ICMP协议的PING程序

今天药忘吃喽~ 2024-04-18 21:22 91阅读 0赞

#include <signal.h>
    #include <sys/socket.h>
    #include <sys/types.h>
    #include <sys/time.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <unistd.h>
    #include <netdb.h>
    #include <netinet/in.h>
    #include <arpa/inet.h>
    #include <netinet/ip.h>
    #include <netinet/ip_icmp.h>
    #include <errno.h>
    
    #define PACKET_SIZE 4096
    #define MAX_WAIT_TIME 5
    #define MAX_NO_PACKETS 3
    
    char sendpacket[PACKET_SIZE];
    char recvpacket[PACKET_SIZE];
    int sockfd,datalen=56;
    int nsend = 0, nreceived = 0;
    struct sockaddr_in dest_addr;
    struct sockaddr_in from;
    struct timeval tvrecv;
    pid_t pid;
    
    void send_packet();
    void recv_packet();
    void statistics(int signo);
    unsigned short cal_chksum(unsigned short *addr, int len);
    int pack(int pack_no);
    int unpack(char *buf, int len);
    
    void statistics(int signo)
    {
    	printf("\n-------------PING statistics-------------\n");
    	printf("%d packets transmitted, %d received, %%%d lost\n",nsend,nreceived,(nsend-nreceived)/nsend*100);
    	close(sockfd);
    	exit(1);
    }
    
    void tv_sub(struct timeval *out, struct timeval *in)
    {
    	if((out->tv_usec -= in->tv_usec) < 0){
    		--out->tv_sec;
    		out->tv_usec+=1000000;
    	}
    	out->tv_usec -= in->tv_sec;;
    }
    unsigned short cal_chksum(unsigned short *addr, int len)
    {
    	int nleft =len;
    	int sum = 0;
    	unsigned short *w = addr;
    	unsigned 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;
    }
    
    int pack(int pack_no)
    {
    	int packsize;
    	struct icmp *icmp;
    	struct timeval *tval;
    	
    	icmp = (struct icmp *)sendpacket;
    	icmp->icmp_type = ICMP_ECHO;
    	icmp->icmp_code = 0;
    	icmp->icmp_cksum = 0;
    	icmp->icmp_seq = pack_no;
    	icmp->icmp_id = pid;
    	
    	packsize = 8 + datalen;
    	tval = (struct timeval *)icmp->icmp_data;
    	gettimeofday(tval,NULL);//记录发包时间
    	icmp->icmp_cksum = cal_chksum((unsigned short *)icmp,packsize);
    	return packsize;
    }
    
    void send_packet()
    {
    	int packtsize;
    	while(nsend < MAX_NO_PACKETS){//ping的次数
    		nsend++;
    		packtsize = pack(nsend);//填充icmp
    		if(sendto(sockfd,sendpacket,packtsize,0,(struct sockaddr *)&dest_addr,sizeof(dest_addr)) < 0){
    			perror("sendto error");
    			continue;
    		}
    		sleep(1);
    	}
    }
    
    void recv_packet()
    {
    	int n,fromlen;
    	extern int errno;
    	signal(SIGALRM,statistics);//收到信号，跳转statistics函数
    	fromlen = sizeof(from);//接收包的长度
    	while(nreceived < 10){
    		alarm(MAX_WAIT_TIME);//定义5秒
    		if((n = recvfrom(sockfd,recvpacket,sizeof(recvpacket),0,(struct sockaddr *)&from,&fromlen)) < 0){//读取包
    			if(errno == EINTR) continue;
    			perror("recvfrom error");
    			continue;
    		}
    		gettimeofday(&tvrecv,NULL);//记录收到包的时间
    		if(unpack(recvpacket,n) == -1) continue;//调用unpack解包，传入包和长度n
    		nreceived++;
    	}
    }
    
    int unpack(char *buf,int len)
    {
    	int iphdrlen;
    	struct ip *ip;
    	struct icmp *icmp;
    	struct timeval *tvsend;
    	double rtt;
    	ip = (struct ip *)buf;
    	iphdrlen = (ip->ip_hl)*4;//求IP包头长度
    	icmp = (struct icmp *)(buf + iphdrlen);
    	len -= iphdrlen;//减去IP包头，直接指向icmp报文
    	if(len < 8){
    		printf("ICMP packets \'s length is less than 8\n");
    		return -1;
    	}
    	if((icmp->icmp_type == ICMP_ECHOREPLY) && (icmp->icmp_id  ==pid)){//判断icmp包是否问应答包，比对发的包和接收的包是否对应
    		tvsend = (struct timeval *)icmp->icmp_data;
    		tv_sub(&tvrecv,tvsend);//计算时间差
    		rtt = tvrecv.tv_sec*1000 + tvrecv.tv_usec/1000;
    		printf("%d bytes from %s:icmp_seq=%u tll=%d rtt=%.3fms \n",
    		len,inet_ntoa(from.sin_addr),
    		icmp->icmp_seq,ip->ip_ttl,rtt);
    	} else return -1;
    	
    	return 0;
    }
    
    int main(int argc, char *argv[])
    {
    	struct hostent *host;
    	struct protoent *protocol;
    	int size = 50*1024;
    	
    	if(argc < 2){
    		printf("usage:%s hostname/IP address\n",argv[0]);
    		exit(1);
    	}
    	
    	if((protocol = getprotobyname("icmp")) == NULL){
    		perror("unknow protocol icmp");
    		exit(1);
    	}
    	
    	if((sockfd = socket(AF_INET,SOCK_RAW,protocol->p_proto)) < 0){
    		perror("socket error");
    		exit(2);
    	}
    	
    	setuid(getuid());
    	setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size));
    	bzero(&dest_addr,sizeof(dest_addr));
    	dest_addr.sin_family = AF_INET;
    	
    	if((host = gethostbyname(argv[1])) == NULL){
    		perror("gethostbyname error");
    		exit(1);
    	}
    	
    	dest_addr.sin_addr = *((struct in_addr *)host->h_addr);
    	pid = getpid();
    	printf("PING %s(%s):%d bytes data in ICMP packets.\n",argv[1],
    		inet_ntoa(dest_addr.sin_addr),datalen);
    	send_packet();
    	recv_packet();
    	statistics(SIGALRM);
    	
    	return 0;
    }