Make max tip age an option instead of chainparam

After discussion in #7164 I think this is better.

Max tip age was introduced in #5987 to make it possible to run
testnet-in-a-box. But associating this behavior with the testnet chain
is wrong conceptually, as it is not needed in normal usage.
Should aim to make testnet test the software as-is.

Replace it with a (debug) option `-maxtipage`, which can be
specified only in the specific case.

src/chainparams.cpp

@@ -115,7 +115,6 @@ public:
         pchMessageStart[3] = 0x64;
         vAlertPubKey = ParseHex("04b7ecf0baa90495ceb4e4090f6b2fd37eec1e9c85fac68a487f3ce11589692e4a317479316ee814e066638e1db54e37a10689b70286e6315b1087b6615d179264");
         nDefaultPort = 8233;
-        nMaxTipAge = 24 * 60 * 60;
         nPruneAfterHeight = 100000;
         const size_t N = 200, K = 9;
         BOOST_STATIC_ASSERT(equihash_parameters_acceptable(N, K));
@@ -275,7 +274,6 @@ public:
         pchMessageStart[3] = 0xbf;
         vAlertPubKey = ParseHex("044e7a1553392325c871c5ace5d6ad73501c66f4c185d6b0453cf45dec5a1322e705c672ac1a27ef7cdaf588c10effdf50ed5f95f85f2f54a5f6159fca394ed0c6");
         nDefaultPort = 18233;
-        nMaxTipAge = 24 * 60 * 60;
         nPruneAfterHeight = 1000;
         const size_t N = 200, K = 9;
         BOOST_STATIC_ASSERT(equihash_parameters_acceptable(N, K));
@@ -387,7 +385,6 @@ public:
         pchMessageStart[2] = 0x3f;
         pchMessageStart[3] = 0x5f;
         nDefaultPort = 18344;
-        nMaxTipAge = 24 * 60 * 60;
         nPruneAfterHeight = 1000;
         const size_t N = 48, K = 5;
         BOOST_STATIC_ASSERT(equihash_parameters_acceptable(N, K));

src/chainparams.h

@@ -68,7 +68,6 @@ public:
     bool DefaultConsistencyChecks() const { return fDefaultConsistencyChecks; }
     /** Policy: Filter transactions that do not match well-defined patterns */
     bool RequireStandard() const { return fRequireStandard; }
-    int64_t MaxTipAge() const { return nMaxTipAge; }
     int64_t PruneAfterHeight() const { return nPruneAfterHeight; }
     unsigned int EquihashN() const { return nEquihashN; }
     unsigned int EquihashK() const { return nEquihashK; }
@@ -97,7 +96,6 @@ protected:
     //! Raw pub key bytes for the broadcast alert signing key.
     std::vector<unsigned char> vAlertPubKey;
     int nDefaultPort = 0;
-    long nMaxTipAge = 0;
     uint64_t nPruneAfterHeight = 0;
     unsigned int nEquihashN = 0;
     unsigned int nEquihashK = 0;

src/init.cpp

@@ -472,6 +472,7 @@ std::string HelpMessage(HelpMessageMode mode)
         strUsage += HelpMessageOpt("-limitfreerelay=<n>", strprintf("Continuously rate-limit free transactions to <n>*1000 bytes per minute (default: %u)", 15));
         strUsage += HelpMessageOpt("-relaypriority", strprintf("Require high priority for relaying free or low-fee transactions (default: %u)", 0));
         strUsage += HelpMessageOpt("-maxsigcachesize=<n>", strprintf("Limit size of signature cache to <n> entries (default: %u)", 50000));
+        strUsage += HelpMessageOpt("-maxtipage=<n>", strprintf("Maximum tip age in seconds to consider node in initial block download (default: %u)", DEFAULT_MAX_TIP_AGE));
     }
     strUsage += HelpMessageOpt("-minrelaytxfee=<amt>", strprintf(_("Fees (in %s/kB) smaller than this are considered zero fee for relaying (default: %s)"),
         CURRENCY_UNIT, FormatMoney(::minRelayTxFee.GetFeePerK())));
@@ -1077,6 +1078,8 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
     if (GetBoolArg("-peerbloomfilters", true))
         nLocalServices |= NODE_BLOOM;
 
+    nMaxTipAge = GetArg("-maxtipage", DEFAULT_MAX_TIP_AGE);
+
 #ifdef ENABLE_MINING
     if (mapArgs.count("-mineraddress")) {
         CTxDestination addr = DecodeDestination(mapArgs["-mineraddress"]);

src/main.cpp

@@ -75,6 +75,9 @@ bool fCoinbaseEnforcedProtectionEnabled = true;
 size_t nCoinCacheUsage = 5000 * 300;
 uint64_t nPruneTarget = 0;
 bool fAlerts = DEFAULT_ALERTS;
+/* If the tip is older than this (in seconds), the node is considered to be in initial block download.
+ */
+int64_t nMaxTipAge = DEFAULT_MAX_TIP_AGE;
 
 unsigned int expiryDelta = DEFAULT_TX_EXPIRY_DELTA;
 
@@ -1733,7 +1736,7 @@ bool IsInitialBlockDownload()
     if (lockIBDState)
         return false;
     bool state = (chainActive.Height() < pindexBestHeader->nHeight - 24 * 6 ||
-            pindexBestHeader->GetBlockTime() < GetTime() - chainParams.MaxTipAge());
+            pindexBestHeader->GetBlockTime() < GetTime() - nMaxTipAge);
     if (!state)
         lockIBDState = true;
     return state;

src/main.h

@@ -98,6 +98,7 @@ static const unsigned int DATABASE_WRITE_INTERVAL = 60 * 60;
 static const unsigned int DATABASE_FLUSH_INTERVAL = 24 * 60 * 60;
 /** Maximum length of reject messages. */
 static const unsigned int MAX_REJECT_MESSAGE_LENGTH = 111;
+static const int64_t DEFAULT_MAX_TIP_AGE = 24 * 60 * 60;
 
 // Sanity check the magic numbers when we change them
 BOOST_STATIC_ASSERT(DEFAULT_BLOCK_MAX_SIZE <= MAX_BLOCK_SIZE);
@@ -137,6 +138,7 @@ extern bool fCoinbaseEnforcedProtectionEnabled;
 extern size_t nCoinCacheUsage;
 extern CFeeRate minRelayTxFee;
 extern bool fAlerts;
+extern int64_t nMaxTipAge;
 
 /** Best header we've seen so far (used for getheaders queries' starting points). */
 extern CBlockIndex *pindexBestHeader;