]> Sergey Matveev's repositories - btrtrc.git/blobdiff - torrent.go
Drop support for go 1.20
[btrtrc.git] / torrent.go
index 7d32b957c88a42a40b8dd73bcc7f740fea584500..6385a3fc026f9a2474ddc029908ef236ab30713a 100644 (file)
@@ -22,6 +22,7 @@ import (
        "github.com/anacrolix/chansync/events"
        "github.com/anacrolix/dht/v2"
        . "github.com/anacrolix/generics"
+       g "github.com/anacrolix/generics"
        "github.com/anacrolix/log"
        "github.com/anacrolix/missinggo/perf"
        "github.com/anacrolix/missinggo/slices"
@@ -30,18 +31,21 @@ import (
        "github.com/anacrolix/missinggo/v2/pubsub"
        "github.com/anacrolix/multiless"
        "github.com/anacrolix/sync"
-       request_strategy "github.com/anacrolix/torrent/request-strategy"
-       typedRoaring "github.com/anacrolix/torrent/typed-roaring"
-       "github.com/davecgh/go-spew/spew"
        "github.com/pion/datachannel"
+       "golang.org/x/exp/maps"
 
        "github.com/anacrolix/torrent/bencode"
        "github.com/anacrolix/torrent/common"
+       "github.com/anacrolix/torrent/internal/check"
+       "github.com/anacrolix/torrent/internal/nestedmaps"
        "github.com/anacrolix/torrent/metainfo"
        pp "github.com/anacrolix/torrent/peer_protocol"
+       utHolepunch "github.com/anacrolix/torrent/peer_protocol/ut-holepunch"
+       request_strategy "github.com/anacrolix/torrent/request-strategy"
        "github.com/anacrolix/torrent/segments"
        "github.com/anacrolix/torrent/storage"
        "github.com/anacrolix/torrent/tracker"
+       typedRoaring "github.com/anacrolix/torrent/typed-roaring"
        "github.com/anacrolix/torrent/webseed"
        "github.com/anacrolix/torrent/webtorrent"
 )
@@ -101,14 +105,14 @@ type Torrent struct {
        maxEstablishedConns int
        // Set of addrs to which we're attempting to connect. Connections are
        // half-open until all handshakes are completed.
-       halfOpen map[string]PeerInfo
+       halfOpen map[string]map[outgoingConnAttemptKey]*PeerInfo
 
        // Reserve of peers to connect to. A peer can be both here and in the
        // active connections if were told about the peer after connecting with
        // them. That encourages us to reconnect to peers that are well known in
        // the swarm.
        peers prioritizedPeers
-       // Whether we want to know to know more peers.
+       // Whether we want to know more peers.
        wantPeersEvent missinggo.Event
        // An announcer for each tracker URL.
        trackerAnnouncers map[string]torrentTrackerAnnouncer
@@ -168,6 +172,8 @@ type Torrent struct {
        requestIndexes     []RequestIndex
 }
 
+type outgoingConnAttemptKey = *PeerInfo
+
 func (t *Torrent) length() int64 {
        return t._length.Value
 }
@@ -232,8 +238,10 @@ func (t *Torrent) KnownSwarm() (ks []PeerInfo) {
        })
 
        // Add half-open peers to the list
-       for _, peer := range t.halfOpen {
-               ks = append(ks, peer)
+       for _, attempts := range t.halfOpen {
+               for _, peer := range attempts {
+                       ks = append(ks, *peer)
+               }
        }
 
        // Add active peers to the list
@@ -535,7 +543,7 @@ func (t *Torrent) setMetadataSize(size int) (err error) {
                return
        }
        if uint32(size) > maxMetadataSize {
-               return errors.New("bad size")
+               return log.WithLevel(log.Warning, errors.New("bad size"))
        }
        if len(t.metadataBytes) == size {
                return
@@ -756,23 +764,40 @@ func (t *Torrent) writeStatus(w io.Writer) {
 
        fmt.Fprintf(w, "DHT Announces: %d\n", t.numDHTAnnounces)
 
