From 3f5de373a73eea3c881278729fd26e91c5c372da Mon Sep 17 00:00:00 2001
From: Benny Daon <benny@tuzig.com>
Date: Tue, 27 Feb 2024 14:05:24 +0200
Subject: [PATCH] Add RTOMax settings

allowing the user to cap the retranmission timeout, this change adds
RTOMax to SettingEngine and pass it on when creating an sctp Client
---
 sctptransport.go      | 5 ++++-
 settingengine.go      | 7 +++++++
 settingengine_test.go | 9 +++++++++
 3 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/sctptransport.go b/sctptransport.go
index c7e0c9bfa8a..43f7f4d842f 100644
--- a/sctptransport.go
+++ b/sctptransport.go
@@ -58,6 +58,8 @@ type SCTPTransport struct {
 
 	api *API
 	log logging.LeveledLogger
+	// maximum retransmission timeout
+	rtoMax float64
 }
 
 // NewSCTPTransport creates a new SCTPTransport.
@@ -105,11 +107,12 @@ func (r *SCTPTransport) Start(SCTPCapabilities) error {
 	if dtlsTransport == nil || dtlsTransport.conn == nil {
 		return errSCTPTransportDTLS
 	}
-
+	rtoMax := float64(r.api.settingEngine.sctp.rtoMax) / float64(time.Millisecond)
 	sctpAssociation, err := sctp.Client(sctp.Config{
 		NetConn:              dtlsTransport.conn,
 		MaxReceiveBufferSize: r.api.settingEngine.sctp.maxReceiveBufferSize,
 		LoggerFactory:        r.api.settingEngine.LoggerFactory,
+		RTOMax:               rtoMax,
 	})
 	if err != nil {
 		return err
diff --git a/settingengine.go b/settingengine.go
index a9eb1036419..37d47a1cc90 100644
--- a/settingengine.go
+++ b/settingengine.go
@@ -76,6 +76,7 @@ type SettingEngine struct {
 	}
 	sctp struct {
 		maxReceiveBufferSize uint32
+		rtoMax               time.Duration
 	}
 	sdpMediaLevelFingerprints                 bool
 	answeringDTLSRole                         DTLSRole
@@ -441,3 +442,9 @@ func (e *SettingEngine) SetSCTPMaxReceiveBufferSize(maxReceiveBufferSize uint32)
 func (e *SettingEngine) SetDTLSCustomerCipherSuites(customCipherSuites func() []dtls.CipherSuite) {
 	e.dtls.customCipherSuites = customCipherSuites
 }
+
+// SetSCTPRTOMax sets the maximum retransmission timeout.
+// Leave this 0 for the default timeout.
+func (e *SettingEngine) SetSCTPRTOMax(rtoMax time.Duration) {
+	e.sctp.rtoMax = rtoMax
+}
diff --git a/settingengine_test.go b/settingengine_test.go
index 5ad70bda9a3..df88243bbb4 100644
--- a/settingengine_test.go
+++ b/settingengine_test.go
@@ -269,3 +269,12 @@ func TestSetSCTPMaxReceiverBufferSize(t *testing.T) {
 	s.SetSCTPMaxReceiveBufferSize(expSize)
 	assert.Equal(t, expSize, s.sctp.maxReceiveBufferSize)
 }
+
+func TestSetSCTPRTOMax(t *testing.T) {
+	s := SettingEngine{}
+	assert.Equal(t, time.Duration(0), s.sctp.rtoMax)
+
+	expSize := time.Second
+	s.SetSCTPRTOMax(expSize)
+	assert.Equal(t, expSize, s.sctp.rtoMax)
+}