C++实现简单的ping功能

青旅半醒 2021-09-19 04:10 691阅读 0赞

**一 代码**

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <errno.h>
    #include <sys/socket.h>
    #include <sys/types.h>
    #include <netinet/in.h>
    #include <arpa/inet.h>
    #include <netdb.h>
    #include <sys/time.h>
    #include <netinet/ip_icmp.h>
    #include <unistd.h>
    #include <signal.h>
    
    #define MAX_SIZE 1024
    
    char send_buf[MAX_SIZE];
    char recv_buf[MAX_SIZE];
    int nsend = 0, nrecv = 0;
    int datalen = 56;
    
        //统计结果
    void statistics(int signum)
    {
        printf("\n----------------PING statistics---------------\n");
        printf("%d packets transmitted,%d recevid,%%%d lost\n", nsend, nrecv, (nsend - nrecv) / nsend * 100);
        exit(EXIT_SUCCESS);
    }
    
        //校验和算法
    int calc_chsum(unsigned short *addr, int len)
    {
        int sum = 0, n = len;
        unsigned short answer = 0;
        unsigned short *p = addr;
            
        //每两个字节相加
        while (n > 1)
        {
            sum += *p++;
            n -= 2;
        }
            
        //处理数据大小是奇数，在最后一个字节后面补0
        if (n == 1)
        {
            *((unsigned char *)&answer) = *(unsigned char *)p;
            sum += answer;
        }
            
        //将得到的sum值的高2字节和低2字节相加
        sum = (sum >> 16) + (sum & 0xffff);
            
        //处理溢出的情况
        sum += sum >> 16;
        answer = ~sum;
    
        return answer;
    }
    
    int pack(int pack_num)
    {
        int packsize;
        struct icmp *icmp;
        struct timeval *tv;
    
        icmp = (struct icmp *)send_buf;
        icmp->icmp_type = ICMP_ECHO;
        icmp->icmp_code = 0;
        icmp->icmp_cksum = 0;
        icmp->icmp_id = htons(getpid());
        icmp->icmp_seq = htons(pack_num);
        tv = (struct timeval *)icmp->icmp_data;
    
                //记录发送时间
        if (gettimeofday(tv, NULL) < 0)
        {
            perror("Fail to gettimeofday");
            return -1;
        }
            
        packsize = 8 + datalen;
        icmp->icmp_cksum = calc_chsum((unsigned short *)icmp, packsize);
            
        return packsize;
    }
    
    int send_packet(int sockfd, struct sockaddr *paddr)
    {
        int packsize;
            
        //将send_buf填上a
        memset(send_buf, 'a', sizeof(send_buf));
    
        nsend++;
        //打icmp包
        packsize = pack(nsend);
    
        if (sendto(sockfd, send_buf, packsize, 0, paddr, sizeof(struct sockaddr)) < 0)
        {
            perror("Fail to sendto");
            return -1;
        }
    
        return 0;
    }
    
    struct timeval time_sub(struct timeval *tv_send, struct timeval *tv_recv)
    {
        struct timeval ts;
    
        if (tv_recv->tv_usec - tv_send->tv_usec < 0)
        {
            tv_recv->tv_sec--;
            tv_recv->tv_usec += 1000000;
        }
    
        ts.tv_sec = tv_recv->tv_sec - tv_send->tv_sec;
        ts.tv_usec = tv_recv->tv_usec - tv_send->tv_usec;
    
        return ts;
    }
    
    int unpack(int len, struct timeval *tv_recv, struct sockaddr *paddr, char *ipname)
    {
        struct ip *ip ;
        struct icmp *icmp ;
        struct timeval *tv_send,
         ts ;
        int ip_head_len ;
        float rtt ;
    
        ip = (struct ip *)recv_buf ;
        ip_head_len = ip->ip_hl << 2 ;
        icmp = (struct icmp *)(recv_buf + ip_head_len) ;
    
        len -= ip_head_len ;
        if(len < 8)
        {
            printf("ICMP packets\'s is less than 8.\n") ;
            return - 1 ;
        }
                
        if(ntohs(icmp->icmp_id) == getpid() && icmp->icmp_type == ICMP_ECHOREPLY)
        {
            nrecv++ ;
            tv_send = (struct timeval *)icmp->icmp_data ;
            ts = time_sub(tv_send, tv_recv) ;
            rtt = ts.tv_sec * 1000 + (float)ts.tv_usec / 1000 ;//以毫秒为单位
            printf("%d bytes from %s (%s):icmp_req = %d ttl=%d time=%.3fms.\n",
            len,
            ipname,
            inet_ntoa(((struct sockaddr_in *)paddr)->sin_addr),
            ntohs(icmp->icmp_seq),
            ip->ip_ttl,
            rtt) ;
        }
            
        return 0 ;
    }
    
    int recv_packet(int sockfd, char *ipname)
    {
        socklen_t addr_len,
         n ;
        struct timeval tv ;
        struct sockaddr from_addr ;
            
