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

@@ -92,7 +92,6 @@ public:
         pchMessageStart[3] = 0xd9;
         vAlertPubKey = ParseHex("04fc9702847840aaf195de8442ebecedf5b095cdbb9bc716bda9110971b28a49e0ead8564ff0db22209e0374782c093bb899692d524e9d6a6956e7c5ecbcd68284");
         nDefaultPort = 8333;
-        nMaxTipAge = 24 * 60 * 60;
         nPruneAfterHeight = 100000;
 
         genesis = CreateGenesisBlock(1231006505, 2083236893, 0x1d00ffff, 1, 50 * COIN);
@@ -169,7 +168,6 @@ public:
         pchMessageStart[3] = 0x07;
         vAlertPubKey = ParseHex("04302390343f91cc401d56d68b123028bf52e5fca1939df127f63c6467cdf9c8e2c14b61104cf817d0b780da337893ecc4aaff1309e536162dabbdb45200ca2b0a");
         nDefaultPort = 18333;
-        nMaxTipAge = 0x7fffffff;
         nPruneAfterHeight = 1000;
 
         genesis = CreateGenesisBlock(1296688602, 414098458, 0x1d00ffff, 1, 50 * COIN);
@@ -233,7 +231,6 @@ public:
         pchMessageStart[1] = 0xbf;
         pchMessageStart[2] = 0xb5;
         pchMessageStart[3] = 0xda;
-        nMaxTipAge = 24 * 60 * 60;
         nDefaultPort = 18444;
         nPruneAfterHeight = 1000;
 

src/chainparams.h

@@ -64,7 +64,6 @@ 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; }
     uint64_t PruneAfterHeight() const { return nPruneAfterHeight; }
     /** Make miner stop after a block is found. In RPC, don't return until nGenProcLimit blocks are generated */
     bool MineBlocksOnDemand() const { return fMineBlocksOnDemand; }
@@ -84,7 +83,6 @@ protected:
     //! Raw pub key bytes for the broadcast alert signing key.
     std::vector<unsigned char> vAlertPubKey;
     int nDefaultPort;
-    long nMaxTipAge;
     uint64_t nPruneAfterHeight;
     std::vector<CDNSSeedData> vSeeds;
     std::vector<unsigned char> base58Prefixes[MAX_BASE58_TYPES];

src/init.cpp

@@ -456,6 +456,7 @@ std::string HelpMessage(HelpMessageMode mode)
         strUsage += HelpMessageOpt("-limitfreerelay=<n>", strprintf("Continuously rate-limit free transactions to <n>*1000 bytes per minute (default: %u)", DEFAULT_LIMITFREERELAY));
         strUsage += HelpMessageOpt("-relaypriority", strprintf("Require high priority for relaying free or low-fee transactions (default: %u)", DEFAULT_RELAYPRIORITY));
         strUsage += HelpMessageOpt("-maxsigcachesize=<n>", strprintf("Limit size of signature cache to <n> MiB (default: %u)", DEFAULT_MAX_SIG_CACHE_SIZE));
+        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, mining and transaction creation (default: %s)"),
         CURRENCY_UNIT, FormatMoney(DEFAULT_MIN_RELAY_TX_FEE)));
@@ -994,6 +995,8 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
     if (GetBoolArg("-peerbloomfilters", true))
         nLocalServices |= NODE_BLOOM;
 
+    nMaxTipAge = GetArg("-maxtipage", DEFAULT_MAX_TIP_AGE);
+
     // ********************************************************* Step 4: application initialization: dir lock, daemonize, pidfile, debug log
 
     // Initialize elliptic curve code

src/main.cpp

@@ -74,6 +74,9 @@ bool fCheckpointsEnabled = DEFAULT_CHECKPOINTS_ENABLED;
 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;
 
 /** Fees smaller than this (in satoshi) are considered zero fee (for relaying, mining and transaction creation) */
 CFeeRate minRelayTxFee = CFeeRate(DEFAULT_MIN_RELAY_TX_FEE);
@@ -1402,7 +1405,7 @@ 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

@@ -89,6 +89,7 @@ static const unsigned int DATABASE_FLUSH_INTERVAL = 24 * 60 * 60;
 static const unsigned int MAX_REJECT_MESSAGE_LENGTH = 111;
 static const unsigned int DEFAULT_LIMITFREERELAY = 15;
 static const bool DEFAULT_RELAYPRIORITY = true;
+static const int64_t DEFAULT_MAX_TIP_AGE = 24 * 60 * 60;
 
 /** Default for -permitbaremultisig */
 static const bool DEFAULT_PERMIT_BAREMULTISIG = true;
@@ -127,6 +128,7 @@ extern bool fCheckpointsEnabled;
 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;