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tailscale/net/tsaddr/tsaddr.go

302 lines
8.9 KiB
Go

// 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"
"sync"
"go4.org/netipx"
"golang.org/x/exp/slices"
"tailscale.com/net/netaddr"
)
// 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
ulaRange 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
}
// NewContainsIPFunc returns a func that reports whether ip is in addrs.
//
// It's optimized for the cases of addrs being empty and addrs
// containing 1 or 2 single-IP prefixes (such as one IPv4 address and
// one IPv6 address).
//
// Otherwise the implementation is somewhat slow.
func NewContainsIPFunc(addrs []netip.Prefix) func(ip netip.Addr) bool {
// Specialize the three common cases: no address, just IPv4
// (or just IPv6), and both IPv4 and IPv6.
if len(addrs) == 0 {
return func(netip.Addr) bool { return false }
}
// If any addr is more than a single IP, then just do the slow
// linear thing until
// https://github.com/inetaf/netaddr/issues/139 is done.
for _, a := range addrs {
if a.IsSingleIP() {
continue
}
acopy := append([]netip.Prefix(nil), addrs...)
return func(ip netip.Addr) bool {
for _, a := range acopy {
if a.Contains(ip) {
return true
}
}
return false
}
}
// Fast paths for 1 and 2 IPs:
if len(addrs) == 1 {
a := addrs[0]
return func(ip netip.Addr) bool { return ip == a.Addr() }
}
if len(addrs) == 2 {
a, b := addrs[0], addrs[1]
return func(ip netip.Addr) bool { return ip == a.Addr() || ip == b.Addr() }
}
// General case:
m := map[netip.Addr]bool{}
for _, a := range addrs {
m[a.Addr()] = true
}
return func(ip netip.Addr) bool { return m[ip] }
}
// 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 []netip.Prefix) bool {
var v4, v6 bool
for _, r := range rr {
if r == allIPv4 {
v4 = true
} else if r == allIPv6 {
v6 = true
}
}
return v4 && v6
}
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} }
// 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 []netip.Prefix, f func(netip.Prefix) bool) []netip.Prefix {
var out []netip.Prefix
for _, v := range in {
if 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
}