Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1Upaza-0007eK-2q for bitcoin-development@lists.sourceforge.net; Thu, 20 Jun 2013 09:17:22 +0000 Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.214.174 as permitted sender) client-ip=209.85.214.174; envelope-from=mh.in.england@gmail.com; helo=mail-ob0-f174.google.com; Received: from mail-ob0-f174.google.com ([209.85.214.174]) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1UpazV-0006sw-5K for bitcoin-development@lists.sourceforge.net; Thu, 20 Jun 2013 09:17:22 +0000 Received: by mail-ob0-f174.google.com with SMTP id wd20so7011710obb.33 for ; Thu, 20 Jun 2013 02:17:11 -0700 (PDT) MIME-Version: 1.0 X-Received: by 10.60.133.243 with SMTP id pf19mr89718oeb.118.1371719831741; Thu, 20 Jun 2013 02:17:11 -0700 (PDT) Sender: mh.in.england@gmail.com Received: by 10.76.23.36 with HTTP; Thu, 20 Jun 2013 02:17:11 -0700 (PDT) In-Reply-To: <20130620090649.GA17765@vps7135.xlshosting.net> References: <4DE0E45E-BB48-4DFF-9C86-ACBE312B3049@bitsofproof.com> <20130620090649.GA17765@vps7135.xlshosting.net> Date: Thu, 20 Jun 2013 11:17:11 +0200 X-Google-Sender-Auth: m1YpdqqI24OSmS9JEZd_-PGGQHQ Message-ID: From: Mike Hearn To: Pieter Wuille Content-Type: multipart/alternative; boundary=047d7b47245a4d6d8d04df9269a7 X-Spam-Score: -0.5 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (mh.in.england[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 1.0 HTML_MESSAGE BODY: HTML included in message 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-Headers-End: 1UpazV-0006sw-5K Cc: Bitcoin Dev , Tamas Blummer Subject: Re: [Bitcoin-development] Missing fRelayTxes in version X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 20 Jun 2013 09:17:22 -0000 --047d7b47245a4d6d8d04df9269a7 Content-Type: text/plain; charset=UTF-8 There's no problem, but there's no benefit either. It also locks us in to a potentially problematic guarantee - what if in future we want to have, say, two optional new pieces of data in two different messages. We don't want to require that if version > X then you have to implement all features up to and including that point. Essentially the number of fields in a message is like a little version number, just for that message. It adds flexibility to keep it that way, and there's no downside, seeing as that bridge was already crossed and people with parsers that can't handle it need to fix their code anyway. So I have a slight preference for keeping things the way they are, it keeps things flexible for future and costs nothing. On Thu, Jun 20, 2013 at 11:06 AM, Pieter Wuille wrote: > On Thu, Jun 20, 2013 at 09:36:40AM +0200, Mike Hearn wrote: > > Sure but why not do that when there's an actual new field to add? Does > > anyone have a proposal for a feature that needs a new version field at > the > > moment? There's no point changing the protocol now unless there's > actually > > a new field to add. > > > > Anyway I still don't see why anyone cares about this issue. The Bitcoin > > protocol does not and never has required that all messages have a fixed > > number of fields per version. Any parser written on the assumption it did > > was just buggy. Look at how tx messages are relayed for the most obvious > > example of that pattern in action - it's actually the raw byte stream > > that's stored and relayed to ensure that fields added in new versions > > aren't dropped during round-tripping. Old versions are supposed to > preserve > > fields from the future. > > Actually, that is not the same issue. What is being argued for here is that > the version in the version message itself should indicate which fields are > present, so a parser doesn't need to look at the length of the message. > That > seems like a minor but very reasonable request to me, and it's trivial to > do. > That doesn't mean that you may receive versions higher than what you know > of, > and thus messages with fields you don't know about. That doesn't matter, > you > can just ignore them. > > I see no problem with raising the protocol version number to indicate > "all fields up to fRelayTxes are required, if the announced nVersion is > above N". > In fact, I believe (though haven't checked) all previous additions to the > version > message were accompanied with a protocol version (then: client version) > increase > as well. > > -- > Pieter > > --047d7b47245a4d6d8d04df9269a7 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
There's no problem, but there's no benefit either.= It also locks us in to a potentially problematic guarantee - what if in fu= ture we want to have, say, two optional new pieces of data in two different= messages. We don't want to require that if version > X then you hav= e to implement all features up to and including that point.

Essentially the number of fields in a message is like a litt= le version number, just for that message. It adds flexibility to keep it th= at way, and there's no downside, seeing as that bridge was already cros= sed and people with parsers that can't handle it need to fix their code= anyway.

So I have a slight preference for keeping things the wa= y they are, it keeps things flexible for future and costs nothing.



On Thu, Jun 20, 2013 at 11:06 AM, Pieter Wuille <pieter.wuille@gmail= .com> wrote:
On Thu, Jun 20, 2013 at 09:36:40AM +0200, Mike Hearn wrot= e:
> Sure but why not do that when there's an actual new field to add? = Does
> anyone have a proposal for a feature that needs a new version field at= the
> moment? There's no point changing the protocol now unless there= 9;s actually
> a new field to add.
>
> Anyway I still don't see why anyone cares about this issue. The Bi= tcoin
> protocol does not and never has required that all messages have a fixe= d
> number of fields per version. Any parser written on the assumption it = did
> was just buggy. Look at how tx messages are relayed for the most obvio= us
> example of that pattern in action - it's actually the raw byte str= eam
> that's stored and relayed to ensure that fields added in new versi= ons
> aren't dropped during round-tripping. Old versions are supposed to= preserve
> fields from the future.

Actually, that is not the same issue. What is being argued for here i= s that
the version in the version message itself should indicate which fields are<= br> present, so a parser doesn't need to look at the length of the message.= That
seems like a minor but very reasonable request to me, and it's trivial = to do.
That doesn't mean that you may receive versions higher than what you kn= ow of,
and thus messages with fields you don't know about. That doesn't ma= tter, you
can just ignore them.

I see no problem with raising the protocol version number to indicate
"all fields up to fRelayTxes are required, if the announced nVersion i= s above N".
In fact, I believe (though haven't checked) all previous additions to t= he version
message were accompanied with a protocol version (then: client version) inc= rease
as well.

--
Pieter


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