// Copyright (c) Tailscale Inc & AUTHORS // SPDX-License-Identifier: BSD-3-Clause // Package tsaddr handles Tailscale-specific IPs and ranges. package tsaddr import ( "encoding/binary" "errors" "net/netip" "slices" "sync" "go4.org/netipx" "tailscale.com/net/netaddr" "tailscale.com/types/views" ) // ChromeOSVMRange returns the subset of the CGNAT IPv4 range used by // ChromeOS to interconnect the host OS to containers and VMs. We // avoid allocating Tailscale IPs from it, to avoid conflicts. func ChromeOSVMRange() netip.Prefix { chromeOSRange.Do(func() { mustPrefix(&chromeOSRange.v, "100.115.92.0/23") }) return chromeOSRange.v } var chromeOSRange oncePrefix // CGNATRange returns the Carrier Grade NAT address range that // is the superset range that Tailscale assigns out of. // See https://tailscale.com/s/cgnat // Note that Tailscale does not assign out of the ChromeOSVMRange. func CGNATRange() netip.Prefix { cgnatRange.Do(func() { mustPrefix(&cgnatRange.v, "100.64.0.0/10") }) return cgnatRange.v } var ( cgnatRange oncePrefix tsUlaRange oncePrefix tsViaRange oncePrefix ula4To6Range oncePrefix ulaEph6Range oncePrefix serviceIPv6 oncePrefix ) // TailscaleServiceIP returns the IPv4 listen address of services // provided by Tailscale itself such as the MagicDNS proxy. // // For IPv6, use TailscaleServiceIPv6. func TailscaleServiceIP() netip.Addr { return netaddr.IPv4(100, 100, 100, 100) // "100.100.100.100" for those grepping } // TailscaleServiceIPv6 returns the IPv6 listen address of the services // provided by Tailscale itself such as the MagicDNS proxy. // // For IPv4, use TailscaleServiceIP. func TailscaleServiceIPv6() netip.Addr { serviceIPv6.Do(func() { mustPrefix(&serviceIPv6.v, TailscaleServiceIPv6String+"/128") }) return serviceIPv6.v.Addr() } const ( TailscaleServiceIPString = "100.100.100.100" TailscaleServiceIPv6String = "fd7a:115c:a1e0::53" ) // IsTailscaleIP reports whether ip is an IP address in a range that // Tailscale assigns from. func IsTailscaleIP(ip netip.Addr) bool { if ip.Is4() { return CGNATRange().Contains(ip) && !ChromeOSVMRange().Contains(ip) } return TailscaleULARange().Contains(ip) } // TailscaleULARange returns the IPv6 Unique Local Address range that // is the superset range that Tailscale assigns out of. func TailscaleULARange() netip.Prefix { tsUlaRange.Do(func() { mustPrefix(&tsUlaRange.v, "fd7a:115c:a1e0::/48") }) return tsUlaRange.v } // TailscaleViaRange returns the IPv6 Unique Local Address subset range // TailscaleULARange that's used for IPv4 tunneling via IPv6. func TailscaleViaRange() netip.Prefix { // Mnemonic: "b1a" sounds like "via". tsViaRange.Do(func() { mustPrefix(&tsViaRange.v, "fd7a:115c:a1e0:b1a::/64") }) return tsViaRange.v } // Tailscale4To6Range returns the subset of TailscaleULARange used for // auto-translated Tailscale ipv4 addresses. func Tailscale4To6Range() netip.Prefix { // This IP range has no significance, beyond being a subset of // TailscaleULARange. The bits from /48 to /104 were picked at // random. ula4To6Range.Do(func() { mustPrefix(&ula4To6Range.v, "fd7a:115c:a1e0:ab12:4843:cd96:6200::/104") }) return ula4To6Range.v } // TailscaleEphemeral6Range returns the subset of TailscaleULARange // used for ephemeral IPv6-only Tailscale nodes. func TailscaleEphemeral6Range() netip.Prefix { // This IP range has no significance, beyond being a subset of // TailscaleULARange. The bits from /48 to /64 were picked at // random, with the only criterion being to not be the conflict // with the Tailscale4To6Range above. ulaEph6Range.Do(func() { mustPrefix(&ulaEph6Range.v, "fd7a:115c:a1e0:efe3::/64") }) return ulaEph6Range.v } // Tailscale4To6Placeholder returns an IP address that can be used as // a source IP when one is required, but a netmap didn't provide // any. This address never gets allocated by the 4-to-6 algorithm in // control. // // Currently used to work around a Windows limitation when programming // IPv6 routes in corner cases. func Tailscale4To6Placeholder() netip.Addr { return Tailscale4To6Range().Addr() } // Tailscale4To6 returns a Tailscale IPv6 address that maps 1:1 to the // given Tailscale IPv4 address. Returns a zero IP if ipv4 isn't a // Tailscale IPv4 address. func Tailscale4To6(ipv4 netip.Addr) netip.Addr { if !ipv4.Is4() || !IsTailscaleIP(ipv4) { return netip.Addr{} } ret := Tailscale4To6Range().Addr().As16() v4 := ipv4.As4() copy(ret[13:], v4[1:]) return netip.AddrFrom16(ret) } // Tailscale6to4 returns the IPv4 address corresponding to the given // tailscale IPv6 