Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 108 insertions, 0 deletions

diff --git a/pkg/sentry/kernel/abstract_socket_namespace.go b/pkg/sentry/kernel/abstract_socket_namespace.go
new file mode 100644
index 000000000..014c4a3bf
--- /dev/null
+++ b/pkg/sentry/kernel/abstract_socket_namespace.go
@@ -0,0 +1,108 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package kernel
+
+import (
+	"sync"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/refs"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/transport/unix"
+)
+
+type abstractEndpoint struct {
+	ep   unix.BoundEndpoint
+	wr   *refs.WeakRef
+	name string
+	ns   *AbstractSocketNamespace
+}
+
+// WeakRefGone implements refs.WeakRefUser.WeakRefGone.
+func (e *abstractEndpoint) WeakRefGone() {
+	e.ns.mu.Lock()
+	if e.ns.endpoints[e.name].ep == e.ep {
+		delete(e.ns.endpoints, e.name)
+	}
+	e.ns.mu.Unlock()
+}
+
+// AbstractSocketNamespace is used to implement the Linux abstract socket functionality.
+type AbstractSocketNamespace struct {
+	mu sync.Mutex `state:"nosave"`
+
+	// Keeps mapping from name to endpoint.
+	endpoints map[string]abstractEndpoint
+}
+
+// NewAbstractSocketNamespace returns a new AbstractSocketNamespace.
+func NewAbstractSocketNamespace() *AbstractSocketNamespace {
+	return &AbstractSocketNamespace{
+		endpoints: make(map[string]abstractEndpoint),
+	}
+}
+
+// A boundEndpoint wraps a unix.BoundEndpoint to maintain a reference on its
+// backing object.
+type boundEndpoint struct {
+	unix.BoundEndpoint
+	rc refs.RefCounter
+}
+
+// Release implements unix.BoundEndpoint.Release.
+func (e *boundEndpoint) Release() {
+	e.rc.DecRef()
+	e.BoundEndpoint.Release()
+}
+
+// BoundEndpoint retrieves the endpoint bound to the given name. The return
+// value is nil if no endpoint was bound.
+func (a *AbstractSocketNamespace) BoundEndpoint(name string) unix.BoundEndpoint {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	ep, ok := a.endpoints[name]
+	if !ok {
+		return nil
+	}
+
+	rc := ep.wr.Get()
+	if rc == nil {
+		delete(a.endpoints, name)
+		return nil
+	}
+
+	return &boundEndpoint{ep.ep, rc}
+}
+
+// Bind binds the given socket.
+//
+// When the last reference managed by rc is dropped, ep may be removed from the
+// namespace.
+func (a *AbstractSocketNamespace) Bind(name string, ep unix.BoundEndpoint, rc refs.RefCounter) error {
+	a.mu.Lock()
+	defer a.mu.Unlock()
+
+	if ep, ok := a.endpoints[name]; ok {
+		if rc := ep.wr.Get(); rc != nil {
+			rc.DecRef()
+			return syscall.EADDRINUSE
+		}
+	}
+
+	ae := abstractEndpoint{ep: ep, name: name, ns: a}
+	ae.wr = refs.NewWeakRef(rc, &ae)
+	a.endpoints[name] = ae
+	return nil
+}