linux c ping实现

心已赠人 2021-08-24 17:42 404阅读 0赞

代码：

/********************************************************
     *  IP报头格式数据结构定义在<netinet/ip.h>中  *
     *  ICMP数据结构定义在<netinet/ip_icmp.h>中       *
     *  套接字地址数据结构定义在<netinet/in.h>中   *
     ********************************************************/
     
    #include <stdio.h>
    #include <stdlib.h>
    #include <signal.h>
    #include <arpa/inet.h>
    #include <sys/types.h>
    #include <sys/socket.h>
    #include <unistd.h>
    #include <netinet/in.h>
    #include <netinet/ip.h>
    #include <netinet/ip_icmp.h>
    #include <netdb.h>
    #include <setjmp.h>
    #include <errno.h>
     
    #define PACKET_SIZE 4096
    #define MAX_WAIT_TIME   5
    #define MAX_NO_PACKETS  10000
     
     
    char *addr[];
    char sendpacket[PACKET_SIZE];
    char recvpacket[PACKET_SIZE];
    int sockfd,datalen = 56;
    int nsend = 0, nreceived = 0;
    double temp_rtt[MAX_NO_PACKETS];
    double all_time = 0;
    double min = 0;
    double max = 0;
    double avg = 0;
    double mdev = 0;
     
    struct sockaddr_in dest_addr;
    struct sockaddr_in from;
    struct timeval tvrecv;
    pid_t pid;
     
    void statistics(int sig);
    void send_packet(void);
    void recv_packet(void);
    void computer_rtt(void);
    void tv_sub(struct timeval *out,struct timeval *in);
    int pack(int pack_no);
    int unpack(char *buf,int len);
    unsigned short cal_checksum(unsigned short *addr,int len);
     
    /*计算rtt最小、大值，平均值，算术平均数差*/
    void computer_rtt()
    {
        double sum_avg = 0;
        int i;
        min = max = temp_rtt[0];
        avg = all_time/nreceived;
     
        for(i=0; i<nreceived; i++){
            if(temp_rtt[i] < min)
                min = temp_rtt[i];
            else if(temp_rtt[i] > max)
                max = temp_rtt[i];
     
            if((temp_rtt[i]-avg) < 0)
                sum_avg += avg - temp_rtt[i];
            else
                sum_avg += temp_rtt[i] - avg; 
            }
        mdev = sum_avg/nreceived;
    }
     
    /****统计数据函数****/
    void statistics(int sig)
    {
        computer_rtt();     //计算rtt
        printf("\n------ %s ping statistics ------\n",addr[0]);
        printf("%d packets transmitted,%d received,%d%% packet loss,time %.f ms\n",
            nsend,nreceived,(nsend-nreceived)/nsend*100,all_time);
        printf("rtt min/avg/max/mdev = %.3f/%.3f/%.3f/%.3f ms\n",
            min,avg,max,mdev);
        close(sockfd);
        exit(1);
    }
     
    /****检验和算法****/
    unsigned short cal_chksum(unsigned short *addr,int len)
    {
        int nleft = len;
        int sum = 0;
        unsigned short *w = addr;
        unsigned short check_sum = 0;
     
        while(nleft>1)       //ICMP包头以字（2字节）为单位累加
        {
            sum += *w++;
            nleft -= 2;
        }
     
        if(nleft == 1)      //ICMP为奇数字节时，转换最后一个字节，继续累加
        {
            *(unsigned char *)(&check_sum) = *(unsigned char *)w;
            sum += check_sum;
        }
        sum = (sum >> 16) + (sum & 0xFFFF);
        sum += (sum >> 16);
        check_sum = ~sum;   //取反得到校验和
        return check_sum;
    }
     
    /*设置ICMP报头*/
    int pack(int pack_no)
    {
        int i,packsize;
        struct icmp *icmp;
        struct timeval *tval;
        icmp = (struct icmp*)sendpacket;
        icmp->icmp_type = ICMP_ECHO; //ICMP_ECHO类型的类型号为0
        icmp->icmp_code = 0;
        icmp->icmp_cksum = 0;
        icmp->icmp_seq = pack_no;    //发送的数据报编号
        icmp->icmp_id = pid;
     
        packsize = 8 + datalen;     //数据报大小为64字节
        tval = (struct timeval *)icmp->icmp_data;
        gettimeofday(tval,NULL);        //记录发送时间
        //校验算法
        icmp->icmp_cksum =  cal_chksum((unsigned short *)icmp,packsize); 
        return packsize;
    }
     
    /****发送三个ICMP报文****/
    void send_packet()
    {
        int packetsize;
        if(nsend < MAX_NO_PACKETS)
        {
            nsend++;
            packetsize = pack(nsend);   //设置ICMP报头
            //发送数据报
            if(sendto(sockfd,sendpacket,packetsize,0,
                (struct sockaddr *)&dest_addr,sizeof(dest_addr)) < 0)
            {
                perror("sendto error");
            }
        }
     
