Merge #7240: fix: initialize quorum connections on startup

5a43003 test: verify post-restart IS lock on all nodes, not just sender (UdjinM6)
ecd5c90 refactor: defer active_ctx block tip init until after nodeman->Init() (UdjinM6)
c25c61a test: add InstantSend after full restart test (UdjinM6)
5e79dbe fix: initialize quorum connections at startup on idle chains (UdjinM6)

Pull request description:

  ## Issue being fixed or feature implemented
  After PR dashpay/dash#7063 (commit dashpay/dash@1360d9d), `CQuorumManager::UpdatedBlockTip` was moved from `CDSNotificationInterface::UpdatedBlockTip` (which is called directly at startup via `InitializeCurrentBlockTip`) to the `ActiveContext`/`ObserverContext` `CValidationInterface` subscribers. These subscribers only receive `UpdatedBlockTip` via `GetMainSignals()` broadcast, which is never triggered at startup on idle chains — `ActivateBestChain` early-returns when `pindexMostWork == m_chain.Tip()`.

  This means that after a full restart with no new blocks:
  - `QuorumObserver::UpdatedBlockTip` never fires
  - `CheckQuorumConnections` is never called
  - Quorum connections are never re-established
  - MNs cannot exchange signing shares
  - InstantSend and ChainLock signing fails

  ## What was done?
  Fix by adding `InitializeCurrentBlockTip()` to `ActiveContext` and `ObserverContext`, called from the `loadblk` thread right after `CDSNotificationInterface::InitializeCurrentBlockTip()`. This method also calls the new `QuorumObserver::InitializeQuorumConnections()`, which bypasses the `IsBlockchainSynced()` guard (mnsync is not yet complete at that point in the startup sequence).

  ## How Has This Been Tested?
  See new "IS after MNs restart" test which fails on develop and passes with the patch applied

  ## Breaking Changes
  n/a

  ## Checklist:
  - [ ] I have performed a self-review of my own code
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have added or updated relevant unit/integration/functional/e2e tests
  - [ ] I have made corresponding changes to the documentation
  - [ ] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

ACKs for top commit:
  PastaPastaPasta:
    utACK 5a43003
  knst:
    utACK 5a43003

Tree-SHA512: 3c91e7cde81d9359e0b55a501eb230a9abcc80212da5050d10d73f23cab076a36bd0f2bd10b2bab3015cd7f64d4156429a03247381e1b96f424b7cd75205a662

Author: PastaPastaPasta

src/active/context.cpp

@@ -97,6 +97,14 @@ void ActiveContext::SetCJServer(gsl::not_null<CCoinJoinServer*> cj_server)
     m_cj_server = cj_server;
 }
 
+void ActiveContext::InitializeCurrentBlockTip(const CBlockIndex* tip, bool ibd)
+{
+    UpdatedBlockTip(tip, nullptr, ibd);
+    if (tip) {
+        qman_handler->InitializeQuorumConnections(tip);
+    }
+}
+
 void ActiveContext::UpdatedBlockTip(const CBlockIndex* pindexNew, const CBlockIndex* pindexFork, bool fInitialDownload)
 {
     if (fInitialDownload || pindexNew == pindexFork) // In IBD or blocks were disconnected without any new ones

src/active/context.h

@@ -74,6 +74,7 @@ struct ActiveContext final : public CValidationInterface {
 
     void Start(CConnman& connman, PeerManager& peerman, int16_t worker_count);
     void Stop();
+    void InitializeCurrentBlockTip(const CBlockIndex* tip, bool ibd);
 
