From bbb8f3b0d9416be54b694529d74e809a34190c7c Mon Sep 17 00:00:00 2001
From: Anupam Ghosh <iamanupamghosh@gmail.com>
Date: Sun, 3 Aug 2025 13:52:25 +0530
Subject: [PATCH] disable sloppy_tcp if there is no DSR & Maglev service

---
 pkg/controllers/proxy/service_endpoints_sync.go | 15 ++++++++-------
 pkg/utils/node.go                               |  2 ++
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/pkg/controllers/proxy/service_endpoints_sync.go b/pkg/controllers/proxy/service_endpoints_sync.go
index eba13f59..12425caa 100644
--- a/pkg/controllers/proxy/service_endpoints_sync.go
+++ b/pkg/controllers/proxy/service_endpoints_sync.go
@@ -406,23 +406,24 @@ func (nsc *NetworkServicesController) setupExternalIPServices(serviceInfoMap ser
 }
 
 func (nsc *NetworkServicesController) setupSloppyTCP(serviceInfoMap serviceInfoMap) {
-	enableSloppyTCP := false
+	var sloppyTCPVal int8 = 0
 	for _, svc := range serviceInfoMap {
 		// Enable sloppy TCP if any DSR service with Maglev hashing is configured
 		if svc.directServerReturn && svc.scheduler == IpvsMaglevHashing {
-			enableSloppyTCP = true
+			sloppyTCPVal = 1
+			break
 		}
 	}
 
-	// set sloppy_tcp to 1 if not already set
+	// enable/disable sloppy_tcp sysctl based on sloppyTCPVal
 	sloppyTCP := nsc.krNode.SloppyTCP()
-	if enableSloppyTCP && sloppyTCP.CachedVal() == 0 {
-		sysctlErr := sloppyTCP.WriteVal(1)
+	if sloppyTCP.CachedVal() != sloppyTCPVal {
+		sysctlErr := sloppyTCP.WriteVal(sloppyTCPVal)
 		if sysctlErr != nil {
 			klog.Errorf("Failed to enable IPVS sloppy TCP: %s", sysctlErr.Error())
-		} else {
-			klog.Infof("IPVS sloppy TCP enabled")
+			return
 		}
+		klog.Infof("IPVS sloppy TCP set to %d", sloppyTCPVal)
 	}
 }
 
diff --git a/pkg/utils/node.go b/pkg/utils/node.go
index 45c0cd65..d9a3bf3b 100644
--- a/pkg/utils/node.go
+++ b/pkg/utils/node.go
@@ -251,6 +251,8 @@ func NewKRNode(node *apiv1.Node, linkQ LocalLinkQuerier, enableIPv4, enableIPv6
 		},
 		linkQ:             linkQ,
 		NodeInterfaceName: nodeInterfaceName,
+		// Purposefully set the value of sloppyTCP to 0. This ensures the machine's sloppy_tcp setting remains
+		// unchanged when there are no services with both Maglev and DSR enabled.
 		sloppyTCP: SysctlConfig{
 			name:  IPv4IPVSSloppyTCP,
 			value: 0,