-       spew.NewDefaultConfig()
-       spew.Fdump(w, t.statsLocked())
-
-       peers := t.peersAsSlice()
-       sort.Slice(peers, func(_i, _j int) bool {
-               i := peers[_i]
-               j := peers[_j]
-               if less, ok := multiless.New().EagerSameLess(
-                       i.downloadRate() == j.downloadRate(), i.downloadRate() < j.downloadRate(),
-               ).LessOk(); ok {
-                       return less
-               }
-               return worseConn(i, j)
+       dumpStats(w, t.statsLocked())
+
+       fmt.Fprintf(w, "webseeds:\n")
+       t.writePeerStatuses(w, maps.Values(t.webSeeds))
+
+       peerConns := maps.Keys(t.conns)
+       // Peers without priorities first, then those with. I'm undecided about how to order peers
+       // without priorities.
+       sort.Slice(peerConns, func(li, ri int) bool {
+               l := peerConns[li]
+               r := peerConns[ri]
+               ml := multiless.New()
+               lpp := g.ResultFromTuple(l.peerPriority()).ToOption()
+               rpp := g.ResultFromTuple(r.peerPriority()).ToOption()
+               ml = ml.Bool(lpp.Ok, rpp.Ok)
+               ml = ml.Uint32(rpp.Value, lpp.Value)
+               return ml.Less()
        })
-       for i, c := range peers {
-               fmt.Fprintf(w, "%2d. ", i+1)
-               c.writeStatus(w, t)
+
+       fmt.Fprintf(w, "%v peer conns:\n", len(peerConns))
+       t.writePeerStatuses(w, g.SliceMap(peerConns, func(pc *PeerConn) *Peer {
+               return &pc.Peer
+       }))
+}
+
+func (t *Torrent) writePeerStatuses(w io.Writer, peers []*Peer) {
+       var buf bytes.Buffer
+       for _, c := range peers {
+               fmt.Fprintf(w, "- ")
+               buf.Reset()
+               c.writeStatus(&buf)
+               w.Write(bytes.TrimRight(
+                       bytes.ReplaceAll(buf.Bytes(), []byte("\n"), []byte("\n  ")),
+                       " "))
        }
 }
 
@@ -805,7 +830,10 @@ func (t *Torrent) newMetaInfo() metainfo.MetaInfo {
        }
 }
 
-// Get bytes left
+// Returns a count of bytes that are not complete in storage, and not pending being written to
+// storage. This value is from the perspective of the download manager, and may not agree with the
+// actual state in storage. If you want read data synchronously you should use a Reader. See
+// https://github.com/anacrolix/torrent/issues/828.
 func (t *Torrent) BytesMissing() (n int64) {
        t.cl.rLock()
        n = t.bytesMissingLocked()
@@ -889,17 +917,21 @@ func (t *Torrent) close(wg *sync.WaitGroup) (err error) {
        if t.storage != nil {
                t.deletePieceRequestOrder()
        }
+       t.assertAllPiecesRelativeAvailabilityZero()
+       t.pex.Reset()
+       t.cl.event.Broadcast()
+       t.pieceStateChanges.Close()
+       t.updateWantPeersEvent()
+       return
+}
+
+func (t *Torrent) assertAllPiecesRelativeAvailabilityZero() {
        for i := range t.pieces {
                p := t.piece(i)
                if p.relativeAvailability != 0 {
                        panic(fmt.Sprintf("piece %v has relative availability %v", i, p.relativeAvailability))
                }
        }
-       t.pex.Reset()
-       t.cl.event.Broadcast()
-       t.pieceStateChanges.Close()
-       t.updateWantPeersEvent()
-       return
 }
 
 func (t *Torrent) requestOffset(r Request) int64 {
@@ -1028,7 +1060,7 @@ func (t *Torrent) havePiece(index pieceIndex) bool {
 func (t *Torrent) maybeDropMutuallyCompletePeer(
        // I'm not sure about taking peer here, not all peer implementations actually drop. Maybe that's
        // okay?
-       p *Peer,
+       p *PeerConn,
 ) {
        if !t.cl.config.DropMutuallyCompletePeers {
                return
@@ -1042,7 +1074,7 @@ func (t *Torrent) maybeDropMutuallyCompletePeer(
        if p.useful() {
                return
        }
-       t.logger.WithDefaultLevel(log.Debug).Printf("dropping %v, which is mutually complete", p)
+       p.logger.Levelf(log.Debug, "is mutually complete; dropping")
        p.drop()
 }
 
