Merge #11560: Connect to a new outbound peer if our tip is stale

6262915 Add unit test for stale tip checking (Suhas Daftuar)
83df257 Add CConnmanTest to mutate g_connman in tests (João Barbosa)
ac7b37c Connect to an extra outbound peer if our tip is stale (Suhas Daftuar)
db32a65 Track tip update time and last new block announcement from each peer (Suhas Daftuar)
2d4327d net: Allow connecting to extra outbound peers (Suhas Daftuar)

Pull request description:

  This is an alternative approach to #11534.  Rather than disconnect an outbound peer when our tip looks stale, instead try to connect to an additional outbound peer.

  Periodically, check to see if we have more outbound peers than we target (ie if any extra peers are in use), and if so, disconnect the one that least recently announced a new block (breaking ties by choosing the newest peer that we connected to).

Tree-SHA512: 8f19e910e0bb36867f81783e020af225f356451899adfc7ade1895d6d3bd5afe51c83759610dfd10c62090c4fe404efa0283b2f63fde0bd7da898a1aaa7fb281

1 files changed, 85 insertions, 0 deletions

diff --git a/src/test/DoS_tests.cpp b/src/test/DoS_tests.cpp
index 7bcf304833..d1f9e63ecf 100644
--- a/src/test/DoS_tests.cpp
+++ b/src/test/DoS_tests.cpp
@@ -40,6 +40,8 @@ CService ip(uint32_t i)
 
 static NodeId id = 0;
 
+void UpdateLastBlockAnnounceTime(NodeId node, int64_t time_in_seconds);
+
 BOOST_FIXTURE_TEST_SUITE(DoS_tests, TestingSetup)
 
 // Test eviction of an outbound peer whose chain never advances
@@ -87,6 +89,89 @@ BOOST_AUTO_TEST_CASE(outbound_slow_chain_eviction)
     peerLogic->FinalizeNode(dummyNode1.GetId(), dummy);
 }
 
+void AddRandomOutboundPeer(std::vector<CNode *> &vNodes, PeerLogicValidation &peerLogic)
+{
+    CAddress addr(ip(GetRandInt(0xffffffff)), NODE_NONE);
+    vNodes.emplace_back(new CNode(id++, ServiceFlags(NODE_NETWORK|NODE_WITNESS), 0, INVALID_SOCKET, addr, 0, 0, CAddress(), "", /*fInboundIn=*/ false));
+    CNode &node = *vNodes.back();
+    node.SetSendVersion(PROTOCOL_VERSION);
+
+    peerLogic.InitializeNode(&node);
+    node.nVersion = 1;
+    node.fSuccessfullyConnected = true;
+
+    CConnmanTest::AddNode(node);
+}
+
+BOOST_AUTO_TEST_CASE(stale_tip_peer_management)
+{
+    const Consensus::Params& consensusParams = Params().GetConsensus();
+    constexpr int nMaxOutbound = 8;
+    CConnman::Options options;
+    options.nMaxConnections = 125;
+    options.nMaxOutbound = nMaxOutbound;
+    options.nMaxFeeler = 1;
+
+    connman->Init(options);
+    std::vector<CNode *> vNodes;
+
+    // Mock some outbound peers
+    for (int i=0; i<nMaxOutbound; ++i) {
+        AddRandomOutboundPeer(vNodes, *peerLogic);
+    }
+
+    peerLogic->CheckForStaleTipAndEvictPeers(consensusParams);
+
+    // No nodes should be marked for disconnection while we have no extra peers
+    for (const CNode *node : vNodes) {
+        BOOST_CHECK(node->fDisconnect == false);
+    }
+
+    SetMockTime(GetTime() + 3*consensusParams.nPowTargetSpacing + 1);
+
+    // Now tip should definitely be stale, and we should look for an extra
+    // outbound peer
+    peerLogic->CheckForStaleTipAndEvictPeers(consensusParams);
+    BOOST_CHECK(connman->GetTryNewOutboundPeer());
+
+    // Still no peers should be marked for disconnection
+    for (const CNode *node : vNodes) {
+        BOOST_CHECK(node->fDisconnect == false);
+    }
+
+    // If we add one more peer, something should get marked for eviction
+    // on the next check (since we're mocking the time to be in the future, the
+    // required time connected check should be satisfied).
+    AddRandomOutboundPeer(vNodes, *peerLogic);
+
+    peerLogic->CheckForStaleTipAndEvictPeers(consensusParams);
+    for (int i=0; i<nMaxOutbound; ++i) {
+        BOOST_CHECK(vNodes[i]->fDisconnect == false);
+    }
+    // Last added node should get marked for eviction
+    BOOST_CHECK(vNodes.back()->fDisconnect == true);
+
+    vNodes.back()->fDisconnect = false;
+
+    // Update the last announced block time for the last
+    // peer, and check that the next newest node gets evicted.
+    UpdateLastBlockAnnounceTime(vNodes.back()->GetId(), GetTime());
+
+    peerLogic->CheckForStaleTipAndEvictPeers(consensusParams);
+    for (int i=0; i<nMaxOutbound-1; ++i) {
+        BOOST_CHECK(vNodes[i]->fDisconnect == false);
+    }
+    BOOST_CHECK(vNodes[nMaxOutbound-1]->fDisconnect == true);
+    BOOST_CHECK(vNodes.back()->fDisconnect == false);
+
+    bool dummy;
+    for (const CNode *node : vNodes) {
+        peerLogic->FinalizeNode(node->GetId(), dummy);
+    }
+
+    CConnmanTest::ClearNodes();
+}
+
 BOOST_AUTO_TEST_CASE(DoS_banning)
 {
     std::atomic<bool> interruptDummy(false);