policy.h File Reference

#include <consensus/consensus.h>
#include <feerate.h>
#include <script/script_flags.h>
#include <optional>
#include <string>

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Functions
static constexpr Amount	DEFAULT_BLOCK_MIN_TX_FEE_PER_KB (1000 *SATOSHI)
	Default for -blockmintxfee, which sets the minimum feerate for a transaction in blocks created by mining code. More...
static const CFeeRate	MEMPOOL_FULL_FEE_INCREMENT (1000 *SATOSHI)
	Default for -incrementalrelayfee, which sets the minimum feerate increase for mempool limiting or BIP 125 replacement. More...
static constexpr Amount	DUST_RELAY_TX_FEE (3000 *SATOSHI)
	Min feerate for defining dust. More...
static constexpr Amount	DEFAULT_MIN_RELAY_TX_FEE_PER_KB (1000 *SATOSHI)
	Default for -minrelaytxfee, minimum relay fee for transactions. More...
Amount	GetDustThreshold (const CTxOut &txout, const CFeeRate &dustRelayFee)
bool	IsDust (const CTxOut &txout, const CFeeRate &dustRelayFee)
bool	IsStandard (const CScript &scriptPubKey, const std::optional< unsigned > &max_datacarrier_bytes, TxoutType &whichType)
bool	IsStandardTx (const CTransaction &tx, const std::optional< unsigned > &max_datacarrier_bytes, 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 for standard transaction types. 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_sigChecks)
static int64_t	GetVirtualTransactionSize (const CTransaction &tx)
static int64_t	GetVirtualTransactionInputSize (const CTxIn &tx)

Variables
static constexpr uint64_t	DEFAULT_MAX_GENERATED_BLOCK_SIZE {16 * ONE_MEGABYTE}
	Default for -blockmaxsize, which controls the maximum size of block the mining code will create. More...
static constexpr unsigned int	MAX_STANDARD_TX_SIZE {100000}
	The maximum size for transactions we're willing to relay/mine. More...
static constexpr unsigned int	MAX_TX_IN_SCRIPT_SIG_SIZE {1650}
	Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed keys (remember the 520 byte limit on redeemScript size). More...
static constexpr unsigned int	DEFAULT_BYTES_PER_SIGCHECK {50}
	Default for -bytespersigcheck . More...
static constexpr bool	DEFAULT_PERMIT_BAREMULTISIG {true}
	Default for -permitbaremultisig. More...
static constexpr bool	DEFAULT_ACCEPT_DATACARRIER {true}
	Default for -datacarrier. More...
static constexpr unsigned int	MAX_OP_RETURN_RELAY {223}
	Default setting for nMaxDatacarrierBytes. More...
static constexpr uint32_t	MANDATORY_SCRIPT_VERIFY_FLAGS
	When transactions fail script evaluations under standard flags, this flagset influences the decision of whether to drop them or to also ban the originator (see CheckInputScripts). More...
static constexpr uint32_t	STANDARD_SCRIPT_VERIFY_FLAGS
	Standard script verification flags that standard transactions will comply with. More...
static constexpr uint32_t	STANDARD_NOT_MANDATORY_VERIFY_FLAGS
	For convenience, standard but not mandatory verify flags. More...
static constexpr uint32_t	STANDARD_LOCKTIME_VERIFY_FLAGS
	Used as the flags parameter to sequence and nLocktime checks in non-consensus code. More...

Function Documentation

AreInputsStandard()

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

Check for standard transaction types.

Parameters

[in]

mapInputs

Map of previous transactions that have outputs we're spending

Returns

True if all inputs (scriptSigs) use only standard transaction forms

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 147 of file policy.cpp.

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DEFAULT_BLOCK_MIN_TX_FEE_PER_KB()

static constexpr Amount DEFAULT_BLOCK_MIN_TX_FEE_PER_KB ( 1000 *  SATOSHI )

staticconstexpr

Default for -blockmintxfee, which sets the minimum feerate for a transaction in blocks created by mining code.

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DEFAULT_MIN_RELAY_TX_FEE_PER_KB()

static constexpr Amount DEFAULT_MIN_RELAY_TX_FEE_PER_KB ( 1000 *  SATOSHI )

staticconstexpr

Default for -minrelaytxfee, minimum relay fee for transactions.

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DUST_RELAY_TX_FEE()

static constexpr Amount DUST_RELAY_TX_FEE ( 3000 *  SATOSHI )

staticconstexpr

Min feerate for defining dust.

Changing the dust limit changes which transactions are standard and should be done with care and ideally rarely. It makes sense to only increase the dust limit after prior releases were already not creating outputs below the new threshold.

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GetDustThreshold()

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

"Dust" is defined in terms of dustRelayFee, which has units satoshis-per-kilobyte. If you'd pay more in fees than the value of the output 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 182*dustRelayFee/1000 (in satoshis). 546 satoshis at the default rate of 3000 sat/kB.

Definition at line 14 of file policy.cpp.

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GetVirtualTransactionInputSize() [1/2]

static int64_t GetVirtualTransactionInputSize ( const CTxIn &  tx )

inlinestatic

Definition at line 163 of file policy.h.

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GetVirtualTransactionInputSize() [2/2]

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

Definition at line 178 of file policy.cpp.

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GetVirtualTransactionSize() [1/3]

static int64_t GetVirtualTransactionSize ( const CTransaction &  tx )

inlinestatic

Definition at line 159 of file policy.h.

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GetVirtualTransactionSize() [2/3]

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

Definition at line 172 of file policy.cpp.

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GetVirtualTransactionSize() [3/3]

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 167 of file policy.cpp.

