In-place seeding: how?

[nojacko]

I've been doing some research into reseeding of old torrents myself and came across a bitmagnet. I'm curious how the future "In-place seeding" feature is going to work?

From what I can gather, this is only really possible with torrents that have a single file as their pieces hashes can be directly calculated from that file and matched. I have this working in a prototype.

Once you have multiple files in a torrent, tracking down the files is no so easy as the pieces hash take the torrent as a whole and the hashes cross the boundaries of files. If you're missing one file, you cannot simply recreate the pieces hashes to match files to torrents.

Hopefully I'm missing something because I'd love to be able to reseed everything I have.

[zypA13510]

Some torrents may include a hash per file: "sha1" is supported by libtorrent^[1], and BitTorrent v2 introduced per-file hash^[2]. Some torrent creators might use paddings^[3] to separate every file into whole pieces.

Just my speculations, as we are talking about a feature that does not exist yet.

[nojacko]

Thanks for the comment.

v2 torrents are perfect for this as you don't even need to seed a the original torrent. You can effectively take loads of files, create a new torrent and any v2 torrent with any of those files could pick them up. Unfortunately, after crawling 2 million torrents in with my own DHT crawler I've yet to find one.

I wasn't aware that some include a hash within each file. it's not something I've seen on the torrents I've inspected. I'll have to do some more digging into that now I know.

I was curious if the dev had any more detailed plans in their head since they have the plan to include it as a future feature.

[zypA13510]

It is not very common. I dug through some 30 torrent files, and the only one I found used an unsupported "filehash" instead of "sha1".

[ireun]

bitmagnet Will not find any V2 hashes currently

[nojacko]

The 2 million I crawled weren't with bitmagnet. V2 is just not popular when it really should be as it's improves everything.