// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. // Package interfaces contains helpers for looking up system network interfaces. package interfaces import ( "bytes" "fmt" "net" "net/http" "runtime" "sort" "strings" "inet.af/netaddr" "tailscale.com/net/tsaddr" "tailscale.com/net/tshttpproxy" ) // LoginEndpointForProxyDetermination is the URL used for testing // which HTTP proxy the system should use. var LoginEndpointForProxyDetermination = "https://login.tailscale.com/" // Tailscale returns the current machine's Tailscale interface, if any. // If none is found, all zero values are returned. // A non-nil error is only returned on a problem listing the system interfaces. func Tailscale() ([]netaddr.IP, *net.Interface, error) { ifs, err := net.Interfaces() if err != nil { return nil, nil, err } for _, iface := range ifs { if !maybeTailscaleInterfaceName(iface.Name) { continue } addrs, err := iface.Addrs() if err != nil { continue } var tsIPs []netaddr.IP for _, a := range addrs { if ipnet, ok := a.(*net.IPNet); ok { nip, ok := netaddr.FromStdIP(ipnet.IP) if ok && tsaddr.IsTailscaleIP(nip) { tsIPs = append(tsIPs, nip) } } } if len(tsIPs) > 0 { return tsIPs, &iface, nil } } return nil, nil, nil } // maybeTailscaleInterfaceName reports whether s is an interface // name that might be used by Tailscale. func maybeTailscaleInterfaceName(s string) bool { return s == "Tailscale" || strings.HasPrefix(s, "wg") || strings.HasPrefix(s, "ts") || strings.HasPrefix(s, "tailscale") || strings.HasPrefix(s, "utun") } func isUp(nif *net.Interface) bool { return nif.Flags&net.FlagUp != 0 } func isLoopback(nif *net.Interface) bool { return nif.Flags&net.FlagLoopback != 0 } func isProblematicInterface(nif *net.Interface) bool { name := nif.Name // Don't try to send disco/etc packets over zerotier; they effectively // DoS each other by doing traffic amplification, both of them // preferring/trying to use each other for transport. See: // https://github.com/tailscale/tailscale/issues/1208 if strings.HasPrefix(name, "zt") || (runtime.GOOS == "windows" && strings.Contains(name, "ZeroTier")) { return true } return false } // LocalAddresses returns the machine's IP addresses, separated by // whether they're loopback addresses. func LocalAddresses() (regular, loopback []netaddr.IP, err error) { // TODO(crawshaw): don't serve interface addresses that we are routing ifaces, err := net.Interfaces() if err != nil { return nil, nil, err } for i := range ifaces { iface := &ifaces[i] if !isUp(iface) || isProblematicInterface(iface) { // Skip down interfaces and ones that are // problematic that we don't want to try to // send Tailscale traffic over. continue } ifcIsLoopback := isLoopback(iface) addrs, err := iface.Addrs() if err != nil { return nil, nil, err } for _, a := range addrs { switch v := a.(type) { case *net.IPNet: ip, ok := netaddr.FromStdIP(v.IP) if !ok { continue } // TODO(apenwarr): don't special case cgNAT. // In the general wireguard case, it might // very well be something we can route to // directly, because both nodes are // behind the same CGNAT router. if tsaddr.IsTailscaleIP(ip) { continue } if ip.IsLinkLocalUnicast() { continue } if ip.IsLoopback() || ifcIsLoopback { loopback = append(loopback, ip) } else { regular = append(regular, ip) } } } } sortIPs(regular) sortIPs(loopback) return regular, loopback, nil } func sortIPs(s []netaddr.IP) { sort.Slice(s, func(i, j int) bool { return s[i].Less(s[j]) }) } // Interface is a