Add unit test for HeadersSyncState

src/Makefile.test.include

@@ -93,6 +93,7 @@ BITCOIN_TESTS =\
   test/fs_tests.cpp \
   test/getarg_tests.cpp \
   test/hash_tests.cpp \
+  test/headers_sync_chainwork.cpp \
   test/httpserver_tests.cpp \
   test/i2p_tests.cpp \
   test/interfaces_tests.cpp \

src/test/headers_sync_chainwork.cpp

@@ -0,0 +1,146 @@
+// Copyright (c) 2022 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <chain.h>
+#include <chainparams.h>
+#include <consensus/params.h>
+#include <headerssync.h>
+#include <pow.h>
+#include <test/util/setup_common.h>
+#include <validation.h>
+#include <vector>
+
+#include <boost/test/unit_test.hpp>
+
+struct HeadersGeneratorSetup : public RegTestingSetup {
+    /** Search for a nonce to meet (regtest) proof of work */
+    void FindProofOfWork(CBlockHeader& starting_header);
+    /**
+     * Generate headers in a chain that build off a given starting hash, using
+     * the given nVersion, advancing time by 1 second from the starting
+     * prev_time, and with a fixed merkle root hash.
+     */
+    void GenerateHeaders(std::vector<CBlockHeader>& headers, size_t count,
+            const uint256& starting_hash, const int nVersion, int prev_time,
+            const uint256& merkle_root, const uint32_t nBits);
+};
+
+void HeadersGeneratorSetup::FindProofOfWork(CBlockHeader& starting_header)
+{
+    while (!CheckProofOfWork(starting_header.GetHash(), starting_header.nBits, Params().GetConsensus())) {
+        ++(starting_header.nNonce);
+    }
+}
+
+void HeadersGeneratorSetup::GenerateHeaders(std::vector<CBlockHeader>& headers,
+        size_t count, const uint256& starting_hash, const int nVersion, int prev_time,
+        const uint256& merkle_root, const uint32_t nBits)
+{
+    uint256 prev_hash = starting_hash;
+
+    while (headers.size() < count) {
+        headers.push_back(CBlockHeader());
+        CBlockHeader& next_header = headers.back();;
+        next_header.nVersion = nVersion;
+        next_header.hashPrevBlock = prev_hash;
+        next_header.hashMerkleRoot = merkle_root;
+        next_header.nTime = prev_time+1;
+        next_header.nBits = nBits;
+
+        FindProofOfWork(next_header);
+        prev_hash = next_header.GetHash();
+        prev_time = next_header.nTime;
+    }
+    return;
+}
+
+BOOST_FIXTURE_TEST_SUITE(headers_sync_chainwork_tests, HeadersGeneratorSetup)
+
+// In this test, we construct two sets of headers from genesis, one with
+// sufficient proof of work and one without.
+// 1. We deliver the first set of headers and verify that the headers sync state
+//    updates to the REDOWNLOAD phase successfully.
+// 2. Then we deliver the second set of headers and verify that they fail
+//    processing (presumably due to commitments not matching).
+// 3. Finally, we verify that repeating with the first set of headers in both
+//    phases is successful.
+BOOST_AUTO_TEST_CASE(headers_sync_state)
+{
+    std::vector<CBlockHeader> first_chain;
+    std::vector<CBlockHeader> second_chain;
+
+    HeadersSyncState *hss = new HeadersSyncState(0, Params().GetConsensus());
+
+    const int target_blocks = 15000;
+    arith_uint256 chain_work = target_blocks*2;
+
+    // Generate headers for two different chains (using differing merkle roots
+    // to ensure the headers are different).
+    GenerateHeaders(first_chain, target_blocks-1, Params().GenesisBlock().GetHash(),
+            Params().GenesisBlock().nVersion, Params().GenesisBlock().nTime,
+            ArithToUint256(0), Params().GenesisBlock().nBits);
+
+    GenerateHeaders(second_chain, target_blocks-2, Params().GenesisBlock().GetHash(),
+            Params().GenesisBlock().nVersion, Params().GenesisBlock().nTime,
+            ArithToUint256(1), Params().GenesisBlock().nBits);
+
+    const CBlockIndex* chain_start = WITH_LOCK(::cs_main, return m_node.chainman->m_blockman.LookupBlockIndex(Params().GenesisBlock().GetHash()));
+    std::vector<CBlockHeader> headers_batch;
+    std::vector<CBlockHeader> headers_to_process;
+    bool success{false};
+
+    // Feed the first chain to HeadersSyncState, by delivering 1 header
+    // initially and then the rest.
+    headers_batch.insert(headers_batch.end(), std::next(first_chain.begin(), 1), first_chain.end());
+
+    (void)hss->StartInitialDownload(chain_start, {first_chain.front()}, chain_work, m_node.chainman->ActiveChain().GetLocator(chain_start));
+    (void)hss->ProcessNextHeaders(headers_batch, true, headers_to_process, success);
+
+    // This chain should look valid, and we should have met the proof-of-work
+    // requirement.
+    BOOST_CHECK(success);
+    BOOST_CHECK(hss->GetState() == HeadersSyncState::State::REDOWNLOAD);
+
+    // Try to sneakily feed back the second chain.
+    (void)hss->ProcessNextHeaders(second_chain, true, headers_to_process, success);
+    BOOST_CHECK(!success); // foiled!
+    BOOST_CHECK(hss->GetState() == HeadersSyncState::State::FINAL);
+
+    delete hss; hss = new HeadersSyncState(0, Params().GetConsensus());
+
+    // Now try again, this time feeding the first chain twice.
+    (void)hss->StartInitialDownload(chain_start, first_chain, chain_work,
+            m_node.chainman->ActiveChain().GetLocator(chain_start));
+    BOOST_CHECK(hss->GetState() == HeadersSyncState::State::REDOWNLOAD);
+
+    (void)hss->ProcessNextHeaders(first_chain, true, headers_to_process, success);
+    BOOST_CHECK(success);
+    // All headers should be ready for acceptance:
+    BOOST_CHECK(headers_to_process.size() == first_chain.size());
+    // Nothing left for the sync logic to do:
+    BOOST_CHECK(hss->GetState() == HeadersSyncState::State::FINAL);
+
+    delete hss; hss = new HeadersSyncState(0, Params().GetConsensus());
+
+    // Finally, verify that just trying to process the second chain would not
+    // succeed (too little work)
+    (void)hss->StartInitialDownload(chain_start, {second_chain.front()},
+            chain_work, m_node.chainman->ActiveChain().GetLocator(chain_start));
+    BOOST_CHECK(hss->GetState() == HeadersSyncState::State::INITIAL_DOWNLOAD);
+
+    headers_batch.clear();
+    headers_batch.insert(headers_batch.end(), std::next(second_chain.begin(), 1), second_chain.end());
+    headers_to_process.clear();
+    // Tell the sync logic that the headers message was not full, implying no
+    // more headers can be requested. For a low-work-chain, this should causes
+    // the sync to end with no headers for acceptance.
+    (void)hss->ProcessNextHeaders(headers_batch, false, headers_to_process, success);
+    BOOST_CHECK(hss->GetState() == HeadersSyncState::State::FINAL);
+    BOOST_CHECK(headers_to_process.empty());
+    // Nevertheless, no validation errors should have been detected with the
+    // chain:
+    BOOST_CHECK(success);
+}
+
+BOOST_AUTO_TEST_SUITE_END()