Feature/dns-server (#537)

Adding DNS server for client

Updated the API with new fields

Added custom zone object for peer's DNS resolution

dns/dns.go

@@ -2,5 +2,55 @@
 // to parse and normalize dns records and configuration
 package dns
 
-// DefaultDNSPort well-known port number
-const DefaultDNSPort = 53
+import (
+	"fmt"
+	"github.com/miekg/dns"
+)
+
+const (
+	// DefaultDNSPort well-known port number
+	DefaultDNSPort = 53
+	// RootZone is a string representation of the root zone
+	RootZone = "."
+	// DefaultClass is the class supported by the system
+	DefaultClass = "IN"
+)
+
+// Update represents a dns update that is exchanged between management and peers
+type Update struct {
+	// ServiceEnable indicates if the service should be enabled
+	ServiceEnable bool
+	// NameServerGroups contains a list of nameserver group
+	NameServerGroups []NameServerGroup
+	// CustomZones contains a list of custom zone
+	CustomZones []CustomZone
+}
+
+// CustomZone represents a custom zone to be resolved by the dns server
+type CustomZone struct {
+	// Domain is the zone's domain
+	Domain string
+	// Records custom zone records
+	Records []SimpleRecord
+}
+
+// SimpleRecord provides a simple DNS record specification for CNAME, A and AAAA records
+type SimpleRecord struct {
+	// Name domain name
+	Name string
+	// Type of record, 1 for A, 5 for CNAME, 28 for AAAA. see https://pkg.go.dev/github.com/miekg/dns@v1.1.41#pkg-constants
+	Type int
+	// Class dns class, currently use the DefaultClass for all records
+	Class string
+	// TTL time-to-live for the record
+	TTL int
+	// RData is the actual value resolved in a dns query
+	RData string
+}
+
+// String returns a string of the simple record formatted as:
+// <Name> <TTL> <Class> <Type> <RDATA>
+func (s SimpleRecord) String() string {
+	fqdn := dns.Fqdn(s.Name)
+	return fmt.Sprintf("%s %d %s %s %s", fqdn, s.TTL, s.Class, dns.Type(s.Type).String(), s.RData)
+}