102 lines
2.8 KiB
Go
102 lines
2.8 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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"gvisor.dev/gvisor/pkg/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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ep *endpoint
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frozen bool
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}
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// emptyLocked determines if the queue is empty.
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// Preconditions: q.mu must be held.
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func (q *segmentQueue) emptyLocked() bool {
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return q.list.Empty()
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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.emptyLocked()
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q.mu.Unlock()
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return r
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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.ep.receiveBufferParams() must be called without holding q.mu to
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// avoid lock order inversion.
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bufSz := q.ep.receiveBufferSize()
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used := q.ep.receiveMemUsed()
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q.mu.Lock()
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// Allow zero sized segments (ACK/FIN/RSTs etc even if the segment queue
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// is currently full).
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allow := (used <= bufSz || s.payloadSize() == 0) && !q.frozen
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if allow {
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q.list.PushBack(s)
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// Set the owner now that the endpoint owns the segment.
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s.setOwner(q.ep, recvQ)
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}
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q.mu.Unlock()
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return allow
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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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}
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q.mu.Unlock()
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return s
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}
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// freeze prevents any more segments from being added to the queue. i.e all
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// future segmentQueue.enqueue will return false and not add the segment to the
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// queue till the queue is unfroze with a corresponding segmentQueue.thaw call.
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func (q *segmentQueue) freeze() {
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q.mu.Lock()
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q.frozen = true
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q.mu.Unlock()
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}
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// thaw unfreezes a previously frozen queue using segmentQueue.freeze() and
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// allows new segments to be queued again.
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func (q *segmentQueue) thaw() {
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q.mu.Lock()
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q.frozen = false
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q.mu.Unlock()
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}
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