File: ip.c

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/* Modified from FreeBSD 2.1 sys/i386/boot/netboot */
/**************************************************************************
NETBOOT -  BOOTP/TFTP Bootstrap Program

Author: Martin Renters
  Date: Dec/93

**************************************************************************/

#include "ip.h"

/*
 * IP checksum algorithm.
 */
unsigned short
ipchksum(void *ipv, int len)
{
	unsigned short *ip = ipv;
	unsigned long sum = 0;

	len >>= 1;
	while (len--) {
		sum += *(ip++);
		if (sum > 0xFFFF)
			sum -= 0xFFFF;
	}
	return((~sum) & 0x0000FFFF);
}