wrapper around Go's net.Interface with some extra methods. type Interface struct { *net.Interface } func (i Interface) IsLoopback() bool { return isLoopback(i.Interface) } func (i Interface) IsUp() bool { return isUp(i.Interface) } // ForeachInterfaceAddress calls fn for each interface's address on // the machine. The IPPrefix's IP is the IP address assigned to the // interface, and Bits are the subnet mask. func ForeachInterfaceAddress(fn func(Interface, netaddr.IPPrefix)) error { ifaces, err := net.Interfaces() if err != nil { return err } for i := range ifaces { iface := &ifaces[i] addrs, err := iface.Addrs() if err != nil { return err } for _, a := range addrs { switch v := a.(type) { case *net.IPNet: if pfx, ok := netaddr.FromStdIPNet(v); ok { fn(Interface{iface}, pfx) } } } } return nil } // ForeachInterface calls fn for each interface on the machine, with // all its addresses. The IPPrefix's IP is the IP address assigned to // the interface, and Bits are the subnet mask. func ForeachInterface(fn func(Interface, []netaddr.IPPrefix)) error { ifaces, err := net.Interfaces() if err != nil { return err } for i := range ifaces { iface := &ifaces[i] addrs, err := iface.Addrs() if err != nil { return err } var pfxs []netaddr.IPPrefix for _, a := range addrs { switch v := a.(type) { case *net.IPNet: if pfx, ok := netaddr.FromStdIPNet(v); ok { pfxs = append(pfxs, pfx) } } } sort.Slice(pfxs, func(i, j int) bool { return pfxs[i].IP().Less(pfxs[j].IP()) }) fn(Interface{iface}, pfxs) } return nil } // State is intended to store the state of the machine's network interfaces, // routing table, and other network configuration. // For now it's pretty basic. type State struct { // InterfaceIPs maps from an interface name to the IP addresses // configured on that interface. Each address is represented as an // IPPrefix, where the IP is the interface IP address and Bits is // the subnet mask. InterfaceIPs map[string][]netaddr.IPPrefix Interface map[string]Interface // HaveV6Global is whether this machine has an IPv6 global address // on some non-Tailscale interface that's up. HaveV6Global bool // HaveV4 is whether the machine has some non-localhost, // non-link-local IPv4 address on a non-Tailscale interface that's up. HaveV4 bool // IsExpensive is whether the current network interface is // considered "expensive", which currently means LTE/etc // instead of Wifi. This field is not populated by GetState. IsExpensive bool // DefaultRouteInterface is the interface name for the machine's default route. // It is not yet populated on all OSes. // Its exact value should not be assumed to be a map key for // the Interface maps above; it's only used for debugging. DefaultRouteInterface string // HTTPProxy is the HTTP proxy to use. HTTPProxy string // PAC is the URL to the Proxy Autoconfig URL, if applicable. PAC string } func (s *State) String() string { var sb strings.Builder fmt.Fprintf(&sb, "interfaces.State{defaultRoute=%v ifs={", s.DefaultRouteInterface) ifs := make([]string, 0, len(s.Interface)) for k := range s.Interface { if anyInterestingIP(s.InterfaceIPs[k]) { ifs = append(ifs, k) } } sort.Slice(ifs, func(i, j int) bool { upi, upj := s.Interface[ifs[i]].IsUp(), s.Interface[ifs[j]].IsUp() if upi != upj { // Up sorts before down. return upi } return ifs[i] < ifs[j] }) for i, ifName := range ifs { if i > 0 { sb.WriteString(" ") } if s.Interface[ifName].IsUp() { fmt.Fprintf(&sb, "%s:[", ifName) needSpace := false for _, pfx := range