Re: [Anima-bootstrap] Anima bootstrap: discover protocol multicast notes

Brian E Carpenter <> Tue, 17 January 2017 23:14 UTC

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From: Brian E Carpenter <>
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Date: Wed, 18 Jan 2017 12:13:59 +1300
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Subject: Re: [Anima-bootstrap] Anima bootstrap: discover protocol multicast notes
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Hi Toerless,

> (R)ight: L2 discovery protocol requirement:
> proxy needs to periodically (unsolicited) announce its proxy service via L2 multicast/broadcast
> pledge only accepts reply if it was multicast/broadcast
> pledge should then try to register via such discovered proxies.
> if multiple proxies discovered, parallel and/or sequential -> more difficult discussion

I take that as a vote for M_FLOOD

> The security of (R)ight depends on pledge being able to see if received packet from proxy was L2
> unicast or multicasted. 

Why? If a malicious node knows that pledges might be checking this, they will
multicast their bogus announcements. And how could they know the address of
a targetted pledge anyway, in order to send the bogus announcement unicast?

> This information is typically ignored in existing network protocol stacks
> and is also typically unavailable on the socket-API. This IMHO makes it highly beneficial to
> use a very lightweight protocol (like the subset of GRASP dedicate to this) that can specifically
> be implemented to do this security check.

Presumably you have to use a raw socket. I don't see any other way to get the
destination address out of the packet.


On 18/01/2017 06:28, Toerless Eckert wrote:
> Oh, and just read mDNS RFC and found the place where it prohibits
> periodic unsolicited announcements, so added that at the end.
> Michael: Would be great if you
> can figure out what you see in your network. Worst case we'll have
> to ask Stewart...
> Cheers
> Toerless
> On Tue, Jan 17, 2017 at 06:17:32PM +0100, Toerless Eckert wrote:
>> Hi folks
>> I have added my gist wrt to the discovery protocol detail i am
>> interested in to the etherpad
>>  lines 368  - 407
>> Hope this explains it better than my feeble verbal attempts during the call.
>> Cheers
>> Toerless