fix: ipv{4,6}-only listen on wildcard address

fix: #797

when listening on a wildcard address like "0.0.0.0" or "[::]", hysteria
actually listened on both IPv4 and IPv6. this is a well-known bug of the
golang net package.

this commit introduces a fix for that, the intended behavior will be:

0.0.0.0:443 => listen on IPv4 only
[::]:443    => listen on IPv6 only
:443        => listen on both IPv4 and IPv6

extras/correctnet/correctnet.go

@@ -0,0 +1,92 @@
+package correctnet
+
+import (
+	"net"
+	"net/http"
+	"strings"
+)
+
+func extractIPFamily(ip net.IP) (family string) {
+	if len(ip) == 0 {
+		// real family independent wildcard address, such as ":443"
+		return ""
+	}
+	if p4 := ip.To4(); len(p4) == net.IPv4len {
+		return "4"
+	}
+	return "6"
+}
+
+func tcpAddrNetwork(addr *net.TCPAddr) (network string) {
+	if addr == nil {
+		return "tcp"
+	}
+	return "tcp" + extractIPFamily(addr.IP)
+}
+
+func udpAddrNetwork(addr *net.UDPAddr) (network string) {
+	if addr == nil {
+		return "udp"
+	}
+	return "udp" + extractIPFamily(addr.IP)
+}
+
+func ipAddrNetwork(addr *net.IPAddr) (network string) {
+	if addr == nil {
+		return "ip"
+	}
+	return "ip" + extractIPFamily(addr.IP)
+}
+
+func Listen(network string, address string) (net.Listener, error) {
+	if network == "tcp" {
+		tcpAddr, err := net.ResolveTCPAddr(network, address)
+		if err != nil {
+			return nil, err
+		}
+		return ListenTCP(network, tcpAddr)
+	}
+	return net.Listen(network, address)
+}
+
+func ListenTCP(network string, laddr *net.TCPAddr) (*net.TCPListener, error) {
+	if network == "tcp" {
+		return net.ListenTCP(tcpAddrNetwork(laddr), laddr)
+	}
+	return net.ListenTCP(network, laddr)
+}
+
+func ListenPacket(network string, address string) (listener net.PacketConn, err error) {
+	if network == "udp" {
+		udpAddr, err := net.ResolveUDPAddr(network, address)
+		if err != nil {
+			return nil, err
+		}
+		return ListenUDP(network, udpAddr)
+	}
+	if strings.HasPrefix(network, "ip:") {
+		proto := network[3:]
+		ipAddr, err := net.ResolveIPAddr(proto, address)
+		if err != nil {
+			return nil, err
+		}
+		return net.ListenIP(ipAddrNetwork(ipAddr)+":"+proto, ipAddr)
+	}
+	return net.ListenPacket(network, address)
+}
+
+func ListenUDP(network string, laddr *net.UDPAddr) (*net.UDPConn, error) {
+	if network == "udp" {
+		return net.ListenUDP(udpAddrNetwork(laddr), laddr)
+	}
+	return net.ListenUDP(network, laddr)
+}
+
+func HTTPListenAndServe(address string, handler http.Handler) (err error) {
+	listener, err := Listen("tcp", address)
+	if err != nil {
+		return err
+	}
+	defer listener.Close()
+	return http.Serve(listener, handler)
+}