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subnetting.c
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subnetting.c
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#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdbool.h>
enum NetworkClass {CLASS_A, CLASS_B, CLASS_C};
// This section of code consitutes a more Java-like version of finding a preix
// A C programmer is more likely to simply do the binary math.
const unsigned int prefix_map[9] = {0, 128, 192, 224, 240, 248, 252, 254, 255};
const int usable_hosts_map[9] = {254, 126, 62, 30, 14, 6, 2, 0, 0};
const int subnet_multiplyer[4] = {0, 8, 16, 24};
unsigned int* subnet_to_octet_array(unsigned int octets[4], char subnet_mask[16]){
sscanf(subnet_mask, "%u.%u.%u.%u", &octets[0], &octets[1], &octets[2], &octets[3]);
return octets;
}
int mask_to_prefix(char mask[16]){
unsigned int octet[4];
int pref = 0;
subnet_to_octet_array(octet, mask);
for (int i = 0; i < 4; ++i){
for (int j = 0; j < 9; ++j){
if (octet[i] == prefix_map[j]){
pref += j;
break;
}
}
}
return pref;
}
char* prefix_to_mask(char subnet_mask[16], unsigned int prefix){
unsigned int octets[5];
for (int i = 0; i < 5; ++i){
for (int j = 8; j >= 0; --j){
if (prefix >= j){
prefix -= j;
octets[i] = prefix_map[j];
break;
}
}
}
sprintf(subnet_mask, "%u.%u.%u.%u", octets[0], octets[1], octets[2], octets[3]);
return subnet_mask;
}
int hosts_for_prefix(int prefix){
return (int)pow(2.0, (double)(32-prefix));
}
int subnets_for_prefix(int prefix){
return (int)pow(2.0, (double)(prefix%8));
}
void ui_to_octets(char addr[16], unsigned int subnet_mask){
int octets[4];
octets[0] = (subnet_mask >> 24) & 0xFF;
octets[1] = (subnet_mask >> 16) & 0xFF;
octets[2] = (subnet_mask >> 8) & 0xFF;
octets[3] = subnet_mask & 0xFF;
sprintf(addr, "%d.%d.%d.%d", octets[0], octets[1], octets[2], octets[3]);
}
int prefix_for_hosts(int hosts_required){
for (int i = 32; i >= 0; --i){
if (hosts_for_prefix(i)-2 >= hosts_required){
return i;
}
}
return -1;
}
char* octet_array_to_string(char subnet_mask[16], char octets[4]){
sprintf(subnet_mask, "%d.%d.%d.%d", octets[0], octets[1], octets[2], octets[3]);
return subnet_mask;
}
int network_type_based_on_subnet(int subnet_arr[4]){
if (subnet_arr[0] != 255){
return -1;
} else if (subnet_arr[1] != 255){
return CLASS_A;
} else if (subnet_arr[2] != 255){
return CLASS_B;
} else if (subnet_arr[3] != 255){
return CLASS_C;
} else {
return -1;
}
}
char network_class(int subnet_arr[4]){
if (subnet_arr[0] != 255){
return '?';
} else if (subnet_arr[1] != 255){
return 'A';
} else if (subnet_arr[2] != 255){
return 'B';
} else if (subnet_arr[3] != 255){
return 'C';
} else {
return '?';
}
}
unsigned int octets_to_ui(char octets[16]){
int so_s[4];
unsigned int rv;
sscanf(octets, "%d.%d.%d.%d", &so_s[0], &so_s[1], &so_s[2], &so_s[3]);
rv = (so_s[0] << 24) | (so_s[1] << 16) | (so_s[2] << 8) | (so_s[3]);
return rv;
}
unsigned int bdr_addr(unsigned int ip, unsigned int subnet){
return ip | ~subnet;
}
unsigned int net_addr(unsigned int ip, unsigned int subnet){
return ip & subnet;
}
char* network_address(char result[16], char ip[16], char subnet[16]){
unsigned int num = octets_to_ui(ip) & octets_to_ui(subnet);
ui_to_octets(result, num);
return result;
}
char* broadcast_address(char result[16], char ip[16], char subnet[16]){
unsigned int bdr_add = octets_to_ui(ip) | ~octets_to_ui(subnet);
ui_to_octets(result, bdr_add);
return result;
}
char* usable_host_addresses(char result[33], char ip[16], char subnet[16]){
char slow_addrs[16];
char shigh_addrs[16];
unsigned int low_addr = net_addr(octets_to_ui(ip), octets_to_ui(subnet));
unsigned int high_addr = bdr_addr(octets_to_ui(ip), octets_to_ui(subnet));
++low_addr;
--high_addr;
ui_to_octets(slow_addrs, low_addr);
ui_to_octets(shigh_addrs, high_addr);
