public inbox for bitcoindev@googlegroups.com
 help / color / mirror / Atom feed
From: Andrew Chow <achow101-lists@achow101.com>
To: Juan Garavaglia <jg@112bit.com>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] Issolated Bitcoin Nodes
Date: Thu, 23 Mar 2017 19:14:28 -0400	[thread overview]
Message-ID: <3fd9846c-6c57-9b57-0b6e-e5958e644e1d@achow101.com> (raw)
In-Reply-To: <SC1P152MB1648D0F9DF4279C49D755233F53F0@SC1P152MB1648.LAMP152.PROD.OUTLOOK.COM>

[-- Attachment #1: Type: text/plain, Size: 3062 bytes --]

The issue is due to Segwit blocks since Testnet has already activated
Segwit. 0.12.x- nodes will receive a Segwit block with all of the
witnesses stripped. When they relay this block to a 0.13.0+ node, the
block will be rejected because those have Segwit functionality and
require the witnesses to be in the block. Given that Testnet has a
smaller number of nodes and less difficulty, this could result in some
miners using 0.13.0+ mining blocks which do not propagate well and thus
causing multiple chain splits and reorgs as other miners find blocks for
the same height before receiving a block for that height.


On 3/23/2017 6:37 PM, Juan Garavaglia via bitcoin-dev wrote:
>
> We notice some reorgs in Bitcoin testnet, while reorgs in testnet are
> common and may be part of different tests and experiments, it seems
> the forks are not created by a single user and multiple blocks were
> mined by different users in each chain.  My first impression was that
> the problem was related to network issues but some Bitcoin explorers
> were following one chain while others follow the other one. 
> Nonetheless, well established explorers like blocktrail.com or
> blockr.io were following different chains at different heights which
> led to me to believe that it was not a network issue. After some time,
> a reorg occurs and it all comes to normal state as a single chain.
>
> We started investigating more and we identified that the fork occurs
> with nodes 0.12; in some situations, nodes 0.12 has longer/different
> chains. The blocks in both chains are valid so something must be
> occurring in the communication between nodes but not related with the
> network itself.
>
> Long story short, when nodes 0.13+ receive blocks from 0.13+ nodes all
> is ok, and those blocks propagate to older nodes with no issues. But
> when a block tries to be propagated from bitcoind 0.12.+ to newer ones
> those blocks are NOT being propagated to the peers with newer versions
> while these newer blocks are being propagated to peers with older
> versions with no issues.
>
> My conclusion is that we have a backward compatibility issue between
> 0.13.X+ and older versions.
>
> The issue is simple to replicate, first, get latest version of
> bitcoind, complete the IBD after is at current height, then force it
> to use exclusively one or more peers of versions 0.12.X and older, and
> you will notice that the latest version node will never receive a new
> block.
>
> Probably some alternative bitcoin implementations act as bridges
> between these two versions and facilitate the chain reorgs.
>
> I have not yet found any way where/how it can be used in a malicious
> way or be exploited by a miner but in theory Bitcoin 0.13.X+ should
> remain compatible with older ones, but a 0.13+ node may become
> isolated by 0.12 peers, and there is not notice for the node owner.
>
>  
>
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev


[-- Attachment #2: Type: text/html, Size: 5965 bytes --]

  parent reply	other threads:[~2017-03-23 23:14 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-23 22:37 [bitcoin-dev] Issolated Bitcoin Nodes Juan Garavaglia
2017-03-23 23:01 ` Matt Corallo
2017-03-23 23:14 ` Andrew Chow [this message]
2017-03-24  3:38   ` Andrew Chow
2017-03-24  0:20 ` Pieter Wuille
2017-03-24  0:31   ` James Hilliard
2017-03-24  1:58   ` Eric Voskuil

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=3fd9846c-6c57-9b57-0b6e-e5958e644e1d@achow101.com \
    --to=achow101-lists@achow101.com \
    --cc=bitcoin-dev@lists.linuxfoundation.org \
    --cc=jg@112bit.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox