nsupdate: lots of clean up logic

such a pain every time I have to code this stuff

internal/pkg/container/nsupdate.go

@@ -1,14 +1,101 @@
 package container
 
 import (
-	"net"
+	"fmt"
+	"strings"
 	"time"
 
 	cmd "gitea.elkins.co/Networking/ccl/internal/pkg/command"
 	"github.com/miekg/dns"
 )
 
-func (c *Container) doReverse(rv string, dn string) error {
+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,
@@ -19,20 +106,6 @@ func (c *Container) doReverse(rv string, dn string) error {
 		Ptr: dn,
 	}
 
-	cli := new(dns.Client)
-	if c.TSIGName != "" {
-		cli.TsigSecret = map[string]string{c.TSIGName: c.TSIGKey}
-	}
-
-	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
 	msg = new(dns.Msg)
 	msg.SetUpdate(soa)
 	msg.Ns = append(msg.Ns, &ptr)
@@ -46,23 +119,85 @@ func (c *Container) doReverse(rv string, dn string) error {
 	return nil
 }
 
-func (c *Container) NsUpdateCommands() cmd.Set {
+func (c *Container) killDnsForward(name string, rrtype uint16) error {
-	if c.DomainName == "" || c.DnsServer == "" {
+	cli := c.makeDnsClient()
-		return cmd.Set{ID: "NSUPDATE_NOT_CONFIGURED"}
+
+	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
+	// 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.IsUnspecified() {
+		if n.IPv6.Bool && n.IPv6Address != nil && !n.IPv6Address.IsUnspecified() {
-			ad := net.ParseIP(n.IPv6Address.String())
-			if ad != nil {
 			f_6 := func() error {
 				aaaa := dns.AAAA{
 					Hdr: dns.RR_Header{
@@ -71,42 +206,23 @@ func (c *Container) NsUpdateCommands() cmd.Set {
 						Class:  dns.ClassINET,
 						Ttl:    7200,
 					},
-						AAAA: ad,
+					AAAA: n.IPv6Address,
 				}
 
-					rv, err := dns.ReverseAddr(aaaa.AAAA.String())
+				if err := c.doDnsReverse(aaaa.AAAA.String(), dn, dns.TypeAAAA); err != nil {
-					if err != nil {
 					return err
 				}
-
+				if err := c.killDnsForward(dn, dns.TypeAAAA); err != nil {
-					cli := new(dns.Client)
-					if c.TSIGName != "" {
-						cli.TsigSecret = map[string]string{c.TSIGName: c.TSIGKey}
-					}
-
-					// Update the forward record
-					msg := new(dns.Msg)
-					msg.SetUpdate(dns.Fqdn(c.DomainName))
-					msg.Ns = append(msg.Ns, &aaaa)
-
-					if c.TSIGName != "" {
-						msg.SetTsig(c.TSIGName, dns.HmacSHA256, 300, time.Now().Unix())
-					}
-					if _, _, err = cli.Exchange(msg, c.DnsServer); err != nil {
 					return err
 				}
-
+				if err := c.doDnsForward(aaaa.String()); err != nil {
-					if err = c.doReverse(rv, dn); err != nil {
 					return err
 				}
 				return nil
 			}
 			cmds = append(cmds, cmd.NewFunc("nsupate6", f_6))
 		}
-		}
+		if n.IPv4Address != nil && !n.IPv4Address.IsUnspecified() {
-		if !n.IPv4Address.IsUnspecified() {
-			ad := net.ParseIP(n.IPv4Address.String())
-			if ad != nil {
 			f_4 := func() error {
 				a := dns.A{
 					Hdr: dns.RR_Header{
@@ -115,31 +231,16 @@ func (c *Container) NsUpdateCommands() cmd.Set {
 						Class:  dns.ClassINET,
 						Ttl:    7200,
 					},
-						A: ad,
+					A: n.IPv4Address,
 				}
 
-					rv, err := dns.ReverseAddr(a.A.String())
+				if err := c.doDnsReverse(a.A.String(), dn, dns.TypeA); err != nil {
-					if err != nil {
 					return err
 				}
-
+				if err := c.killDnsForward(dn, dns.TypeA); err != nil {
-					cli := new(dns.Client)
-					if c.TSIGName != "" {
-						cli.TsigSecret = map[string]string{c.TSIGName: c.TSIGKey}
-					}
-
-					// Update the forward record
-					msg := new(dns.Msg)
-					msg.SetUpdate(dns.Fqdn(c.DomainName))
-					msg.Ns = append(msg.Ns, &a)
-					if c.TSIGName != "" {
-						msg.SetTsig(c.TSIGName, dns.HmacSHA256, 300, time.Now().Unix())
-					}
-					if _, _, err = cli.Exchange(msg, c.DnsServer); err != nil {
 					return err
 				}
-
+				if err := c.doDnsForward(a.String()); err != nil {
-					if err = c.doReverse(rv, dn); err != nil {
 					return err
 				}
 				return nil
@@ -147,6 +248,5 @@ func (c *Container) NsUpdateCommands() cmd.Set {
 			cmds = append(cmds, cmd.NewFunc("nsupate4", f_4))
 		}
 	}
-	}
 	return c.newCommandSet("NSUPDATE", cmds)
 }