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inet_chksum.h File Reference
`#include "lwip/opt.h"`
`#include "lwip/pbuf.h"`
`#include "lwip/ip_addr.h"`

## Macros

#define | SWAP_BYTES_IN_WORD(w)
#define | FOLD_U32T(u)

## Functions

u16_t | inet_chksum_pbuf (struct pbuf *p)
u16_t | ip6_chksum_pseudo (struct pbuf *p, u8_t proto, u16_t proto_len, const ip6_addr_t *src, const ip6_addr_t *dest)
u16_t | ip6_chksum_pseudo_partial (struct pbuf *p, u8_t proto, u16_t proto_len, u16_t chksum_len, const ip6_addr_t *src, const ip6_addr_t *dest)

## Detailed Description

IP checksum calculation functions

## Macro Definition Documentation

## FOLD_U32T

#define FOLD_U32T | ( |  | u | ) |

Value:
((u32_t)(((u) >> 16) + ((u) & 0x0000ffffUL)))

Split an u32_t in two u16_ts and add them up

## SWAP_BYTES_IN_WORD

#define SWAP_BYTES_IN_WORD | ( |  | w | ) |

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

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

## Function Documentation

## 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

## ip6_chksum_pseudo()

u16_t ip6_chksum_pseudo | ( | struct pbuf * | p,
|  | u8_t | proto,
|  | u16_t | proto_len,
|  | const ip6_addr_t * | src,
|  | const ip6_addr_t * | dest )

Calculates the checksum with IPv6 pseudo header used by TCP and UDP for a pbuf chain. IPv6 addresses are expected to be in network byte order.

Parameters

  p | chain of pbufs over that a checksum should be calculated (ip data part)
  proto | ipv6 protocol/next header (used for checksum of pseudo header)
  proto_len | length of the ipv6 payload (used for checksum of pseudo header)
  src | source ipv6 address (used for checksum of pseudo header)
  dest | destination ipv6 address (used for checksum of pseudo header)

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

## ip6_chksum_pseudo_partial()

u16_t ip6_chksum_pseudo_partial | ( | struct pbuf * | p,
|  | u8_t | proto,
|  | u16_t | proto_len,
|  | u16_t | chksum_len,
|  | const ip6_addr_t * | src,
|  | const ip6_addr_t * | dest )

Calculates the checksum with IPv6 pseudo header used by TCP and UDP for a pbuf chain. IPv6 addresses are expected to be in network byte order. Will only compute for a portion of the payload.

Parameters

  p | chain of pbufs over that a checksum should be calculated (ip data part)
  proto | ipv6 protocol/next header (used for checksum of pseudo header)
  proto_len | length of the ipv6 payload (used for checksum of pseudo header)
  chksum_len | number of payload bytes used to compute chksum
  src | source ipv6 address (used for checksum of pseudo header)
  dest | destination ipv6 address (used for checksum of pseudo header)

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