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