Merge #19464: net: remove -banscore configuration option

06059b0c2a6c2db70c87a7715f8a344a13400fa1 net: rename DEFAULT_BANSCORE_THRESHOLD to DISCOURAGEMENT_THRESHOLD (Jon Atack)
1d4024bca8086cceff7539dd8c15e0b7fe1cc5ea net: remove -banscore configuration option (Jon Atack)

Pull request description:

  per https://github.com/bitcoin/bitcoin/pull/19219#issuecomment-652684340, https://github.com/bitcoin/bitcoin/pull/19219#discussion_r443074487 and https://github.com/bitcoin/bitcoin/pull/19219#issuecomment-652699592. Edit: now split into 3 straightforward PRs:
  - net: remove -banscore configuration option (this PR)
  - rpc: deprecate banscore field in getpeerinfo (#19469, *merged*)
  - gui: no longer display banscores (TBA in the gui repo)

ACKs for top commit:
  MarcoFalke:
    review ACK 06059b0c2a6c2db70c87a7715f8a344a13400fa1 📙
  vasild:
    ACK 06059b0c

Tree-SHA512: 03fad249986e0896697033fbb8ba2cbfaae7d7603b1fb2a38b3d41db697630d238623f4d732b9098c82af249ce5a1767dd432b7ca0fec10544e23d24fbd57c50

7 files changed, 17 insertions, 15 deletions

diff --git a/doc/release-notes.md b/doc/release-notes.md
index 2966f9083c..2a2e0f9472 100644
--- a/doc/release-notes.md
+++ b/doc/release-notes.md
@@ -121,6 +121,11 @@ Build System
 Updated settings
 ----------------
 
+- The `-banscore` configuration option, which modified the default threshold for
+  disconnecting and discouraging misbehaving peers, has been removed as part of
+  changes in this release to the handling of misbehaving peers. Refer to the
+  section, "Changes regarding misbehaving peers", for details. (#19464)
+
 - The `-debug=db` logging category, which was deprecated in 0.20 and replaced by
   `-debug=walletdb` to distinguish it from `coindb`, has been removed. (#19202)
 
diff --git a/src/init.cpp b/src/init.cpp
index 16f765574f..7b893a08d7 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -431,7 +431,6 @@ void SetupServerArgs(NodeContext& node)
 
     gArgs.AddArg("-addnode=<ip>", "Add a node to connect to and attempt to keep the connection open (see the `addnode` RPC command help for more info). This option can be specified multiple times to add multiple nodes.", ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::CONNECTION);
     gArgs.AddArg("-asmap=<file>", strprintf("Specify asn mapping used for bucketing of the peers (default: %s). Relative paths will be prefixed by the net-specific datadir location.", DEFAULT_ASMAP_FILENAME), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
-    gArgs.AddArg("-banscore=<n>", strprintf("Threshold for disconnecting and discouraging misbehaving peers (default: %u)", DEFAULT_BANSCORE_THRESHOLD), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     gArgs.AddArg("-bantime=<n>", strprintf("Default duration (in seconds) of manually configured bans (default: %u)", DEFAULT_MISBEHAVING_BANTIME), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     gArgs.AddArg("-bind=<addr>", "Bind to given address and always listen on it. Use [host]:port notation for IPv6", ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::CONNECTION);
     gArgs.AddArg("-connect=<ip>", "Connect only to the specified node; -noconnect disables automatic connections (the rules for this peer are the same as for -addnode). This option can be specified multiple times to connect to multiple nodes.", ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::CONNECTION);
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 1fb6accb82..ad349cf1a7 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -1031,7 +1031,8 @@ unsigned int LimitOrphanTxSize(unsigned int nMaxOrphans)
 }
 
