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// Copyright 2016 The Netstack Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package fragmentation
import (
"container/heap"
"fmt"
"math"
"sync"
"time"
"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
)
type hole struct {
first uint16
last uint16
deleted bool
}
type reassembler struct {
reassemblerEntry
id uint32
size int
mu sync.Mutex
holes []hole
deleted int
heap fragHeap
done bool
creationTime time.Time
}
func newReassembler(id uint32) *reassembler {
r := &reassembler{
id: id,
holes: make([]hole, 0, 16),
deleted: 0,
heap: make(fragHeap, 0, 8),
creationTime: time.Now(),
}
r.holes = append(r.holes, hole{
first: 0,
last: math.MaxUint16,
deleted: false})
return r
}
// updateHoles updates the list of holes for an incoming fragment and
// returns true iff the fragment filled at least part of an existing hole.
func (r *reassembler) updateHoles(first, last uint16, more bool) bool {
used := false
for i := range r.holes {
if r.holes[i].deleted || first > r.holes[i].last || last < r.holes[i].first {
continue
}
used = true
r.deleted++
r.holes[i].deleted = true
if first > r.holes[i].first {
r.holes = append(r.holes, hole{r.holes[i].first, first - 1, false})
}
if last < r.holes[i].last && more {
r.holes = append(r.holes, hole{last + 1, r.holes[i].last, false})
}
}
return used
}
func (r *reassembler) process(first, last uint16, more bool, vv *buffer.VectorisedView) (buffer.VectorisedView, bool, int) {
r.mu.Lock()
defer r.mu.Unlock()
consumed := 0
if r.done {
// A concurrent goroutine might have already reassembled
// the packet and emptied the heap while this goroutine
// was waiting on the mutex. We don't have to do anything in this case.
return buffer.NewVectorisedView(0, nil), false, consumed
}
if r.updateHoles(first, last, more) {
// We store the incoming packet only if it filled some holes.
uu := vv.Clone(nil)
heap.Push(&r.heap, fragment{offset: first, vv: &uu})
consumed = vv.Size()
r.size += consumed
}
// Check if all the holes have been deleted and we are ready to reassamble.
if r.deleted < len(r.holes) {
return buffer.NewVectorisedView(0, nil), false, consumed
}
res, err := r.heap.reassemble()
if err != nil {
panic(fmt.Sprintf("reassemble failed with: %v. There is probably a bug in the code handling the holes.", err))
}
return res, true, consumed
}
func (r *reassembler) tooOld(timeout time.Duration) bool {
return time.Now().Sub(r.creationTime) > timeout
}
func (r *reassembler) checkDoneOrMark() bool {
r.mu.Lock()
prev := r.done
r.done = true
r.mu.Unlock()
return prev
}
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