Mix checklocks and atomic analyzers.

This change makes the checklocks analyzer considerable more powerful, adding:
* The ability to traverse complex structures, e.g. to have multiple nested
  fields as part of the annotation.
* The ability to resolve simple anonymous functions and closures, and perform
  lock analysis across these invocations. This does not apply to closures that
  are passed elsewhere, since it is not possible to know the context in which
  they might be invoked.
* The ability to annotate return values in addition to receivers and other
  parameters, with the same complex structures noted above.
* Ignoring locking semantics for "fresh" objects, i.e. objects that are
  allocated in the local frame (typically a new-style function).
* Sanity checking of locking state across block transitions and returns, to
  ensure that no unexpected locks are held.

Note that initially, most of these findings are excluded by a comprehensive
nogo.yaml. The findings that are included are fundamental lock violations.
The changes here should be relatively low risk, minor refactorings to either
include necessary annotations to simplify the code structure (in general
removing closures in favor of methods) so that the analyzer can be easily
track the lock state.

This change additional includes two changes to nogo itself:
* Sanity checking of all types to ensure that the binary and ast-derived
  types have a consistent objectpath, to prevent the bug above from occurring
  silently (and causing much confusion). This also requires a trick in
  order to ensure that serialized facts are consumable downstream. This can
  be removed with https://go-review.googlesource.com/c/tools/+/331789 merged.
* A minor refactoring to isolation the objdump settings in its own package.
  This was originally used to implement the sanity check above, but this
  information is now being passed another way. The minor refactor is preserved
  however, since it cleans up the code slightly and is minimal risk.

PiperOrigin-RevId: 382613300

1 files changed, 84 insertions, 66 deletions

diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index def9d7186..82a3f2287 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -364,6 +364,7 @@ func (e *endpoint) Read(dst io.Writer, opts tcpip.ReadOptions) (tcpip.ReadResult
 // reacquire the mutex in exclusive mode.
 //
 // Returns true for retry if preparation should be retried.
+// +checklocks:e.mu
 func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err tcpip.Error) {
 	switch e.EndpointState() {
 	case StateInitial:
@@ -380,10 +381,8 @@ func (e *endpoint) prepareForWrite(to *tcpip.FullAddress) (retry bool, err tcpip
 	}
 
 	e.mu.RUnlock()
-	defer e.mu.RLock()
-
 	e.mu.Lock()
-	defer e.mu.Unlock()
+	defer e.mu.DowngradeLock()
 
 	// The state changed when we released the shared locked and re-acquired
 	// it in exclusive mode. Try again.
@@ -449,37 +448,20 @@ func (e *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 	return n, err
 }
 
-func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
-	if err := e.LastError(); err != nil {
-		return 0, err
-	}
-
-	// MSG_MORE is unimplemented. (This also means that MSG_EOR is a no-op.)
-	if opts.More {
-		return 0, &tcpip.ErrInvalidOptionValue{}
-	}
-
-	to := opts.To
-
+func (e *endpoint) buildUDPPacketInfo(p tcpip.Payloader, opts tcpip.WriteOptions) (udpPacketInfo, tcpip.Error) {
 	e.mu.RLock()
-	lockReleased := false
-	defer func() {
-		if lockReleased {
-			return
-		}
-		e.mu.RUnlock()
-	}()
+	defer e.mu.RUnlock()
 
 	// If we've shutdown with SHUT_WR we are in an invalid state for sending.
 	if e.shutdownFlags&tcpip.ShutdownWrite != 0 {
-		return 0, &tcpip.ErrClosedForSend{}
+		return udpPacketInfo{}, &tcpip.ErrClosedForSend{}
 	}
 
