Remove bad chain alert partition check

As per meeting 2016-03-31
https://bitcoincore.org/en/meetings/2016/03/31/#bad-chain-alerts

The partition checker was producing huge number of false-positives
and was disabled in 0.12.1 on the understanding it would either be
fixed in 0.13 or removed entirely from master if not.

src/Makefile.test.include

@@ -38,7 +38,6 @@ BITCOIN_TESTS =\
   test/arith_uint256_tests.cpp \
   test/scriptnum10.h \
   test/addrman_tests.cpp \
-  test/alert_tests.cpp \
   test/amount_tests.cpp \
   test/allocator_tests.cpp \
   test/base32_tests.cpp \

src/init.cpp

@@ -1416,12 +1416,6 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
 
     StartNode(threadGroup, scheduler);
 
-    // Monitor the chain, and alert if we get blocks much quicker or slower than expected
-    int64_t nPowTargetSpacing = Params().GetConsensus().nPowTargetSpacing;
-    CScheduler::Function f = boost::bind(&PartitionCheck, &IsInitialBlockDownload,
-                                         boost::ref(cs_main), boost::cref(pindexBestHeader), nPowTargetSpacing);
-    scheduler.scheduleEvery(f, nPowTargetSpacing);
-
     // ********************************************************* Step 12: finished
 
     SetRPCWarmupFinished();

src/main.cpp

@@ -2118,68 +2118,6 @@ void ThreadScriptCheck() {
     scriptcheckqueue.Thread();
 }
 
-//
-// Called periodically asynchronously; alerts if it smells like
-// we're being fed a bad chain (blocks being generated much
-// too slowly or too quickly).
-//
-void PartitionCheck(bool (*initialDownloadCheck)(), CCriticalSection& cs, const CBlockIndex *const &bestHeader,
-                    int64_t nPowTargetSpacing)
-{
-    if (bestHeader == NULL || initialDownloadCheck()) return;
-
-    static int64_t lastAlertTime = 0;
-    int64_t now = GetAdjustedTime();
-    if (lastAlertTime > now-60*60*24) return; // Alert at most once per day
-
-    const int SPAN_HOURS=4;
-    const int SPAN_SECONDS=SPAN_HOURS*60*60;
-    int BLOCKS_EXPECTED = SPAN_SECONDS / nPowTargetSpacing;
-
-    boost::math::poisson_distribution<double> poisson(BLOCKS_EXPECTED);
-
-    std::string strWarning;
-    int64_t startTime = GetAdjustedTime()-SPAN_SECONDS;
-
-    LOCK(cs);
-    const CBlockIndex* i = bestHeader;
-    int nBlocks = 0;
-    while (i->GetBlockTime() >= startTime) {
-        ++nBlocks;
-        i = i->pprev;
-        if (i == NULL) return; // Ran out of chain, we must not be fully sync'ed
-    }
-
-    // How likely is it to find that many by chance?
-    double p = boost::math::pdf(poisson, nBlocks);
-
-    LogPrint("partitioncheck", "%s: Found %d blocks in the last %d hours\n", __func__, nBlocks, SPAN_HOURS);
-    LogPrint("partitioncheck", "%s: likelihood: %g\n", __func__, p);
-
-    // Aim for one false-positive about every fifty years of normal running:
-    const int FIFTY_YEARS = 50*365*24*60*60;
-    double alertThreshold = 1.0 / (FIFTY_YEARS / SPAN_SECONDS);
-
-    if (p <= alertThreshold && nBlocks < BLOCKS_EXPECTED)
-    {
-        // Many fewer blocks than expected: alert!
-        strWarning = strprintf(_("WARNING: check your network connection, %d blocks received in the last %d hours (%d expected)"),
-                               nBlocks, SPAN_HOURS, BLOCKS_EXPECTED);
-    }
-    else if (p <= alertThreshold && nBlocks > BLOCKS_EXPECTED)
-    {
-        // Many more blocks than expected: alert!
-        strWarning = strprintf(_("WARNING: abnormally high number of blocks generated, %d blocks received in the last %d hours (%d expected)"),
-                               nBlocks, SPAN_HOURS, BLOCKS_EXPECTED);
-    }
-    if (!strWarning.empty())
-    {
-        strMiscWarning = strWarning;
-        AlertNotify(strWarning);
-        lastAlertTime = now;
-    }
-}
-
 // Protected by cs_main
 VersionBitsCache versionbitscache;
 

