[ipxe-devel] Intel 82576 MAC swapping

[Kieran Evans]

Hi, unless I'm mis-reading this, or I've misunderstood, this code looks 
like it will always use the EEPROM MAC if it exists (i.e. the return 0 
after intel_fetch_mac_eeprom is before the is_valid_ether_addr, so it'll 
never be reached).


static int intel_fetch_mac ( struct intel_nic *intel, uint8_t *hw_addr ) {
union intel_receive_address mac;
int rc;
/* Read current address from RAL0/RAH0 */
mac.reg.low = cpu_to_le32 ( readl ( intel->regs + INTEL_RAL0 ) );
mac.reg.high = cpu_to_le32 ( readl ( intel->regs + INTEL_RAH0 ) );
DBGC ( intel, "INTEL %p has autoloaded MAC address %s\n",
intel, eth_ntoa ( mac.raw ) );
/* Try to read address from EEPROM */
if ( ( rc = intel_fetch_mac_eeprom ( intel, hw_addr ) ) == 0 )
return 0;
/* Use current address if valid */
if ( is_valid_ether_addr ( mac.raw ) ) {
memcpy ( hw_addr, mac.raw, ETH_ALEN );
return 0;
}
DBGC ( intel, "INTEL %p has no MAC address to use\n", intel );
return -ENOENT;
}


It seems like this is the correct way to do things, as if a user has 
burned a custom MAC into the EEPROM, then that's the one to use. I 
assume (though I can't find any info to back this up) that intel burns 
the default MAC into the eeprom too, and that's why there's MAC 
addresses in the EEPROM even though I never changed them. Could this 
issue be down to PCI device enumeration? I.e. the two ports are being 
enumerated in a different order by iPXE than elsewhere, so even though 
the auto-assigned mac is correct, when it checks the EEPROM, it's seeing 
a different value because  it thinks port 0 is port 1 and port 1 is 0?

/Kieran

Also, oops, forgot to reply to the list,  last time, so list email added 
back in.

On 27/07/2012 10:40, Anton D. Kachalov wrote:
> EEPROM macs used only when autoloaded is not complain by "is_valid_ether_addr" routine (lines 226-230). Try to add more debug messages here to track why driver going to use EEPROM's MAC instead of autloaded.
>
> 27.07.2012, 13:14, "Kieran Evans" <keyz182 at gmail.com>:
>> Hmm, it seems that the autoloaded and EEPROM MACs are at odds (I'm the
>> only person to have touched these servers since they were purchased, and
>> no modification of the EEPROM has been made, no setting of alternate MAC
>> addresses etc).
>>
>> http://dbyz.co.uk/ipxe1.png
>> http://dbyz.co.uk/ipxe2.png
>>
>> After seeing that, I can think of two possible temporary workarounds,
>> but not sure about perminent fixes.
>>
>> Workaround A: Set the MACs in EEPROM the other way around. (May then
>> confuse linux, so needs checking)
>> Workaround B: Compile iPXE with Mac loading from the EEPROM disabled
>> (Comment out line 223+224 of src/drivers/net/intel.c ?)
>>
>> Any ideas on a more perminent workaround/fix? I'm fairly lucky as I only
>> have 4 servers with this NIC/Problem, so modifying the eeprom is only
>> half an hour of my time, but this could be a much bigger issue elsewhere.
>>

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