[lwip-devel] LWIP_NSC_IPV4_GATEWAY/NETMASK/SETTINGS_CHANGED should check if the setting is actually being changed

[Axel Lin]

Currently seems only LWIP_NSC_IPV4_ADDRESS_CHANGED check if the
setting is actually being changed.

When enable LWIP_NETIF_EXT_STATUS_CALLBACK:
I got below event everytime when dhcp server re-assigned ip address even the
gateway/netmask/ip are exactly the same with previous setting.

LWIP_NSC_IPV4_GATEWAY_CHANGED
LWIP_NSC_IPV4_NETMASK_CHANGED
LWIP_NSC_IPV4_SETTINGS_CHANGED

I'm wondering if these callbacks should be called only when the
setting is actually being changed.