ccl/internal/pkg/container/nsupdate.go

package container

import (
	"fmt"
	"strings"
	"time"

	cmd "gitea.elkins.co/Networking/ccl/internal/pkg/command"
	"github.com/miekg/dns"
)

func (c *Container) makeDnsClient() *dns.Client {
	cli := new(dns.Client)
	if c.TSIGName != "" {
		cli.TsigSecret = map[string]string{c.TSIGName: c.TSIGKey}
	}
	return cli
}

func (c *Container) killDnsReverse(ip string) error {
	rv, err := dns.ReverseAddr(ip)
	if err != nil {
		return err
	}
	cli := c.makeDnsClient()

	// Determine SOA of old reverse zone
	msg := new(dns.Msg)
	msg.SetQuestion(rv, dns.TypeSOA)
	resp, _, err := cli.Exchange(msg, c.DnsServer)
	if err != nil {
		return err
	}
	soa := resp.Ns[0].Header().Name

	// Remove the old PTR
	ptr := dns.ANY{
		Hdr: dns.RR_Header{
			Name:   rv,
			Rrtype: dns.TypePTR,
		},
	}
	msg = new(dns.Msg)
	msg.SetUpdate(soa)
	msg.RemoveName([]dns.RR{&ptr})
	if c.TSIGName != "" {
		msg.SetTsig(c.TSIGName, dns.HmacSHA256, 300, time.Now().Unix())
	}
	resp, _, err = cli.Exchange(msg, c.DnsServer)
	if err != nil {
		return err
	}
	return nil
}

// This is the same code for ipv4 or ipv6 so factor it out
func (c *Container) doDnsReverse(ip string, dn string, rrtype uint16) error {
	rv, err := dns.ReverseAddr(ip)
	if err != nil {
		return err
	}

	cli := c.makeDnsClient()

	// Delete any existing PTR
	// Strategy:
	//   1. find existing RR's of our given type
	//   2. for each one, kill any reverse pointers to that address
	msg := new(dns.Msg)
	msg.SetQuestion(dn, rrtype)
	resp, _, err := cli.Exchange(msg, c.DnsServer)
	if err != nil {
		return fmt.Errorf("error looking up existing RRs for %s type %d: %s", dn, rrtype, err)
	}
	for i := range resp.Answer {
		var ip string
		if rrtype == dns.TypeA {
			x := (resp.Answer[i]).(*dns.A)
			ip = x.A.String()
		} else {
			x := (resp.Answer[i]).(*dns.AAAA)
			ip = x.AAAA.String()
		}
		if err := c.killDnsReverse(ip); err != nil {
			return err
		}
	}

	// Determine SOA of reverse zone
	msg = new(dns.Msg)
	msg.SetQuestion(rv, dns.TypeSOA)
	resp, _, err = cli.Exchange(msg, c.DnsServer)
	if err != nil {
		return err
	}
	soa := resp.Ns[0].Header().Name

	// Update the reverse record
	ptr := dns.PTR{
		Hdr: dns.RR_Header{
			Name:   rv,
			Rrtype: dns.TypePTR,
			Class:  dns.ClassINET,
			Ttl:    7200,
		},
		Ptr: dn,
	}

	msg = new(dns.Msg)
	msg.SetUpdate(soa)
	msg.Ns = append(msg.Ns, &ptr)
	if c.TSIGName != "" {
		msg.SetTsig(c.TSIGName, dns.HmacSHA256, 300, time.Now().Unix())
	}
	_, _, err = cli.Exchange(msg, c.DnsServer)
	if err != nil {
		return err
	}
	return nil
}

func (c *Container) killDnsForward(name string, rrtype uint16) error {
	cli := c.makeDnsClient()

	msg := new(dns.Msg)
	msg.SetQuestion(name, rrtype)
	resp, _, err := cli.Exchange(msg, c.DnsServer)
	if err != nil {
		return err
	}

	dn := dns.Fqdn(c.DomainName)
	if !strings.HasSuffix(dn, ".") {
		dn = dn + "."
	}

	if len(resp.Answer) > 0 {
		msg := new(dns.Msg)
		msg.SetUpdate(dn)
		msg.RemoveRRset(resp.Answer)
		if _, _, err := cli.Exchange(msg, c.DnsServer); err != nil {
			return err
		}
	}

	return nil
}

func (c *Container) doDnsForward(rr string) error {
	rr_parsed, err := dns.NewRR(rr)
	if err != nil {
		return err
	}

	cli := c.makeDnsClient()
	dn := dns.Fqdn(c.DomainName)
	if !strings.HasSuffix(dn, ".") {
		dn = dn + "."
	}

	// Update the forward record
	msg := new(dns.Msg)
	msg.SetUpdate(dn)
	msg.Ns = append(msg.Ns, rr_parsed)
	if c.TSIGName != "" {
		msg.SetTsig(c.TSIGName, dns.HmacSHA256, 300, time.Now().Unix())
	}
	if _, _, err = cli.Exchange(msg, c.DnsServer); err != nil {
		return err
	}
	return nil
}

func (c *Container) NsUpdateCommands() cmd.Set {
	// check that a server is configured
	if c.DomainName == "" || c.DnsServer == "" {
		return cmd.Set{ID: "NSUPDATE", Commands: []cmd.Command{
			cmd.NewFunc("NSUPDATE_NOT_CONFIGURED", func() error {
				return fmt.Errorf("nsupdate command requires `domain_name` and `dns_server` to be configured")
			}),
		}}
	}

	// determine hostname
	hostname := c.Hostname
	if c.Hostname == "" {
		hostname = c.Name
	}
	dn := dns.Fqdn(hostname + "." + c.DomainName)
	if !strings.HasSuffix(dn, ".") {
		dn = dn + "."
	}

	// prepare update commands
	cmds := []cmd.Command{}

	// TODO: also iterate over c.IPv6Addresses, if it ever works
	for i := range c.Networks {
		n := &c.Networks[i]
		if n.IPv6.Bool && n.IPv6Address != nil && !n.IPv6Address.IsUnspecified() {
			f_6 := func() error {
				aaaa := dns.AAAA{
					Hdr: dns.RR_Header{
						Name:   dn,
						Rrtype: dns.TypeAAAA,
						Class:  dns.ClassINET,
						Ttl:    7200,
					},
					AAAA: n.IPv6Address,
				}

				if err := c.doDnsReverse(aaaa.AAAA.String(), dn, dns.TypeAAAA); err != nil {
					return err
				}
				if err := c.killDnsForward(dn, dns.TypeAAAA); err != nil {
					return err
				}
				if err := c.doDnsForward(aaaa.String()); err != nil {
					return err
				}
				return nil
			}
			cmds = append(cmds, cmd.NewFunc("nsupate6", f_6))
		}
		if n.IPv4Address != nil && !n.IPv4Address.IsUnspecified() {
			f_4 := func() error {
				a := dns.A{
					Hdr: dns.RR_Header{
						Name:   dn,
						Rrtype: dns.TypeA,
						Class:  dns.ClassINET,
						Ttl:    7200,
					},
					A: n.IPv4Address,
				}

				if err := c.doDnsReverse(a.A.String(), dn, dns.TypeA); err != nil {
					return err
				}
				if err := c.killDnsForward(dn, dns.TypeA); err != nil {
					return err
				}
				if err := c.doDnsForward(a.String()); err != nil {
					return err
				}
				return nil
			}
			cmds = append(cmds, cmd.NewFunc("nsupate4", f_4))
		}
	}
	return c.newCommandSet("NSUPDATE", cmds)
}