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Re: [lwip-devel] lwip-devel Digest, Vol 117, Issue 5


From: Ivan Delamer
Subject: Re: [lwip-devel] lwip-devel Digest, Vol 117, Issue 5
Date: Thu, 06 Mar 2014 08:42:10 -0700

Rahul: could you post this as a bug in Savannah, so it doesn't get forgotten? Something like "separate netif_flag_up for IPv4/6"...

Thanks!
Ivan


Date: Thu, 6 Mar 2014 09:16:01 +0530
From: Rahul Gundecha <address@hidden>
To: address@hidden
Subject: [lwip-devel] netif_set_up & IPv6
Message-ID:
        <address@hidden>
Content-Type: text/plain; charset="iso-8859-1"

Hi all,

I have query about the function netif_set_up() which brings an interface
up. Here is my understanding about this function.
This 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.
Is there some other way of doing this task which I missing here.

Otherwise 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.

Also I see 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.

Thanks,
Rahul




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