        addr_len = sizeof(struct sockaddr) ;
        if((n = recvfrom(sockfd, recv_buf, sizeof(recv_buf), 0,&from_addr, &addr_len)) < 0)
        {
            perror("Fail to recvfrom") ;
            return - 1 ;
        }
    
        if(gettimeofday(&tv, NULL) < 0)
        {
            perror("Fail to gettimeofday") ;
            return - 1 ;
        }
    
        unpack(n, &tv, &from_addr, ipname) ;
    
        return 0 ;
    }
    
    
    int main(int argc, char *argv[])
    {
        int size = 50 * 1024 ;
        int sockfd,
        netaddr ;
        struct protoent *protocol ;
        struct hostent *host ;
        struct sockaddr_in peer_addr ;
            
        if(argc < 2)
        {
            fprintf(stderr, "usage : %s ip.\n", argv[0]) ;
            exit(EXIT_FAILURE) ;
        }
            
        //获取icmp的信息
        if((protocol = getprotobyname("icmp")) == NULL)
        {
            perror("Fail to getprotobyname") ;
            exit(EXIT_FAILURE) ;
        }
            
        //创建原始套接字
        if((sockfd = socket(AF_INET, SOCK_RAW, protocol->p_proto)) < 0)
        {
            perror("Fail to socket") ;
            exit(EXIT_FAILURE) ;
        }
    
        //回收root权限,设置当前用户权限
        setuid(getuid()) ;
    
        /*
         扩大套接子接收缓冲区到50k，这样做主要为了减少接收缓冲区溢出的可能性
         若无影中ping一个广播地址或多播地址，将会引来大量应答
         */
        if(setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &size, sizeof(size)) < 0)
        {
            perror("Fail to setsockopt") ;
            exit(EXIT_FAILURE) ;
        }
    
        //填充对方的地址
        bzero(&peer_addr, sizeof(peer_addr)) ;
        peer_addr.sin_family = AF_INET ;
        //判断是主机名(域名)还是ip
        if((netaddr = inet_addr(argv[1])) == INADDR_NONE)
        {    
            //是主机名（域名）
            if((host = gethostbyname(argv[1])) == NULL)
            {
                fprintf(stderr, "%s unknown host : %s.\n", argv[0], argv[1]) ;
                exit(EXIT_FAILURE) ;
            }
    
            memcpy((char *)&peer_addr.sin_addr, host->h_addr, host->h_length) ;
                
        }
        else
        {//ip地址
            peer_addr.sin_addr.s_addr = netaddr ;
        }
                
        //注册信号处理函数
        signal(SIGALRM, statistics) ;
        signal(SIGINT, statistics) ;
        alarm(5) ;
    
        //打印开始信息
        printf("PING %s(%s) %d bytes of data.\n", argv[1], inet_ntoa(peer_addr.sin_addr), datalen) ;
    
        //发送包文和接收报文
        while(1)
        {
            send_packet(sockfd, (struct sockaddr *)&peer_addr) ;
            recv_packet(sockfd, argv[1]) ;
            alarm(5) ;
            sleep(1) ;
        }
    
        exit(EXIT_SUCCESS) ;    
    }

二 运行

[root@localhost test]# ./test 192.168.0.121
    PING 192.168.0.121(192.168.0.121) 56 bytes of data.
    ^C
    ----------------PING statistics---------------
    1 packets transmitted,0 recevid,%100 lost
    [root@localhost test]# ./test 192.168.0.120
    PING 192.168.0.120(192.168.0.120) 56 bytes of data.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 1 ttl=64 time=0.451ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 2 ttl=64 time=0.309ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 3 ttl=64 time=0.526ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 4 ttl=64 time=0.233ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 5 ttl=64 time=0.236ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 6 ttl=64 time=0.297ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 7 ttl=64 time=0.279ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 8 ttl=64 time=0.290ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 9 ttl=64 time=0.296ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 10 ttl=64 time=0.234ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 11 ttl=64 time=0.235ms.
    64 bytes from 192.168.0.120 (192.168.0.120):icmp_req = 12 ttl=64 time=0.294ms.
    ^C
    ----------------PING statistics---------------
    12 packets transmitted,12 recevid,%0 lost
    [root@localhost test]# ./test www.baidu.com
    PING www.baidu.com(220.181.111.37) 56 bytes of data.
    64 bytes from www.baidu.com (220.181.111.37):icmp_req = 1 ttl=54 time=28.862ms.
    64 bytes from www.baidu.com (220.181.111.37):icmp_req = 1 ttl=54 time=1029.613ms.
    64 bytes from www.baidu.com (220.181.111.37):icmp_req = 2 ttl=54 time=1001.167ms.
    64 bytes from www.baidu.com (220.181.111.37):icmp_req = 2 ttl=54 time=2001.564ms.
    64 bytes from www.baidu.com (220.181.111.37):icmp_req = 3 ttl=54 time=2001.395ms.
    64 bytes from www.baidu.com (220.181.111.37):icmp_req = 3 ttl=54 time=3001.786ms.
    ^C
    ----------------PING statistics---------------
    6 packets transmitted,6 recevid,%0 lost