1/*
2 * Network checksum routines
3 *
4 * Copyright (C) 1999, 2003 Hewlett-Packard Co
5 *	Stephane Eranian <eranian@hpl.hp.com>
6 *
7 * Most of the code coming from arch/alpha/lib/checksum.c
8 *
9 * This file contains network checksum routines that are better done
10 * in an architecture-specific manner due to speed..
11 */
12
13#include <linux/module.h>
14#include <linux/string.h>
15
16#include <asm/byteorder.h>
17
18static inline unsigned short
19from64to16 (unsigned long x)
20{
21	/* add up 32-bit words for 33 bits */
22	x = (x & 0xffffffff) + (x >> 32);
23	/* add up 16-bit and 17-bit words for 17+c bits */
24	x = (x & 0xffff) + (x >> 16);
25	/* add up 16-bit and 2-bit for 16+c bit */
26	x = (x & 0xffff) + (x >> 16);
27	/* add up carry.. */
28	x = (x & 0xffff) + (x >> 16);
29	return x;
30}
31
32/*
33 * computes the checksum of the TCP/UDP pseudo-header
34 * returns a 16-bit checksum, already complemented.
35 */
36__sum16
37csum_tcpudp_magic (__be32 saddr, __be32 daddr, unsigned short len,
38		   unsigned short proto, __wsum sum)
39{
40	return (__force __sum16)~from64to16(
41		(__force u64)saddr + (__force u64)daddr +
42		(__force u64)sum + ((len + proto) << 8));
43}
44
45EXPORT_SYMBOL(csum_tcpudp_magic);
46
47__wsum
48csum_tcpudp_nofold (__be32 saddr, __be32 daddr, unsigned short len,
49		    unsigned short proto, __wsum sum)
50{
51	unsigned long result;
52
53	result = (__force u64)saddr + (__force u64)daddr +
54		 (__force u64)sum + ((len + proto) << 8);
55
56	/* Fold down to 32-bits so we don't lose in the typedef-less network stack.  */
57	/* 64 to 33 */
58	result = (result & 0xffffffff) + (result >> 32);
59	/* 33 to 32 */
60	result = (result & 0xffffffff) + (result >> 32);
61	return (__force __wsum)result;
62}
63
64extern unsigned long do_csum (const unsigned char *, long);
65
66/*
67 * computes the checksum of a memory block at buff, length len,
68 * and adds in "sum" (32-bit)
69 *
70 * returns a 32-bit number suitable for feeding into itself
71 * or csum_tcpudp_magic
72 *
73 * this function must be called with even lengths, except
74 * for the last fragment, which may be odd
75 *
76 * it's best to have buff aligned on a 32-bit boundary
77 */
78__wsum csum_partial(const void *buff, int len, __wsum sum)
79{
80	u64 result = do_csum(buff, len);
81
82	/* add in old sum, and carry.. */
83	result += (__force u32)sum;
84	/* 32+c bits -> 32 bits */
85	result = (result & 0xffffffff) + (result >> 32);
86	return (__force __wsum)result;
87}
88
89EXPORT_SYMBOL(csum_partial);
90
91/*
92 * this routine is used for miscellaneous IP-like checksums, mainly
93 * in icmp.c
94 */
95__sum16 ip_compute_csum (const void *buff, int len)
96{
97	return (__force __sum16)~do_csum(buff,len);
98}
99
100EXPORT_SYMBOL(ip_compute_csum);
101