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

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Message-ID: <4FF313F6.7010600@xdin.com>
Date:	Tue, 3 Jul 2012 15:47:03 +0000
From:	Arvid Brodin <Arvid.Brodin@...n.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	Stephen Hemminger <shemminger@...tta.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>
Subject: Re: "ADDRCONF(NETDEV_UP): eth0: link is not ready" with IPv6

(Added MACB "patch" contact Nicolas Ferre to CC list.)

On 2012-06-29 17:24, Ben Hutchings wrote:
> On Fri, 2012-06-29 at 02:36 +0000, Arvid Brodin wrote:
>> 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().
> 
> It should be called after register_netdev() and before the driver's
> ndo_open implementation returns.

I'm guessing this allows linkwatch to do netif_carrier_on() some time after the dev_open()?

Besides not calling netif_carrier_off() in dev_open(), the Cadence/MACB driver calls
netif_carrier_off() in dev_close(). Is this correct?


How should I handle carrier state for a virtual device? The device should have "carrier"
as long as at least one of the underlying physical interfaces is operational (which I
guess means operational state UP). Would it be correct to watch NETDEV_CHANGE and DOWN/UP
events of the slaves and call netif_carrier_on()/off() on the virtual device depending on
the slaves' states?


> 
>> 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
> 
> This looks normal.

Good, that narrows it down a bit.

> 
>> 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.
> 
> Perhaps some packets sent automatically by IPv6 are triggering a driver
> bug?  Or there is a bug in multicast support, which IPv6 always uses.
> 
> Ben.
> 
>> *N.B. I'm writing a driver for a network protocol called "High-availability Seamless
>> Redundancy".
> 


-- 
Arvid Brodin | Consultant (Linux)
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