2 files changed, 242 insertions, 0 deletions
diff --git a/pkg/sentry/socket/unix/transport/queue/BUILD b/pkg/sentry/socket/unix/transport/queue/BUILD
new file mode 100644
index 000000000..d914ecc23
--- /dev/null
+++ b/pkg/sentry/socket/unix/transport/queue/BUILD
@@ -0,0 +1,15 @@
+package(licenses = ["notice"])  # Apache 2.0
+
+load("//tools/go_stateify:defs.bzl", "go_library")
+
+go_library(
+    name = "queue",
+    srcs = ["queue.go"],
+    importpath = "gvisor.googlesource.com/gvisor/pkg/sentry/socket/unix/transport/queue",
+    visibility = ["//:sandbox"],
+    deps = [
+        "//pkg/ilist",
+        "//pkg/tcpip",
+        "//pkg/waiter",
+    ],
+)
diff --git a/pkg/sentry/socket/unix/transport/queue/queue.go b/pkg/sentry/socket/unix/transport/queue/queue.go
new file mode 100644
index 000000000..b3d2ea68b
--- /dev/null
+++ b/pkg/sentry/socket/unix/transport/queue/queue.go
@@ -0,0 +1,227 @@
+// 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 queue provides the implementation of buffer queue
+// and interface of queue entry with Length method.
+package queue
+
+import (
+	"sync"
+
+	"gvisor.googlesource.com/gvisor/pkg/ilist"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// Entry implements Linker interface and has additional required methods.
+type Entry interface {
+	ilist.Linker
+
+	// Length returns the number of bytes stored in the entry.
+	Length() int64
+
+	// Release releases any resources held by the entry.
+	Release()
+
+	// Peek returns a copy of the entry. It must be Released separately.
+	Peek() Entry
+
+	// Truncate reduces the number of bytes stored in the entry to n bytes.
+	//
+	// Preconditions: n <= Length().
+	Truncate(n int64)
+}
+
+// Queue is a buffer queue.
+//
+// +stateify savable
+type Queue struct {
+	ReaderQueue *waiter.Queue
+	WriterQueue *waiter.Queue
+
+	mu       sync.Mutex `state:"nosave"`
+	closed   bool
+	used     int64
+	limit    int64
+	dataList ilist.List
+}
+
+// New allocates and initializes a new queue.
+func New(ReaderQueue *waiter.Queue, WriterQueue *waiter.Queue, limit int64) *Queue {
+	return &Queue{ReaderQueue: ReaderQueue, WriterQueue: WriterQueue, limit: limit}
+}
+
+// Close closes q for reading and writing. It is immediately not writable and
+// will become unreadable when no more data is pending.
+//
+// Both the read and write queues must be notified after closing:
+// q.ReaderQueue.Notify(waiter.EventIn)
+// q.WriterQueue.Notify(waiter.EventOut)
+func (q *Queue) Close() {
+	q.mu.Lock()
+	q.closed = true
+	q.mu.Unlock()
+}
+
+// Reset empties the queue and Releases all of the Entries.
+//
+// Both the read and write queues must be notified after resetting:
+// q.ReaderQueue.Notify(waiter.EventIn)
+// q.WriterQueue.Notify(waiter.EventOut)
+func (q *Queue) Reset() {
+	q.mu.Lock()
+	for cur := q.dataList.Front(); cur != nil; cur = cur.Next() {
+		cur.(Entry).Release()
+	}
+	q.dataList.Reset()
+	q.used = 0
+	q.mu.Unlock()
+}
+
+// IsReadable determines if q is currently readable.
+func (q *Queue) IsReadable() bool {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+
+	return q.closed || q.dataList.Front() != nil
+}
+
+// bufWritable returns true if there is space for writing.
+//
+// N.B. Linux only considers a unix socket "writable" if >75% of the buffer is
+// free.
+//
+// See net/unix/af_unix.c:unix_writeable.
+func (q *Queue) bufWritable() bool {
+	return 4*q.used < q.limit
+}
+
+// IsWritable determines if q is currently writable.
+func (q *Queue) IsWritable() bool {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+
+	return q.closed || q.bufWritable()
+}
+
+// Enqueue adds an entry to the data queue if room is available.
+//
+// If truncate is true, Enqueue may truncate the message beforing enqueuing it.
+// Otherwise, the entire message must fit. If n < e.Length(), err indicates why.
+//
+// If notify is true, ReaderQueue.Notify must be called:
+// q.ReaderQueue.Notify(waiter.EventIn)
+func (q *Queue) Enqueue(e Entry, truncate bool) (l int64, notify bool, err *tcpip.Error) {
+	q.mu.Lock()
+
+	if q.closed {
+		q.mu.Unlock()
+		return 0, false, tcpip.ErrClosedForSend
+	}
+
+	free := q.limit - q.used
+
+	l = e.Length()
+
+	if l > free && truncate {
+		if free == 0 {
+			// Message can't fit right now.
+			q.mu.Unlock()
+			return 0, false, tcpip.ErrWouldBlock
+		}
+
+		e.Truncate(free)
+		l = e.Length()
+		err = tcpip.ErrWouldBlock
+	}
+
+	if l > q.limit {
+		// Message is too big to ever fit.
+		q.mu.Unlock()
+		return 0, false, tcpip.ErrMessageTooLong
+	}
+
+	if l > free {
+		// Message can't fit right now.
+		q.mu.Unlock()
+		return 0, false, tcpip.ErrWouldBlock
+	}
+
+	notify = q.dataList.Front() == nil
+	q.used += l
+	q.dataList.PushBack(e)
+
+	q.mu.Unlock()
+
+	return l, notify, err
+}
+
+// Dequeue removes the first entry in the data queue, if one exists.
+//
+// If notify is true, WriterQueue.Notify must be called:
+// q.WriterQueue.Notify(waiter.EventOut)
+func (q *Queue) Dequeue() (e Entry, notify bool, err *tcpip.Error) {
+	q.mu.Lock()
+
+	if q.dataList.Front() == nil {
+		err := tcpip.ErrWouldBlock
+		if q.closed {
+			err = tcpip.ErrClosedForReceive
+		}
+		q.mu.Unlock()
+
+		return nil, false, err
+	}
+
+	notify = !q.bufWritable()
+
+	e = q.dataList.Front().(Entry)
+	q.dataList.Remove(e)
+	q.used -= e.Length()
+
+	notify = notify && q.bufWritable()
+
+	q.mu.Unlock()
+
+	return e, notify, nil
+}
+
+// Peek returns the first entry in the data queue, if one exists.
+func (q *Queue) Peek() (Entry, *tcpip.Error) {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+
+	if q.dataList.Front() == nil {
+		err := tcpip.ErrWouldBlock
+		if q.closed {
+			err = tcpip.ErrClosedForReceive
+		}
+		return nil, err
+	}
+
+	return q.dataList.Front().(Entry).Peek(), nil
+}
+
+// QueuedSize returns the number of bytes currently in the queue, that is, the
+// number of readable bytes.
+func (q *Queue) QueuedSize() int64 {
+	q.mu.Lock()
+	defer q.mu.Unlock()
+	return q.used
+}
+
+// MaxQueueSize returns the maximum number of bytes storable in the queue.
+func (q *Queue) MaxQueueSize() int64 {
+	return q.limit
+}