Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

change(mempool): Refactor the ZIP-317 minimum fee rate calculation to use usize #6585

Merged
merged 2 commits into from
Apr 28, 2023
Merged

change(mempool): Refactor the ZIP-317 minimum fee rate calculation to use usize #6585

Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
b07b634
Refactor the minimum fee rate calculation to use usize
teor2345 Apr 27, 2023
ca54611
Check for overflow if constants change
teor2345 Apr 27, 2023
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
38 changes: 34 additions & 4 deletions zebra-chain/src/transaction/unmined/zip317.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,23 @@ const MIN_BLOCK_PRODUCTION_SUBSTITUTE_FEE: i64 = 1;
/// `block_unpaid_action_limit` in ZIP-317.
pub const BLOCK_PRODUCTION_UNPAID_ACTION_LIMIT: u32 = 50;

/// The minimum fee per kilobyte for Zebra mempool transactions.
/// Also used as the minimum fee for a mempool transaction.
///
/// Based on `DEFAULT_MIN_RELAY_TX_FEE` in `zcashd`:
/// <https://github.com/zcash/zcash/blob/f512291ff20098291442e83713de89bcddc07546/src/main.h#L71-L72>
///
/// This is a `usize` to simplify transaction size-based calculation code.
pub const MIN_MEMPOOL_TX_FEE_RATE: usize = 100;

/// The fee cap for [`MIN_MEMPOOL_TX_FEE_RATE`] minimum required mempool fees.
///
/// Based on `LEGACY_DEFAULT_FEE` in `zcashd`:
/// <https://github.com/zcash/zcash/blob/9e856cfc5b81aa2607a16a23ff5584ea10014de6/src/amount.h#L35-L36>
///
/// This is a `usize` to simplify transaction size-based calculation code.
pub const MEMPOOL_TX_FEE_REQUIREMENT_CAP: usize = 1000;

/// Returns the conventional fee for `transaction`, as defined by [ZIP-317].
///
/// [ZIP-317]: https://zips.z.cash/zip-0317#fee-calculation
Expand Down Expand Up @@ -184,11 +201,24 @@ pub fn mempool_checks(
// > with a maximum fee of 1000 zatoshis. In zcashd this is `DEFAULT_MIN_RELAY_TX_FEE`.
//
// <https://github.com/ZcashFoundation/zebra/issues/5336#issuecomment-1506748801>
let limit = std::cmp::min(
1000,
(f32::floor(100.0 * transaction_size as f32 / 1000.0)) as u64,
const KILOBYTE: usize = 1000;

// This calculation can't overflow, because transactions are limited to 2 MB,
// and usize is at least 4 GB.
assert!(
MIN_MEMPOOL_TX_FEE_RATE
< usize::MAX / usize::try_from(MAX_BLOCK_BYTES).expect("constant fits in usize"),
"the fee rate multiplication must never overflow",
);
if miner_fee < Amount::<NonNegative>::try_from(limit).expect("limit value is invalid") {

let min_fee = (MIN_MEMPOOL_TX_FEE_RATE * transaction_size / KILOBYTE)
.clamp(MIN_MEMPOOL_TX_FEE_RATE, MEMPOOL_TX_FEE_REQUIREMENT_CAP);
Comment on lines +214 to +215
Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

It seemed easier to do this calculation in usize then convert to Amount, which is what zcashd does.

Otherwise every calculation has to be checked for overflow, even though we clamp to [100, 1000] at the end anyway.

let min_fee: u64 = min_fee
.try_into()
.expect("clamped value always fits in u64");
let min_fee: Amount<NonNegative> = min_fee.try_into().expect("clamped value is positive");

if miner_fee < min_fee {
return Err(Error::FeeBelowMinimumRate);
}

Expand Down
Loading