- 参考链接:http://www.jb51.cc/article/p-ehzxwqqp-zr.html
- http://blog.csdn.net/petershina/article/details/8571562
- http://www.cnblogs.com/noble/p/4144139.html
- http://www.jb51.cc/article/p-qxsxpcrq-tm.html
- ping程序使用原始套接字,发送以太网首部+ip首部+icmp首部+56字节的数据
- 在发送时将icmp标志设置为进程pid,同时icmp序列号由1递增,数据部分为发送时的时间,在icmp应答报文中将请求回显报文中的标志位和数据原封不动的返回,便于计算往返时延rtt。
- icmp报头+数据 检验采用循环二进制反码求和
- 流程:创建通信的套接字-->将地址、端口信息与套接字绑定-->构建IP包头与ICMP包头-->发送构建的数据包-->接收对方主机的回应-->给出程序反馈信息
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编译时要加上-lpthread
包含头文件了,仅能说明有了线程函数的声明, 但是还没有实现, 加上-lpthread是在链接阶段,链接这个库
- 写注释时注意别在注释外面写全角空格和英文,编译器不识别
- protoent结构:
struct protoent{ char *p_name; //网络协议名 char **p_aliases;//别名 int p_proto;//网络协议编号 }
- ip结构
typedef struct _ip_hdr { #if LITTLE_ENDIAN unsigned char ihl:4; //首部长度 unsigned char version:4,//版本 #else unsigned char version:4,//版本 unsigned char ihl:4; //首部长度 #endif unsigned char tos; //服务类型 unsigned short tot_len; //总长度 unsigned short id; //标志 unsigned short frag_off; //分片偏移 unsigned char ttl; //生存时间 unsigned char protocol; //协议 unsigned short chk_sum; //检验和 struct in_addr srcaddr; //源IP地址 struct in_addr dstaddr; //目的IP地址 }ip_hdr;
- icmp结构
typedef struct _icmphdr{ unsigned char i_type; //8位类型,本实验用 8: ECHO 0:ECHO REPLY unsigned char i_code; //8位代码,本实验置零 unsigned short i_cksum; //16位校验和,从TYPE开始,直到最后一位用户数据,如果为字节数为奇数则补充一位 unsigned short i_id ; //识别号(一般用进程号作为识别号),用于匹配ECHO和ECHO REPLY包 unsigned short i_seq ; //报文序列号,用于标记ECHO报文顺序 unsigned int timestamp; //时间戳 }ICMP_HEADER;
- 实现代码:
#include<stdio.h> #include<stdlib.h> #include<signal.h> #include<unistd.h> #include<netinet/ip_icmp.h> #include<netdb.h>/*名字与地址转换*/ #include<string.h> #include<sys/types.h> #include<sys/socket.h> #include<sys/time.h> #include<netinet/in.h>/*字节排序*/ #include<arpa/inet.h>/*字符串与网络字节序转化*/ #include<pthread.h> struct sockaddr_in dst_addr; struct sockaddr_in recv_addr; struct timeval tvrecv; char icmp_pkt[1024]={0}; char recv_pkt[1024]={0}; int sockfd=0,bytes=56,nsend_pkt = 0,nrecv_pkt = 0; pid_t pid; void statistics(); int in_chksum(unsigned short * buf,int size);/*检验和算法*/ int pack(int send_pkt);/*设置icmp报头*/ void *send_ping();/*发送三个icmp报文*/ int unpack(char *recv_pkt,int size);/*剥去icmp报头*/ void *recv_ping();/*接受所有icmp报文*/ void tv_sub(struct timeval *out,struct timeval *in);/*两个time_val结构相减*/ /*struct protoent{ char *p_name; //网络协议名 char **p_aliases;//别名 int p_proto;//网络协议编号 } */ int main(int argc,char *argv[]) { int size = 50 * 1024; int errno=-1; int ttl=64; void *tret; pthread_t send_id,recv_id; struct in_addr ipv4_addr; struct hostent *ipv4_host; struct protoent *protocol = NULL; if(argc < 2 ) { printf("Usage : ./ping <host>\n"); exit(1); } if((protocol = getprotobyname("icmp")) == NULL)/*不可重入,线程不安全*/ { printf("unkown protocol\n"); exit(1); } /*使用原始套接字,只有root权限才可以创建,以太网首部+ip首部+icmp首部+56字节的数据,直接使用底层协议*/ if((sockfd=socket(AF_INET,SOCK_RAW,protocol->p_proto)) < 0) { printf("socket fail\n"); exit(1); } /*回收root权限,设置当前实际用户权限。*/ setuid(getuid()); /*扩大套件字接受缓冲区到50k,避免缓冲区溢出的可能性,若无意中ping一个广播或多播地址,可能会收到大量应答*/ setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size)); /*指定为IPPROTO_IP级别,制定外出TTL。*/ setsockopt(sockfd,IPPROTO_IP,IP_MULTICAST_TTL,&ttl,sizeof(ttl)); /*指定存活时间*/ setsockopt(sockfd,IP_TTL,sizeof(ttl)); /*memset(&dst_addr,sizeof(dst_addr));*/ bzero(&dst_addr,sizeof(dst_addr)); dst_addr.sin_family=AF_INET; errno=inet_aton(argv[1],&ipv4_addr); if(errno == 0) { ipv4_host = gethostbyname(argv[1]); if(ipv4_host == NULL) { printf("connect: Invalid argument\n"); return -1; } dst_addr.sin_addr=*((struct in_addr *)ipv4_host->h_addr); } else { dst_addr.sin_addr= ipv4_addr; } pid=getpid(); printf("PING %s (%s) %d bytes of data.