ip_test.c

IP地址及子网的合法性 使有方法: 程序名 subnet/mask ip_addr 说明:subnet/mask:如211.168.2.0/27 ip_addr: 如211.168.2.3

#include <stdio.h>
#include <math.h>

int IpFt;		//the first byte of the subnet's ip


int IsLegal(char * const s){
	char *p = s, c;
	int err = 0, dot = 1, i = 3;
	while((c = *p++) && !err) {
		if (c == '.') {
			if (dot) {
				err++;
				break;
			}
			//ipaddr->uip.part[i] = part;
			dot++, i--;
		} else if (isdigit(c))
			dot = 0;
	              else err++;
	}
	if (i || *(--p, --p) == '.')
		err++;
	return !err;
}

int Ip_addr_test(char *addr, long int *ip) //test IP  whether it is legal or not
{ 
	int i, num = 0; 	// num:the number of the char '.'
	char *p = addr;

	if(IsLegal(addr)){  
		int j, k = 3;
		while(p != NULL) {
			j = atoi(p); 
			if(j <= 255 && j >= 0){  // ip address <= 255 and >= 0
			   if(*ip == 0)
				IpFt = j;
			   *ip = *ip + j * (1 << (k*8));			   
			 //  printf("ip: %d.", *ip);		
			} 
			else 	return -2;	 
			p = strchr(p, '.');
			if( p != NULL)
				p++;
			k--;
		}	
		return 0;	
	}else
		return -1;
}

int Subnet_test(char* subnet, long int* l_subnet, int* i_mask){
	int i, flag = 0, ipflag = 0;
	char * p = subnet;

	for(i = 0; i < strlen(subnet); i++){
		if(subnet[i] == '/')
			flag++;
		else if(subnet[i] != '.' && (subnet[i] < '0' || subnet[i] > '9' ))
			return  -1;
	}
	if(flag == 1){
		p = strchr( p, '/' );
		*p = '\0';
		p++;
		*i_mask = atoi(p);		
		if(Ip_addr_test(subnet, l_subnet))         
			return -1;
	}else if(flag == 0)
			return -2;
		else 
		 	return -1;
	return 0;
}
			
int Ip_Addr_Type(){//A type return 1, b type return 2, c type return 3

	if(IpFt >= 1 && IpFt <= 126)
		return 1;	
	else if(IpFt >= 127 && IpFt <= 191)
		return 2;
	     else if(IpFt >= 192 && IpFt <= 223)
		return 3;
		else 
		   return 4;
}

int TestMask(long int sn, int m, int *mflag, int *snflag){ /* return -1:ip address type is D, E 
			  mflag signs which mask is legal; sn sings which subnet is legal */
	int HIpNum = 32 - m;
	long int n;
	
	//printf(" ipft= %d\n type = %d\n",IpFt, Ip_Addr_Type()); 
	switch(Ip_Addr_Type()){
		case 1: 
			if(m < 8 || m > 32) 
				*mflag = 1;
			break;
		case 2:
			if(m < 16 || m > 32) 
				*mflag = 1;
			break;
		case 3:
			if(m < 24 || m > 32) 
				*mflag = 1;
			break;
		defalut:
			printf("D. E type IP address!!\n");
			return -1; 
	}
	if(*mflag == 0){
		n = (1 << (32 - m )) - 1;
		//printf("m = %d, n = %08x\n", m , sn);
		if((sn & n) != 0)
			*snflag = 1;
	}
	//printf("mflag = %d, snflag = %d\n", *mflag, *snflag);
	return 0;		
}

int Is_subnet(long int ip, long int sn, int m)
{
	int HostIpNum;
	long int n = -1;

	HostIpNum = 32  - m;
	n = (n << HostIpNum) & ip; 
	if(n  == sn)
	 	return 1;
	else 
		return 0;
}

int main(int argc, char **argv){
	long int l_ip = 0, l_subnet = 0;
	int i_mask;
	int mflag = 0, snflag = 0, flag; // mflag is mask 's check flag;  snflag is subnet's check flag

	if(argc <=  2){
		printf("Error:para is too few!\n");
		return -1;
	}
	flag = Ip_addr_test(argv[2], &l_ip); // test ip 

	/* < -- test ip --> */
	if(flag == -1){
		printf("IP adress ERROR: IP includes too much dot or doesn't only include digits\n");
		return -1;
	}else if(flag == -2){
		printf("IP adress ERROR:the ip adress > 255 or < 0!!\n");
		return -1;
	}else
		printf("the ip adress is right!!\n");

	  
	/* < -- test subnet and mask --> */  	
	if((flag = Subnet_test(argv[1], &l_subnet, &i_mask)) == -1){  //detach and test subnet
		printf("SUBNET ERROR: IP includes too much dot or doesn't only include digits!\n");
		return -1;
	} else if(flag == -2){
		printf("SUBNET ERROR:lack of mask\n");
		return -1;
	}
	if(! TestMask(l_subnet, i_mask, &mflag, &snflag)){ // test Mask code
	     if(mflag == 1){
			printf("MASK ERROR:mask is wrong!\n");
			return -1;
		}
	     if(snflag == 1){
			printf("SUBNET ERROR:the subnet doesn't exist!!\n");
			return -1;
		}
	     printf("subnet is legal!!\n");
	}	

	/* ip belongs to subnet */
	if(Is_subnet(l_ip, l_subnet, i_mask))            
		printf("\n%s  belongs to %s/%d\n", argv[2], argv[1], i_mask);
	else 
		printf("\n%s doesn't belog to %s/%d\n", argv[2], argv[1], i_mask);
	return 0;
}