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