TCP Checksum

tcp_csum_core.c

uint32_t __core_csum_tcp(uint16_t *addr, uint32_t count)
{
    register uint32_t sum = 0;

    while (count > 1)  {
        sum += *addr++;
        count -= 2;
    }

    /*  Add left-over byte, if any, (zero padding) */
    if (count)
        sum += *(uint8_t *) addr;

    /*  Fold 32-bit sum to 16 bits */
    while (sum >> 16)
        sum = (sum & 0xffff) + (sum >> 16);

    return ~sum;
}