root / net-checksum.c @ 8950a950
History | View | Annotate | Download (2.2 kB)
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 |
|
18 |
#include "hw/hw.h" |
19 |
#include "net.h" |
20 |
|
21 |
#define PROTO_TCP 6 |
22 |
#define PROTO_UDP 17 |
23 |
|
24 |
uint32_t net_checksum_add(int len, uint8_t *buf)
|
25 |
{ |
26 |
uint32_t sum = 0;
|
27 |
int i;
|
28 |
|
29 |
for (i = 0; i < len; i++) { |
30 |
if (i & 1) |
31 |
sum += (uint32_t)buf[i]; |
32 |
else
|
33 |
sum += (uint32_t)buf[i] << 8;
|
34 |
} |
35 |
return sum;
|
36 |
} |
37 |
|
38 |
uint16_t net_checksum_finish(uint32_t sum) |
39 |
{ |
40 |
while (sum>>16) |
41 |
sum = (sum & 0xFFFF)+(sum >> 16); |
42 |
return ~sum;
|
43 |
} |
44 |
|
45 |
uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto, |
46 |
uint8_t *addrs, uint8_t *buf) |
47 |
{ |
48 |
uint32_t sum = 0;
|
49 |
|
50 |
sum += net_checksum_add(length, buf); // payload
|
51 |
sum += net_checksum_add(8, addrs); // src + dst address |
52 |
sum += proto + length; // protocol & length
|
53 |
return net_checksum_finish(sum);
|
54 |
} |
55 |
|
56 |
void net_checksum_calculate(uint8_t *data, int length) |
57 |
{ |
58 |
int hlen, plen, proto, csum_offset;
|
59 |
uint16_t csum; |
60 |
|
61 |
if ((data[14] & 0xf0) != 0x40) |
62 |
return; /* not IPv4 */ |
63 |
hlen = (data[14] & 0x0f) * 4; |
64 |
plen = (data[16] << 8 | data[17]) - hlen; |
65 |
proto = data[23];
|
66 |
|
67 |
switch (proto) {
|
68 |
case PROTO_TCP:
|
69 |
csum_offset = 16;
|
70 |
break;
|
71 |
case PROTO_UDP:
|
72 |
csum_offset = 6;
|
73 |
break;
|
74 |
default:
|
75 |
return;
|
76 |
} |
77 |
|
78 |
if (plen < csum_offset+2) |
79 |
return;
|
80 |
|
81 |
data[14+hlen+csum_offset] = 0; |
82 |
data[14+hlen+csum_offset+1] = 0; |
83 |
csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen); |
84 |
data[14+hlen+csum_offset] = csum >> 8; |
85 |
data[14+hlen+csum_offset+1] = csum & 0xff; |
86 |
} |