+ Dialer: &net.Dialer{
+ // Dialling TCP from a local port limits us to a single outgoing TCP connection to
+ // each remote client. Instead this should be a last resort if we need to use holepunching, and only then to connect to other clients that actually try to holepunch TCP.
+ //LocalAddr: l.Addr(),
+
+ // We don't want fallback, as we explicitly manage the IPv4/IPv6 distinction
+ // ourselves, although it's probably not triggered as I think the network is already
+ // constrained to tcp4 or tcp6 at this point.
+ FallbackDelay: -1,
+ // BitTorrent connections manage their own keep-alives.
+ KeepAlive: tcpListenConfig.KeepAlive,
+ Control: func(network, address string, c syscall.RawConn) (err error) {
+ controlErr := c.Control(func(fd uintptr) {
+ err = setSockNoLinger(fd)
+ if err != nil {
+ // Failing to disable linger is undesirable, but not fatal.
+ log.Printf("error setting linger socket option on tcp socket: %v", err)
+ }
+ err = setReusePortSockOpts(fd)
+ })
+ if err == nil {
+ err = controlErr
+ }
+ return
+ },
+ },