@@ -1081,17 +1113,26 @@ func getPeerConnSlice(cap int) []*PeerConn {
        }
 }
 
-// The worst connection is one that hasn't been sent, or sent anything useful for the longest. A bad
-// connection is one that usually sends us unwanted pieces, or has been in the worse half of the
-// established connections for more than a minute. This is O(n log n). If there was a way to not
-// consider the position of a conn relative to the total number, it could be reduced to O(n).
-func (t *Torrent) worstBadConn() (ret *PeerConn) {
-       wcs := worseConnSlice{conns: t.appendUnclosedConns(getPeerConnSlice(len(t.conns)))}
-       defer peerConnSlices.Put(wcs.conns)
-       wcs.initKeys()
+// Calls the given function with a slice of unclosed conns. It uses a pool to reduce allocations as
+// this is a frequent occurrence.
+func (t *Torrent) withUnclosedConns(f func([]*PeerConn)) {
+       sl := t.appendUnclosedConns(getPeerConnSlice(len(t.conns)))
+       f(sl)
+       peerConnSlices.Put(sl)
+}
+
+func (t *Torrent) worstBadConnFromSlice(opts worseConnLensOpts, sl []*PeerConn) *PeerConn {
+       wcs := worseConnSlice{conns: sl}
+       wcs.initKeys(opts)
        heap.Init(&wcs)
        for wcs.Len() != 0 {
                c := heap.Pop(&wcs).(*PeerConn)
+               if opts.incomingIsBad && !c.outgoing {
+                       return c
+               }
+               if opts.outgoingIsBad && c.outgoing {
+                       return c
+               }
                if c._stats.ChunksReadWasted.Int64() >= 6 && c._stats.ChunksReadWasted.Int64() > c._stats.ChunksReadUseful.Int64() {
                        return c
                }
@@ -1107,6 +1148,17 @@ func (t *Torrent) worstBadConn() (ret *PeerConn) {
        return nil
 }
 
+// The worst connection is one that hasn't been sent, or sent anything useful for the longest. A bad
+// connection is one that usually sends us unwanted pieces, or has been in the worse half of the
+// established connections for more than a minute. This is O(n log n). If there was a way to not
+// consider the position of a conn relative to the total number, it could be reduced to O(n).
+func (t *Torrent) worstBadConn(opts worseConnLensOpts) (ret *PeerConn) {
+       t.withUnclosedConns(func(ucs []*PeerConn) {
+               ret = t.worstBadConnFromSlice(opts, ucs)
+       })
+       return
+}
+
 type PieceStateChange struct {
        Index int
        PieceState
@@ -1294,6 +1346,15 @@ func (t *Torrent) numReceivedConns() (ret int) {
        return
 }
 
+func (t *Torrent) numOutgoingConns() (ret int) {
+       for c := range t.conns {
+               if c.outgoing {
+                       ret++
+               }
+       }
+       return
+}
+
 func (t *Torrent) maxHalfOpen() int {
        // Note that if we somehow exceed the maximum established conns, we want
        // the negative value to have an effect.
@@ -1301,13 +1362,16 @@ func (t *Torrent) maxHalfOpen() int {
        extraIncoming := int64(t.numReceivedConns() - t.maxEstablishedConns/2)
        // We want to allow some experimentation with new peers, and to try to
        // upset an oversupply of received connections.
-       return int(min(max(5, extraIncoming)+establishedHeadroom, int64(t.cl.config.HalfOpenConnsPerTorrent)))
+       return int(min(
+               max(5, extraIncoming)+establishedHeadroom,
+               int64(t.cl.config.HalfOpenConnsPerTorrent),
+       ))
 }
 
