improved support for multi-homed clients

ChangeLog

@@ -1,3 +1,4 @@
+	* improved support for multi-homed clients
 	* added feature to not count downloaded bytes from web seeds in stats
 	* added alert for incoming local service discovery messages
 	* added option to set file priorities when adding torrents

docs/manual.rst

@@ -2744,8 +2744,10 @@ use_interface()
 
 ``use_interface()`` sets the network interface this torrent will use when it opens outgoing
 connections. By default, it uses the same interface as the session_ uses to listen on. The
-parameter must be a string containing an ip-address (either an IPv4 or IPv6 address). If
-the string does not conform to this format and exception is thrown.
+parameter must be a string containing one or more, comma separated, ip-address (either an
+IPv4 or IPv6 address). When specifying multiple interfaces, the torrent will round-robin
+which interface to use for each outgoing conneciton. This is useful for clients that are
+multi-homed.
 
 
 info_hash()
@@ -3485,6 +3487,8 @@ It contains the following fields::
 
 		float progress;
 		int progress_ppm;
+
+		tcp::endpoint local_endpoint;
 	};
 
 The ``flags`` attribute tells you in which state the peer is. It is set to
@@ -3710,6 +3714,11 @@ floating point operations are diabled, instead use ``progress_ppm``.
 ``progress_ppm`` indicates the download progress of the peer in the range [0, 1000000]
 (parts per million).
 
+``local_endpoint`` is the IP and port pair the socket is bound to locally. i.e. the IP
+address of the interface it's going out over. This may be useful for multi-homed
+clients with multiple interfaces to the internet.
+
+
 session customization
 =====================
 

examples/client_test.cpp

@@ -329,7 +329,7 @@ int peer_index(libtorrent::tcp::endpoint addr, std::vector<libtorrent::peer_info
 void print_peer_info(std::string& out, std::vector<libtorrent::peer_info> const& peers)
 {
 	using namespace libtorrent;
-	if (print_ip) out += "IP                           ";
+	if (print_ip) out += "IP                                           ";
 #ifndef TORRENT_DISABLE_GEO_IP
 	if (print_as) out += "AS                                         ";
 #endif
@@ -355,7 +355,8 @@ void print_peer_info(std::string& out, std::vector<libtorrent::peer_info> const&
 		if (print_ip)
 		{
 			error_code ec;
-			snprintf(str, sizeof(str), "%-22s:%-5d ", i->ip.address().to_string(ec).c_str(), i->ip.port());
+			snprintf(str, sizeof(str), "%-22s %22s ", print_endpoint(i->ip).c_str()
+				, print_endpoint(i->local_endpoint).c_str());
 			out += str;
 		}
 
@@ -511,6 +512,7 @@ int torrent_upload_limit = 0;
 int torrent_download_limit = 0;
 std::string monitor_dir;
 std::string bind_to_interface = "";
+std::string outgoing_interface = "";
 int poll_interval = 5;
 int max_connections_per_torrent = 50;
 
@@ -573,6 +575,7 @@ void add_torrent(libtorrent::session& ses
 	h.set_ratio(preferred_ratio);
 	h.set_upload_limit(torrent_upload_limit);
 	h.set_download_limit(torrent_download_limit);
+	h.use_interface(outgoing_interface.c_str());
 #ifndef TORRENT_DISABLE_RESOLVE_COUNTRIES
 	h.resolve_countries(true);
 #endif
@@ -752,6 +755,8 @@ int main(int argc, char* argv[])
 			"  -m <path>             sets the .torrent monitor directory\n"
 			"  -b <IP>               sets IP of the interface to bind the\n"
 			"                        listen socket to\n"
+			"  -I <IP>               sets the IP of the interface to bind\n"
+			"                        outgoing peer connections to\n"
 			"  -w <seconds>          sets the retry time for failed web seeds\n"
 			"  -t <seconds>          sets the scan interval of the monitor dir\n"
 			"  -x <file>             loads an emule IP-filter file\n"
@@ -956,6 +961,7 @@ int main(int argc, char* argv[])
 #endif
 				}
 				break;
+			case 'I': outgoing_interface = arg; break;
 		}
 		++i; // skip the argument
 	}
@@ -999,6 +1005,7 @@ int main(int argc, char* argv[])
 		h.set_ratio(preferred_ratio);
 		h.set_upload_limit(torrent_upload_limit);
 		h.set_download_limit(torrent_download_limit);
+		h.use_interface(outgoing_interface.c_str());
 	}
 
 	for (std::vector<std::string>::iterator i = torrents.begin()
@@ -1026,6 +1033,7 @@ int main(int argc, char* argv[])
 			h.set_ratio(preferred_ratio);
 			h.set_upload_limit(torrent_upload_limit);
 			h.set_download_limit(torrent_download_limit);
+			h.use_interface(outgoing_interface.c_str());
 			continue;
 		}
 

