Linux用ICMP協議實現簡單Ping網路監測功能

ICMP是（Internet Control Message Protocol）Internet控制報文協議。它是TCP/IP協議族的一個子協議，用於在IP主機、路由器之間傳遞控制訊息。控制訊息是指網路通不通、主機是否可達、路由是否可用等網路本身的訊息。這些控制訊息雖然並不傳輸使用者資料，但是對於使用者資料的傳遞起著重要的作用。ICMP協議是一種面向不需連線的協議，用於傳輸出錯報告控制資訊。它是一個非常重要的協議，它對於網路安全具有極其重要的意義。
折騰半天，原來ICMP也是TCP/IP其中一種協議.那麼監測網路是否ping的通，就跟TCP協議差不多了。 步驟簡單歸納為：1.綁定通訊端，2.發送資料包 3.接收資料包 4.解析資料包

#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//效驗演算法（百度下有注釋，但是還是看不太明白）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函數int ping( char *ips, int timeout)  {          struct timeval *tval;            int maxfds = 0;      fd_set readfds;          struct sockaddr_in addr;      struct sockaddr_in from;      // 設定Ip資訊      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\n",ips);          return ERROR;      }          struct timeval timeo;      // 設定TimeOut時間      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\n",ips);          return ERROR;      }          char sendpacket[PACKET_SIZE];      char recvpacket[PACKET_SIZE];      // 設定Ping包      memset(sendpacket, 0, sizeof(sendpacket));          pid_t pid;      // 取得PID，作為Ping的Sequence ID      pid=getpid();          struct ip *iph;      struct icmp *icmp;            icmp=(struct icmp*)sendpacket;      icmp->icmp_type=ICMP_ECHO;  //回應要求    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));  //校正        int n;      // 發包      n = sendto(sockfd, (char *)&sendpacket, sizeof(struct icmp), 0, (struct sockaddr *)&addr, sizeof(addr));      if (n < 1)      {          printf("ip:%s,sendto error\n",ips);          return ERROR;      }          // 接受      // 由於可能接受到其他Ping的應答訊息，所以這裡要用迴圈      while(1)      {          // 設定TimeOut時間，這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\n",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);              // 判斷是否是自己Ping的回複          if (strcmp(from_ip,ips) != 0)          {              printf("NowPingip:%s Fromip:%s\nNowPingip is not same to Fromip,so ping wrong!\n",ips,from_ip);     return ERROR;        }                  iph = (struct ip *)recvpacket;                  icmp=(struct icmp *)(recvpacket + (iph->ip_hl<<2));                  printf("ip:%s\n,icmp->icmp_type:%d\n,icmp->icmp_id:%d\n",ips,icmp->icmp_type,icmp->icmp_id);          // 判斷Ping回複包的狀態          if (icmp->icmp_type == ICMP_ECHOREPLY && icmp->icmp_id == pid)   //ICMP_ECHOREPLY回顯應答        {              // 正常就退出迴圈              break;          }          else          {              // 否則繼續等              continue;          }      }          int main(){char cPing[16];printf("Please input ping IP:");scanf("%s",cPing);if(ping(cPing,10000)){printf("Ping succeed!\n");}else{printf("Ping wrong!\n");}}

測試結果：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!