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"помогите пересчитать TCP checksum" Отправлено tcp, 27-Сен-06 18:05
попробовал вообще другим путём, u_short tcp_checksum (u_short *addr, int len) { u_short *w = addr; int i=len; int sum=0; //u_short answer; while (i > 0) { sum += *w++; i -= 2; } if (i ==1) sum +=*(u_char *)w; sum = (sum >> 16) + (sum & 0xffff); sum = sum + (sum >> 16); return (~sum); } struct _pseudoheader { struct in_addr source_addr; struct in_addr destination_addr; u_char zero; /* зеpо */ u_char protocol; u_short length; } pseudoheader; u_char *pseudopacket; pseudoheader.source_addr = iph->ip_src; pseudoheader.destination_addr = iph->ip_dst; pseudoheader.zero = 0; pseudoheader.protocol = IPPROTO_TCP; pseudoheader.length = size_tcp + size_payload; pseudopacket = (char *)malloc(sizeof(pseudoheader) + sizeof(struct tcphdr) + size_payload); if ( !pseudopacket ) { perror ("malloc"); exit (1); } memcpy (pseudopacket, &pseudoheader, sizeof (pseudoheader)); memcpy (pseudopacket + sizeof (pseudoheader),packet + +size_ethernet + sizeof (struct ip),sizeof (struct tcphdr)); memcpy (pseudopacket + sizeof (pseudoheader) + size_tcp, packet + size_ethernet + size_ip + size_tcp, size_payload); tcph->th_sum = 0; tcph->th_sum = tcp_checksum ((u_short *)pseudopacket, sizeof (pseudoheader)+sizeof(struct tcphdr)); взято из http://dims.karelia.ru/~alexmou/nets_tele/lab05_raw_sockets.pdf