/**
* @brief Calculate the UDP checksum dependent on the network protocol
*
* @note If the checksum turns out to be 0x0000, the function returns 0xffff
* as specified in RFC768
*
* @param[in] pkt pointer to the packet in the packet buffer
* @param[in] pseudo_hdr pointer to the network layer header
* @param[in] payload pointer to the payload
*
* @return the checksum of the pkt in host byte order
* @return 0 on error
*/
static uint16_t _calc_csum(ng_pktsnip_t *hdr, ng_pktsnip_t *pseudo_hdr,
ng_pktsnip_t *payload)
{
uint16_t csum = 0;
uint16_t len = (uint16_t)hdr->size;
/* process the payload */
while (payload && payload != hdr) {
csum = ng_inet_csum(csum, (uint8_t *)(payload->data), payload->size);
len += (uint16_t)payload->size;
payload = payload->next;
}
/* process applicable UDP header bytes */
csum = ng_inet_csum(csum, (uint8_t *)hdr->data, sizeof(ng_udp_hdr_t));
switch (pseudo_hdr->type) {
#ifdef MODULE_NG_IPV6
case NG_NETTYPE_IPV6:
csum = ng_ipv6_hdr_inet_csum(csum, pseudo_hdr->data,
NG_PROTNUM_UDP, len);
break;
#endif
default:
(void)len;
return 0;
}
/* return inverted results */
return ~csum;
}
static inline uint16_t _calc_csum(ng_pktsnip_t *hdr,
ng_pktsnip_t *pseudo_hdr,
ng_pktsnip_t *payload)
{
uint16_t csum = 0;
uint16_t len = (uint16_t)hdr->size;
while (payload && (payload != hdr)) {
csum = ng_inet_csum(csum, payload->data, payload->size);
len += (uint16_t)payload->size;
payload = payload->next;
}
csum = ng_inet_csum(csum, hdr->data, hdr->size);
csum = ng_ipv6_hdr_inet_csum(csum, pseudo_hdr->data, NG_PROTNUM_ICMPV6,
len);
return ~csum;
}
