fancy-dns/internal/localzone/render.go

package localzone

import (
	"fmt"
	"strings"

	"git.k8s-git-k6n.net/mats/fancy-dns/internal/zonefile"
)

// RenderZone renders a complete zone from declared records, for sources that
// own a zone outright (a Kubernetes DNSZone) rather than editing a file in
// place. It runs the same checks the console writer does: every record goes
// through newRecord, a delegation may not shadow data, and the rendering is
// re-parsed and compared with the records before it is returned, so a renderer
// bug surfaces as an error here and not as a zone that silently stopped
// answering.
//
// serial is the SOA serial; 0 means the writer's default. A declarative source
// should pass something that changes exactly when the spec does, so two
// replicas rendering the same object produce the same bytes.
func RenderZone(origin string, def ZoneDefaults, recs []Record, serial uint32) (string, error) {
	origin, err := NormalizeOrigin(origin)
	if err != nil {
		return "", fmt.Errorf("zone name: %w", err)
	}
	f, err := newFileState(origin, def)
	if err != nil {
		return "", err
	}
	for _, in := range recs {
		rec, err := newRecord(origin, in.Name, in.Type, ttlOr(in.TTL, f.ttl), in.Value)
		if err != nil {
			return "", err
		}
		for _, have := range f.recs {
			if have.Key() == rec.Key() && have.Value == rec.Value {
				return "", fmt.Errorf("%s %s is declared twice", rec.Name, rec.Type)
			}
		}
		f.recs = append(f.recs, rec)
	}
	if err := f.finish(); err != nil {
		return "", err
	}
	if serial != 0 {
		f.soa.Serial = serial
	}
	text := f.render()
	check, err := parseFileState(origin, text)
	if err != nil {
		return "", fmt.Errorf("the zone file for %s did not render correctly: %w", origin, err)
	}
	if err := sameRecords(check.recs, f.recs); err != nil {
		return "", fmt.Errorf("the zone file for %s did not render correctly: %w", origin, err)
	}
	return strings.Replace(text, FileHeader, ZoneSourceHeader, 1), nil
}

// ZoneSourceHeader tops a rendered zone that an external object owns.
const ZoneSourceHeader = `; fancy-dns zone rendered from a Kubernetes DNSZone object.
;
; Regenerated whenever the object changes; edit the DNSZone, not this file.
`

// CanonicalRecord returns a record in the form the zone store holds it: the
// owner fully qualified, the type uppercased, the RDATA as the master-file
// parser reads it. An editor compares records in this form, so "www" and
// "www.example.com." are the same record.
func CanonicalRecord(origin string, in Record) (Record, error) {
	origin, err := NormalizeOrigin(origin)
	if err != nil {
		return Record{}, fmt.Errorf("zone name: %w", err)
	}
	rec, err := newRecord(origin, in.Name, in.Type, ttlOr(in.TTL, DefaultZoneTTL), in.Value)
	if err != nil {
		return Record{}, err
	}
	rec.TTL = in.TTL // 0 still means "the zone's default"
	return rec, nil
}

// ZoneFile is a master file read back into the form a DNSZone holds it in.
type ZoneFile struct {
	// TTL is the file's $TTL, or the default when it has none.
	TTL uint32
	// Soa is the SOA rdata ("ns mbox serial refresh retry expire minimum"), or
	// "" when the file has none.
	Soa     string
	Records []Record
}

// ParseZoneFile reads an RFC 1035 master file for the zone origin. Records come
// back canonical (absolute owner, uppercase type, rdata as the parser prints
// it) and without the SOA, which is returned separately. It is the reading half
// of a migration from master files to DNSZone objects.
func ParseZoneFile(origin, text string) (ZoneFile, error) {
	origin, err := NormalizeOrigin(origin)
	if err != nil {
		return ZoneFile{}, fmt.Errorf("zone name: %w", err)
	}
	z, err := zonefile.Parse(strings.NewReader(text), zonefile.Options{Origin: origin, File: origin + "zone"})
	if err != nil {
		return ZoneFile{}, err
	}
	f := fileStateFromZone(z, origin)
	out := ZoneFile{TTL: f.ttl, Records: f.recs}
	if f.soa != nil {
		out.Soa = fmt.Sprintf("%s %s %d %d %d %d %d", f.soa.Ns, f.soa.Mbox,
			f.soa.Serial, f.soa.Refresh, f.soa.Retry, f.soa.Expire, f.soa.Minttl)
	}
	return out, nil
}