 func (t *Torrent) openNewConns() (initiated int) {
        defer t.updateWantPeersEvent()
        for t.peers.Len() != 0 {
-               if !t.wantConns() {
+               if !t.wantOutgoingConns() {
                        return
                }
                if len(t.halfOpen) >= t.maxHalfOpen() {
@@ -1320,7 +1384,15 @@ func (t *Torrent) openNewConns() (initiated int) {
                        return
                }
                p := t.peers.PopMax()
-               t.initiateConn(p)
+               opts := outgoingConnOpts{
+                       peerInfo:                 p,
+                       t:                        t,
+                       requireRendezvous:        false,
+                       skipHolepunchRendezvous:  false,
+                       receivedHolepunchConnect: false,
+                       HeaderObfuscationPolicy:  t.cl.config.HeaderObfuscationPolicy,
+               }
+               initiateConn(opts, false)
                initiated++
        }
        return
@@ -1498,7 +1570,7 @@ func (t *Torrent) decPeerPieceAvailability(p *Peer) {
 }
 
 func (t *Torrent) assertPendingRequests() {
-       if !check {
+       if !check.Enabled {
                return
        }
        // var actual pendingRequests
@@ -1533,7 +1605,7 @@ func (t *Torrent) wantPeers() bool {
        if t.peers.Len() > t.cl.config.TorrentPeersLowWater {
                return false
        }
-       return t.wantConns()
+       return t.wantOutgoingConns()
 }
 
 func (t *Torrent) updateWantPeersEvent() {
@@ -1614,7 +1686,7 @@ func (t *Torrent) onWebRtcConn(
 func (t *Torrent) logRunHandshookConn(pc *PeerConn, logAll bool, level log.Level) {
        err := t.cl.runHandshookConn(pc, t)
        if err != nil || logAll {
-               t.logger.WithDefaultLevel(level).Printf("error running handshook conn: %v", err)
+               t.logger.WithDefaultLevel(level).Levelf(log.ErrorLevel(err), "error running handshook conn: %v", err)
        }
 }
 
@@ -1646,10 +1718,9 @@ func (t *Torrent) startScrapingTracker(_url string) {
        }
        u, err := url.Parse(_url)
        if err != nil {
-               // URLs with a leading '*' appear to be a uTorrent convention to
-               // disable trackers.
+               // URLs with a leading '*' appear to be a uTorrent convention to disable trackers.
                if _url[0] != '*' {
-                       log.Str("error parsing tracker url").AddValues("url", _url).Log(t.logger)
+                       t.logger.Levelf(log.Warning, "error parsing tracker url: %v", err)
                }
                return
        }
@@ -1806,7 +1877,7 @@ func (t *Torrent) dhtAnnouncer(s DhtServer) {
                        // We're also announcing ourselves as a listener, so we don't just want peer addresses.
                        // TODO: We can include the announce_peer step depending on whether we can receive
                        // inbound connections. We should probably only announce once every 15 mins too.
-                       if !t.wantConns() {
+                       if !t.wantAnyConns() {
                                goto wait
                        }
                        // TODO: Determine if there's a listener on the port we're announcing.
@@ -1924,9 +1995,16 @@ func (t *Torrent) addPeerConn(c *PeerConn) (err error) {
                }
        }
        if len(t.conns) >= t.maxEstablishedConns {
-               c := t.worstBadConn()
+               numOutgoing := t.numOutgoingConns()
+               numIncoming := len(t.conns) - numOutgoing
+               c := t.worstBadConn(worseConnLensOpts{
+                       // We've already established that we have too many connections at this point, so we just
+                       // need to match what kind we have too many of vs. what we're trying to add now.
+                       incomingIsBad: (numIncoming-numOutgoing > 1) && c.outgoing,
+                       outgoingIsBad: (numOutgoing-numIncoming > 1) && !c.outgoing,
+               })
                if c == nil {
-                       return errors.New("don't want conns")
+                       return errors.New("don't want conn")
                }
                c.close()
                t.deletePeerConn(c)
@@ -1935,13 +2013,28 @@ func (t *Torrent) addPeerConn(c *PeerConn) (err error) {
                panic(len(t.conns))
        }
        t.conns[c] = struct{}{}
+       t.cl.event.Broadcast()
+       // We'll never receive the "p" extended handshake parameter.
        if !t.cl.config.DisablePEX && !c.PeerExtensionBytes.SupportsExtended() {
-               t.pex.Add(c) // as no further extended handshake expected
+               t.pex.Add(c)
        }
        return nil
 }
 
