Reverse resolve

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netdb.h>

static char name[32];

int main(int argc, char **argv)
{
        int error;
        char *ip = argv[1];

        struct sockaddr_in sa;

        if (argc <= 1) {
                fprintf(stderr, "usage: %s <ip address>\n", argv[0]);
                exit(EXIT_FAILURE);
        }

        memset(&sa, 0, sizeof(sa));
        sa.sin_family = AF_INET;
        error = inet_aton(ip, &sa.sin_addr);
        if (error == 0) {
                perror("inet_aton()");
                exit(EXIT_FAILURE);
        }

        error = getnameinfo((struct sockaddr *)&sa, sizeof(sa), name, sizeof(name), NULL, 0, NI_NAMEREQD);
        if (error) {
                perror("getnameinfo()");
                exit(EXIT_FAILURE);
        }
        puts(name);
        return 0;

}