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Path: utzoo!watmath!clyde!akgua!sdcsvax!sdcrdcf!hplabs!zehntel!ihnp4!inuxc!pur-ee!CS-Mordred!Pucc-H:acg
From: acg@pucc-h (Schwab)
Newsgroups: net.unix-wizards,net.bugs.4bsd
Subject: if_uba.c routines do not handle local net hlen of 0
Message-ID: <729@pucc-h>
Date: Fri, 25-May-84 16:30:58 EDT
Article-I.D.: pucc-h.729
Posted: Fri May 25 16:30:58 1984
Date-Received: Fri, 1-Jun-84 02:39:55 EDT
Organization: Purdue University Computing Center
Lines: 53
Xref: 1387 231

Description:
	If a local network interface has an hlen of 0, the routines
	in if_ubainit() allocate spurious pages and the if_rubaget()
	routine will exchange the wrong page when handling a packet
	greater than 1024 bytes long.
Repeat-By:
	The pcl-11 is such a device.  If you raise the mtu on the
	device from the default 1006 to anything greater than
	1024, your network will be unusable.
Fix:
	The following diff's fix the extraneous page allocations and
	the problems in if_rubaget().

			- Jeff Schwab
			  <jrs@purdue,  ...pur-ee!pucc-h:acg>

---- if_ubainit() ------
  	register caddr_t cp;
  	int i, ncl;
  
+ #ifdef	PUCC
+ 	ncl = clrnd(nmr + (hlen? CLSIZE: 0)) / CLSIZE;
+ #else	PUCC
  	ncl = clrnd(nmr + CLSIZE) / CLSIZE;
+ #endif	PUCC
  	if (ifu->ifu_r.ifrw_addr)
+ #ifdef	PUCC
+ 		cp = ifu->ifu_r.ifrw_addr - (hlen? (CLBYTES - hlen): 0);
+ #else	PUCC
  		cp = ifu->ifu_r.ifrw_addr - (CLBYTES - hlen);
+ #endif	PUCC
  	else {
  		cp = m_clalloc(2 * ncl, MPG_SPACE);
  		if (cp == 0)
  			return (0);
+ #ifdef	PUCC
+ 		ifu->ifu_r.ifrw_addr = cp + (hlen? (CLBYTES - hlen): 0);
+ #else	PUCC
  		ifu->ifu_r.ifrw_addr = cp + CLBYTES - hlen;
+ #endif	PUCC
  		ifu->ifu_w.ifrw_addr = ifu->ifu_r.ifrw_addr + ncl * CLBYTES;
------- if_rubaget() -------
  			ppte = &Mbmap[mtocl(p)*CLSIZE];
  			x = btop(cp - ifu->ifu_r.ifrw_addr);
  			ip = (int *)&ifu->ifu_r.ifrw_mr[x];
+ #ifdef	PUCC
+ 			if (ifu->ifu_hlen == 0) {
+ 				ip--;
+ 			}
+ #endif	PUCC
  			for (i = 0; i < CLSIZE; i++) {
  				struct pte t;
  				t = *ppte; *ppte++ = *cpte; *cpte = t;