implement DNS frontend

node/lux_dns.go

@@ -3,9 +3,14 @@ package node
 import (
 	"encoding/binary"
 	"fmt"
+	"lux/host"
 	"net"
+	"net/netip"
+	"strings"
 )
 
+const LUX_DNS_TTL uint32 = 60 * 5 // 5 minutes
+
 type LuxDnsServer struct {
 	node     *LuxNode
 	stopChan chan bool
@@ -30,6 +35,46 @@ type dnsEntry struct {
 	dnsClass uint16
 }
 
+// host
+// host.lux
+// host.wan.lux
+// host.re0.lux
+// service1.host.re0.lux
+type luxDomainInfo struct {
+	hostname string
+	netif    string
+	tld      string
+}
+
+func (entry *dnsEntry) ParseDomainInfo() luxDomainInfo {
+	switch len(entry.labels) {
+	case 1:
+		return luxDomainInfo{
+			hostname: entry.labels[0],
+			netif:    "wan",
+			tld:      "lux",
+		}
+	case 2:
+		return luxDomainInfo{
+			hostname: entry.labels[0],
+			netif:    "wan",
+			tld:      entry.labels[1],
+		}
+	case 3:
+		return luxDomainInfo{
+			hostname: entry.labels[0],
+			netif:    entry.labels[1],
+			tld:      entry.labels[2],
+		}
+	default:
+		return luxDomainInfo{
+			hostname: entry.labels[len(entry.labels)-3],
+			netif:    entry.labels[len(entry.labels)-2],
+			tld:      entry.labels[len(entry.labels)-1],
+		}
+	}
+}
+
 func (sv *LuxDnsServer) HandleRequest(req []byte) []byte {
 	id := NO.Uint16(req[0:2])
 	flags := NO.Uint16(req[2:4])
@@ -48,9 +93,7 @@ func (sv *LuxDnsServer) HandleRequest(req []byte) []byte {
 
 	if qr != 0 || opcode != 0 {
 		// throw not supported
-		qr = 1
-		rcode = 4
-		goto reply
+		goto not_imp
 	}
 
 	// decode questions
@@ -97,21 +140,113 @@ func (sv *LuxDnsServer) HandleRequest(req []byte) []byte {
 		offset += 2
 
 		entries[i] = dnsEntry{
+			fullName: strings.Join(labels, "."),
 			labels:   labels,
 			offset:   thisOff,
 			dnsType:  dnsType,
 			dnsClass: dnsClass,
 		}
 	}
-	fmt.Println(entries)
-	goto not_imp
+
+	// start forming response. first, we just gonna put questions
+	// from request into response
+	fmt.Println(offset)
+	data = req[12:offset]
+
+	// answer questions
+	for _, entry := range entries {
+		info := entry.ParseDomainInfo()
+		if info.tld != "lux" {
+			goto refused
+		}
+
+		// find luxHost
+		luxHost, ok := sv.node.GetHostByName(info.hostname)
+		if !ok {
+			goto not_found
+		}
+
+		// get IP by netif
+		state := &luxHost.State
+
+		var addr netip.Addr
+		switch info.netif {
+		case "wan":
+			wan, ok := state.Options[host.LuxOptionTypeWAN]
+			if !ok {
+				// no WAN info
+				goto not_found
+			}
+
+			addr = wan.(*host.LuxOptionWAN).Addr4
+		default:
+			// look for netif
+			opt, ok := state.Options[host.LuxOptionTypeNetIf]
+			if !ok {
+				goto not_found
+			}
+
+			netif, ok := opt.(*host.LuxOptionNetIf).Interfaces[info.netif]
+			if !ok {
+				goto not_found
+			}
+
+			ipFound := false
+			for _, netAddr := range netif.Addrs {
+				if netAddr.Type == host.LuxNetAddrType4 {
+					addr = netAddr.Addr
+					ipFound = true
+				}
+			}
+			if !ipFound {
+				goto not_found
+			}
+		}
+
+		// write IP to response
+		answer := make([]byte, 12)
+		NO.PutUint16(answer[0:2], uint16(entry.offset)|0xC000) // name
+		NO.PutUint16(answer[2:4], entry.dnsType)               // type
+		NO.PutUint16(answer[4:6], entry.dnsClass)              // class
+		NO.PutUint32(answer[6:10], LUX_DNS_TTL)                // DNS TTL
+
+		if addr.Is6() {
+			NO.PutUint16(answer[10:12], 16) // Data Length - IPv6
+
+			octets := addr.As16()
+			answer = append(answer, octets[:]...)
+		} else {
+			NO.PutUint16(answer[10:12], 4) // Data Length - IPv4
+
+			octets := addr.As4()
+			answer = append(answer, octets[:]...)
+		}
+
+		data = append(data, answer...)
+		ancount++
+	}
+
+	rcode = 0
+	nscount = 0
+	arcount = 0
+
+	flags |= (1 << 10) // Authoritative Answer
+	goto reply
 
 decode_error:
 	rcode = 2
 	goto reply
 
+not_found:
+	rcode = 3
+	goto reply
+
 not_imp:
 	rcode = 4
+	goto reply
+
+refused:
+	rcode = 5
 
 reply:
 	qr = 1

node/lux_node.go

@@ -101,8 +101,8 @@ func (node *LuxNode) GetStateLock() *sync.RWMutex {
 }
 
 func (node *LuxNode) GetHostByName(name string) (LuxHostState, bool) {
-	node.stateLock.RLock()
-	defer node.stateLock.RUnlock()
+	// node.stateLock.RLock()
+	// defer node.stateLock.RUnlock()
 
 	for _, host := range node.state.hosts {
 		if host.State.Hostname == name {