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This commit is contained in:
Juan Font Alonso 2021-10-10 00:40:25 +02:00
parent 32c3f09eb4
commit 6884798404
1 changed files with 11 additions and 0 deletions
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11
dns.go
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@ -8,6 +8,9 @@ import (
"tailscale.com/util/dnsname" "tailscale.com/util/dnsname"
) )
// generateMagicDNSRootDomains generates a list of DNS entries to be included in the
// routing for DNS in the MapResponse struct. This list of DNS instructs the OS
// on what domains the Tailscale embedded DNS server should be used for.
func generateMagicDNSRootDomains(ipPrefix netaddr.IPPrefix, baseDomain string) (*[]dnsname.FQDN, error) { func generateMagicDNSRootDomains(ipPrefix netaddr.IPPrefix, baseDomain string) (*[]dnsname.FQDN, error) {
base, err := dnsname.ToFQDN(baseDomain) base, err := dnsname.ToFQDN(baseDomain)
if err != nil { if err != nil {
@ -19,14 +22,22 @@ func generateMagicDNSRootDomains(ipPrefix netaddr.IPPrefix, baseDomain string) (
ipv6base := dnsname.FQDN("0.e.1.a.c.5.1.1.a.7.d.f.ip6.arpa.") ipv6base := dnsname.FQDN("0.e.1.a.c.5.1.1.a.7.d.f.ip6.arpa.")
fqdns := []dnsname.FQDN{base, ipv6base} fqdns := []dnsname.FQDN{base, ipv6base}
// Conversion to the std lib net.IPnet, a bit easier to operate
netRange := ipPrefix.IPNet() netRange := ipPrefix.IPNet()
maskBits, _ := netRange.Mask.Size() maskBits, _ := netRange.Mask.Size()
// lastByte is the last IP byte covered by the mask
lastByte := maskBits / 8 lastByte := maskBits / 8
// unmaskedBits is the number of bits not under the mask in the byte lastByte
unmaskedBits := 8 - maskBits%8 unmaskedBits := 8 - maskBits%8
// min is the value in the lastByte byte of the IP
// max is basically 2^unmaskedBits - i.e., the value when all the unmaskedBits are set to 1
min := uint(netRange.IP[lastByte]) min := uint(netRange.IP[lastByte])
max := uint((min + 1<<uint(unmaskedBits)) - 1) max := uint((min + 1<<uint(unmaskedBits)) - 1)
// here we generate the base domain (e.g., 100.in-addr.arpa., 16.172.in-addr.arpa., etc.)
rdnsSlice := []string{} rdnsSlice := []string{}
for i := lastByte - 1; i >= 0; i-- { for i := lastByte - 1; i >= 0; i-- {
rdnsSlice = append(rdnsSlice, fmt.Sprintf("%d", netRange.IP[i])) rdnsSlice = append(rdnsSlice, fmt.Sprintf("%d", netRange.IP[i]))