 /**
- * Increment peer's misbehavior score. If the new value surpasses banscore (specified on startup or by default), mark node to be discouraged, meaning the peer might be disconnected & added to the discouragement filter.
+ * Increment peer's misbehavior score. If the new value >= DISCOURAGEMENT_THRESHOLD, mark the node
+ * to be discouraged, meaning the peer might be disconnected and added to the discouragement filter.
  */
 void Misbehaving(NodeId pnode, int howmuch, const std::string& message) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
 {
@@ -1043,9 +1044,8 @@ void Misbehaving(NodeId pnode, int howmuch, const std::string& message) EXCLUSIV
         return;
 
     state->nMisbehavior += howmuch;
-    int banscore = gArgs.GetArg("-banscore", DEFAULT_BANSCORE_THRESHOLD);
     std::string message_prefixed = message.empty() ? "" : (": " + message);
-    if (state->nMisbehavior >= banscore && state->nMisbehavior - howmuch < banscore)
+    if (state->nMisbehavior >= DISCOURAGEMENT_THRESHOLD && state->nMisbehavior - howmuch < DISCOURAGEMENT_THRESHOLD)
     {
         LogPrint(BCLog::NET, "%s: %s peer=%d (%d -> %d) DISCOURAGE THRESHOLD EXCEEDED%s\n", __func__, state->name, pnode, state->nMisbehavior-howmuch, state->nMisbehavior, message_prefixed);
         state->m_should_discourage = true;
diff --git a/src/net_processing.h b/src/net_processing.h
index eadf29e59f..3479ef6865 100644
--- a/src/net_processing.h
+++ b/src/net_processing.h
@@ -23,6 +23,8 @@ static const unsigned int DEFAULT_MAX_ORPHAN_TRANSACTIONS = 100;
 static const unsigned int DEFAULT_BLOCK_RECONSTRUCTION_EXTRA_TXN = 100;
 static const bool DEFAULT_PEERBLOOMFILTERS = false;
 static const bool DEFAULT_PEERBLOCKFILTERS = false;
+/** Threshold for marking a node to be discouraged, e.g. disconnected and added to the discouragement filter. */
+static const int DISCOURAGEMENT_THRESHOLD{100};
 
 class PeerLogicValidation final : public CValidationInterface, public NetEventsInterface {
 private:
diff --git a/src/test/denialofservice_tests.cpp b/src/test/denialofservice_tests.cpp
index 1fe01fae04..3d84fa855f 100644
--- a/src/test/denialofservice_tests.cpp
+++ b/src/test/denialofservice_tests.cpp
@@ -232,14 +232,14 @@ BOOST_AUTO_TEST_CASE(DoS_banning)
     dummyNode1.fSuccessfullyConnected = true;
     {
         LOCK(cs_main);
-        Misbehaving(dummyNode1.GetId(), 100); // Should get banned
+        Misbehaving(dummyNode1.GetId(), DISCOURAGEMENT_THRESHOLD); // Should be discouraged
     }
     {
         LOCK2(cs_main, dummyNode1.cs_sendProcessing);
         BOOST_CHECK(peerLogic->SendMessages(&dummyNode1));
     }
     BOOST_CHECK(banman->IsDiscouraged(addr1));
-    BOOST_CHECK(!banman->IsDiscouraged(ip(0xa0b0c001|0x0000ff00))); // Different IP, not banned
+    BOOST_CHECK(!banman->IsDiscouraged(ip(0xa0b0c001|0x0000ff00))); // Different IP, not discouraged
 
     CAddress addr2(ip(0xa0b0c002), NODE_NONE);
     CNode dummyNode2(id++, NODE_NETWORK, 0, INVALID_SOCKET, addr2, 1, 1, CAddress(), "", true);
@@ -255,7 +255,7 @@ BOOST_AUTO_TEST_CASE(DoS_banning)
         LOCK2(cs_main, dummyNode2.cs_sendProcessing);
         BOOST_CHECK(peerLogic->SendMessages(&dummyNode2));
     }
-    BOOST_CHECK(!banman->IsDiscouraged(addr2)); // 2 not banned yet...
+    BOOST_CHECK(!banman->IsDiscouraged(addr2)); // 2 not discouraged yet...
     BOOST_CHECK(banman->IsDiscouraged(addr1));  // ... but 1 still should be
     {
         LOCK(cs_main);
@@ -279,7 +279,6 @@ BOOST_AUTO_TEST_CASE(DoS_banscore)
     auto peerLogic = MakeUnique<PeerLogicValidation>(connman.get(), banman.get(), *m_node.scheduler, *m_node.chainman, *m_node.mempool);
 
