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net/tsaddr, wgengine/netstack: add IPv6 range that forwards to site-relative IPv4

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This defines a new magic IPv6 prefix, fd7a:115c:a1e0:b1a::/64, a
subset of our existing /48, where the final 32 bits are an IPv4
address, and the middle 32 bits are a user-chosen "site ID". (which
must currently be 0000:00xx; the top 3 bytes must be zero for now)

e.g., I can say my home LAN's "site ID" is "0000:00bb" and then
advertise its 10.2.0.0/16 IPv4 range via IPv6, like:

    tailscale up --advertise-routes=fd7a:115c:a1e0:b1a::bb:10.2.0.0/112

(112 being /128 minuse the /96 v6 prefix length)

Then people in my tailnet can:

     $ curl '[fd7a:115c:a1e0:b1a::bb:10.2.0.230]'
     <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" ....

Updates #3616, etc

RELNOTE=initial support for TS IPv6 addresses to route v4 "via" specific nodes

Change-Id: I9b49b6ad10410a24b5866b9fbc69d3cae1f600ef
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2022-03-30 08:47:16 -07:00 committed by Brad Fitzpatrick
parent f992749b98
commit 3ae701f0eb
6 changed files with 156 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
cmd/tailscale/cli/cli_test.go
View File

@ -659,6 +659,39 @@ func TestPrefsFromUpArgs(t *testing.T) {
NoSNAT: true,
},
},
{
name: "via_route_good",
goos: "linux",
args: upArgsT{
advertiseRoutes: "fd7a:115c:a1e0:b1a::bb:10.0.0.0/112",
netfilterMode: "off",
},
want: &ipn.Prefs{
WantRunning: true,
NoSNAT: true,
AdvertiseRoutes: []netaddr.IPPrefix{
netaddr.MustParseIPPrefix("fd7a:115c:a1e0:b1a::bb:10.0.0.0/112"),
},
},
},
{
name: "via_route_short_prefix",
goos: "linux",
args: upArgsT{
advertiseRoutes: "fd7a:115c:a1e0:b1a::/64",
netfilterMode: "off",
},
wantErr: "fd7a:115c:a1e0:b1a::/64 4-in-6 prefix must be at least a /96",
},
{
name: "via_route_short_reserved_siteid",
goos: "linux",
args: upArgsT{
advertiseRoutes: "fd7a:115c:a1e0:b1a:1234:5678::/112",
netfilterMode: "off",
},
wantErr: "route fd7a:115c:a1e0:b1a:1234:5678::/112 contains invalid site ID 12345678; must be 0xff or less",
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {

27
cmd/tailscale/cli/up.go
View File

@ -7,6 +7,7 @@
import (
"context"
"encoding/base64"
"encoding/binary"
"encoding/json"
"errors"
"flag"
@ -27,6 +28,7 @@
"tailscale.com/envknob"
"tailscale.com/ipn"
"tailscale.com/ipn/ipnstate"
"tailscale.com/net/tsaddr"
"tailscale.com/safesocket"
"tailscale.com/tailcfg"
"tailscale.com/types/logger"
@ -201,6 +203,26 @@ func warnf(format string, args ...any) {
ipv6default = netaddr.MustParseIPPrefix("::/0")
)
func validateViaPrefix(ipp netaddr.IPPrefix) error {
if !tsaddr.IsViaPrefix(ipp) {
return fmt.Errorf("%v is not a 4-in-6 prefix", ipp)
}
if ipp.Bits() < (128 - 32) {
return fmt.Errorf("%v 4-in-6 prefix must be at least a /%v", ipp, 128-32)
}
a := ipp.IP().As16()
// The first 64 bits of a are the via prefix.
// The next 32 bits are the "site ID".
// The last 32 bits are the IPv4.
// For now, we reserve the top 3 bytes of the site ID,
// and only allow users to use site IDs 0-255.
siteID := binary.BigEndian.Uint32(a[8:12])
if siteID > 0xFF {
return fmt.Errorf("route %v contains invalid site ID %08x; must be 0xff or less", ipp, siteID)
}
return nil
}
func calcAdvertiseRoutes(advertiseRoutes string, advertiseDefaultRoute bool) ([]netaddr.IPPrefix, error) {
routeMap := map[netaddr.IPPrefix]bool{}
if advertiseRoutes != "" {
@ -214,6 +236,11 @@ func calcAdvertiseRoutes(advertiseRoutes string, advertiseDefaultRoute bool) ([]
if ipp != ipp.Masked() {
return nil, fmt.Errorf("%s has non-address bits set; expected %s", ipp, ipp.Masked())
}
if tsaddr.IsViaPrefix(ipp) {
if err := validateViaPrefix(ipp); err != nil {
return nil, err
}
}
if ipp == ipv4default {
default4 = true
} else if ipp == ipv6default {

