Reputation: 52
I am writing a tool to scan all the nodes on a network but I have ran in to a problem. I'm writing the tool in C but I'm new to the language so I'm not sure how the iterate through the address range.
The user will give the argument 192.168.*.* and it will create every IP address in that range, e.g. 192.168.1.1, 192.168.1.2, 192.168.1.3 and then eventually 192.168.2.1, 192.168.2.2, 192.168.2.3 etc.
My previous code was:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void scanner(int s)
{
char addr[20];
for (int i = 0; i < 255; ++i)
{
sprintf(addr, "192.168.%d.%d", s, i);
printf("%s\n", addr);
}
}
int main()
{
for (int i = 0; i < 255; ++i)
{
scanner(i);
}
return 0;
}
But I don't know how to run this from the user input.
Upvotes: 0
Views: 733
Reputation: 1158
Inspired by (e.g. python-) generators, my solution doesn't perform dynamic memory allocation and and has constant memory consumption. I don't like that I currently rely on a do while
loop. Also the explicit check for ig->num_wildcards == 0
is ugly. Anyways:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define IP_OCTETS 4
#define MAX_UCHAR 255
typedef struct {
int wildcard_pos[IP_OCTETS];
int num_wildcards;
int counter[IP_OCTETS];
int octet[IP_OCTETS];
} ip_generator;
char* mystrsep(char** stringp, const char* delim)
{
char* start = *stringp;
char* p;
p = (start != NULL) ? strpbrk(start, delim) : NULL;
if (p == NULL)
{
*stringp = NULL;
}
else
{
*p = '\0';
*stringp = p + 1;
}
return start;
}
void init_ip_gen(ip_generator *ig, char* ip_mask)
{
char *token, *string;
char* ip_mask_ptr = ip_mask;
const char delimiters[] = ".";
int i = 0;
while ((token = mystrsep(&ip_mask_ptr, delimiters)) != NULL)
{
ig->wildcard_pos[i] = -1;
if (strcmp(token, "*") == 0)
{
ig->wildcard_pos[ig->num_wildcards] = i;
ig->counter[ig->num_wildcards] = 1;
ig->num_wildcards++;
}
else
{
ig->octet[i] = atoi(token);
}
i++;
}
}
int ig_next(ip_generator *ig)
{
int i;
int carry = 1;
if (ig->num_wildcards == 0)
{
return 0;
}
for (i = ig->num_wildcards - 1; i >= 0; i--)
{
if (carry == 1)
{
if (ig->counter[i] == MAX_UCHAR)
{
ig->counter[i] = 1;
}
else
{
ig->counter[i]++;
carry = 0;
}
}
if (carry == 0)
{
break;
}
if (i == 0 && carry == 1)
{
return 0;
}
}
return 1;
}
void generate_ip(ip_generator *ig, char *ip)
{
int i;
int j = 0;
int oct[IP_OCTETS];
for (i = 0; i < IP_OCTETS; i++)
{
if (i == ig->wildcard_pos[j])
{
oct[i] = ig->counter[j];
j++;
}
else
{
oct[i] = ig->octet[i];
}
}
sprintf(ip, "%d.%d.%d.%d", oct[0], oct[1], oct[2], oct[3]);
}
int main()
{
char ip_mask[] = "192.*.10.*";
//char ip_mask[] = "192.1.10.123";
ip_generator ig;
memset(&ig, 0, sizeof(ig));
init_ip_gen(&ig, ip_mask);
char ip[32];
memset(ip, 0, sizeof(ip));
do
{
generate_ip(&ig, ip);
printf("%s\n", ip);
} while (ig_next(&ig));
return 0;
}
Upvotes: 0
Reputation: 381
You can take the inputs from the user using the scanf function. I have updated your code to use the same -
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int addr_byte_0;
int addr_byte_1;
void scanner(int s)
{
char addr[200];
int i;
for (i = 0; i < 255; ++i)
{
sprintf(addr, "%d.%d.%d.%d", addr_byte_0, addr_byte_1, s, i);
printf("%s\n", addr);
}
}
int main()
{
int i;
//printf("Enter the first byte of the address: ");
scanf ("%d", &addr_byte_0);
//printf("Enter the second byte of the address: ");
scanf ("%d", &addr_byte_1);
for (i = 0; i < 255; ++i)
{
scanner(i);
}
return 0;
}
Also, as per C standards you cannot declare a variable inside the for loop. Hence I have moved the declaration out of the for loop. Hope this helps!
Upvotes: 1