* [ECOS] Redboot responds to ICMP echo when it shouldn't.
@ 2011-03-21 20:49 Grant Edwards
2011-03-21 21:36 ` Gary Thomas
0 siblings, 1 reply; 5+ messages in thread
From: Grant Edwards @ 2011-03-21 20:49 UTC (permalink / raw)
To: ecos-discuss
While testing my rewrite of Redboot DHCP support, I've noticed that
Redboots "ping" support is also broken. Redboot responds to ICMP echo
requests that it shouldn't.
Redboot will respond to ICMP echo requests _before_ it has received an
IP address from the BOOTP/DHCP server. The destination IP address in
the ICMP echo packet _does_not_match_ Redboot's IP address, but it
responds anyway with a source IP address of 0.0.0.0.
Is this behavior intentional?
If so, why?
--
Grant Edwards grant.b.edwards Yow! ... I see TOILET
at SEATS ...
gmail.com
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [ECOS] Redboot responds to ICMP echo when it shouldn't.
2011-03-21 20:49 [ECOS] Redboot responds to ICMP echo when it shouldn't Grant Edwards
@ 2011-03-21 21:36 ` Gary Thomas
2011-03-22 11:16 ` [ECOS] " Grant Edwards
0 siblings, 1 reply; 5+ messages in thread
From: Gary Thomas @ 2011-03-21 21:36 UTC (permalink / raw)
To: Grant Edwards; +Cc: ecos-discuss
On 03/21/2011 02:21 PM, Grant Edwards wrote:
> While testing my rewrite of Redboot DHCP support, I've noticed that
> Redboots "ping" support is also broken. Redboot responds to ICMP echo
> requests that it shouldn't.
>
> Redboot will respond to ICMP echo requests _before_ it has received an
> IP address from the BOOTP/DHCP server. The destination IP address in
> the ICMP echo packet _does_not_match_ Redboot's IP address, but it
> responds anyway with a source IP address of 0.0.0.0.
>
> Is this behavior intentional?
Not as far as I know.
How are those packets even being received? Are they going to a broadcast
address (IP or ESA)? Normally incoming packets are filtered by ESA by
the network driver before they get pushed up the stack and processed.
You might find that RedBoot replies to [some, maybe all] packets which
somehow match it's ESA, but not IP address as well.
>
> If so, why?
>
--
------------------------------------------------------------
Gary Thomas | Consulting for the
MLB Associates | Embedded world
------------------------------------------------------------
--
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
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^ permalink raw reply [flat|nested] 5+ messages in thread
* [ECOS] Re: Redboot responds to ICMP echo when it shouldn't.
2011-03-21 21:36 ` Gary Thomas
@ 2011-03-22 11:16 ` Grant Edwards
2011-03-22 13:05 ` Gary Thomas
0 siblings, 1 reply; 5+ messages in thread
From: Grant Edwards @ 2011-03-22 11:16 UTC (permalink / raw)
To: ecos-discuss
On 2011-03-21, Gary Thomas <gary@mlbassoc.com> wrote:
> On 03/21/2011 02:21 PM, Grant Edwards wrote:
>> While testing my rewrite of Redboot DHCP support, I've noticed that
>> Redboots "ping" support is also broken. Redboot responds to ICMP echo
>> requests that it shouldn't.
>>
>> Redboot will respond to ICMP echo requests _before_ it has received an
>> IP address from the BOOTP/DHCP server. The destination IP address in
>> the ICMP echo packet _does_not_match_ Redboot's IP address, but it
>> responds anyway with a source IP address of 0.0.0.0.
>>
>> Is this behavior intentional?
>
> Not as far as I know.
>
> How are those packets even being received?
The "pinging" host's ARP cache still has RedBoot's MAC address
associated with the IP address bing pinged.
> Are they going to a broadcast address (IP or ESA)?
Unicast Ethernet MAC, unicast IP.
> Normally incoming packets are filtered by ESA by the network driver
> before they get pushed up the stack and processed.
Right. And then the IP layer should filter them by IP address, right?
> You might find that RedBoot replies to [some, maybe all] packets
> which somehow match it's ESA, but not IP address as well.
That appears to be the case.
I assumed that devices shouldn't respond to ICMP ping requests that
don't match their IP address. Am I wrong?
The DHCP server (which is sending the ICMP echo request before
offering an IP address) appears to be ignoring the reply from IP
address 0.0.0.0, but I can imagine somewhat contrived situations where
it might cause problems.
--
Grant Edwards grant.b.edwards Yow! Let's all show human
at CONCERN for REVERAND MOON's
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [ECOS] Re: Redboot responds to ICMP echo when it shouldn't.