sprintf(result, "%s-%s", slow_addrs, shigh_addrs);
return result;
}
int get_ui_class(unsigned int ip){
unsigned int fo = ip >> 24;
if (fo >= 1 && fo <= 126){
return CLASS_A;
} else if (fo >= 128 && fo <= 191){
return CLASS_B;
} else if (fo >= 192 && fo <= 223){
return CLASS_C;
}
return -1;
}
int main(){
char* mask1 = {"255.255.255.192"};
char mask2[16];
int prefix, hosts, networks;
unsigned int octets[4];
prefix = mask_to_prefix(mask1);
fprintf(stdout, "Prefix of %s is %d\n", mask1, prefix);
prefix_to_mask(mask2, prefix);
fprintf(stdout, "Subnet of %d is %s\n", prefix, mask2);
hosts = hosts_for_prefix(prefix);
printf("It can support up to %d hosts.\n", hosts);
networks = subnets_for_prefix(prefix);
printf("It can support ip to %d subnets.\n", networks);
subnet_to_octet_array(octets, mask1);
for (int i = 0; i < 4; ++i){
printf("\tPt %d: %d\n", i+1, octets[i]);
}
int prefix64,prefix2000;
char subnet64[16];
char subnet2000[16];
int subarr64[4];
int subarr2000[4];
prefix64 = prefix_for_hosts(64);
prefix2000 = prefix_for_hosts(2000);
prefix_to_mask(subnet64, prefix64);
prefix_to_mask(subnet2000, prefix2000);
subnet_to_octet_array(subarr64, subnet64);
subnet_to_octet_array(subarr2000, subnet2000);
printf("64 hosts requires a prefix of %d (%s).\n", prefix64, subnet64);
printf("2000 hosts requires a prefix of %d (%s).\n", prefix2000, subnet2000);
printf("A prefix of %d can support %d hosts.\n", prefix2000, hosts_for_prefix(prefix2000));
printf("%s indicates a class %c network.\n", subnet64, network_class(subarr64));
printf("%s indicates a class %c network.\n", subnet2000, network_class(subarr2000));
char* ip1 = {"192.168.16.122"};
char* sub1_ip1 = { "255.255.255.240" };
char na_ip1[16];
char ba_ip1[16];
char ra_ip1[33];
network_address(na_ip1, ip1, sub1_ip1);
broadcast_address(ba_ip1, ip1, sub1_ip1);
usable_host_addresses(ra_ip1, ip1, sub1_ip1);
printf("%s (%s)'s network address is %s.\n", ip1, sub1_ip1, na_ip1);
printf("%s (%s)'s broadcast address is %s.\n", ip1, sub1_ip1, ba_ip1);
printf("The host range is %s\n", ra_ip1);
char* ip2 = {"172.17.130.222"};
char* sub2_ip2 = { "255.255.128.0" };
char na_ip2[16];
network_address(na_ip2, ip2, sub2_ip2);
printf("%s (%s)'s network address is %s.\n", ip2, sub2_ip2, na_ip2);
// actual program
char* print_format = {"%18s | %33s | %18s | %16s | /%2d\n"};
int num_of_networks;
int hosts_per_network;
char file_location[255];
FILE* print_file;
printf("Where would you like to save these tables? ");
scanf("%s", file_location);
print_file = fopen(file_location, "w");
fprintf(print_file, "---------------------------------------------------------------------------------------------------------------------\n");
printf("How many networks do you need? ");
scanf("%d", &num_of_networks);
char ip[16];
unsigned int ui_ip;
printf("Enter a base IP address to start configuring. (Usually 192.168.x.0, 172.17.x.0, etc...)\nBase IP: ");
scanf("%s", ip);
ui_ip = octets_to_ui(ip);
fprintf(print_file, print_format, "Network Address", "Host Range", "Broadcast Address", "Subnet Mask", 0);
for (int i = 0; i < num_of_networks; ++i){
int hosts;
char subnt_s[16];
char broadcast_addr[16];
char network_addr[16];
char usable_range[33];
unsigned int subnt;
int this_prefix;
printf("How many hosts do you need on this network [%d]? ", i);
scanf("%d", &hosts);
this_prefix = prefix_for_hosts(hosts);
prefix_to_mask(subnt_s, this_prefix);
subnt = octets_to_ui(subnt_s);
broadcast_address(broadcast_addr, ip, subnt_s);
network_address(network_addr, ip, subnt_s);
usable_host_addresses(usable_range, ip, subnt_s);
fprintf(print_file, print_format, network_addr, usable_range, broadcast_addr, subnt_s, this_prefix);
ui_ip = octets_to_ui(broadcast_addr) + 1;
ui_to_octets(ip, ui_ip);
}
return 0;
}