Merged the IP checksum changes from the skas code.

arch/um/include/sysdep-i386/checksum.h

+/* 
+ * Licensed under the GPL
+ */
+
+#ifndef __UM_SYSDEP_CHECKSUM_H
+#define __UM_SYSDEP_CHECKSUM_H
+
+#include "linux/string.h"
+
+/*
+ * computes the checksum of a memory block at buff, length len,
+ * and adds in "sum" (32-bit)
+ *
+ * returns a 32-bit number suitable for feeding into itself
+ * or csum_tcpudp_magic
+ *
+ * this function must be called with even lengths, except
+ * for the last fragment, which may be odd
+ *
+ * it's best to have buff aligned on a 32-bit boundary
+ */
+unsigned int csum_partial(const unsigned char * buff, int len, 
+			  unsigned int sum);
+
+/*
+ * the same as csum_partial, but copies from src while it
+ * checksums, and handles user-space pointer exceptions correctly, when needed.
+ *
+ * here even more important to align src and dst on a 32-bit (or even
+ * better 64-bit) boundary
+ */
+
+unsigned int csum_partial_copy_to(const char *src, char *dst, int len, 
+				  int sum, int *err_ptr);
+unsigned int csum_partial_copy_from(const char *src, char *dst, int len, 
+				    int sum, int *err_ptr);
+
+/*
+ *	Note: when you get a NULL pointer exception here this means someone
+ *	passed in an incorrect kernel address to one of these functions.
+ *
+ *	If you use these functions directly please don't forget the
+ *	verify_area().
+ */
+
+static __inline__
+unsigned int csum_partial_copy_nocheck(const char *src, char *dst,
+				       int len, int sum)
+{
+	memcpy(dst, src, len);
+	return(csum_partial(dst, len, sum));
+}
+
+static __inline__
+unsigned int csum_partial_copy_from_user(const char *src, char *dst,
+					 int len, int sum, int *err_ptr)
+{
+	return csum_partial_copy_from(src, dst, len, sum, err_ptr);
+}
+
+/*
+ * These are the old (and unsafe) way of doing checksums, a warning message 
+ * will be printed if they are used and an exeption occurs.
+ *
+ * these functions should go away after some time.
+ */
+
+#define csum_partial_copy_fromuser csum_partial_copy_from_user
+unsigned int csum_partial_copy( const char *src, char *dst, int len, int sum);
+
+/*
+ *	This is a version of ip_compute_csum() optimized for IP headers,
+ *	which always checksum on 4 octet boundaries.
+ *
+ *	By Jorge Cwik <jorge@laser.satlink.net>, adapted for linux by
+ *	Arnt Gulbrandsen.
+ */
+static inline unsigned short ip_fast_csum(unsigned char * iph,
+					  unsigned int ihl)
+{
+	unsigned int sum;
+
+	__asm__ __volatile__(
+	    "movl (%1), %0	;\n"
+	    "subl $4, %2	;\n"
+	    "jbe 2f		;\n"
+	    "addl 4(%1), %0	;\n"
+	    "adcl 8(%1), %0	;\n"
+	    "adcl 12(%1), %0	;\n"
+"1:	    adcl 16(%1), %0	;\n"
+	    "lea 4(%1), %1	;\n"
+	    "decl %2		;\n"
+	    "jne 1b		;\n"
+	    "adcl $0, %0	;\n"
+	    "movl %0, %2	;\n"
+	    "shrl $16, %0	;\n"
+	    "addw %w2, %w0	;\n"
+	    "adcl $0, %0	;\n"
+	    "notl %0		;\n"
+"2:				;\n"
+	/* Since the input registers which are loaded with iph and ipl
+	   are modified, we must also specify them as outputs, or gcc
+	   will assume they contain their original values. */
+	: "=r" (sum), "=r" (iph), "=r" (ihl)
+	: "1" (iph), "2" (ihl));
+	return(sum);
+}
+
+/*
+ *	Fold a partial checksum
+ */
+
+static inline unsigned int csum_fold(unsigned int sum)
+{
+	__asm__(
+		"addl %1, %0		;\n"
+		"adcl $0xffff, %0	;\n"
+		: "=r" (sum)
+		: "r" (sum << 16), "0" (sum & 0xffff0000)
+	);
+	return (~sum) >> 16;
+}
+
+static inline unsigned long csum_tcpudp_nofold(unsigned long saddr,
+						   unsigned long daddr,
+						   unsigned short len,
+						   unsigned short proto,
+						   unsigned int sum)
+{
+    __asm__(
+	"addl %1, %0	;\n"
+	"adcl %2, %0	;\n"
+	"adcl %3, %0	;\n"
+	"adcl $0, %0	;\n"
+	: "=r" (sum)
+	: "g" (daddr), "g"(saddr), "g"((ntohs(len)<<16)+proto*256), "0"(sum));
+    return sum;
+}
+
+/*
+ * computes the checksum of the TCP/UDP pseudo-header
+ * returns a 16-bit checksum, already complemented
+ */
+static inline unsigned short int csum_tcpudp_magic(unsigned long saddr,
+						   unsigned long daddr,
+						   unsigned short len,
+						   unsigned short proto,
+						   unsigned int sum)
+{
+	return csum_fold(csum_tcpudp_nofold(saddr,daddr,len,proto,sum));
+}
+
+/*
+ * this routine is used for miscellaneous IP-like checksums, mainly
+ * in icmp.c
+ */
+
+static inline unsigned short ip_compute_csum(unsigned char * buff, int len)
+{
+    return csum_fold (csum_partial(buff, len, 0));
+}
+
+#define _HAVE_ARCH_IPV6_CSUM
+static __inline__ unsigned short int csum_ipv6_magic(struct in6_addr *saddr,
+						     struct in6_addr *daddr,
+						     __u32 len,
+						     unsigned short proto,
+						     unsigned int sum)
+{
+	__asm__(
+		"addl 0(%1), %0		;\n"
+		"adcl 4(%1), %0		;\n"
+		"adcl 8(%1), %0		;\n"
+		"adcl 12(%1), %0	;\n"
+		"adcl 0(%2), %0		;\n"
+		"adcl 4(%2), %0		;\n"
+		"adcl 8(%2), %0		;\n"
+		"adcl 12(%2), %0	;\n"
+		"adcl %3, %0		;\n"
+		"adcl %4, %0		;\n"
+		"adcl $0, %0		;\n"
+		: "=&r" (sum)
+		: "r" (saddr), "r" (daddr),
+		  "r"(htonl(len)), "r"(htonl(proto)), "0"(sum));
+
+	return csum_fold(sum);
+}
+
+/*
+ *	Copy and checksum to user
+ */
+#define HAVE_CSUM_COPY_USER
+static __inline__ unsigned int csum_and_copy_to_user(const char *src, 
+						     char *dst, int len,
+						     int sum, int *err_ptr)
+{
+	if (access_ok(VERIFY_WRITE, dst, len))
+		return(csum_partial_copy_to(src, dst, len, sum, err_ptr));
+
+	if (len)
+		*err_ptr = -EFAULT;
+
+	return -1; /* invalid checksum */
+}
+
+#endif
+
+/*
+ * Overrides for Emacs so that we follow Linus's tabbing style.
+ * Emacs will notice this stuff at the end of the file and automatically
+ * adjust the settings for this buffer only.  This must remain at the end
+ * of the file.
+ * ---------------------------------------------------------------------------
+ * Local variables:
+ * c-file-style: "linux"
+ * End:
+ */

