2 * Copyright (c) 2008, 2009, 2010, 2011, 2013, 2015 Nicira, Inc.
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:
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
19 #include "unaligned.h"
20 #include <netinet/in.h>
23 /* Returns the IP checksum of the 'n' bytes in 'data'.
25 * The return value has the same endianness as the data. That is, if 'data'
26 * consists of a packet in network byte order, then the return value is a value
27 * in network byte order, and if 'data' consists of a data structure in host
28 * byte order, then the return value is in host byte order. */
30 csum(const void *data
, size_t n
)
32 return csum_finish(csum_continue(0, data
, n
));
35 /* Adds the 'n' bytes in 'data' to the partial IP checksum 'partial' and
36 * returns the updated checksum. (To start a new checksum, pass 0 for
37 * 'partial'. To obtain the finished checksum, pass the return value to
40 csum_continue(uint32_t partial
, const void *data_
, size_t n
)
42 const ovs_be16
*data
= data_
;
44 for (; n
> 1; n
-= 2, data
++) {
45 partial
= csum_add16(partial
, get_unaligned_be16(data
));
48 #ifdef WORDS_BIGENDIAN
49 partial
+= (*(uint8_t *) data
) << 8;
51 partial
+= *(uint8_t *) data
;
57 /* Returns the IP checksum corresponding to 'partial', which is a value updated
58 * by some combination of csum_add16(), csum_add32(), and csum_continue().
60 * The return value has the same endianness as the checksummed data. That is,
61 * if the data consist of a packet in network byte order, then the return value
62 * is a value in network byte order, and if the data are a data structure in
63 * host byte order, then the return value is in host byte order. */
65 csum_finish(uint32_t partial
)
67 while (partial
>> 16) {
68 partial
= (partial
& 0xffff) + (partial
>> 16);
73 /* Returns the new checksum for a packet in which the checksum field previously
74 * contained 'old_csum' and in which a field that contained 'old_u16' was
75 * changed to contain 'new_u16'. */
77 recalc_csum16(ovs_be16 old_csum
, ovs_be16 old_u16
, ovs_be16 new_u16
)
79 /* Ones-complement arithmetic is endian-independent, so this code does not
80 * use htons() or ntohs().
82 * See RFC 1624 for formula and explanation. */
83 uint16_t hc_complement
= ~old_csum
;
84 uint16_t m_complement
= ~old_u16
;
85 uint16_t m_prime
= new_u16
;
86 uint32_t sum
= hc_complement
+ m_complement
+ m_prime
;
87 return csum_finish(sum
);
90 /* Returns the new checksum for a packet in which the checksum field previously
91 * contained 'old_csum' and in which a field that contained 'old_u32' was
92 * changed to contain 'new_u32'. */
94 recalc_csum32(ovs_be16 old_csum
, ovs_be32 old_u32
, ovs_be32 new_u32
)
96 return recalc_csum16(recalc_csum16(old_csum
, old_u32
, new_u32
),
97 old_u32
>> 16, new_u32
>> 16);
100 /* Returns the new checksum for a packet in which the checksum field previously
101 * contained 'old_csum' and in which a field that contained the 6 bytes at
102 * 'old_mac' was changed to contain the 6 bytes at 'new_mac'. */
104 recalc_csum48(ovs_be16 old_csum
, const struct eth_addr old_mac
,
105 const struct eth_addr new_mac
)
107 ovs_be16 new_csum
= old_csum
;
109 for (int i
= 0; i
< 3; ++i
) {
110 new_csum
= recalc_csum16(new_csum
, old_mac
.be16
[i
], new_mac
.be16
[i
]);
116 /* Returns the new checksum for a packet in which the checksum field previously
117 * contained 'old_csum' and in which a field that contained 'old_u32[4]' was
118 * changed to contain 'new_u32[4]'. */
120 recalc_csum128(ovs_be16 old_csum
, ovs_16aligned_be32 old_u32
[4],
121 const struct in6_addr
*new_in6
)
123 ovs_be16 new_csum
= old_csum
;
126 memcpy(new_u32
, new_in6
, sizeof new_u32
);
128 const ovs_be32
*new_u32
= new_in6
->s6_addr32
;
132 for (i
= 0; i
< 4; ++i
) {
133 new_csum
= recalc_csum32(new_csum
,
134 get_16aligned_be32(&old_u32
[i
]), new_u32
[i
]);
138 #else /* __CHECKER__ */
139 /* Making sparse happy with these functions also makes them unreadable, so
140 * don't bother to show it their implementations. */