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1 | /* | |
2 | * Copyright (c) 2008, 2009, 2010, 2011, 2013, 2015 Nicira, Inc. | |
3 | * | |
4 | * Licensed under the Apache License, Version 2.0 (the "License"); | |
5 | * you may not use this file except in compliance with the License. | |
6 | * You may obtain a copy of the License at: | |
7 | * | |
8 | * http://www.apache.org/licenses/LICENSE-2.0 | |
9 | * | |
10 | * Unless required by applicable law or agreed to in writing, software | |
11 | * distributed under the License is distributed on an "AS IS" BASIS, | |
12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
13 | * See the License for the specific language governing permissions and | |
14 | * limitations under the License. | |
15 | */ | |
16 | ||
17 | #include <config.h> | |
18 | #include "csum.h" | |
19 | #include "unaligned.h" | |
20 | #include <sys/types.h> | |
21 | #include <netinet/in.h> | |
22 | ||
23 | #ifndef __CHECKER__ | |
24 | /* Returns the IP checksum of the 'n' bytes in 'data'. | |
25 | * | |
26 | * The return value has the same endianness as the data. That is, if 'data' | |
27 | * consists of a packet in network byte order, then the return value is a value | |
28 | * in network byte order, and if 'data' consists of a data structure in host | |
29 | * byte order, then the return value is in host byte order. */ | |
30 | ovs_be16 | |
31 | csum(const void *data, size_t n) | |
32 | { | |
33 | return csum_finish(csum_continue(0, data, n)); | |
34 | } | |
35 | ||
36 | /* Adds the 'n' bytes in 'data' to the partial IP checksum 'partial' and | |
37 | * returns the updated checksum. (To start a new checksum, pass 0 for | |
38 | * 'partial'. To obtain the finished checksum, pass the return value to | |
39 | * csum_finish().) */ | |
40 | uint32_t | |
41 | csum_continue(uint32_t partial, const void *data_, size_t n) | |
42 | { | |
43 | const ovs_be16 *data = data_; | |
44 | ||
45 | for (; n > 1; n -= 2, data++) { | |
46 | partial = csum_add16(partial, get_unaligned_be16(data)); | |
47 | } | |
48 | if (n) { | |
49 | #ifdef WORDS_BIGENDIAN | |
50 | partial += (*(uint8_t *) data) << 8; | |
51 | #else | |
52 | partial += *(uint8_t *) data; | |
53 | #endif | |
54 | } | |
55 | return partial; | |
56 | } | |
57 | ||
58 | /* Returns the IP checksum corresponding to 'partial', which is a value updated | |
59 | * by some combination of csum_add16(), csum_add32(), and csum_continue(). | |
60 | * | |
61 | * The return value has the same endianness as the checksummed data. That is, | |
62 | * if the data consist of a packet in network byte order, then the return value | |
63 | * is a value in network byte order, and if the data are a data structure in | |
64 | * host byte order, then the return value is in host byte order. */ | |
65 | ovs_be16 | |
66 | csum_finish(uint32_t partial) | |
67 | { | |
68 | while (partial >> 16) { | |
69 | partial = (partial & 0xffff) + (partial >> 16); | |
70 | } | |
71 | return ~partial; | |
72 | } | |
73 | ||
74 | /* Returns the new checksum for a packet in which the checksum field previously | |
75 | * contained 'old_csum' and in which a field that contained 'old_u16' was | |
76 | * changed to contain 'new_u16'. */ | |
77 | ovs_be16 | |
78 | recalc_csum16(ovs_be16 old_csum, ovs_be16 old_u16, ovs_be16 new_u16) | |
79 | { | |
80 | /* Ones-complement arithmetic is endian-independent, so this code does not | |
81 | * use htons() or ntohs(). | |
82 | * | |
83 | * See RFC 1624 for formula and explanation. */ | |
84 | uint16_t hc_complement = ~old_csum; | |
85 | uint16_t m_complement = ~old_u16; | |
86 | uint16_t m_prime = new_u16; | |
87 | uint32_t sum = hc_complement + m_complement + m_prime; | |
88 | return csum_finish(sum); | |
89 | } | |
90 | ||
91 | /* Returns the new checksum for a packet in which the checksum field previously | |
92 | * contained 'old_csum' and in which a field that contained 'old_u32' was | |
93 | * changed to contain 'new_u32'. */ | |
94 | ovs_be16 | |
95 | recalc_csum32(ovs_be16 old_csum, ovs_be32 old_u32, ovs_be32 new_u32) | |
96 | { | |
97 | return recalc_csum16(recalc_csum16(old_csum, old_u32, new_u32), | |
98 | old_u32 >> 16, new_u32 >> 16); | |
99 | } | |
100 | ||
101 | /* Returns the new checksum for a packet in which the checksum field previously | |
102 | * contained 'old_csum' and in which a field that contained the 6 bytes at | |
103 | * 'old_mac' was changed to contain the 6 bytes at 'new_mac'. */ | |
104 | ovs_be16 | |
105 | recalc_csum48(ovs_be16 old_csum, const struct eth_addr old_mac, | |
106 | const struct eth_addr new_mac) | |
107 | { | |
108 | ovs_be16 new_csum = old_csum; | |
109 | ||
110 | for (int i = 0; i < 3; ++i) { | |
111 | new_csum = recalc_csum16(new_csum, old_mac.be16[i], new_mac.be16[i]); | |
112 | } | |
113 | ||
114 | return new_csum; | |
115 | } | |
116 | ||
117 | /* Returns the new checksum for a packet in which the checksum field previously | |
118 | * contained 'old_csum' and in which a field that contained 'old_u32[4]' was | |
119 | * changed to contain 'new_u32[4]'. */ | |
120 | ovs_be16 | |
121 | recalc_csum128(ovs_be16 old_csum, ovs_16aligned_be32 old_u32[4], | |
122 | const struct in6_addr *new_in6) | |
123 | { | |
124 | ovs_be16 new_csum = old_csum; | |
125 | #ifndef s6_addr32 | |
126 | ovs_be32 new_u32[4]; | |
127 | memcpy(new_u32, new_in6, sizeof new_u32); | |
128 | #else | |
129 | const ovs_be32 *new_u32 = new_in6->s6_addr32; | |
130 | #endif | |
131 | int i; | |
132 | ||
133 | for (i = 0; i < 4; ++i) { | |
134 | new_csum = recalc_csum32(new_csum, | |
135 | get_16aligned_be32(&old_u32[i]), new_u32[i]); | |
136 | } | |
137 | return new_csum; | |
138 | } | |
139 | #else /* __CHECKER__ */ | |
140 | /* Making sparse happy with these functions also makes them unreadable, so | |
141 | * don't bother to show it their implementations. */ | |
142 | #endif |