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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *
4 * INET An implementation of the TCP/IP protocol suite for the LINUX
5 * operating system. INET is implemented using the BSD Socket
6 * interface as the means of communication with the user level.
7 *
8 * IP/TCP/UDP checksumming routines
9 *
10 * Authors: Jorge Cwik, <[email protected]>
11 * Arnt Gulbrandsen, <[email protected]>
12 * Tom May, <[email protected]>
13 * Andreas Schwab, <[email protected]>
14 * Lots of code moved from tcp.c and ip.c; see those files
15 * for more names.
16 *
17 * 03/02/96 Jes Sorensen, Andreas Schwab, Roman Hodek:
18 * Fixed some nasty bugs, causing some horrible crashes.
19 * A: At some points, the sum (%0) was used as
20 * length-counter instead of the length counter
21 * (%1). Thanks to Roman Hodek for pointing this out.
22 * B: GCC seems to mess up if one uses too many
23 * data-registers to hold input values and one tries to
24 * specify d0 and d1 as scratch registers. Letting gcc
25 * choose these registers itself solves the problem.
26 */
27
28/* Revised by Kenneth Albanowski for m68knommu. Basic problem: unaligned access
29 kills, so most of the assembly has to go. */
30
31#include <linux/export.h>
32#include <net/checksum.h>
33
34#include <asm/byteorder.h>
35
36#ifndef do_csum
37static unsigned int do_csum(const unsigned char *buff, int len)
38{
39 int odd;
40 unsigned int result = 0;
41
42 if (len <= 0)
43 goto out;
44 odd = 1 & (unsigned long) buff;
45 if (odd) {
46#ifdef __LITTLE_ENDIAN
47 result += (*buff << 8);
48#else
49 result = *buff;
50#endif
51 len--;
52 buff++;
53 }
54 if (len >= 2) {
55 if (2 & (unsigned long) buff) {
56 result += *(unsigned short *) buff;
57 len -= 2;
58 buff += 2;
59 }
60 if (len >= 4) {
61 const unsigned char *end = buff + ((unsigned)len & ~3);
62 unsigned int carry = 0;
63 do {
64 unsigned int w = *(unsigned int *) buff;
65 buff += 4;
66 result += carry;
67 result += w;
68 carry = (w > result);
69 } while (buff < end);
70 result += carry;
71 result = (result & 0xffff) + (result >> 16);
72 }
73 if (len & 2) {
74 result += *(unsigned short *) buff;
75 buff += 2;
76 }
77 }
78 if (len & 1)
79#ifdef __LITTLE_ENDIAN
80 result += *buff;
81#else
82 result += (*buff << 8);
83#endif
84 result = csum_from32to16(result);
85 if (odd)
86 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
87out:
88 return result;
89}
90#endif
91
92#ifndef ip_fast_csum
93/*
94 * This is a version of ip_compute_csum() optimized for IP headers,
95 * which always checksum on 4 octet boundaries.
96 */
97__sum16 ip_fast_csum(const void *iph, unsigned int ihl)
98{
99 return (__force __sum16)~do_csum(iph, ihl*4);
100}
101EXPORT_SYMBOL(ip_fast_csum);
102#endif
103
104/*
105 * computes the checksum of a memory block at buff, length len,
106 * and adds in "sum" (32-bit)
107 *
108 * returns a 32-bit number suitable for feeding into itself
109 * or csum_tcpudp_magic
110 *
111 * this function must be called with even lengths, except
112 * for the last fragment, which may be odd
113 *
114 * it's best to have buff aligned on a 32-bit boundary
115 */
116__wsum csum_partial(const void *buff, int len, __wsum wsum)
117{
118 unsigned int sum = (__force unsigned int)wsum;
119 unsigned int result = do_csum(buff, len);
120
121 /* add in old sum, and carry.. */
122 result += sum;
123 if (sum > result)
124 result += 1;
125 return (__force __wsum)result;
126}
127EXPORT_SYMBOL(csum_partial);
128
129/*
130 * this routine is used for miscellaneous IP-like checksums, mainly
131 * in icmp.c
132 */
133__sum16 ip_compute_csum(const void *buff, int len)
134{
135 return (__force __sum16)~do_csum(buff, len);
136}
137EXPORT_SYMBOL(ip_compute_csum);
138
139#ifndef csum_tcpudp_nofold
140static inline u32 from64to32(u64 x)
141{
142 /* add up 32-bit and 32-bit for 32+c bit */
143 x = (x & 0xffffffff) + (x >> 32);
144 /* add up carry.. */
145 x = (x & 0xffffffff) + (x >> 32);
146 return (u32)x;
147}
148
149__wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
150 __u32 len, __u8 proto, __wsum sum)
151{
152 unsigned long long s = (__force u32)sum;
153
154 s += (__force u32)saddr;
155 s += (__force u32)daddr;
156#ifdef __BIG_ENDIAN
157 s += proto + len;
158#else
159 s += (proto + len) << 8;
160#endif
161 return (__force __wsum)from64to32(s);
162}
163EXPORT_SYMBOL(csum_tcpudp_nofold);
164#endif