31
ipn/ipnlocal/local.go
View File

@ -106,7 +106,8 @@ type LocalBackend struct {
filterHash deephash.Sum
filterAtomic atomic.Value // of *filter.Filter
filterAtomic atomic.Value // of *filter.Filter
containsViaIPFuncAtomic atomic.Value // of func(netaddr.IP) bool
// The mutex protects the following elements.
mu sync.Mutex
@ -1573,11 +1574,23 @@ func (b *LocalBackend) loadStateLocked(key ipn.StateKey, prefs *ipn.Prefs) (err
b.logf("using backend prefs for %q: %s", key, b.prefs.Pretty())
b.sshAtomicBool.Set(b.prefs != nil && b.prefs.RunSSH && canSSH)
b.setAtomicValuesFromPrefs(b.prefs)
return nil
}
// setAtomicValuesFromPrefs populates sshAtomicBool and containsViaIPFuncAtomic
// from the prefs p, which may be nil.
func (b *LocalBackend) setAtomicValuesFromPrefs(p *ipn.Prefs) {
b.sshAtomicBool.Set(p != nil && p.RunSSH && canSSH)
if p == nil {
b.containsViaIPFuncAtomic.Store(tsaddr.NewContainsIPFunc(nil))
} else {
b.containsViaIPFuncAtomic.Store(tsaddr.NewContainsIPFunc(tsaddr.FilterPrefixesCopy(p.AdvertiseRoutes, tsaddr.IsViaPrefix)))
}
}
// State returns the backend state machine's current state.
func (b *LocalBackend) State() ipn.State {
b.mu.Lock()
@ -1746,7 +1759,7 @@ func (b *LocalBackend) setPrefsLockedOnEntry(caller string, newp *ipn.Prefs) {
netMap := b.netMap
stateKey := b.stateKey
b.sshAtomicBool.Set(newp.RunSSH && canSSH)
b.setAtomicValuesFromPrefs(newp)
oldp := b.prefs
newp.Persist = oldp.Persist // caller isn't allowed to override this
@ -2690,11 +2703,21 @@ func (b *LocalBackend) ResetForClientDisconnect() {
b.authURL = ""
b.authURLSticky = ""
b.activeLogin = ""
b.sshAtomicBool.Set(false)
b.setAtomicValuesFromPrefs(nil)
}
func (b *LocalBackend) ShouldRunSSH() bool { return b.sshAtomicBool.Get() && canSSH }
// ShouldHandleViaIP reports whether whether ip is an IPv6 address in the
// Tailscale ULA's v6 "via" range embedding an IPv4 address to be forwarded to
// by Tailscale.
func (b *LocalBackend) ShouldHandleViaIP(ip netaddr.IP) bool {
if f, ok := b.containsViaIPFuncAtomic.Load().(func(netaddr.IP) bool); ok {
return f(ip)
}
return false
}
// Logout tells the controlclient that we want to log out, and
// transitions the local engine to the logged-out state without
// waiting for controlclient to be in that state.

