Merge #7293: fix: keep sending ISDLOCK invs to non-MN peers with watchquorums

f6bb02d fix: keep sending ISDLOCK invs to non-MN peers that want recsigs (Konstantin Akimov)

Pull request description:

  ## Issue being fixed or feature implemented

  PR #6994 made masternodes skip ISDLOCK inv announcements to any peer with m_wants_recsigs set, on the premise that such peers can reconstruct the ISLOCK from the recsig.

  It works for MN peers but it does not work for quorum observers running with -watchquorums: those nodes also opt in to recsigs via QSENDRECSIGS but they don't have a signer worker running, so they cannot reconstruct an ISDLOCK from a recsig and they still need the inv.

  nodes[0] runs with -watchquorums and had progressively sent QSENDRECSIGS to all four MN peers; by the third call every MN saw nodes[0].m_wants_recsigs=true and skipped the inv to it.

  ## What was done?
  The ISDLOCK is skipped now only on the peer being verified masternode. Move the policy from PushInv (called for every inv type) to the three sites that actually relay MSG_ISDLOCK and have CNode in scope.

  ## How Has This Been Tested?
  Run functional test interface_dash_zmq.py multiple times.
  This PR drops failure rate from 50% to 0.

  ## Breaking Changes
  N/A

  ## Checklist:
  - [x] 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
  - [x] I have assigned this pull request to a milestone

ACKs for top commit:
  PastaPastaPasta:
    utACK f6bb02d

Tree-SHA512: 14be2cfaad6dd0cb359bedca9e65e176b3d52de109f1c9e606892ee284f8079860d01117d538efb19bcf695e5da0cae747f08dcb98c209624ca28d6cf7d1e34d

Author: PastaPastaPasta

src/net_processing.cpp

@@ -1193,6 +1193,16 @@ static uint16_t GetHeadersLimit(const CNode& pfrom, bool compressed)
     return MAX_HEADERS_UNCOMPRESSED_RESULT;
 }
 
+// Returns true when peer is a verified masternode that has opted in to receive recsigs.
+// Such peers participate in the signing flow that populates creatingInstantSendLocks, so
+// they can reconstruct an ISDLOCK locally from the recsig and don't need the ISDLOCK inv.
+// Non-MN peers (e.g. nodes running with -watchquorums) also opt in to recsigs via
+// QSENDRECSIGS but still need ISDLOCK invs because they don't run the signing flow.
+static bool PeerReconstructsISLockFromRecsig(const CNode& pnode, const Peer& peer)
+{
+    return peer.m_wants_recsigs && !pnode.GetVerifiedProRegTxHash().IsNull();
+}
+
 static void PushInv(Peer& peer, const CInv& inv)
 {
     auto inv_relay = peer.GetInvRelay();
@@ -1204,13 +1214,6 @@ static void PushInv(Peer& peer, const CInv& inv)
         return;
     }
 
-    // Skip ISDLOCK inv announcements for peers that want recsigs, as they can reconstruct
-    // the islock from the recsig
-    if (inv.type == MSG_ISDLOCK && peer.m_wants_recsigs) {
-        LogPrint(BCLog::NET, "%s -- skipping ISDLOCK inv (peer wants recsigs): %s peer=%d\n", __func__, inv.ToString(), peer.m_id);
-        return;
-    }
-
     LOCK(inv_relay->m_tx_inventory_mutex);
     if (inv_relay->m_tx_inventory_known_filter.contains(inv.hash)) {
         LogPrint(BCLog::NET, "%s -- skipping known inv: %s peer=%d\n", __func__, inv.ToString(), peer.m_id);
@@ -2541,6 +2544,11 @@ void PeerManagerImpl::RelayInvFiltered(const CInv& inv, const CTransaction& rela
                 return;
             }
         } // LOCK(tx_relay->m_bloom_filter_mutex)
+        if (inv.type == MSG_ISDLOCK && PeerReconstructsISLockFromRecsig(*pnode, *peer)) {
+            LogPrint(BCLog::NET, "%s -- skipping ISDLOCK inv (peer wants recsigs): %s peer=%d\n",
+                     __func__, inv.ToString(), peer->m_id);
+            return;
+        }
         PushInv(*peer, inv);
     });
 }
@@ -2566,6 +2574,11 @@ void PeerManagerImpl::RelayInvFiltered(const CInv& inv, const uint256& relatedTx
                 return;
             }
         } // LOCK(tx_relay->m_bloom_filter_mutex)
+        if (inv.type == MSG_ISDLOCK && PeerReconstructsISLockFromRecsig(*pnode, *peer)) {
+            LogPrint(BCLog::NET, "%s -- skipping ISDLOCK inv (peer wants recsigs): %s peer=%d\n",
+                     __func__, inv.ToString(), peer->m_id);
+            return;
+        }
         PushInv(*peer, inv);
     });
 }
@@ -6348,9 +6361,7 @@ bool PeerManagerImpl::SendMessages(CNode* pto)
                     if (islock == nullptr) continue;
                     uint256 isLockHash{::SerializeHash(*islock)};
                     tx_relay->m_tx_inventory_known_filter.insert(isLockHash);
-                    // Skip ISDLOCK inv announcements for peers that want recsigs, as they can reconstruct
-                    // the islock from the recsig
-                    if (!peer->m_wants_recsigs) {
+                    if (!PeerReconstructsISLockFromRecsig(*pto, *peer)) {
                         queueAndMaybePushInv(CInv(MSG_ISDLOCK, isLockHash));
                     }
                 }