Sockopt: Allow v6only work for Windows & Drawin (#4571)

Completes #1677

---------

Co-authored-by: RPRX <63339210+RPRX@users.noreply.github.com>

Author: xqzr

transport/internet/sockopt_darwin.go

@@ -200,6 +200,12 @@ func applyInboundSocketOptions(network string, fd uintptr, config *SocketConfig)
 		}
 	}
 
+	if config.V6Only {
+		if err := unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_V6ONLY, 1); err != nil {
+			return errors.New("failed to set IPV6_V6ONLY").Base(err)
+		}
+	}
+
 	return nil
 }
 

transport/internet/sockopt_windows.go

@@ -15,6 +15,7 @@ const (
 	IPV6_UNICAST_IF = 31
 	IP_MULTICAST_IF = 9
 	IPV6_MULTICAST_IF = 9
+	IPV6_V6ONLY = 27
 )
 
 func setTFO(fd syscall.Handle, tfo int) error {
@@ -90,6 +91,12 @@ func applyInboundSocketOptions(network string, fd uintptr, config *SocketConfig)
 		}
 	}
 
+	if config.V6Only {
+		if err := syscall.SetsockoptInt(syscall.Handle(fd), syscall.IPPROTO_IPV6, IPV6_V6ONLY, 1); err != nil {
+			return errors.New("failed to set IPV6_V6ONLY").Base(err)
+		}
+	}
+
 	return nil
 }