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1 | 7200ac3c | Mark McLoughlin | /*
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2 | 7200ac3c | Mark McLoughlin | * IP checksumming functions.
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3 | 7200ac3c | Mark McLoughlin | * (c) 2008 Gerd Hoffmann <kraxel@redhat.com>
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4 | 7200ac3c | Mark McLoughlin | *
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5 | 7200ac3c | Mark McLoughlin | * This program is free software; you can redistribute it and/or modify
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6 | 7200ac3c | Mark McLoughlin | * it under the terms of the GNU General Public License as published by
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7 | 7200ac3c | Mark McLoughlin | * the Free Software Foundation; under version 2 of the License.
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8 | 7200ac3c | Mark McLoughlin | *
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9 | 7200ac3c | Mark McLoughlin | * This program is distributed in the hope that it will be useful,
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10 | 7200ac3c | Mark McLoughlin | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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11 | 7200ac3c | Mark McLoughlin | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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12 | 7200ac3c | Mark McLoughlin | * GNU General Public License for more details.
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13 | 7200ac3c | Mark McLoughlin | *
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14 | 7200ac3c | Mark McLoughlin | * You should have received a copy of the GNU General Public License
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15 | 7200ac3c | Mark McLoughlin | * along with this program; if not, see <http://www.gnu.org/licenses/>.
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16 | 7200ac3c | Mark McLoughlin | */
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17 | 7200ac3c | Mark McLoughlin | |
18 | 7200ac3c | Mark McLoughlin | #include "net/checksum.h" |
19 | 7200ac3c | Mark McLoughlin | |
20 | 7200ac3c | Mark McLoughlin | #define PROTO_TCP 6 |
21 | 7200ac3c | Mark McLoughlin | #define PROTO_UDP 17 |
22 | 7200ac3c | Mark McLoughlin | |
23 | 7200ac3c | Mark McLoughlin | uint32_t net_checksum_add(int len, uint8_t *buf)
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24 | 7200ac3c | Mark McLoughlin | { |
25 | 7200ac3c | Mark McLoughlin | uint32_t sum = 0;
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26 | 7200ac3c | Mark McLoughlin | int i;
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27 | 7200ac3c | Mark McLoughlin | |
28 | 7200ac3c | Mark McLoughlin | for (i = 0; i < len; i++) { |
29 | 7200ac3c | Mark McLoughlin | if (i & 1) |
30 | 7200ac3c | Mark McLoughlin | sum += (uint32_t)buf[i]; |
31 | 7200ac3c | Mark McLoughlin | else
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32 | 7200ac3c | Mark McLoughlin | sum += (uint32_t)buf[i] << 8;
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33 | 7200ac3c | Mark McLoughlin | } |
34 | 7200ac3c | Mark McLoughlin | return sum;
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35 | 7200ac3c | Mark McLoughlin | } |
36 | 7200ac3c | Mark McLoughlin | |
37 | 7200ac3c | Mark McLoughlin | uint16_t net_checksum_finish(uint32_t sum) |
38 | 7200ac3c | Mark McLoughlin | { |
39 | 7200ac3c | Mark McLoughlin | while (sum>>16) |
40 | 7200ac3c | Mark McLoughlin | sum = (sum & 0xFFFF)+(sum >> 16); |
41 | 7200ac3c | Mark McLoughlin | return ~sum;
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42 | 7200ac3c | Mark McLoughlin | } |
43 | 7200ac3c | Mark McLoughlin | |
44 | 7200ac3c | Mark McLoughlin | uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto, |
45 | 7200ac3c | Mark McLoughlin | uint8_t *addrs, uint8_t *buf) |
46 | 7200ac3c | Mark McLoughlin | { |
47 | 7200ac3c | Mark McLoughlin | uint32_t sum = 0;
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48 | 7200ac3c | Mark McLoughlin | |
49 | 7200ac3c | Mark McLoughlin | sum += net_checksum_add(length, buf); // payload
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50 | 7200ac3c | Mark McLoughlin | sum += net_checksum_add(8, addrs); // src + dst address |
51 | 7200ac3c | Mark McLoughlin | sum += proto + length; // protocol & length
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52 | 7200ac3c | Mark McLoughlin | return net_checksum_finish(sum);
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53 | 7200ac3c | Mark McLoughlin | } |
54 | 7200ac3c | Mark McLoughlin | |
55 | 7200ac3c | Mark McLoughlin | void net_checksum_calculate(uint8_t *data, int length) |
56 | 7200ac3c | Mark McLoughlin | { |
57 | 7200ac3c | Mark McLoughlin | int hlen, plen, proto, csum_offset;
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58 | 7200ac3c | Mark McLoughlin | uint16_t csum; |
59 | 7200ac3c | Mark McLoughlin | |
60 | 7200ac3c | Mark McLoughlin | if ((data[14] & 0xf0) != 0x40) |
61 | 7200ac3c | Mark McLoughlin | return; /* not IPv4 */ |
62 | 7200ac3c | Mark McLoughlin | hlen = (data[14] & 0x0f) * 4; |
63 | 7200ac3c | Mark McLoughlin | plen = (data[16] << 8 | data[17]) - hlen; |
64 | 7200ac3c | Mark McLoughlin | proto = data[23];
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65 | 7200ac3c | Mark McLoughlin | |
66 | 7200ac3c | Mark McLoughlin | switch (proto) {
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67 | 7200ac3c | Mark McLoughlin | case PROTO_TCP:
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68 | 7200ac3c | Mark McLoughlin | csum_offset = 16;
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69 | 7200ac3c | Mark McLoughlin | break;
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70 | 7200ac3c | Mark McLoughlin | case PROTO_UDP:
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71 | 7200ac3c | Mark McLoughlin | csum_offset = 6;
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72 | 7200ac3c | Mark McLoughlin | break;
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73 | 7200ac3c | Mark McLoughlin | default:
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74 | 7200ac3c | Mark McLoughlin | return;
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75 | 7200ac3c | Mark McLoughlin | } |
76 | 7200ac3c | Mark McLoughlin | |
77 | 7200ac3c | Mark McLoughlin | if (plen < csum_offset+2) |
78 | 7200ac3c | Mark McLoughlin | return;
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79 | 7200ac3c | Mark McLoughlin | |
80 | 7200ac3c | Mark McLoughlin | data[14+hlen+csum_offset] = 0; |
81 | 7200ac3c | Mark McLoughlin | data[14+hlen+csum_offset+1] = 0; |
82 | 7200ac3c | Mark McLoughlin | csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen); |
83 | 7200ac3c | Mark McLoughlin | data[14+hlen+csum_offset] = csum >> 8; |
84 | 7200ac3c | Mark McLoughlin | data[14+hlen+csum_offset+1] = csum & 0xff; |
85 | 7200ac3c | Mark McLoughlin | } |