     banman->ClearBanned();
-    gArgs.ForceSetArg("-banscore", "111"); // because 11 is my favorite number
     CAddress addr1(ip(0xa0b0c001), NODE_NONE);
     CNode dummyNode1(id++, NODE_NETWORK, 0, INVALID_SOCKET, addr1, 3, 1, CAddress(), "", true);
     dummyNode1.SetSendVersion(PROTOCOL_VERSION);
@@ -288,7 +287,7 @@ BOOST_AUTO_TEST_CASE(DoS_banscore)
     dummyNode1.fSuccessfullyConnected = true;
     {
         LOCK(cs_main);
-        Misbehaving(dummyNode1.GetId(), 100);
+        Misbehaving(dummyNode1.GetId(), DISCOURAGEMENT_THRESHOLD - 11);
     }
     {
         LOCK2(cs_main, dummyNode1.cs_sendProcessing);
@@ -313,7 +312,6 @@ BOOST_AUTO_TEST_CASE(DoS_banscore)
         BOOST_CHECK(peerLogic->SendMessages(&dummyNode1));
     }
     BOOST_CHECK(banman->IsDiscouraged(addr1));
-    gArgs.ForceSetArg("-banscore", ToString(DEFAULT_BANSCORE_THRESHOLD));
 
     bool dummy;
     peerLogic->FinalizeNode(dummyNode1.GetId(), dummy);
@@ -338,7 +336,7 @@ BOOST_AUTO_TEST_CASE(DoS_bantime)
 
     {
         LOCK(cs_main);
-        Misbehaving(dummyNode.GetId(), 100);
+        Misbehaving(dummyNode.GetId(), DISCOURAGEMENT_THRESHOLD);
     }
     {
         LOCK2(cs_main, dummyNode.cs_sendProcessing);
diff --git a/src/validation.h b/src/validation.h
index 9b49627135..acadf151c5 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -74,7 +74,6 @@ static const int64_t DEFAULT_MAX_TIP_AGE = 24 * 60 * 60;
 static const bool DEFAULT_CHECKPOINTS_ENABLED = true;
 static const bool DEFAULT_TXINDEX = false;
 static const char* const DEFAULT_BLOCKFILTERINDEX = "0";
-static const unsigned int DEFAULT_BANSCORE_THRESHOLD = 100;
 /** Default for -persistmempool */
 static const bool DEFAULT_PERSIST_MEMPOOL = true;
 /** Default for using fee filter */
diff --git a/test/functional/p2p_leak.py b/test/functional/p2p_leak.py
index 3b3dbd08f2..6cf252e626 100755
--- a/test/functional/p2p_leak.py
+++ b/test/functional/p2p_leak.py
@@ -26,7 +26,7 @@ from test_framework.util import (
     wait_until,
 )
 
-banscore = 10
+DISCOURAGEMENT_THRESHOLD = 100
 
 
 class CLazyNode(P2PInterface):
@@ -70,7 +70,7 @@ class CNodeNoVersionBan(CLazyNode):
     # NOTE: implementation-specific check here. Remove if bitcoind ban behavior changes
     def on_open(self):
         super().on_open()
-        for i in range(banscore):
+        for _ in range(DISCOURAGEMENT_THRESHOLD):
             self.send_message(msg_verack())
 
 # Node that never sends a version. This one just sits idle and hopes to receive
@@ -106,7 +106,6 @@ class P2PVersionStore(P2PInterface):
 class P2PLeakTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 1
-        self.extra_args = [['-banscore=' + str(banscore)]]
 
     def run_test(self):
         no_version_bannode = self.nodes[0].add_p2p_connection(CNodeNoVersionBan(), send_version=False, wait_for_verack=False)