src/main.h

@@ -242,8 +242,6 @@ bool ProcessMessages(CNode* pfrom);
 bool SendMessages(CNode* pto);
 /** Run an instance of the script checking thread */
 void ThreadScriptCheck();
-/** Try to detect Partition (network isolation) attacks against us */
-void PartitionCheck(bool (*initialDownloadCheck)(), CCriticalSection& cs, const CBlockIndex *const &bestHeader, int64_t nPowTargetSpacing);
 /** Check whether we are doing an initial block download (synchronizing from disk or network) */
 bool IsInitialBlockDownload();
 /** Format a string that describes several potential problems detected by the core.

src/test/alert_tests.cpp

@@ -1,79 +0,0 @@
-// Copyright (c) 2013-2015 The Bitcoin Core developers
-// Distributed under the MIT software license, see the accompanying
-// file COPYING or http://www.opensource.org/licenses/mit-license.php.
-
-// Unit tests for alert system
-
-#include "chainparams.h"
-#include "main.h" // For PartitionCheck
-
-#include "test/testutil.h"
-#include "test/test_bitcoin.h"
-
-#include <boost/test/unit_test.hpp>
-
-BOOST_FIXTURE_TEST_SUITE(Alert_tests, TestingSetup)
-
-
-static bool falseFunc() { return false; }
-
-BOOST_AUTO_TEST_CASE(PartitionAlert)
-{
-    // Test PartitionCheck
-    CCriticalSection csDummy;
-    CBlockIndex indexDummy[100];
-    CChainParams& params = Params(CBaseChainParams::MAIN);
-    int64_t nPowTargetSpacing = params.GetConsensus().nPowTargetSpacing;
-
-    // Generate fake blockchain timestamps relative to
-    // an arbitrary time:
-    int64_t now = 1427379054;
-    SetMockTime(now);
-    for (int i = 0; i < 100; i++)
-    {
-        indexDummy[i].phashBlock = NULL;
-        if (i == 0) indexDummy[i].pprev = NULL;
-        else indexDummy[i].pprev = &indexDummy[i-1];
-        indexDummy[i].nHeight = i;
-        indexDummy[i].nTime = now - (100-i)*nPowTargetSpacing;
-        // Other members don't matter, the partition check code doesn't
-        // use them
-    }
-
-    strMiscWarning = "";
-
-    // Test 1: chain with blocks every nPowTargetSpacing seconds,
-    // as normal, no worries:
-    PartitionCheck(falseFunc, csDummy, &indexDummy[99], nPowTargetSpacing);
-    BOOST_CHECK_MESSAGE(strMiscWarning.empty(), strMiscWarning);
-
-    // Test 2: go 3.5 hours without a block, expect a warning:
-    now += 3*60*60+30*60;
-    SetMockTime(now);
-    PartitionCheck(falseFunc, csDummy, &indexDummy[99], nPowTargetSpacing);
-    BOOST_CHECK(!strMiscWarning.empty());
-    BOOST_TEST_MESSAGE(std::string("Got alert text: ")+strMiscWarning);
-    strMiscWarning = "";
-
-    // Test 3: test the "partition alerts only go off once per day"
-    // code:
-    now += 60*10;
-    SetMockTime(now);
-    PartitionCheck(falseFunc, csDummy, &indexDummy[99], nPowTargetSpacing);
-    BOOST_CHECK(strMiscWarning.empty());
-
-    // Test 4: get 2.5 times as many blocks as expected:
-    now += 60*60*24; // Pretend it is a day later
-    SetMockTime(now);
-    int64_t quickSpacing = nPowTargetSpacing*2/5;
-    for (int i = 0; i < 100; i++) // Tweak chain timestamps:
-        indexDummy[i].nTime = now - (100-i)*quickSpacing;
-    PartitionCheck(falseFunc, csDummy, &indexDummy[99], nPowTargetSpacing);
-    BOOST_CHECK(!strMiscWarning.empty());
-    BOOST_TEST_MESSAGE(std::string("Got alert text: ")+strMiscWarning);
-    strMiscWarning = "";
-
-    SetMockTime(0);
-}
-
-BOOST_AUTO_TEST_SUITE_END()