LXR qemu/net/checksum.c

   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 or later 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 "qemu/osdep.h"
  19#include "qemu-common.h"
  20#include "net/checksum.h"
  21
  22#define PROTO_TCP  6
  23#define PROTO_UDP 17
  24
  25uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq)
  26{
  27    uint32_t sum = 0;
  28    int i;
  29
  30    for (i = seq; i < seq + len; i++) {
  31        if (i & 1) {
  32            sum += (uint32_t)buf[i - seq];
  33        } else {
  34            sum += (uint32_t)buf[i - seq] << 8;
  35        }
  36    }
  37    return sum;
  38}
  39
  40uint16_t net_checksum_finish(uint32_t sum)
  41{
  42    while (sum>>16)
  43        sum = (sum & 0xFFFF)+(sum >> 16);
  44    return ~sum;
  45}
  46
  47uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
  48                             uint8_t *addrs, uint8_t *buf)
  49{
  50    uint32_t sum = 0;
  51
  52    sum += net_checksum_add(length, buf);         // payload
  53    sum += net_checksum_add(8, addrs);            // src + dst address
  54    sum += proto + length;                        // protocol & length
  55    return net_checksum_finish(sum);
  56}
  57
  58void net_checksum_calculate(uint8_t *data, int length)
  59{
  60    int hlen, plen, proto, csum_offset;
  61    uint16_t csum;
  62
  63    /* Ensure data has complete L2 & L3 headers. */
  64    if (length < 14 + 20) {
  65        return;
  66    }
  67
  68    if ((data[14] & 0xf0) != 0x40)
  69        return; /* not IPv4 */
  70    hlen  = (data[14] & 0x0f) * 4;
  71    plen  = (data[16] << 8 | data[17]) - hlen;
  72    proto = data[23];
  73
  74    switch (proto) {
  75    case PROTO_TCP:
  76        csum_offset = 16;
  77        break;
  78    case PROTO_UDP:
  79        csum_offset = 6;
  80        break;
  81    default:
  82        return;
  83    }
  84
  85    if (plen < csum_offset + 2 || 14 + hlen + plen > length) {
  86        return;
  87    }
  88
  89    data[14+hlen+csum_offset]   = 0;
  90    data[14+hlen+csum_offset+1] = 0;
  91    csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen);
  92    data[14+hlen+csum_offset]   = csum >> 8;
  93    data[14+hlen+csum_offset+1] = csum & 0xff;
  94}
  95
  96uint32_t
  97net_checksum_add_iov(const struct iovec *iov, const unsigned int iov_cnt,
  98                     uint32_t iov_off, uint32_t size)
  99{
 100    size_t iovec_off, buf_off;
 101    unsigned int i;
 102    uint32_t res = 0;
 103    uint32_t seq = 0;
 104
 105    iovec_off = 0;
 106    buf_off = 0;
 107    for (i = 0; i < iov_cnt && size; i++) {
 108        if (iov_off < (iovec_off + iov[i].iov_len)) {
 109            size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size);
 110            void *chunk_buf = iov[i].iov_base + (iov_off - iovec_off);
 111
 112            res += net_checksum_add_cont(len, chunk_buf, seq);
 113            seq += len;
 114
 115            buf_off += len;
 116            iov_off += len;
 117            size -= len;
 118        }
 119        iovec_off += iov[i].iov_len;
 120    }
 121    return res;
 122}
 123