File:  [Qemu by Fabrice Bellard] / qemu / net-checksum.c
Revision 1.1.1.2 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 17:20:41 2018 UTC (23 months, 1 week ago) by root
Branches: qemu, MAIN
CVS tags: qemu0150, qemu0141, qemu0140, qemu0130, qemu0125, qemu0124, qemu0123, qemu0122, qemu0121, qemu0120, qemu0111, qemu0110, HEAD
qemu 0.11.0

    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: }

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