根据传入的ip地址，从arp表中查找mac地址并返回

//根据传入的ip地址，从arp表中查找mac地址并返回
char *arp_get(const char *req_ip)
{
    FILE           *proc;
	 char ip[16];
	 char mac[18];
	 char * reply = NULL;

    if (!(proc = fopen("/proc/net/arp", "r"))) {
        return NULL;
    }

    /* Skip first line */
	 while (!feof(proc) && fgetc(proc) != '\n');

	 /* Find ip, copy mac in reply */
	 reply = NULL;
    while (!feof(proc) && (fscanf(proc, " %15[0-9.] %*s %*s %17[A-Fa-f0-9:] %*s %*s", ip, mac) == 2)) {
		  if (strcmp(ip, req_ip) == 0) {
				reply = safe_strdup(mac);
				break;
		  }
    }

    fclose(proc);

    return reply;
}