policy.cpp File Reference

#include <policy/policy.h>
#include <consensus/validation.h>
#include <coins.h>

Functions
CAmount	GetDustThreshold (const CTxOut &txout, const CFeeRate &dustRelayFeeIn)
bool	IsDust (const CTxOut &txout, const CFeeRate &dustRelayFeeIn)
bool	IsStandard (const CScript &scriptPubKey, txnouttype &whichType)
bool	IsStandardTx (const CTransaction &tx, bool permit_bare_multisig, const CFeeRate &dust_relay_fee, std::string &reason)
bool	AreInputsStandard (const CTransaction &tx, const CCoinsViewCache &mapInputs)
bool	IsWitnessStandard (const CTransaction &tx, const CCoinsViewCache &mapInputs)
int64_t	GetVirtualTransactionSize (int64_t nWeight, int64_t nSigOpCost, unsigned int bytes_per_sigop)
int64_t	GetVirtualTransactionSize (const CTransaction &tx, int64_t nSigOpCost, unsigned int bytes_per_sigop)
int64_t	GetVirtualTransactionInputSize (const CTxIn &txin, int64_t nSigOpCost, unsigned int bytes_per_sigop)

Function Documentation

AreInputsStandard()

bool AreInputsStandard	(	const CTransaction &	tx,
		const CCoinsViewCache &	mapInputs
	)

Check transaction inputs to mitigate two potential denial-of-service attacks:

1. scriptSigs with extra data stuffed into them, not consumed by scriptPubKey (or P2SH script)
2. P2SH scripts with a crazy number of expensive CHECKSIG/CHECKMULTISIG operations

Why bother? To avoid denial-of-service attacks; an attacker can submit a standard HASH... OP_EQUAL transaction, which will get accepted into blocks. The redemption script can be anything; an attacker could use a very expensive-to-check-upon-redemption script like: DUP CHECKSIG DROP ... repeated 100 times... OP_1

GetDustThreshold()

CAmount GetDustThreshold	(	const CTxOut &	txout,
		const CFeeRate &	dustRelayFeeIn
	)

GetVirtualTransactionInputSize()

int64_t GetVirtualTransactionInputSize	(	const CTxIn &	txin,
		int64_t	nSigOpCost,
		unsigned int	bytes_per_sigop
	)

GetVirtualTransactionSize() [1/2]

int64_t GetVirtualTransactionSize	(	int64_t	nWeight,
		int64_t	nSigOpCost,
		unsigned int	bytes_per_sigop
	)

Compute the virtual transaction size (weight reinterpreted as bytes).

GetVirtualTransactionSize() [2/2]

int64_t GetVirtualTransactionSize	(	const CTransaction &	tx,
		int64_t	nSigOpCost,
		unsigned int	bytes_per_sigop
	)

IsDust()

bool IsDust	(	const CTxOut &	txout,
		const CFeeRate &	dustRelayFeeIn
	)

IsStandard()

bool IsStandard	(	const CScript &	scriptPubKey,
		txnouttype &	whichType
	)

IsStandardTx()

bool IsStandardTx	(	const CTransaction &	tx,
		bool	permit_bare_multisig,
		const CFeeRate &	dust_relay_fee,
		std::string &	reason
	)

Check for standard transaction types

Returns

True if all outputs (scriptPubKeys) use only standard transaction forms

IsWitnessStandard()

bool IsWitnessStandard	(	const CTransaction &	tx,
		const CCoinsViewCache &	mapInputs
	)

Check if the transaction is over standard P2WSH resources limit: 3600bytes witnessScript size, 80bytes per witness stack element, 100 witness stack elements These limits are adequate for multi-signature up to n-of-100 using OP_CHECKSIG, OP_ADD, and OP_EQUAL,