From ab5d8dec9ecc76b13541bee947f172417015b64e Mon Sep 17 00:00:00 2001
From: mykola2312 <49044616+mykola2312@users.noreply.github.com>
Date: Tue, 28 Jan 2025 04:27:19 +0200
Subject: [PATCH] simple DNS response works

---
 main.go          | 10 ++++++++++
 node/lux_dns.go  | 43 +++++++++++++++++++++++++++++++++++++++----
 node/lux_node.go | 15 +++++++++++++++
 3 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/main.go b/main.go
index 71c3da7..91c7827 100644
--- a/main.go
+++ b/main.go
@@ -54,6 +54,8 @@ type NodeConfig struct {
 
 	RPCEndpoints []string `xml:"rpc"`
 
+	DNS []string `xml:"dns"`
+
 	Log LogConfig `xml:"log"`
 }
 
@@ -276,6 +278,14 @@ func nodeMain() {
 		}
 	}
 
+	// add dns server frontends
+	for _, dnsListen := range config.DNS {
+		if err := node.AddDnsFrontend(dnsListen); err != nil {
+			log.Criticalf("failed to spawn dns %s: %v\n", dnsListen, err)
+			os.Exit(1)
+		}
+	}
+
 	// start node
 	node.Start()
 
diff --git a/node/lux_dns.go b/node/lux_dns.go
index bcc286d..bee65aa 100644
--- a/node/lux_dns.go
+++ b/node/lux_dns.go
@@ -1,21 +1,56 @@
 package node
 
-import "net"
+import (
+	"encoding/binary"
+	"net"
+)
 
 type LuxDnsServer struct {
 	node     *LuxNode
 	stopChan chan bool
 }
 
-func NewLuxDnsServer(node *LuxNode) LuxDnsServer {
-	return LuxDnsServer{
+func NewLuxDnsServer(node *LuxNode) *LuxDnsServer {
+	return &LuxDnsServer{
 		node:     node,
 		stopChan: make(chan bool),
 	}
 }
 
+var NO = binary.BigEndian
+
 func (sv *LuxDnsServer) HandleRequest(req []byte) []byte {
-	return nil
+	id := NO.Uint16(req[0:2])
+	flags := NO.Uint16(req[2:4])
+	qdcount := NO.Uint16(req[4:6])
+	ancount := NO.Uint16(req[6:8])
+	nscount := NO.Uint16(req[8:10])
+	arcount := NO.Uint16(req[10:12])
+	data := req[12:]
+
+	qr := flags >> 15
+	opcode := (flags >> 11) & 0b1111
+	var rcode uint16
+
+	if qr != 0 || opcode != 0 {
+		// throw not supported
+		goto reply
+	}
+
+	qr = 1
+	rcode = 4
+reply:
+	flags |= (qr << 15) | rcode
+
+	hdr := make([]byte, 12)
+	NO.PutUint16(hdr[0:2], id)
+	NO.PutUint16(hdr[2:4], flags)
+	NO.PutUint16(hdr[4:6], qdcount)
+	NO.PutUint16(hdr[6:8], ancount)
+	NO.PutUint16(hdr[8:10], nscount)
+	NO.PutUint16(hdr[10:12], arcount)
+
+	return append(hdr, data...)
 }
 
 func (sv *LuxDnsServer) CreateFrontend(udpListen string) error {
diff --git a/node/lux_node.go b/node/lux_node.go
index 8a60c0a..2361d65 100644
--- a/node/lux_node.go
+++ b/node/lux_node.go
@@ -24,6 +24,8 @@ type LuxNode struct {
 	stateLock sync.RWMutex
 
 	genlist net.LuxNonceList
+
+	dns *LuxDnsServer
 }
 
 func NewLuxNode(nodeKey crypto.LuxKey, ks crypto.LuxKeyStore) LuxNode {
@@ -34,6 +36,7 @@ func NewLuxNode(nodeKey crypto.LuxKey, ks crypto.LuxKeyStore) LuxNode {
 		neighbors: make(map[proto.LuxID]*ipnet.UDPAddr),
 		state:     NewLuxNodeState(),
 		genlist:   net.NewLuxNonceList(),
+		dns:       nil,
 	}
 }
 
@@ -81,6 +84,14 @@ func (node *LuxNode) AddNeighbor(id proto.LuxID, udpAddr string) error {
 	return nil
 }
 
+func (node *LuxNode) AddDnsFrontend(udpListen string) error {
+	if node.dns == nil {
+		node.dns = NewLuxDnsServer(node)
+	}
+
+	return node.dns.CreateFrontend(udpListen)
+}
+
 func (node *LuxNode) GetState() *LuxNodeState {
 	return &node.state
 }
@@ -228,6 +239,10 @@ func (node *LuxNode) Start() {
 }
 
 func (node *LuxNode) Stop() {
+	if node.dns != nil {
+		node.dns.Stop()
+	}
+
 	node.running = false
 	node.router.Stop()
 }