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(x: 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(buff: iph, len: 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(x: s); |
171 | } |
172 | EXPORT_SYMBOL(csum_tcpudp_nofold); |
173 | #endif |
174 | |