17200ac3cSMark McLoughlin /* 27200ac3cSMark McLoughlin * IP checksumming functions. 37200ac3cSMark McLoughlin * (c) 2008 Gerd Hoffmann <kraxel@redhat.com> 47200ac3cSMark McLoughlin * 57200ac3cSMark McLoughlin * This program is free software; you can redistribute it and/or modify 67200ac3cSMark McLoughlin * it under the terms of the GNU General Public License as published by 7*4c32fe66SStefan Weil * the Free Software Foundation; under version 2 or later of the License. 87200ac3cSMark McLoughlin * 97200ac3cSMark McLoughlin * This program is distributed in the hope that it will be useful, 107200ac3cSMark McLoughlin * but WITHOUT ANY WARRANTY; without even the implied warranty of 117200ac3cSMark McLoughlin * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 127200ac3cSMark McLoughlin * GNU General Public License for more details. 137200ac3cSMark McLoughlin * 147200ac3cSMark McLoughlin * You should have received a copy of the GNU General Public License 157200ac3cSMark McLoughlin * along with this program; if not, see <http://www.gnu.org/licenses/>. 167200ac3cSMark McLoughlin */ 177200ac3cSMark McLoughlin 187200ac3cSMark McLoughlin #include "net/checksum.h" 197200ac3cSMark McLoughlin 207200ac3cSMark McLoughlin #define PROTO_TCP 6 217200ac3cSMark McLoughlin #define PROTO_UDP 17 227200ac3cSMark McLoughlin 237200ac3cSMark McLoughlin uint32_t net_checksum_add(int len, uint8_t *buf) 247200ac3cSMark McLoughlin { 257200ac3cSMark McLoughlin uint32_t sum = 0; 267200ac3cSMark McLoughlin int i; 277200ac3cSMark McLoughlin 287200ac3cSMark McLoughlin for (i = 0; i < len; i++) { 297200ac3cSMark McLoughlin if (i & 1) 307200ac3cSMark McLoughlin sum += (uint32_t)buf[i]; 317200ac3cSMark McLoughlin else 327200ac3cSMark McLoughlin sum += (uint32_t)buf[i] << 8; 337200ac3cSMark McLoughlin } 347200ac3cSMark McLoughlin return sum; 357200ac3cSMark McLoughlin } 367200ac3cSMark McLoughlin 377200ac3cSMark McLoughlin uint16_t net_checksum_finish(uint32_t sum) 387200ac3cSMark McLoughlin { 397200ac3cSMark McLoughlin while (sum>>16) 407200ac3cSMark McLoughlin sum = (sum & 0xFFFF)+(sum >> 16); 417200ac3cSMark McLoughlin return ~sum; 427200ac3cSMark McLoughlin } 437200ac3cSMark McLoughlin 447200ac3cSMark McLoughlin uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto, 457200ac3cSMark McLoughlin uint8_t *addrs, uint8_t *buf) 467200ac3cSMark McLoughlin { 477200ac3cSMark McLoughlin uint32_t sum = 0; 487200ac3cSMark McLoughlin 497200ac3cSMark McLoughlin sum += net_checksum_add(length, buf); // payload 507200ac3cSMark McLoughlin sum += net_checksum_add(8, addrs); // src + dst address 517200ac3cSMark McLoughlin sum += proto + length; // protocol & length 527200ac3cSMark McLoughlin return net_checksum_finish(sum); 537200ac3cSMark McLoughlin } 547200ac3cSMark McLoughlin 557200ac3cSMark McLoughlin void net_checksum_calculate(uint8_t *data, int length) 567200ac3cSMark McLoughlin { 577200ac3cSMark McLoughlin int hlen, plen, proto, csum_offset; 587200ac3cSMark McLoughlin uint16_t csum; 597200ac3cSMark McLoughlin 607200ac3cSMark McLoughlin if ((data[14] & 0xf0) != 0x40) 617200ac3cSMark McLoughlin return; /* not IPv4 */ 627200ac3cSMark McLoughlin hlen = (data[14] & 0x0f) * 4; 637200ac3cSMark McLoughlin plen = (data[16] << 8 | data[17]) - hlen; 647200ac3cSMark McLoughlin proto = data[23]; 657200ac3cSMark McLoughlin 667200ac3cSMark McLoughlin switch (proto) { 677200ac3cSMark McLoughlin case PROTO_TCP: 687200ac3cSMark McLoughlin csum_offset = 16; 697200ac3cSMark McLoughlin break; 707200ac3cSMark McLoughlin case PROTO_UDP: 717200ac3cSMark McLoughlin csum_offset = 6; 727200ac3cSMark McLoughlin break; 737200ac3cSMark McLoughlin default: 747200ac3cSMark McLoughlin return; 757200ac3cSMark McLoughlin } 767200ac3cSMark McLoughlin 777200ac3cSMark McLoughlin if (plen < csum_offset+2) 787200ac3cSMark McLoughlin return; 797200ac3cSMark McLoughlin 807200ac3cSMark McLoughlin data[14+hlen+csum_offset] = 0; 817200ac3cSMark McLoughlin data[14+hlen+csum_offset+1] = 0; 827200ac3cSMark McLoughlin csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen); 837200ac3cSMark McLoughlin data[14+hlen+csum_offset] = csum >> 8; 847200ac3cSMark McLoughlin data[14+hlen+csum_offset+1] = csum & 0xff; 857200ac3cSMark McLoughlin } 86