Linux用ICMP协议实现简单Ping网络监测功能

ICMP是（Internet Control Message Protocol）Internet控制报文协议。它是TCP/IP协议族的一个子协议，用于在IP主机、路由器之间传递控制消息。控制消息是指网络通不通、主机是否可达、路由是否可用等网络本身的消息。这些控制消息虽然并不传输用户数据，但是对于用户数据的传递起着重要的作用。

ICMP协议是一种面向无连接的协议，用于传输出错报告控制信息。它是一个非常重要的协议，它对于网络安全具有极其重要的意义。

 

折腾半天，原来ICMP也是TCP/IP其中一种协议.那么监测网络是否ping的通，就跟TCP协议差不多了。

步骤简单归纳为：1.绑定套接字，2.发送数据包 3.接收数据包 4.解析数据包

#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netdb.h>

#define PACKET_SIZE     4096
#define ERROR           0
#define SUCCESS         1

//效验算法（百度下有注释，但是还是看不太明白）
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;
}
// Ping函数
int ping( char *ips, int timeout)
{
    struct timeval *tval;
    int maxfds = 0;
    fd_set readfds;

    struct sockaddr_in addr;
    struct sockaddr_in from;
    // 设定Ip信息
    bzero(&addr,sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_addr.s_addr = inet_addr(ips);

    int sockfd;
    // 取得socket
    sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
    if (sockfd < 0)
    {
        printf("ip:%s,socket error
",ips);
        return ERROR;
    }

    struct timeval timeo;
    // 设定TimeOut时间
    timeo.tv_sec = timeout / 1000;
    timeo.tv_usec = timeout % 1000;

    if (setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, &timeo, sizeof(timeo)) == -1)
    {
        printf("ip:%s,setsockopt error
",ips);
        return ERROR;
    }

    char sendpacket[PACKET_SIZE];
    char recvpacket[PACKET_SIZE];
    // 设定Ping包
    memset(sendpacket, 0, sizeof(sendpacket));

    pid_t pid;
    // 取得PID，作为Ping的Sequence ID
    pid=getpid();

    struct ip *iph;
    struct icmp *icmp;


    icmp=(struct icmp*)sendpacket;
    icmp->icmp_type=ICMP_ECHO;  //回显请求
    icmp->icmp_code=0;
    icmp->icmp_cksum=0;
    icmp->icmp_seq=0;
    icmp->icmp_id=pid;
    tval= (struct timeval *)icmp->icmp_data;
    gettimeofday(tval,NULL);
    icmp->icmp_cksum=cal_chksum((unsigned short *)icmp,sizeof(struct icmp));  //校验

    int n;
    // 发包
    n = sendto(sockfd, (char *)&sendpacket, sizeof(struct icmp), 0, (struct sockaddr *)&addr, sizeof(addr));
    if (n < 1)
    {
        printf("ip:%s,sendto error
",ips);
        return ERROR;
    }

    // 接受
    // 由于可能接受到其他Ping的应答消息，所以这里要用循环
    while(1)
    {
        // 设定TimeOut时间，这次才是真正起作用的
        FD_ZERO(&readfds);
        FD_SET(sockfd, &readfds);
        maxfds = sockfd + 1;
        n = select(maxfds, &readfds, NULL, NULL, &timeo);
        if (n <= 0)
        {
            printf("ip:%s,Time out error
",ips);
            close(sockfd);
            return ERROR;
        }

        // 接受
        memset(recvpacket, 0, sizeof(recvpacket));
        int fromlen = sizeof(from);
        n = recvfrom(sockfd, recvpacket, sizeof(recvpacket), 0, (struct sockaddr *)&from, (socklen_t *)&fromlen);
        if (n < 1) {
            break;
        }


        char *from_ip = (char *)inet_ntoa(from.sin_addr);
            // 判断是否是自己Ping的回复
        if (strcmp(from_ip,ips) != 0)
        {
            printf("NowPingip:%s Fromip:%s
NowPingip is not same to Fromip,so ping wrong!
",ips,from_ip);
            return ERROR;
        }

        iph = (struct ip *)recvpacket;

        icmp=(struct icmp *)(recvpacket + (iph->ip_hl<<2));

        printf("ip:%s
,icmp->icmp_type:%d
,icmp->icmp_id:%d
",ips,icmp->icmp_type,icmp->icmp_id);
        // 判断Ping回复包的状态
        if (icmp->icmp_type == ICMP_ECHOREPLY && icmp->icmp_id == pid)   //ICMP_ECHOREPLY回显应答
        {
            // 正常就退出循环
            break;
        }
        else
        {
            // 否则继续等
            continue;
        }
    }

    int main()
{
    char cPing[16];
    printf("Please input ping IP:");
    scanf("%s",cPing);

    if(ping(cPing,10000))
    {
        printf("Ping succeed!
");
    }
    else
    {
        printf("Ping wrong!
");
    }

}

测试结果：

root@an-virtual-machine:~/wyz/test# ./testping
Please input ping IP:192.168.1.155
Nowip:192.168.1.155 Fromip:192.168.1.133
Nowip is not same to Fromip,so ping wrong!
Ping wrong!
root@an-virtual-machine:~/wyz/test# ./testping
Please input ping IP:192.168.1.188
ip:192.168.1.188
,icmp->icmp_type:0
,icmp->icmp_id:27865
Ping succeed!