inet_chksum.h File Reference

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

Go to the source code of this file.

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 (const void *dataptr, u16_t len)
u16_t	inet_chksum_pbuf (struct pbuf *p)
u16_t	ip_chksum_pseudo (struct pbuf *p, u8_t proto, u16_t proto_len, const ip_addr_t *src, const ip_addr_t *dest)
u16_t	ip_chksum_pseudo_partial (struct pbuf *p, u8_t proto, u16_t proto_len, u16_t chksum_len, const ip_addr_t *src, const ip_addr_t *dest)

Detailed Description

IP checksum calculation functions

Macro Definition Documentation

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 lwip_htons() for little-endian

FOLD_U32T

#define FOLD_U32T

(

u

)

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

Split an u32_t in two u16_ts and add them up

LWIP_CHKSUM_COPY_ALGORITHM

#define LWIP_CHKSUM_COPY_ALGORITHM   0

Function Documentation

inet_chksum()

u16_t inet_chksum	(	const void *	dataptr,
		u16_t	len
	)

{
  return (u16_t)~(unsigned int)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

{
  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);
}

ip_chksum_pseudo()

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

{
#if LWIP_IPV6
  if (IP_IS_V6(dest)) {
    return ip6_chksum_pseudo(p, proto, proto_len, ip_2_ip6(src), ip_2_ip6(dest));
  }
#endif /* LWIP_IPV6 */
#if LWIP_IPV4 && LWIP_IPV6
  else
#endif /* LWIP_IPV4 && LWIP_IPV6 */
#if LWIP_IPV4
  {
    return inet_chksum_pseudo(p, proto, proto_len, ip_2_ip4(src), ip_2_ip4(dest));
  }
#endif /* LWIP_IPV4 */
}

ip_chksum_pseudo_partial()

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

{
#if LWIP_IPV6
  if (IP_IS_V6(dest)) {
    return ip6_chksum_pseudo_partial(p, proto, proto_len, chksum_len, ip_2_ip6(src), ip_2_ip6(dest));
  }
#endif /* LWIP_IPV6 */
#if LWIP_IPV4 && LWIP_IPV6
  else
#endif /* LWIP_IPV4 && LWIP_IPV6 */
#if LWIP_IPV4
  {
    return inet_chksum_pseudo_partial(p, proto, proto_len, chksum_len, ip_2_ip4(src), ip_2_ip4(dest));
  }
#endif /* LWIP_IPV4 */
}