cryptonote_protocol: prevent duplicate txs in fluff queue

1. Fix duplicate transaction monero-project#9335
2. Add test for cases where there are duplicate transaction in fluff

Co-authored-by: Boog900 <boog900@tutanota.com>

src/cryptonote_protocol/levin_notify.cpp

@@ -396,6 +396,8 @@ namespace levin
         for (auto& connection : connections)
         {
           std::sort(connection.first.begin(), connection.first.end()); // don't leak receive order
+          connection.first.erase(std::unique(connection.first.begin(), connection.first.end()),
+                                  connection.first.end());
           make_payload_send_txs(*zone_->p2p, std::move(connection.first), connection.second, zone_->pad_txs, true);
         }
 

tests/unit_tests/levin.cpp

@@ -2219,6 +2219,63 @@ TEST_F(levin_notify, fluff_multiple)
     }
 }
 
+TEST_F(levin_notify, fluff_with_duplicate)
+{
+    std::shared_ptr<cryptonote::levin::notify> notifier_ptr = make_notifier(0, true, false);
+    auto &notifier = *notifier_ptr;
+
+    for (unsigned count = 0; count < 10; ++count)
+        add_connection(count % 2 == 0);
+
+    {
+        const auto status = notifier.get_status();
+        EXPECT_FALSE(status.has_noise);
+        EXPECT_FALSE(status.connections_filled);
+        EXPECT_TRUE(status.has_outgoing);
+    }
+    notifier.new_out_connection();
+    io_service_.poll();
+
+    std::vector<cryptonote::blobdata> txs(9);
+    txs[0].resize(100, 'e');
+    txs[1].resize(100, 'e');
+    txs[2].resize(100, 'e');
+    txs[3].resize(100, 'e');
+    txs[4].resize(200, 'f');
+    txs[5].resize(200, 'f');
+    txs[6].resize(200, 'f');
+    txs[7].resize(200, 'f');
+    txs[8].resize(200, 'f');
+
+    ASSERT_EQ(10u, contexts_.size());
+    {
+        auto context = contexts_.begin();
+        EXPECT_TRUE(notifier.send_txs(txs, context->get_id(), cryptonote::relay_method::fluff));
+
+        io_service_.reset();
+        ASSERT_LT(0u, io_service_.poll());
+        notifier.run_fluff();
+        ASSERT_LT(0u, io_service_.poll());
+
+        EXPECT_EQ(0u, context->process_send_queue());
+        for (++context; context != contexts_.end(); ++context)
+            EXPECT_EQ(1u, context->process_send_queue());
+
+        EXPECT_EQ(txs, events_.take_relayed(cryptonote::relay_method::fluff));
+        std::sort(txs.begin(), txs.end());
+        ASSERT_EQ(9u, receiver_.notified_size());
+        for (unsigned count = 0; count < 9; ++count)
+        {
+            auto notification = receiver_.get_notification<cryptonote::NOTIFY_NEW_TRANSACTIONS>().second;
+            EXPECT_NE(txs, notification.txs);
+            EXPECT_EQ(notification.txs.size(), 2);
+            EXPECT_TRUE(notification._.empty());
+            EXPECT_TRUE(notification.dandelionpp_fluff);
+        }
+    }
+
+}
+
 TEST_F(levin_notify, noise)
 {
     for (unsigned count = 0; count < 10; ++count)