 	// Prepare for write.
 	for {
-		retry, err := e.prepareForWrite(to)
+		retry, err := e.prepareForWrite(opts.To)
 		if err != nil {
-			return 0, err
+			return udpPacketInfo{}, err
 		}
 
 		if !retry {
@@ -489,34 +471,34 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 
 	route := e.route
 	dstPort := e.dstPort
-	if to != nil {
+	if opts.To != nil {
 		// Reject destination address if it goes through a different
 		// NIC than the endpoint was bound to.
-		nicID := to.NIC
+		nicID := opts.To.NIC
 		if nicID == 0 {
 			nicID = tcpip.NICID(e.ops.GetBindToDevice())
 		}
 		if e.BindNICID != 0 {
 			if nicID != 0 && nicID != e.BindNICID {
-				return 0, &tcpip.ErrNoRoute{}
+				return udpPacketInfo{}, &tcpip.ErrNoRoute{}
 			}
 
 			nicID = e.BindNICID
 		}
 
-		if to.Port == 0 {
+		if opts.To.Port == 0 {
 			// Port 0 is an invalid port to send to.
-			return 0, &tcpip.ErrInvalidEndpointState{}
+			return udpPacketInfo{}, &tcpip.ErrInvalidEndpointState{}
 		}
 
-		dst, netProto, err := e.checkV4MappedLocked(*to)
+		dst, netProto, err := e.checkV4MappedLocked(*opts.To)
 		if err != nil {
-			return 0, err
+			return udpPacketInfo{}, err
 		}
 
 		r, _, err := e.connectRoute(nicID, dst, netProto)
 		if err != nil {
-			return 0, err
+			return udpPacketInfo{}, err
 		}
 		defer r.Release()
 
@@ -525,12 +507,12 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 	}
 
 	if !e.ops.GetBroadcast() && route.IsOutboundBroadcast() {
-		return 0, &tcpip.ErrBroadcastDisabled{}
+		return udpPacketInfo{}, &tcpip.ErrBroadcastDisabled{}
 	}
 
 	v := make([]byte, p.Len())
 	if _, err := io.ReadFull(p, v); err != nil {
-		return 0, &tcpip.ErrBadBuffer{}
+		return udpPacketInfo{}, &tcpip.ErrBadBuffer{}
 	}
 	if len(v) > header.UDPMaximumPacketSize {
 		// Payload can't possibly fit in a packet.
@@ -548,24 +530,39 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 				v,
 			)
 		}
-		return 0, &tcpip.ErrMessageTooLong{}
+		return udpPacketInfo{}, &tcpip.ErrMessageTooLong{}
 	}
 
 	ttl := e.ttl
 	useDefaultTTL := ttl == 0
-
 	if header.IsV4MulticastAddress(route.RemoteAddress()) || header.IsV6MulticastAddress(route.RemoteAddress()) {
 		ttl = e.multicastTTL
 		// Multicast allows a 0 TTL.
 		useDefaultTTL = false
 	}
 
-	localPort := e.ID.LocalPort
-	sendTOS := e.sendTOS
-	owner := e.owner
-	noChecksum := e.SocketOptions().GetNoChecksum()
-	lockReleased = true
-	e.mu.RUnlock()
+	return udpPacketInfo{
+		route:         route,
+		data:          buffer.View(v),
+		localPort:     e.ID.LocalPort,
+		remotePort:    dstPort,
+		ttl:           ttl,
+		useDefaultTTL: useDefaultTTL,
+		tos:           e.sendTOS,
+		owner:         e.owner,
+		noChecksum:    e.SocketOptions().GetNoChecksum(),
+	}, nil
+}
+
+func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcpip.Error) {
+	if err := e.LastError(); err != nil {
+		return 0, err
+	}
+
+	// MSG_MORE is unimplemented. (This also means that MSG_EOR is a no-op.)
+	if opts.More {
+		return 0, &tcpip.ErrInvalidOptionValue{}
+	}
 
 	// Do not hold lock when sending as loopback is synchronous and if the UDP
 	// datagram ends up generating an ICMP response then it can result in a
@@ -577,10 +574,15 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 	//
 	// See: https://golang.org/pkg/sync/#RWMutex for details on why recursive read
 	// locking is prohibited.
-	if err := sendUDP(route, buffer.View(v).ToVectorisedView(), localPort, dstPort, ttl, useDefaultTTL, sendTOS, owner, noChecksum); err != nil {
+	u, err := e.buildUDPPacketInfo(p, opts)
+	if err != nil {
 		return 0, err
 	}
-	return int64(len(v)), nil
+	n, err := u.send()
+	if err != nil {
+		return 0, err
+	}
+	return int64(n), nil
 }
 
