Subject: Re: [bitcoindev] Libre Relay v27.1 released with lower 1.25x replacement threshold

From: Peter Todd <[email-masked]>
Date: Sat, 22 Jun 2024 14:29:43 +0000

On Thu, Jun 20, 2024 at 10:33:46PM +0000, Peter Todd wrote:
> On Thu, Jun 20, 2024 at 04:33:47PM +0000, Peter Todd wrote:
> > Libre Relay/RBFR is already mitigating transaction pinning in the real world.
> > I've personally run into a few cases with LND nodes where anchor outputs were
> > spent after the 16 block CSV timeout by third parties in a large transaction
> > that the LND node was not aware of, leading to LND creating a conflicting,
> > higher-fee, transaction spending the anchor output and other outputs. Normally
> > the conflict would fail to get mined due to the higher absolute fee pin. But in
> > each case after propagation via Libre Relay nodes, F2Pool eventually mined the
> > higher fee-rate transaction after a few hours; I suspect F2Pool has an unusual
> > short mempool expiration time. Lightning node operators should consider running
> > Libre Relay for this purpose, as the existing Lightning protocol does have some
> > pinning vulnerabilities.
> 
> Here's a real world example of this pinning situation being resolved by RBFR,

...and we have yet another example of this same pinning situation, involving a
totally different Lightning node. This time the RBFR transaction was bumped one
more time with RBF before getting mined. But both transactions were still less
total fees than the pin tx:

2024-06-21T19:25:10Z [mempool] replacing tx 68b813b844e4160227e4e73573c23321d77b9fd2b4fe701b6a2a2a12309db020 (wtxid=08950f68152f7890f52a7f4029a89b54b26e7c575dd7c8eb5bf2910b7c13cbcb) with 4664cb8e556b1c673dbea7cbdc77c5ad29cfbf0e9a439d1b51874e2161f3edcc (wtxid=a63305ccd136f2b613f9add2b293c6d4eb20b0eca3271e687445b749aa9b7e69) for -0.0049018 additional fees, -98471 delta bytes
2024-06-21T19:25:10Z [mempool] AcceptToMemoryPool: peer=454: accepted 4664cb8e556b1c673dbea7cbdc77c5ad29cfbf0e9a439d1b51874e2161f3edcc (wtxid=a63305ccd136f2b613f9add2b293c6d4eb20b0eca3271e687445b749aa9b7e69) (poolsz 103582 txn, 283345 kB)

2024-06-21T22:13:09Z [mempool] replacing tx 4664cb8e556b1c673dbea7cbdc77c5ad29cfbf0e9a439d1b51874e2161f3edcc (wtxid=a63305ccd136f2b613f9add2b293c6d4eb20b0eca3271e687445b749aa9b7e69) with 4f6ed6c3fe25571b883a631503ab84cccef450b96d8c9065c712246758e15e6b (wtxid=7a465ba70b8f8d983aad594530751e9c17be77b3dac11275ade213ceccad997e) for 0.00003035 additional fees, 0 delta bytes
2024-06-21T22:13:09Z [mempool] AcceptToMemoryPool: peer=41398: accepted 4f6ed6c3fe25571b883a631503ab84cccef450b96d8c9065c712246758e15e6b (wtxid=7a465ba70b8f8d983aad594530751e9c17be77b3dac11275ade213ceccad997e) (poolsz 92468 txn, 273091 kB)

Again, it was F2Pool that fixed the problem.

-- 
https://petertodd.org 'peter'[:-1]@petertodd.org

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