     CCoinJoinServer& GetCJServer() const;
     void SetCJServer(gsl::not_null<CCoinJoinServer*> cj_server);

src/init.cpp

@@ -2417,6 +2417,15 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         // but don't call it directly to prevent triggering of other listeners like zmq etc.
         // GetMainSignals().UpdatedBlockTip(::ChainActive().Tip());
         g_ds_notification_interface->InitializeCurrentBlockTip();
+        {
+            const CBlockIndex* tip = WITH_LOCK(::cs_main, return chainman.ActiveTip());
+            const bool ibd = chainman.ActiveChainstate().IsInitialBlockDownload();
+            if (node.observer_ctx && !node.active_ctx) {
+                node.observer_ctx->InitializeCurrentBlockTip(tip, ibd);
+            }
+            // Note: active_ctx initialization is deferred until after nodeman->Init()
+            // so that GetProTxHash() is available for quorum connection setup.
+        }
 
         {
             // Get all UTXOs for each MN collateral in one go so that we can fill coin cache early
@@ -2481,6 +2490,13 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
 
         if (node.active_ctx) {
             node.active_ctx->nodeman->Init(chainman.ActiveTip());
+            // Initialize current block tip after nodeman->Init() so that
+            // GetProTxHash() is available for quorum connection setup.
+            // Without this ordering, EnsureQuorumConnections returns early
+            // because the null proTxHash makes the MN appear as a non-member.
+            const CBlockIndex* tip = WITH_LOCK(::cs_main, return chainman.ActiveTip());
+            const bool ibd = chainman.ActiveChainstate().IsInitialBlockDownload();
+            node.active_ctx->InitializeCurrentBlockTip(tip, ibd);
         }
     });
 #ifdef ENABLE_WALLET

src/llmq/observer/context.cpp

@@ -47,6 +47,14 @@ void ObserverContext::Stop()
     qman_handler->Stop();
 }
 
+void ObserverContext::InitializeCurrentBlockTip(const CBlockIndex* tip, bool ibd)
+{
+    UpdatedBlockTip(tip, nullptr, ibd);
+    if (tip) {
+        qman_handler->InitializeQuorumConnections(tip);
+    }
+}
+
 void ObserverContext::UpdatedBlockTip(const CBlockIndex* pindexNew, const CBlockIndex* pindexFork, bool fInitialDownload)
 {
     if (fInitialDownload || pindexNew == pindexFork) // In IBD or blocks were disconnected without any new ones

src/llmq/observer/context.h

@@ -49,6 +49,7 @@ struct ObserverContext final : public CValidationInterface {
 
     void Start(int16_t worker_count);
     void Stop();
+    void InitializeCurrentBlockTip(const CBlockIndex* tip, bool ibd);
 
 protected:
     // CValidationInterface

src/llmq/observer/quorums.cpp

@@ -59,6 +59,13 @@ void QuorumObserver::Stop()
     workerPool.stop(true);
 }
 
+void QuorumObserver::InitializeQuorumConnections(gsl::not_null<const CBlockIndex*> pindexNew) const
+{
+    for (const auto& params : Params().GetConsensus().llmqs) {
+        CheckQuorumConnections(params, pindexNew);
+    }
+}
+
 void QuorumObserver::UpdatedBlockTip(const CBlockIndex* pindexNew, bool fInitialDownload) const
 {
     if (!pindexNew) return;

src/llmq/observer/quorums.h

@@ -96,6 +96,7 @@ class QuorumObserver
     void Stop();
 
     void UpdatedBlockTip(const CBlockIndex* pindexNew, bool fInitialDownload) const;
+    void InitializeQuorumConnections(gsl::not_null<const CBlockIndex*> pindexNew) const;
 
 public:
     virtual bool SetQuorumSecretKeyShare(CQuorum& quorum, Span<CBLSSecretKey> skContributions) const;

test/functional/p2p_instantsend.py

@@ -4,7 +4,7 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 from test_framework.test_framework import DashTestFramework
-from test_framework.util import assert_equal, assert_raises_rpc_error
+from test_framework.util import assert_equal, assert_raises_rpc_error, force_finish_mnsync
 
 '''
 p2p_instantsend.py
@@ -36,6 +36,7 @@ def run_test(self):
 
         self.test_mempool_doublespend()
         self.test_block_doublespend()
+        self.test_instantsend_after_restart()
 
     def test_block_doublespend(self):
         sender = self.nodes[self.sender_idx]
@@ -143,5 +144,85 @@ def test_mempool_doublespend(self):
         # mine more blocks
         self.generate(self.nodes[0], 2)
 
