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
  23 uint32_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
  43 uint16_t net_checksum_finish(uint32_t sum)
  44 {
  45     while (sum>>16)
  46         sum = (sum & 0xFFFF)+(sum >> 16);
  47     return ~sum;
  48 }
  49
  50 uint16_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
  61 void 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
 168 uint32_t
 169 net_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 }