Lenient gas limit.

Two uncles only.
Min 2048 difficulty & assoc adjustment.

libethcore/BlockInfo.cpp

@@ -191,16 +191,19 @@ u256 BlockInfo::calculateDifficulty(BlockInfo const& _parent) const
 	if (!parentHash)
 		return c_genesisDifficulty;
 	else
-		return max<u256>(1024, timestamp >= _parent.timestamp + (c_protocolVersion == 49 ? 5 : 8) ? _parent.difficulty - (_parent.difficulty >> 10) : (_parent.difficulty + (_parent.difficulty >> 10)));
+		return max<u256>(2048, timestamp >= _parent.timestamp + (c_protocolVersion == 49 ? 5 : 8) ? _parent.difficulty - (_parent.difficulty / 2048) : (_parent.difficulty + (_parent.difficulty / 2048)));
 }
 
+template <class N> inline N diff(N const& _a, N const& _b) { return max(_a, _b) - min(_a, _b); }
+
 void BlockInfo::verifyParent(BlockInfo const& _parent) const
 {	// Check difficulty is correct given the two timestamps.
 	if (difficulty != calculateDifficulty(_parent))
 		BOOST_THROW_EXCEPTION(InvalidDifficulty());
 
-	if (gasLimit != calculateGasLimit(_parent))
+	if (diff(gasLimit, _parent.gasLimit) <= _parent.gasLimit / 1024)
-		BOOST_THROW_EXCEPTION(InvalidGasLimit(gasLimit, calculateGasLimit(_parent)));
+		BOOST_THROW_EXCEPTION(InvalidGasLimit(gasLimit, calculateGasLimit(_parent), diff(gasLimit, _parent.gasLimit), _parent.gasLimit / 1024));
+
 
 	// Check timestamp is after previous timestamp.
 	if (parentHash)

libethcore/Exceptions.cpp

@@ -39,7 +39,7 @@ static boost::thread_specific_ptr<string> g_exceptionMessage;
 const char* InvalidBlockFormat::what() const noexcept { ETH_RETURN_STRING("Invalid block format: Bad field " + toString(m_f) + " (" + toHex(m_d) + ")"); }
 const char* UncleInChain::what() const noexcept { ETH_RETURN_STRING("Uncle in block already mentioned: Uncles " + toString(m_uncles) + " (" + m_block.abridged() + ")"); }
 const char* InvalidTransactionsHash::what() const noexcept { ETH_RETURN_STRING("Invalid transactions hash:  header says: " + toHex(m_head.ref()) + " block is:" + toHex(m_real.ref())); }
-const char* InvalidGasLimit::what() const noexcept { ETH_RETURN_STRING("Invalid gas limit (provided: " + toString(provided) + " valid:" + toString(valid) + ")"); }
+const char* InvalidGasLimit::what() const noexcept { ETH_RETURN_STRING("Invalid gas limit (provided: " + toString(provided) + " default:" + toString(valid) + " givenDiff:" + toString(givenDiff) + " maxDiff:" + toString(maxDiff) + ")"); }
 const char* InvalidMinGasPrice::what() const noexcept { ETH_RETURN_STRING("Invalid minimum gas price (provided: " + toString(provided) + " limit:" + toString(limit) + ")"); }
 const char* InvalidNonce::what() const noexcept { ETH_RETURN_STRING("Invalid nonce (r: " + toString(required) + " c:" + toString(candidate) + ")"); }
 const char* InvalidBlockNonce::what() const noexcept { ETH_RETURN_STRING("Invalid nonce (h: " + toString(h) + " n:" + toString(n) + " d:" + toString(d) + ")"); }

