fix: tun failed on linux when ipv6.disable=1

app/internal/tun/check_ipv6_others.go

@@ -0,0 +1,14 @@
+//go:build !unix && !windows
+
+package tun
+
+import "net"
+
+func isIPv6Supported() bool {
+	lis, err := net.ListenPacket("udp6", "[::1]:0")
+	if err != nil {
+		return false
+	}
+	_ = lis.Close()
+	return true
+}

app/internal/tun/check_ipv6_unix.go

@@ -0,0 +1,16 @@
+//go:build unix
+
+package tun
+
+import (
+	"golang.org/x/sys/unix"
+)
+
+func isIPv6Supported() bool {
+	sock, err := unix.Socket(unix.AF_INET6, unix.SOCK_DGRAM, unix.IPPROTO_UDP)
+	if err != nil {
+		return false
+	}
+	_ = unix.Close(sock)
+	return true
+}

app/internal/tun/check_ipv6_windows.go

@@ -0,0 +1,24 @@
+//go:build windows
+
+package tun
+
+import (
+	"golang.org/x/sys/windows"
+)
+
+func isIPv6Supported() bool {
+	var wsaData windows.WSAData
+	err := windows.WSAStartup(uint32(0x202), &wsaData)
+	if err != nil {
+		// Failing silently: it is not our duty to report such errors
+		return true
+	}
+	defer windows.WSACleanup()
+
+	sock, err := windows.Socket(windows.AF_INET6, windows.SOCK_DGRAM, windows.IPPROTO_UDP)
+	if err != nil {
+		return false
+	}
+	_ = windows.Closesocket(sock)
+	return true
+}

app/internal/tun/server.go

@@ -49,6 +49,10 @@ type EventLogger interface {
 }
 
 func (s *Server) Serve() error {
+	if !isIPv6Supported() {
+		s.Logger.Warn("tun-pre-check", zap.String("msg", "IPv6 is not supported or enabled on this system, TUN device is created without IPv6 support."))
+		s.Inet6Address = nil
+	}
 	tunOpts := tun.Options{
 		Name:                     s.IfName,
 		Inet4Address:             s.Inet4Address,