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-common.h"
  19#include "net/checksum.h"
  20
  21#define PROTO_TCP  6
  22#define PROTO_UDP 17
  23
  24uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq)
  25{
  26    uint32_t sum = 0;
  27    int i;
  28
  29    for (i = seq; i < seq + len; i++) {
  30        if (i & 1) {
  31            sum += (uint32_t)buf[i - seq];
  32        } else {
  33            sum += (uint32_t)buf[i - seq] << 8;
  34        }
  35    }
  36    return sum;
  37}
  38
  39uint16_t net_checksum_finish(uint32_t sum)
  40{
  41    while (sum>>16)
  42        sum = (sum & 0xFFFF)+(sum >> 16);
  43    return ~sum;
  44}
  45
  46uint16_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
  57void net_checksum_calculate(uint8_t *data, int length)
  58{
  59    int hlen, plen, proto, csum_offset;
  60    uint16_t csum;
  61
  62    /* Ensure data has complete L2 & L3 headers. */
  63    if (length < 14 + 20) {
  64        return;
  65    }
  66
  67    if ((data[14] & 0xf0) != 0x40)
  68        return; /* not IPv4 */
  69    hlen  = (data[14] & 0x0f) * 4;
  70    plen  = (data[16] << 8 | data[17]) - hlen;
  71    proto = data[23];
  72
  73    switch (proto) {
  74    case PROTO_TCP:
  75        csum_offset = 16;
  76        break;
  77    case PROTO_UDP:
  78        csum_offset = 6;
  79        break;
  80    default:
  81        return;
  82    }
  83
  84    if (plen < csum_offset + 2 || 14 + hlen + plen > length) {
  85        return;
  86    }
  87
  88    data[14+hlen+csum_offset]   = 0;
  89    data[14+hlen+csum_offset+1] = 0;
  90    csum = net_checksum_tcpudp(plen, proto, data+14+12, data+14+hlen);
  91    data[14+hlen+csum_offset]   = csum >> 8;
  92    data[14+hlen+csum_offset+1] = csum & 0xff;
  93}
  94
  95uint32_t
  96net_checksum_add_iov(const struct iovec *iov, const unsigned int iov_cnt,
  97                     uint32_t iov_off, uint32_t size)
  98{
  99    size_t iovec_off, buf_off;
 100    unsigned int i;
 101    uint32_t res = 0;
 102    uint32_t seq = 0;
 103
 104    iovec_off = 0;
 105    buf_off = 0;
 106    for (i = 0; i < iov_cnt && size; i++) {
 107        if (iov_off < (iovec_off + iov[i].iov_len)) {
 108            size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size);
 109            void *chunk_buf = iov[i].iov_base + (iov_off - iovec_off);
 110
 111            res += net_checksum_add_cont(len, chunk_buf, seq);
 112            seq += len;
 113
 114            buf_off += len;
 115            iov_off += len;
 116            size -= len;
 117        }
 118        iovec_off += iov[i].iov_len;
 119    }
 120    return res;
 121}
 122