libethcore/Exceptions.h

@@ -47,6 +47,7 @@ struct InvalidSignature: virtual dev::Exception {};
 class InvalidBlockFormat: virtual public dev::Exception { public: InvalidBlockFormat(int _f, bytesConstRef _d): m_f(_f), m_d(_d.toBytes()) {} int m_f; bytes m_d; virtual const char* what() const noexcept; };
 struct InvalidUnclesHash: virtual dev::Exception {};
 struct InvalidUncle: virtual dev::Exception {};
+struct TooManyUncles: virtual dev::Exception {};
 struct UncleTooOld: virtual dev::Exception {};
 class UncleInChain: virtual public dev::Exception { public: UncleInChain(h256Set _uncles, h256 _block): m_uncles(_uncles), m_block(_block) {} h256Set m_uncles; h256 m_block; virtual const char* what() const noexcept; };
 struct DuplicateUncleNonce: virtual dev::Exception {};
@@ -55,7 +56,7 @@ struct InvalidGasUsed: virtual dev::Exception {};
 class InvalidTransactionsHash: virtual public dev::Exception { public: InvalidTransactionsHash(h256 _head, h256 _real): m_head(_head), m_real(_real) {} h256 m_head; h256 m_real; virtual const char* what() const noexcept; };
 struct InvalidTransaction: virtual dev::Exception {};
 struct InvalidDifficulty: virtual dev::Exception {};
-class InvalidGasLimit: virtual public dev::Exception { public: InvalidGasLimit(u256 _provided = 0, u256 _valid = 0): provided(_provided), valid(_valid) {} u256 provided; u256 valid; virtual const char* what() const noexcept; };
+class InvalidGasLimit: virtual public dev::Exception { public: InvalidGasLimit(u256 _provided = 0, u256 _valid = 0, u256 _gD = 0, u256 _mD = 0): provided(_provided), valid(_valid), givenDiff(_gD), maxDiff(_mD) {} u256 provided; u256 valid; u256 givenDiff; u256 maxDiff; virtual const char* what() const noexcept; };
 class InvalidMinGasPrice: virtual public dev::Exception { public: InvalidMinGasPrice(u256 _provided = 0, u256 _limit = 0): provided(_provided), limit(_limit) {} u256 provided; u256 limit; virtual const char* what() const noexcept; };
 struct InvalidTransactionGasUsed: virtual dev::Exception {};
 struct InvalidTransactionsStateRoot: virtual dev::Exception {};

libethereum/State.cpp

@@ -486,10 +486,11 @@ u256 State::enact(bytesConstRef _block, BlockChain const& _bc, bool _checkNonce)
 	receiptsTrie.init();
 
 	LastHashes lh = getLastHashes(_bc, (unsigned)m_previousBlock.number);
+	RLP rlp(_block);
 
 	// All ok with the block generally. Play back the transactions now...
 	unsigned i = 0;
-	for (auto const& tr: RLP(_block)[1])
+	for (auto const& tr: rlp[1])
 	{
 		RLPStream k;
 		k << i;
@@ -503,17 +504,11 @@ u256 State::enact(bytesConstRef _block, BlockChain const& _bc, bool _checkNonce)
 		++i;
 	}
 
-	if (transactionsTrie.root() != m_currentBlock.transactionsRoot)
-	{
-		cwarn << "Bad transactions state root!";
-		BOOST_THROW_EXCEPTION(InvalidTransactionsStateRoot());
-	}
-
 	if (receiptsTrie.root() != m_currentBlock.receiptsRoot)
 	{
 		cwarn << "Bad receipts state root.";
 		cwarn << "Block:" << toHex(_block);
-		cwarn << "Block RLP:" << RLP(_block);
+		cwarn << "Block RLP:" << rlp;
 		cwarn << "Calculated: " << receiptsTrie.root();
 		for (unsigned j = 0; j < i; ++j)
 		{
@@ -548,10 +543,14 @@ u256 State::enact(bytesConstRef _block, BlockChain const& _bc, bool _checkNonce)
 	u256 tdIncrease = m_currentBlock.difficulty;
 
 	// Check uncles & apply their rewards to state.
+	if (rlp[2].itemCount() > 2)
+		BOOST_THROW_EXCEPTION(TooManyUncles());
+
 	set<h256> nonces = { m_currentBlock.nonce };
 	Addresses rewarded;
 	set<h256> knownUncles = _bc.allUnclesFrom(m_currentBlock.parentHash);
-	for (auto const& i: RLP(_block)[2])
+
+	for (auto const& i: rlp[2])
 	{
 		if (knownUncles.count(sha3(i.data())))
 			BOOST_THROW_EXCEPTION(UncleInChain(knownUncles, sha3(i.data()) ));
@@ -699,7 +698,7 @@ void State::commitToMine(BlockChain const& _bc)
 //		cout << "Checking " << m_previousBlock.hash << ", parent=" << m_previousBlock.parentHash << endl;
 		set<h256> knownUncles = _bc.allUnclesFrom(m_currentBlock.parentHash);
 		auto p = m_previousBlock.parentHash;
-		for (unsigned gen = 0; gen < 6 && p != _bc.genesisHash(); ++gen, p = _bc.details(p).parent)
+		for (unsigned gen = 0; gen < 6 && p != _bc.genesisHash() && unclesCount < 2; ++gen, p = _bc.details(p).parent)
 		{
 			auto us = _bc.details(p).children;
 			assert(us.size() >= 1);	// must be at least 1 child of our grandparent - it's our own parent!
@@ -710,6 +709,8 @@ void State::commitToMine(BlockChain const& _bc)
 					ubi.streamRLP(unclesData, WithNonce);
 					++unclesCount;
 					uncleAddresses.push_back(ubi.coinbaseAddress);
+					if (unclesCount == 2)
+						break;
 				}
 		}
 	}