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Update minimum RTT for RACK.

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We are currently tracking the minimum RTT for RACK as smoothed RTT. As per RFC
minimum RTT can be a global minimum of all RTTs or filtered value of recent
RTT measurements. In this cl minimum RTT is updated to global minimum of all
RTTs for the connection.

PiperOrigin-RevId: 335061518
This commit is contained in:
Nayana Bidari
2020-10-02 11:09:35 -07:00
committed by gVisor bot
parent 02cff90ad9
commit d23f1ec0fa
2 changed files with 15 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/tcpip/transport/tcp/rack.go
+14 -2
View File
@@ -39,6 +39,9 @@ type rackControl struct {
// sequence.
fack seqnum.Value
// minRTT is the estimated minimum RTT of the connection.
minRTT time.Duration
// rtt is the RTT of the most recently delivered packet on the
// connection (either cumulatively acknowledged or selectively
// acknowledged) that was not marked invalid as a possible spurious
@@ -48,7 +51,7 @@ type rackControl struct {
// Update will update the RACK related fields when an ACK has been received.
// See: https://tools.ietf.org/html/draft-ietf-tcpm-rack-08#section-7.2
func (rc *rackControl) Update(seg *segment, ackSeg *segment, srtt time.Duration, offset uint32) {
func (rc *rackControl) Update(seg *segment, ackSeg *segment, offset uint32) {
rtt := time.Now().Sub(seg.xmitTime)
// If the ACK is for a retransmitted packet, do not update if it is a
@@ -65,12 +68,21 @@ func (rc *rackControl) Update(seg *segment, ackSeg *segment, srtt time.Duration,
return
}
}
if rtt < srtt {
if rtt < rc.minRTT {
return
}
}
rc.rtt = rtt
// The sender can either track a simple global minimum of all RTT
// measurements from the connection, or a windowed min-filtered value
// of recent RTT measurements. This implementation keeps track of the
// simple global minimum of all RTTs for the connection.
if rtt < rc.minRTT || rc.minRTT == 0 {
rc.minRTT = rtt
}
// Update rc.xmitTime and rc.endSequence to the transmit time and
// ending sequence number of the packet which has been acknowledged
// most recently.
pkg/tcpip/transport/tcp/snd.go
+1 -4
View File
@@ -1365,9 +1365,6 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
ackLeft := acked
originalOutstanding := s.outstanding
s.rtt.Lock()
srtt := s.rtt.srtt
s.rtt.Unlock()
for ackLeft > 0 {
// We use logicalLen here because we can have FIN
// segments (which are always at the end of list) that
@@ -1389,7 +1386,7 @@ func (s *sender) handleRcvdSegment(rcvdSeg *segment) {
// Update the RACK fields if SACK is enabled.
if s.ep.sackPermitted {
s.rc.Update(seg, rcvdSeg, srtt, s.ep.tsOffset)
s.rc.Update(seg, rcvdSeg, s.ep.tsOffset)
}
s.writeList.Remove(seg)