Atmel Software Framework

lwip-1.4.1/src/core/pbuf.c File Reference

Packet buffer management.

Packets are built from the pbuf data structure. It supports dynamic memory allocation for packet contents or can reference externally managed packet contents both in RAM and ROM. Quick allocation for incoming packets is provided through pools with fixed sized pbufs.

A packet may span over multiple pbufs, chained as a singly linked list. This is called a "pbuf chain".

Multiple packets may be queued, also using this singly linked list. This is called a "packet queue".

So, a packet queue consists of one or more pbuf chains, each of which consist of one or more pbufs. CURRENTLY, PACKET QUEUES ARE NOT SUPPORTED!!! Use helper structs to queue multiple packets.

The differences between a pbuf chain and a packet queue are very precise but subtle.

The last pbuf of a packet has a ->tot_len field that equals the ->len field. It can be found by traversing the list. If the last pbuf of a packet has a ->next field other than NULL, more packets are on the queue.

Therefore, looping through a pbuf of a single packet, has an loop end condition (tot_len == p->len), NOT (next == NULL).

#include "lwip/opt.h"
#include "lwip/stats.h"
#include "lwip/def.h"
#include "lwip/mem.h"
#include "lwip/memp.h"
#include "lwip/pbuf.h"
#include "lwip/sys.h"
#include "arch/perf.h"
#include <string.h>

Macros

#define PBUF_POOL_BUFSIZE_ALIGNED   LWIP_MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE)
 
#define PBUF_POOL_IS_EMPTY()
 
#define SIZEOF_STRUCT_PBUF   LWIP_MEM_ALIGN_SIZE(sizeof(struct pbuf))
 

Functions

struct pbufpbuf_alloc (pbuf_layer layer, u16_t length, pbuf_type type)
 Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type). More...
 
void pbuf_cat (struct pbuf *h, struct pbuf *t)
 Concatenate two pbufs (each may be a pbuf chain) and take over the caller's reference of the tail pbuf. More...
 
void pbuf_chain (struct pbuf *h, struct pbuf *t)
 Chain two pbufs (or pbuf chains) together. More...
 
u8_t pbuf_clen (struct pbuf *p)
 Count number of pbufs in a chain. More...
 
struct pbufpbuf_coalesce (struct pbuf *p, pbuf_layer layer)
 Creates a single pbuf out of a queue of pbufs. More...
 
err_t pbuf_copy (struct pbuf *p_to, struct pbuf *p_from)
 Create PBUF_RAM copies of pbufs. More...
 
u16_t pbuf_copy_partial (struct pbuf *buf, void *dataptr, u16_t len, u16_t offset)
 Copy (part of) the contents of a packet buffer to an application supplied buffer. More...
 
struct pbufpbuf_dechain (struct pbuf *p)
 Dechains the first pbuf from its succeeding pbufs in the chain. More...
 
u8_t pbuf_free (struct pbuf *p)
 Dereference a pbuf chain or queue and deallocate any no-longer-used pbufs at the head of this chain or queue. More...
 
u8_t pbuf_get_at (struct pbuf *p, u16_t offset)
 Get one byte from the specified position in a pbuf WARNING: returns zero for offset >= p->tot_len. More...
 
u8_t pbuf_header (struct pbuf *p, s16_t header_size_increment)
 Adjusts the payload pointer to hide or reveal headers in the payload. More...
 
u16_t pbuf_memcmp (struct pbuf *p, u16_t offset, const void *s2, u16_t n)
 Compare pbuf contents at specified offset with memory s2, both of length n. More...
 
u16_t pbuf_memfind (struct pbuf *p, const void *mem, u16_t mem_len, u16_t start_offset)
 Find occurrence of mem (with length mem_len) in pbuf p, starting at offset start_offset. More...
 
void pbuf_realloc (struct pbuf *p, u16_t new_len)
 Shrink a pbuf chain to a desired length. More...
 
void pbuf_ref (struct pbuf *p)
 Increment the reference count of the pbuf. More...
 
u16_t pbuf_strstr (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! More...
 
err_t pbuf_take (struct pbuf *buf, const void *dataptr, u16_t len)
 Copy application supplied data into a pbuf. More...
 

