V2 Netbird integration - UDP MIMO/SIMO, ICMPv6, DHCPv6 implementations (#106)

* begin adding udp.MuxHandler * add udp MuxHandlerSIMO/MIMO * add tcp rx shutdown * icmpv6 client * icmpv6 Client shared NDP/Echo preparation * icmpv6 client ndp/echo split * icmpv6 client ndp/echo split done * icmpv6 adjustments * add dhcpv6 stubs * dhcpv4 preliminary revision * add dns.NextLabel * dns label name tweaks * dns begin work on TCP client * add dnstcp package * apply gofmt changes * add udp mux tests * clean up, remove StackBig for now * remove dnstcp so as to merged confident parts and we continue dnstcp work elsewhere
2026-09-03 21:39:04 +00:00 · 2026-05-10 12:16:30 -03:00
parent bdbd38ab44
commit 7d5830d7ab
22 changed files with 2785 additions and 75 deletions
@@ -15,7 +15,7 @@ type Client struct {
 	lport           uint16
 	msg             Message
 	respFlags       HeaderFlags
-	state           clientState
+	state           StateClientQuery
 	enableRecursion bool
 }

@@ -36,7 +36,7 @@ func (c *Client) StartResolve(localPort, txid uint16, cfg ResolveConfig) error {
 	if nd > math.MaxUint16 {
 		return lneto.ErrInvalidConfig
 	}
-	c.reset(localPort, txid, dnsSendQuery, cfg.EnableRecursion)
+	c.reset(localPort, txid, CQueryPending, cfg.EnableRecursion)
 	c.msg.LimitResourceDecoding(uint16(nd), uint16(nd), 0, 0)
 	c.msg.AddQuestions(cfg.Questions)
 	c.msg.AddAdditionals(cfg.Additional)
@@ -46,7 +46,7 @@ func (c *Client) StartResolve(localPort, txid uint16, cfg ResolveConfig) error {
 func (c *Client) Encapsulate(carrierData []byte, offsetToIP, offsetToFrame int) (int, error) {
 	if c.isClosed() {
 		return 0, net.ErrClosed
-	} else if c.state != dnsSendQuery {
+	} else if c.state != CQueryPending {
 		return 0, nil
 	}

@@ -64,7 +64,7 @@ func (c *Client) Encapsulate(carrierData []byte, offsetToIP, offsetToFrame int)
 		internal.LogAttrs(nil, slog.LevelError, "dns:unexpected-write", slog.Int("got", len(data)), slog.Int("want", int(msglen)))
 		return 0, lneto.ErrBug
 	}
-	c.state = dnsAwaitResponse
+	c.state = CQueryOutstanding
 	// Unset don't frag since DNS requests go through LOTS of nodes.
 	// if frameOffset >= 28 {
 	// 	version := carrierData[0] >> 4
@@ -78,7 +78,7 @@ func (c *Client) Encapsulate(carrierData []byte, offsetToIP, offsetToFrame int)
 func (c *Client) Demux(carrierData []byte, frameOffset int) error {
 	if c.isClosed() {
 		return net.ErrClosed
-	} else if c.state != dnsAwaitResponse {
+	} else if c.state != CQueryOutstanding {
 		return nil
 	}
 	frame := carrierData[frameOffset:]
@@ -91,7 +91,7 @@ func (c *Client) Demux(carrierData []byte, frameOffset int) error {
 		return nil // Not meant for our client.
 	}
 	c.respFlags = flags
-	c.state = dnsDone
+	c.state = CQueryDone
 	msg := &c.msg
 	_, incompleteButOK, err := msg.Decode(frame)
 	if err != nil && !incompleteButOK {
@@ -101,7 +101,7 @@ func (c *Client) Demux(carrierData []byte, frameOffset int) error {
 }

 func (c *Client) isClosed() bool {
-	return c.state == dnsClosed || c.state == dnsAborted
+	return c.state == CQueryIdle || c.state == CQueryAborted
 }

