仿ping程序(linux网络编程

/*
* =====================================================================================
*
*       Filename:  ping.c
*
*    Description:
*
*        Version:  1.0
*        Created:  2012年02月25日 23时04分36秒
*       Revision:  none
*       Compiler:  gcc
*
*         Author:  MaZheng (blog.csdn.net/mazheng1989), mazheng19891019@gmail.com
*        Company:  Dalian University Of Technology
*
* =====================================================================================
*/

#include	<stdio.h>
#include	<sys/time.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	<netdb.h>
#include	<setjmp.h>
#include	<errno.h>
#include	<netinet/ip_icmp.h>
#include	<string.h>
#include	<stdlib.h>
#define	PACKET_SIZE 4096			/*  */
#define MAX_WAIT_TIME 5
#define MAX_NO_PACKETS 3

char sendpacket[PACKET_SIZE];
char recvpacket[PACKET_SIZE];
int sockfd,datalen=56;
int nsend=0,nreceived=0;
struct sockaddr_in dest_addr;
pid_t pid;
struct sockaddr_in from;
struct timeval tvrecv;
void statistics(int signo);
unsigned short cal_chksum(unsigned short *addr,int len);
int pack(int pack_no);
void send_packet(void);
void recv_packet(void);
int unpack(char* buf,int len);
void tv_sub(struct timeval *out,struct timeval* in);

void statistics(int signo)
{
printf("\n-----------------PING statistics----------------\n");
printf("%d packet transmitted,%d received,%%%d lost \n",nsend,nreceived,(nsend-nreceived)/nsend*100);
close(sockfd);
exit(1);
}
/*校验和算法*/
unsigned short cal_chksum(unsigned short *addr,int len)
{
int nleft=len;
int sum=0;
unsigned short *w=addr;
unsigned short answer=0;
/*把ICMP报头二进制数据以2字节为单位累加起来*/
while(nleft>1)
{
sum+=*w++;
nleft-=2;
}
/*若ICMP报头为奇数个字节，会剩下最后一个字节。把最后一个字节视为2字节数据的高字节，这个2字节数据的低字节为0，继续累加*/
if(nleft==1)
{
*(unsigned char *)(&answer)=*(unsigned char *)w;
sum+=answer;
}
sum=(sum>>16)+(sum&0xffff);
sum+=(sum>>16);
answer=~sum;
return answer;
}
/*设置ICMP报头*/
int pack(int pack_no)
{
int packsize;
struct icmp *icmpp;
struct timeval *tval;
icmpp=(struct icmp *)sendpacket;
icmpp->icmp_type=ICMP_ECHO;
icmpp->icmp_code=0;
icmpp->icmp_cksum=0;
icmpp->icmp_seq=pack_no;
icmpp->icmp_id=pid;
packsize=8+datalen;
tval=(struct timeval *)icmpp->icmp_data;
gettimeofday(tval,NULL);/*记录发送时间*/
icmpp->icmp_cksum=cal_chksum((unsigned short*)icmpp,packsize);/*校验算法*/
return packsize;
}
/*发送3个ICMP报文*/
void send_packet()
{
int packetsize;
while(nsend<MAX_NO_PACKETS)
{
nsend++;
packetsize=pack(nsend);/*设置ICMP报文*/
if(sendto(sockfd,sendpacket,packetsize,0,(struct sockaddr *)&dest_addr,sizeof(dest_addr))<0)
{
perror("sendto error");
continue;
}
sleep(1);/*每隔一秒发送一个ICMP报文*/
}
}
/*接收所有ICMP报文*/
void recv_packet()
{
int n,fromlen;
extern int errno;

signal(SIGALRM,statistics);
fromlen=sizeof(from);
while(nreceived<10)
{
alarm(MAX_WAIT_TIME);
if((n=recvfrom(sockfd,recvpacket,sizeof(recvpacket),0,(struct sockaddr *)&from,&fromlen))<0)
{
if(errno==EINTR)
{
continue;
}
perror("recvfrom error\n");
continue;
}
gettimeofday(&tvrecv,NULL); /*记录接收时间*/
if(unpack(recvpacket,n)==-1)
continue;
nreceived++;
}
}
/*剥去ICMP报头*/
int unpack(char *buf,int len)
{
int iphdrlen;
struct ip *ipp;
struct icmp *icmpp;
struct timeval *tvsend;
int rtt;
ipp=(struct ip *)buf;
iphdrlen=(ipp->ip_hl)*4;/*求IP报头长度，即IP报头的长度标志乘4*/
icmpp=(struct icmp*)(buf+iphdrlen);/*超过IP报头，指向ICMP报头*/
len-=iphdrlen;/*ICMP报头及ICMP数据报的总长度*/
if(len<8)/*小于ICMP报头长度则不合理*/
{
printf("ICMP packets\'s length is less than 8\n");
return -1;
}
/*确保所接收的是用户所发的ICMP的回应*/
if((icmpp->icmp_type==ICMP_ECHOREPLY)&&(icmpp->icmp_id==pid))
{
tvsend=(struct timeval *)icmpp->icmp_data;
tv_sub(&tvrecv,tvsend); /*接收和发送的时间差*/
rtt=tvrecv.tv_sec*1000+tvrecv.tv_usec/1000;/*以毫秒为单位计算rtt*/
/*显示相关信息*/
printf("%d byte from %s:icmp_seq=%u ttl=%d rtt=%d  ms\n",
len,inet_ntoa(from.sin_addr),icmpp->icmp_seq,ipp->ip_ttl,rtt);
}
else
return -1;
}
void tv_sub(struct timeval *out,struct timeval *in)
{
if((out->tv_usec-=in->tv_usec)<0)
{
out->tv_sec-=1;
out->tv_usec+=1000000;
}
out->tv_sec-=in->tv_sec;
}
int main(int argc,char **argv)
{
struct hostent *host;
struct protoent *protocol;
int size=50*1024;
if(argc<2)
{
printf("usage : %s hostname/IP address \n",argv[0]);
exit(1);
}
if((protocol=getprotobyname("icmp"))==NULL)
{
perror("getprotobyname\n");
exit(1);
}
/*生成使用ICMP的原始套接字，这种套接字只是root才能生成*/
if((sockfd=socket(AF_INET,SOCK_RAW,protocol->p_proto))<0)
{
perror("socket error\n");
exit(1);
}
/*回收root权限，设置当前用户权限*/
setuid(getuid());
/*扩大套接字接收缓冲区到50K，这样做主要为了减少接收缓冲区溢出的可能性，若无意中ping一个广播地址或多播地址，将会引来大量应答*/
setsockopt(sockfd,SOL_SOCKET,SO_RCVBUF,&size,sizeof(size));
bzero(&dest_addr,sizeof(dest_addr));
dest_addr.sin_family=AF_INET;
if((host=gethostbyname(argv[1]))==NULL)
{
perror("gethostbyname error\n");
exit(1);
}
dest_addr.sin_addr=*((struct in_addr *)host->h_addr);
pid=getpid();
printf("PING %s(%s): %d bytes data in ICMP packets.\n",argv[1],inet_ntoa(dest_addr.sin_addr),datalen);
send_packet();/*发送所有ICMP报文*/
recv_packet();/*接收所有ICMP报文*/
statistics(SIGALRM);/*进行统计*/

return 0;
}

编译：$:gcc -o ping ping.c

授权: $: sudo chown root ping

$:sudo chown u+s ping

运行： $./ping target（target为目标地址