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1 /* |
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2 * IP checksumming functions. |
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3 * (c) 2008 Gerd Hoffmann <kraxel@redhat.com> |
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4 * |
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5 * This program is free software; you can redistribute it and/or modify |
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6 * it under the terms of the GNU General Public License as published by |
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7 * the Free Software Foundation; under version 2 of the License. |
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8 * |
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9 * This program is distributed in the hope that it will be useful, |
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10 * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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12 * GNU General Public License for more details. |
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13 * |
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14 * You should have received a copy of the GNU General Public License |
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15 * along with this program; if not, write to the Free Software |
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16 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
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17 */ |
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18 |
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19 #include "hw/hw.h" |
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20 #include "net.h" |
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21 |
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22 #define PROTO_TCP 6 |
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23 #define PROTO_UDP 17 |
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24 |
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25 uint32_t net_checksum_add(int len, uint8_t *buf) |
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26 { |
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27 uint32_t sum = 0; |
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28 int i; |
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29 |
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30 for (i = 0; i < len; i++) { |
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31 if (i & 1) |
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32 sum += (uint32_t)buf[i]; |
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33 else |
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34 sum += (uint32_t)buf[i] << 8; |
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35 } |
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36 return sum; |
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37 } |
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38 |
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39 uint16_t net_checksum_finish(uint32_t sum) |
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40 { |
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41 while (sum>>16) |
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42 sum = (sum & 0xFFFF)+(sum >> 16); |
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43 return ~sum; |
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44 } |
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45 |
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46 uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto, |
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47 uint8_t *addrs, uint8_t *buf) |
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48 { |
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49 uint32_t sum = 0; |
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50 |
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51 sum += net_checksum_add(length, buf); // payload |
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52 sum += net_checksum_add(8, addrs); // src + dst address |
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53 sum += proto + length; // protocol & length |
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54 return net_checksum_finish(sum); |
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55 } |
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56 |
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57 void net_checksum_calculate(uint8_t *data, int length) |
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58 { |
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59 int hlen, plen, proto, csum_offset; |
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60 uint16_t csum; |
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61 |
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62 if ((data[14] & 0xf0) != 0x40) |
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63 return; /* not IPv4 */ |
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64 hlen = (data[14] & 0x0f) * 4; |
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65 plen = (data[16] << 8 | data[17]) - hlen; |
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66 proto = data[23]; |
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67 |
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68 switch (proto) { |
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69 case PROTO_TCP: |
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70 csum_offset = 16; |
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71 break; |
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72 case PROTO_UDP: |
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73 csum_offset = 6; |
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74 break; |
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75 default: |
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76 return; |
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77 } |
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78 |
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79 if (plen < csum_offset+2) |
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80 return; |
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81 |
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82 data[14+hlen+csum_offset] = 0; |
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83 data[14+hlen+csum_offset+1] = 0; |
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84 csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen); |
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85 data[14+hlen+csum_offset] = csum >> 8; |
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86 data[14+hlen+csum_offset+1] = csum & 0xff; |
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87 } |