ping源碼
 

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第八軍團 時間：2004-1-17 21:47:53 
   
記得W.richard stevens的一句話，學習編碼的最好方法即讀懂大量編碼。 
最近比較有空，所以整理一些代碼供大家學習，有些是自己的拙作，希望不要 
見笑，呵呵。 

/* PING.C  
/*  
/* ping source code distribute by cpu || digger.  
/* for unix family only. compil and link success in sco unix.  
/* i think linux no problem too. u can try it.  
/* before read this code, you shoud know about the principle of  
/* tcp/ip, especially icmp protocol, u also should also know some  
/* about BSD socket API, and unix system signal programming.  
/*  
/* cc -o ping ping.c -lsocket, then u will get executable file,  
/* but must act as root when cc it, and then set euid attribute  
/* for this ping, then u can execute it as common user.  
/* because only root can have authority to creat raw socket.  
/*  
/* i love socket, if so do u,  
/* call me, cpu == digger  

# include  
# include  
# include  
# include  
# include  
# include  
# include  
# include  
# include  
# include  

# define ICMP_ECHO 8 /* icmp echo requir */  
# define ICMP_ECHOREPLY 0 /* icmp echo reply */  
# define ICMP_HEADSIZE 8 /* icmp packet header size */  
# define IP_HEADSIZE 20 /* ip packet header size */  

typedef struct tagIpHead /* icmp packet header */  
{  
u_char ip_verlen; /* ip version and ip header lenth*/  
u_char ip_tos; /* ip type of service */  
u_short ip_len; /* ip packet lenghth */  
u_short ip_id; /* ip packet identification */  
u_short ip_fragoff; /* ip packet fragment and offset */  
u_char ip_ttl; /* ip packet time to live */  
u_char ip_proto; /* ip packet protocol type */  
u_short ip_chksum; /* ip packet header checksum */  
u_long ip_src_addr; /* ip source ip adress */  
u_long ip_dst_addr; /* ip destination ip adress */  
} IPHEAD;  

typedef struct tagIcmpHead /* icmp header */  
{  
u_char icmp_type; /* icmp service type */  
/* 8 echo require, 0 echo reply */  
u_char icmp_code; /* icmp header code */  
u_short icmp_chksum; /* icmp header chksum */  
u_short icmp_id; /* icmp packet identification */  
u_short icmp_seq; /* icmp packet sequent */  
u_char icmp_data[1]; /* icmp data, use as pointer */  
} ICMPHEAD;  

u_short ChkSum( u_short * pIcmpData, int iDataLen )  
/* for check sum of icmp header */  
{  
u_short iSum;  
u_short iOddByte;  

iSum = 0;  

while ( iDataLen > 1 ) { /* xor the next unsigned int data */  
iSum ^= *pIcmpData++;  
iDataLen -= 2;  
}  

if ( iDataLen == 1 ) { /* the rest odd byte */  
iOddByte = 0;  
*((u_char *)&iOddByte) = *(u_char *)pIcmpData;  
iSum ^= iOddByte;  
}  

iSum ^= 0xffff; /* xor 0xffff == not it */  
return(iSum);  
}  

long time_now() /* return time passed by */  
/* since 1970.1.1 00:00:00, */  
/* in 1/1000000 second */  
{  
struct timeval now;  
long lPassed;  
gettimeofday(&now, 0);  
lPassed = now.tv_sec * 1000000 + now.tv_usec;  
/* now.tv_sec in second */  
/* now.tv_usec in 1/1000000 second */  
return lPassed;  
}  

char* host; /* destination host */  
char* prog; /* program name */  
extern errno; /* system global parameter */  
long lSendTime; /* each time when send, change it */  
u_short seq; /* the icmp packet seqence */  
int iTimeOut; /* time out parameter */  
int sock, sent, recvd, max, min, total;  
/* sent : icmp packet already sent */  
/* recvd: proper icmp packet received */  
/* max, min: max min round trip time */  
/* total: total round trip time */  
/* store to calculate average */  
u_long lHostIp; /* host ip adress */  
struct sockaddr_in it; /* destination host information */  

int ping();  
void stat();  

main(int argc, char** argv)  
{  
struct hostent* h;  
char buf[200];  
char dst_host[32];  
int i, namelen;  
IPHEAD* pIpHead;  
ICMPHEAD* pIcmpHead;  

if (argc < 2) { /* ping the destination host */  
/* every timeout second */  
/* default timeout is 1 second */  

printf("usage: %s [-timeout] host|IP\n", argv[0]);  
exit(0);  
}  
prog = argv[0];  
host = argc == 2 ? argv[1] : argv[2];  
iTimeOut = argc == 2 ? 1 : atoi(argv[1]);  

/* creat the raw socket for icmp */  

if ((sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)) < 0) {  
perror("socket");  
exit(2);  
}  

/* set destination host information */  

bzero(&it, sizeof(it));  
it.sin_family = AF_INET;  

