libtorrent: Optimize UDP trackers for UDNS (#42)

This commit optimizes UDP trackers with a fast path to ipv4 addresses. When using UDNS, we know the address is going to resolve to IPV4. We can skip a few checks to increase performance.

libtorrent/rak/socket_address.h

@@ -155,6 +155,10 @@ class socket_address_inet {
   bool                is_port_any() const                     { return port() == 0; }
   bool                is_address_any() const                  { return m_sockaddr.sin_addr.s_addr == htonl(INADDR_ANY); }
 
+#ifdef USE_UDNS
+  bool                is_bindable() const                     { return !is_address_any(); }
+#endif
+
   void                clear()                                 { std::memset(this, 0, sizeof(socket_address_inet)); set_family(); }
 
   uint16_t            port() const                            { return ntohs(m_sockaddr.sin_port); }
@@ -168,6 +172,10 @@ class socket_address_inet {
   uint32_t            address_n() const                       { return m_sockaddr.sin_addr.s_addr; }
   std::string         address_str() const;
   bool                address_c_str(char* buf, socklen_t size) const;
+
+#ifdef USE_UDNS
+  std::string         pretty_address_str() const              { return address_str(); }
+#endif
 
   void                set_address(in_addr a)                  { m_sockaddr.sin_addr = a; }
   void                set_address_h(uint32_t a)               { m_sockaddr.sin_addr.s_addr = htonl(a); }
@@ -180,13 +188,24 @@ class socket_address_inet {
   sa_family_t         family() const                          { return m_sockaddr.sin_family; }
   void                set_family()                            { m_sockaddr.sin_family = AF_INET; }
 
+#ifdef USE_UDNS
+  uint32_t            length() const                          { return sizeof(sockaddr_in); }
+#endif
+
   sockaddr*           c_sockaddr()                            { return reinterpret_cast<sockaddr*>(&m_sockaddr); }
   sockaddr_in*        c_sockaddr_inet()                       { return &m_sockaddr; }
 
   const sockaddr*     c_sockaddr() const                      { return reinterpret_cast<const sockaddr*>(&m_sockaddr); }
   const sockaddr_in*  c_sockaddr_inet() const                 { return &m_sockaddr; }
 
   socket_address_inet6 to_mapped_address() const;
+
+#ifdef USE_UDNS
+  static socket_address_inet*       cast_from(sockaddr* sa)        { return reinterpret_cast<socket_address_inet*>(sa); }
+  static const socket_address_inet* cast_from(const sockaddr* sa)  { return reinterpret_cast<const socket_address_inet*>(sa); }
+  static socket_address_inet*       cast_from_inet(sockaddr_in* sa)        { return reinterpret_cast<socket_address_inet*>(sa); }
+  static const socket_address_inet* cast_from_inet(const sockaddr_in* sa)  { return reinterpret_cast<const socket_address_inet*>(sa); }
+#endif
 
   bool                operator == (const socket_address_inet& rhs) const;
   bool                operator < (const socket_address_inet& rhs) const;

libtorrent/src/net/socket_datagram.cc

@@ -87,7 +87,7 @@ SocketDatagram::write_datagram(const void* buffer, unsigned int length, rak::soc
 
 #ifdef USE_UDNS
 int
-SocketDatagram::write_datagram_ipv4(const void* buffer, unsigned int length, rak::socket_address* sa) {
+SocketDatagram::write_datagram_ipv4(const void* buffer, unsigned int length, rak::socket_address_inet* sa) {
   if (length == 0)
     throw internal_error("Tried to send buffer length 0");
 

libtorrent/src/net/socket_datagram.h

@@ -49,7 +49,7 @@ class SocketDatagram : public SocketBase {
   int                 read_datagram(void* buffer, unsigned int length, rak::socket_address* sa = NULL);
   int                 write_datagram(const void* buffer, unsigned int length, rak::socket_address* sa = NULL);
 #ifdef USE_UDNS
-  int                 write_datagram_ipv4(const void* buffer, unsigned int length, rak::socket_address* sa = NULL);
+  int                 write_datagram_ipv4(const void* buffer, unsigned int length, rak::socket_address_inet* sa = NULL);
 #endif
 };
 

libtorrent/src/net/socket_fd.cc

@@ -208,7 +208,7 @@ SocketFd::bind(const rak::socket_address& sa) {
 
 #ifdef USE_UDNS
 bool
-SocketFd::bind_ipv4(const rak::socket_address& sa) {
+SocketFd::bind_ipv4(const rak::socket_address_inet& sa) {
   check_valid();
 
   return !::bind(m_fd, sa.c_sockaddr(), sa.length());

libtorrent/src/net/socket_fd.h

@@ -41,6 +41,9 @@
 
 namespace rak {
   class socket_address;
+#ifdef USE_UDNS
+  class socket_address_inet;
+#endif
 }
 
 namespace torrent {
@@ -88,7 +91,7 @@ class SocketFd {
   bool                getsockname(rak::socket_address* sa);
 
