MIME-Version: 1.0
From: Antoine Riard <antoine.riard@gmail.com>
Date: Wed, 10 Feb 2021 08:13:34 -0500
Message-ID: <CALZpt+E6UqB5cew145PO2qiEMsELJ-TuGyE5PBL04T1tESiOiQ@mail.gmail.com>
To: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Content-Type: multipart/alternative; boundary="0000000000003cc08005bafb2c86"
Subject: [bitcoin-dev] Proposal to stop processing of unrequested
	transactions in Bitcoin Core
Precedence: list

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Hi,

I'm proposing to stop the processing of unrequested transactions in Bitcoin
Core 22.0+ at TX message reception. An unrequested transaction is one
defined by which a "getdata" message for its specific identifier (either
txid or wtxid) has not been previously issued by the node [0].

This change is motivated by reducing the CPU DoS surface of Bitcoin Core
around mempool acceptance. Currently, an attacker can open multiple inbound
connections to a node and send expensive to validate, junk transactions.
Once the canonical INV/GETDATA sequence is enforced on the network, a
further protection would be to deprioritize bandwidth and validation
resources allocation, or even to wither connections with such DoSy peers. A
permissioned peer (PF_RELAY) will still be able to bypass such restrictions.

Raw TX message processing has always been tolerated by Core and as such
some Bitcoin clients aren't bothering with an INV/GETDATA sequence. Such
change will break their tx-relay capabilities on the p2p network and
require adaptation from them. Given deployment time of any release, I hope
it provides a window time wide enough before the old tx-processing behavior
becomes the minority.

Eager to gather feedback on this proposal, especially if such change is
deemed as too much constraining or fast on any Bitcoin software.

Cheers,
Antoine

[0] See https://github.com/bitcoin/bitcoin/pull/20277

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<div dir=3D"ltr"><div>Hi,<br><br>I&#39;m proposing to stop the processing o=
f unrequested transactions in Bitcoin Core 22.0+ at TX message reception. A=
n unrequested transaction is one defined by which a &quot;getdata&quot; mes=
sage for its specific identifier (either txid or wtxid) has not been previo=
usly issued by the node [0].<br><br>This change is motivated by reducing th=
e CPU DoS surface of Bitcoin Core around mempool acceptance. Currently, an =
attacker can open multiple inbound connections to a node and send expensive=
 to validate, junk transactions. Once the canonical INV/GETDATA sequence is=
 enforced on the network, a further protection would be to deprioritize ban=
dwidth and validation resources allocation, or even to wither connections w=
ith such DoSy peers. A permissioned peer (PF_RELAY) will still be able to b=
ypass such restrictions.<br><br>Raw TX message processing has always been t=
olerated by Core and as such some Bitcoin clients aren&#39;t bothering with=
 an INV/GETDATA sequence. Such change will break their tx-relay capabilitie=
s on the p2p network and require adaptation from them. Given deployment tim=
e of any release, I hope it provides a window time wide enough before the o=
ld tx-processing behavior becomes the minority.<br><br>Eager to gather feed=
back on this proposal, especially if such change is deemed as too much cons=
training or fast on any Bitcoin software.<br><br>Cheers,<br>Antoine<br><br>=
[0] See <a href=3D"https://github.com/bitcoin/bitcoin/pull/20277">https://g=
ithub.com/bitcoin/bitcoin/pull/20277</a><br></div></div>

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