From: Matt Joiner <anacrolix@gmail.com>
Date: Mon, 25 Oct 2021 02:00:56 +0000 (+1100)
Subject: Fix panic when sustaining unrejected requests after being choked
X-Git-Tag: v1.34.0^2~12
X-Git-Url: http://www.git.stargrave.org/?a=commitdiff_plain;h=e884b8079b6b5863d4dd9c2f9d8cab119ebeb525;p=btrtrc.git

Fix panic when sustaining unrejected requests after being choked

Fixes https://github.com/anacrolix/torrent/issues/680.
---

diff --git a/peerconn.go b/peerconn.go
index 005c6b7d..c1b98c2a 100644
--- a/peerconn.go
+++ b/peerconn.go
@@ -556,6 +556,8 @@ func (pc *PeerConn) writeInterested(interested bool) bool {
 // are okay.
 type messageWriter func(pp.Message) bool
 
+// This function seems to only used by Peer.request. It's all logic checks, so maybe we can no-op it
+// when we want to go fast.
 func (cn *Peer) shouldRequest(r RequestIndex) error {
 	pi := pieceIndex(r / cn.t.chunksPerRegularPiece())
 	if !cn.peerHasPiece(pi) {
@@ -574,7 +576,11 @@ func (cn *Peer) shouldRequest(r RequestIndex) error {
 		panic("piece is queued for hash")
 	}
 	if cn.peerChoking && !cn.peerAllowedFast.Contains(bitmap.BitIndex(pi)) {
-		panic("peer choking and piece not allowed fast")
+		// This could occur if we made a request with the fast extension, and then got choked and
+		// haven't had the request rejected yet.
+		if !cn.actualRequestState.Requests.Contains(r) {
+			panic("peer choking and piece not allowed fast")
+		}
 	}
 	return nil
 }
diff --git a/requesting.go b/requesting.go
index 6d707fde..1d2d5e19 100644
--- a/requesting.go
+++ b/requesting.go
@@ -216,8 +216,12 @@ func (p *Peer) getDesiredRequestState() (desired requestState) {
 			allowedFast := p.peerAllowedFast.ContainsInt(pieceIndex)
 			rsp.IterPendingChunks.Iter(func(ci request_strategy.ChunkIndex) {
 				if !allowedFast {
-					// We must signal interest to request this..
+					// We must signal interest to request this
 					desired.Interested = true
+					// We can make or will allow sustaining a request here if we're not choked, or
+					// have made the request previously (presumably while unchoked), and haven't had
+					// the peer respond yet (and the request was retained because we are using the
+					// fast extension).
 					if p.peerChoking && !p.actualRequestState.Requests.Contains(ci) {
 						// We can't request this right now.
 						return