IfList implementation with separate objects

IfList.h

#ifndef __IFLIST_H__
#define __IFLIST_H__

struct NetInterface
{

  NetInterface(_netif *netif) : _netif(netif), _num(-1) {}
  NetInterface(const NetInterface & o) : _netif(o.netif), _num(o._num) {}

  bool isLegacy() const { return _num == 0; }
  IPAddress addr () const { return _ip_from_netif_num(); }
  IPAddress netmask () const { return _netif->netmask; }
  IPAddress gw () const { return _netif->gw; }
  String iface () const { return String(_netif->name[0]) + _netif->name[1]; }
  const char* hostname () const { return _netif->hostname ? : ""; }
  const char* mac () const { return (const char*)_netif->hwaddr; }
  int number () const { return _netif->num; }
 
  bool operator==(const NetInterface & o) {return equal(o);}
  bool operator!=(const NetInterface & o) {return !equal(o);}

  bool equal (const NetInterface& o) 
  {
    return _netif == o._netif && (!_netif || _num == o._num);
  }


  const ip_addr_t* ip_from_netif_num () const 
  {
#if LWIP_IPV6
    return _num ? &_netif->ip6_addr[_num - 1] : &_netif->ip_addr;
#else
    return &_netif->ip_addr;
#endif
  }


  netif* _netif;
  int _num;
};




class NetInterfaceIterator
{
public:
  const NetInterfaceIterator& operator* () const { return netIface; }
  const NetInterfaceIterator* operator-> () const { return &netIface; }

  bool operator==(const NetInterfaceIterator & o) {return netIface.equal(o.netIface);}
  bool operator!=(const NetInterfaceIterator & o) {return !netIface.equal(o.netIface);}

  NetInterfaceIterator & operator= (const NetInterfaceIterator& o) { _netif = o._netif; _num = o._num; return *this; }

  NetInterfaceIterator operator++(int) 
  {
    NetInterfaceIterator ret = *this;
    ++(*this);
    return ret;
  }

  NetInterfaceIterator & operator++() 
  {
    while (netIface._netif) 
    {
      if (++netIface._num == IF_NUM_ADDRESSES) 
      {
        netIface = NetInterface(netIface._netif->next);
        continue;
      }

      if (!ip_addr_isany(netIface.ip_from_netif_num()))
        break;
    }
    return *this;
  }

private:
  NetInterface netIface;
};


class IfList
{
  using const_iterator = const NetInterfaceIterator;

  const_iterator begin() {return const_iterator(netif_list);}
  const_iterator end()   {return const_iterator(nullptr);}
};

#endif