2 * Copyright (c) 2008, 2009, 2010, 2011 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"
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 16 bits in 'new' to the partial IP checksum 'partial' and returns
36 * the updated checksum. (To start a new checksum, pass 0 for 'partial'. To
37 * obtain the finished checksum, pass the return value to csum_finish().) */
39 csum_add16(uint32_t partial, ovs_be16 new)
44 /* Adds the 32 bits in 'new' to the partial IP checksum 'partial' and returns
45 * the updated checksum. (To start a new checksum, pass 0 for 'partial'. To
46 * obtain the finished checksum, pass the return value to csum_finish().) */
48 csum_add32(uint32_t partial, ovs_be32 new)
50 return partial + (new >> 16) + (new & 0xffff);
54 /* Adds the 'n' bytes in 'data' to the partial IP checksum 'partial' and
55 * returns the updated checksum. (To start a new checksum, pass 0 for
56 * 'partial'. To obtain the finished checksum, pass the return value to
59 csum_continue(uint32_t partial, const void *data_, size_t n)
61 const ovs_be16 *data = data_;
63 for (; n > 1; n -= 2, data++) {
64 partial = csum_add16(partial, get_unaligned_be16(data));
67 partial += *(uint8_t *) data;
72 /* Returns the IP checksum corresponding to 'partial', which is a value updated
73 * by some combination of csum_add16(), csum_add32(), and csum_continue().
75 * The return value has the same endianness as the checksummed data. That is,
76 * if the data consist of a packet in network byte order, then the return value
77 * is a value in network byte order, and if the data are a data structure in
78 * host byte order, then the return value is in host byte order. */
80 csum_finish(uint32_t partial)
82 while (partial >> 16) {
83 partial = (partial & 0xffff) + (partial >> 16);
88 /* Returns the new checksum for a packet in which the checksum field previously
89 * contained 'old_csum' and in which a field that contained 'old_u16' was
90 * changed to contain 'new_u16'. */
92 recalc_csum16(ovs_be16 old_csum, ovs_be16 old_u16, ovs_be16 new_u16)
94 /* Ones-complement arithmetic is endian-independent, so this code does not
95 * use htons() or ntohs().
97 * See RFC 1624 for formula and explanation. */
98 uint16_t hc_complement = ~old_csum;
99 uint16_t m_complement = ~old_u16;
100 uint16_t m_prime = new_u16;
101 uint32_t sum = hc_complement + m_complement + m_prime;
102 return csum_finish(sum);
105 /* Returns the new checksum for a packet in which the checksum field previously
106 * contained 'old_csum' and in which a field that contained 'old_u32' was
107 * changed to contain 'new_u32'. */
109 recalc_csum32(ovs_be16 old_csum, ovs_be32 old_u32, ovs_be32 new_u32)
111 return recalc_csum16(recalc_csum16(old_csum, old_u32, new_u32),
112 old_u32 >> 16, new_u32 >> 16);
115 /* Returns the new checksum for a packet in which the checksum field previously
116 * contained 'old_csum' and in which a field that contained 'old_u32[4]' was
117 * changed to contain 'new_u32[4]'. */
119 recalc_csum128(ovs_be16 old_csum, ovs_be32 old_u32[4],
120 const ovs_be32 new_u32[4])
122 ovs_be16 new_csum = old_csum;
125 for (i = 0; i < 4; ++i) {
126 new_csum = recalc_csum32(new_csum, old_u32[i], new_u32[i]);
130 #else /* __CHECKER__ */
131 /* Making sparse happy with these functions also makes them unreadable, so
132 * don't bother to show it their implementations. */