policy.cpp File Reference

#include <coins.h>
#include <policy/policy.h>
#include <script/interpreter.h>
#include <util/system.h>

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Functions
Amount	GetDustThreshold (const CTxOut &txout, const CFeeRate &dustRelayFeeIn)
bool	IsDust (const CTxOut &txout, const CFeeRate &dustRelayFeeIn)
bool	IsStandard (const CScript &scriptPubKey, TxoutType &whichType)
bool	IsStandardTx (const CTransaction &tx, bool permit_bare_multisig, const CFeeRate &dust_relay_fee, std::string &reason)
	Check for standard transaction types. More...
bool	AreInputsStandard (const CTransaction &tx, const CCoinsViewCache &mapInputs, uint32_t flags)
	Check transaction inputs to mitigate two potential denial-of-service attacks: More...
int64_t	GetVirtualTransactionSize (int64_t nSize, int64_t nSigChecks, unsigned int bytes_per_sigCheck)
	Compute the virtual transaction size (size, or more if sigChecks are too dense). More...
int64_t	GetVirtualTransactionSize (const CTransaction &tx, int64_t nSigChecks, unsigned int bytes_per_sigCheck)
int64_t	GetVirtualTransactionInputSize (const CTxIn &txin, int64_t nSigChecks, unsigned int bytes_per_sigCheck)

Function Documentation

AreInputsStandard()

bool AreInputsStandard	(	const CTransaction &	tx,
		const CCoinsViewCache &	mapInputs,
		uint32_t	flags
	)

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

Check for standard transaction types.

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

Definition at line 144 of file policy.cpp.

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GetDustThreshold()

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

"Dust" is defined in terms of dustRelayFee, which has units satoshis-per-kilobyte. If you'd pay more than 1/3 in fees to spend something, then we consider it dust. A typical spendable txout is 34 bytes big, and will need a CTxIn of at least 148 bytes to spend: so dust is a spendable txout less than 546*dustRelayFee/1000 (in satoshis).

Definition at line 14 of file policy.cpp.

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GetVirtualTransactionInputSize()

int64_t GetVirtualTransactionInputSize	(	const CTxIn &	txin,
		int64_t	nSigChecks,
		unsigned int	bytes_per_sigCheck
	)

Definition at line 175 of file policy.cpp.

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GetVirtualTransactionSize() [1/2]

int64_t GetVirtualTransactionSize	(	const CTransaction &	tx,
		int64_t	nSigChecks,
		unsigned int	bytes_per_sigCheck
	)

Definition at line 169 of file policy.cpp.

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GetVirtualTransactionSize() [2/2]

int64_t GetVirtualTransactionSize	(	int64_t	nSize,
		int64_t	nSigChecks,
		unsigned int	bytes_per_sigCheck
	)

Compute the virtual transaction size (size, or more if sigChecks are too dense).

Definition at line 164 of file policy.cpp.

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IsDust()

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

Definition at line 34 of file policy.cpp.

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IsStandard()

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

Definition at line 38 of file policy.cpp.

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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

Definition at line 69 of file policy.cpp.

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