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RACK: Create a new list for segments. 

RACK requires the segments to be in the order of their transmission
or retransmission times. This cl creates a new list and moves the
retransmitted segments to the end of the list.

PiperOrigin-RevId: 327325153
This commit is contained in:
Nayana Bidari 2020-08-18 15:57:48 -07:00 committed by gVisor bot
parent 6405525b04
commit 4184a7d5f1
5 changed files with 72 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
pkg/tcpip/transport/tcp/BUILD
View File

@ -11,7 +11,8 @@ go_template_instance(
template = "//pkg/ilist:generic_list",
types = {
"Element": "*segment",
"Linker": "*segment",
"ElementMapper": "segmentMapper",
"Linker": "*segmentEntry",
},
)
@ -27,6 +28,19 @@ go_template_instance(
},
)
go_template_instance(
name = "tcp_rack_segment_list",
out = "tcp_rack_segment_list.go",
package = "tcp",
prefix = "rackSegment",
template = "//pkg/ilist:generic_list",
types = {
"Element": "*segment",
"ElementMapper": "rackSegmentMapper",
"Linker": "*rackSegmentEntry",
},
)
go_library(
name = "tcp",
srcs = [
@ -55,6 +69,7 @@ go_library(
"snd.go",
"snd_state.go",
"tcp_endpoint_list.go",
"tcp_rack_segment_list.go",
"tcp_segment_list.go",
"timer.go",
],

11
pkg/tcpip/transport/tcp/connect.go
View File

@ -924,7 +924,18 @@ func (e *endpoint) handleWrite() *tcpip.Error {
first := e.sndQueue.Front()
if first != nil {
lastSeg := e.snd.writeList.Back()
e.snd.writeList.PushBackList(&e.sndQueue)
if lastSeg == nil {
lastSeg = e.snd.writeList.Front()
} else {
lastSeg = lastSeg.segEntry.Next()
}
// Add new segments to rcList, as rcList and writeList should
// be consistent.
for seg := lastSeg; seg != nil; seg = seg.segEntry.Next() {
e.snd.rcList.PushBack(seg)
}
e.sndBufInQueue = 0
}

4
pkg/tcpip/transport/tcp/endpoint.go
View File

@ -1428,7 +1428,7 @@ func (e *endpoint) Peek(vec [][]byte) (int64, tcpip.ControlMessages, *tcpip.Erro
vec = append([][]byte(nil), vec...)
var num int64
for s := e.rcvList.Front(); s != nil; s = s.Next() {
for s := e.rcvList.Front(); s != nil; s = s.segEntry.Next() {
views := s.data.Views()
for i := s.viewToDeliver; i < len(views); i++ {
@ -2249,7 +2249,7 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc
if !handshake {
e.segmentQueue.mu.Lock()
for _, l := range []segmentList{e.segmentQueue.list, e.sndQueue, e.snd.writeList} {
for s := l.Front(); s != nil; s = s.Next() {
for s := l.Front(); s != nil; s = s.segEntry.Next() {
s.id = e.ID
s.route = r.Clone()
e.sndWaker.Assert()

23
pkg/tcpip/transport/tcp/segment.go
View File

@ -30,12 +30,13 @@ import (
//
// +stateify savable
type segment struct {
segmentEntry
refCnt int32
id stack.TransportEndpointID `state:"manual"`
route stack.Route `state:"manual"`
data buffer.VectorisedView `state:".(buffer.VectorisedView)"`
hdr header.TCP
segEntry segmentEntry
rackSegEntry rackSegmentEntry
refCnt int32
id stack.TransportEndpointID `state:"manual"`
route stack.Route `state:"manual"`
data buffer.VectorisedView `state:".(buffer.VectorisedView)"`
hdr header.TCP
// views is used as buffer for data when its length is large
// enough to store a VectorisedView.
views [8]buffer.View `state:"nosave"`
@ -61,6 +62,16 @@ type segment struct {
xmitCount uint32
}
// segmentMapper is the ElementMapper for the writeList.
type segmentMapper struct{}
func (segmentMapper) linkerFor(seg *segment) *segmentEntry { return &seg.segEntry }
// rackSegmentMapper is the ElementMapper for the rcList.
type rackSegmentMapper struct{}
func (rackSegmentMapper) linkerFor(seg *segment) *rackSegmentEntry { return &seg.rackSegEntry }
func newSegment(r *stack.Route, id stack.TransportEndpointID, pkt *stack.PacketBuffer) *segment {
s := &segment{
refCnt: 1,

