File:  [Qemu by Fabrice Bellard] / qemu / net-checksum.c
Revision 1.1.1.1 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 16:50:35 2018 UTC (3 years, 3 months ago) by root
Branches: qemu, MAIN
CVS tags: qemu0105, qemu0104, qemu0103, qemu0102, qemu0101, qemu0100, HEAD
qemu 0.10.0

    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, write to the Free Software
   16:  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA  02110-1301 USA
   17:  */
   18: 
   19: #include "hw/hw.h"
   20: #include "net.h"
   21: 
   22: #define PROTO_TCP  6
   23: #define PROTO_UDP 17
   24: 
   25: uint32_t net_checksum_add(int len, uint8_t *buf)
   26: {
   27:     uint32_t sum = 0;
   28:     int i;
   29: 
   30:     for (i = 0; i < len; i++) {
   31: 	if (i & 1)
   32: 	    sum += (uint32_t)buf[i];
   33: 	else
   34: 	    sum += (uint32_t)buf[i] << 8;
   35:     }
   36:     return sum;
   37: }
   38: 
   39: uint16_t net_checksum_finish(uint32_t sum)
   40: {
   41:     while (sum>>16)
   42: 	sum = (sum & 0xFFFF)+(sum >> 16);
   43:     return ~sum;
   44: }
   45: 
   46: uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
   47:                              uint8_t *addrs, uint8_t *buf)
   48: {
   49:     uint32_t sum = 0;
   50: 
   51:     sum += net_checksum_add(length, buf);         // payload
   52:     sum += net_checksum_add(8, addrs);            // src + dst address
   53:     sum += proto + length;                        // protocol & length
   54:     return net_checksum_finish(sum);
   55: }
   56: 
   57: void net_checksum_calculate(uint8_t *data, int length)
   58: {
   59:     int hlen, plen, proto, csum_offset;
   60:     uint16_t csum;
   61: 
   62:     if ((data[14] & 0xf0) != 0x40)
   63: 	return; /* not IPv4 */
   64:     hlen  = (data[14] & 0x0f) * 4;
   65:     plen  = (data[16] << 8 | data[17]) - hlen;
   66:     proto = data[23];
   67: 
   68:     switch (proto) {
   69:     case PROTO_TCP:
   70: 	csum_offset = 16;
   71: 	break;
   72:     case PROTO_UDP:
   73: 	csum_offset = 6;
   74: 	break;
   75:     default:
   76: 	return;
   77:     }
   78: 
   79:     if (plen < csum_offset+2)
   80: 	return;
   81: 
   82:     data[14+hlen+csum_offset]   = 0;
   83:     data[14+hlen+csum_offset+1] = 0;
   84:     csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen);
   85:     data[14+hlen+csum_offset]   = csum >> 8;
   86:     data[14+hlen+csum_offset+1] = csum & 0xff;
   87: }

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