Add an inline function to compute the common-case IP header checksum.

1 files changed, 76 insertions, 0 deletions

diff --git a/sys/i386/include/in_cksum.h b/sys/i386/include/in_cksum.h
new file mode 100644
index 0000000..8142e6f
--- /dev/null
+++ b/sys/i386/include/in_cksum.h
@@ -0,0 +1,76 @@
+/*-
+ * Copyright (c) 1990 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	from tahoe:	in_cksum.c	1.2	86/01/05
+ *	from:		@(#)in_cksum.c	1.3 (Berkeley) 1/19/91
+ *	from: Id: in_cksum.c,v 1.8 1995/12/03 18:35:19 bde Exp
+ *	$Id$
+ */
+
+#ifndef _MACHINE_IN_CKSUM_H_
+#define	_MACHINE_IN_CKSUM_H_	1
+
+#include <sys/cdefs.h>
+
+/*
+ * It it useful to have an Internet checksum routine which is inlineable
+ * and optimized specifically for the task of computing IP header checksums
+ * in the normal case (where there are no options and the header length is
+ * therefore always exactly five 32-bit words.
+ */
+#ifdef __GNUC__
+static __inline u_int
+in_cksum_hdr(const struct ip *ip)
+{
+	register u_int sum = 0;
+		    
+#define ADD(n)	__asm("addl " #n "(%2), %0" : "=r" (sum) : "0" (sum), "r" (ip))
+#define ADDC(n)	__asm("adcl " #n "(%2), %0" : "=r" (sum) : "0" (sum), "r" (ip))
+#define MOP	__asm("adcl         $0, %0" : "=r" (sum) : "0" (sum))
+
+	ADD(0);
+	ADDC(4);
+	ADDC(8);
+	ADDC(12);
+	ADDC(16);
+	MOP;
+	sum = (sum & 0xffff) + (sum >> 16);
+	if (sum > 0xffff)
+		sum -= 0xffff;
+
+	return ~sum & 0xffff;
+}
+#else
+u_int in_cksum_hdr __P((const struct ip *));
+#endif
+
+#endif /* _MACHINE_IN_CKSUM_H_ */