 #ifdef USE_UDNS
-  bool                bind_ipv4(const rak::socket_address& sa);
+  bool                bind_ipv4(const rak::socket_address_inet& sa);
 #endif
 
   bool                listen(int size);

libtorrent/src/torrent/connection_manager.cc

@@ -62,8 +62,8 @@ class UdnsAsyncResolver : public AsyncResolver {
 public:
   UdnsAsyncResolver(ConnectionManager *cm) : AsyncResolver(cm) {}
 
-  void *enqueue(const char *name, int family, resolver_callback *cbck) {
-    return m_udnsevent.enqueue_resolve(name, family, cbck);
+  void *enqueue(const char *name, resolver_callback *cbck) {
+    return m_udnsevent.enqueue_resolve(name, cbck);
   }
 
   void flush() {
@@ -79,7 +79,7 @@ class UdnsAsyncResolver : public AsyncResolver {
 };
 
 void
-ConnectionManager::start_udp_announce(uint64_t idx, const sockaddr* sa, int err) {
+ConnectionManager::start_udp_announce(uint64_t idx, const sockaddr_in* sa, int err) {
   if (m_tracker_udp_list[idx] != NULL) {
     m_tracker_udp_list[idx]->start_announce(sa, err);
   }
@@ -135,7 +135,11 @@ class StubAsyncResolver : public AsyncResolver {
 #endif
 
 static void
+#ifdef USE_UDNS
+resolve_host(const char* host, int family, int socktype, legacy_resolver_callback slot) {
+#else
 resolve_host(const char* host, int family, int socktype, resolver_callback slot) {
+#endif
   if (manager->main_thread_main()->is_current())
     thread_base::release_global_lock();
 

libtorrent/src/torrent/connection_manager.h

@@ -61,7 +61,12 @@ typedef std::pair<Throttle*, Throttle*> ThrottlePair;
 
 // The sockaddr argument in the result call is NULL if the resolve failed,
 // and the int holds the error code.
+#ifdef USE_UDNS
+typedef std::function<void (const sockaddr_in*, int)> resolver_callback;
+typedef std::function<void (const sockaddr*, int)> legacy_resolver_callback;
+#else
 typedef std::function<void (const sockaddr*, int)> resolver_callback;
+#endif
 
 // Encapsulates whether we do genuine async resolution or fall back to sync.
 // In a build with USE_UDNS, these do genuine asynchronous DNS resolution.
@@ -74,7 +79,11 @@ class LIBTORRENT_EXPORT AsyncResolver {
   // this queues a DNS resolve but doesn't send it. it doesn't execute any callbacks
   // and returns control immediately. the return value is an opaque identifier that
   // can be used to cancel the query (as long as the callback hasn't been executed yet):
+#ifdef USE_UDNS
+  virtual void*   enqueue(const char *name, resolver_callback *cbck) = 0;
+#else
   virtual void*   enqueue(const char *name, int family, resolver_callback *cbck) = 0;
+#endif
   // this sends any queued resolves. it can execute arbitrary callbacks
   // before returning control:
   virtual void    flush() = 0;
@@ -130,7 +139,11 @@ class LIBTORRENT_EXPORT ConnectionManager {
   typedef std::function<uint32_t (const sockaddr*)>     slot_filter_type;
   typedef std::function<ThrottlePair (const sockaddr*)> slot_throttle_type;
 
+#ifdef USE_UDNS
+  typedef std::function<void (const char*, int, int, legacy_resolver_callback)> slot_resolver_type;
+#else
   typedef std::function<void (const char*, int, int, resolver_callback)> slot_resolver_type;
+#endif
 
   ConnectionManager();
   ~ConnectionManager();
@@ -182,12 +195,8 @@ class LIBTORRENT_EXPORT ConnectionManager {
   void                set_listen_port(port_type p)            { m_listen_port = p; }
   void                set_listen_backlog(int v);
 
-  void*               enqueue_async_resolve(const char *name, int family, resolver_callback *cbck);
-  void                flush_async_resolves();
-  void                cancel_async_resolve(void *query);
-
 #ifdef USE_UDNS
-  void                start_udp_announce(uint64_t idx, const sockaddr* sa, int err);
+  void                start_udp_announce(uint64_t idx, const sockaddr_in* sa, int err);
   void                null_udp_tracker(uint64_t idx)          { m_tracker_udp_list[idx] = NULL; }
   void                add_udp_tracker(TrackerUdp* tracker)    { m_tracker_udp_list.push_back(tracker); }
   uint64_t            get_udp_tracker_count()                 { return m_tracker_udp_list.size(); }

libtorrent/src/tracker/tracker_udp.cc

@@ -110,24 +110,25 @@ TrackerUdp::send_state(int state) {
 
   m_resolver_query = manager->connection_manager()->async_resolver().enqueue(
       m_hostname.c_str(),
-      AF_UNSPEC,
 #ifdef USE_UDNS
       manager->connection_manager()->get_resolver_callback(m_vec_idx)
 #else
+      AF_UNSPEC,
       &m_resolver_callback
 #endif
   );
   manager->connection_manager()->async_resolver().flush();
 }
 
