Bitcoin Core bumpfee with descendants in mempool

CardCoins

jr. member

Activity: 31

Merit: 14

Quote from: HCP on August 18, 2020, 05:05:49 PM

Quote from: CardCoins on August 18, 2020, 02:48:05 PM

As mentioned, bumpfee won't let you do this, but if you do attempt it with a raw transaction, note that you will have to bump the fee relative to the entire package of transactions. So if you are bumping the fee of a transaction with a lot of descendants, you will need to calculate the total package size in bytes, then bump the fee accordingly.

Are you thinking of CPFP (Child-Pays-For-Parent)? Huh

If so, that works the other way... when you're trying to get one of the descendants confirmed quickly, you have to take into account all of the ascendants.

ie. if you have the following chain of transactions: TransA -> TransB -> TransC -> TransD -> TransE

And you bumpfee on TransA... then B, C, D and E will become invalid as the hash of TransA will change, making B invalid.

If you're wanting to get TransE confirmed quickly, then you would need to take A, B, C & D into account as well, to make sure that the fees are big enough for miners to want to get all 5 transactions included in a block.

Are you familiar with RBF pinning? This is a good explanation of the issue I have described. CPFP is subject to the same principle. If I could just kick out transactions w/ descendants from the mempool without paying for the full package that would be a DoS attack of sorts. Unfortunately it can also be turned on its head to "stick" transactions.

https://bitcoinops.org/en/topics/transaction-pinning/

HCP

legendary

Activity: 2086

Merit: 4361

Quote from: CardCoins on August 18, 2020, 02:48:05 PM

As mentioned, bumpfee won't let you do this, but if you do attempt it with a raw transaction, note that you will have to bump the fee relative to the entire package of transactions. So if you are bumping the fee of a transaction with a lot of descendants, you will need to calculate the total package size in bytes, then bump the fee accordingly.

Are you thinking of CPFP (Child-Pays-For-Parent)? Huh

If so, that works the other way... when you're trying to get one of the descendants confirmed quickly, you have to take into account all of the ascendants.

ie. if you have the following chain of transactions: TransA -> TransB -> TransC -> TransD -> TransE

And you bumpfee on TransA... then B, C, D and E will become invalid as the hash of TransA will change, making B invalid.

If you're wanting to get TransE confirmed quickly, then you would need to take A, B, C & D into account as well, to make sure that the fees are big enough for miners to want to get all 5 transactions included in a block.

CardCoins

jr. member

Activity: 31

Merit: 14

As mentioned, bumpfee won't let you do this, but if you do attempt it with a raw transaction, note that you will have to bump the fee relative to the entire package of transactions. So if you are bumping the fee of a transaction with a lot of descendants, you will need to calculate the total package size in bytes, then bump the fee accordingly.

nc50lc

legendary

Activity: 2534

Merit: 6080

Self-proclaimed Genius

Quote from: Nergon on August 13, 2020, 01:18:25 PM

I tried it today. It works fine with sendrawtransaction. You only get a txn-mempool-conflict if Replace by fee is disabled.

Sorry, sendrawtransaction indeed works.
Seems like I have used the wrong UTXO on my previous test.
The previous transaction and its descendants were automatically booted out of the node's mempool.

Nergon

newbie

Activity: 14

Merit: 7

Quote from: nc50lc on August 13, 2020, 07:26:33 AM

Quote from: Nergon on August 13, 2020, 07:04:27 AM

Can you bump the fee manually with sendrawtransaction?

After manually creating a replacement signed raw transaction?
You will probably get "txn-mempool-conflict" due to the same reason achow101 explained above (I've only tested in on regtest).

But sending that RAW transaction through other clients might work as long as the to-be-replaced transaction is RBF.

I tried it today. It works fine with sendrawtransaction. You only get a txn-mempool-conflict if Replace by fee is disabled.

nc50lc

legendary

Activity: 2534

Merit: 6080

Self-proclaimed Genius

Quote from: Nergon on August 13, 2020, 07:04:27 AM

Can you bump the fee manually with sendrawtransaction?

After manually creating a replacement signed raw transaction?
You will probably get "txn-mempool-conflict" due to the same reason achow101 explained above (I've only tested in on regtest).

But sending that RAW transaction through other clients might work as long as the to-be-replaced transaction is RBF.

Nergon

newbie

Activity: 14

Merit: 7

Quote from: achow101 on August 12, 2020, 02:03:36 PM

Quote from: Nergon on August 12, 2020, 11:35:35 AM

Oh interesting. Why can you do it on Wallets like Electrum if its not allowed?

It's not disallowed by the network. It's just disallowed by Bitcoin Core's bumpfee functionality.

Can you bump the fee manually with sendrawtransaction?

achow101

staff

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Just writing some code

Quote from: Nergon on August 12, 2020, 11:35:35 AM

Oh interesting. Why can you do it on Wallets like Electrum if its not allowed?

It's not disallowed by the network. It's just disallowed by Bitcoin Core's bumpfee functionality.

Nergon

newbie

Activity: 14

Merit: 7

Quote from: achow101 on August 12, 2020, 11:20:17 AM

No, it is not.

If a transaction has descendants, that means that there are transactions that spend its outputs. Bumping the fee on that transaction will change the txid of that transaction and invalidate those descendant transactions. Thus bumpfee is disallowed on transactions with descendants.

Oh interesting. Why can you do it on Wallets like Electrum if its not allowed?

achow101

staff

Activity: 3458

Merit: 6793

Just writing some code

No, it is not.

If a transaction has descendants, that means that there are transactions that spend its outputs. Bumping the fee on that transaction will change the txid of that transaction and invalidate those descendant transactions. Thus bumpfee is disallowed on transactions with descendants.

Nergon

newbie

Activity: 14

Merit: 7

Hello,
Is it possible to use the bumpfee command if there are descendants in the mempool? Currently Bitcoin Core 0.20.0 always prints following error:

Code:

error code: -8
error message:
Transaction has descendants in the mempool

Is there a way to still do a replace by fee? How does it work?

Topic: Bitcoin Core bumpfee with descendants in mempool (Read 190 times)