Re: [bitcoin-dev] Removal of reject network messages from Bitcoin Core (BIP61)

[John Newbery <john@johnnewbery.com>]

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Following discussion on this mailing list, support for BIP 61 REJECT
messages was not removed from Bitcoin Core in V0.19. The behaviour in that
upcoming release is that REJECT messages are disabled by default and can be
enabled using the `-enablebip61` command line option.

Support for REJECT messages will be removed entirely in Bitcoin Core V0.20,
expected for release in mid 2020. The PR to remove support was merged into
Bitcoin Core's master branch this week.

Adoption of new Bitcoin Core versions across reachable nodes generally
takes several months. https://bitnodes.earn.com/dashboard/?days=365 shows
that although v0.18 was released in May 2019, there are still several
hundred reachable nodes on V0.17, V0.16, V0.15 and earlier software.
Software that currently use REJECT messages from public nodes for
troubleshooting issues therefore have plenty of time to transition to one
of the methods listed by Marco in the email above.

John

On Tue, Mar 5, 2019 at 10:28 PM Marco Falke via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Bitcoin Core may send "reject" messages as response to "tx", "block" or
> "version" messages from a network peer when the message could not be
> accepted.
>
> This feature is toggled by the `-enablebip61` command line option and has
> been
> disabled by default since Bitcoin Core version 0.18.0 (not yet released as
> of
> time of writing). Nodes on the network can not generally be trusted to send
> valid ("reject") messages, so this should only ever be used when connected
> to a
> trusted node. At this time, I am not aware of any software that requires
> this
> feature, and I would like to remove if from Bitcoin Core to make the
> codebase
> slimmer, easier to understand and maintain. Let us know if your application
> relies on this feature and you can not use any of the recommended
> alternatives:
>
> * Testing or debugging of implementations of the Bitcoin P2P network
> protocol
>   should be done by inspecting the log messages that are produced by a
> recent
>   version of Bitcoin Core. Bitcoin Core logs debug messages
>   (`-debug=<category>`) to a stream (`-printtoconsole`) or to a file
>   (`-debuglogfile=<debug.log>`).
>
> * Testing the validity of a block can be achieved by specific RPCs:
>   - `submitblock`
>   - `getblocktemplate` with `'mode'` set to `'proposal'` for blocks with
>     potentially invalid POW
>
> * Testing the validity of a transaction can be achieved by specific RPCs:
>   - `sendrawtransaction`
>   - `testmempoolaccept`
>
> * Wallets should not use the absence of "reject" messages to indicate a
>   transaction has propagated the network, nor should wallets use "reject"
>   messages to set transaction fees. Wallets should rather use fee
> estimation
>   to determine transaction fees and set replace-by-fee if desired. Thus,
> they
>   could wait until the transaction has confirmed (taking into account the
> fee
>   target they set (compare the RPC `estimatesmartfee`)) or listen for the
>   transaction announcement by other network peers to check for propagation.
>
> I propose to remove "reject" messages from Bitcoin Core 0.19.0 unless
> there are
> valid concerns about its removal.
>
> Marco
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