Stay interested when the peer has pieces we don't have

diff --git a/requesting.go b/requesting.go
index b70f2645e990b234b28703ab64927d42ae31d1a9..fdb0ad79109feff0383e3df15099460d0098741e 100644 (file)
--- a/requesting.go
+++ b/requesting.go
@@ -9,6 +9,7 @@ import (
        "time"
        "unsafe"
 
+       "github.com/RoaringBitmap/roaring"
        "github.com/anacrolix/generics/heap"
        "github.com/anacrolix/log"
        "github.com/anacrolix/multiless"
@@ -248,9 +249,31 @@ func (p *Peer) maybeUpdateActualRequestState() {
        )
 }
 
+// Whether we should allow sending not interested ("losing interest") to the peer. I noticed
+// qBitTorrent seems to punish us for sending not interested when we're streaming and don't
+// currently need anything.
+func (p *Peer) allowSendNotInterested() bool {
+       // Except for caching, we're not likely to lose pieces very soon.
+       if p.t.haveAllPieces() {
+               return true
+       }
+       all, known := p.peerHasAllPieces()
+       if all || !known {
+               return false
+       }
+       // Allow losing interest if we have all the pieces the peer has.
+       return roaring.AndNot(p.peerPieces(), &p.t._completedPieces).IsEmpty()
+}
+
 // Transmit/action the request state to the peer.
 func (p *Peer) applyRequestState(next desiredRequestState) {
        current := &p.requestState
+       // Make interest sticky
+       if !next.Interested && p.requestState.Interested {
+               if !p.allowSendNotInterested() {
+                       next.Interested = true
+               }
+       }
        if !p.setInterested(next.Interested) {
                return
        }