#define PBUF_POOL_BUFSIZE_ALIGNED   LWIP_MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE)

Referenced by pbuf_alloc().

#define PBUF_POOL_IS_EMPTY ( )

Referenced by pbuf_alloc().

#define SIZEOF_STRUCT_PBUF   LWIP_MEM_ALIGN_SIZE(sizeof(struct pbuf))

Referenced by pbuf_alloc(), and pbuf_header().

struct pbuf* pbuf_alloc ( pbuf_layer  layer,
u16_t  length,
pbuf_type  type 
)

Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type).

The actual memory allocated for the pbuf is determined by the layer at which the pbuf is allocated and the requested size (from the size parameter).

Parameters
layerflag to define header size
lengthsize of the pbuf's payload
typethis parameter decides how and where the pbuf should be allocated as follows:
  • PBUF_RAM: buffer memory for pbuf is allocated as one large chunk. This includes protocol headers as well.
  • PBUF_ROM: no buffer memory is allocated for the pbuf, even for protocol headers. Additional headers must be prepended by allocating another pbuf and chain in to the front of the ROM pbuf. It is assumed that the memory used is really similar to ROM in that it is immutable and will not be changed. Memory which is dynamic should generally not be attached to PBUF_ROM pbufs. Use PBUF_REF instead.
  • PBUF_REF: no buffer memory is allocated for the pbuf, even for protocol headers. It is assumed that the pbuf is only being used in a single thread. If the pbuf gets queued, then pbuf_take should be called to copy the buffer.
  • PBUF_POOL: the pbuf is allocated as a pbuf chain, with pbufs from the pbuf pool that is allocated during pbuf_init().
Returns
the allocated pbuf. If multiple pbufs where allocated, this is the first pbuf of a pbuf chain.

References pbuf::flags, pbuf::len, length, LWIP_ASSERT, LWIP_DBG_LEVEL_SERIOUS, LWIP_DBG_TRACE, LWIP_DEBUGF, LWIP_MEM_ALIGN, LWIP_MEM_ALIGN_SIZE, LWIP_MIN, MEM_ALIGNMENT, mem_malloc(), memp_malloc(), pbuf::next, NULL, pbuf::payload, PBUF_DEBUG, pbuf_free(), PBUF_IP, PBUF_IP_HLEN, PBUF_LINK, PBUF_LINK_HLEN, PBUF_POOL, PBUF_POOL_BUFSIZE_ALIGNED, PBUF_POOL_IS_EMPTY, PBUF_RAM, PBUF_RAW, PBUF_REF, PBUF_ROM, PBUF_TRANSPORT, PBUF_TRANSPORT_HLEN, pbuf::ref, SIZEOF_STRUCT_PBUF, pbuf::tot_len, pbuf::type, and U16_F.

void pbuf_cat ( struct pbuf h,
struct pbuf t 
)

Concatenate two pbufs (each may be a pbuf chain) and take over the caller's reference of the tail pbuf.

Note
The caller MAY NOT reference the tail pbuf afterwards. Use pbuf_chain() for that purpose.
See Also
pbuf_chain()

References pbuf::len, LWIP_ASSERT, LWIP_ERROR, pbuf::next, NULL, and pbuf::tot_len.

void pbuf_chain ( struct pbuf h,
struct pbuf t 
)

Chain two pbufs (or pbuf chains) together.

The caller MUST call pbuf_free(t) once it has stopped using it. Use pbuf_cat() instead if you no longer use t.

Parameters
hhead pbuf (chain)
ttail pbuf (chain)
Note
The pbufs MUST belong to the same packet.
MAY NOT be called on a packet queue.

The ->tot_len fields of all pbufs of the head chain are adjusted. The ->next field of the last pbuf of the head chain is adjusted. The ->ref field of the first pbuf of the tail chain is adjusted.

References LWIP_DBG_TRACE, LWIP_DEBUGF, pbuf_cat(), PBUF_DEBUG, and pbuf_ref().

u8_t pbuf_clen ( struct pbuf p)

Count number of pbufs in a chain.