\n",argv[1],inet_ntoa(dst_addr.sin_addr),bytes); signal(SIGINT,statistics); if((errno=pthread_create(&send_id,NULL,send_ping,NULL)) !=0) { printf("send_ping thread fail\n"); exit(1); } if((errno=pthread_create(&recv_id,recv_ping,NULL)) !=0) { printf("recv_ping thread fail\n"); exit(1); } if((errno =pthread_join(send_id,&tret)) !=0) { printf("can't join with thread send"); exit(1); } if((errno =pthread_join(recv_id,&tret)) != 0) { printf("can't join with thread recv"); exit(1); } return 0; } /*在收到终端信号时,输出ping 的检测状态 */ void statistics() { printf("\n--- %s ping statistics ---\n",inet_ntoa(dst_addr.sin_addr)); printf("%d packets transmitted,%d recvived,%.3f%c packet loss\n",nsend_pkt,nrecv_pkt,(float)100*(nsend_pkt-nrecv_pkt)/nsend_pkt,'%'); close(sockfd); exit(0); } /*校验和算法 icmp首部+数据*/ int in_chksum(unsigned short *buf,int size) { int nleft=size; int sum=0; unsigned short *w=buf; unsigned short ans=0; /*将ICMP二进制数据以两个字节相加*/ while(nleft > 1) { sum+=*w; /*相加16bits*/ w++; /* 移动sizeof(short)2个大小的字节*/ nleft-=2; } /*若只剩下一个字节的数据,则将最后一个字节视为两个字节的高字节,低字节视为0,继续相加*/ if(nleft == 1) { *(unsigned char *)(&ans)= *(unsigned char *)w; sum+=ans; } /*将高16位与低16位相加,可能产生进位,故第二次移位相加*/ sum=(sum>>16)+(sum & 0xFFFF); sum+=(sum>>16); ans=~sum; return ans; } int pack(int send_pkt) { struct icmp *pkt= (struct icmp *)icmp_pkt; struct timeval *time=NULL; pkt->icmp_type = ICMP_ECHO; pkt->icmp_code = 0; pkt->icmp_cksum= 0; pkt->icmp_seq= htons(send_pkt); pkt->icmp_id = pid; time = (struct timeval *)pkt->icmp_data; gettimeofday(time,NULL);/*记录发送时间*/ pkt->icmp_cksum=in_chksum((unsigned short *)pkt,bytes + 8);/*进行校验*/ return bytes + 8; } void *send_ping() { int send_bytes=0; int ret=-1; while(1) { nsend_pkt++; send_bytes= pack(nsend_pkt); ret=sendto(sockfd,icmp_pkt,send_bytes,(struct sockaddr *)&dst_addr,sizeof(dst_addr)); if(ret == -1) printf("send fail \n"); sleep(1); } } void tv_sub(struct timeval *out,struct timeval *in) { if((out->tv_usec-=in->tv_usec) < 0) { --out->tv_sec; out->tv_usec+=1000000; } out->tv_sec-=in->tv_sec; } int unpack(char *recv_pkt,int size) { struct iphdr *ip= NULL; int iphdrlen; struct icmp *icmp; struct timeval *tvsend; double rtt; ip = (struct iphdr *)recv_pkt; iphdrlen = ip->ihl<<2;/*求ip报头的长度,单位为4个字节*/ icmp = (struct icmp *)(recv_pkt + iphdrlen); size-=iphdrlen; if(size <8)/*小于icmp报头长度则不合理*/ { printf("ICMP size is less than 8\n"); exit(1); } if((icmp->icmp_type == ICMP_ECHOREPLY) && (icmp->icmp_id == pid)) { tvsend = (struct timeval *)icmp->icmp_data; tv_sub(&tvrecv,tvsend); rtt = tvrecv.tv_sec * 1000 + (double)tvrecv.tv_usec /(double)1000; printf("%d byte from %s: icmp_seq = %d ttl=%d rtt=%.3fms\n",size,inet_ntoa(recv_addr.sin_addr),ntohs(icmp->icmp_seq),ip->ttl,rtt); } else { return -1; } return 0; } void *recv_ping() { fd_set rd_set; struct timeval time; time.tv_sec = 5; time.tv_usec =0; int ret = 0,nread =0,recv_len =0; recv_len= sizeof(recv_addr); while(1) { FD_ZERO(&rd_set); FD_SET(sockfd,&rd_set); ret=select(sockfd+1,&rd_set,&time); if(ret <= 0) continue; else if(FD_ISSET(sockfd,&rd_set)) { nread=recvfrom(sockfd,recv_pkt,sizeof(recv_pkt),(struct sockaddr *)&recv_addr,(socklen_t *)&recv_len); if(nread < 0) continue; gettimeofday(&tvrecv,NULL); if(unpack(recv_pkt,nread) == -1) continue; nrecv_pkt++; } } }
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