Implement BEP 27 (private torrents)#1053
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Honors the `private=1` flag in torrent metainfo per BEP 27. Private
torrents must not be advertised on, or receive peers from, any
decentralized discovery mechanism — only the trackers explicitly
listed in the metainfo. Previously the field was parsed into
metainfo.Info.Private but never checked at runtime, so private
trackers' workflow was silently leaking peers via DHT/PEX/LSD.
This change adds a single helper, Torrent.isPrivate(), and consults
it at every existing discovery gate:
torrent.go
isPrivate() — returns true iff info is loaded and Private==true.
Returns false when info is not yet loaded (magnet still fetching
metadata). The downstream loops re-check each iteration so the
flag takes effect as soon as metadata arrives.
torrent.go: dhtAnnouncer
Skips DHT announce when private. Re-checked per loop so a magnet
that turns out to be private stops announcing immediately after
info loads.
pexconn.go: pexConnState.Init
PEX is not enabled for private torrents — the connection still
works, just doesn't share peer lists.
client.go: TorrentInfohashesAndPort
Excludes private torrents from the Local Peer Discovery (BEP 14)
multicast announce.
client.go: OnLPDAnnouncement
Inbound LPD peers are not added to private torrents, including
via the "add to all other torrents" fallback path.
client.go: AddTorrentOpt
Skips the post-add lpdPeers / lpdForce kick when the torrent is
private.
bep27_private_test.go
Covers the helper's behaviour for the four meaningful input states:
no info, Private==nil, Private==&false, Private==&true. The
per-gate behaviour is exercised by the existing integration tests
(./test/...) which still pass on every public-torrent path.
All existing tests pass (storage/possum fails locally due to a
missing native libpossum on Windows — unrelated to this change).
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Honors the `private=1` flag in torrent metainfo per BEP 27. Previously `metainfo.Info.Private` was parsed but never checked at runtime, so private trackers' workflow was silently leaking peers via DHT, PEX, and LSD.
What changed
Adds a single helper `Torrent.isPrivate()` and consults it at every existing decentralized-discovery gate:
Magnet edge case
`isPrivate()` returns false when info has not yet been loaded (e.g. a magnet still fetching metadata). The downstream loops re-check each iteration, so the moment metadata arrives the flag takes effect. This is the only safe behaviour — we physically cannot honour a private flag we don't yet have. In practice private trackers distribute `.torrent` files (not magnets) because of this race.
Tests
`bep27_private_test.go` covers the four meaningful states of the helper: no info, `Private==nil`, `Private==&false`, `Private==&true`.
Per-gate behaviour is exercised by the existing integration suite (`./test/...`), which still passes on every public-torrent path. `storage/possum` fails locally on Windows due to missing native `libpossum` — unrelated to this change.
Spec reference