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 "net/checksum.h"
  20#include "net/eth.h"
  21
  22uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq)
  23{
  24    uint32_t sum1 = 0, sum2 = 0;
  25    int i;
  26
  27    for (i = 0; i < len - 1; i += 2) {
  28        sum1 += (uint32_t)buf[i];
  29        sum2 += (uint32_t)buf[i + 1];
  30    }
  31    if (i < len) {
  32        sum1 += (uint32_t)buf[i];
  33    }
  34
  35    if (seq & 1) {
  36        return sum1 + (sum2 << 8);
  37    } else {
  38        return sum2 + (sum1 << 8);
  39    }
  40}
  41
  42uint16_t net_checksum_finish(uint32_t sum)
  43{
  44    while (sum>>16)
  45        sum = (sum & 0xFFFF)+(sum >> 16);
  46    return ~sum;
  47}
  48
  49uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
  50                             uint8_t *addrs, uint8_t *buf)
  51{
  52    uint32_t sum = 0;
  53
  54    sum += net_checksum_add(length, buf);         // payload
  55    sum += net_checksum_add(8, addrs);            // src + dst address
  56    sum += proto + length;                        // protocol & length
  57    return net_checksum_finish(sum);
  58}
  59
  60void net_checksum_calculate(uint8_t *data, int length)
  61{
  62    int mac_hdr_len, ip_len;
  63    struct ip_header *ip;
  64
  65    /*
  66     * Note: We cannot assume "data" is aligned, so the all code uses
  67     * some macros that take care of possible unaligned access for
  68     * struct members (just in case).
  69     */
  70
  71    /* Ensure we have at least an Eth header */
  72    if (length < sizeof(struct eth_header)) {
  73        return;
  74    }
  75
  76    /* Handle the optionnal VLAN headers */
  77    switch (lduw_be_p(&PKT_GET_ETH_HDR(data)->h_proto)) {
  78    case ETH_P_VLAN:
  79        mac_hdr_len = sizeof(struct eth_header) +
  80                     sizeof(struct vlan_header);
  81        break;
  82    case ETH_P_DVLAN:
  83        if (lduw_be_p(&PKT_GET_VLAN_HDR(data)->h_proto) == ETH_P_VLAN) {
  84            mac_hdr_len = sizeof(struct eth_header) +
  85                         2 * sizeof(struct vlan_header);
  86        } else {
  87            mac_hdr_len = sizeof(struct eth_header) +
  88                         sizeof(struct vlan_header);
  89        }
  90        break;
  91    default:
  92        mac_hdr_len = sizeof(struct eth_header);
  93        break;
  94    }
  95
  96    length -= mac_hdr_len;
  97
  98    /* Now check we have an IP header (with an optionnal VLAN header) */
  99    if (length < sizeof(struct ip_header)) {
 100        return;
 101    }
 102
 103    ip = (struct ip_header *)(data + mac_hdr_len);
 104
 105    if (IP_HEADER_VERSION(ip) != IP_HEADER_VERSION_4) {
 106        return; /* not IPv4 */
 107    }
 108
 109    ip_len = lduw_be_p(&ip->ip_len);
 110
 111    /* Last, check that we have enough data for the all IP frame */
 112    if (length < ip_len) {
 113        return;
 114    }
 115
 116    ip_len -= IP_HDR_GET_LEN(ip);
 117
 118    switch (ip->ip_p) {
 119    case IP_PROTO_TCP:
 120    {
 121        uint16_t csum;
 122        tcp_header *tcp = (tcp_header *)(ip + 1);
 123
 124        if (ip_len < sizeof(tcp_header)) {
 125            return;
 126        }
 127
 128        /* Set csum to 0 */
 129        stw_he_p(&tcp->th_sum, 0);
 130
 131        csum = net_checksum_tcpudp(ip_len, ip->ip_p,
 132                                   (uint8_t *)&ip->ip_src,
 133                                   (uint8_t *)tcp);
 134
 135        /* Store computed csum */
 136        stw_be_p(&tcp->th_sum, csum);
 137
 138        break;
 139    }
 140    case IP_PROTO_UDP:
 141    {
 142        uint16_t csum;
 143        udp_header *udp = (udp_header *)(ip + 1);
 144
 145        if (ip_len < sizeof(udp_header)) {
 146            return;
 147        }
 148
 149        /* Set csum to 0 */
 150        stw_he_p(&udp->uh_sum, 0);
 151
 152        csum = net_checksum_tcpudp(ip_len, ip->ip_p,
 153                                   (uint8_t *)&ip->ip_src,
 154                                   (uint8_t *)udp);
 155
 156        /* Store computed csum */
 157        stw_be_p(&udp->uh_sum, csum);
 158
 159        break;
 160    }
 161    default:
 162        /* Can't handle any other protocol */
 163        break;
 164    }
 165}
 166
 167uint32_t
 168net_checksum_add_iov(const struct iovec *iov, const unsigned int iov_cnt,
 169                     uint32_t iov_off, uint32_t size, uint32_t csum_offset)
 170{
 171    size_t iovec_off, buf_off;
 172    unsigned int i;
 173    uint32_t res = 0;
 174
 175    iovec_off = 0;
 176    buf_off = 0;
 177    for (i = 0; i < iov_cnt && size; i++) {
 178        if (iov_off < (iovec_off + iov[i].iov_len)) {
 179            size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size);
 180            void *chunk_buf = iov[i].iov_base + (iov_off - iovec_off);
 181
 182            res += net_checksum_add_cont(len, chunk_buf, csum_offset);
 183            csum_offset += len;
 184
 185            buf_off += len;
 186            iov_off += len;
 187            size -= len;
 188        }
 189        iovec_off += iov[i].iov_len;
 190    }
 191    return res;
 192}
 193