#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 = ,nrecv = ;

int datalen = ;

//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 * );

    exit(EXIT_SUCCESS);

}

//校验和算法

int calc_chsum(unsigned short *addr,int len)

{

    int sum = ,n = len;

    unsigned short answer = ;

    unsigned short *p = addr;

    //每两个字节相加

    while(n > )

    {

        sum += *p ++;

        n -= ;

    }

    //处理数据大小是奇数，在最后一个字节后面补0

    if(n == )

    {

        *((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 >> ) + (sum & 0xffff);

    //处理溢出的情况

    sum += sum >> ;

    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 = ;

    icmp->icmp_cksum = ;

    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) < )

    {

        perror("Fail to gettimeofday");

        return -;

    }

    packsize =  + 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,,paddr,sizeof(struct sockaddr)) < )

    {

        perror("Fail to sendto");

        return -;

    }

    return ;

}

struct timeval time_sub(struct timeval *tv_send,struct timeval *tv_recv)

{

    struct timeval ts;

    if(tv_recv->tv_usec - tv_send->tv_usec < )

    {

        tv_recv->tv_sec --;

        tv_recv->tv_usec += ;

    }

    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 << ;

    icmp = (struct icmp *)(recv_buf + ip_head_len);

    len -= ip_head_len;

    if(len < )

    {

        printf("ICMP packets\'s is less than 8.\n");

        return -;

    }

    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 *  + (float)ts.tv_usec/;//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 ;

}

int recv_packet(int sockfd,char *ipname)

{

    int addr_len ,n;

    struct timeval tv;

    struct sockaddr from_addr;

    addr_len = sizeof(struct sockaddr);

    if((n = recvfrom(sockfd,recv_buf,sizeof(recv_buf),,&from_addr,&addr_len)) < )

    {

        perror("Fail to recvfrom");

        return -;

    }

    if(gettimeofday(&tv,NULL) < )

    {

        perror("Fail to gettimeofday");

        return -;

    }

    unpack(n,&tv,&from_addr,ipname);

    return ;

}

int main(int argc,char *argv[])

{

    int size =  * ;

    int sockfd,netaddr;

    struct protoent *protocol;

    struct hostent *host;

    struct sockaddr_in peer_addr;

    if(argc < )

    {

        fprintf(stderr,"usage : %s ip.\n",argv[]);

        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)) < )

    {

        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)) < )

    {

        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[])) == INADDR_NONE)

    {

        //是主机名（域名）

        if((host = gethostbyname(argv[])) == NULL)

        {

            fprintf(stderr,"%s unknown host : %s.\n",argv[],argv[]);

            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();

    //开始信息

    printf("PING %s(%s) %d bytes of data.\n",argv[],inet_ntoa(peer_addr.sin_addr),datalen);

    //发送包文和接收报文

    while()

    {

        send_packet(sockfd,(struct sockaddr *)&peer_addr);

        recv_packet(sockfd,argv[]);

        alarm();

        sleep();

    }

    exit(EXIT_SUCCESS);

}