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"
22 /* Returns the IP checksum of the 'n' bytes in 'data'.
24 * The return value has the same endianness as the data. That is, if 'data'
25 * consists of a packet in network byte order, then the return value is a value
26 * in network byte order, and if 'data' consists of a data structure in host
27 * byte order, then the return value is in host byte order. */
29 csum(const void *data, size_t n)
31 return csum_finish(csum_continue(0, data, n));
34 /* Adds the 'n' bytes in 'data' to the partial IP checksum 'partial' and
35 * returns the updated checksum. (To start a new checksum, pass 0 for
36 * 'partial'. To obtain the finished checksum, pass the return value to
39 csum_continue(uint32_t partial, const void *data_, size_t n)
41 const ovs_be16 *data = data_;
43 for (; n > 1; n -= 2, data++) {
44 partial = csum_add16(partial, get_unaligned_be16(data));
47 partial += *(uint8_t *) data;
52 /* Returns the IP checksum corresponding to 'partial', which is a value updated
53 * by some combination of csum_add16(), csum_add32(), and csum_continue().
55 * The return value has the same endianness as the checksummed data. That is,
56 * if the data consist of a packet in network byte order, then the return value
57 * is a value in network byte order, and if the data are a data structure in
58 * host byte order, then the return value is in host byte order. */
60 csum_finish(uint32_t partial)
62 while (partial >> 16) {
63 partial = (partial & 0xffff) + (partial >> 16);
68 /* Returns the new checksum for a packet in which the checksum field previously
69 * contained 'old_csum' and in which a field that contained 'old_u16' was
70 * changed to contain 'new_u16'. */
72 recalc_csum16(ovs_be16 old_csum, ovs_be16 old_u16, ovs_be16 new_u16)
74 /* Ones-complement arithmetic is endian-independent, so this code does not
75 * use htons() or ntohs().
77 * See RFC 1624 for formula and explanation. */
78 uint16_t hc_complement = ~old_csum;
79 uint16_t m_complement = ~old_u16;
80 uint16_t m_prime = new_u16;
81 uint32_t sum = hc_complement + m_complement + m_prime;
82 return csum_finish(sum);
85 /* Returns the new checksum for a packet in which the checksum field previously
86 * contained 'old_csum' and in which a field that contained 'old_u32' was
87 * changed to contain 'new_u32'. */
89 recalc_csum32(ovs_be16 old_csum, ovs_be32 old_u32, ovs_be32 new_u32)
91 return recalc_csum16(recalc_csum16(old_csum, old_u32, new_u32),
92 old_u32 >> 16, new_u32 >> 16);
95 /* Returns the new checksum for a packet in which the checksum field previously
96 * contained 'old_csum' and in which a field that contained the 6 bytes at
97 * 'old_mac' was changed to contain the 6 bytes at 'new_mac'. */
99 recalc_csum48(ovs_be16 old_csum, const struct eth_addr old_mac,
100 const struct eth_addr new_mac)
102 ovs_be16 new_csum = old_csum;
104 for (int i = 0; i < 3; ++i) {
105 new_csum = recalc_csum16(new_csum, old_mac.be16[i], new_mac.be16[i]);
111 /* Returns the new checksum for a packet in which the checksum field previously
112 * contained 'old_csum' and in which a field that contained 'old_u32[4]' was
113 * changed to contain 'new_u32[4]'. */
115 recalc_csum128(ovs_be16 old_csum, ovs_16aligned_be32 old_u32[4],
116 const ovs_be32 new_u32[4])
118 ovs_be16 new_csum = old_csum;
121 for (i = 0; i < 4; ++i) {
122 new_csum = recalc_csum32(new_csum,
123 get_16aligned_be32(&old_u32[i]), new_u32[i]);
127 #else /* __CHECKER__ */
128 /* Making sparse happy with these functions also makes them unreadable, so
129 * don't bother to show it their implementations. */