-func (t *Torrent) wantConns() bool {
+func (t *Torrent) newConnsAllowed() bool {
+       if !t.networkingEnabled.Bool() {
+               return false
+       }
+       if t.closed.IsSet() {
+               return false
+       }
+       if !t.needData() && (!t.seeding() || !t.haveAnyPieces()) {
+               return false
+       }
+       return true
+}
+
+func (t *Torrent) wantAnyConns() bool {
        if !t.networkingEnabled.Bool() {
                return false
        }
@@ -1951,7 +2044,35 @@ func (t *Torrent) wantConns() bool {
        if !t.needData() && (!t.seeding() || !t.haveAnyPieces()) {
                return false
        }
-       return len(t.conns) < t.maxEstablishedConns || t.worstBadConn() != nil
+       return len(t.conns) < t.maxEstablishedConns
+}
+
+func (t *Torrent) wantOutgoingConns() bool {
+       if !t.newConnsAllowed() {
+               return false
+       }
+       if len(t.conns) < t.maxEstablishedConns {
+               return true
+       }
+       numIncomingConns := len(t.conns) - t.numOutgoingConns()
+       return t.worstBadConn(worseConnLensOpts{
+               incomingIsBad: numIncomingConns-t.numOutgoingConns() > 1,
+               outgoingIsBad: false,
+       }) != nil
+}
+
+func (t *Torrent) wantIncomingConns() bool {
+       if !t.newConnsAllowed() {
+               return false
+       }
+       if len(t.conns) < t.maxEstablishedConns {
+               return true
+       }
+       numIncomingConns := len(t.conns) - t.numOutgoingConns()
+       return t.worstBadConn(worseConnLensOpts{
+               incomingIsBad: false,
+               outgoingIsBad: t.numOutgoingConns()-numIncomingConns > 1,
+       }) != nil
 }
 
 func (t *Torrent) SetMaxEstablishedConns(max int) (oldMax int) {
@@ -1964,7 +2085,7 @@ func (t *Torrent) SetMaxEstablishedConns(max int) (oldMax int) {
                        return true
                }),
        }
-       wcs.initKeys()
+       wcs.initKeys(worseConnLensOpts{})
        heap.Init(&wcs)
        for len(t.conns) > t.maxEstablishedConns && wcs.Len() > 0 {
                t.dropConnection(heap.Pop(&wcs).(*PeerConn))
@@ -2022,7 +2143,7 @@ func (t *Torrent) pieceHashed(piece pieceIndex, passed bool, hashIoErr error) {
                }
                err := p.Storage().MarkComplete()
                if err != nil {
-                       t.logger.Printf("%T: error marking piece complete %d: %s", t.storage, piece, err)
+                       t.logger.Levelf(log.Warning, "%T: error marking piece complete %d: %s", t.storage, piece, err)
                }
                t.cl.lock()
 
@@ -2067,7 +2188,7 @@ func (t *Torrent) pieceHashed(piece pieceIndex, passed bool, hashIoErr error) {
                        if len(bannableTouchers) >= 1 {
                                c := bannableTouchers[0]
                                if len(bannableTouchers) != 1 {
-                                       t.logger.Levelf(log.Warning, "would have banned %v for touching piece %v after failed piece check", c.remoteIp(), piece)
+                                       t.logger.Levelf(log.Debug, "would have banned %v for touching piece %v after failed piece check", c.remoteIp(), piece)
                                } else {
                                        // Turns out it's still useful to ban peers like this because if there's only a
                                        // single peer for a piece, and we never progress that piece to completion, we
@@ -2098,7 +2219,7 @@ func (t *Torrent) onPieceCompleted(piece pieceIndex) {
        t.piece(piece).readerCond.Broadcast()
        for conn := range t.conns {
                conn.have(piece)
-               t.maybeDropMutuallyCompletePeer(&conn.Peer)
+               t.maybeDropMutuallyCompletePeer(conn)
        }
 }
 
