4 files changed, 188 insertions, 40 deletions
diff --git a/pkg/tcpip/link/tun/BUILD b/pkg/tcpip/link/tun/BUILD
deleted file mode 100644
index 0243424f6..000000000
--- a/pkg/tcpip/link/tun/BUILD
+++ /dev/null
@@ -1,40 +0,0 @@
-load("//tools:defs.bzl", "go_library")
-load("//tools/go_generics:defs.bzl", "go_template_instance")
-
-package(licenses = ["notice"])
-
-go_template_instance(
-    name = "tun_endpoint_refs",
-    out = "tun_endpoint_refs.go",
-    package = "tun",
-    prefix = "tunEndpoint",
-    template = "//pkg/refs_vfs2:refs_template",
-    types = {
-        "T": "tunEndpoint",
-    },
-)
-
-go_library(
-    name = "tun",
-    srcs = [
-        "device.go",
-        "protocol.go",
-        "tun_endpoint_refs.go",
-        "tun_unsafe.go",
-    ],
-    visibility = ["//visibility:public"],
-    deps = [
-        "//pkg/abi/linux",
-        "//pkg/context",
-        "//pkg/log",
-        "//pkg/refs",
-        "//pkg/sync",
-        "//pkg/syserror",
-        "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
-        "//pkg/tcpip/header",
-        "//pkg/tcpip/link/channel",
-        "//pkg/tcpip/stack",
-        "//pkg/waiter",
-    ],
-)
diff --git a/pkg/tcpip/link/tun/tun_endpoint_refs.go b/pkg/tcpip/link/tun/tun_endpoint_refs.go
new file mode 100644
index 000000000..06d11f0e1
--- /dev/null
+++ b/pkg/tcpip/link/tun/tun_endpoint_refs.go
@@ -0,0 +1,118 @@
+package tun
+
+import (
+	"sync/atomic"
+
+	"fmt"
+	"gvisor.dev/gvisor/pkg/log"
+	refs_vfs1 "gvisor.dev/gvisor/pkg/refs"
+	"runtime"
+)
+
+// ownerType is used to customize logging. Note that we use a pointer to T so
+// that we do not copy the entire object when passed as a format parameter.
+var tunEndpointownerType *tunEndpoint
+
+// Refs implements refs.RefCounter. It keeps a reference count using atomic
+// operations and calls the destructor when the count reaches zero.
+//
+// Note that the number of references is actually refCount + 1 so that a default
+// zero-value Refs object contains one reference.
+//
+// TODO(gvisor.dev/issue/1486): Store stack traces when leak check is enabled in
+// a map with 16-bit hashes, and store the hash in the top 16 bits of refCount.
+// This will allow us to add stack trace information to the leak messages
+// without growing the size of Refs.
+//
+// +stateify savable
+type tunEndpointRefs struct {
+	// refCount is composed of two fields:
+	//
+	//	[32-bit speculative references]:[32-bit real references]
+	//
+	// Speculative references are used for TryIncRef, to avoid a CompareAndSwap
+	// loop. See IncRef, DecRef and TryIncRef for details of how these fields are
+	// used.
+	refCount int64
+}
+
+func (r *tunEndpointRefs) finalize() {
+	var note string
+	switch refs_vfs1.GetLeakMode() {
+	case refs_vfs1.NoLeakChecking:
+		return
+	case refs_vfs1.UninitializedLeakChecking:
+		note = "(Leak checker uninitialized): "
+	}
+	if n := r.ReadRefs(); n != 0 {
+		log.Warningf("%sRefs %p owned by %T garbage collected with ref count of %d (want 0)", note, r, tunEndpointownerType, n)
+	}
+}
+
+// EnableLeakCheck checks for reference leaks when Refs gets garbage collected.
+func (r *tunEndpointRefs) EnableLeakCheck() {
+	if refs_vfs1.GetLeakMode() != refs_vfs1.NoLeakChecking {
+		runtime.SetFinalizer(r, (*tunEndpointRefs).finalize)
+	}
+}
+
+// ReadRefs returns the current number of references. The returned count is
+// inherently racy and is unsafe to use without external synchronization.
+func (r *tunEndpointRefs) ReadRefs() int64 {
+
+	return atomic.LoadInt64(&r.refCount) + 1
+}
+
+// IncRef implements refs.RefCounter.IncRef.
