/* * IP checksumming functions. * (c) 2008 Gerd Hoffmann <kraxel@redhat.com> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; under version 2 of the License. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, see <http://www.gnu.org/licenses/>. */ #include "hw/hw.h" #include "net.h" #define PROTO_TCP 6 #define PROTO_UDP 17 uint32_t net_checksum_add(int len, uint8_t *buf) { uint32_t sum = 0; int i; for (i = 0; i < len; i++) { if (i & 1) sum += (uint32_t)buf[i]; else sum += (uint32_t)buf[i] << 8; } return sum; } uint16_t net_checksum_finish(uint32_t sum) { while (sum>>16) sum = (sum & 0xFFFF)+(sum >> 16); return ~sum; } uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto, uint8_t *addrs, uint8_t *buf) { uint32_t sum = 0; sum += net_checksum_add(length, buf); // payload sum += net_checksum_add(8, addrs); // src + dst address sum += proto + length; // protocol & length return net_checksum_finish(sum); } void net_checksum_calculate(uint8_t *data, int length) { int hlen, plen, proto, csum_offset; uint16_t csum; if ((data[14] & 0xf0) != 0x40) return; /* not IPv4 */ hlen = (data[14] & 0x0f) * 4; plen = (data[16] << 8 | data[17]) - hlen; proto = data[23]; switch (proto) { case PROTO_TCP: csum_offset = 16; break; case PROTO_UDP: csum_offset = 6; break; default: return; } if (plen < csum_offset+2) return; data[14+hlen+csum_offset] = 0; data[14+hlen+csum_offset+1] = 0; csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen); data[14+hlen+csum_offset] = csum >> 8; data[14+hlen+csum_offset+1] = csum & 0xff; }