arch/um/kernel/checksum.c

+#include "asm/uaccess.h"
+#include "linux/errno.h"
+
+extern unsigned int arch_csum_partial(const char *buff, int len, int sum);
+
+extern unsigned int csum_partial(char *buff, int len, int sum)
+{
+	return(arch_csum_partial(buff, len, sum));
+}
+
+unsigned int csum_partial_copy_to(const char *src, char *dst, int len, 
+				  int sum, int *err_ptr)
+{
+	if(copy_to_user(dst, src, len)){
+		*err_ptr = -EFAULT;
+		return(-1);
+	}
+
+	return(arch_csum_partial(src, len, sum));
+}
+
+unsigned int csum_partial_copy_from(const char *src, char *dst, int len, 
+				    int sum, int *err_ptr)
+{
+	if(copy_from_user(dst, src, len)){
+		*err_ptr = -EFAULT;
+		return(-1);
+	}
+
+	return(arch_csum_partial(dst, len, sum));
+}
+
+/*
+ * Overrides for Emacs so that we follow Linus's tabbing style.
+ * Emacs will notice this stuff at the end of the file and automatically
+ * adjust the settings for this buffer only.  This must remain at the end
+ * of the file.
+ * ---------------------------------------------------------------------------
+ * Local variables:
+ * c-file-style: "linux"
+ * End:
+ */

arch/um/sys-i386/ksyms.c

@@ -13,4 +13,5 @@ EXPORT_SYMBOL(__down_failed_trylock);
 EXPORT_SYMBOL(__up_wakeup);
 
 /* Networking helper routines. */
-EXPORT_SYMBOL(csum_partial_copy_generic);
+EXPORT_SYMBOL(csum_partial_copy_from);
+EXPORT_SYMBOL(csum_partial_copy_to);

include/asm-um/checksum.h

 #ifndef __UM_CHECKSUM_H
 #define __UM_CHECKSUM_H
 
-#include "asm/arch/checksum.h"
+#include "sysdep/checksum.h"
 
 #endif