test12_7.txt

人民邮电出版社的经典著作《Linux下的C编程》配套源码！初学者的必备！共14章

//#include "headfile.h"
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/time.h>
#include <stdio.h>
#include <signal.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <errno.h>
#define BUFSIZE 1500

char recvbuf[BUFSIZE];
char sendbuf[BUFSIZE];
int datalen;
char *host;
int nsent;
pid_t pid;
int sockfd;
int verbose;
void proc(char *,ssize_t,struct timeval *);
void send(void);
void readloop(void);
void sig_alrm(int);
void tv_sub(struct timeval *,struct timeval *);
struct sockaddr_in *sasend;
struct sockaddr_in *sarecv;


/*main.c程序 */
//#include "ping.h"
int datalen=56;
/*数据可选长度为56字节 */
int main(int argc,char **argv)
{
	int c;
	struct addrinfo *ai;
	int opterr=0;
	while((c=getopt(argc,argv, "v"))!= -1)
	{
		switch(c)
		{
			case 'v':
				verbose++;
				break;
			case '?':
				err_quit("unrecognized option:%c",c);
		}
	}
    /*定义命令选项－v */
	if(opterr!=argc-1)
		err_quit("usage:ping[-v]<hostname>");
	host=argv[opterr];
	pid=getpid();
	signal(SIGALRM,sig_alrm);
    /*建立信号处理程序，发送ICMP请求*/
	ai=host_serv(host,NULL,0,0);
	printf("ping %s(%s):%d data bytes \n",ai->ai_cononname,
		sock_ntop_host(ai->ai_addr,ai->ai_addrlen),datalen);
	readloop();
    /*调用函数readloop执行接收ICMP应答*/
	exit(0);
}


/*函数readloop代码*/
//#include "ping.h"
void readloop(void)
{
	int size;
	char recvbuf[BUFSIZE];
	socklen_t len;
	ssize_t n;
	struct timeval tval;
	sockfd=socket(AF_INET,SOCK_RAW,IPPROTO_ICMP);
	setuid(getuid());
    /*创建一个原始套接口，协议为ICMP*/
	size=60*1024;
	setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size));
		/*设置接收缓冲区的大小 */
	sig_alrm(SIGALRM);
		/*调用信号处理程序发送一个请求*/
	for(;;)
	{
		len=sizeof(sarecv);
		n=recvfrom(sockfd,recvbuf,sizeof(recvbuf),0,sarecv,&len);
		if(n<0)
		{
			if(errno==EINTR)
				continue;
			else
				err_sys("recvfrom error\n");
		}
		gettimeofday(&tval,NULL);
		proc(recvbuf,n,&tval);
	}
/*进入无限循环，读取返回给ICMP原始套接口的每个分组，调用函数gettimeofday来记录分组到达的时间，调用函数proc处理分组消息*/
}


/*函数tv_sub代码*/
//#include "ping.h"
void tv_sub(struct timeval *out,struct timeval *in)
{
	if((out->tv_usec-=in->tv_usec)<0)
	{
		--out->tv_usec;
		out->tv_usec+=10000;
	}
	out->tv_usec-=in->tv_usec;
}


/*函数proc代码*/
//#include "ping.h"
void proc(char *ptr,ssize_t len,struct timeval *tvrecv)
{
	int hlen1,icmplen;
	double rtt;
	struct ip *ip;
	struct icmp *icmp;
	struct timeval *tvsend;
	ip=(struct ip *)ptr;
	hlen1=ip->ip_hl<<2;
	icmp=(struct icmp *)(ptr+hlen1);
	if((icmplen=len-hlen1)<8);
		err_quit("icmplen %d<8",icmplen);
	if(icmp->icmp_type==ICMP_ECHOREPLY)
	{
		if(icmp->icmp_id!=pid)
			return;
		if(icmplen<16)
			err_quit("icmplen %d<16",icmplen);
			/*对接收到的ICMP信息进行检查，看是否是发送请求的应答 */
		tvsend=(struct timeval *)icmp->icmp_data;
		tv_sub(tvrecv,tvsend);
		rtt=tvrecv->tv_sec *1000.0+tvrecv->tv_usec/1000.0;
		printf("%d bytes from %s:seq=%u,ttl=%d,rtt=%.3f ms\n",
			icmplen,sock_ntop_host(sarecv,sizeof(struct sockaddr_in)),
			icmp->icmp_type,icmp->icmp_code);
			/*提取ICMP消息中的内容并显示，计算RTT ,TTR和序列号等*/
	}
	else if(verbose)
	{
		printf("%d bytes from %s:type =%d,code=%d\n",icmplen,
			sock_ntop_host(sarecv,sizeof(struct sockaddr_in)),
			icmp->icmp_type,icmp->icmp_code);
	}
}


/*send函数代码*/
//#include "ping.h"
void send(void)
{
	int len;
	struct icmp *icmp;
	icmp=(struct icmp *)sendbuf;
	icmp->icmp_type=ICMP_ECHO;
	icmp->icmp_code=0;
	icmp->icmp_id=pid;
	icmp->icmp_seq=nsent++;
	gettimeofday((struct timeval *)icmp->icmp_data,NULL);
		/*构造ICMP消息，当前时间为数据部分*/
	len=8+datalen;
	icmp->icmp_cksum=0;
	icmp->icmp_cksum=in_cksum((u_short *)icmp,len);
		/*调用in_cksum计算校验和，in_cksum*/
	sendto(sockfd,sendbuf,len,0,sasend,sizeof(struct sockaddr_in));
}


/*函数in_cksum代码 */
u_short in_cksum(unsigned short *addr,int len)
{
	int nleft=len;
	int sum=0;
	unsigned short *w=addr;
	unsigned short answer=0;
	while(nleft>1)
	{
		sum+=*w++;
		nleft-=2;
	}
	if(nleft==1)
	{
		*(unsigned char* )(&answer)=(unsigned char *)w;
		sum+=answer;
	}
	sum=(sum>>16)+(sum&0xffff);
	sum+=(sum>>16);
	answer= ~sum;
	return(answer);
}