39
net/tsaddr/tsaddr.go
View File

@ -34,6 +34,7 @@ func CGNATRange() netaddr.IPPrefix {
cgnatRange oncePrefix
ulaRange oncePrefix
tsUlaRange oncePrefix
tsViaRange oncePrefix
ula4To6Range oncePrefix
ulaEph6Range oncePrefix
serviceIPv6 oncePrefix
@ -72,6 +73,14 @@ func TailscaleULARange() netaddr.IPPrefix {
return tsUlaRange.v
}
// TailscaleViaRange returns the IPv6 Unique Local Address subset range
// TailscaleULARange that's used for IPv4 tunneling via IPv6.
func TailscaleViaRange() netaddr.IPPrefix {
// 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() netaddr.IPPrefix {
@ -241,3 +250,33 @@ func AllIPv6() netaddr.IPPrefix { return allIPv6 }
// ExitRoutes returns a slice containing AllIPv4 and AllIPv6.
func ExitRoutes() []netaddr.IPPrefix { return []netaddr.IPPrefix{allIPv4, allIPv6} }
// FilterPrefixes returns a new slice, not aliasing in, containing elements of
// in that match f.
func FilterPrefixesCopy(in []netaddr.IPPrefix, f func(netaddr.IPPrefix) bool) []netaddr.IPPrefix {
var out []netaddr.IPPrefix
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 netaddr.IPPrefix) bool {
return TailscaleViaRange().Contains(p.IP())
}
// 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 netaddr.IP) netaddr.IP {
if TailscaleViaRange().Contains(ip) {
a := ip.As16()
return netaddr.IPFrom4(*(*[4]byte)(a[12:16]))
}
return ip
}

16
net/tsaddr/tsaddr_test.go
View File

@ -88,3 +88,19 @@ func BenchmarkTailscaleServiceAddr(b *testing.B) {
sinkIP = TailscaleServiceIP()
}
}
func TestUnmapVia(t *testing.T) {
tests := []struct {
ip string
want string
}{
{"1.2.3.4", "1.2.3.4"}, // unchanged v4
{"fd7a:115c:a1e0:b1a::bb:10.2.1.3", "10.2.1.3"},
{"fd7a:115c:a1e0:b1b::bb:10.2.1.4", "fd7a:115c:a1e0:b1b:0:bb:a02:104"}, // "b1b",not "bia"
}
for _, tt := range tests {
if got := UnmapVia(netaddr.MustParseIP(tt.ip)).String(); got != tt.want {
t.Errorf("for %q: got %q, want %q", tt.ip, got, tt.want)
}
}
}

14
wgengine/netstack/netstack.go
View File

@ -431,6 +431,8 @@ func (ns *Impl) peerAPIPortAtomic(ip netaddr.IP) *uint32 {
}
}
var viaRange = tsaddr.TailscaleViaRange()
// shouldProcessInbound reports whether an inbound packet should be
// handled by netstack.
func (ns *Impl) shouldProcessInbound(p *packet.Parsed, t *tstun.Wrapper) bool {
@ -453,6 +455,9 @@ func (ns *Impl) shouldProcessInbound(p *packet.Parsed, t *tstun.Wrapper) bool {
if ns.isInboundTSSH(p) && ns.processSSH() {
return true
}
if p.IPVersion == 6 && viaRange.Contains(p.Dst.IP()) {
return ns.lb != nil && ns.lb.ShouldHandleViaIP(p.Dst.IP())
}
if !ns.ProcessLocalIPs && !ns.ProcessSubnets {
// Fast path for common case (e.g. Linux server in TUN mode) where
// netstack isn't used at all; don't even do an isLocalIP lookup.
@ -624,6 +629,12 @@ func (ns *Impl) acceptTCP(r *tcp.ForwarderRequest) {
dialIP := netaddrIPFromNetstackIP(reqDetails.LocalAddress)
isTailscaleIP := tsaddr.IsTailscaleIP(dialIP)
if viaRange.Contains(dialIP) {
isTailscaleIP = false
dialIP = tsaddr.UnmapVia(dialIP)
}
defer func() {
if !isTailscaleIP {
// if this is a subnet IP, we added this in before the TCP handshake
@ -775,6 +786,9 @@ func (ns *Impl) forwardUDP(client *gonet.UDPConn, wq *waiter.Queue, clientAddr,
backendRemoteAddr = &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: int(port)}
backendListenAddr = &net.UDPAddr{IP: net.ParseIP("127.0.0.1"), Port: int(srcPort)}
} else {
if dstIP := dstAddr.IP(); viaRange.Contains(dstIP) {
dstAddr = netaddr.IPPortFrom(tsaddr.UnmapVia(dstIP), dstAddr.Port())
}
backendRemoteAddr = dstAddr.UDPAddr()
if dstAddr.IP().Is4() {
backendListenAddr = &net.UDPAddr{IP: net.ParseIP("0.0.0.0"), Port: int(srcPort)}