Why is LPD not enabled by default in Transmission?

Question

Since version 2.00, Transmission has Local Peer Discovery feature, which seems quite useful. I was surprised that it wasn't enabled by default though, so I became concerned about any potential issues it might have.

Solution 1

As far as I could investigate there are not major issues with the LPD feature, but maybe the reason on this issue tracker ticket.

Solution 2

Check this comment from project issue tracker:

There needs to be a manual toggle to enable/disable the feature globally, and it MUST default to disabled. Please let me justify this last requirement. The local peer discovery code broadcasts the set of torrents you're participating in every four minutes. Anyone on the same link as you (your neighbour, your mom, your wee brother) can find out the set of torrents just by listening on the right multicast group, and these are the very people you might not want to know about what your are downloading. Hence, I insist on this being DISABLED by default.

Comments

[Wowfunhappy]

This really, really ought to be explained in a tooltip. No point in disabling it by default if you don't also warn users about the dangers of enabling.

[Alexander]

To be clear, the Local Service Discovery protocol only broadcasts your torrents' info hashes, and not your torrents' names. The torrent name is one of the things "mixed in" to the info hash, but it can't be retrieved back from the info hash. Thus, someone can identify your torrent only if they already have that exact torrent. They would compute their torrent's info hash, see that it matches the one you broadcast, and conclude that you have the same torrent as them. Indeed, that's the whole point of local peer discovery.