Resolve IP address given in hexadecimal format using getnameinfo() - c

Question

I have a simple program in C, which resolves IP addresses into hostnames.
#include <stdio.h> /* stderr, stdout */
#include <netinet/in.h> /* in_addr structure */
#include <strings.h>
#include <arpa/inet.h>
#include <netdb.h>
int main(int argc, char **argv) {
if ( argc == 2) {
struct sockaddr_in sa;
sa.sin_family = AF_INET;
inet_pton(AF_INET, argv[1], &sa.sin_addr);
char node[NI_MAXHOST];
int res = getnameinfo((struct sockaddr*)&sa, sizeof(sa), node, sizeof(node), NULL, 0, 0);
if (res)
{
printf("%s\n", gai_strerror(res));
return 1;
}
printf("%s\n", node);
return 0;
}
}
It works fine (i.e. ./a.out 10.1.1.2) but I need to modify it so that it accepts IP addresses in HEX format.
Is there some function to convert hex IP addresses to decimal?

Answer 1

I haven't tested this but should work.
#include <stdio.h> /* stderr, stdout */
#include <netinet/in.h> /* in_addr structure */
#include <strings.h>
#include <arpa/inet.h>
#include <netdb.h>
int main(int argc, char **argv) {
if ( argc == 2) {
struct sockaddr_in sa;
char a[2048] = {'\0'}; // placeholder not to overflow and initialised.
if( NULL == strchr(argv[1],'.') )
{
unsigned int unit0, uint1, uint2, uint3;
sscanf(argv[1], "%2x%2x%2x%2x", &uint0, &uint1, &uint2, &uint3);
sprintf(a,"%u.%u.%u.%u",uint0, uint1, uint2, uint3);
}
else
strcpy(a.argv[1]);
sa.sin_family = AF_INET;
inet_pton(AF_INET, a, &sa.sin_addr);
char node[NI_MAXHOST];
int res = getnameinfo((struct sockaddr*)&sa, sizeof(sa), node, sizeof(node), NULL, 0, 0);
if (res)
{
printf("%s\n", gai_strerror(res));
return 1;
}
printf("%s\n", node);
return 0;
}
}
Thanks