Parameters
pfirst pbuf of chain
Returns
the number of pbufs in a chain

References pbuf::next, and NULL.

struct pbuf* pbuf_coalesce ( struct pbuf p,
pbuf_layer  layer 
)

Creates a single pbuf out of a queue of pbufs.

Remarks
: Either the source pbuf 'p' is freed by this function or the original pbuf 'p' is returned, therefore the caller has to check the result!
Parameters
pthe source pbuf
layerpbuf_layer of the new pbuf
Returns
a new, single pbuf (p->next is NULL) or the old pbuf if allocation fails

References ERR_OK, LWIP_ASSERT, pbuf::next, NULL, pbuf_alloc(), pbuf_copy(), pbuf_free(), PBUF_RAM, and pbuf::tot_len.

err_t pbuf_copy ( struct pbuf p_to,
struct pbuf p_from 
)

Create PBUF_RAM copies of pbufs.

Used to queue packets on behalf of the lwIP stack, such as ARP based queueing.

Note
You MUST explicitly use p = pbuf_take(p);
Only one packet is copied, no packet queue!
Parameters
p_topbuf destination of the copy
p_frompbuf source of the copy
Returns
ERR_OK if pbuf was copied ERR_ARG if one of the pbufs is NULL or p_to is not big enough to hold p_from

References ERR_ARG, ERR_OK, ERR_VAL, pbuf::len, LWIP_ASSERT, LWIP_DBG_TRACE, LWIP_DEBUGF, LWIP_ERROR, MEMCPY, pbuf::next, NULL, pbuf::payload, PBUF_DEBUG, and pbuf::tot_len.

u16_t pbuf_copy_partial ( struct pbuf buf,
void *  dataptr,
u16_t  len,
u16_t  offset 
)

Copy (part of) the contents of a packet buffer to an application supplied buffer.

Parameters
bufthe pbuf from which to copy data
dataptrthe application supplied buffer
lenlength of data to copy (dataptr must be big enough). No more than buf->tot_len will be copied, irrespective of len
offsetoffset into the packet buffer from where to begin copying len bytes
Returns
the number of bytes copied, or 0 on failure

References pbuf::len, LWIP_ERROR, MEMCPY, pbuf::next, NULL, and pbuf::payload.

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.

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

References pbuf::len, LWIP_ASSERT, LWIP_DBG_TRACE, LWIP_DEBUGF, pbuf::next, NULL, PBUF_DEBUG, pbuf_free(), and pbuf::tot_len.

u8_t pbuf_free ( struct pbuf p)

Dereference a pbuf chain or queue and deallocate any no-longer-used pbufs at the head of this chain or queue.

Decrements the pbuf reference count. If it reaches zero, the pbuf is deallocated.

For a pbuf chain, this is repeated for each pbuf in the chain, up to the first pbuf which has a non-zero reference count after decrementing. So, when all reference counts are one, the whole chain is free'd.

Parameters
pThe pbuf (chain) to be dereferenced.
Returns
the number of pbufs that were de-allocated from the head of the chain.
Note
MUST NOT be called on a packet queue (Not verified to work yet).
the reference counter of a pbuf equals the number of pointers that refer to the pbuf (or into the pbuf).

examples:

Assuming existing chains a->b->c with the following reference counts, calling pbuf_free(a) results in:

1->2->3 becomes ...1->3 3->3->3 becomes 2->3->3 1->1->2 becomes ......1 2->1->1 becomes 1->1->1 1->1->1 becomes .......

References count, pbuf::flags, LWIP_ASSERT, LWIP_DBG_LEVEL_SERIOUS, LWIP_DBG_TRACE, LWIP_DEBUGF, mem_free(), memp_free(), pbuf::next, NULL, PBUF_DEBUG, PBUF_FLAG_IS_CUSTOM, PBUF_POOL, PBUF_RAM, PBUF_REF, PBUF_ROM, PERF_START, PERF_STOP, pbuf::ref, SYS_ARCH_DECL_PROTECT, SYS_ARCH_PROTECT, SYS_ARCH_UNPROTECT, pbuf::type, and U16_F.

u8_t pbuf_get_at ( struct pbuf p,
u16_t  offset 
)

Get one byte from the specified position in a pbuf WARNING: returns zero for offset >= p->tot_len.

