Re: 2 idées et 1 remarque

J'utilise une autre fonction de calcul de checksum qui vient d'un article de phrack maintenant

int checksum (unsigned short *buf, int nwords)
{
/*! Compute Internet Checksum for "count" bytes
* beginning at location "addr".
*/
register long sum = 0;

while( nwords > 1 ) {
/*! This is the inner loop */
sum += *buf++;
nwords -= 2;
}

/*! Add left-over byte, if any */
if( nwords == 1 )
{
u_short oddbyte = 0;
*((u_char *) &oddbyte) = *(u_char *)buf;
sum += oddbyte;
}

/*! Fold 32-bit sum to 16 bits */
sum = (sum >> 16) + (sum & 0xffff); /* add high-16 to low-16 */
sum += (sum >> 16); /* add carry */
return(~sum);
}

de fait, le code de creation devient

/*! *******************
* compute TCP checksum
* ********************
*/
int PSEUDO_SIZE = /*! 12 = size of the pseudoheader */
PAYLOAD_SIZE + (replay_tcp->doff*4) + 12;

char pseudo_tcp[ PSEUDO_SIZE ];

/*! fill up the pseudo header
*/
struct pseudo_header *ph = (struct pseudo_header *) pseudo_tcp;

ph->saddr = iph->saddr;
ph->daddr = iph->daddr;
ph->mbz = 0;
ph->ptcl = 6;
ph->tcpl = htons(PSEUDO_SIZE - 12);

/*! fill check field to 0 for checksum computation
*/
replay_tcp->check = 0;

/*! add tcp header + payload to the pseudo packet
*/
memcpy((char *)&ph->tcp, (char *)&replay_tcp, PSEUDO_SIZE - 12);

/*! compute the checksum and store it in the TCP structure
*/
replay_tcp->check = checksum((unsigned short *) pseudo_tcp, PSEUDO_SIZE );

g_print("check = %x, size = %u \n", ntohs(replay_tcp->check), PSEUDO_SIZE);

mais ca marche toujours pas :'(