traceroute.c

实现了traceroute的功能

#include <stdio.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/udp.h>
#include <netinet/ip_icmp.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <errno.h>
#include <signal.h>
#include <setjmp.h>

#define BUFFER_SIZE 1500
int ttl = 0;
static sigjmp_buf jmpbuf;

static void recvfrom_alarm(int signo) 
{ 
	printf("*");
        alarm(3);
        siglongjmp(jmpbuf, 1);
}

int main(int argc, char *argv[])
{
        int max_ttl=30;//最大TTL
        u_short sport=30000;//本机端口	
        u_short dport=32768+666;//宿端口
	int myflag= 1;
	const char *message = "Hello Linux World!";//发送的字符串
        int len=strlen(message);//字符串长度
        int    i,j,  packetsize,  sockfd,  number,  clilen;
	struct in_addr src_addr,des_addr;
	struct hostent *host;
	struct sockaddr_in cliaddr,servaddr;
	struct udphdr *udp;
	struct iphdr  *ip,*ip_header;
	struct icmphdr *icmp;
        struct timeval t1,t2;
	double rtt;

        char recvbuf[BUFFER_SIZE] , packet[BUFFER_SIZE], ipstr[INET_ADDRSTRLEN],iptr[INET_ADDRSTRLEN];
        if(argc != 2)
	{
	  printf("usage :traceroute hostname \n");
	  exit(1);
	}
	src_addr.s_addr = htonl(INADDR_ANY);

	if((host=gethostbyname(argv[1])) == NULL)//get host by name
	{
		perror("gethostbyname");
		exit(1);
	}

	memcpy((void*)&des_addr,host->h_addr,sizeof(struct in_addr));

	if(inet_ntop(AF_INET,&(des_addr),iptr,INET_ADDRSTRLEN) == NULL)
  	{
	  perror("inet_ntop");
	  exit(1);
  	}
  	
  	printf("traceroute to %s (%s) %d hop max %d bytes packets\n",argv[1],iptr,max_ttl,len);

	if((sockfd=socket(AF_INET,SOCK_RAW,IPPROTO_ICMP))<0)
	{
		perror("socket");
		exit(1);
	}

	if(setsockopt(sockfd,IPPROTO_IP,IP_HDRINCL,(char*)&myflag,sizeof(myflag))<0)
	{
		perror("setsockopt");
		exit(1);
	}
	
	packetsize = sizeof(struct iphdr) + sizeof(struct udphdr) + strlen(message);//计算发送包的大小
	
        signal(SIGALRM,recvfrom_alarm);
	alarm(3);
	for (ttl=1;ttl <=max_ttl;ttl++)
	  { 
           //创建ip头
	   ip_header = (struct iphdr *)packet;
           bzero((char*)(ip_header),sizeof(struct iphdr));
           ip_header->ihl = 5;
           ip_header->version = 4;
           ip_header->id = htons(getpid());
           ip_header->ttl = ttl; 
           ip_header->protocol = IPPROTO_UDP;
           ip_header->daddr = des_addr.s_addr;
       
         
	   //为剩余空间清零
	   bzero((packet + sizeof(struct udphdr) + sizeof(struct iphdr)),BUFFER_SIZE-packetsize);
	   printf("%2d",ttl);
           fflush(stdout);
	   //udp指针
	   udp  =(struct udphdr*)(packet + sizeof(struct iphdr));
	   //创建udp头
           udp->source = htons(sport);
	   udp->dest = htons(dport);
	   udp->len = htons((sizeof(struct udphdr)+strlen(message))); 
	   udp->check = 0;
  	   //将Hello Linux World 拷贝到包中
           memcpy((char*)udp+sizeof(struct udphdr),message,strlen(message));
	   //连接准备工作
	   bzero(&servaddr,sizeof(servaddr));
	   servaddr.sin_family = AF_INET;
	   servaddr.sin_port = htons(dport);
	   servaddr.sin_addr = des_addr;
   	  
	
   	   //时间戳
           for(j=0;j<3;j++)
	     {
           gettimeofday(&t1,NULL);
	   if(sendto(sockfd,packet,packetsize,0,(struct sockaddr *)&servaddr,sizeof(servaddr)) != packetsize)
    		{
		  perror("sendto");
		  exit(1);
    		}
    		
	   if (sigsetjmp(jmpbuf, 1) != 0)
	     continue;
    	
	   number = recvfrom(sockfd,recvbuf, BUFFER_SIZE-1, 0, (struct sockaddr *)&cliaddr , &clilen);
	  
	 
	   gettimeofday(&t2,NULL);
	   t2.tv_sec = t2.tv_sec - t1.tv_sec;
	   t2.tv_usec = t2.tv_usec - t1.tv_usec;
	   rtt = t2.tv_sec*1000.0+ t2.tv_usec/1000.0;  
	   printf("  %.3f ms",rtt);
	     }	
	   recvbuf[number] = '\0';
	   	   	
	   ip = (struct iphdr*)recvbuf;
	   icmp = (struct icmphdr *)(recvbuf+sizeof(struct iphdr));
	   udp = (struct udphdr *)(recvbuf + 2*sizeof(struct iphdr) + sizeof(struct icmphdr));
	   printf("  %s  ",inet_ntop(AF_INET,(struct in_addr *)&(ip->saddr),ipstr,INET_ADDRSTRLEN));	
	   printf("\n");	
	   if(icmp->type==ICMP_TIME_EXCEEDED && icmp->code==ICMP_EXC_TTL)
   		{

   		continue;
   		}
	   if(icmp->type==ICMP_DEST_UNREACH && icmp->code==ICMP_PORT_UNREACH)
   		{
   		ip = (struct iphdr*)recvbuf;

                break;
       		}
       	 
   	}
   return 0;
}