package torrent import ( "context" "net" "strconv" utp "github.com/anacrolix/go-libutp" "github.com/anacrolix/missinggo/perf" "github.com/anacrolix/missinggo/v2" "github.com/pkg/errors" ) type Listener interface { // Accept waits for and returns the next connection to the listener. Accept() (net.Conn, error) // Addr returns the listener's network address. Addr() net.Addr } type socket interface { Listener Dialer Close() error } func listen(n network, addr string, f firewallCallback) (socket, error) { switch { case n.Tcp: return listenTcp(n.String(), addr) case n.Udp: return listenUtp(n.String(), addr, f) default: panic(n) } } func listenTcp(network, address string) (s socket, err error) { l, err := net.Listen(network, address) return tcpSocket{ Listener: l, NetworkDialer: NetworkDialer{ Network: network, Dialer: DefaultNetDialer, }, }, err } type tcpSocket struct { net.Listener NetworkDialer } func listenAll(networks []network, getHost func(string) string, port int, f firewallCallback) ([]socket, error) { if len(networks) == 0 { return nil, nil } var nahs []networkAndHost for _, n := range networks { nahs = append(nahs, networkAndHost{n, getHost(n.String())}) } for { ss, retry, err := listenAllRetry(nahs, port, f) if !retry { return ss, err } } } type networkAndHost struct { Network network Host string } func listenAllRetry(nahs []networkAndHost, port int, f firewallCallback) (ss []socket, retry bool, err error) { ss = make([]socket, 1, len(nahs)) portStr := strconv.FormatInt(int64(port), 10) ss[0], err = listen(nahs[0].Network, net.JoinHostPort(nahs[0].Host, portStr), f) if err != nil { return nil, false, errors.Wrap(err, "first listen") } defer func() { if err != nil || retry { for _, s := range ss { s.Close() } ss = nil } }() portStr = strconv.FormatInt(int64(missinggo.AddrPort(ss[0].Addr())), 10) for _, nah := range nahs[1:] { s, err := listen(nah.Network, net.JoinHostPort(nah.Host, portStr), f) if err != nil { return ss, missinggo.IsAddrInUse(err) && port == 0, errors.Wrap(err, "subsequent listen") } ss = append(ss, s) } return } type firewallCallback = utp.FirewallCallback func listenUtp(network, addr string, fc firewallCallback) (socket, error) { us, err := NewUtpSocket(network, addr, fc) return utpSocketSocket{us, network}, err } // utpSocket wrapper, additionally wrapped for the torrent package's socket interface. type utpSocketSocket struct { utpSocket network string } func (me utpSocketSocket) DialerNetwork() string { return me.network } func (me utpSocketSocket) Dial(ctx context.Context, addr string) (conn net.Conn, err error) { defer perf.ScopeTimerErr(&err)() return me.utpSocket.DialContext(ctx, me.network, addr) }