Re: [Bitcoin-development] Missing fRelayTxes in version message
I never said that Bitcoin message field lengths should always be the same. But
before this change they certainly were constant per protocol version. All I'm
saying is that optional lengths shouldn't be used (a field exists or not) and
for every field change, the protocol version should be upgraded.
Now that fRelayTxes is part of the protocol, the version number should be
upgraded to reflect this fact.
From: Mike Hearn m...@plan99.net
To: Paul Lyon pml...@hotmail.ca
Cc: Turkey Breast turkeybre...@yahoo.com;
bitcoin-development@lists.sourceforge.net
bitcoin-development@lists.sourceforge.net
Sent: Wednesday, June 19, 2013 3:20 PM
Subject: Re: [Bitcoin-development] Missing fRelayTxes in version message
If you want to criticise the Bitcoin protocol for sloppyness, the variable
length of some messages isn't where I'd start.
Note that ping has the same issue, its length has changed over time to include
the nonce.
If your parser can't handle that kind of thing, you need to fix it. The
protocol has always worked that way.
On Wed, Jun 19, 2013 at 3:03 PM, Paul Lyon pml...@hotmail.ca wrote:
I’m also running into this exact same issue with my parser, now I understand
why the relay field behavior I was seeing doesn’t match the wiki.
So to parse a version message, you can’t rely on the protocol version? You
have to know how long the payload is, and then parse the message accordingly?
I agree with Turkey Breast, this seems a bit sloppy to me.
Paul
P.S. I’ve never used a dev mailing list before and I want to get involved with
the Bitcoin dev community, so let me know if I’m horribly violating any
mailing list etiquette.
From: Mike Hearn
Sent: Wednesday, June 19, 2013 7:43 AM
To: Turkey Breast
Cc: bitcoin-development@lists.sourceforge.net
Bitcoin-Qt on master does send it now although it doesn't affect anything, but
as old pre-filtering versions will continue to exist, you'll always have to be
able to deserialize version messages without it.
Bitcoin version messages have always had variable length, look at how the code
is written in main.cpp. If you didn't experience issues until now all it means
is that no sufficiently old nodes were talking to yours.
The standard does not say it should appear. Read it again - BIP 37 says about
the new version message field:
If false then broadcast transactions will not be announced until a
filter{load,add,clear} command is received. If missing or true, no change in
protocol behaviour occurs.
On Wed, Jun 19, 2013 at 12:33 PM, Turkey Breast turkeybre...@yahoo.com wrote:
It's a problem if you work with iterators to deserialize the byte stream. Even
failing that, it's just sloppy programming. What happens in the future when
new fields are added to the version message? It's not a big deal to say that
this protocol version has X number of fields, that (higher) protocol version
message has X + N number of fields. Deterministic number of fields per
protocol version is sensical and how Bitcoin has been for a long time.
And yes, it was a problem for me that caused a lot of confusion why this byte
didn't exist in many version messages despite the standard saying it should
and the code in bitcoind indicating it should. Nowhere was this written. It
doesn't help other implementations to have an unclear behaviour that depends
on some magic from one implementation.
From: Mike Hearn m...@plan99.net
To: Turkey Breast turkeybre...@yahoo.com
Cc: bitcoin-development@lists.sourceforge.net
bitcoin-development@lists.sourceforge.net
Sent: Wednesday, June 19, 2013 11:39 AM
Subject: Re: [Bitcoin-development] Missing fRelayTxes in version message
It has to be optional because old clients don't send it, obviously.
Why is this even an issue? There's no problem with variable length messages
in any codebase that I'm aware of. Is this solving some actual problem?
On Wed, Jun 19, 2013 at 12:30 AM, Turkey Breast turkeybre...@yahoo.com
wrote:
That's me. I never said to make all messages fixed length. I said to make a
fixed number of fields per protocol. So given a protocol version number, you
know the number of fields in a message. This is not only easier for parsing
messages, but just good practice. I don't see why a 1 byte flag needs to be
optional anyway.
From: Mike Hearn m...@plan99.net
To: Turkey Breast turkeybre...@yahoo.com
Cc: Bitcoin Dev bitcoin-development@lists.sourceforge.net
Sent: Tuesday, June 18, 2013 9:48 PM
Subject: Re: [Bitcoin-development] Missing fRelayTxes in version message
It's not a bug (although there was recently a change to make bitcoind/qt
always send this field anyway).
