From 921c7f301f4e8d9c320cb1a41d5a03d1b7ec5f93 Mon Sep 17 00:00:00 2001
From: josie <josibake@protonmail.com>
Date: Wed, 3 Jun 2026 13:14:15 +0200
Subject: [PATCH] relay broadcast transactions to peers

subscribe the outbound transaction protocol to locally broadcast
transaction messages and announce them through the existing inv path.

the handler preserves the existing was_announced/null-hash behavior and
avoids echoing a transaction back to the channel that originated the
broadcast.

added to support broadcast from sparrow wallet; discovered while testing
the silent payments index PRs.
---
 .../protocol_transaction_out_106.hpp          |  6 ++++
 .../protocol_transaction_out_106.cpp          | 28 +++++++++++++++++--
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/include/bitcoin/node/protocols/protocol_transaction_out_106.hpp b/include/bitcoin/node/protocols/protocol_transaction_out_106.hpp
index 16113766..c9c25fba 100644
--- a/include/bitcoin/node/protocols/protocol_transaction_out_106.hpp
+++ b/include/bitcoin/node/protocols/protocol_transaction_out_106.hpp
@@ -54,11 +54,17 @@ class BCN_API protocol_transaction_out_106
     /// Process tx announcement.
     virtual bool do_announce(transaction_t link) NOEXCEPT;
 
+    virtual bool handle_broadcast_transaction(const code& ec,
+        const network::messages::peer::transaction::cptr& message,
+        uint64_t sender) NOEXCEPT;
+
     virtual bool handle_receive_get_data(const code& ec,
         const network::messages::peer::get_data::cptr& message) NOEXCEPT;
     virtual void send_transaction(const code& ec, size_t index,
         const network::messages::peer::get_data::cptr& message) NOEXCEPT;
 
+    virtual bool announce(const system::hash_digest& hash) NOEXCEPT;
+
 private:
     // These are thread safe.
     const bool node_witness_;
diff --git a/src/protocols/protocol_transaction_out_106.cpp b/src/protocols/protocol_transaction_out_106.cpp
index 6ca35a72..67733f7a 100644
--- a/src/protocols/protocol_transaction_out_106.cpp
+++ b/src/protocols/protocol_transaction_out_106.cpp
@@ -45,6 +45,7 @@ void protocol_transaction_out_106::start() NOEXCEPT
 
     // Events subscription is asynchronous, events may be missed.
     subscribe_chase(BIND(handle_chase, _1, _2, _3));
+    SUBSCRIBE_BROADCAST(transaction, handle_broadcast_transaction, _1, _2, _3);
     SUBSCRIBE_CHANNEL(get_data, handle_receive_get_data, _1, _2);
     protocol_peer::start();
 }
@@ -54,6 +55,7 @@ void protocol_transaction_out_106::stopping(const code& ec) NOEXCEPT
     // Unsubscriber race is ok.
     BC_ASSERT(stranded());
     unsubscribe_chase();
+    UNSUBSCRIBE_BROADCAST();
     protocol_peer::stopping(ec);
 }
 
@@ -98,8 +100,30 @@ bool protocol_transaction_out_106::do_announce(transaction_t link) NOEXCEPT
     if (stopped())
         return false;
 
-    // Don't announce to peer that announced to us.
-    const auto hash = query.get_tx_key(link);
+    return announce(query.get_tx_key(link));
+}
+
+bool protocol_transaction_out_106::handle_broadcast_transaction(const code& ec,
+    const transaction::cptr& message, uint64_t sender) NOEXCEPT
+{
+    BC_ASSERT(stranded());
+
+    if (stopped(ec))
+        return false;
+
+    if (sender == identifier())
+        return true;
+
+    if (!message || !message->transaction_ptr)
+        return true;
+
+    return announce(message->transaction_ptr->hash(false));
+}
+
+bool protocol_transaction_out_106::announce(const hash_digest& hash) NOEXCEPT
+{
+    BC_ASSERT(stranded());
+
     if (was_announced(hash))
         return true;