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IsDust()

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

Definition at line 36 of file policy.cpp.

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IsStandard()

bool IsStandard	(	const CScript &	scriptPubKey,
		const std::optional< unsigned > &	max_datacarrier_bytes,
		TxoutType &	whichType
	)

Definition at line 40 of file policy.cpp.

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IsStandardTx()

bool IsStandardTx	(	const CTransaction &	tx,
		const std::optional< unsigned > &	max_datacarrier_bytes,
		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 68 of file policy.cpp.

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MEMPOOL_FULL_FEE_INCREMENT()

static const CFeeRate MEMPOOL_FULL_FEE_INCREMENT ( 1000 *  SATOSHI )

static

Default for -incrementalrelayfee, which sets the minimum feerate increase for mempool limiting or BIP 125 replacement.

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Variable Documentation

DEFAULT_ACCEPT_DATACARRIER

constexpr bool DEFAULT_ACCEPT_DATACARRIER {true}

staticconstexpr

Default for -datacarrier.

Definition at line 72 of file policy.h.

DEFAULT_BYTES_PER_SIGCHECK

constexpr unsigned int DEFAULT_BYTES_PER_SIGCHECK {50}

staticconstexpr

Default for -bytespersigcheck .

Definition at line 56 of file policy.h.

DEFAULT_MAX_GENERATED_BLOCK_SIZE

constexpr uint64_t DEFAULT_MAX_GENERATED_BLOCK_SIZE {16 * ONE_MEGABYTE}

staticconstexpr

Default for -blockmaxsize, which controls the maximum size of block the mining code will create.

Definition at line 27 of file policy.h.

DEFAULT_PERMIT_BAREMULTISIG

constexpr bool DEFAULT_PERMIT_BAREMULTISIG {true}

staticconstexpr

Default for -permitbaremultisig.

Definition at line 58 of file policy.h.

MANDATORY_SCRIPT_VERIFY_FLAGS

constexpr uint32_t MANDATORY_SCRIPT_VERIFY_FLAGS

staticconstexpr

Initial value:

{
    SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_STRICTENC |
    SCRIPT_ENABLE_SIGHASH_FORKID | SCRIPT_VERIFY_LOW_S |
    SCRIPT_VERIFY_NULLFAIL | SCRIPT_VERIFY_MINIMALDATA |
    SCRIPT_ENABLE_SCHNORR_MULTISIG | SCRIPT_ENFORCE_SIGCHECKS}

When transactions fail script evaluations under standard flags, this flagset influences the decision of whether to drop them or to also ban the originator (see CheckInputScripts).

Definition at line 84 of file policy.h.

MAX_OP_RETURN_RELAY

constexpr unsigned int MAX_OP_RETURN_RELAY {223}

staticconstexpr

Default setting for nMaxDatacarrierBytes.

220 bytes of data, +1 for OP_RETURN, +2 for the pushdata opcodes.

Definition at line 77 of file policy.h.

MAX_STANDARD_TX_SIZE

constexpr unsigned int MAX_STANDARD_TX_SIZE {100000}

staticconstexpr

The maximum size for transactions we're willing to relay/mine.

Definition at line 36 of file policy.h.

MAX_TX_IN_SCRIPT_SIG_SIZE

constexpr unsigned int MAX_TX_IN_SCRIPT_SIG_SIZE {1650}

staticconstexpr

Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed keys (remember the 520 byte limit on redeemScript size).

That works out to a (15*(33+1))+3=513 byte redeemScript, 513+1+15*(73+1)+3=1627 bytes of scriptSig, which we round off to 1650 bytes for some minor future-proofing. That's also enough to spend a 20-of-20 CHECKMULTISIG scriptPubKey, though such a scriptPubKey is not considered standard.

Definition at line 46 of file policy.h.

STANDARD_LOCKTIME_VERIFY_FLAGS

constexpr uint32_t STANDARD_LOCKTIME_VERIFY_FLAGS

staticconstexpr

Initial value:

{
    LOCKTIME_VERIFY_SEQUENCE}

Used as the flags parameter to sequence and nLocktime checks in non-consensus code.

Definition at line 118 of file policy.h.

STANDARD_NOT_MANDATORY_VERIFY_FLAGS

constexpr uint32_t STANDARD_NOT_MANDATORY_VERIFY_FLAGS

staticconstexpr

Initial value:

{
    STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS}

For convenience, standard but not mandatory verify flags.

Definition at line 111 of file policy.h.

STANDARD_SCRIPT_VERIFY_FLAGS

constexpr uint32_t STANDARD_SCRIPT_VERIFY_FLAGS

staticconstexpr

Initial value:

{
    MANDATORY_SCRIPT_VERIFY_FLAGS | SCRIPT_VERIFY_DERSIG |
    SCRIPT_VERIFY_SIGPUSHONLY | SCRIPT_VERIFY_MINIMALDATA |
    SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS | SCRIPT_VERIFY_CLEANSTACK |
    SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY | SCRIPT_VERIFY_CHECKSEQUENCEVERIFY |
    SCRIPT_DISALLOW_SEGWIT_RECOVERY | SCRIPT_VERIFY_INPUT_SIGCHECKS}

Standard script verification flags that standard transactions will comply with.

However scripts violating these flags may still be present in valid blocks and we must accept those blocks.

Note that the actual mempool validation flags may be slightly different (see GetStandardScriptFlags), however this constant should be set to the most restrictive flag set that applies in the current / next upgrade, since it is used in numerous parts of the codebase that are unable to access the contextual information of which upgrades are currently active.

Definition at line 101 of file policy.h.