const struct pbuf *p, void *dataptr, u16_t len, u16_t offset)
err_t pbuf_take (struct pbuf *buf, const void *dataptr, u16_t len)
err_t pbuf_take_at (struct pbuf *buf, const void *dataptr, u16_t len, u16_t offset)
struct pbufpbuf_skip (struct pbuf *in, u16_t in_offset, u16_t *out_offset)
struct pbufpbuf_coalesce (struct pbuf *p, pbuf_layer layer)
u8_t pbuf_get_at (const struct pbuf *p, u16_t offset)
int pbuf_try_get_at (const struct pbuf *p, u16_t offset)
void pbuf_put_at (struct pbuf *p, u16_t offset, u8_t data)
u16_t pbuf_memcmp (const struct pbuf *p, u16_t offset, const void *s2, u16_t n)
u16_t pbuf_memfind (const struct pbuf *p, const void *mem, u16_t mem_len, u16_t start_offset)
u16_t pbuf_strstr (const struct pbuf *p, const char *substr)

Detailed Description

pbuf API

Macro Definition Documentation



LWIP_SUPPORT_CUSTOM_PBUF==1: Custom pbufs behave much like their pbuf type but they are allocated by external code (initialised by calling pbuf_alloced_custom()) and when pbuf_free gives up their last reference, they are freed by calling pbuf_custom->custom_free_function(). Currently, the pbuf_custom code is only needed for one specific configuration of IP_FRAG, unless required by external driver/application code.


#define PBUF_FLAG_IS_CUSTOM   0x02U

indicates this is a custom pbuf: pbuf_free calls pbuf_custom->custom_free_function() when the last reference is released (plus custom PBUF_RAM cannot be trimmed)


#define PBUF_FLAG_LLBCAST   0x08U

indicates this pbuf was received as link-level broadcast


#define PBUF_FLAG_LLMCAST   0x10U

indicates this pbuf was received as link-level multicast



indicates this pbuf is UDP multicast to be looped back


#define PBUF_FLAG_PUSH   0x01U

indicates this packet's data should be immediately passed to the application


#define PBUF_FLAG_TCP_FIN   0x20U

indicates this pbuf includes a TCP FIN flag



Define this to 0 to prevent freeing ooseq pbufs when the PBUF_POOL is empty

Typedef Documentation

◆ pbuf_free_custom_fn

typedef void(* pbuf_free_custom_fn) (struct pbuf *p)

Prototype for a function to free a custom pbuf

Function Documentation

◆ pbuf_clen()

u16_t pbuf_clen ( const struct pbuf p)

Count number of pbufs in a chain

pfirst pbuf of chain
the number of pbufs in a chain

◆ pbuf_dechain()

struct pbuf* pbuf_dechain ( struct pbuf p)

Dechains the first pbuf from its succeeding pbufs in the chain.

Makes p->tot_len field equal to p->len.

ppbuf to dechain
remainder of the pbuf chain, or NULL if it was de-allocated.
May not be called on a packet queue.

◆ pbuf_header()

u8_t pbuf_header ( struct pbuf p,
s16_t  header_size_increment 

Adjusts the payload pointer to hide or reveal headers in the payload.

Adjusts the ->payload pointer so that space for a header (dis)appears in the pbuf payload.

The ->payload, ->tot_len and ->len fields are adjusted.

ppbuf to change the header size.
header_size_incrementNumber of bytes to increment header size which increases the size of the pbuf. New space is on the front. (Using a negative value decreases the header size.) If hdr_size_inc is 0, this function does nothing and returns successful.

PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so the call will fail. A check is made that the increase in header size does not move the payload pointer in front of the start of the buffer.

non-zero on failure, zero on success.

◆ pbuf_header_force()

u8_t pbuf_header_force ( struct pbuf p,
s16_t  header_size_increment 

Same as pbuf_header but does not check if 'header_size > 0' is allowed. This is used internally only, to allow PBUF_REF for RX.

◆ pbuf_strstr()

u16_t pbuf_strstr ( const struct pbuf p,
const char *  substr 

Find occurrence of substr with length substr_len in pbuf p, start at offset start_offset WARNING: in contrast to strstr(), this one does not stop at the first \0 in the pbuf/source string!

ppbuf to search, maximum length is 0xFFFE since 0xFFFF is used as return value 'not found'
substrstring to search for in p, maximum length is 0xFFFE
0xFFFF if substr was not found in p or the index where it was found