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Linux kernel mirror (for testing)
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linux
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 */
36unsigned short int
37csum_tcpudp_magic (unsigned long saddr, unsigned long daddr, unsigned short len,
38 unsigned short proto, unsigned int sum)
39{
40 return ~from64to16(saddr + daddr + sum + ((unsigned long) ntohs(len) << 16) +
41 ((unsigned long) proto << 8));
42}
43
44EXPORT_SYMBOL(csum_tcpudp_magic);
45
46unsigned int
47csum_tcpudp_nofold (unsigned long saddr, unsigned long daddr, unsigned short len,
48 unsigned short proto, unsigned int sum)
49{
50 unsigned long result;
51
52 result = (saddr + daddr + sum +
53 ((unsigned long) ntohs(len) << 16) +
54 ((unsigned long) 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 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 */
78unsigned int
79csum_partial (const unsigned char * buff, int len, unsigned int sum)
80{
81 unsigned long result = do_csum(buff, len);
82
83 /* add in old sum, and carry.. */
84 result += sum;
85 /* 32+c bits -> 32 bits */
86 result = (result & 0xffffffff) + (result >> 32);
87 return result;
88}
89
90EXPORT_SYMBOL(csum_partial);
91
92/*
93 * this routine is used for miscellaneous IP-like checksums, mainly
94 * in icmp.c
95 */
96unsigned short
97ip_compute_csum (unsigned char * buff, int len)
98{
99 return ~do_csum(buff,len);
100}
101
102EXPORT_SYMBOL(ip_compute_csum);