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From: Ethan Heilman <eth3rs@gmail.com>
Date: Thu, 15 Dec 2016 17:44:55 -0500
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To: =?UTF-8?B?Sm9yZ2UgVGltw7Nu?= <jtimon@jtimon.cc>, 
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] Planned Obsolescence
Precedence: list

I assume this has been well discussed in at some point in the Bitcoin
community, so I apologize if I'm repeating old ideas.

Problem exploitable nodes:
It is plausible that people running these versions of bitcoind may not
be applying patches. Thus, these nodes may be vulnerable to known
exploits. I would hope none of these nodes are gateway nodes for
miners, web wallets or exchanges. How difficult would it be to crawl
the network to find vulnerable nodes and exploit them? What percentage
of the network is running vulnerable versions of bitcoind?

Problem eclipsable nodes:
Currently a bitcoind node disconnects from any node with a version
below MIN_PEER_PROTO_VERSION. Such nodes become be ripe for an eclipse
attack because they are partitioned from the newer nodes, especially
when they are "freshly obsolete". I have not examined how protocol
versioning works in detail so I could be missing something.

One option could be that after a grace period:
1. to still connect to obsolete nodes and even to transmit blockheaders,
2. but to stop sending the full-blocks and transactions to these
nodes, thereby alerting the operator that something is wrong and
causing them to upgrade.
It may make sense to create this as a rule, if your longest chain
consists of only blockheaders and no one will tell you the
transactions for over 1000 blocks you are obsolete, spit out an error
message and shutdown.

This would not address the issue of alt-coins which are forked from
old vulnerable versions of bitcoind, but that is probably out of
scope.

On Thu, Dec 15, 2016 at 1:48 PM, Jorge Tim=C3=B3n via bitcoin-dev
<bitcoin-dev@lists.linuxfoundation.org> wrote:
> On Thu, Dec 15, 2016 at 4:38 AM, Juan Garavaglia via bitcoin-dev
> <bitcoin-dev@lists.linuxfoundation.org> wrote:
>> Older node versions may generate issues because some upgrades will make
>> several of the nodes running older protocol versions obsolete and or
>> incompatible. There may be other hard to predict behaviors on older vers=
ions
>> of the client.
>
> Hard to predict or not, you can't force people to run newer software.
>
>> In order to avoid such wide fragmentation of "Bitcoin Core=E2=80=9D node=
 versions
>> and to help there be a more predictable protocol improvement process, I
>> consider it worth it to analyze introducing some planned obsolescence in
>> each new version. In the last year we had 4 new versions so if each vers=
ion
>> is valid for about 1 year (52560 blocks) this may be a reasonable time f=
rame
>> for node operators to upgrade. If a node does not upgrade it will stop
>> working instead of participating in the network with an outdated protoco=
l
>> version.
>
> When you introduce anti-features like this in free software they can
> be trivially removed and they likely will.
>
>> These changes may also simplify the developer's jobs in some cases by
>> avoiding them having to deal with ancient versions of the client.
>
> There's a simpler solution for this which is what is being done now:
> stop maintaining and giving support for older versions.
> There's limited resources and developers are rarely interested in
> fixing bugs for very old versions. Users shouldn't expect things to be
> backported to old versions (if developers do it and there's enough
> testing, there's no reason not to do more releases of old versions, it
> is just rarely the case).
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