qdev: remove baked in notion of aliases (v2)
[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 or later 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
18 #include "net/checksum.h"
19
20 #define PROTO_TCP 6
21 #define PROTO_UDP 17
22
23 uint32_t net_checksum_add(int len, uint8_t *buf)
24 {
25 uint32_t sum = 0;
26 int i;
27
28 for (i = 0; i < len; i++) {
29 if (i & 1)
30 sum += (uint32_t)buf[i];
31 else
32 sum += (uint32_t)buf[i] << 8;
33 }
34 return sum;
35 }
36
37 uint16_t net_checksum_finish(uint32_t sum)
38 {
39 while (sum>>16)
40 sum = (sum & 0xFFFF)+(sum >> 16);
41 return ~sum;
42 }
43
44 uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
45 uint8_t *addrs, uint8_t *buf)
46 {
47 uint32_t sum = 0;
48
49 sum += net_checksum_add(length, buf); // payload
50 sum += net_checksum_add(8, addrs); // src + dst address
51 sum += proto + length; // protocol & length
52 return net_checksum_finish(sum);
53 }
54
55 void net_checksum_calculate(uint8_t *data, int length)
56 {
57 int hlen, plen, proto, csum_offset;
58 uint16_t csum;
59
60 if ((data[14] & 0xf0) != 0x40)
61 return; /* not IPv4 */
62 hlen = (data[14] & 0x0f) * 4;
63 plen = (data[16] << 8 | data[17]) - hlen;
64 proto = data[23];
65
66 switch (proto) {
67 case PROTO_TCP:
68 csum_offset = 16;
69 break;
70 case PROTO_UDP:
71 csum_offset = 6;
72 break;
73 default:
74 return;
75 }
76
77 if (plen < csum_offset+2)
78 return;
79
80 data[14+hlen+csum_offset] = 0;
81 data[14+hlen+csum_offset+1] = 0;
82 csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen);
83 data[14+hlen+csum_offset] = csum >> 8;
84 data[14+hlen+csum_offset+1] = csum & 0xff;
85 }