implement IPv6 in DNS

node/lux_dns.go

@@ -9,7 +9,7 @@ import (
 	"strings"
 )
 
-const LUX_DNS_TTL uint32 = 60 * 5 // 5 minutes
+const LUX_DNS_TTL uint32 = 60 * 1 // 1 minute
 
 type LuxDnsServer struct {
 	node     *LuxNode
@@ -75,6 +75,9 @@ func (entry *dnsEntry) ParseDomainInfo() luxDomainInfo {
 	}
 }
 
+const dnsTypeA = 1
+const dnsTypeAAAA = 28
+
 func (sv *LuxDnsServer) HandleRequest(req []byte) []byte {
 	id := NO.Uint16(req[0:2])
 	flags := NO.Uint16(req[2:4])
@@ -155,6 +158,10 @@ func (sv *LuxDnsServer) HandleRequest(req []byte) []byte {
 
 	// answer questions
 	for _, entry := range entries {
+		if entry.dnsType != dnsTypeA && entry.dnsType != dnsTypeAAAA {
+			continue // only A and AAAA are supported
+		}
+
 		info := entry.ParseDomainInfo()
 		if info.tld != "lux" {
 			goto refused
@@ -178,7 +185,17 @@ func (sv *LuxDnsServer) HandleRequest(req []byte) []byte {
 				goto not_found
 			}
 
-			addr = wan.(*host.LuxOptionWAN).Addr4
+			if entry.dnsType == dnsTypeA {
+				// IPv4
+				addr = wan.(*host.LuxOptionWAN).Addr4
+			} else {
+				// IPv6
+				addr = wan.(*host.LuxOptionWAN).Addr6
+			}
+
+			if addr.IsUnspecified() {
+				goto not_found
+			}
 		default:
 			// look for netif
 			opt, ok := state.Options[host.LuxOptionTypeNetIf]
@@ -193,9 +210,25 @@ func (sv *LuxDnsServer) HandleRequest(req []byte) []byte {
 
 			ipFound := false
 			for _, netAddr := range netif.Addrs {
-				if netAddr.Type == host.LuxNetAddrType4 {
-					addr = netAddr.Addr
-					ipFound = true
+				if entry.dnsType == dnsTypeA {
+					if netAddr.Type == host.LuxNetAddrType4 {
+						addr = netAddr.Addr
+						ipFound = true
+						break
+					}
+				} else {
+					// look either for IPv6 global unicast or local unicast.
+					// but we prefer global over local unicast
+					if netAddr.Type == host.LuxNetAddrType6GUA {
+						addr = netAddr.Addr
+						ipFound = true
+						break
+					} else if netAddr.Type == host.LuxNetAddrType6ULA {
+						addr = netAddr.Addr
+						ipFound = true
+						// we dont break here since next addr may be global unicast,
+						// which we prefer over ula
+					}
 				}
 			}
 			if !ipFound {