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Re: [PATCH v2 net-next] sky2: use random address if EEPROM is bad

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On Wed, Aug 12, 2015 at 04:28:23PM +0100, Stephen Hemminger wrote:
> On Wed, 12 Aug 2015 10:30:05 +0100
> Liviu Dudau <Liviu.Dudau@arm.com> wrote:
> 
> > On Tue, Aug 11, 2015 at 06:01:32PM +0100, Stephen Hemminger wrote:
> > > On Tue, 11 Aug 2015 15:35:56 +0100
> > > Liviu Dudau <Liviu.Dudau@arm.com> wrote:
> > > 
> > > > On some embedded systems the EEPROM does not contain a valid MAC address.
> > > > In that case it is better to fallback to a generated mac address and
> > > > let init scripts fix the value later.
> > > > 
> > > > Reported-by: Liviu Dudau <Liviu.Dudau@arm.com>
> > > > Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> > > > [Changed handcoded setup to use eth_hw_addr_random() instead]
> > > > Signed-off-by: Liviu Dudau <Liviu.Dudau@arm.com>
> > > > ---
> > > > I have tested this on my Juno platform and I can successfully do an nfsroot boot.
> > > > 
> > > > Best regards,
> > > > Liviu
> > > > 
> > > >  drivers/net/ethernet/marvell/sky2.c | 7 +++++++
> > > >  1 file changed, 7 insertions(+)
> > > > 
> > > > diff --git a/drivers/net/ethernet/marvell/sky2.c b/drivers/net/ethernet/marvell/sky2.c
> > > > index d9f4498..c309879 100644
> > > > --- a/drivers/net/ethernet/marvell/sky2.c
> > > > +++ b/drivers/net/ethernet/marvell/sky2.c
> > > > @@ -4819,6 +4819,13 @@ static struct net_device *sky2_init_netdev(struct sky2_hw *hw, unsigned port,
> > > >  		memcpy_fromio(dev->dev_addr, hw->regs + B2_MAC_1 + port * 8,
> > > >  			      ETH_ALEN);
> > > >  
> > > > +	/* if the address is invalid, use a random value */
> > > > +	if (!is_valid_ether_addr(dev->dev_addr)) {
> > > > +		netdev_warn(dev,
> > > > +			"Invalid MAC address, defaulting to random\n");
> > > > +		eth_hw_addr_random(dev);
> > > > +	}
> > > > +
> > > >  	return dev;
> > > >  }
> > > >  
> > > 
> > > This is not enough, you need to program the hardware with the new random MAC
> > > address. The easiest way is calling sky2_set_mac_address, but you need to convert
> > > the address from array back to sockaddr.
> > > 
> > 
> > OK, I am a bit confused as to why sky2_set_mac_address is needed here, as this was not
> > required by the existing function. Given that in my tests I get a random MAC address
> > assigned every time to the device and I can see the same MAC address with ifconfig, how
> > can I test the effect of sky2_set_mac_address if I add it?
> 
> The network device address is stored in two places. One is in the
> kernel (dev->dev_addr) and is  used by networking stack.
> The other is the hardware (actually two places) and is used filtering received packets
> in the PHY and for sending hardware generated pause frames.
> 
> When a random address is generated, you need to tell the hardware
> to use that address as well. I suspect your hardware maybe limited in functionality
> and not do the normal filtering.
> 

I understand now, thanks for explaining it. I admit my tests were very limited and I did not
try to capture any packets using the interface. I thought the DHCP discovery requires the
MAC address to be correct in the hardware to work, but it might be that the kernel's DHCP
client is more thorough than userspace.

I will add the setting of the MAC address in v3.

Best regards,
Liviu

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
    ¯\_(ツ)_/¯

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Thread

[PATCH] sky2: Add module parameter for passing the MAC address Liviu Dudau <Liviu.Dudau@arm.com> - 2015-08-05 18:00 +0200
  Re: [PATCH] sky2: Add module parameter for passing the MAC address Stephen Hemminger <stephen@networkplumber.org> - 2015-08-05 18:50 +0200
    Re: [PATCH] sky2: Add module parameter for passing the MAC address Liviu Dudau <Liviu.Dudau@arm.com> - 2015-08-05 19:20 +0200
      Re: [PATCH] sky2: Add module parameter for passing the MAC address Francois Romieu <romieu@fr.zoreil.com> - 2015-08-05 22:40 +0200
        Re: [PATCH] sky2: Add module parameter for passing the MAC address Stephen Hemminger <stephen@networkplumber.org> - 2015-08-06 01:20 +0200
          Re: [PATCH] sky2: Add module parameter for passing the MAC address Florian Fainelli <f.fainelli@gmail.com> - 2015-08-06 02:40 +0200
            [PATCH v2 net-next] sky2: use random address if EEPROM is bad Liviu Dudau <Liviu.Dudau@arm.com> - 2015-08-11 16:40 +0200
              Re: [PATCH v2 net-next] sky2: use random address if EEPROM is bad Stephen Hemminger <stephen@networkplumber.org> - 2015-08-11 19:10 +0200
                Re: [PATCH v2 net-next] sky2: use random address if EEPROM is bad Liviu Dudau <Liviu.Dudau@arm.com> - 2015-08-12 11:40 +0200
                Re: [PATCH v2 net-next] sky2: use random address if EEPROM is bad Stephen Hemminger <stephen@networkplumber.org> - 2015-08-12 17:30 +0200
                Re: [PATCH v2 net-next] sky2: use random address if EEPROM is bad Liviu Dudau <Liviu.Dudau@arm.com> - 2015-08-12 18:10 +0200
              Re: [PATCH v2 net-next] sky2: use random address if EEPROM is bad Sergei Shtylyov <sergei.shtylyov@cogentembedded.com> - 2015-08-11 21:00 +0200
                Re: [PATCH v2 net-next] sky2: use random address if EEPROM is bad Liviu Dudau <Liviu.Dudau@arm.com> - 2015-08-12 11:20 +0200
  Re: [PATCH] sky2: Add module parameter for passing the MAC address Liviu Dudau <Liviu.Dudau@arm.com> - 2015-08-05 19:20 +0200
  Re: [PATCH] sky2: Add module parameter for passing the MAC address David Miller <davem@davemloft.net> - 2015-08-06 02:20 +0200
    Re: [PATCH] sky2: Add module parameter for passing the MAC address Liviu Dudau <Liviu.Dudau@arm.com> - 2015-08-06 12:40 +0200

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