    }
     
     
    /****接受所有ICMP报文****/
    void recv_packet()
    {
        int n,fromlen;
        extern int error;
        fromlen = sizeof(from);
        if(nreceived < nsend)
        {   
            //接收数据报
            if((n = recvfrom(sockfd,recvpacket,sizeof(recvpacket),0,
                (struct sockaddr *)&from,&fromlen)) < 0)
            {
                perror("recvfrom error");
            }
            gettimeofday(&tvrecv,NULL);     //记录接收时间
            unpack(recvpacket,n);       //剥去ICMP报头
            nreceived++;
        }
    }
     
     
    /******剥去ICMP报头******/
    int unpack(char *buf,int len)
    {
        int i;
        int iphdrlen;       //ip头长度
        struct ip *ip;
        struct icmp *icmp;
        struct timeval *tvsend;
        double rtt;
     
     
        ip = (struct ip *)buf;
        iphdrlen = ip->ip_hl << 2; //求IP报文头长度，即IP报头长度乘4
        icmp = (struct icmp *)(buf + iphdrlen); //越过IP头，指向ICMP报头
        len -= iphdrlen;    //ICMP报头及数据报的总长度
        if(len < 8)      //小于ICMP报头的长度则不合理
        {
            printf("ICMP packet\'s length is less than 8\n");
            return -1;
        }
        //确保所接收的是所发的ICMP的回应
        if((icmp->icmp_type == ICMP_ECHOREPLY) && (icmp->icmp_id == pid))
        {
            tvsend = (struct timeval *)icmp->icmp_data;
            tv_sub(&tvrecv,tvsend); //接收和发送的时间差
            //以毫秒为单位计算rtt
            rtt = tvrecv.tv_sec*1000 + tvrecv.tv_usec/1000;
            temp_rtt[nreceived] = rtt;
            all_time += rtt;    //总时间
            //显示相关的信息
            printf("%d bytes from %s: icmp_seq=%u ttl=%d time=%.1f ms\n",
                    len,inet_ntoa(from.sin_addr),
                    icmp->icmp_seq,ip->ip_ttl,rtt);
        }
        else return -1;
    }
     
     
    //两个timeval相减
    void tv_sub(struct timeval *recvtime,struct timeval *sendtime)
    {
        long sec = recvtime->tv_sec - sendtime->tv_sec;
        long usec = recvtime->tv_usec - sendtime->tv_usec;
        if(usec >= 0){
            recvtime->tv_sec = sec;
            recvtime->tv_usec = usec;
        }else{
            recvtime->tv_sec = sec - 1;
            recvtime->tv_usec = -usec;
        }
    }
     
    /*主函数*/
    main(int argc,char *argv[])
    {
        struct hostent *host;
        struct protoent *protocol;
        unsigned long inaddr = 0;
    //  int waittime = MAX_WAIT_TIME;
        int size = 50 * 1024;
        addr[0] = argv[1];
        //参数小于两个
        if(argc < 2)     
        {
            printf("usage:%s hostname/IP address\n",argv[0]);
            exit(1);
        }
        //不是ICMP协议
        if((protocol = getprotobyname("icmp")) == NULL)
        {
            perror("getprotobyname");
            exit(1);
        }
     
        //生成使用ICMP的原始套接字，只有root才能生成
        if((sockfd = socket(AF_INET,SOCK_RAW,protocol->p_proto)) < 0)
        {
            perror("socket error");
            exit(1);
        }
     
        //回收root权限，设置当前权限
        setuid(getuid());
     
        /*扩大套接字的接收缓存区导50K，这样做是为了减小接收缓存区溢出的
          可能性，若无意中ping一个广播地址或多播地址，将会引来大量的应答*/
        setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size));
        bzero(&dest_addr,sizeof(dest_addr));    //初始化
        dest_addr.sin_family = AF_INET;     //套接字域是AF_INET(网络套接字)
     
        //判断主机名是否是IP地址
        if(inet_addr(argv[1]) == INADDR_NONE)
        {
            if((host = gethostbyname(argv[1])) == NULL) //是主机名
            {
                perror("gethostbyname error");
                exit(1);
            }
            memcpy((char *)&dest_addr.sin_addr,host->h_addr,host->h_length);
        }
        else{ //是IP 地址
            dest_addr.sin_addr.s_addr = inet_addr(argv[1]);
        }
        pid = getpid();
        printf("PING %s(%s):%d bytes of data.\n",argv[1],
                inet_ntoa(dest_addr.sin_addr),datalen);
     
        //当按下ctrl+c时发出中断信号，并开始执行统计函数
        signal(SIGINT,statistics);  
        while(nsend < MAX_NO_PACKETS){
            sleep(1);       //每隔一秒发送一个ICMP报文
            send_packet();      //发送ICMP报文
            recv_packet();      //接收ICMP报文
        }
        return 0;
    }

运行结果：

![format_png][]

[format_png]: /images/20210728/6d56f2b2c11e4e439cfa051a7560825c.png