@@ -2130,7 +2251,7 @@ func (t *Torrent) onIncompletePiece(piece pieceIndex) {
 }
 
 func (t *Torrent) tryCreateMorePieceHashers() {
-       for !t.closed.IsSet() && t.activePieceHashes < 2 && t.tryCreatePieceHasher() {
+       for !t.closed.IsSet() && t.activePieceHashes < t.cl.config.PieceHashersPerTorrent && t.tryCreatePieceHasher() {
        }
 }
 
@@ -2252,8 +2373,45 @@ func (t *Torrent) VerifyData() {
        }
 }
 
-// Start the process of connecting to the given peer for the given torrent if appropriate.
-func (t *Torrent) initiateConn(peer PeerInfo) {
+func (t *Torrent) connectingToPeerAddr(addrStr string) bool {
+       return len(t.halfOpen[addrStr]) != 0
+}
+
+func (t *Torrent) hasPeerConnForAddr(x PeerRemoteAddr) bool {
+       addrStr := x.String()
+       for c := range t.conns {
+               ra := c.RemoteAddr
+               if ra.String() == addrStr {
+                       return true
+               }
+       }
+       return false
+}
+
+func (t *Torrent) getHalfOpenPath(
+       addrStr string,
+       attemptKey outgoingConnAttemptKey,
+) nestedmaps.Path[*PeerInfo] {
+       return nestedmaps.Next(nestedmaps.Next(nestedmaps.Begin(&t.halfOpen), addrStr), attemptKey)
+}
+
+func (t *Torrent) addHalfOpen(addrStr string, attemptKey *PeerInfo) {
+       path := t.getHalfOpenPath(addrStr, attemptKey)
+       if path.Exists() {
+               panic("should be unique")
+       }
+       path.Set(attemptKey)
+       t.cl.numHalfOpen++
+}
+
+// Start the process of connecting to the given peer for the given torrent if appropriate. I'm not
+// sure all the PeerInfo fields are being used.
+func initiateConn(
+       opts outgoingConnOpts,
+       ignoreLimits bool,
+) {
+       t := opts.t
+       peer := opts.peerInfo
        if peer.Id == t.cl.peerID {
                return
        }
@@ -2261,12 +2419,21 @@ func (t *Torrent) initiateConn(peer PeerInfo) {
                return
        }
        addr := peer.Addr
-       if t.addrActive(addr.String()) {
+       addrStr := addr.String()
+       if !ignoreLimits {
+               if t.connectingToPeerAddr(addrStr) {
+                       return
+               }
+       }
+       if t.hasPeerConnForAddr(addr) {
                return
        }
-       t.cl.numHalfOpen++
-       t.halfOpen[addr.String()] = peer
-       go t.cl.outgoingConnection(t, addr, peer.Source, peer.Trusted)
+       attemptKey := &peer
+       t.addHalfOpen(addrStr, attemptKey)
+       go t.cl.outgoingConnection(
+               opts,
+               attemptKey,
+       )
 }
 
 // Adds a trusted, pending peer for each of the given Client's addresses. Typically used in tests to
@@ -2287,7 +2454,7 @@ func (t *Torrent) AddClientPeer(cl *Client) int {
 // connection.
 func (t *Torrent) allStats(f func(*ConnStats)) {
        f(&t.stats)
-       f(&t.cl.stats)
+       f(&t.cl.connStats)
 }
 
