东大某位同学ping代码，还不错

转自百度文库。

#include <stdio.h>

#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.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>


#define PACKET_SIZE 4096
#define MAX_WAIT_TIME 3


char sendpacket[PACKET_SIZE];
char recvpacket[PACKET_SIZE];
int sockfd, datalen = 56;
int nsend = 0, nreceived = 0;
struct sockaddr_in dest_addr;
struct protoent *protocol;
pid_t pid;
struct sockaddr_in from;
struct timeval tvrecv;
double min_rtt = MAX_WAIT_TIME, max_rtt = 0.0, sum_rtt = 0.0;


void statistics( int signo );
void timeout( 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 );


int main( int argc, char *argv[] )
{
struct hostent *host;
unsigned long inaddr = 0l;
int size = 50 * 1024;
int destLocation = 1;//目的地参数所在位置
int sendCount = 0;//发送数据包个数


if( argc < 2 )
{
printf( "Usage:%s destination\n", argv[0] );
exit( 1 );
}
else
{
int AC = 1; //参数计数器
while( AC < argc )
{
if( argv[AC][0] == '-' )//有选项参数
{
if( argv[AC][1] == 'c' )//指定发送包个数
{
if( strlen(argv[AC]) == 2 )
{
AC++;
sendCount = atoi(argv[AC]);
}
else
sendCount = atoi(&argv[AC][2]);
}
else if( argv[AC][1] == 's' )//指定发送包数据大小
{
if( strlen(argv[AC]) == 2 )
{
AC++;
datalen = atoi(argv[AC]);
}
else
datalen = atoi(&argv[AC][2]);
}
}
else //是目的地参数
destLocation = AC;
AC++;
}
}


if( (protocol = getprotobyname( "icmp" )) == NULL ) //获得协议信息
{
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。这样做主要为了减小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;
//判断是主机名还是IP地址
if( (inaddr = inet_addr( argv[destLocation] )) == INADDR_NONE ) 
{ //不是点分十进制
if( (host = gethostbyname( argv[destLocation] )) == NULL )
{
perror( "gethostbyname error" );
exit( 1 );
} //是主机名
memcpy( (char *)&dest_addr.sin_addr, host->h_addr, host->h_length );
}
else //是IP地址
memcpy( (char *)&dest_addr.sin_addr, (char *)&inaddr, sizeof(inaddr) );


//获取main的进程id,用于设置ICMP的标志符
pid = getpid();
printf( "PING %s(%s): %d bytes of data in ICMP packets.\n", argv[destLocation],
inet_ntoa( dest_addr.sin_addr ), datalen );


signal( SIGINT, statistics );//若从键盘中断则直接进行统计输出


while( 1 )
{
send_packet();
recv_packet();
sleep( 1 ); //每隔一秒发送一个ICMP报文


if( sendCount == 0 )
continue;
else if( nsend == sendCount )
break;
}


statistics( SIGTERM );//正常结束进行统计输出


return 0;
}


//进行统计
void statistics( int signo )
{
close( sockfd );//在统计时关闭sockfd
printf( "\n--------------------PING statistics-------------------\n" );
printf( "%d packets transmitted, %d received , %.0f%% packet loss\n",
nsend, nreceived, (nsend - nreceived) / (double)nsend * 100.0 );
if( min_rtt < MAX_WAIT_TIME)//没有ping通，以下不会显示
{
printf( "rtt min/avg/max = %.3f/%.3f/%.3f ms\n", min_rtt,
sum_rtt / nreceived, max_rtt );
}
exit( 1 );
}


//超时处理
void timeout( int signo )
{
printf( "Request timed out.\n" );
}


//计算校验和
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，会剩下最后一字节。
//把最后一个字节视为一个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 *icmp;
struct timeval *tval;
icmp = (struct icmp*)sendpacket;
icmp->icmp_type = ICMP_ECHO;//ICMP报文类型
icmp->icmp_code = 0;//编码（未使用）
icmp->icmp_cksum = 0;//初始化校验和
icmp->icmp_seq = pack_no;//发送序列号
icmp->icmp_id = pid;//唯一标识ICMP报文
packsize = 8 + datalen;//ICMP报文头部共8字节
tval = (struct timeval *)icmp->icmp_data;
gettimeofday( tval, NULL ); //记录发送时间
icmp->icmp_cksum = cal_chksum( (unsigned short *)icmp, packsize );//校验和
return packsize;
}


//发送一条ICMP报文
void send_packet()
{
int packetsize;


packetsize = pack( nsend + 1 );//设置ICMP报头
if( sendto( sockfd, sendpacket, packetsize, 0,
(struct sockaddr *)&dest_addr, sizeof(dest_addr) ) < 0 )
{
perror( "sendto error" );
return;
}
nsend++;
}


//接收一条ICMP报文
void recv_packet()
{
int n, fromlen;
extern int errno;


signal( SIGALRM, timeout );//等待MAX_WAIT_TIME无响应则直接进入超时处理
alarm( MAX_WAIT_TIME );//设置最长等待时间
do
{
if( (n = recvfrom( sockfd, recvpacket, sizeof(recvpacket), 0,
(struct sockaddr *)&from, &fromlen )) < 0 )
{
if( errno == EINTR )//被信号中断
return;
perror( "recvfrom error" );
return;
}
gettimeofday( &tvrecv, NULL );//记录接收时间
} //收到前面超时或非ECHOREPLY的报文则再取下一条报文
while( unpack( recvpacket, n ) == 1 );
alarm( MAX_WAIT_TIME );//设置最长等待时间
}


//剥去ICMP报头并处理ICMP信息
int unpack( char *buf, int len )
{
int iphdrlen;
struct ip *ip;
struct icmp *icmp;
struct timeval *tvsend;
double rtt;


ip = (struct ip *)buf;
iphdrlen = ip->ip_hl << 2;//求ip报头长度,即ip报头的长度标志乘以4
icmp = (struct icmp *)(buf + iphdrlen);//越过ip报头,指向ICMP报头
if( ip->ip_p == protocol->p_proto && icmp->icmp_seq == nsend && 
icmp->icmp_type == ICMP_ECHOREPLY )
{
len -= iphdrlen;//ICMP报文的总长度
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;
}
//确保所接收的是本程序所发的的ICMP的回应
if( icmp->icmp_id == pid )
{
nreceived++; //收到正确的报文
tvsend = (struct timeval *)icmp->icmp_data;
tv_sub( &tvrecv, tvsend );//计算接收和发送的时间差
rtt = tvrecv.tv_sec * (double)1000 + tvrecv.tv_usec / (double)1000;
printf( "%d bytes from %s: icmp_seq=%u ttl=%d time=%.3f ms\n", len,
inet_ntoa( from.sin_addr ), icmp->icmp_seq, ip->ip_ttl, rtt );
if( rtt < min_rtt )
min_rtt = rtt;
if( rtt > max_rtt )
max_rtt = rtt;
sum_rtt += rtt;
return 0;
}
else
return -1;
}
else //收到非ICMP报文或前面超时的报文则不再处理
return 1;
}


//计算时间差
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;
}