1 /* Copyright (c) 2008 The Board of Trustees of The Leland Stanford
4 * We are making the OpenFlow specification and associated documentation
5 * (Software) available for public use and benefit with the expectation
6 * that others will use, modify and enhance the Software and contribute
7 * those enhancements back to the community. However, since we would
8 * like to make the Software available for broadest use, with as few
9 * restrictions as possible permission is hereby granted, free of
10 * charge, to any person obtaining a copy of this Software to deal in
11 * the Software under the copyrights without restriction, including
12 * without limitation the rights to use, copy, modify, merge, publish,
13 * distribute, sublicense, and/or sell copies of the Software, and to
14 * permit persons to whom the Software is furnished to do so, subject to
15 * the following conditions:
17 * The above copyright notice and this permission notice shall be
18 * included in all copies or substantial portions of the Software.
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
24 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
25 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
26 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
29 * The name and trademarks of copyright holder(s) may NOT be used in
30 * advertising or publicity pertaining to the Software or any
31 * derivatives without specific, written prior permission.
36 /* Returns the IP checksum of the 'n' bytes in 'data'. */
38 csum(const void *data, size_t n)
40 return csum_finish(csum_continue(0, data, n));
43 /* Adds the 16 bits in 'new' to the partial IP checksum 'partial' and returns
44 * the updated checksum. (To start a new checksum, pass 0 for 'partial'. To
45 * obtain the finished checksum, pass the return value to csum_finish().) */
47 csum_add16(uint32_t partial, uint16_t new)
52 /* Adds the 32 bits in 'new' to the partial IP checksum 'partial' and returns
53 * the updated checksum. (To start a new checksum, pass 0 for 'partial'. To
54 * obtain the finished checksum, pass the return value to csum_finish().) */
56 csum_add32(uint32_t partial, uint32_t new)
58 return partial + (new >> 16) + (new & 0xffff);
62 /* Adds the 'n' bytes in 'data' to the partial IP checksum 'partial' and
63 * returns the updated checksum. (To start a new checksum, pass 0 for
64 * 'partial'. To obtain the finished checksum, pass the return value to
67 csum_continue(uint32_t partial, const void *data_, size_t n)
69 const uint16_t *data = data_;
71 for (; n > 1; n -= 2) {
72 partial = csum_add16(partial, *data++);
75 partial += *(uint8_t *) data;
80 /* Returns the IP checksum corresponding to 'partial', which is a value updated
81 * by some combination of csum_add16(), csum_add32(), and csum_continue(). */
83 csum_finish(uint32_t partial)
85 return ~((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(uint16_t old_csum, uint16_t old_u16, uint16_t 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 uint16_t hc_prime_complement = sum + (sum >> 16);
103 return ~hc_prime_complement;
106 /* Returns the new checksum for a packet in which the checksum field previously
107 * contained 'old_csum' and in which a field that contained 'old_u32' was
108 * changed to contain 'new_u32'. */
110 recalc_csum32(uint16_t old_csum, uint32_t old_u32, uint32_t new_u32)
112 return recalc_csum16(recalc_csum16(old_csum, old_u32, new_u32),
113 old_u32 >> 16, new_u32 >> 16);