s.InterfaceIPs[ifName] { if !isInterestingIP(pfx.IP()) { continue } if needSpace { sb.WriteString(" ") } fmt.Fprintf(&sb, "%s", pfx) needSpace = true } sb.WriteString("]") } else { fmt.Fprintf(&sb, "%s:down", ifName) } } sb.WriteString("}") if s.IsExpensive { sb.WriteString(" expensive") } if s.HTTPProxy != "" { fmt.Fprintf(&sb, " httpproxy=%s", s.HTTPProxy) } if s.PAC != "" { fmt.Fprintf(&sb, " pac=%s", s.PAC) } fmt.Fprintf(&sb, " v4=%v v6global=%v}", s.HaveV4, s.HaveV6Global) return sb.String() } // EqualFiltered reports whether s and s2 are equal, // considering only interfaces in s for which filter returns true. func (s *State) EqualFiltered(s2 *State, filter func(i Interface, ips []netaddr.IPPrefix) bool) bool { if s == nil && s2 == nil { return true } if s == nil || s2 == nil { return false } if s.HaveV6Global != s2.HaveV6Global || s.HaveV4 != s2.HaveV4 || s.IsExpensive != s2.IsExpensive || s.DefaultRouteInterface != s2.DefaultRouteInterface || s.HTTPProxy != s2.HTTPProxy || s.PAC != s2.PAC { return false } for iname, i := range s.Interface { ips := s.InterfaceIPs[iname] if !filter(i, ips) { continue } i2, ok := s2.Interface[iname] if !ok { return false } ips2, ok := s2.InterfaceIPs[iname] if !ok { return false } if !interfacesEqual(i, i2) || !prefixesEqual(ips, ips2) { return false } } return true } func interfacesEqual(a, b Interface) bool { return a.Index == b.Index && a.MTU == b.MTU && a.Name == b.Name && a.Flags == b.Flags && bytes.Equal([]byte(a.HardwareAddr), []byte(b.HardwareAddr)) } func prefixesEqual(a, b []netaddr.IPPrefix) bool { if len(a) != len(b) { return false } for i, v := range a { if b[i] != v { return false } } return true } // FilterInteresting reports whether i is an interesting non-Tailscale interface. func FilterInteresting(i Interface, ips []netaddr.IPPrefix) bool { return !isTailscaleInterface(i.Name, ips) && anyInterestingIP(ips) } // FilterAll always returns true, to use EqualFiltered against all interfaces. func FilterAll(i Interface, ips []netaddr.IPPrefix) bool { return true } func (s *State) HasPAC() bool { return s != nil && s.PAC != "" } // AnyInterfaceUp reports whether any interface seems like it has Internet access. func (s *State) AnyInterfaceUp() bool { return s != nil && (s.HaveV4 || s.HaveV6Global) } func hasTailscaleIP(pfxs []netaddr.IPPrefix) bool { for _, pfx := range pfxs { if tsaddr.IsTailscaleIP(pfx.IP()) { return true } } return false } func isTailscaleInterface(name string, ips []netaddr.IPPrefix) bool { if runtime.GOOS == "darwin" && strings.HasPrefix(name, "utun") && hasTailscaleIP(ips) { // On macOS in the sandboxed app (at least as of // 2021-02-25), we often see two utun devices // (e.g. utun4 and utun7) with the same IPv4 and IPv6 // addresses. Just remove all utun devices with // Tailscale IPs until we know what's happening with // macOS NetworkExtensions and utun devices. return true } return name == "Tailscale" || // as it is on Windows strings.HasPrefix(name, "tailscale") // TODO: use --tun flag value, etc; see TODO in method doc } // getPAC, if non-nil, returns the current PAC file URL. var getPAC func() string // GetState returns the state of all the current machine's network interfaces. // // It does not set the returned State.IsExpensive. The caller can populate that. func GetState() (*State, error) { s := &State{ InterfaceIPs: make(map[string][]netaddr.IPPrefix), Interface: make(map[string]Interface), } if err := ForeachInterface(func(ni Interface, pfxs []netaddr.IPPrefix) { ifUp := ni.IsUp() s.Interface[ni.Name] = ni s.InterfaceIPs[ni.Name] = append(s.InterfaceIPs[ni.Name], pfxs...) if !ifUp || isTailscaleInterface(ni.Name, pfxs) { return } for _, pfx := range pfxs { if pfx.IP().IsLoopback() || pfx.IP().IsLinkLocalUnicast() { continue } s.HaveV6Global = s.HaveV6Global || isGlobalV6(pfx.IP()) s.HaveV4 = s.HaveV4 || pfx.IP().Is4() } }); err != nil { return nil, err } s.DefaultRouteInterface, _ = DefaultRouteInterface() if s.AnyInterfaceUp() { req, err := http.NewRequest("GET", LoginEndpointForProxyDetermination, nil) if err != nil { return nil, err } if u, err := tshttpproxy.ProxyFromEnvironment(req); err == nil && u != nil { s.HTTPProxy = u.String() } if getPAC != nil { s.PAC = getPAC() } } return s, nil } // HTTPOfListener returns the HTTP address to ln. // If the listener is listening on the unspecified address, it // it tries to find a reasonable interface address on the machine to use. func HTTPOfListener(ln net.Listener) string { ta, ok := ln.Addr().(*net.TCPAddr) if !ok || !ta.IP.IsUnspecified() { return fmt.Sprintf("http://%v/", ln.Addr()) } var goodIP string var privateIP string ForeachInterfaceAddress(func(i Interface, pfx netaddr.IPPrefix) { ip := pfx.IP() if isPrivateIP(ip) { if privateIP == "" { privateIP = ip.String() } return } goodIP = ip.String() }) if privateIP != "" { goodIP = privateIP } if goodIP != "" { return fmt.Sprintf("http://%v/", net.JoinHostPort(goodIP, fmt.Sprint(ta.Port))) } return fmt.Sprintf("http://localhost:%v/", fmt.Sprint(ta.Port)) } var likelyHomeRouterIP func() (netaddr.IP, bool) // LikelyHomeRouterIP returns the likely IP of the residential router, // which will always be an IPv4 private address, if found. // In addition, it returns the IP address of the current machine on // the LAN using that gateway. // This is used as the destination for UPnP, NAT-PMP, PCP, etc queries. func LikelyHomeRouterIP() (gateway, myIP netaddr.IP, ok bool) { if likelyHomeRouterIP != nil { gateway, ok = likelyHomeRouterIP() if !ok { return } } if !ok { return } ForeachInterfaceAddress(func(i Interface, pfx netaddr.IPPrefix) { ip := pfx.IP() if !i.IsUp() || ip.IsZero() || !myIP.IsZero() { return } for _, prefix := range privatev4s { if prefix.Contains(gateway) && prefix.Contains(ip) { myIP = ip ok = true return } } }) return gateway, myIP, !myIP.IsZero() } func isPrivateIP(ip netaddr.IP) bool { return private1.Contains(ip) || private2.Contains(ip) || private3.Contains(ip) } func isGlobalV6(ip netaddr.IP) bool { return v6Global1.Contains(ip) || (tsaddr.IsULA(ip) && !tsaddr.TailscaleULARange().Contains(ip)) } func mustCIDR(s string) netaddr.IPPrefix { prefix, err := netaddr.ParseIPPrefix(s) if err != nil { panic(err) } return prefix } var ( private1 = mustCIDR("10.0.0.0/8") private2 = mustCIDR("172.16.0.0/12") private3 = mustCIDR("192.168.0.0/16") privatev4s = []netaddr.IPPrefix{private1, private2, private3} v6Global1 = mustCIDR("2000::/3") ) // anyInterestingIP reports whether pfxs contains any IP that matches // isInterestingIP. func anyInterestingIP(pfxs []netaddr.IPPrefix) bool { for _, pfx := range pfxs { if isInterestingIP(pfx.IP()) { return true } } return false } // isInterestingIP reports whether ip is an interesting IP that we // should log in interfaces.State logging. We don't need to show // localhost or link-local addresses. func isInterestingIP(ip netaddr.IP) bool { if ip.IsLoopback() || ip.IsLinkLocalUnicast() { return false } return true }