KVM: Update headers (except HIOR mess)
[qemu.git] / net / checksum.c
1 /*
2 * IP checksumming functions.
3 * (c) 2008 Gerd Hoffmann <kraxel@redhat.com>
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; under version 2 of the License.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, see <http://www.gnu.org/licenses/>.
16 *
17 * Contributions after 2012-01-13 are licensed under the terms of the
18 * GNU GPL, version 2 or (at your option) any later version.
19 */
20
21 #include "net/checksum.h"
22
23 #define PROTO_TCP 6
24 #define PROTO_UDP 17
25
26 uint32_t net_checksum_add(int len, uint8_t *buf)
27 {
28 uint32_t sum = 0;
29 int i;
30
31 for (i = 0; i < len; i++) {
32 if (i & 1)
33 sum += (uint32_t)buf[i];
34 else
35 sum += (uint32_t)buf[i] << 8;
36 }
37 return sum;
38 }
39
40 uint16_t net_checksum_finish(uint32_t sum)
41 {
42 while (sum>>16)
43 sum = (sum & 0xFFFF)+(sum >> 16);
44 return ~sum;
45 }
46
47 uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
48 uint8_t *addrs, uint8_t *buf)
49 {
50 uint32_t sum = 0;
51
52 sum += net_checksum_add(length, buf); // payload
53 sum += net_checksum_add(8, addrs); // src + dst address
54 sum += proto + length; // protocol & length
55 return net_checksum_finish(sum);
56 }
57
58 void net_checksum_calculate(uint8_t *data, int length)
59 {
60 int hlen, plen, proto, csum_offset;
61 uint16_t csum;
62
63 if ((data[14] & 0xf0) != 0x40)
64 return; /* not IPv4 */
65 hlen = (data[14] & 0x0f) * 4;
66 plen = (data[16] << 8 | data[17]) - hlen;
67 proto = data[23];
68
69 switch (proto) {
70 case PROTO_TCP:
71 csum_offset = 16;
72 break;
73 case PROTO_UDP:
74 csum_offset = 6;
75 break;
76 default:
77 return;
78 }
79
80 if (plen < csum_offset+2)
81 return;
82
83 data[14+hlen+csum_offset] = 0;
84 data[14+hlen+csum_offset+1] = 0;
85 csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen);
86 data[14+hlen+csum_offset] = csum >> 8;
87 data[14+hlen+csum_offset+1] = csum & 0xff;
88 }