Parameters
ppbuf to parse
offsetoffset into p of the byte to return
Returns
byte at an offset into p OR ZERO IF 'offset' >= p->tot_len

References pbuf::len, pbuf::next, NULL, and pbuf::payload.

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.

Parameters
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 succesful.

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.

Returns
non-zero on failure, zero on success.

References if(), pbuf::len, LWIP_ASSERT, LWIP_DBG_LEVEL_SERIOUS, LWIP_DBG_TRACE, LWIP_DEBUGF, LWIP_ERROR, NULL, pbuf::payload, payload, PBUF_DEBUG, PBUF_POOL, PBUF_RAM, PBUF_REF, PBUF_ROM, S16_F, SIZEOF_STRUCT_PBUF, pbuf::tot_len, and pbuf::type.

u16_t pbuf_memcmp ( struct pbuf p,
u16_t  offset,
const void *  s2,
u16_t  n 
)

Compare pbuf contents at specified offset with memory s2, both of length n.

Parameters
ppbuf to compare
offsetoffset into p at wich to start comparing
s2buffer to compare
nlength of buffer to compare
Returns
zero if equal, nonzero otherwise (0xffff if p is too short, diffoffset+1 otherwise)

References a(), b, i, pbuf::len, n, pbuf::next, NULL, pbuf_get_at(), and start.

u16_t pbuf_memfind ( struct pbuf p,
const void *  mem,
u16_t  mem_len,
u16_t  start_offset 
)

Find occurrence of mem (with length mem_len) in pbuf p, starting at offset start_offset.

Parameters
ppbuf to search, maximum length is 0xFFFE since 0xFFFF is used as return value 'not found'
memsearch for the contents of this buffer
mem_lenlength of 'mem'
start_offsetoffset into p at which to start searching
Returns
0xFFFF if substr was not found in p or the index where it was found

References i, max, pbuf_memcmp(), and pbuf::tot_len.

void pbuf_realloc ( struct pbuf p,
u16_t  new_len 
)

Shrink a pbuf chain to a desired length.

Parameters
ppbuf to shrink.
new_lendesired new length of pbuf chain

Depending on the desired length, the first few pbufs in a chain might be skipped and left unchanged. The new last pbuf in the chain will be resized, and any remaining pbufs will be freed.

Note
If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.
May not be called on a packet queue.
Despite its name, pbuf_realloc cannot grow the size of a pbuf (chain).

References pbuf::len, LWIP_ASSERT, mem_trim(), pbuf::next, NULL, pbuf::payload, pbuf_free(), PBUF_POOL, PBUF_RAM, PBUF_REF, PBUF_ROM, pbuf::tot_len, and pbuf::type.

void pbuf_ref ( struct pbuf p)

Increment the reference count of the pbuf.

Parameters
ppbuf to increase reference counter of

References NULL, pbuf::ref, SYS_ARCH_DECL_PROTECT, SYS_ARCH_PROTECT, and SYS_ARCH_UNPROTECT.

u16_t pbuf_strstr ( 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!

Parameters
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
Returns
0xFFFF if substr was not found in p or the index where it was found

References NULL, pbuf_memfind(), and pbuf::tot_len.

err_t pbuf_take ( struct pbuf buf,
const void *  dataptr,
u16_t  len 
)

Copy application supplied data into a pbuf.

This function can only be used to copy the equivalent of buf->tot_len data.

Parameters
bufpbuf to fill with data
dataptrapplication supplied data buffer
lenlength of the application supplied data buffer
Returns
ERR_OK if successful, ERR_MEM if the pbuf is not big enough

References ERR_ARG, ERR_OK, pbuf::len, LWIP_ASSERT, LWIP_ERROR, MEMCPY, pbuf::next, NULL, pbuf::payload, and pbuf::tot_len.