 // OnReuseAddressSet implements tcpip.SocketOptionsHandler.
@@ -817,14 +819,30 @@ func (e *endpoint) GetSockOpt(opt tcpip.GettableSocketOption) tcpip.Error {
 	return nil
 }
 
-// sendUDP sends a UDP segment via the provided network endpoint and under the
-// provided identity.
-func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort uint16, ttl uint8, useDefaultTTL bool, tos uint8, owner tcpip.PacketOwner, noChecksum bool) tcpip.Error {
+// udpPacketInfo contains all information required to send a UDP packet.
+//
+// This should be used as a value-only type, which exists in order to simplify
+// return value syntax. It should not be exported or extended.
+type udpPacketInfo struct {
+	route         *stack.Route
+	data          buffer.View
+	localPort     uint16
+	remotePort    uint16
+	ttl           uint8
+	useDefaultTTL bool
+	tos           uint8
+	owner         tcpip.PacketOwner
+	noChecksum    bool
+}
+
+// send sends the given packet.
+func (u *udpPacketInfo) send() (int, tcpip.Error) {
+	vv := u.data.ToVectorisedView()
 	pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
-		ReserveHeaderBytes: header.UDPMinimumSize + int(r.MaxHeaderLength()),
-		Data:               data,
+		ReserveHeaderBytes: header.UDPMinimumSize + int(u.route.MaxHeaderLength()),
+		Data:               vv,
 	})
-	pkt.Owner = owner
+	pkt.Owner = u.owner
 
 	// Initialize the UDP header.
 	udp := header.UDP(pkt.TransportHeader().Push(header.UDPMinimumSize))
@@ -832,8 +850,8 @@ func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort u
 
 	length := uint16(pkt.Size())
 	udp.Encode(&header.UDPFields{
-		SrcPort: localPort,
-		DstPort: remotePort,
+		SrcPort: u.localPort,
+		DstPort: u.remotePort,
 		Length:  length,
 	})
 
@@ -841,30 +859,30 @@ func sendUDP(r *stack.Route, data buffer.VectorisedView, localPort, remotePort u
 	// On IPv4, UDP checksum is optional, and a zero value indicates the
 	// transmitter skipped the checksum generation (RFC768).
 	// On IPv6, UDP checksum is not optional (RFC2460 Section 8.1).
-	if r.RequiresTXTransportChecksum() &&
-		(!noChecksum || r.NetProto() == header.IPv6ProtocolNumber) {
-		xsum := r.PseudoHeaderChecksum(ProtocolNumber, length)
-		for _, v := range data.Views() {
+	if u.route.RequiresTXTransportChecksum() &&
+		(!u.noChecksum || u.route.NetProto() == header.IPv6ProtocolNumber) {
+		xsum := u.route.PseudoHeaderChecksum(ProtocolNumber, length)
+		for _, v := range vv.Views() {
 			xsum = header.Checksum(v, xsum)
 		}
 		udp.SetChecksum(^udp.CalculateChecksum(xsum))
 	}
 
-	if useDefaultTTL {
-		ttl = r.DefaultTTL()
+	if u.useDefaultTTL {
+		u.ttl = u.route.DefaultTTL()
 	}
-	if err := r.WritePacket(stack.NetworkHeaderParams{
+	if err := u.route.WritePacket(stack.NetworkHeaderParams{
 		Protocol: ProtocolNumber,
-		TTL:      ttl,
-		TOS:      tos,
+		TTL:      u.ttl,
+		TOS:      u.tos,
 	}, pkt); err != nil {
-		r.Stats().UDP.PacketSendErrors.Increment()
-		return err
+		u.route.Stats().UDP.PacketSendErrors.Increment()
+		return 0, err
 	}
 
 	// Track count of packets sent.
-	r.Stats().UDP.PacketsSent.Increment()
-	return nil
+	u.route.Stats().UDP.PacketsSent.Increment()
+	return len(u.data), nil
 }
 
 // checkV4MappedLocked determines the effective network protocol and converts