qemu

checksum.c (5545B)

---

 /*
  *  IP checksumming functions.
  *  (c) 2008 Gerd Hoffmann <kraxel@redhat.com>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
  *  the Free Software Foundation; under version 2 or later of the License.
  *
  *  This program is distributed in the hope that it will be useful,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  *  GNU General Public License for more details.
  *
  *  You should have received a copy of the GNU General Public License
  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 
 #include "qemu/osdep.h"
 #include "net/checksum.h"
 #include "net/eth.h"
 
 uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq)
 {
     uint32_t sum1 = 0, sum2 = 0;
     int i;
 
     for (i = 0; i < len - 1; i += 2) {
         sum1 += (uint32_t)buf[i];
         sum2 += (uint32_t)buf[i + 1];
     }
     if (i < len) {
         sum1 += (uint32_t)buf[i];
     }
 
     if (seq & 1) {
         return sum1 + (sum2 << 8);
     } else {
         return sum2 + (sum1 << 8);
     }
 }
 
 uint16_t net_checksum_finish(uint32_t sum)
 {
     while (sum>>16)
         sum = (sum & 0xFFFF)+(sum >> 16);
     return ~sum;
 }
 
 uint16_t net_checksum_tcpudp(uint16_t length, uint16_t proto,
                              uint8_t *addrs, uint8_t *buf)
 {
     uint32_t sum = 0;
 
     sum += net_checksum_add(length, buf);         // payload
     sum += net_checksum_add(8, addrs);            // src + dst address
     sum += proto + length;                        // protocol & length
     return net_checksum_finish(sum);
 }
 
 void net_checksum_calculate(uint8_t *data, int length, int csum_flag)
 {
     int mac_hdr_len, ip_len;
     struct ip_header *ip;
     uint16_t csum;
 
     /*
      * Note: We cannot assume "data" is aligned, so the all code uses
      * some macros that take care of possible unaligned access for
      * struct members (just in case).
      */
 
     /* Ensure we have at least an Eth header */
     if (length < sizeof(struct eth_header)) {
         return;
     }
 
     /* Handle the optionnal VLAN headers */
     switch (lduw_be_p(&PKT_GET_ETH_HDR(data)->h_proto)) {
     case ETH_P_VLAN:
         mac_hdr_len = sizeof(struct eth_header) +
                      sizeof(struct vlan_header);
         break;
     case ETH_P_DVLAN:
         if (lduw_be_p(&PKT_GET_VLAN_HDR(data)->h_proto) == ETH_P_VLAN) {
             mac_hdr_len = sizeof(struct eth_header) +
                          2 * sizeof(struct vlan_header);
         } else {
             mac_hdr_len = sizeof(struct eth_header) +
                          sizeof(struct vlan_header);
         }
         break;
     default:
         mac_hdr_len = sizeof(struct eth_header);
         break;
     }
 
     length -= mac_hdr_len;
 
     /* Now check we have an IP header (with an optionnal VLAN header) */
     if (length < sizeof(struct ip_header)) {
         return;
     }
 
     ip = (struct ip_header *)(data + mac_hdr_len);
 
     if (IP_HEADER_VERSION(ip) != IP_HEADER_VERSION_4) {
         return; /* not IPv4 */
     }
 
     /* Calculate IP checksum */
     if (csum_flag & CSUM_IP) {
         stw_he_p(&ip->ip_sum, 0);
         csum = net_raw_checksum((uint8_t *)ip, IP_HDR_GET_LEN(ip));
         stw_be_p(&ip->ip_sum, csum);
     }
 
     if (IP4_IS_FRAGMENT(ip)) {
         return; /* a fragmented IP packet */
     }
 
     ip_len = lduw_be_p(&ip->ip_len);
 
     /* Last, check that we have enough data for the all IP frame */
     if (length < ip_len) {
         return;
     }
 
     ip_len -= IP_HDR_GET_LEN(ip);
 
     switch (ip->ip_p) {
     case IP_PROTO_TCP:
     {
         if (!(csum_flag & CSUM_TCP)) {
             return;
         }
 
         tcp_header *tcp = (tcp_header *)(ip + 1);
 
         if (ip_len < sizeof(tcp_header)) {
             return;
         }
 
         /* Set csum to 0 */
         stw_he_p(&tcp->th_sum, 0);
 
         csum = net_checksum_tcpudp(ip_len, ip->ip_p,
                                    (uint8_t *)&ip->ip_src,
                                    (uint8_t *)tcp);
 
         /* Store computed csum */
         stw_be_p(&tcp->th_sum, csum);
 
         break;
     }
     case IP_PROTO_UDP:
     {
         if (!(csum_flag & CSUM_UDP)) {
             return;
         }
 
         udp_header *udp = (udp_header *)(ip + 1);
 
         if (ip_len < sizeof(udp_header)) {
             return;
         }
 
         /* Set csum to 0 */
         stw_he_p(&udp->uh_sum, 0);
 
         csum = net_checksum_tcpudp(ip_len, ip->ip_p,
                                    (uint8_t *)&ip->ip_src,
                                    (uint8_t *)udp);
 
         /* Store computed csum */
         stw_be_p(&udp->uh_sum, csum);
 
         break;
     }
     default:
         /* Can't handle any other protocol */
         break;
     }
 }
 
 uint32_t
 net_checksum_add_iov(const struct iovec *iov, const unsigned int iov_cnt,
                      uint32_t iov_off, uint32_t size, uint32_t csum_offset)
 {
     size_t iovec_off;
     unsigned int i;
     uint32_t res = 0;
 
     iovec_off = 0;
     for (i = 0; i < iov_cnt && size; i++) {
         if (iov_off < (iovec_off + iov[i].iov_len)) {
             size_t len = MIN((iovec_off + iov[i].iov_len) - iov_off , size);
             void *chunk_buf = iov[i].iov_base + (iov_off - iovec_off);
 
             res += net_checksum_add_cont(len, chunk_buf, csum_offset);
             csum_offset += len;
 
             iov_off += len;
             size -= len;
         }
         iovec_off += iov[i].iov_len;
     }
     return res;
 }