+    def test_instantsend_after_restart(self):
+        self.log.info("Testing InstantSend works after full restart without new blocks")
+
+        # fund sender with confirmed coins
+        sender = self.nodes[self.sender_idx]
+        receiver = self.nodes[self.receiver_idx]
+        sender_addr = sender.getnewaddress()
+        fund_id = self.nodes[0].sendtoaddress(sender_addr, 1)
+        self.bump_mocktime(30)
+        self.sync_mempools()
+        for node in self.nodes:
+            self.wait_for_instantlock(fund_id, node)
+        tip = self.generate(self.nodes[0], 2)[-1]
+        self.bump_mocktime(30)
+        self.wait_for_chainlocked_block_all_nodes(tip)
+        self.sync_blocks()
+        assert sender.getbalance() >= 0.5
+
+        receiver_addr = receiver.getnewaddress()
+
+        # restart all nodes without mining new blocks
+        self.log.info("Restarting all nodes")
+        num_simple_nodes = self.num_nodes - self.mn_count
+        self.stop_nodes()
+
+        for i in range(num_simple_nodes):
+            self.start_node(i)
+        for mn_info in self.mninfo:
+            self.start_masternode(mn_info)
+
+        # reconnect: simple nodes to node 0, MNs to node 0 only.
+        # Quorum connections between MNs must be re-established automatically
+        # via InitializeCurrentBlockTip → EnsureQuorumConnections, NOT via
+        # manual connect_nodes between MN pairs.
+        for i in range(1, num_simple_nodes):
+            self.connect_nodes(i, 0)
+        for mn_info in self.mninfo:
+            self.connect_nodes(mn_info.nodeIdx, 0)
+        for i in range(num_simple_nodes):
+            force_finish_mnsync(self.nodes[i])
+
+        # bump past WAIT_FOR_ISLOCK_TIMEOUT so txFirstSeenTime loss doesn't
+        # block chainlock signing for TXs mined before restart
+        self.bump_mocktime(10 * 60 + 1)
+        self.sync_blocks()
+
+        # Verify that MNs formed quorum connections to other MNs after restart.
+        # InitializeCurrentBlockTip → EnsureQuorumConnections must populate
+        # masternodeQuorumNodes so ThreadOpenMasternodeConnections establishes
+        # MN-to-MN links beyond the manual connections to node 0.
+        self.log.info("Verifying MN-to-MN quorum connections formed after restart")
+        for mn_info in self.mninfo:
+            mn_node = self.nodes[mn_info.nodeIdx]
+
+            def check_mn_peers(node=mn_node, my_hash=mn_info.proTxHash):
+                peers = node.getpeerinfo()
+                mn_peers = set(p['verified_proregtx_hash'] for p in peers
+                               if p.get('verified_proregtx_hash', '') != '')
+                other_mn_peers = mn_peers - {my_hash}
+                return len(other_mn_peers) > 0
+            self.wait_until(check_mn_peers, timeout=30)
+
+        # re-grab references after restart
+        sender = self.nodes[self.sender_idx]
+        receiver = self.nodes[self.receiver_idx]
+
+        # send a TX — needs IS lock from all restarted MNs, no new blocks mined
+        is_id = sender.sendtoaddress(receiver_addr, 0.5)
+        self.bump_mocktime(30)
+        self.sync_mempools()
+        for node in self.nodes:
+            self.wait_for_instantlock(is_id, node)
+        self.log.info("InstantSend lock succeeded after full restart")
+
+        # clean up
+        receiver.sendtoaddress(self.nodes[0].getnewaddress(), 0.5, "", "", True)
+        self.bump_mocktime(30)
+        self.sync_mempools()
+        self.generate(self.nodes[0], 2)
+
 if __name__ == '__main__':
     InstantSendTest().main()