lib/dns: add init method to RDataSOA

The ini method initialize the SOA record by setting fields to its default
value if its empty.

The default value for RName is "root", for Serial is current epoch,
for Refresh is 1 day, for Retry is 1 hour, and for Minimum is 1 hour.

While at it, update the comments to be more understandable and represent
the type or fields.

1 files changed, 49 insertions, 40 deletions

diff --git a/lib/dns/rdata_soa.go b/lib/dns/rdata_soa.go
index b4fda947..a511de1e 100644
--- a/lib/dns/rdata_soa.go
+++ b/lib/dns/rdata_soa.go
@@ -5,67 +5,76 @@
 package dns
 
 import (
-	"fmt"
 	"strings"
+	"time"
+)
+
+const (
+	defaultRName      string = "root"
+	defaultRefresh    int32  = 1 * 24 * 60 * 60 // 1 Day.
+	defaultRetry      int32  = 1 * 60 * 60      // 1 Hour.
+	defaultMinimumTTL uint32 = 1 * 60 * 60      // 1 Hour.
 )
 
 //
-// RDataSOA marks the Start Of a zone of Authority RDATA format in resource
-// record.
+// RDataSOA contains the authority of zone.
 //
 // All times are in units of seconds.
 //
-// Most of these fields are pertinent only for name server maintenance
-// operations.  However, MINIMUM is used in all query operations that
-// retrieve RRs from a zone.  Whenever a RR is sent in a response to a
-// query, the TTL field is set to the maximum of the TTL field from the RR
-// and the MINIMUM field in the appropriate SOA.  Thus MINIMUM is a lower
-// bound on the TTL field for all RRs in a zone.  Note that this use of
-// MINIMUM should occur when the RRs are copied into the response and not
-// when the zone is loaded from a zone file or via a zone transfer.  The
-// reason for this provison is to allow future dynamic update facilities to
-// change the SOA RR with known semantics.
-//
 type RDataSOA struct {
-	// The <domain-name> of the name server that was the original or
-	// primary source of data for this zone.
+	// The primary name server for the zone.
 	MName string
 
-	// A <domain-name> which specifies the mailbox of the person
-	// responsible for this zone.
+	// The mailbox of the person responsible for the name server.
+	// For example, "root@localhost", but with '@' is replaced with dot
+	// '.', its become "root.localhost".
+	// If its empty, default to "root".
 	RName string
 
-	// The unsigned 32 bit version number of the original copy of the
-	// zone.  Zone transfers preserve this value.  This value wraps and
-	// should be compared using sequence space arithmetic.
+	// The version number of the original copy of the zone.
+	// If its empty, default to current epoch.
 	Serial uint32
 
-	// A 32 bit time interval before the zone should be refreshed.
+	// A time interval before the zone should be refreshed.
+	// If its empty, default to 1 days.
 	Refresh int32
 
-	// A 32 bit time interval that should elapse before a failed refresh
-	// should be retried.
+	// A time interval that should elapse before a failed refresh should
+	// be retried.
+	// If its empty, default to 1 hour.
 	Retry int32
 
-	// A 32 bit time value that specifies the upper limit on the time
-	// interval that can elapse before the zone is no longer
-	// authoritative.
+	// A time value that specifies the upper limit on the time interval
+	// that can elapse before the zone is no longer authoritative.
 	Expire int32
 
-	// The unsigned 32 bit minimum TTL field that should be exported with
-	// any RR from this zone.
+	// The minimum TTL field that should be exported with any RR from this
+	// zone.
+	// If its empty, default to 1 hour.
 	Minimum uint32
 }
 
-//
-// String return readable representation of SOA record.
-//
-func (soa *RDataSOA) String() string {
-	var b strings.Builder
-
-	fmt.Fprintf(&b, "{MName:%s RName:%s Serial:%d Refresh:%d Retry:%d Expire:%d Minimum:%d}",
-		soa.MName, soa.RName, soa.Serial, soa.Refresh, soa.Retry,
-		soa.Expire, soa.Minimum)
-
-	return b.String()
+// init initialize the SOA record by setting fields to its default value if
+// its empty.
+func (soa *RDataSOA) init() {
+	if len(soa.MName) > 0 {
+		soa.MName = strings.ToLower(soa.MName)
+	}
+	if len(soa.RName) > 0 {
+		soa.RName = strings.ToLower(soa.RName)
+	} else {
+		soa.RName = defaultRName
+	}
+	if soa.Serial == 0 {
+		soa.Serial = uint32(time.Now().Unix())
+	}
+	if soa.Refresh == 0 {
+		soa.Refresh = defaultRefresh
+	}
+	if soa.Retry == 0 {
+		soa.Retry = defaultRetry
+	}
+	if soa.Minimum == 0 {
+		soa.Minimum = defaultMinimumTTL
+	}
 }