Linux下模拟ping命令的C代码实现1

/******************************************************** * IP报头格式数据结构定义在<netinet/ip.h>中 * * ICMP数据结构定义在<netinet/ip_icmp.h>中 * * 套接字地址数据结构定义在<netinet/in.h>中 * ********************************************************/ #include <stdio.h> #include <stdlib.h> #include <signal.h> #include <arpa/inet.h> #include <sys/types.h> #include <sys/socket.h> #include <unistd.h> #include <netinet/in.h> #include <netinet/ip.h> #include <netinet/ip_icmp.h> #include <netdb.h> #include <setjmp.h> #include <errno.h> #define PACKET_SIZE 4096 #define MAX_WAIT_TIME 5 #define MAX_NO_PACKETS 10000 char *addr[]; char sendpacket[PACKET_SIZE]; char recvpacket[PACKET_SIZE]; int sockfd,datalen = 56; int nsend = 0, nreceived = 0; double temp_rtt[MAX_NO_PACKETS]; double all_time = 0; double min = 0; double max = 0; double avg = 0; double mdev = 0; struct sockaddr_in dest_addr; struct sockaddr_in from; struct timeval tvrecv; pid_t pid; void statistics(int sig); void send_packet(void); void recv_packet(void); void computer_rtt(void); void tv_sub(struct timeval *out,struct timeval *in); int pack(int pack_no); int unpack(char *buf,int len); unsigned short cal_checksum(unsigned short *addr,int len); /*计算rtt最小、大值，平均值，算术平均数差*/ void computer_rtt() { double sum_avg = 0; int i; min = max = temp_rtt[0]; avg = all_time/nreceived; for(i=0; i<nreceived; i++){ if(temp_rtt[i] < min) min = temp_rtt[i]; else if(temp_rtt[i] > max) max = temp_rtt[i]; if((temp_rtt[i]-avg) < 0) sum_avg += avg - temp_rtt[i]; else sum_avg += temp_rtt[i] - avg; } mdev = sum_avg/nreceived; } /****统计数据函数****/ void statistics(int sig) { computer_rtt(); //计算rtt printf("/n------ %s ping statistics ------/n",addr[0]); printf("%d packets transmitted,%d received,%d%% packet loss,time %.f ms/n", nsend,nreceived,(nsend-nreceived)/nsend*100,all_time); printf("rtt min/avg/max/mdev = %.3f/%.3f/%.3f/%.3f ms/n", min,avg,max,mdev); close(sockfd); exit(1); } /****检验和算法****/ unsigned short cal_chksum(unsigned short *addr,int len) { int nleft = len; int sum = 0; unsigned short *w = addr; unsigned short check_sum = 0; while(nleft>1) //ICMP包头以字（2字节）为单位累加 { sum += *w++; nleft -= 2; } if(nleft == 1) //ICMP为奇数字节时，转换最后一个字节，继续累加 { *(unsigned char *)(&check_sum) = *(unsigned char *)w; sum += check_sum; } sum = (sum >> 16) + (sum & 0xFFFF); sum += (sum >> 16); check_sum = ~sum; //取反得到校验和 return check_sum; } /*设置ICMP报头*/ int pack(int pack_no) { int i,packsize; struct icmp *icmp; struct timeval *tval; icmp = (struct icmp*)sendpacket; icmp->icmp_type = ICMP_ECHO; //ICMP_ECHO类型的类型号为0 icmp->icmp_code = 0; icmp->icmp_cksum = 0; icmp->icmp_seq = pack_no; //发送的数据报编号 icmp->icmp_id = pid; packsize = 8 + datalen; //数据报大小为64字节 tval = (struct timeval *)icmp->icmp_data; gettimeofday(tval,NULL); //记录发送时间 //校验算法 icmp->icmp_cksum = cal_chksum((unsigned short *)icmp,packsize); return packsize; } /****发送三个ICMP报文****/ void send_packet() { int packetsize; if(nsend < MAX_NO_PACKETS) { nsend++; packetsize = pack(nsend); //设置ICMP报头 //发送数据报 if(sendto(sockfd,sendpacket,packetsize,0, (struct sockaddr *)&dest_addr,sizeof(dest_addr)) < 0) { perror("sendto error"); } } } /****接受所有ICMP报文****/ void recv_packet() { int n,fromlen; extern int error; fromlen = sizeof(from); if(nreceived < nsend) { //接收数据报 if((n = recvfrom(sockfd,recvpacket,sizeof(recvpacket),0, (struct sockaddr *)&from,&fromlen)) < 0) { perror("recvfrom error"); } gettimeofday(&tvrecv,NULL); //记录接收时间 unpack(recvpacket,n); //剥去ICMP报头 nreceived++; } } /******剥去ICMP报头******/ int unpack(char *buf,int len) { int i; int iphdrlen; //ip头长度 struct ip *ip; struct icmp *icmp; struct timeval *tvsend; double rtt; ip = (struct ip *)buf; iphdrlen = ip->ip_hl << 2; //求IP报文头长度，即IP报头长度乘4 icmp = (struct icmp *)(buf + iphdrlen); //越过IP头，指向ICMP报头 len -= iphdrlen; //ICMP报头及数据报的总长度 if(len < 8) //小于ICMP报头的长度则不合理 { printf("ICMP packet/'s length is less than 8/n"); return -1; } //确保所接收的是所发的ICMP的回应 if((icmp->icmp_type == ICMP_ECHOREPLY) && (icmp->icmp_id == pid)) { tvsend = (struct timeval *)icmp->icmp_data; tv_sub(&tvrecv,tvsend); //接收和发送的时间差 //以毫秒为单位计算rtt rtt = tvrecv.tv_sec*1000 + tvrecv.tv_usec/1000; temp_rtt[nreceived] = rtt; all_time += rtt; //总时间 //显示相关的信息 printf("%d bytes from %s: icmp_seq=%u ttl=%d time=%.1f ms/n", len,inet_ntoa(from.sin_addr), icmp->icmp_seq,ip->ip_ttl,rtt); } else return -1; } //两个timeval相减 void tv_sub(struct timeval *recvtime,struct timeval *sendtime) { long sec = recvtime->tv_sec - sendtime->tv_sec; long usec = recvtime->tv_usec - sendtime->tv_usec; if(usec >= 0){ recvtime->tv_sec = sec; recvtime->tv_usec = usec; }else{ recvtime->tv_sec = sec - 1; recvtime->tv_usec = -usec; } } /*主函数*/ main(int argc,char *argv[]) { struct hostent *host; struct protoent *protocol; unsigned long inaddr = 0; // int waittime = MAX_WAIT_TIME; int size = 50 * 1024; addr[0] = argv[1]; //参数小于两个 if(argc < 2) { printf("usage:%s hostname/IP address/n",argv[0]); exit(1); } //不是ICMP协议 if((protocol = getprotobyname("icmp")) == NULL) { perror("getprotobyname"); exit(1); } //生成使用ICMP的原始套接字，只有root才能生成 if((sockfd = socket(AF_INET,SOCK_RAW,protocol->p_proto)) < 0) { perror("socket error"); exit(1); } //回收root权限，设置当前权限 setuid(getuid()); /*扩大套接字的接收缓存区导50K，这样做是为了减小接收缓存区溢出的 可能性，若无意中ping一个广播地址或多播地址，将会引来大量的应答*/ setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size)); bzero(&dest_addr,sizeof(dest_addr)); //初始化 dest_addr.sin_family = AF_INET; //套接字域是AF_INET(网络套接字) //判断主机名是否是IP地址 if(inet_addr(argv[1]) == INADDR_NONE) { if((host = gethostbyname(argv[1])) == NULL) //是主机名 { perror("gethostbyname error"); exit(1); } memcpy((char *)&dest_addr.sin_addr,host->h_addr,host->h_length); } else{ //是IP 地址 dest_addr.sin_addr.s_addr = inet_addr(argv[1]); } pid = getpid(); printf("PING %s(%s):%d bytes of data./n",argv[1], inet_ntoa(dest_addr.sin_addr),datalen); //当按下ctrl+c时发出中断信号，并开始执行统计函数 signal(SIGINT,statistics); while(nsend < MAX_NO_PACKETS){ sleep(1); //每隔一秒发送一个ICMP报文 send_packet(); //发送ICMP报文 recv_packet(); //接收ICMP报文 } return 0; }