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>#definePACKET_SIZE4096#defineMAX_WAIT_TIME5#defineMAX_NO_PACKETS10000char *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];elsesum_avg += temp_rtt[i] - avg; }mdev = sum_avg/nreceived;}/****统计数据函数****/void statistics(int sig){computer_rtt();//计算rttprintf("/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0icmp->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4icmp = (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rttrtt = 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;}