From 68847984047b2b4bddb53e0eefc70cb878670f25 Mon Sep 17 00:00:00 2001 From: Juan Font Alonso Date: Sun, 10 Oct 2021 00:40:25 +0200 Subject: [PATCH] Added some comments --- dns.go | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/dns.go b/dns.go index d8f587f5..db09337d 100644 --- a/dns.go +++ b/dns.go @@ -8,6 +8,9 @@ import ( "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) { base, err := dnsname.ToFQDN(baseDomain) 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.") fqdns := []dnsname.FQDN{base, ipv6base} + // Conversion to the std lib net.IPnet, a bit easier to operate netRange := ipPrefix.IPNet() maskBits, _ := netRange.Mask.Size() + // lastByte is the last IP byte covered by the mask lastByte := maskBits / 8 + + // unmaskedBits is the number of bits not under the mask in the byte lastByte 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]) max := uint((min + 1<= 0; i-- { rdnsSlice = append(rdnsSlice, fmt.Sprintf("%d", netRange.IP[i]))