address within the 4To6 range. The IPv4 address // and true are returned if the given address was in the correct range, // false if not. func Tailscale6to4(ipv6 netip.Addr) (netip.Addr, bool) { if !ipv6.Is6() || !Tailscale4To6Range().Contains(ipv6) { return netip.Addr{}, false } v6 := ipv6.As16() return netip.AddrFrom4([4]byte{100, v6[13], v6[14], v6[15]}), true } func mustPrefix(v *netip.Prefix, prefix string) { var err error *v, err = netip.ParsePrefix(prefix) if err != nil { panic(err) } } type oncePrefix struct { sync.Once v netip.Prefix } // PrefixesContainsIP reports whether any prefix in ipp contains ip. func PrefixesContainsIP(ipp []netip.Prefix, ip netip.Addr) bool { for _, r := range ipp { if r.Contains(ip) { return true } } return false } // PrefixIs4 reports whether p is an IPv4 prefix. func PrefixIs4(p netip.Prefix) bool { return p.Addr().Is4() } // PrefixIs6 reports whether p is an IPv6 prefix. func PrefixIs6(p netip.Prefix) bool { return p.Addr().Is6() } // ContainsExitRoutes reports whether rr contains both the IPv4 and // IPv6 /0 route. func ContainsExitRoutes(rr views.Slice[netip.Prefix]) bool { var v4, v6 bool for i := range rr.Len() { r := rr.At(i) if r == allIPv4 { v4 = true } else if r == allIPv6 { v6 = true } } return v4 && v6 } // ContainsExitRoute reports whether rr contains at least one of IPv4 or // IPv6 /0 (exit) routes. func ContainsExitRoute(rr views.Slice[netip.Prefix]) bool { for i := range rr.Len() { if rr.At(i).Bits() == 0 { return true } } return false } // ContainsNonExitSubnetRoutes reports whether v contains Subnet // Routes other than ExitNode Routes. func ContainsNonExitSubnetRoutes(rr views.Slice[netip.Prefix]) bool { for i := range rr.Len() { if rr.At(i).Bits() != 0 { return true } } return false } // WithoutExitRoutes returns rr unchanged if it has only 1 or 0 /0 // routes. If it has both IPv4 and IPv6 /0 routes, then it returns // a copy with all /0 routes removed. func WithoutExitRoutes(rr views.Slice[netip.Prefix]) views.Slice[netip.Prefix] { if !ContainsExitRoutes(rr) { return rr } var out []netip.Prefix for _, r := range rr.All() { if r.Bits() > 0 { out = append(out, r) } } return views.SliceOf(out) } // WithoutExitRoute returns rr unchanged if it has 0 /0 // routes. If it has a IPv4 or IPv6 /0 routes, then it returns // a copy with all /0 routes removed. func WithoutExitRoute(rr views.Slice[netip.Prefix]) views.Slice[netip.Prefix] { if !ContainsExitRoute(rr) { return rr } var out []netip.Prefix for _, r := range rr.All() { if r.Bits() > 0 { out = append(out, r) } } return views.SliceOf(out) } var ( allIPv4 = netip.MustParsePrefix("0.0.0.0/0") allIPv6 = netip.MustParsePrefix("::/0") ) // AllIPv4 returns 0.0.0.0/0. func AllIPv4() netip.Prefix { return allIPv4 } // AllIPv6 returns ::/0. func AllIPv6() netip.Prefix { return allIPv6 } // ExitRoutes returns a slice containing AllIPv4 and AllIPv6. func ExitRoutes() []netip.Prefix { return []netip.Prefix{allIPv4, allIPv6} } // IsExitRoute reports whether p is an exit node route. func IsExitRoute(p netip.Prefix) bool { return p == allIPv4 || p == allIPv6 } // SortPrefixes sorts the prefixes in place. func SortPrefixes(p []netip.Prefix) { slices.SortFunc(p, netipx.ComparePrefix) } // FilterPrefixes returns a new slice, not aliasing in, containing elements of // in that match f. func FilterPrefixesCopy(in views.Slice[netip.Prefix], f func(netip.Prefix) bool) []netip.Prefix { var out []netip.Prefix for i := range in.Len() { if v := in.At(i); f(v) { out = append(out, v) } } return out } // IsViaPrefix reports whether p is a CIDR in the Tailscale "via" range. // See TailscaleViaRange. func IsViaPrefix(p netip.Prefix) bool { return TailscaleViaRange().Contains(p.Addr()) } // UnmapVia returns the IPv4 address that corresponds to the provided Tailscale // "via" IPv4-in-IPv6 address. // // If ip is not a via address, it returns ip unchanged. func UnmapVia(ip netip.Addr) netip.Addr { if TailscaleViaRange().Contains(ip) { a := ip.As16() return netip.AddrFrom4(*(*[4]byte)(a[12:16])) } return ip } // MapVia returns an IPv6 "via" route for an IPv4 CIDR in a given siteID. func MapVia(siteID uint32, v4 netip.Prefix) (via netip.Prefix, err error) { if !v4.Addr().Is4() { return via, errors.New("want IPv4 CIDR with a site ID") } viaRange16 := TailscaleViaRange().Addr().As16() var a [16]byte copy(a[:], viaRange16[:8]) binary.BigEndian.PutUint32(a[8:], siteID) ip4a := v4.Addr().As4() copy(a[12:], ip4a[:]) return netip.PrefixFrom(netip.AddrFrom16(a), v4.Bits()+64+32), nil }