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// Copyright 2018 The gVisor Authors.
//
// 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 (
"syscall"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/refs"
"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
"gvisor.dev/gvisor/pkg/sync"
)
// +stateify savable
type abstractEndpoint struct {
ep transport.BoundEndpoint
wr *refs.WeakRef
name string
ns *AbstractSocketNamespace
}
// WeakRefGone implements refs.WeakRefUser.WeakRefGone.
func (e *abstractEndpoint) WeakRefGone(context.Context) {
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.
//
// +stateify savable
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 transport.BoundEndpoint to maintain a reference on
// its backing object.
type boundEndpoint struct {
transport.BoundEndpoint
rc refs.RefCounter
}
// Release implements transport.BoundEndpoint.Release.
func (e *boundEndpoint) Release(ctx context.Context) {
e.rc.DecRef(ctx)
e.BoundEndpoint.Release(ctx)
}
// 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) transport.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(ctx context.Context, name string, ep transport.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(ctx)
return syscall.EADDRINUSE
}
}
ae := abstractEndpoint{ep: ep, name: name, ns: a}
ae.wr = refs.NewWeakRef(rc, &ae)
a.endpoints[name] = ae
return nil
}
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