tiamak/salvium-rs
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Fix sweep fee_too_low: replace single rebuild with convergence loop

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The rebuild step could produce a TX with slightly different weight than
  the first build (signing randomness), leaving the fee short. Now loops
  until fee >= weight * fee_per_byte, converging in 1-2 iterations.
This commit is contained in:
Matt Hess
2026-03-01 22:10:08 +00:00
parent d61834be1f
commit 0d2887175a
1 changed files with 23 additions and 49 deletions
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crates/salvium-ffi/src/transfer.rs
+23 -49
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@@ -920,51 +920,19 @@ pub async fn build_sign_maybe_broadcast(
(keys.cn.spend_public_key, keys.cn.view_public_key)
};
// Clone inputs before first build (builder consumes them).
let inputs_for_rebuild = prepared_inputs.clone();
// Inputs are cloned on each loop iteration (builder consumes them).
let inputs_for_rebuild = prepared_inputs;
// --- First pass: build with estimated fee to measure actual blob size ---
let mut builder = TransactionBuilder::new()
.add_inputs(prepared_inputs)
.set_change_address(chg_spend, chg_view)
.set_tx_type(tt)
.set_fee(initial_fee)
.set_unlock_time(unlock_time)
.set_priority(priority)
.set_asset_types(asset_type, asset_type)
.set_rct_type(fork_rct_type);
if is_carrot {
builder = builder.set_change_view_balance_secret(keys.carrot.view_balance_secret);
}
if amount_burnt > 0 {
builder = builder.set_amount_burnt(amount_burnt);
}
for dest in destinations {
builder = builder.add_destination(dest.clone());
}
let first_unsigned = builder.build().map_err(|e| format!("transaction build failed: {e}"))?;
let first_signed = salvium_tx::sign_transaction(first_unsigned)
.map_err(|e| format!("transaction signing failed: {e}"))?;
let first_bytes = first_signed.to_bytes().map_err(|e| format!("tx serialize failed: {e}"))?;
let actual_weight = first_bytes.len() as u64;
let exact_fee = fee::calculate_fee_from_weight(fee_per_byte, actual_weight);
// --- Second pass (if needed): rebuild with exact fee ---
let (signed, tx_bytes, actual_fee, weight) = if exact_fee != initial_fee {
log::info!(
"FEE REBUILD: initial_fee={} exact_fee={} delta={} (actual_weight={}, estimated={})",
initial_fee,
exact_fee,
initial_fee as i64 - exact_fee as i64,
actual_weight,
estimated_weight,
);
// Build-measure-rebuild loop: each build may produce a slightly different
// weight (signing randomness, varint encoding), so we loop until the fee
// covers the actual blob. Converges in 1-2 iterations.
let mut current_fee = initial_fee;
let (signed, tx_bytes, actual_fee, weight) = loop {
let mut builder = TransactionBuilder::new()
.add_inputs(inputs_for_rebuild)
.add_inputs(inputs_for_rebuild.clone())
.set_change_address(chg_spend, chg_view)
.set_tx_type(tt)
.set_fee(exact_fee)
.set_fee(current_fee)
.set_unlock_time(unlock_time)
.set_priority(priority)
.set_asset_types(asset_type, asset_type)
@@ -979,17 +947,23 @@ pub async fn build_sign_maybe_broadcast(
builder = builder.add_destination(dest.clone());
}
let unsigned =
builder.build().map_err(|e| format!("transaction build failed (rebuild): {e}"))?;
let unsigned = builder.build().map_err(|e| format!("transaction build failed: {e}"))?;
let fee = unsigned.fee;
let signed = salvium_tx::sign_transaction(unsigned)
.map_err(|e| format!("transaction signing failed (rebuild): {e}"))?;
let tx_bytes =
signed.to_bytes().map_err(|e| format!("tx serialize failed (rebuild): {e}"))?;
.map_err(|e| format!("transaction signing failed: {e}"))?;
let tx_bytes = signed.to_bytes().map_err(|e| format!("tx serialize failed: {e}"))?;
let w = tx_bytes.len() as u64;
(signed, tx_bytes, fee, w)
} else {
(first_signed, first_bytes, initial_fee, actual_weight)
let fee_needed = fee::calculate_fee_from_weight(fee_per_byte, w);
log::info!(
"FEE LOOP: fee={} weight={} fee_needed={} (estimated_weight={} initial_fee={})",
fee, w, fee_needed, estimated_weight, initial_fee,
);
if fee >= fee_needed {
break (signed, tx_bytes, fee, w);
}
current_fee = fee_needed;
};
// 4. Final serialization.