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
  22 uint32_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
  42 uint16_t net_checksum_finish(uint32_t sum)
  43 {
  44     while (sum>>16)
  45         sum = (sum & 0xFFFF)+(sum >> 16);
  46     return ~sum;
  47 }
  48
  49 uint16_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
  60 void 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
 167 uint32_t
 168 net_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 }