1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * arch/alpha/lib/checksum.c
4 *
5 * This file contains network checksum routines that are better done
6 * in an architecture-specific manner due to speed..
7 * Comments in other versions indicate that the algorithms are from RFC1071
8 *
9 * accelerated versions (and 21264 assembly versions ) contributed by
10 * Rick Gorton <rick.gorton@alpha-processor.com>
11 */
12
13 #include <linux/module.h>
14 #include <linux/string.h>
15 #include <net/checksum.h>
16
17 #include <asm/byteorder.h>
18 #include <asm/checksum.h>
19
20 static inline unsigned short from64to16(unsigned long x)
21 {
22 /* Using extract instructions is a bit more efficient
23 than the original shift/bitmask version. */
24
25 union {
26 unsigned long ul;
27 unsigned int ui[2];
28 unsigned short us[4];
29 } in_v, tmp_v, out_v;
30
31 in_v.ul = x;
32 tmp_v.ul = (unsigned long) in_v.ui[0] + (unsigned long) in_v.ui[1];
33
34 /* Since the bits of tmp_v.sh[3] are going to always be zero,
35 we don't have to bother to add that in. */
36 out_v.ul = (unsigned long) tmp_v.us[0] + (unsigned long) tmp_v.us[1]
37 + (unsigned long) tmp_v.us[2];
38
39 /* Similarly, out_v.us[2] is always zero for the final add. */
40 return out_v.us[0] + out_v.us[1];
41 }
42
43 /*
44 * computes the checksum of the TCP/UDP pseudo-header
45 * returns a 16-bit checksum, already complemented.
46 */
47 __sum16 csum_tcpudp_magic(__be32 saddr, __be32 daddr,
48 __u32 len, __u8 proto, __wsum sum)
49 {
50 return (__force __sum16)~from64to16(
51 (__force u64)saddr + (__force u64)daddr +
52 (__force u64)sum + ((len + proto) << 8));
53 }
54 EXPORT_SYMBOL(csum_tcpudp_magic);
55
56 __wsum csum_tcpudp_nofold(__be32 saddr, __be32 daddr,
57 __u32 len, __u8 proto, __wsum sum)
58 {
59 unsigned long result;
60
61 result = (__force u64)saddr + (__force u64)daddr +
62 (__force u64)sum + ((len + proto) << 8);
63
64 /* Fold down to 32-bits so we don't lose in the typedef-less
65 network stack. */
66 /* 64 to 33 */
67 result = (result & 0xffffffff) + (result >> 32);
68 /* 33 to 32 */
69 result = (result & 0xffffffff) + (result >> 32);
70 return (__force __wsum)result;
71 }
72 EXPORT_SYMBOL(csum_tcpudp_nofold);
73
74 /*
75 * Do a 64-bit checksum on an arbitrary memory area..
76 *
77 * This isn't a great routine, but it's not _horrible_ either. The
78 * inner loop could be unrolled a bit further, and there are better
79 * ways to do the carry, but this is reasonable.
80 */
81 static inline unsigned long do_csum(const unsigned char * buff, int len)
82 {
83 int odd, count;
84 unsigned long result = 0;
85
86 if (len <= 0)
87 goto out;
88 odd = 1 & (unsigned long) buff;
89 if (odd) {
90 result = *buff << 8;
91 len--;
92 buff++;
93 }
94 count = len >> 1; /* nr of 16-bit words.. */
95 if (count) {
96 if (2 & (unsigned long) buff) {
97 result += *(unsigned short *) buff;
98 count--;
99 len -= 2;
100 buff += 2;
101 }
102 count >>= 1; /* nr of 32-bit words.. */
103 if (count) {
104 if (4 & (unsigned long) buff) {
105 result += *(unsigned int *) buff;
106 count--;
107 len -= 4;
108 buff += 4;
109 }
110 count >>= 1; /* nr of 64-bit words.. */
111 if (count) {
112 unsigned long carry = 0;
113 do {
114 unsigned long w = *(unsigned long *) buff;
115 count--;
116 buff += 8;
117 result += carry;
118 result += w;
119 carry = (w > result);
120 } while (count);
121 result += carry;
122 result = (result & 0xffffffff) + (result >> 32);
123 }
124 if (len & 4) {
125 result += *(unsigned int *) buff;
126 buff += 4;
127 }
128 }
129 if (len & 2) {
130 result += *(unsigned short *) buff;
131 buff += 2;
132 }
133 }
134 if (len & 1)
135 result += *buff;
136 result = from64to16(result);
137 if (odd)
138 result = ((result >> 8) & 0xff) | ((result & 0xff) << 8);
139 out:
140 return result;
141 }
142
143 /*
144 * This is a version of ip_compute_csum() optimized for IP headers,
145 * which always checksum on 4 octet boundaries.
146 */
147 __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
148 {
149 return (__force __sum16)~do_csum(iph,ihl*4);
150 }
151 EXPORT_SYMBOL(ip_fast_csum);
152
153 /*
154 * computes the checksum of a memory block at buff, length len,
155 * and adds in "sum" (32-bit)
156 *
157 * returns a 32-bit number suitable for feeding into itself
158 * or csum_tcpudp_magic
159 *
160 * this function must be called with even lengths, except
161 * for the last fragment, which may be odd
162 *
163 * it's best to have buff aligned on a 32-bit boundary
164 */
165 __wsum csum_partial(const void *buff, int len, __wsum sum)
166 {
167 unsigned long result = do_csum(buff, len);
168
169 /* add in old sum, and carry.. */
170 result += (__force u32)sum;
171 /* 32+c bits -> 32 bits */
172 result = (result & 0xffffffff) + (result >> 32);
173 return (__force __wsum)result;
174 }
175
176 EXPORT_SYMBOL(csum_partial);
177
178 /*
179 * this routine is used for miscellaneous IP-like checksums, mainly
180 * in icmp.c
181 */
182 __sum16 ip_compute_csum(const void *buff, int len)
183 {
184 return (__force __sum16)~from64to16(do_csum(buff,len));
185 }
186 EXPORT_SYMBOL(ip_compute_csum);
187
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.