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tsaddr: add helpers for the Tailscale IPv6 range, and 4to6 conversion.

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Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson 2020-10-15 21:12:23 +00:00 committed by Dave Anderson
parent c6dbd24f67
commit 5c35c35e7f
1 changed files with 39 additions and 2 deletions
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41
net/tsaddr/tsaddr.go
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@ -30,7 +30,11 @@ func CGNATRange() netaddr.IPPrefix {
return cgnatRange.v
}
var cgnatRange oncePrefix
var (
cgnatRange oncePrefix
ulaRange oncePrefix
ula4To6Range oncePrefix
)
// TailscaleServiceIP returns the listen address of services
// provided by Tailscale itself such as the Magic DNS proxy.
@ -44,7 +48,40 @@ func TailscaleServiceIP() netaddr.IP {
// IsTailscaleIP reports whether ip is an IP address in a range that
// Tailscale assigns from.
func IsTailscaleIP(ip netaddr.IP) bool {
return CGNATRange().Contains(ip) && !ChromeOSVMRange().Contains(ip)
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() netaddr.IPPrefix {
ulaRange.Do(func() { mustPrefix(&ulaRange.v, "fd7a:115c:a1e0::/48") })
return ulaRange.v
}
// Tailscale4To6Range returns the subset of TailscaleULARange used for
// auto-translated Tailscale ipv4 addresses.
func Tailscale4To6Range() netaddr.IPPrefix {
// 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
}
// 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 netaddr.IP) netaddr.IP {
if !ipv4.Is4() || !IsTailscaleIP(ipv4) {
return netaddr.IP{}
}
ret := Tailscale4To6Range().IP.As16()
v4 := ipv4.As4()
copy(ret[13:], v4[1:])
return netaddr.IPFrom16(ret)
}
func mustPrefix(v *netaddr.IPPrefix, prefix string) {