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#include "net/eth.h"
  22
  23uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq)
  24{
  25    uint32_t sum1 = 0, sum2 = 0;
  26    int i;
  27
  28    for (i = 0; i < len - 1; i += 2) {
  29        sum1 += (uint32_t)buf[i];
  30        sum2 += (uint32_t)buf[i + 1];
  31    }
  32    if (i < len) {
  33        sum1 += (uint32_t)buf[i];
  34    }
  35
  36    if (seq & 1) {
  37        return sum1 + (sum2 << 8);
  38    } else {
  39        return sum2 + (sum1 << 8);
  40    }
  41}
  42
  43uint16_t net_checksum_finish(uint32_t sum)
  44{
  45    while (sum>>16)
  46        sum = (sum & 0xFFFF)+(sum >> 16);
  47    return ~sum;
  48}
  49
  50uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
  51                             uint8_t *addrs, uint8_t *buf)
  52{
  53    uint32_t sum = 0;
  54
  55    sum += net_checksum_add(length, buf);         // payload
  56    sum += net_checksum_add(8, addrs);            // src + dst address
  57    sum += proto + length;                        // protocol & length
  58    return net_checksum_finish(sum);
  59}
  60
  61void net_checksum_calculate(uint8_t *data, int length)
  62{
  63    int mac_hdr_len, ip_len;
  64    struct ip_header *ip;
  65
  66    /*
  67     * Note: We cannot assume "data" is aligned, so the all code uses
  68     * some macros that take care of possible unaligned access for
  69     * struct members (just in case).
  70     */
  71
  72    /* Ensure we have at least an Eth header */
  73    if (length < sizeof(struct eth_header)) {
  74        return;
  75    }
  76
  77    /* Handle the optionnal VLAN headers */
  78    switch (lduw_be_p(&PKT_GET_ETH_HDR(data)->h_proto)) {
  79    case ETH_P_VLAN:
  80        mac_hdr_len = sizeof(struct eth_header) +
  81                     sizeof(struct vlan_header);
  82        break;
  83    case ETH_P_DVLAN:
  84        if (lduw_be_p(&PKT_GET_VLAN_HDR(data)->h_proto) == ETH_P_VLAN) {
  85            mac_hdr_len = sizeof(struct eth_header) +
  86                         2 * sizeof(struct vlan_header);
  87        } else {
  88            mac_hdr_len = sizeof(struct eth_header) +
  89                         sizeof(struct vlan_header);
  90        }
  91        break;
  92    default:
  93        mac_hdr_len = sizeof(struct eth_header);
  94        break;
  95    }
  96
  97    length -= mac_hdr_len;
  98
  99    /* Now check we have an IP header (with an optionnal VLAN header) */
 100    if (length < sizeof(struct ip_header)) {
 101        return;
 102    }
 103
 104    ip = (struct ip_header *)(data + mac_hdr_len);
 105
 106    if (IP_HEADER_VERSION(ip) != IP_HEADER_VERSION_4) {
 107        return; /* not IPv4 */
 108    }
 109
 110    ip_len = lduw_be_p(&ip->ip_len);
 111
 112    /* Last, check that we have enough data for the all IP frame */
 113    if (length < ip_len) {
 114        return;
 115    }
 116
 117    ip_len -= IP_HDR_GET_LEN(ip);
 118
 119    switch (ip->ip_p) {
 120    case IP_PROTO_TCP:
 121    {
 122        uint16_t csum;
 123        tcp_header *tcp = (tcp_header *)(ip + 1);
 124
 125        if (ip_len < sizeof(tcp_header)) {
 126            return;
 127        }
 128
 129        /* Set csum to 0 */
 130        stw_he_p(&tcp->th_sum, 0);
 131
 132        csum = net_checksum_tcpudp(ip_len, ip->ip_p,
 133                                   (uint8_t *)&ip->ip_src,
 134                                   (uint8_t *)tcp);
 135
 136        /* Store computed csum */
 137        stw_be_p(&tcp->th_sum, csum);
 138
 139        break;
 140    }
 141    case IP_PROTO_UDP:
 142    {
 143        uint16_t csum;
 144        udp_header *udp = (udp_header *)(ip + 1);
 145
 146        if (ip_len < sizeof(udp_header)) {
 147            return;
 148        }
 149
 150        /* Set csum to 0 */
 151        stw_he_p(&udp->uh_sum, 0);
 152
 153        csum = net_checksum_tcpudp(ip_len, ip->ip_p,
 154                                   (uint8_t *)&ip->ip_src,
 155                                   (uint8_t *)udp);
 156
 157        /* Store computed csum */
 158        stw_be_p(&udp->uh_sum, csum);
 159
 160        break;
 161    }
 162    default:
 163        /* Can't handle any other protocol */
 164        break;
 165    }
 166}
 167
 168uint32_t
 169net_checksum_add_iov(const struct iovec *iov, const unsigned int iov_cnt,
 170                     uint32_t iov_off, uint32_t size, uint32_t csum_offset)
 171{
 172    size_t iovec_off, buf_off;
 173    unsigned int i;
 174    uint32_t res = 0;
 175
 176    iovec_off = 0;
 177    buf_off = 0;
 178    for (i = 0; i < iov_cnt && size; i++) {
 179        if (iov_off < (iovec_off + iov[i].iov_len)) {
 180            size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size);
 181            void *chunk_buf = iov[i].iov_base + (iov_off - iovec_off);
 182
 183            res += net_checksum_add_cont(len, chunk_buf, csum_offset);
 184            csum_offset += len;
 185
 186            buf_off += len;
 187            iov_off += len;
 188            size -= len;
 189        }
 190        iovec_off += iov[i].iov_len;
 191    }
 192    return res;
 193}
 194