fix: abort handshake if the torrent is stopped (#6947)

* fix: abort handshake if torrent isn't running

* fix: check if torrent is running in all cases

* fix: don't penalise peer if handshake failed because of us

* fix: tests

* perf: ensure copy-elision in `HandshakeMediator::torrent()`

* code review: more accurate log wording

libtransmission/handshake.cc

@@ -290,14 +290,14 @@ ReadState tr_handshake::read_handshake(tr_peerIo* peer_io)
     auto hash = tr_sha1_digest_t{};
     peer_io->read_bytes(std::data(hash), std::size(hash));
 
+    if (auto const& info = mediator_->torrent(hash); !info || !info->is_running)
+    {
+        tr_logAddTraceHand(this, "peer is trying to connect to us for a torrent we aren't running.");
+        return done(false);
+    }
+
     if (is_incoming() && peer_io->torrent_hash() == tr_sha1_digest_t{}) // incoming plain handshake
     {
-        if (!mediator_->torrent(hash))
-        {
-            tr_logAddTraceHand(this, "peer is trying to connect to us for a torrent we don't have.");
-            return done(false);
-        }
-
         peer_io->set_torrent_hash(hash);
     }
     else // outgoing, or incoming MSE handshake
@@ -458,14 +458,14 @@ ReadState tr_handshake::read_crypto_provide(tr_peerIo* peer_io)
         obfuscated_hash[i] = x_or[i] ^ req3[i];
     }
 
-    if (auto const info = mediator_->torrent_from_obfuscated(obfuscated_hash); info)
+    if (auto const info = mediator_->torrent_from_obfuscated(obfuscated_hash); info && info->is_running)
     {
         tr_logAddTraceHand(this, fmt::format("got INCOMING connection's MSE handshake for torrent [{}]", info->id));
         peer_io->set_torrent_hash(info->info_hash);
     }
     else
     {
-        tr_logAddTraceHand(this, "can't find that torrent...");
+        tr_logAddTraceHand(this, "we are not running that torrent...");
         return done(false);
     }
 
@@ -714,7 +714,7 @@ bool tr_handshake::build_handshake_message(tr_peerIo* io, libtransmission::Buffe
     TR_ASSERT_MSG(info_hash != tr_sha1_digest_t{}, "build_handshake_message requires an info_hash");
 
     auto const info = mediator_->torrent(info_hash);
-    if (!info)
+    if (!info || !info->is_running)
     {
         return false;
     }

libtransmission/handshake.h

@@ -64,6 +64,7 @@ public:
             tr_peer_id_t client_peer_id;
             tr_torrent_id_t id;
             bool is_done;
+            bool is_running;
         };
 
         virtual ~Mediator() = default;

libtransmission/peer-mgr.cc

@@ -75,12 +75,13 @@ private:
             return {};
         }
 
-        auto info = TorrentInfo{};
+        return TorrentInfo{
-        info.info_hash = tor->info_hash();
+            tor->info_hash(), // info_hash
-        info.client_peer_id = tor->peer_id();
+            tor->peer_id(), // client_peer_id
-        info.id = tor->id();
+            tor->id(), // id
-        info.is_done = tor->is_done();
+            tor->is_done(), // is_done
-        return info;
+            tor->is_running() // is_running
+        };
     }
 
 public:
@@ -1289,7 +1290,12 @@ void create_bit_torrent_peer(
         info->destroy_handshake();
     }
 
-    if (!result.is_connected || swarm == nullptr || !swarm->is_running)
+    if (swarm == nullptr || !swarm->is_running)
+    {
+        return false;
+    }
+
+    if (!result.is_connected)
     {
         if (info && !info->is_connected())
         {

tests/libtransmission/handshake-test.cc

@@ -155,11 +155,13 @@ public:
     tr_handshake::Mediator::TorrentInfo const TorrentWeAreSeeding{ tr_sha1::digest("abcde"sv),
                                                                    tr_peerIdInit(),
                                                                    tr_torrent_id_t{ 100 },
-                                                                   true /*is_done*/ };
+                                                                   true /*is_done*/,
+                                                                   true /*is_running*/ };
     tr_handshake::Mediator::TorrentInfo const UbuntuTorrent{ *tr_sha1_from_string("2c6b6858d61da9543d4231a71db4b1c9264b0685"sv),
                                                              tr_peerIdInit(),
                                                              tr_torrent_id_t{ 101 },
-                                                             false /*is_done*/ };
+                                                             false /*is_done*/,
+                                                             true /*is_running*/ };
 
     auto createIncomingIo(tr_session* session)
     {