1 files changed, 23 insertions, 5 deletions
diff --git a/pkg/flipcall/flipcall_unsafe.go b/pkg/flipcall/flipcall_unsafe.go
index 7c8977893..a37952637 100644
--- a/pkg/flipcall/flipcall_unsafe.go
+++ b/pkg/flipcall/flipcall_unsafe.go
@@ -17,17 +17,19 @@ package flipcall
 import (
 	"reflect"
 	"unsafe"
+
+	"gvisor.dev/gvisor/third_party/gvsync"
 )
 
-// Packets consist of an 8-byte header followed by an arbitrarily-sized
+// Packets consist of a 16-byte header followed by an arbitrarily-sized
 // datagram. The header consists of:
 //
 // - A 4-byte native-endian connection state.
 //
 // - A 4-byte native-endian datagram length in bytes.
+//
+// - 8 reserved bytes.
 const (
-	sizeofUint32 = unsafe.Sizeof(uint32(0))
-
 	// PacketHeaderBytes is the size of a flipcall packet header in bytes. The
 	// maximum datagram size supported by a flipcall connection is equal to the
 	// length of the packet window minus PacketHeaderBytes.
@@ -35,7 +37,7 @@ const (
 	// PacketHeaderBytes is exported to support its use in constant
 	// expressions. Non-constant expressions may prefer to use
 	// PacketWindowLengthForDataCap().
-	PacketHeaderBytes = 2 * sizeofUint32
+	PacketHeaderBytes = 16
 )
 
 func (ep *Endpoint) connState() *uint32 {
@@ -43,7 +45,7 @@ func (ep *Endpoint) connState() *uint32 {
 }
 
 func (ep *Endpoint) dataLen() *uint32 {
-	return (*uint32)((unsafe.Pointer)(ep.packet + sizeofUint32))
+	return (*uint32)((unsafe.Pointer)(ep.packet + 4))
 }
 
 // Data returns the datagram part of ep's packet window as a byte slice.
@@ -67,3 +69,19 @@ func (ep *Endpoint) Data() []byte {
 	bsReflect.Cap = int(ep.dataCap)
 	return bs
 }
+
+// ioSync is a dummy variable used to indicate synchronization to the Go race
+// detector. Compare syscall.ioSync.
+var ioSync int64
+
+func raceBecomeActive() {
+	if gvsync.RaceEnabled {
+		gvsync.RaceAcquire((unsafe.Pointer)(&ioSync))
+	}
+}
+
+func raceBecomeInactive() {
+	if gvsync.RaceEnabled {
+		gvsync.RaceReleaseMerge((unsafe.Pointer)(&ioSync))
+	}
+}