[lwip-devel] [bug #37068] netif up/down handling is unclear

[Rahul]

Follow-up Comment #4, bug #37068 (project lwip):

A related issue is about having separate NETIF_FLAG_UP for IPv4 and IPv6.
Below the description of the issue - 

netif_set_up() function is called from DHCP state machine inside lwip, or it
should be called by netif driver while static IP address is configured.
Lets consider a scenario where a device is configured with DHCP, however for
some reasons device do not get DHCP (IPv4) address. Irrespective of the
success/failure with DHCP (IPv4), one wants to configure link local IPv6
address for an interface and start IPv6 traffic.

One can call netif_set_up() while configuring IPv6 address. However as struct
netif is shared by IPv4 and IPv6 both, calling netif_set_up() wrongly assumes
that both IPv4 and IPv6 address have been configured successfully - hence it
starts sending different kinds of IPv4 (Gratuitous ARP, IGMP, SNMP, etc.) and
IPv6 (MLD, RS,etc.) traffic.

How about separating out the "NETIF_FLAG_UP" flag for IPv4 &
IPv6? If either of IPv4 or IPv6 address is successfully configured then only
the traffic pertaining to that address need to be activated.

NETIF_FLAG_UP is checked only in IPv6 specific functions and not used in IPv4
specific functions other than netif_set_down(). Is there any specific reason
behind this.

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