/* check host format */  

if ( ( lHostIp = inet_addr(host) ) != INADDR_NONE ) {  
/* is available ip adress */  
it.sin_addr.s_addr = lHostIp;  
strcpy( dst_host, host );  
} else if ( h = gethostbyname(host) ) {  
/* is available host name */  
/* from hosts file of local host */  
/* or from DNS */  
bcopy(h->h_addr, &it.sin_addr, h->h_length);  
sprintf( dst_host, "%s (%s)", host,  
inet_ntoa(it.sin_addr) );  
} else {  
/* bad ip adress or host name */  
/* exit */  
fprintf( stderr, "bad IP or host\n" );  
exit(3);  
}  
namelen = sizeof(it);  

printf("\nDigger pinging %s, send %d bytes\n",  
dst_host,  
IP_HEADSIZE + ICMP_HEADSIZE + sizeof(long)  
);  

seq = 0; /* first icmp_seq = 0 */  
sigset(SIGINT, stat); /* when press del or ctrl+c, call stat */  
/* to statistic the result , and then exit */  
sigset(SIGALRM, ping); /* hook ping function to timer */  
alarm(iTimeOut); /* start timer, call ping every timeout */  
/* seconds */  
ping();  
for ( ;; ) { /* waiting for every echo back */  
/* icmp packet and check it */  
register size;  
register u_char ttl;  
register delta;  
register iIpHeadLen;  

/* block to received echo back datagram */  

size = recvfrom(sock, buf, sizeof(buf), 0,  
(struct sockaddr *)&it, &namelen);  
if (size == -1 && errno == EINTR) {  
/* receive error or system call */  
/* interrupted */  
continue;  
}  

/* calculate the round trip time, */  
/* time when receive minus time when send */  

delta = (int)((time_now() - lSendTime)/1000);  

/* get echo back packet and check its ip header */  

pIpHead = (IPHEAD *)buf;  

/* get the ip packet lenth */  
/* if too small, not the icmp echoreply packet */  
/* give it up */  

iIpHeadLen = (int)((pIpHead->ip_verlen & 0x0f) << 2);  
if (size < iIpHeadLen + ICMP_HEADSIZE) {  
continue;  
}  
ttl = pIpHead->ip_ttl; /* time to live param */  

/* get the icmp header information */  
pIcmpHead = (ICMPHEAD *)(buf + iIpHeadLen);  

/* not icmp echo reply packet, give it up */  
if (pIcmpHead->icmp_type != ICMP_ECHOREPLY) {  
continue;  
}  

/* not proper icmp sequent number, give it up */  
if (pIcmpHead->icmp_id != seq || pIcmpHead->icmp_seq != seq) {  
continue;  
}  

/* print out result for each icmp */  
/* echo reply information */  
sprintf( buf, "icmp_seq=%u bytes=%d ttl=%d",  
pIcmpHead->icmp_seq, size, ttl );  
fprintf(stderr, "reply from %s: %s time=%d ms\n",  
host, buf, delta);  

/* calculate some statistic information */  
/* max, min, average round trip time */  
/* received icmp echo reply packet numbers */  
max = MAX(delta, max);  
min = min ? MIN(delta, min) : delta;  
total += delta;  
++ recvd;  

/* for next icmp sequence */  

++ seq;  
}  
}  

ping()  
{  
char buf[200];  
int iPacketSize;  

/* make the icmp header information */  

ICMPHEAD *pIcmpHead = (ICMPHEAD *)buf;  
pIcmpHead->icmp_type = ICMP_ECHO;  
pIcmpHead->icmp_code = 0;  
pIcmpHead->icmp_id = seq;  
pIcmpHead->icmp_seq = seq;  
pIcmpHead->icmp_chksum = 0;  

/* store time information as icmp packet content, 4 bytes */  
/* u may store other information instead */  

*((long *)pIcmpHead->icmp_data) = time_now();  

iPacketSize = ICMP_HEADSIZE + 4; /* icmp packet length */  

/* icmp header check sum */  

pIcmpHead->icmp_chksum = ChkSum((u_short *)pIcmpHead,  
iPacketSize );  

/* remember the time when send for calculate round trip time */  
lSendTime = time_now();  

/* send the icmp packet to des host */  
if ( sendto(sock, buf, iPacketSize, 0, (struct sockaddr *)&it,  
sizeof(it) ) < 0) {  
perror("send failed");  
exit(6);  
}  

/* packet number been sent */  
++sent;  

/* reset the timer hooker to me again */  
alarm(iTimeOut);  
}  

void stat() /* print the statistic information for this time's ping */  
{  
if (sent) {  
printf("\n----- %s ping statistics summerized by Digger-----\n"  
, host );  
printf("%d packets sent, %d packets received, %.2f%% lost\n",  
sent, recvd, (float)(sent-recvd)/(float)sent*100 );  
}  
if (recvd) {  
printf("round_trip min/avg/max: %d/%d/%d ms\n\n",  
min, total/recvd, max );  
}  
exit(0);  
}