+//
+//go:nosplit
+func (r *tunEndpointRefs) IncRef() {
+	if v := atomic.AddInt64(&r.refCount, 1); v <= 0 {
+		panic(fmt.Sprintf("Incrementing non-positive ref count %p owned by %T", r, tunEndpointownerType))
+	}
+}
+
+// TryIncRef implements refs.RefCounter.TryIncRef.
+//
+// To do this safely without a loop, a speculative reference is first acquired
+// on the object. This allows multiple concurrent TryIncRef calls to distinguish
+// other TryIncRef calls from genuine references held.
+//
+//go:nosplit
+func (r *tunEndpointRefs) TryIncRef() bool {
+	const speculativeRef = 1 << 32
+	v := atomic.AddInt64(&r.refCount, speculativeRef)
+	if int32(v) < 0 {
+
+		atomic.AddInt64(&r.refCount, -speculativeRef)
+		return false
+	}
+
+	atomic.AddInt64(&r.refCount, -speculativeRef+1)
+	return true
+}
+
+// DecRef implements refs.RefCounter.DecRef.
+//
+// Note that speculative references are counted here. Since they were added
+// prior to real references reaching zero, they will successfully convert to
+// real references. In other words, we see speculative references only in the
+// following case:
+//
+//	A: TryIncRef [speculative increase => sees non-negative references]
+//	B: DecRef [real decrease]
+//	A: TryIncRef [transform speculative to real]
+//
+//go:nosplit
+func (r *tunEndpointRefs) DecRef(destroy func()) {
+	switch v := atomic.AddInt64(&r.refCount, -1); {
+	case v < -1:
+		panic(fmt.Sprintf("Decrementing non-positive ref count %p, owned by %T", r, tunEndpointownerType))
+
+	case v == -1:
+
+		if destroy != nil {
+			destroy()
+		}
+	}
+}
diff --git a/pkg/tcpip/link/tun/tun_state_autogen.go b/pkg/tcpip/link/tun/tun_state_autogen.go
new file mode 100644
index 000000000..0b3041e84
--- /dev/null
+++ b/pkg/tcpip/link/tun/tun_state_autogen.go
@@ -0,0 +1,65 @@
+// automatically generated by stateify.
+
+package tun
+
+import (
+	"gvisor.dev/gvisor/pkg/state"
+)
+
+func (x *Device) StateTypeName() string {
+	return "pkg/tcpip/link/tun.Device"
+}
+
+func (x *Device) StateFields() []string {
+	return []string{
+		"Queue",
+		"endpoint",
+		"notifyHandle",
+		"flags",
+	}
+}
+
+func (x *Device) StateSave(m state.Sink) {
+	x.beforeSave()
+	m.Save(0, &x.Queue)
+	m.Save(1, &x.endpoint)
+	m.Save(2, &x.notifyHandle)
+	m.Save(3, &x.flags)
+}
+
+func (x *Device) afterLoad() {}
+
+func (x *Device) StateLoad(m state.Source) {
+	m.Load(0, &x.Queue)
+	m.Load(1, &x.endpoint)
+	m.Load(2, &x.notifyHandle)
+	m.Load(3, &x.flags)
+}
+
+func (x *tunEndpointRefs) StateTypeName() string {
+	return "pkg/tcpip/link/tun.tunEndpointRefs"
+}
+
+func (x *tunEndpointRefs) StateFields() []string {
+	return []string{
+		"refCount",
+	}
+}
+
+func (x *tunEndpointRefs) beforeSave() {}
+
+func (x *tunEndpointRefs) StateSave(m state.Sink) {
+	x.beforeSave()
+	m.Save(0, &x.refCount)
+}
+
+func (x *tunEndpointRefs) afterLoad() {}
+
+func (x *tunEndpointRefs) StateLoad(m state.Source) {
+	m.Load(0, &x.refCount)
+}
+
+func init() {
+	state.Register((*Device)(nil))
+	state.Register((*tunEndpointRefs)(nil))
+}
diff --git a/pkg/tcpip/link/tun/tun_unsafe_state_autogen.go b/pkg/tcpip/link/tun/tun_unsafe_state_autogen.go
new file mode 100644
index 000000000..149299ea3
--- /dev/null
+++ b/pkg/tcpip/link/tun/tun_unsafe_state_autogen.go
@@ -0,0 +1,5 @@
+// automatically generated by stateify.
+
+// +build linux
+
+package tun