include/libtorrent/peer_info.hpp

@@ -216,6 +216,8 @@ namespace libtorrent
 		int progress_ppm; // [0, 1000000]
 
 		int estimated_reciprocation_rate;
+
+		tcp::endpoint local_endpoint;
 	};
 
 	struct TORRENT_EXPORT peer_list_entry

include/libtorrent/torrent.hpp

@@ -309,7 +309,7 @@ namespace libtorrent
 		void file_progress(std::vector<size_type>& fp, int flags = 0) const;
 
 		void use_interface(std::string net_interface);
-		tcp::endpoint get_interface() const { return m_net_interface; }
+		tcp::endpoint get_interface() const;
 		
 		void connect_to_url_seed(std::list<web_seed_entry>::iterator url);
 		bool connect_to_peer(policy::peer* peerinfo);
@@ -939,9 +939,10 @@ namespace libtorrent
 		std::string m_username;
 		std::string m_password;
 
-		// the network interface all outgoing connections
-		// are opened through
-		union_endpoint m_net_interface;
+		// the network interfaces outgoing connections
+		// are opened through. If there is more then one,
+		// they are used in a round-robin fasion
+		std::vector<union_endpoint> m_net_interfaces;
 
 		std::string m_save_path;
 
@@ -1208,6 +1209,9 @@ namespace libtorrent
 		// the number of seconds since the last byte was uploaded
 		// from this torrent
 		boost::uint16_t m_last_upload;
+
+		// round-robin index into m_interfaces
+		mutable boost::uint8_t m_interface_index;
 	};
 }
 

src/peer_connection.cpp

@@ -3471,6 +3471,9 @@ namespace libtorrent
 		int upload_capacity = m_ses.upload_rate_limit();
 		if (upload_capacity == 0)
 			upload_capacity = (std::max)(20000, m_ses.m_peak_up_rate + 10000);
+
+		error_code ec;
+		p.local_endpoint = get_socket()->local_endpoint(ec);
 	}
 
 	// allocates a disk buffer of size 'disk_buffer_size' and replaces the

src/torrent.cpp

@@ -77,6 +77,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "libtorrent/broadcast_socket.hpp"
 #include "libtorrent/kademlia/dht_tracker.hpp"
 #include "libtorrent/peer_info.hpp"
+#include "libtorrent/enum_net.hpp"
 
 #if TORRENT_USE_IOSTREAM
 #include <iostream>
@@ -226,7 +227,7 @@ namespace libtorrent
 		PRINT_OFFSETOF(torrent, m_time_critical_pieces)
 		PRINT_OFFSETOF(torrent, m_username)
 		PRINT_OFFSETOF(torrent, m_password)
-		PRINT_OFFSETOF(torrent, m_net_interface)
+		PRINT_OFFSETOF(torrent, m_net_interfaces)
 		PRINT_OFFSETOF(torrent, m_save_path)
 		PRINT_OFFSETOF(torrent, m_verified)
 		PRINT_OFFSETOF(torrent, m_error)
@@ -323,7 +324,6 @@ namespace libtorrent
 		, m_tracker_timer(ses.m_io_service)
 		, m_ses(ses)
 		, m_trackers(m_torrent_file->trackers())
-		, m_net_interface(tcp::endpoint(net_interface.address(), 0))
 		, m_save_path(complete(p.save_path))
 		, m_storage_constructor(p.storage)
 		, m_ratio(0.f)
@@ -381,7 +381,10 @@ namespace libtorrent
 		, m_last_scrape(0)
 		, m_last_download(0)
 		, m_last_upload(0)
+		, m_interface_index(0)
 	{
+		m_net_interfaces.push_back(net_interface);
+
 		if (p.file_priorities)
 			m_file_priority = *p.file_priorities;
 
@@ -1269,14 +1272,30 @@ namespace libtorrent
 		files_checked();
 	}
 
-	void torrent::use_interface(std::string net_interface)
+	void torrent::use_interface(std::string net_interfaces)
 	{
 		INVARIANT_CHECK;
+		m_net_interfaces.clear();
 
-		error_code ec;
-		address a(address::from_string(net_interface.c_str(), ec));
-		if (ec) return;
-		m_net_interface = tcp::endpoint(a, 0);
+		char* str = &net_interfaces[0];
+
+		while (str)
+		{
+			char* space = strchr(str, ',');
+			if (space) *space++ = 0;
+			error_code ec;
+			address a(address::from_string(str, ec));
+			str = space;
+			if (ec) continue;
+			m_net_interfaces.push_back(tcp::endpoint(a, 0));
+		}
+	}
+
+	tcp::endpoint torrent::get_interface() const
+	{
+		if (m_net_interfaces.empty()) return tcp::endpoint(address_v4(), 0);
+		if (m_interface_index >= m_net_interfaces.size()) m_interface_index = 0;
+		return m_net_interfaces[m_interface_index++];
 	}
 
 	void torrent::on_tracker_announce_disp(boost::weak_ptr<torrent> p