 func (t *Torrent) hashingPiece(i pieceIndex) bool {
@@ -2425,7 +2592,6 @@ func (t *Torrent) addWebSeed(url string, opts ...AddWebSeedsOpt) {
                        },
                },
                activeRequests: make(map[Request]webseed.Request, maxRequests),
-               maxRequests:    maxRequests,
        }
        ws.peer.initRequestState()
        for _, opt := range opts {
@@ -2541,3 +2707,199 @@ type requestState struct {
        peer *Peer
        when time.Time
 }
+
+// Returns an error if a received chunk is out of bounds in someway.
+func (t *Torrent) checkValidReceiveChunk(r Request) error {
+       if !t.haveInfo() {
+               return errors.New("torrent missing info")
+       }
+       if int(r.Index) >= t.numPieces() {
+               return fmt.Errorf("chunk index %v, torrent num pieces %v", r.Index, t.numPieces())
+       }
+       pieceLength := t.pieceLength(pieceIndex(r.Index))
+       if r.Begin >= pieceLength {
+               return fmt.Errorf("chunk begins beyond end of piece (%v >= %v)", r.Begin, pieceLength)
+       }
+       // We could check chunk lengths here, but chunk request size is not changed often, and tricky
+       // for peers to manipulate as they need to send potentially large buffers to begin with. There
+       // should be considerable checks elsewhere for this case due to the network overhead. We should
+       // catch most of the overflow manipulation stuff by checking index and begin above.
+       return nil
+}
+
+func (t *Torrent) peerConnsWithDialAddrPort(target netip.AddrPort) (ret []*PeerConn) {
+       for pc := range t.conns {
+               dialAddr, err := pc.remoteDialAddrPort()
+               if err != nil {
+                       continue
+               }
+               if dialAddr != target {
+                       continue
+               }
+               ret = append(ret, pc)
+       }
+       return
+}
+
+func wrapUtHolepunchMsgForPeerConn(
+       recipient *PeerConn,
+       msg utHolepunch.Msg,
+) pp.Message {
+       extendedPayload, err := msg.MarshalBinary()
+       if err != nil {
+               panic(err)
+       }
+       return pp.Message{
+               Type:            pp.Extended,
+               ExtendedID:      MapMustGet(recipient.PeerExtensionIDs, utHolepunch.ExtensionName),
+               ExtendedPayload: extendedPayload,
+       }
+}
+
+func sendUtHolepunchMsg(
+       pc *PeerConn,
+       msgType utHolepunch.MsgType,
+       addrPort netip.AddrPort,
+       errCode utHolepunch.ErrCode,
+) {
+       holepunchMsg := utHolepunch.Msg{
+               MsgType:  msgType,
+               AddrPort: addrPort,
+               ErrCode:  errCode,
+       }
+       incHolepunchMessagesSent(holepunchMsg)
+       ppMsg := wrapUtHolepunchMsgForPeerConn(pc, holepunchMsg)
+       pc.write(ppMsg)
+}
+
+func incHolepunchMessages(msg utHolepunch.Msg, verb string) {
+       torrent.Add(
+               fmt.Sprintf(
+                       "holepunch %v %v messages %v",
+                       msg.MsgType,
+                       addrPortProtocolStr(msg.AddrPort),
+                       verb,
+               ),
+               1,
+       )
+}
+
+func incHolepunchMessagesReceived(msg utHolepunch.Msg) {
+       incHolepunchMessages(msg, "received")
+}
+
+func incHolepunchMessagesSent(msg utHolepunch.Msg) {
+       incHolepunchMessages(msg, "sent")
+}
+
+func (t *Torrent) handleReceivedUtHolepunchMsg(msg utHolepunch.Msg, sender *PeerConn) error {
+       incHolepunchMessagesReceived(msg)
+       switch msg.MsgType {
+       case utHolepunch.Rendezvous:
+               t.logger.Printf("got holepunch rendezvous request for %v from %p", msg.AddrPort, sender)
+               sendMsg := sendUtHolepunchMsg
+               senderAddrPort, err := sender.remoteDialAddrPort()
+               if err != nil {
+                       sender.logger.Levelf(
+                               log.Warning,
+                               "error getting ut_holepunch rendezvous sender's dial address: %v",
+                               err,
+                       )
+                       // There's no better error code. The sender's address itself is invalid. I don't see