+#ifdef USE_UDNS
 void
-TrackerUdp::start_announce(const sockaddr* sa, int err) {
+TrackerUdp::start_announce(const sockaddr_in* sa, int err) {
   m_resolver_query = NULL;
 
   if (sa == NULL)
     return receive_failed("could not resolve hostname");
 
-  m_connectAddress = *rak::socket_address::cast_from(sa);
+  m_connectAddress = *rak::socket_address_inet::cast_from_inet(sa);
   m_connectAddress.set_port(m_port);
 
   LT_LOG_TRACKER(DEBUG, "address found (address:%s)", m_connectAddress.address_str().c_str());
@@ -136,20 +137,50 @@ TrackerUdp::start_announce(const sockaddr* sa, int err) {
     return receive_failed("invalid tracker address");
 
   // TODO: Make each of these a separate error... at the very least separate open and bind.
-#ifdef USE_UDNS
   if (!get_fd().open_datagram_ipv4() || !get_fd().set_nonblock())
+    return receive_failed("could not open UDP socket");
+
+  auto bind_address = rak::socket_address_inet::cast_from(manager->connection_manager()->bind_address());
+
+  if (bind_address->is_bindable() && !get_fd().bind_ipv4(*bind_address))
+    return receive_failed("failed to bind socket to udp address '" + bind_address->pretty_address_str() + "' with error '" + rak::error_number::current().c_str() + "'");
+
+  m_readBuffer = new ReadBuffer;
+  m_writeBuffer = new WriteBuffer;
+
+  prepare_connect_input();
+
+  manager->poll()->open(this);
+  manager->poll()->insert_read(this);
+  manager->poll()->insert_write(this);
+  manager->poll()->insert_error(this);
+
+  m_tries = m_parent->info()->udp_tries();
+  priority_queue_insert(&taskScheduler, &m_taskTimeout, (cachedTime + rak::timer::from_seconds(m_parent->info()->udp_timeout())).round_seconds());
+}
 #else
+void
+TrackerUdp::start_announce(const sockaddr* sa, int err) {
+  m_resolver_query = NULL;
+
+  if (sa == NULL)
+    return receive_failed("could not resolve hostname");
+
+  m_connectAddress = *rak::socket_address::cast_from(sa);
+  m_connectAddress.set_port(m_port);
+
+  LT_LOG_TRACKER(DEBUG, "address found (address:%s)", m_connectAddress.address_str().c_str());
+
+  if (!m_connectAddress.is_valid())
+    return receive_failed("invalid tracker address");
+
+  // TODO: Make each of these a separate error... at the very least separate open and bind.
   if (!get_fd().open_datagram() || !get_fd().set_nonblock())
-#endif
     return receive_failed("could not open UDP socket");
 
   auto bind_address = rak::socket_address::cast_from(manager->connection_manager()->bind_address());
 
-#ifdef USE_UDNS
-  if (bind_address->is_bindable() && !get_fd().bind_ipv4(*bind_address))
-#else
   if (bind_address->is_bindable() && !get_fd().bind(*bind_address))
-#endif
     return receive_failed("failed to bind socket to udp address '" + bind_address->pretty_address_str() + "' with error '" + rak::error_number::current().c_str() + "'");
 
   m_readBuffer = new ReadBuffer;
@@ -165,6 +196,7 @@ TrackerUdp::start_announce(const sockaddr* sa, int err) {
   m_tries = m_parent->info()->udp_tries();
   priority_queue_insert(&taskScheduler, &m_taskTimeout, (cachedTime + rak::timer::from_seconds(m_parent->info()->udp_timeout())).round_seconds());
 }
+#endif	
 
 void
 TrackerUdp::close() {

libtorrent/src/tracker/tracker_udp.h

@@ -75,8 +75,12 @@ class TrackerUdp : public SocketDatagram, public Tracker {
   virtual void        event_read();
   virtual void        event_write();
   virtual void        event_error();
-
+
+#ifdef USE_UDNS
+  void                start_announce(const sockaddr_in* sa, int err);
+#else
   void                start_announce(const sockaddr* sa, int err);
+#endif
 
 private:
   void                close_directly();
@@ -93,7 +97,12 @@ class TrackerUdp : public SocketDatagram, public Tracker {
 
   bool                parse_udp_url(const std::string& url, hostname_type& hostname, int& port) const;
 
+#ifdef USE_UDNS
+  rak::socket_address_inet m_connectAddress;
+#else
   rak::socket_address m_connectAddress;
+#endif
+
   int                 m_port;
   std::string         m_hostname;