Add complete secondary support

Respond to notifies and allow a secondary to follow the SOA parameters

to update a zone from a primary. Also sprinkle it with logging.



Also extend monitoring to include qtype in more metrics.

middleware/file/secondary.go

@@ -2,6 +2,9 @@ package file
 
 import (
 	"log"
+	"time"
+
+	"github.com/miekg/coredns/middleware"
 
 	"github.com/miekg/dns"
 )
@@ -11,16 +14,18 @@ func (z *Zone) TransferIn() error {
 	if len(z.TransferFrom) == 0 {
 		return nil
 	}
-	t := new(dns.Transfer)
 	m := new(dns.Msg)
 	m.SetAxfr(z.name)
 
+	z1 := z.Copy()
 	var Err error
+
 Transfer:
 	for _, tr := range z.TransferFrom {
+		t := new(dns.Transfer)
 		c, err := t.In(m, tr)
 		if err != nil {
-			log.Printf("[ERROR] Failed to setup transfer %s with %s: %v", z.name, z.TransferFrom[0], err)
+			log.Printf("[ERROR] Failed to setup transfer %s with %s: %v", z.name, tr, err)
 			Err = err
 			continue Transfer
 		}
@@ -32,21 +37,127 @@ Transfer:
 			}
 			for _, rr := range env.RR {
 				if rr.Header().Rrtype == dns.TypeSOA {
-					z.SOA = rr.(*dns.SOA)
+					z1.SOA = rr.(*dns.SOA)
 					continue
 				}
 				if rr.Header().Rrtype == dns.TypeRRSIG {
 					if x, ok := rr.(*dns.RRSIG); ok && x.TypeCovered == dns.TypeSOA {
-						z.SIG = append(z.SIG, x)
+						z1.SIG = append(z1.SIG, x)
 					}
 				}
-				z.Insert(rr)
+				z1.Insert(rr)
 			}
 		}
+		Err = nil
+		break
 	}
 	if Err != nil {
 		log.Printf("[ERROR] Failed to transfer %s", z.name)
+		return nil
 	}
+
+	z.Tree = z1.Tree
+	*z.Expired = false
+	log.Printf("[INFO] Transfered: %s", z.name)
+	return nil
+}
+
+// shouldTransfer checks the primaries of zone, retrieves the SOA record, checks the current serial
+// and the remote serial and will return true if the remote one is higher than the locally configured one.
+func (z *Zone) shouldTransfer() (bool, error) {
+	c := new(dns.Client)
+	c.Net = "tcp" // do this query over TCP to minimize spoofing
+	m := new(dns.Msg)
+	m.SetQuestion(z.name, dns.TypeSOA)
+
+	var Err error
+	serial := -1
+
+	for _, tr := range z.TransferFrom {
+		Err = nil
+		ret, err := middleware.Exchange(c, m, tr)
+		if err != nil || ret.Rcode != dns.RcodeSuccess {
+			Err = err
+			continue
+		}
+		for _, a := range ret.Answer {
+			if a.Header().Rrtype == dns.TypeSOA {
+				serial = int(a.(*dns.SOA).Serial)
+			}
+		}
+	}
+	if serial == -1 {
+		return false, Err
+	}
+	return less(z.SOA.Serial, uint32(serial)), Err
+}
+
+// less return true of a is smaller than b when taking RFC 1982 serial arithmetic into account.
+func less(a, b uint32) bool {
+	// TODO(miek): implement!
+	return a < b
+}
+
+// Update updates the secondary zone according to its SOA. It will run for the life time of the server
+// and uses the SOA parameters. Every refresh it will check for a new SOA number. If that fails (for all
+// server) it wil retry every retry interval. If the zone failed to transfer before the expire, the zone
+// will be marked expired.
+func (z *Zone) Update() error {
+	// TODO(miek): if SOA changes we need to redo this with possible different timer values.
+	// TODO(miek): yeah...
+	for z.SOA == nil {
+		time.Sleep(1 * time.Second)
+	}
+
+	refresh := time.Second * time.Duration(z.SOA.Refresh)
+	retry := time.Second * time.Duration(z.SOA.Retry)
+	expire := time.Second * time.Duration(z.SOA.Expire)
+	retryActive := false
+
+	// TODO(miek): check max as well?
+	if refresh < time.Hour {
+		refresh = time.Hour
+	}
+	if retry < time.Hour {
+		retry = time.Hour
+	}
+
+	refreshTicker := time.NewTicker(refresh)
+	retryTicker := time.NewTicker(retry)
+	expireTicker := time.NewTicker(expire)
+
+	for {
+		select {
+		case <-expireTicker.C:
+			if !retryActive {
+				break
+			}
+			// TODO(miek): should actually keep track of last succesfull transfer
+			*z.Expired = true
+
+		case <-retryTicker.C:
+			if !retryActive {
+				break
+			}
+			ok, err := z.shouldTransfer()
+			if err != nil && ok {
+				log.Printf("[INFO] Refreshing zone: %s: initiating transfer", z.name)
+				z.TransferIn()
+				retryActive = false
+			}
+
+		case <-refreshTicker.C:
+			ok, err := z.shouldTransfer()
+			retryActive = err != nil
+			if err != nil && ok {
+				log.Printf("[INFO] Refreshing zone: %s: initiating transfer", z.name)
+				z.TransferIn()
+			}
+		}
+	}
+
+	refreshTicker.Stop()
+	retryTicker.Stop()
+	expireTicker.Stop()
 	return nil
-	return Err // ignore errors for now. TODO(miek)
 }