 func (c *Client) MessageCopyTo(dst *Message) (done bool, err error) {
@@ -117,17 +117,17 @@ func (c *Client) MessageCopyTo(dst *Message) (done bool, err error) {
 }

 func (c *Client) Answers() []Resource {
-	if c.state != dnsDone {
+	if c.state != CQueryDone {
 		return nil
 	}
 	return c.msg.Answers
 }

 func (c *Client) Abort() {
-	c.reset(0, 0, 0, false)
+	c.reset(0, 0, CQueryAborted, false)
 }

-func (c *Client) reset(lport, txid uint16, state clientState, enableRecursion bool) {
+func (c *Client) reset(lport, txid uint16, state StateClientQuery, enableRecursion bool) {
 	*c = Client{
 		connID:          c.connID + 1,
 		lport:           lport,
@@ -138,13 +138,3 @@ func (c *Client) reset(lport, txid uint16, state clientState, enableRecursion bo
 	}
 	c.msg.Reset()
 }
-
-type clientState uint8
-
-const (
-	dnsClosed clientState = iota
-	dnsSendQuery
-	dnsAwaitResponse
-	dnsDone
-	dnsAborted
-)
@@ -238,6 +238,17 @@ const (
 	RCodeRefused RCode = 5 // refused
 )

+// StateClientQuery is the lifecycle state of a single DNS query.
+type StateClientQuery uint8
+
+const (
+	CQueryIdle        StateClientQuery = iota // no active query (zero value)
+	CQueryPending                             // query built, not yet transmitted
+	CQueryOutstanding                         // transmitted; awaiting response (RFC 7766 §9.3)
+	CQueryDone                                // response received and decoded
+	CQueryAborted                             // query abandoned (connection error or caller abort)
+)
+
 func b2u8(b bool) uint8 {
 	if b {
 		return 1
@@ -26,6 +26,11 @@ const (
 	MaxSizeUDP = 512
 )

+// Message is a convenience type for decoding DNS messages and storing results in a single object.
+// Message is designed for ease of memory reuse. All internal buffers in a Message are reused in methods:
+// - [Message.Decode]: Limited in decode size by [Message.LimitResourceDecoding] which must be called beforehand.
+// - [Message.CopyFrom]
+// - [Message.AddQuestions]
 type Message struct {
 	Questions   []Question
 	Answers     []Resource
@@ -598,8 +603,6 @@ func append32(b []byte, v uint32) []byte {
 }

 func visitAllLabels(msg []byte, off uint16, fn func(b []byte), allowCompression bool) (uint16, error) {
-	// currOff is the current working offset.
-	currOff := off
 	if len(msg) > math.MaxUint16 {
 		return off, errResTooLong
 	}
@@ -610,60 +613,86 @@ func visitAllLabels(msg []byte, off uint16, fn func(b []byte), allowCompression
 	// the usage of this name.
 	var newOff = off

