[U-Boot-Users] Duplicate IP address check

[U-Boot-Users] Duplicate IP address check

[Dan Batryn]

        Due to a mis-configuration of our DHCP server there was an overlapping range of DHCP assigned IP address and units configured to have IP addresses statically assigned.  I was surprised to find that UBOOT did not complain of a duplicate IP address while trying to boot via the network.  Looking through the source I cannot see any code to perform the typical ARP for yourself check that I have seen before.  Could someone please tell me if I have overlooked something or is this feature missing?




Daniel Batryn
Shoretel Inc.
960 Stewart
Sunnyvale, CA  94085
Phone:  (408) 331-3575
Fax:    (408) 331-3333

[U-Boot-Users] Duplicate IP address check

[Ben Warren]

Hi Dan,

Dan Batryn wrote:
>         Due to a mis-configuration of our DHCP server there was an overlapping range of DHCP assigned IP address and units configured to have IP addresses statically assigned.  I was surprised to find that UBOOT did not complain of a duplicate IP address while trying to boot via the network.  Looking through the source I cannot see any code to perform the typical ARP for yourself check that I have seen before.  Could someone please tell me if I have overlooked something or is this feature missing?
>
>   
There is no explicit check for duplicate IP assignment. U-boot's 
networking code is intentionally minimalist and thus lacks many such 
features. Feel free to provide a patch and a convincing argument of why 
it's needed.

regards,
Ben

[U-Boot-Users] Duplicate IP address check

[gvb.uboot]

Ben Warren wrote:
> Hi Dan,
> 
> Dan Batryn wrote:
>> Due to a mis-configuration of our DHCP server there was an
>> overlapping range of DHCP assigned IP address and units configured
>> to have IP addresses statically assigned.  I was surprised to find
>> that UBOOT did not complain of a duplicate IP address while trying
>> to boot via the network.  Looking through the source I cannot see
>> any code to perform the typical ARP for yourself check that I have
>> seen before.  Could someone please tell me if I have overlooked
>> something or is this feature missing?
>>
>>   
> There is no explicit check for duplicate IP assignment. U-boot's 
> networking code is intentionally minimalist and thus lacks many such 
> features. Feel free to provide a patch and a convincing argument of why 
> it's needed.
> 
> regards,
> Ben

Ditto on the patch.

WRT the convincing argument, I think the bar would be *really* low on 
this one. :-)  I would consider a convincing argument to be "The nearly 
universal convention of performing an ARP to verify that the 
DHCP-assigned IP address is unused is missing."

Best regards,
gvb

[U-Boot-Users] Duplicate IP address check

[Ben Warren]

gvb.uboot wrote:
> Ben Warren wrote:
>> Hi Dan,
>>
>> Dan Batryn wrote:
>>> Due to a mis-configuration of our DHCP server there was an
>>> overlapping range of DHCP assigned IP address and units configured
>>> to have IP addresses statically assigned. I was surprised to find
>>> that UBOOT did not complain of a duplicate IP address while trying
>>> to boot via the network. Looking through the source I cannot see
>>> any code to perform the typical ARP for yourself check that I have
>>> seen before. Could someone please tell me if I have overlooked
>>> something or is this feature missing?
>>>
>> There is no explicit check for duplicate IP assignment. U-boot's 
>> networking code is intentionally minimalist and thus lacks many such 
>> features. Feel free to provide a patch and a convincing argument of 
>> why it's needed.
>>
>> regards,
>> Ben
>
> Ditto on the patch.
>
> WRT the convincing argument, I think the bar would be *really* low on 
> this one. :-) I would consider a convincing argument to be "The nearly 
> universal convention of performing an ARP to verify that the 
> DHCP-assigned IP address is unused is missing."
Sure, this is a no-brainer. But, it shouldn't be limited to DHCP since 
having a dynamic address trouncing a static one is only one trouble 
scenario. Who knows, there may be people out there who object to the 
extra milliseconds that this ARP will add to boot time (not me).

regards,
Ben

[U-Boot-Users] Duplicate IP address check

[gvb.uboot]

Ben Warren wrote:
> gvb.uboot wrote:
>> Ben Warren wrote:
>>> Hi Dan,
>>>
>>> Dan Batryn wrote:
>>>> Due to a mis-configuration of our DHCP server there was an
>>>> overlapping range of DHCP assigned IP address and units configured
>>>> to have IP addresses statically assigned. I was surprised to find
>>>> that UBOOT did not complain of a duplicate IP address while trying
>>>> to boot via the network. Looking through the source I cannot see
>>>> any code to perform the typical ARP for yourself check that I have
>>>> seen before. Could someone please tell me if I have overlooked
>>>> something or is this feature missing?
>>>>
>>> There is no explicit check for duplicate IP assignment. U-boot's 
>>> networking code is intentionally minimalist and thus lacks many such 
>>> features. Feel free to provide a patch and a convincing argument of 
>>> why it's needed.
>>>
>>> regards,
>>> Ben
>>
>> Ditto on the patch.
>>
>> WRT the convincing argument, I think the bar would be *really* low on 
>> this one. :-) I would consider a convincing argument to be "The nearly 
>> universal convention of performing an ARP to verify that the 
>> DHCP-assigned IP address is unused is missing."
> Sure, this is a no-brainer. But, it shouldn't be limited to DHCP since 
> having a dynamic address trouncing a static one is only one trouble 
> scenario. Who knows, there may be people out there who object to the 
> extra milliseconds that this ARP will add to boot time (not me).
> 
> regards,
> Ben

Ahh, so right.  It is actually a worse risk for human-assigned 
addresses.  s/DHCP-//

It would be simple enough to have a configurable ARP response wait 
timeout and use a special value (say <= 0) to disable the ARP test.

gvb