80 lines
1.9 KiB
Go
80 lines
1.9 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package tcp
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import (
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"sync"
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)
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// segmentQueue is a bounded, thread-safe queue of TCP segments.
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//
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// +stateify savable
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type segmentQueue struct {
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mu sync.Mutex `state:"nosave"`
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list segmentList `state:"wait"`
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limit int
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used int
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}
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// empty determines if the queue is empty.
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func (q *segmentQueue) empty() bool {
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q.mu.Lock()
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r := q.used == 0
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q.mu.Unlock()
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return r
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}
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// setLimit updates the limit. No segments are immediately dropped in case the
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// queue becomes full due to the new limit.
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func (q *segmentQueue) setLimit(limit int) {
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q.mu.Lock()
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q.limit = limit
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q.mu.Unlock()
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}
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// enqueue adds the given segment to the queue.
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//
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// Returns true when the segment is successfully added to the queue, in which
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// case ownership of the reference is transferred to the queue. And returns
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// false if the queue is full, in which case ownership is retained by the
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// caller.
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func (q *segmentQueue) enqueue(s *segment) bool {
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q.mu.Lock()
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r := q.used < q.limit
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if r {
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q.list.PushBack(s)
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q.used++
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}
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q.mu.Unlock()
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return r
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}
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// dequeue removes and returns the next segment from queue, if one exists.
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// Ownership is transferred to the caller, who is responsible for decrementing
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// the ref count when done.
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func (q *segmentQueue) dequeue() *segment {
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q.mu.Lock()
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s := q.list.Front()
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if s != nil {
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q.list.Remove(s)
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q.used--
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}
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q.mu.Unlock()
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return s
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}
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