+                       // this error message being appropriate anywhere else anyway.
+                       sendMsg(sender, utHolepunch.Error, msg.AddrPort, utHolepunch.NoSuchPeer)
+               }
+               targets := t.peerConnsWithDialAddrPort(msg.AddrPort)
+               if len(targets) == 0 {
+                       sendMsg(sender, utHolepunch.Error, msg.AddrPort, utHolepunch.NotConnected)
+                       return nil
+               }
+               for _, pc := range targets {
+                       if !pc.supportsExtension(utHolepunch.ExtensionName) {
+                               sendMsg(sender, utHolepunch.Error, msg.AddrPort, utHolepunch.NoSupport)
+                               continue
+                       }
+                       sendMsg(sender, utHolepunch.Connect, msg.AddrPort, 0)
+                       sendMsg(pc, utHolepunch.Connect, senderAddrPort, 0)
+               }
+               return nil
+       case utHolepunch.Connect:
+               holepunchAddr := msg.AddrPort
+               t.logger.Printf("got holepunch connect request for %v from %p", holepunchAddr, sender)
+               if g.MapContains(t.cl.undialableWithoutHolepunch, holepunchAddr) {
+                       setAdd(&t.cl.undialableWithoutHolepunchDialedAfterHolepunchConnect, holepunchAddr)
+                       if g.MapContains(t.cl.accepted, holepunchAddr) {
+                               setAdd(&t.cl.probablyOnlyConnectedDueToHolepunch, holepunchAddr)
+                       }
+               }
+               opts := outgoingConnOpts{
+                       peerInfo: PeerInfo{
+                               Addr:         msg.AddrPort,
+                               Source:       PeerSourceUtHolepunch,
+                               PexPeerFlags: sender.pex.remoteLiveConns[msg.AddrPort].UnwrapOrZeroValue(),
+                       },
+                       t: t,
+                       // Don't attempt to start our own rendezvous if we fail to connect.
+                       skipHolepunchRendezvous:  true,
+                       receivedHolepunchConnect: true,
+                       // Assume that the other end initiated the rendezvous, and will use our preferred
+                       // encryption. So we will act normally.
+                       HeaderObfuscationPolicy: t.cl.config.HeaderObfuscationPolicy,
+               }
+               initiateConn(opts, true)
+               return nil
+       case utHolepunch.Error:
+               torrent.Add("holepunch error messages received", 1)
+               t.logger.Levelf(log.Debug, "received ut_holepunch error message from %v: %v", sender, msg.ErrCode)
+               return nil
+       default:
+               return fmt.Errorf("unhandled msg type %v", msg.MsgType)
+       }
+}
+
+func addrPortProtocolStr(addrPort netip.AddrPort) string {
+       addr := addrPort.Addr()
+       switch {
+       case addr.Is4():
+               return "ipv4"
+       case addr.Is6():
+               return "ipv6"
+       default:
+               panic(addrPort)
+       }
+}
+
+func (t *Torrent) trySendHolepunchRendezvous(addrPort netip.AddrPort) error {
+       rzsSent := 0
+       for pc := range t.conns {
+               if !pc.supportsExtension(utHolepunch.ExtensionName) {
+                       continue
+               }
+               if pc.supportsExtension(pp.ExtensionNamePex) {
+                       if !g.MapContains(pc.pex.remoteLiveConns, addrPort) {
+                               continue
+                       }
+               }
+               t.logger.Levelf(log.Debug, "sent ut_holepunch rendezvous message to %v for %v", pc, addrPort)
+               sendUtHolepunchMsg(pc, utHolepunch.Rendezvous, addrPort, 0)
+               rzsSent++
+       }
+       if rzsSent == 0 {
+               return errors.New("no eligible relays")
+       }
+       return nil
+}
+
+func (t *Torrent) numHalfOpenAttempts() (num int) {
+       for _, attempts := range t.halfOpen {
+               num += len(attempts)
+       }
+       return
+}
+
+func (t *Torrent) getDialTimeoutUnlocked() time.Duration {
+       cl := t.cl
+       cl.rLock()
+       defer cl.rUnlock()
+       return t.dialTimeout()
+}