Linux用ICMP協議實現簡單Ping網絡監測功能

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消息。控制消息是指網絡通不通、主機是否可達、路由是否可用等網絡本身的消息。這些控制消息雖然並不傳輸用戶數據，但是對於用戶數據的傳遞起著重要的作用。

ICMP協議是一種面向無連接的協議，用於傳輸出錯報告控制信息。它是一個非常重要的協議，它對於網絡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.那麼監測網絡是否ping的通，就跟TCP協議差不多了。

步驟簡單歸納為：1.綁定套接字，2.發送數據包 3.接收數據包 4.解析數據包

1. #include <stdio.h>
2. #include <sys/socket.h>
3. #include <netinet/in.h>
4. #include <netinet/ip.h>
5. #include <netinet/ip_icmp.h>
6. #include <netdb.h>

1. #define PACKET_SIZE 4096
2. #define ERROR 0
3. #define SUCCESS 1
5. //效驗算法（百度下有注釋，但是還是看不太明白）
6. unsigned short cal_chksum(unsigned short *addr, int len)
7. {
8. int nleft=len;
9. int sum=0;
10. unsigned short *w=addr;
11. unsigned short answer=0;
13. while(nleft > 1)
14. {
15. sum += *w++;
16. nleft -= 2;
17. }
19. if( nleft == 1)
20. {
21. *(unsigned char *)(&answer) = *(unsigned char *)w;
22. sum += answer;
23. }
25. sum = (sum >> 16) + (sum & 0xffff);
26. sum += (sum >> 16);
27. answer = ~sum;
29. return answer;
30. }
31. // Ping函數
32. int ping( char *ips, int timeout)
33. {
34. struct timeval *tval;
35. int maxfds = 0;
36. fd_set readfds;
38. struct sockaddr_in addr;
39. struct sockaddr_in from;
40. // 設定Ip信息
41. bzero(&addr,sizeof(addr));
42. addr.sin_family = AF_INET;
43. addr.sin_addr.s_addr = inet_addr(ips);
45. int sockfd;
46. // 取得socket
47. sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
48. if (sockfd < 0)
49. {
50. printf("ip:%s,socket error\n",ips);
51. return ERROR;
52. }
54. struct timeval timeo;
55. // 設定TimeOut時間
56. timeo.tv_sec = timeout / 1000;
57. timeo.tv_usec = timeout % 1000;
59. if (setsockopt(sockfd, SOL_SOCKET, SO_SNDTIMEO, &timeo, sizeof(timeo)) == -1)
60. {
61. printf("ip:%s,setsockopt error\n",ips);
62. return ERROR;
63. }
65. char sendpacket[PACKET_SIZE];
66. char recvpacket[PACKET_SIZE];
67. // 設定Ping包
68. memset(sendpacket, 0, sizeof(sendpacket));
70. pid_t pid;
71. // 取得PID，作為Ping的Sequence ID
72. pid=getpid();
74. struct ip *iph;
75. struct icmp *icmp;
78. icmp=(struct icmp*)sendpacket;
79. icmp->icmp_type=ICMP_ECHO; //回顯請求
80. icmp->icmp_code=0;
81. icmp->icmp_cksum=0;
82. icmp->icmp_seq=0;
83. icmp->icmp_id=pid;
84. tval= (struct timeval *)icmp->icmp_data;
85. gettimeofday(tval,NULL);
86. icmp->icmp_cksum=cal_chksum((unsigned short *)icmp,sizeof(struct icmp)); //校驗
88. int n;
89. // 發包
90. n = sendto(sockfd, (char *)&sendpacket, sizeof(struct icmp), 0, (struct sockaddr *)&addr, sizeof(addr));
91. if (n < 1)
92. {
93. printf("ip:%s,sendto error\n",ips);
94. return ERROR;
95. }
97. // 接受
98. // 由於可能接受到其他Ping的應答消息，所以這裡要用循環
99. while(1)
100. {
101. // 設定TimeOut時間，這次才是真正起作用的
102. FD_ZERO(&readfds);
103. FD_SET(sockfd, &readfds);
104. maxfds = sockfd + 1;
105. n = select(maxfds, &readfds, NULL, NULL, &timeo);
106. if (n <= 0)
107. {
108. printf("ip:%s,Time out error\n",ips);
109. close(sockfd);
110. return ERROR;
111. }
113. // 接受
114. memset(recvpacket, 0, sizeof(recvpacket));
115. int fromlen = sizeof(from);
116. n = recvfrom(sockfd, recvpacket, sizeof(recvpacket), 0, (struct sockaddr *)&from, (socklen_t *)&fromlen);
117. if (n < 1) {
118. break;
119. }
122. char *from_ip = (char *)inet_ntoa(from.sin_addr);
123. // 判斷是否是自己Ping的回復
124. if (strcmp(from_ip,ips) != 0)
125. {
126. printf("NowPingip:%s Fromip:%s\nNowPingip is not same to Fromip,so ping wrong!\n",ips,from_ip);
127. return ERROR;
128. }
130. iph = (struct ip *)recvpacket;
132. icmp=(struct icmp *)(recvpacket + (iph->ip_hl<<2));
134. printf("ip:%s\n,icmp->icmp_type:%d\n,icmp->icmp_id:%d\n",ips,icmp->icmp_type,icmp->icmp_id);
135. // 判斷Ping回復包的狀態
136. if (icmp->icmp_type == ICMP_ECHOREPLY && icmp->icmp_id == pid) //ICMP_ECHOREPLY回顯應答
137. {
138. // 正常就退出循環
139. break;
140. }
141. else
142. {
143. // 否則繼續等
144. continue;
145. }
146. }
148. int main()
149. {
150. char cPing[16];
151. printf("Please input ping IP:");
152. scanf("%s",cPing);
154. if(ping(cPing,10000))
155. {
156. printf("Ping succeed!\n");
157. }
158. else
159. {
160. printf("Ping wrong!\n");
161. }
163. }

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!