I don't know where Amir is going with BIP 60. Version messages have always
been variable length. There's nothing inherent in the Bitcoin protocol that
says all messages are fixed length, indeed, tx messages
Re: [Bitcoin-development] Missing fRelayTxes in version
I don't get why this is such a contentious change? Before I was able to use asserts to check the expected length of length of messages per protocol version, I could pass in dumb iterators that just parse the byte stream and I could serialize and deserialize a message to check the parser is correct (in debug mode). This 'simple' change causes all that behaviour to be lost. You can no longer just use iterators but must know the remaining length (or if you use std::distance, you can only use specific std containers - not just anything with an iterator and an operator++). You cannot check the deserialization process by serializing the deserialized message and comparing it to the original data (because the bool is always present in the serializer). It's a bit stupid you call it buggy code when this behaviour has never been present in Bitcoin. The BIP doesn't introduce any unwanted side-effects and is a trivial reasonable change. If you want optional fields then the proper way to do it, is to either set a flag in the Services field of the version message to indicate different formats for messages (i.e use this template structure for a message, not that one), introduce a new message (if the changes are big), to approve/improve Stefan's BIP 32 for custom services or to have a value in the byte stream indicating which fields are present (maybe a bitfield or so). Using a quirk of an implementation is just bad form and sloppy coding. Optional fields should have their own mechanism that allows them to remain as optional fields between protocol version upgrades. The bitcoind software can probably be improved too, by checking that the length of the version message is consistent for the protocol version given by the connected node. Right now it makes no assumptions based on that which is a mistake (new clients can broadcast older version messages that don't have all the fields required). Probably the software should penalise hosts which do that. What's the big deal to update the protocol version number from 70001 to 70002? It's not like we'll run out of integers. The field has now gone from optional to required now anyway - that's a behaviour change. It'd be good to enforce that. I see this as a bug. From: Mike Hearn m...@plan99.net To: Pieter Wuille pieter.wui...@gmail.com Cc: Bitcoin Dev bitcoin-development@lists.sourceforge.net; Tamas Blummer ta...@bitsofproof.com Sent: Thursday, June 20, 2013 11:17 AM Subject: Re: [Bitcoin-development] Missing fRelayTxes in version 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 pieter.wui...@gmail.com 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
Re: [Bitcoin-development] Missing fRelayTxes in version message
It's a problem if you work with iterators to deserialize the byte stream. Even failing that, it's just sloppy programming. What happens in the future when new fields are added to the version message? It's not a big deal to say that this protocol version has X number of fields, that (higher) protocol version message has X + N number of fields. Deterministic number of fields per protocol version is sensical and how Bitcoin has been for a long time. And yes, it was a problem for me that caused a lot of confusion why this byte didn't exist in many version messages despite the standard saying it should and the code in bitcoind indicating it should. Nowhere was this written. It doesn't help other implementations to have an unclear behaviour that depends on some magic from one implementation. From: Mike Hearn m...@plan99.net To: Turkey Breast turkeybre...@yahoo.com Cc: bitcoin-development@lists.sourceforge.net bitcoin-development@lists.sourceforge.net Sent: Wednesday, June 19, 2013 11:39 AM Subject: Re: [Bitcoin-development] Missing fRelayTxes in version message It has to be optional because old clients don't send it, obviously. Why is this even an issue? There's no problem with variable length messages in any codebase that I'm aware of. Is this solving some actual problem? On Wed, Jun 19, 2013 at 12:30 AM, Turkey Breast turkeybre...@yahoo.com wrote: That's me. I never said to make all messages fixed length. I said to make a fixed number of fields per protocol. So given a protocol version number, you know the number of fields in a message. This is not only easier for parsing messages, but just good practice. I don't see why a 1 byte flag needs to be optional anyway. From: Mike Hearn m...@plan99.net To: Turkey Breast turkeybre...@yahoo.com Cc: Bitcoin Dev bitcoin-development@lists.sourceforge.net Sent: Tuesday, June 18, 2013 9:48 PM Subject: Re: [Bitcoin-development] Missing fRelayTxes in version message It's not a bug (although there was recently a change to make bitcoind/qt always send this field anyway). I don't know where Amir is going with BIP 60. Version messages have always been variable length. There's nothing inherent in the Bitcoin protocol that says all messages are fixed length, indeed, tx messages are allowed to have arbitrary data appended after them that gets relayed. On Tue, Jun 18, 2013 at 7:45 PM, Turkey Breast turkeybre...@yahoo.com wrote: See this BIP. I'm not sure if this is a bug or what, but it would be good if messages always had a fixed number of fields per protocol version. https://en.bitcoin.it/wiki/BIP_0060#Code_Updates This BIP details everything that needs to be done and proposes a protocol upgrade. -- This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
[Bitcoin-development] Missing fRelayTxes in version message
See this BIP. I'm not sure if this is a bug or what, but it would be good if messages always had a fixed number of fields per protocol version. https://en.bitcoin.it/wiki/BIP_0060#Code_Updates This BIP details everything that needs to be done and proposes a protocol upgrade. -- This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
Re: [Bitcoin-development] Missing fRelayTxes in version message
That's me. I never said to make all messages fixed length. I said to make a fixed number of fields per protocol. So given a protocol version number, you know the number of fields in a message. This is not only easier for parsing messages, but just good practice. I don't see why a 1 byte flag needs to be optional anyway. From: Mike Hearn m...@plan99.net To: Turkey Breast turkeybre...@yahoo.com Cc: Bitcoin Dev bitcoin-development@lists.sourceforge.net Sent: Tuesday, June 18, 2013 9:48 PM Subject: Re: [Bitcoin-development] Missing fRelayTxes in version message It's not a bug (although there was recently a change to make bitcoind/qt always send this field anyway). I don't know where Amir is going with BIP 60. Version messages have always been variable length. There's nothing inherent in the Bitcoin protocol that says all messages are fixed length, indeed, tx messages are allowed to have arbitrary data appended after them that gets relayed. On Tue, Jun 18, 2013 at 7:45 PM, Turkey Breast turkeybre...@yahoo.com wrote: See this BIP. I'm not sure if this is a bug or what, but it would be good if messages always had a fixed number of fields per protocol version. https://en.bitcoin.it/wiki/BIP_0060#Code_Updates This BIP details everything that needs to be done and proposes a protocol upgrade. -- This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev ___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development -- This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev___ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
