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, <jorge@laser.satlink.net>
11 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
12 * Tom May, <ftom@netcom.com>
13 * Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de>
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
37 static inline unsigned short from32to16(unsigned int x)
38 {
39 /* add up 16-bit and 16-bit for 16+c bit */
40 x = (x & 0xffff) + (x >> 16);
41 /* add up carry.. */
42 x = (x & 0xffff) + (x >> 16);
43 return x;
44 }
45
46 static unsigned int do_csum(const unsigned char *buff, int len)
47 {
48 int odd;
49 unsigned int result = 0;
50
51 if (len <= 0)
52 goto out;
53 odd = 1 & (unsigned long) buff;
54 if (odd) {
55 #ifdef __LITTLE_ENDIAN
56 result += (*buff << 8);
57 #else
58 result = *buff;
59 #endif
60 len--;
61 buff++;
62 }
63 if (len >= 2) {
64 if (2 & (unsigned long) buff) {
65 result += *(unsigned short *) buff;
66 len -= 2;
67 buff += 2;
68 }
69 if (len >= 4) {
70 const unsigned char *end = buff + ((unsigned)len & ~3);
71 unsigned int carry = 0;
72 do {
73 unsigned int w = *(unsigned int *) buff;
74 buff += 4;
75 result += carry;
76 result += w;
77 carry = (w > result);
78 } while (buff < end);
79 result += carry;
80 result = (result & 0xffff) + (result >> 16);
81 }
82 if (len & 2) {
83 result += *(unsigned short *) buff;
84 buff += 2;
85 }
86 }
87 if (len & 1)
88 #ifdef __LITTLE_ENDIAN
89 result += *buff;
90 #else
91 result += (*buff << 8);
92 #endif
93 result = from32to16(result);
94 if (odd)
95 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
96 out:
97 return result;
98 }
99 #endif
100
101 #ifndef ip_fast_csum
102 /*
103 * This is a version of ip_compute_csum() optimized for IP headers,
104 * which always checksum on 4 octet boundaries.
105 */
106 __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
107 {
108 return (__force __sum16)~do_csum(iph, ihl*4);
109 }
110 EXPORT_SYMBOL(ip_fast_csum);
111 #endif
112
113 /*
114 * computes the checksum of a memory block at buff, length len,
115 * and adds in "sum" (32-bit)
116 *
117 * returns a 32-bit number suitable for feeding into itself
118 * or csum_tcpudp_magic
119 *
120 * this function must be called with even lengths, except
121 * for the last fragment, which may be odd
122 *
123 * it's best to have buff aligned on a 32-bit boundary
124 */
125 __wsum csum_partial(const void *buff, int len, __wsum wsum)
126 {
127 unsigned int sum = (__force unsigned int)wsum;
128 unsigned int result = do_csum(buff, len);
129
130 /* add in old sum, and carry.. */
131 result += sum;
132 if (sum > result)
133 result += 1;
134 return (__force __wsum)result;
135 }
136 EXPORT_SYMBOL(csum_partial);
137
138 /*
139 * this routine is used for miscellaneous IP-like checksums, mainly
140 * in icmp.c
141 */
142 __sum16 ip_compute_csum(const void *buff, int len)
143 {
144 return (__force __sum16)~do_csum(buff, len);
145 }
146 EXPORT_SYMBOL(ip_compute_csum);
147
148 #ifndef csum_tcpudp_nofold
149 static inline u32 from64to32(u64 x)
150 {
151 /* add up 32-bit and 32-bit for 32+c bit */
152 x = (x & 0xffffffff) + (x >> 32);
153 /* add up carry.. */
154 x = (x & 0xffffffff) + (x >> 32);
155 return (u32)x;
156 }
157
158 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
159 __u32 len, __u8 proto, __wsum sum)
160 {
161 unsigned long long s = (__force u32)sum;
162
163 s += (__force u32)saddr;
164 s += (__force u32)daddr;
165 #ifdef __BIG_ENDIAN
166 s += proto + len;
167 #else
168 s += (proto + len) << 8;
169 #endif
170 return (__force __wsum)from64to32(s);
171 }
172 EXPORT_SYMBOL(csum_tcpudp_nofold);
173 #endif
174
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