41
pkg/tcpip/transport/tcp/snd.go
View File

@ -154,6 +154,7 @@ type sender struct {
closed bool
writeNext *segment
writeList segmentList
rcList rackSegmentList
resendTimer timer `state:"nosave"`
resendWaker sleep.Waker `state:"nosave"`
@ -367,7 +368,7 @@ func (s *sender) updateMaxPayloadSize(mtu, count int) {
// Rewind writeNext to the first segment exceeding the MTU. Do nothing
// if it is already before such a packet.
for seg := s.writeList.Front(); seg != nil; seg = seg.Next() {
for seg := s.writeList.Front(); seg != nil; seg = seg.segEntry.Next() {
if seg == s.writeNext {
// We got to writeNext before we could find a segment
// exceeding the MTU.
@ -622,6 +623,7 @@ func (s *sender) splitSeg(seg *segment, size int) {
nSeg.data.TrimFront(size)
nSeg.sequenceNumber.UpdateForward(seqnum.Size(size))
s.writeList.InsertAfter(seg, nSeg)
s.rcList.InsertAfter(seg, nSeg)
// The segment being split does not carry PUSH flag because it is
// followed by the newly split segment.
@ -653,7 +655,7 @@ func (s *sender) NextSeg(nextSegHint *segment) (nextSeg, hint *segment, rescueRt
var s3 *segment
var s4 *segment
// Step 1.
for seg := nextSegHint; seg != nil; seg = seg.Next() {
for seg := nextSegHint; seg != nil; seg = seg.segEntry.Next() {
// Stop iteration if we hit a segment that has never been
// transmitted (i.e. either it has no assigned sequence number
// or if it does have one, it's >= the next sequence number
@ -683,7 +685,7 @@ func (s *sender) NextSeg(nextSegHint *segment) (nextSeg, hint *segment, rescueRt
// NextSeg():
// (1.c) IsLost(S2) returns true.
if s.ep.scoreboard.IsLost(segSeq) {
return seg, seg.Next(), false
return seg, seg.segEntry.Next(), false
}
// NextSeg():
@ -697,7 +699,7 @@ func (s *sender) NextSeg(nextSegHint *segment) (nextSeg, hint *segment, rescueRt
// SHOULD be returned.
if s3 == nil {
s3 = seg
hint = seg.Next()
hint = seg.segEntry.Next()
}
}
// NextSeg():
@ -731,7 +733,7 @@ func (s *sender) NextSeg(nextSegHint *segment) (nextSeg, hint *segment, rescueRt
// range of one segment of up to SMSS octets of
// previously unsent data starting with sequence number
// HighData+1 MUST be returned."
for seg := s.writeNext; seg != nil; seg = seg.Next() {
for seg := s.writeNext; seg != nil; seg = seg.segEntry.Next() {
if s.isAssignedSequenceNumber(seg) && seg.sequenceNumber.LessThan(s.sndNxt) {
continue
}
@ -773,15 +775,16 @@ func (s *sender) maybeSendSegment(seg *segment, limit int, end seqnum.Value) (se
// triggering bugs in poorly written DNS
// implementations.
var nextTooBig bool
for seg.Next() != nil && seg.Next().data.Size() != 0 {
if seg.data.Size()+seg.Next().data.Size() > available {
for seg.segEntry.Next() != nil && seg.segEntry.Next().data.Size() != 0 {
if seg.data.Size()+seg.segEntry.Next().data.Size() > available {
nextTooBig = true
break
}
seg.data.Append(seg.Next().data)
seg.data.Append(seg.segEntry.Next().data)
// Consume the segment that we just merged in.
s.writeList.Remove(seg.Next())
