š
Original date posted:2015-10-27
š Original message:
On Wed, Oct 28, 2015 at 06:11:20AM +1030, Rusty Russell wrote:
> Pierre <pm+lists at acinq.fr> writes:
> > Hi Rusty,
> >
> >> 5) Unknown protobuf fields are handled in the protocol as follows
> >> (including in the initial Authenticate packet):
> >>
> >> 1) Odd numbered fields are optional, and backwards compatible.
> >> 2) Even numbered fields are required; abort if you get one.
> >
> > I don't get it, what is it about ?
>
> Yes, I really need to write this up in Matsjj's lightning-core docs
> repository.
>
> Since protobuf fields are explicitly numbered, we can use this to
> deliberately break backwards compatibility in future after some
> transition.
>
> For example, if we want to add a "currency identifier" field in HTLC,
> for non-bitcoin transactions. That would be an even numbered field,
> since you need to understand it. (There would also need to be some way
> to indicate you support those, during connection setup or something).
>
> But if we want to add an optional new field, we'd make it odd, and
> existing implementations could ignore it.
FWIW an analogous idea is OpenPGP's "critical bit" for packets, which
indicates that if the software doesn't understand the packet it should
consider the signature to be invalid:
https://tools.ietf.org/html/rfc4880#section-5.2.3.1
--
'peter'[:-1]@petertodd.org
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Peter Todd [ARCHIVE] /
npub1m2ā¦a2np2
2023-06-09 12:44:56
in reply to nevent1qā¦u3r8
Author Public Key
npub1m230cem2yh3mtdzkg32qhj73uytgkyg5ylxsu083n3tpjnajxx4qqa2np2Published at
2023-06-09 12:44:56Event JSON
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Original date posted:2015-10-27\nš Original message:\nOn Wed, Oct 28, 2015 at 06:11:20AM +1030, Rusty Russell wrote:\n\u003e Pierre \u003cpm+lists at acinq.fr\u003e writes:\n\u003e \u003e Hi Rusty,\n\u003e \u003e\n\u003e \u003e\u003e 5) Unknown protobuf fields are handled in the protocol as follows\n\u003e \u003e\u003e (including in the initial Authenticate packet):\n\u003e \u003e\u003e\n\u003e \u003e\u003e 1) Odd numbered fields are optional, and backwards compatible.\n\u003e \u003e\u003e 2) Even numbered fields are required; abort if you get one.\n\u003e \u003e\n\u003e \u003e I don't get it, what is it about ?\n\u003e \n\u003e Yes, I really need to write this up in Matsjj's lightning-core docs\n\u003e repository.\n\u003e \n\u003e Since protobuf fields are explicitly numbered, we can use this to\n\u003e deliberately break backwards compatibility in future after some\n\u003e transition.\n\u003e \n\u003e For example, if we want to add a \"currency identifier\" field in HTLC,\n\u003e for non-bitcoin transactions. That would be an even numbered field,\n\u003e since you need to understand it. (There would also need to be some way\n\u003e to indicate you support those, during connection setup or something).\n\u003e \n\u003e But if we want to add an optional new field, we'd make it odd, and\n\u003e existing implementations could ignore it.\n\nFWIW an analogous idea is OpenPGP's \"critical bit\" for packets, which\nindicates that if the software doesn't understand the packet it should\nconsider the signature to be invalid:\n\nhttps://tools.ietf.org/html/rfc4880#section-5.2.3.1\n\n-- \n'peter'[:-1]@petertodd.org\n00000000000000000b3f41bf1f2b9c5547bbdaa1ab40c914ab26faf764ff16a5\n-------------- next part --------------\nA non-text attachment was scrubbed...\nName: signature.asc\nType: application/pgp-signature\nSize: 650 bytes\nDesc: Digital signature\nURL: \u003chttp://lists.linuxfoundation.org/pipermail/lightning-dev/attachments/20151027/1b0bc972/attachment.sig\u003e",
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