With peerblockfilters=1 hundreds of "btcwire 0.5.0/neutrino" connections are downloading TB from my Bitcoin node

Question

I run Bitcoin Core 0.21.0 from a data center, unmetered, with compact block filters enabled (blockfilterindex=1 peerblockfilters=1).

Soon after the restart, I get a huge number (140-200) of connections identifying as btcwire 0.5.0/neutrino, from all over the world. They are responsible for vast majority of download bandwidth (90%+).

This only happens when node is signalling CBF support via peerblockfilters=1.

I am aware "Neutrino" is a proof-of-concept light wallet using CBF but it doesn't explain neither the vast dominance in terms of connections number (~75%), nor in terms of bandwidth (90%+).

Incidentally, "Neutrino" is also a surveillance company owned by Coinbase :)

Any guidance is welcome!

Answer 1

It appears that btcwire is the Bitcoin p2p module of btcd and neutrino is Lightning Labs's implementation of BIP157/158 (compact client-side block filters (CBF)). I suspect that the agent identifier btcwire 0.5.0/neutrino indicates LND (Lightning Network Daemon) instances which are configured to allow or prefer CBF for synchronization. Given your experience and since CBF support was only added to Bitcoin Core in 0.21.0, it looks like the demand for the CBF network service far outstrips the few listening nodes that provide the CBF network service at this time.

I expect that the load will be distributed better as more Bitcoin Core 0.21.0 listening nodes come online.