/* udpcksum.c - udpcksum */#include <conf.h>#include <kernel.h>#include <network.h>/*------------------------------------------------------------------------ *  udpcksum -  compute a UDP pseudo-header checksum *------------------------------------------------------------------------ */unsigned shortudpcksum(struct ep *pep, int len){	struct	ip	*pip = (struct ip *)pep->ep_data;	struct	udp	*pudp = (struct udp *)pip->ip_data;	unsigned	short	*sptr;	unsigned	long ucksum;	int		i;	ucksum = 0;	sptr = (unsigned short *) &pip->ip_src;	/* 2*IP_ALEN octets = IP_ALEN shorts... */	/* they are in net order.		*/	for (i=0; i<IP_ALEN; ++i)		ucksum += *sptr++;	sptr = (unsigned short *)pudp;	ucksum += hs2net(IPT_UDP + len);	if (len % 2) {		((char *)pudp)[len] = 0;	/* pad */		len += 1;	/* for the following division */	}	len >>= 1;	/* convert to length in shorts */	for (i=0; i<len; ++i)		ucksum += *sptr++;	ucksum = (ucksum >> 16) + (ucksum & 0xffff);	ucksum += (ucksum >> 16);	return (short)(~ucksum & 0xffff);}