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/*
* 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 "qemu-common.h"
#include "net/checksum.h"
#include "net/eth.h"
uint32_t net_checksum_add_cont(int len, uint8_t *buf, int seq)
{
uint32_t sum = 0;
int i;
for (i = seq; i < seq + len; i++) {
if (i & 1) {
sum += (uint32_t)buf[i - seq];
} else {
sum += (uint32_t)buf[i - seq] << 8;
}
}
return sum;
}
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 ip_len;
struct ip_header *ip;
/*
* 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 data has complete L2 & L3 headers. */
if (length < (sizeof(struct eth_header) + sizeof(struct ip_header))) {
return;
}
ip = (struct ip_header *)(data + sizeof(struct eth_header));
if (IP_HEADER_VERSION(ip) != IP_HEADER_VERSION_4) {
return; /* not IPv4 */
}
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:
{
uint16_t csum;
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:
{
uint16_t csum;
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, buf_off;
unsigned int i;
uint32_t res = 0;
iovec_off = 0;
buf_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;
buf_off += len;
iov_off += len;
size -= len;
}
iovec_off += iov[i].iov_len;
}
return res;
}
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