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1da177e4 LT |
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 | ||
18 | static inline unsigned short | |
19 | from64to16 (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 | unsigned short int | |
37 | csum_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 | ||
44 | EXPORT_SYMBOL(csum_tcpudp_magic); | |
45 | ||
46 | unsigned int | |
47 | csum_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 | ||
64 | extern 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 | unsigned int | |
79 | csum_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 | ||
90 | EXPORT_SYMBOL(csum_partial); | |
91 | ||
92 | /* | |
93 | * this routine is used for miscellaneous IP-like checksums, mainly | |
94 | * in icmp.c | |
95 | */ | |
96 | unsigned short | |
97 | ip_compute_csum (unsigned char * buff, int len) | |
98 | { | |
99 | return ~do_csum(buff,len); | |
100 | } | |
101 | ||
102 | EXPORT_SYMBOL(ip_compute_csum); |