2011-03-22 11:16 ` [ECOS] " Grant Edwards
@ 2011-03-22 13:05 ` Gary Thomas
2011-03-22 13:35 ` Grant Edwards
0 siblings, 1 reply; 5+ messages in thread
From: Gary Thomas @ 2011-03-22 13:05 UTC (permalink / raw)
To: Grant Edwards; +Cc: ecos-discuss
On 03/21/2011 02:36 PM, Grant Edwards wrote:
> On 2011-03-21, Gary Thomas<gary@mlbassoc.com> wrote:
>> On 03/21/2011 02:21 PM, Grant Edwards wrote:
>>> While testing my rewrite of Redboot DHCP support, I've noticed that
>>> Redboots "ping" support is also broken. Redboot responds to ICMP echo
>>> requests that it shouldn't.
>>>
>>> Redboot will respond to ICMP echo requests _before_ it has received an
>>> IP address from the BOOTP/DHCP server. The destination IP address in
>>> the ICMP echo packet _does_not_match_ Redboot's IP address, but it
>>> responds anyway with a source IP address of 0.0.0.0.
>>>
>>> Is this behavior intentional?
>>
>> Not as far as I know.
>>
>> How are those packets even being received?
>
> The "pinging" host's ARP cache still has RedBoot's MAC address
> associated with the IP address bing pinged.
>
>> Are they going to a broadcast address (IP or ESA)?
>
> Unicast Ethernet MAC, unicast IP.
This is happening because of a stale ARP cache on your host.
>
>> Normally incoming packets are filtered by ESA by the network driver
>> before they get pushed up the stack and processed.
>
> Right. And then the IP layer should filter them by IP address, right?
>
>> You might find that RedBoot replies to [some, maybe all] packets
>> which somehow match it's ESA, but not IP address as well.
>
> That appears to be the case.
>
> I assumed that devices shouldn't respond to ICMP ping requests that
> don't match their IP address. Am I wrong?
No, I think you are correct. The IP code may match if the local IP address
is set to IPANY (i.e. 0.0.0.0).
>
> The DHCP server (which is sending the ICMP echo request before
> offering an IP address) appears to be ignoring the reply from IP
> address 0.0.0.0, but I can imagine somewhat contrived situations where
> it might cause problems.
This seems to be a pretty rare condition, caused by a stale ARP cache.
--
------------------------------------------------------------
Gary Thomas | Consulting for the
MLB Associates | Embedded world
------------------------------------------------------------
--
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss
^ permalink raw reply [flat|nested] 5+ messages in thread
* [ECOS] Re: Redboot responds to ICMP echo when it shouldn't.
2011-03-22 13:05 ` Gary Thomas
@ 2011-03-22 13:35 ` Grant Edwards
0 siblings, 0 replies; 5+ messages in thread
From: Grant Edwards @ 2011-03-22 13:35 UTC (permalink / raw)
To: ecos-discuss
On 2011-03-21, Gary Thomas <gary@mlbassoc.com> wrote:
>>> How are those packets even being received?
>>
>> The "pinging" host's ARP cache still has RedBoot's MAC address
>> associated with the IP address bing pinged.
>>
>>> Are they going to a broadcast address (IP or ESA)?
>>
>> Unicast Ethernet MAC, unicast IP.
>
> This is happening because of a stale ARP cache on your host.
Right.
>>> Normally incoming packets are filtered by ESA by the network driver
>>> before they get pushed up the stack and processed.
>>
>> Right. And then the IP layer should filter them by IP address, right?
>>
>>> You might find that RedBoot replies to [some, maybe all] packets
>>> which somehow match it's ESA, but not IP address as well.
>>
>> That appears to be the case.
>>
>> I assumed that devices shouldn't respond to ICMP ping requests that
>> don't match their IP address. Am I wrong?
>
> No, I think you are correct. The IP code may match if the local IP
> address is set to IPANY (i.e. 0.0.0.0).
But doesn't Redboot use 0.0.0.0 as a sentinel value meaning "I don't
have an IP address" rather than "my address is IP_ANY"?
>> The DHCP server (which is sending the ICMP echo request before
>> offering an IP address) appears to be ignoring the reply from IP
>> address 0.0.0.0, but I can imagine somewhat contrived situations
>> where it might cause problems.
>
> This seems to be a pretty rare condition, caused by a stale ARP
> cache.
Agreed.
--
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at parking meter on Darvon!
gmail.com
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2011-03-21 20:49 [ECOS] Redboot responds to ICMP echo when it shouldn't Grant Edwards
2011-03-21 21:36 ` Gary Thomas
2011-03-22 11:16 ` [ECOS] " Grant Edwards
2011-03-22 13:05 ` Gary Thomas
2011-03-22 13:35 ` Grant Edwards
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