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#include <u.h>
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#include <libc.h>
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#include <ip.h>
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#include <auth.h>
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#include "ppp.h"
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static	ushort	endian	= 1;
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static	uchar*	aendian	= (uchar*)&endian;
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#define	LITTLE	*aendian
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ushort
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ptclbsum(uchar *addr, int len)
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{
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	ulong losum, hisum, mdsum, x;
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	ulong t1, t2;
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	losum = 0;
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	hisum = 0;
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	mdsum = 0;
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	x = 0;
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	if((uintptr)addr & 1) {
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		if(len) {
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			hisum += addr[0];
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			len--;
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			addr++;
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		}
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		x = 1;
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	}
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	while(len >= 16) {
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		t1 = *(ushort*)(addr+0);
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		t2 = *(ushort*)(addr+2);	mdsum += t1;
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		t1 = *(ushort*)(addr+4);	mdsum += t2;
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		t2 = *(ushort*)(addr+6);	mdsum += t1;
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		t1 = *(ushort*)(addr+8);	mdsum += t2;
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		t2 = *(ushort*)(addr+10);	mdsum += t1;
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		t1 = *(ushort*)(addr+12);	mdsum += t2;
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		t2 = *(ushort*)(addr+14);	mdsum += t1;
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		mdsum += t2;
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		len -= 16;
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		addr += 16;
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	}
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	while(len >= 2) {
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		mdsum += *(ushort*)addr;
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		len -= 2;
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		addr += 2;
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	}
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	if(x) {
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		if(len)
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			losum += addr[0];
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		if(LITTLE)
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			losum += mdsum;
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		else
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			hisum += mdsum;
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	} else {
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		if(len)
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			hisum += addr[0];
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		if(LITTLE)
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			hisum += mdsum;
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		else
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			losum += mdsum;
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	}
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	losum += hisum >> 8;
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	losum += (hisum & 0xff) << 8;
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	while(hisum = losum>>16)
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		losum = hisum + (losum & 0xffff);
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	return losum & 0xffff;
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}
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ushort
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ptclcsum(Block *bp, int offset, int len)
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{
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	uchar *addr;
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	ulong losum, hisum;
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	ushort csum;
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	int odd, blen, x;
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	/* Correct to front of data area */
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	while(bp != nil && offset && offset >= BLEN(bp)) {
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		offset -= BLEN(bp);
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		bp = bp->next;
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	}
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	if(bp == nil)
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		return 0;
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	addr = bp->rptr + offset;
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	blen = BLEN(bp) - offset;
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	if(bp->next == nil) {
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		if(blen < len)
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			len = blen;
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		return ~ptclbsum(addr, len) & 0xffff;
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	}
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	losum = 0;
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	hisum = 0;
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	odd = 0;
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	while(len) {
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		x = blen;
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		if(len < x)
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			x = len;
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		csum = ptclbsum(addr, x);
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		if(odd)
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			hisum += csum;
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		else
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			losum += csum;
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		odd = (odd+x) & 1;
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		len -= x;
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		bp = bp->next;
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		if(bp == nil)
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			break;
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		blen = BLEN(bp);
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		addr = bp->rptr;
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	}
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	losum += hisum>>8;
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	losum += (hisum&0xff)<<8;
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	while((csum = losum>>16) != 0)
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		losum = csum + (losum & 0xffff);
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	return ~losum & 0xffff;
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}
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ushort
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ipcsum(uchar *addr)
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{
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	int len;
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	ulong sum;
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	sum = 0;
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	len = (addr[0]&0xf)<<2;
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	while(len > 0) {
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		sum += (addr[0]<<8) | addr[1] ;
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		len -= 2;
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		addr += 2;
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	}
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	sum = (sum & 0xffff) + (sum >> 16);
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	sum = (sum & 0xffff) + (sum >> 16);
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	return (sum^0xffff);
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}