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Re: Redboot responds to ICMP echo when it shouldn't.
- From: Grant Edwards <grant dot b dot edwards at gmail dot com>
- To: ecos-discuss at sources dot redhat dot com
- Date: Mon, 21 Mar 2011 20:36:30 +0000 (UTC)
- Subject: [ECOS] Re: Redboot responds to ICMP echo when it shouldn't.
- References: <im8c04$f2k$1@dough.gmane.org> <4D87B4F0.4070903@mlbassoc.com>
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
gmail.com legal difficulties!!
--
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