-LOOP:
 	for {
-		if currOff >= uint16(len(msg)) {
-			return off, lneto.ErrTruncatedFrame
-		}
-		c := uint16(msg[currOff])
-		currOff++
-		switch c & 0xc0 {
-		case 0x00: // String label (segment).
-			if c == 0x00 {
-				break LOOP // Nominal end of name, always ends with null terminator.
-			}
-			endOff := currOff + c
-			if endOff > uint16(len(msg)) {
-				return off, errCalcLen
-			}
-
-			// Reject names containing dots. See issue golang/go#56246
-			if bytes.IndexByte(msg[currOff:endOff], '.') >= 0 {
-				return off, errInvalidName
-			}
-
-			fn(msg[currOff:endOff])
-			currOff = endOff
-
-		case 0xc0: // Pointer.
-			// https://cs.opensource.google/go/x/net/+/refs/tags/v0.19.0:dns/dnsmessage/message.go;l=2078
-			if !allowCompression {
-				return off, errCompressedSRV
-			}
-			if currOff >= uint16(len(msg)) {
-				return off, errInvalidPtr
-			}
-			c1 := msg[currOff]
-			currOff++
+		start, end, isPtr, err := NextLabel(msg[off:])
+		if err != nil {
+			return off, err
+		} else if start == end {
 			if ptr == 0 {
-				newOff = currOff
+				newOff = off + 1 // advance past the null terminator byte
 			}
-			// Don't follow too many pointers, maybe there's a loop.
-			if ptr++; ptr > 10 {
-				return off, errTooManyPtr
+			break
+		} else if isPtr {
+			if !allowCompression {
+				return newOff, errCompressedSRV
 			}
-			currOff = (c^0xC0)<<8 | uint16(c1)
-		default:
-			// Prefixes 0x80 and 0x40 are reserved.
-			return off, errReserved
+			if ptr == 0 {
+				newOff = off + 2 // next record follows the 2-byte pointer
+			}
+			off = start
+			if int(off) >= len(msg) {
+				return newOff, errInvalidPtr
+			} else if ptr++; ptr > 10 {
+				return newOff, errTooManyPtr
+			}
+		} else {
+			// Is normal label; start/end are relative to msg[off:].
+			fn(msg[off+start : off+end])
+			off += end
 		}
 	}
-	if ptr == 0 {
-		newOff = currOff
-	}
 	return newOff, nil
 }

+// NextLabel parses the first control byte of data and returns the position and extent of next DNS label.
+//
+// For a normal string label (RFC 1035 §3.1), isPointer==false and start/end are
+// byte indices into data: data[start:end] holds the raw label bytes.
+// A null terminator (c==0) signals the end of the name: start==end==1, err==nil.
+//
+// For a compression pointer (RFC 1035 §4.1.4), isPointer==true:
+//   - start is the absolute target offset within the full DNS message to jump to.
+//   - end==0 (sentinel; not a data range).
+//
+// Returns [lneto.ErrTruncatedFrame] if data is too short to read the full label or pointer.
+// Returns errReserved for the 0x40 and 0x80 reserved prefix classes.
+func NextLabel(data []byte) (start_RelOrAbs, endRel uint16, isAbsPointer bool, err error) {
+	// Default invalid values
+	start_RelOrAbs, endRel = 0, 0
+	if len(data) == 0 {
+		return start_RelOrAbs, endRel, false, lneto.ErrTruncatedFrame
+	}
+	c := uint16(data[0])
+	switch c & 0xc0 {
+	case 0:
+		start_RelOrAbs = 1
+		// String label segment.
+		if c == 0 {
+			return start_RelOrAbs, start_RelOrAbs, false, nil // Null terminator. String ended.
+		}
+		endRel = start_RelOrAbs + c
+		if int(endRel) > len(data) {
+			return start_RelOrAbs, endRel, false, lneto.ErrTruncatedFrame
+		}
+		// Reject names containing dots. See issue golang/go#56246
+		if bytes.IndexByte(data[start_RelOrAbs:endRel], '.') >= 0 {
+			return start_RelOrAbs, endRel, false, errInvalidName
+		}
+		// Correct label!
+	case 0xc0:
+		// Pointer. Start is absolute index in DNS message.
+		isAbsPointer = true
+		if len(data) < 2 {
+			return start_RelOrAbs, endRel, isAbsPointer, lneto.ErrTruncatedFrame // Need more data to fully read pointer.
+		}
+		c1 := uint16(data[1])
+		start_RelOrAbs = (c^0xC0)<<8 | c1
+	default:
+		err = errReserved
+	}
+	return start_RelOrAbs, endRel, isAbsPointer, err
+}
+
 func (dst *Message) CopyFrom(m Message) {
 	internal.SliceReuse(&dst.Questions, len(m.Questions))
 	internal.SliceReuse(&dst.Answers, len(m.Answers))