inet_chksum.h File Reference

#include "lwip/opt.h"
#include "lwip/pbuf.h"
#include "lwip/ip_addr.h"

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Macros
#define	SWAP_BYTES_IN_WORD(w)   (((w) & 0xff) << 8) | (((w) & 0xff00) >> 8)
#define	FOLD_U32T(u)   (((u) >> 16) + ((u) & 0x0000ffffUL))
#define	LWIP_CHKSUM_COPY_ALGORITHM   0

Functions
u16_t	inet_chksum (void *dataptr, u16_t len)
u16_t	inet_chksum_pbuf (struct pbuf *p)
u16_t	inet_chksum_pseudo (struct pbuf *p, ip_addr_t *src, ip_addr_t *dest, u8_t proto, u16_t proto_len)
u16_t	inet_chksum_pseudo_partial (struct pbuf *p, ip_addr_t *src, ip_addr_t *dest, u8_t proto, u16_t proto_len, u16_t chksum_len)

Macro Definition Documentation

FOLD_U32T

#define FOLD_U32T

(

u

)

(((u) >> 16) + ((u) & 0x0000ffffUL))

Split an u32_t in two u16_ts and add them up

Definition at line 53 of file inet_chksum.h.

LWIP_CHKSUM_COPY_ALGORITHM

#define LWIP_CHKSUM_COPY_ALGORITHM   0

Definition at line 66 of file inet_chksum.h.

SWAP_BYTES_IN_WORD

#define SWAP_BYTES_IN_WORD

(

w

)

(((w) & 0xff) << 8) | (((w) & 0xff00) >> 8)

Swap the bytes in an u16_t: much like htons() for little-endian

Definition at line 47 of file inet_chksum.h.

Function Documentation

inet_chksum()

u16_t inet_chksum	(	void *	dataptr,
		u16_t	len
	)

Definition at line 396 of file inet_chksum.c.

{
  return ~LWIP_CHKSUM(dataptr, len);
}

inet_chksum_pbuf()

u16_t inet_chksum_pbuf

(

struct pbuf *

p

)

Calculate a checksum over a chain of pbufs (without pseudo-header, much like inet_chksum only pbufs are used).

Parameters

p	pbuf chain over that the checksum should be calculated

Returns

checksum (as u16_t) to be saved directly in the protocol header

Definition at line 409 of file inet_chksum.c.

{
  u32_t acc;
  struct pbuf *q;
  u8_t swapped;
 
  acc = 0;
  swapped = 0;
  for(q = p; q != NULL; q = q->next) {
    acc += LWIP_CHKSUM(q->payload, q->len);
    acc = FOLD_U32T(acc);
    if (q->len % 2 != 0) {
      swapped = 1 - swapped;
      acc = SWAP_BYTES_IN_WORD(acc);
    }
  }
 
  if (swapped) {
    acc = SWAP_BYTES_IN_WORD(acc);
  }
  return (u16_t)~(acc & 0xffffUL);
}

inet_chksum_pseudo()

u16_t inet_chksum_pseudo	(	struct pbuf *	p,
		ip_addr_t *	src,
		ip_addr_t *	dest,
		u8_t	proto,
		u16_t	proto_len
	)

Definition at line 272 of file inet_chksum.c.

{
  u32_t acc;
  u32_t addr;
  struct pbuf *q;
  u8_t swapped;
 
  acc = 0;
  swapped = 0;
  /* iterate through all pbuf in chain */
  for(q = p; q != NULL; q = q->next) {
    LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): checksumming pbuf %p (has next %p) \n",
      (void *)q, (void *)q->next));
    acc += LWIP_CHKSUM(q->payload, q->len);
    /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%"X32_F" \n", acc));*/
    /* just executing this next line is probably faster that the if statement needed
       to check whether we really need to execute it, and does no harm */
    acc = FOLD_U32T(acc);
    if (q->len % 2 != 0) {
      swapped = 1 - swapped;
      acc = SWAP_BYTES_IN_WORD(acc);
    }
    /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/
  }
 
  if (swapped) {
    acc = SWAP_BYTES_IN_WORD(acc);
  }
  addr = ip4_addr_get_u32(src);
  acc += (addr & 0xffffUL);
  acc += ((addr >> 16) & 0xffffUL);
  addr = ip4_addr_get_u32(dest);
  acc += (addr & 0xffffUL);
  acc += ((addr >> 16) & 0xffffUL);
  acc += (u32_t)htons((u16_t)proto);
  acc += (u32_t)htons(proto_len);
 
  /* Fold 32-bit sum to 16 bits
     calling this twice is propably faster than if statements... */
  acc = FOLD_U32T(acc);
  acc = FOLD_U32T(acc);
  LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): pbuf chain lwip_chksum()=%"X32_F"\n", acc));
  return (u16_t)~(acc & 0xffffUL);
}

Referenced by tcp_create_segment_wnd().

inet_chksum_pseudo_partial()

u16_t inet_chksum_pseudo_partial	(	struct pbuf *	p,
		ip_addr_t *	src,
		ip_addr_t *	dest,
		u8_t	proto,
		u16_t	proto_len,
		u16_t	chksum_len
	)

Definition at line 332 of file inet_chksum.c.

{
  u32_t acc;
  u32_t addr;
  struct pbuf *q;
  u8_t swapped;
  u16_t chklen;
 
  acc = 0;
  swapped = 0;
  /* iterate through all pbuf in chain */
  for(q = p; (q != NULL) && (chksum_len > 0); q = q->next) {
    LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): checksumming pbuf %p (has next %p) \n",
      (void *)q, (void *)q->next));
    chklen = q->len;
    if (chklen > chksum_len) {
      chklen = chksum_len;
    }
    acc += LWIP_CHKSUM(q->payload, chklen);
    chksum_len -= chklen;
    LWIP_ASSERT("delete me", chksum_len < 0x7fff);
    /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%"X32_F" \n", acc));*/
    /* fold the upper bit down */
    acc = FOLD_U32T(acc);
    if (q->len % 2 != 0) {
      swapped = 1 - swapped;
      acc = SWAP_BYTES_IN_WORD(acc);
    }
    /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/
  }
 
  if (swapped) {
    acc = SWAP_BYTES_IN_WORD(acc);
  }
  addr = ip4_addr_get_u32(src);
  acc += (addr & 0xffffUL);
  acc += ((addr >> 16) & 0xffffUL);
  addr = ip4_addr_get_u32(dest);
  acc += (addr & 0xffffUL);
  acc += ((addr >> 16) & 0xffffUL);
  acc += (u32_t)htons((u16_t)proto);
  acc += (u32_t)htons(proto_len);
 
  /* Fold 32-bit sum to 16 bits
     calling this twice is propably faster than if statements... */
  acc = FOLD_U32T(acc);
  acc = FOLD_U32T(acc);
  LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): pbuf chain lwip_chksum()=%"X32_F"\n", acc));
  return (u16_t)~(acc & 0xffffUL);
}