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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"
"math"
"gvisor.dev/gvisor/pkg/sync"
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/buffer"
)
type hole struct {
first uint16
last uint16
deleted bool
}
type reassembler struct {
reassemblerEntry
id FragmentID
size int
proto uint8
mu sync.Mutex
holes []hole
deleted int
heap fragHeap
done bool
creationTime int64
}
func newReassembler(id FragmentID, clock tcpip.Clock) *reassembler {
r := &reassembler{
id: id,
holes: make([]hole, 0, 16),
heap: make(fragHeap, 0, 8),
creationTime: clock.NowMonotonic(),
}
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, proto uint8, vv buffer.VectorisedView) (buffer.VectorisedView, uint8, bool, int, error) {
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.VectorisedView{}, 0, false, consumed, nil
}
// For IPv6, it is possible to have different Protocol values between
// fragments of a packet (because, unlike IPv4, the Protocol is not used to
// identify a fragment). In this case, only the Protocol of the first
// fragment must be used as per RFC 8200 Section 4.5.
//
// TODO(gvisor.dev/issue/3648): The entire first IP header should be recorded
// here (instead of just the protocol) because most IP options should be
// derived from the first fragment.
if first == 0 {
r.proto = proto
}
if r.updateHoles(first, last, more) {
// We store the incoming packet only if it filled some holes.
heap.Push(&r.heap, fragment{offset: first, vv: vv.Clone(nil)})
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.VectorisedView{}, 0, false, consumed, nil
}
res, err := r.heap.reassemble()
if err != nil {
return buffer.VectorisedView{}, 0, false, consumed, fmt.Errorf("fragment reassembly failed: %w", err)
}
return res, r.proto, true, consumed, nil
}
func (r *reassembler) checkDoneOrMark() bool {
r.mu.Lock()
prev := r.done
r.done = true
r.mu.Unlock()
return prev
}
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