s.writeList.Remove(seg.segEntry.Next())
s.rcList.Remove(seg.rackSegEntry.Next())
}
if !nextTooBig && seg.data.Size() < available {
// Segment is not full.
@ -948,7 +951,7 @@ func (s *sender) handleSACKRecovery(limit int, end seqnum.Value) (dataSent bool)
}
dataSent = true
s.outstanding++
s.writeNext = nextSeg.Next()
s.writeNext = nextSeg.segEntry.Next()
continue
}
@ -961,6 +964,7 @@ func (s *sender) handleSACKRecovery(limit int, end seqnum.Value) (dataSent bool)
// transmitted in (C.1)."
s.outstanding++
dataSent = true
s.sendSegment(nextSeg)
segEnd := nextSeg.sequenceNumber.Add(nextSeg.logicalLen())
@ -1035,7 +1039,7 @@ func (s *sender) sendData() {
if s.fr.active && s.ep.sackPermitted {
dataSent = s.handleSACKRecovery(s.maxPayloadSize, end)
} else {
for seg := s.writeNext; seg != nil && s.outstanding < s.sndCwnd; seg = seg.Next() {
for seg := s.writeNext; seg != nil && s.outstanding < s.sndCwnd; seg = seg.segEntry.Next() {
cwndLimit := (s.sndCwnd - s.outstanding) * s.maxPayloadSize
if cwndLimit < limit {
limit = cwndLimit
@ -1043,7 +1047,7 @@ func (s *sender) sendData() {
if s.isAssignedSequenceNumber(seg) && s.ep.sackPermitted && s.ep.scoreboard.IsSACKED(seg.sackBlock()) {
// Move writeNext along so that we don't try and scan data that
// has already been SACKED.
s.writeNext = seg.Next()
s.writeNext = seg.segEntry.Next()
continue
}
if sent := s.maybeSendSegment(seg, limit, end); !sent {
@ -1051,7 +1055,7 @@ func (s *sender) sendData() {
}
dataSent = true
s.outstanding += s.pCount(seg)
s.writeNext = seg.Next()
s.writeNext = seg.segEntry.Next()
}
}
@ -1182,7 +1186,7 @@ func (s *sender) SetPipe() {
}
pipe := 0
smss := seqnum.Size(s.ep.scoreboard.SMSS())
for s1 := s.writeList.Front(); s1 != nil && s1.data.Size() != 0 && s.isAssignedSequenceNumber(s1); s1 = s1.Next() {
for s1 := s.writeList.Front(); s1 != nil && s1.data.Size() != 0 && s.isAssignedSequenceNumber(s1); s1 = s1.segEntry.Next() {
// With GSO each segment can be much larger than SMSS. So check the segment
// in SMSS sized ranges.
segEnd := s1.sequenceNumber.Add(seqnum.Size(s1.data.Size()))
@ -1384,7 +1388,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
}
if s.writeNext == seg {
s.writeNext = seg.Next()
s.writeNext = seg.segEntry.Next()
}
// Update the RACK fields if SACK is enabled.
@ -1393,6 +1397,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
}
s.writeList.Remove(seg)
s.rcList.Remove(seg)
// if SACK is enabled then Only reduce outstanding if
// the segment was not previously SACKED as these have
@ -1460,6 +1465,12 @@ func (s *sender) sendSegment(seg *segment) *tcpip.Error {
if s.sndCwnd < s.sndSsthresh {
s.ep.stack.Stats().TCP.SlowStartRetransmits.Increment()
}
// Move the segment which has to be retransmitted to the end of the list, as
// RACK requires the segments in the order of their transmission times.
// See: https://tools.ietf.org/html/draft-ietf-tcpm-rack-09#section-6.2
// Step 5
s.rcList.PushBack(seg)
}
seg.xmitTime = time.Now()
seg.xmitCount++