netdev - "ADDRCONF(NETDEV_UP): eth0: link is not ready" with IPv6

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Date:	Fri, 29 Jun 2012 02:36:51 +0000
From:	Arvid Brodin <Arvid.Brodin@...n.com>
To:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	Stephen Hemminger <shemminger@...tta.com>
Subject: "ADDRCONF(NETDEV_UP): eth0: link is not ready" with IPv6

Hi,

After 'ip link set eth0 up' on an avr32 board (network driver macb), the device ends up in
operational mode "UNKNOWN":

# ip link
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
    link/ether 00:24:74:00:17:9d brd ff:ff:ff:ff:ff:ff

Unplugging and plugging in the network cable gets the device to mode "UP".

This is a problem for me because I'm trying to use this device as a "slave" device (for a
virtual HSR device*) and I need to be able to decide if the slave device is operational or
not.

Following Stephen's advice here:
http://kerneltrap.org/mailarchive/linux-netdev/2008/9/24/3398834 I checked the macb.c code
and noticed they do not call netif_carrier_off() neither before register_netdev() nor in
dev_open().

I added the call before register_netdev(), which fixed the problem. However, if I then
enable IPv6:

# ip link set eth0 up
ADDRCONF(NETDEV_UP): eth0: link is not ready
eth0: link up (100/Full)
ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready

Any idea what is happening / what I'm doing wrong? (This is not just cosmetic; is some
situations this seems to kill the interface - e.g. ping does not work, down/up does not
help...) Things work fine without IPv6 configured.

*N.B. I'm writing a driver for a network protocol called "High-availability Seamless
Redundancy".

-- 
Arvid Brodin | Consultant (Linux)
XDIN AB | Jan Stenbecks Torg 17 | SE-164 40 Kista | Sweden | xdin.com