ping 的实现

项目功能：模拟dos界面下的ping功能

项目名称：ping 的实现

开发环境：Linux/C

注：  函数中具体API的调用及原理清参考草根老师的博客

调试效果：

1.myping.c#include <stdio.h>#include <stdlib.h>#include <string.h>#include <errno.h>#include <sys/socket.h>#include <sys/types.h>#include <netinet/in.h>#include <arpa/inet.h>#include <netdb.h>#include <sys/time.h>#include <netinet/ip_icmp.h>#include <unistd.h>#include <signal.h>#define MAX_SIZE 1024char send_buf[MAX_SIZE];char recv_buf[MAX_SIZE];int nsend = 0,nrecv = 0;int datalen = 56;//统计结果void statistics(int signum){printf("\n----------------PING statistics---------------\n");printf("%d packets transmitted,%d recevid,%%%.2f lost\n",nsend,nrecv,(float)(nsend - nrecv)/nsend * 100);exit(EXIT_SUCCESS);}//校验和算法int calc_chsum(unsigned short *addr,int len){int sum = 0,n = len;unsigned short answer = 0;unsigned short *p = addr;//每两个字节相加while(n > 1){sum += *p ++;n -= 2;}//处理数据大小是奇数，在最后一个字节后面补0if(n == 1){*((unsigned char *)&answer) = *(unsigned char *)p;sum += answer;}//将得到的sum值的高2字节和低2字节相加sum = (sum >> 16) + (sum & 0xffff);//处理溢出的情况sum += sum >> 16;answer = ~sum;return answer;}int pack(int pack_num){int packsize;struct icmp *icmp;struct timeval *tv;icmp = (struct icmp *)send_buf;icmp->icmp_type = ICMP_ECHO;icmp->icmp_code = 0;icmp->icmp_cksum = 0;icmp->icmp_id = htons(getpid());icmp->icmp_seq = htons(pack_num);tv = (struct timeval *)icmp->icmp_data;//记录发送时间if(gettimeofday(tv,NULL) < 0){perror("Fail to gettimeofday");return -1;}packsize = 8 + datalen;icmp->icmp_cksum = calc_chsum((unsigned short *)icmp,packsize);return packsize;}int send_packet(int sockfd,struct sockaddr *paddr){int packsize;//将send_buf填上amemset(send_buf,'a',sizeof(send_buf));nsend ++;//打icmp包packsize = pack(nsend);if(sendto(sockfd,send_buf,packsize,0,paddr,sizeof(struct sockaddr)) < 0){perror("Fail to sendto");return -1;}return 0;}struct timeval  time_sub(struct timeval *tv_send,struct timeval *tv_recv){struct timeval ts;if(tv_recv->tv_usec - tv_send->tv_usec < 0){tv_recv->tv_sec --;tv_recv->tv_usec += 1000000;}ts.tv_sec = tv_recv->tv_sec - tv_send->tv_sec;ts.tv_usec = tv_recv->tv_usec - tv_send->tv_usec;return ts;}int unpack(int len,struct timeval *tv_recv,struct sockaddr *paddr,char *ipname){struct ip *ip;struct icmp *icmp;struct timeval *tv_send,ts;int ip_head_len;float rtt;ip = (struct ip *)recv_buf;ip_head_len = ip->ip_hl << 2;icmp = (struct icmp *)(recv_buf + ip_head_len);len -= ip_head_len;if(len < 8){printf("ICMP packets\'s is less than 8.\n");return -1;}tv_send = (struct timeval *)icmp->icmp_data;ts = time_sub(tv_send,tv_recv);rtt = ts.tv_sec * 1000 + (float)ts.tv_usec/1000;//以毫秒为单位if(ntohs(icmp->icmp_id) == getpid() && icmp->icmp_type == ICMP_ECHOREPLY){nrecv ++;printf("%d bytes from %s (%s):icmp_req = %d ttl=%d rtt=%.3fms.\n",len,ipname,inet_ntoa(((struct sockaddr_in *)paddr)->sin_addr),ntohs(icmp->icmp_seq),ip->ip_ttl,rtt);}return 0;}int recv_packet(int sockfd,char *ipname){int addr_len ,n;struct timeval tv;struct sockaddr from_addr;addr_len = sizeof(struct sockaddr);memset(recv_buf,0,sizeof(recv_buf));if((n = recvfrom(sockfd,recv_buf,sizeof(recv_buf),0,&from_addr,&addr_len)) < 0){perror("Fail to recvfrom");return -1;}if(gettimeofday(&tv,NULL) < 0){perror("Fail to gettimeofday");return -1;}unpack(n,&tv,&from_addr,ipname);return 0;}//myping 192.168.0.1 || myping www.baidu.comint main(int argc,char *argv[]){int size = 50 * 1024;int sockfd,netaddr;struct protoent *protocol;struct hostent *host;struct sockaddr_in peer_addr;if(argc < 2){fprintf(stderr,"usage : %s ip.\n",argv[0]);exit(EXIT_FAILURE);}//获取icmp的信息if((protocol = getprotobyname("icmp")) ==  NULL){perror("Fail to getprotobyname");exit(EXIT_FAILURE);}//创建原始套接字if((sockfd = socket(AF_INET,SOCK_RAW,protocol->p_proto)) < 0){perror("Fail to socket");exit(EXIT_FAILURE);}//回收root权限,设置当前用户权限setuid(getuid());/* 扩大套接子接收缓冲区到50k，这样做主要为了减少接收缓冲区溢出的可能性 若无中意ping一个广播地址或多播地址，将会引来大量应答 */if(setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size)) < 0){perror("Fail to setsockopt");exit(EXIT_FAILURE);}//填充对方的地址bzero(&peer_addr,sizeof(peer_addr));peer_addr.sin_family = AF_INET;//判断是主机名(域名)还是ipif((netaddr = inet_addr(argv[1])) == INADDR_NONE){//是主机名（域名）if((host = gethostbyname(argv[1])) == NULL){fprintf(stderr,"%s unknown host : %s.\n",argv[0],argv[1]);exit(EXIT_FAILURE);}memcpy((char *)&peer_addr.sin_addr,host->h_addr,host->h_length);}else{//ip地址peer_addr.sin_addr.s_addr = netaddr;}//注册信号处理函数signal(SIGALRM,statistics);signal(SIGINT,statistics);alarm(5);//开始信息printf("PING %s(%s) %d bytes of data.\n",argv[1],inet_ntoa(peer_addr.sin_addr),datalen);//发送包文和接收报文while(1){send_packet(sockfd,(struct sockaddr *)&peer_addr);recv_packet(sockfd,argv[1]);alarm(5);sleep(1);}exit(EXIT_SUCCESS);}