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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 fragmentation
import (
"container/heap"
"fmt"
"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
)
type fragment struct {
offset uint16
vv buffer.VectorisedView
}
type fragHeap []fragment
func (h *fragHeap) Len() int {
return len(*h)
}
func (h *fragHeap) Less(i, j int) bool {
return (*h)[i].offset < (*h)[j].offset
}
func (h *fragHeap) Swap(i, j int) {
(*h)[i], (*h)[j] = (*h)[j], (*h)[i]
}
func (h *fragHeap) Push(x interface{}) {
*h = append(*h, x.(fragment))
}
func (h *fragHeap) Pop() interface{} {
old := *h
n := len(old)
x := old[n-1]
*h = old[:n-1]
return x
}
// reassamble empties the heap and returns a VectorisedView
// containing a reassambled version of the fragments inside the heap.
func (h *fragHeap) reassemble() (buffer.VectorisedView, error) {
curr := heap.Pop(h).(fragment)
views := curr.vv.Views()
size := curr.vv.Size()
if curr.offset != 0 {
return buffer.VectorisedView{}, fmt.Errorf("offset of the first packet is != 0 (%d)", curr.offset)
}
for h.Len() > 0 {
curr := heap.Pop(h).(fragment)
if int(curr.offset) < size {
curr.vv.TrimFront(size - int(curr.offset))
} else if int(curr.offset) > size {
return buffer.VectorisedView{}, fmt.Errorf("packet has a hole, expected offset %d, got %d", size, curr.offset)
}
size += curr.vv.Size()
views = append(views, curr.vv.Views()...)
}
return buffer.NewVectorisedView(size, views), nil
}
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