Reduce flakiness in tcp_test.

Tests now use a MinRTO of 3s instead of default 200ms. This reduced flakiness in
a lot of the congestion control/recovery tests which were flaky due to
retransmit timer firing too early in case the test executors were overloaded.

This change also bumps some of the timeouts in tests which were too sensitive to
timer variations and reduces the number of slow start iterations which can
make the tests run for too long and also trigger retansmit timeouts etc if
the executor is overloaded.

PiperOrigin-RevId: 306562645

1 files changed, 13 insertions, 2 deletions

diff --git a/pkg/tcpip/transport/tcp/snd.go b/pkg/tcpip/transport/tcp/snd.go
index 6b7bac37d..d8cfe3115 100644
--- a/pkg/tcpip/transport/tcp/snd.go
+++ b/pkg/tcpip/transport/tcp/snd.go
@@ -15,6 +15,7 @@
 package tcp
 
 import (
+	"fmt"
 	"math"
 	"sync/atomic"
 	"time"
@@ -149,6 +150,9 @@ type sender struct {
 	rtt rtt
 	rto time.Duration
 
+	// minRTO is the minimum permitted value for sender.rto.
+	minRTO time.Duration
+
 	// maxPayloadSize is the maximum size of the payload of a given segment.
 	// It is initialized on demand.
 	maxPayloadSize int
@@ -260,6 +264,13 @@ func newSender(ep *endpoint, iss, irs seqnum.Value, sndWnd seqnum.Size, mss uint
 	// etc.
 	s.ep.scoreboard = NewSACKScoreboard(uint16(s.maxPayloadSize), iss)
 
+	// Get Stack wide minRTO.
+	var v tcpip.TCPMinRTOOption
+	if err := ep.stack.TransportProtocolOption(ProtocolNumber, &v); err != nil {
+		panic(fmt.Sprintf("unable to get minRTO from stack: %s", err))
+	}
+	s.minRTO = time.Duration(v)
+
 	return s
 }
 
@@ -394,8 +405,8 @@ func (s *sender) updateRTO(rtt time.Duration) {
 
 	s.rto = s.rtt.srtt + 4*s.rtt.rttvar
 	s.rtt.Unlock()
-	if s.rto < MinRTO {
-		s.rto = MinRTO
+	if s.rto < s.minRTO {
+		s.rto = s.minRTO
 	}
 }