Add bip-halt-unrequested-txn-processing

bip-halt-unrequested-txn-processing.mediawiki

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+<pre>
+  BIP: YYY
+  Layer: Peer Services
+  Title: Unrequested Transactions Processing
+  Author: Antoine Riard <btc@ariard.me>
+  Comments-Summary: No comments yet.
+  Comments-URI: https://github.com/bitcoin/bips/wiki/Comments:BIP-0XXX
+  Status: Draft
+  Type: Standards Track
+  Created: 2024-09-05
+  License: GPLv2
+</pre>
+
+==Abstract==
+
+This BIP proposes a new mechanism to halt the processing of unrequested transations
+received by a node from its bitcoin networks peers.
+
+==Motivation==
+
+Historically, nodes have been exchanging transactions on the Bitcoin peer-to-peer
+network by sending an inv, and if the transaction has not been discovered and processed
+yet by the other peer, sending a dedicated tx message.
+
+Sending an unnannounced tx message has always been considered in conformity with
+the protocol, however this behavior creates a denanonymization vector if leveraged
+by mass connectors.
+
+We can eliminate this concern by nodes rejecting unrequested transactions.
+
+==Specification==
+
+TODO: segment the protocol version by sub-categories of traffic class (eg tx, addr, block ?)
+
+#. The protocol version of nodes implementing this BIP must be set to 70017 or higher.
+
+#. After a node received a transaction from a peer
+## If this transaction has been previously fetch with a getdata request, the node MUST process the transaction
+## If this transaction has not been previously fetch with a getdata request, the node SHOULD reject the transaction
+
+TODO: add a policy rule to disconnect protocol violation ?
+
+==Backward compatibility==
+
+This mechanism only applies to network peers signaling NODE_TXRELAY_V2 as a node service bit.
+
+==Implementation==
+
+https://github.com/bitcoin/bitcoin/pull/30572
+
+==Copyright==
+
+This BIP is licensed under the GPLv2.