mark net.ipv4.tcp_keepalive_time as a safe sysctl

pkg/kubelet/sysctl/safe_sysctls.go

@@ -25,24 +25,33 @@ import (
 	"k8s.io/kubernetes/pkg/proxy/ipvs"
 )
 
-// refer to https://github.com/torvalds/linux/commit/122ff243f5f104194750ecbc76d5946dd1eec934.
-const ipLocalReservedPortsMinNamespacedKernelVersion = "3.16"
-
-var safeSysctls = []string{
-	"kernel.shm_rmid_forced",
-	"net.ipv4.ip_local_port_range",
-	"net.ipv4.tcp_syncookies",
-	"net.ipv4.ping_group_range",
-	"net.ipv4.ip_unprivileged_port_start",
+type sysctl struct {
+	// the name of sysctl
+	name string
+	// the minimum kernel version where the sysctl is available
+	kernel string
 }
 
-var safeSysctlsIncludeReservedPorts = []string{
-	"kernel.shm_rmid_forced",
-	"net.ipv4.ip_local_port_range",
-	"net.ipv4.tcp_syncookies",
-	"net.ipv4.ping_group_range",
-	"net.ipv4.ip_unprivileged_port_start",
-	"net.ipv4.ip_local_reserved_ports",
+var safeSysctls = []sysctl{
+	{
+		name: "kernel.shm_rmid_forced",
+	}, {
+		name: "net.ipv4.ip_local_port_range",
+	}, {
+		name: "net.ipv4.tcp_syncookies",
+	}, {
+		name: "net.ipv4.ping_group_range",
+	}, {
+		name: "net.ipv4.ip_unprivileged_port_start",
+	}, {
+		name: "net.ipv4.ip_local_reserved_ports",
+		// refer to https://github.com/torvalds/linux/commit/122ff243f5f104194750ecbc76d5946dd1eec934.
+		kernel: "3.16",
+	}, {
+		name: "net.ipv4.tcp_keepalive_time",
+		// refer to https://github.com/torvalds/linux/commit/13b287e8d1cad951634389f85b8c9b816bd3bb1e.
+		kernel: "4.5",
+	},
 }
 
 // SafeSysctlAllowlist returns the allowlist of safe sysctls and safe sysctl patterns (ending in *).
@@ -51,19 +60,32 @@ var safeSysctlsIncludeReservedPorts = []string{
 // - it is namespaced in the container or the pod
 // - it is isolated, i.e. has no influence on any other pod on the same node.
 func SafeSysctlAllowlist() []string {
-	if goruntime.GOOS == "linux" {
-		// make sure we're on a new enough kernel that the ip_local_reserved_ports sysctl is namespaced
-		kernelVersion, err := getKernelVersion()
-		if err != nil {
-			klog.ErrorS(err, "Failed to get kernel version, dropping net.ipv4.ip_local_reserved_ports from safe sysctl list")
-			return safeSysctls
+	if goruntime.GOOS != "linux" {
+		return nil
+	}
+	return getSafeSysctlAllowlist(getKernelVersion)
+}
+
+func getSafeSysctlAllowlist(getVersion func() (*version.Version, error)) []string {
+	kernelVersion, err := getVersion()
+	if err != nil {
+		klog.ErrorS(err, "failed to get kernel version, unable to determine which sysctls are available")
+	}
+
+	var safeSysctlAllowlist []string
+	for _, sc := range safeSysctls {
+		if sc.kernel == "" {
+			safeSysctlAllowlist = append(safeSysctlAllowlist, sc.name)
+			continue
 		}
-		if kernelVersion.LessThan(version.MustParseGeneric(ipLocalReservedPortsMinNamespacedKernelVersion)) {
-			klog.ErrorS(nil, "Kernel version is too old, dropping net.ipv4.ip_local_reserved_ports from safe sysctl list", "kernelVersion", kernelVersion)
-			return safeSysctls
+
+		if kernelVersion != nil && kernelVersion.AtLeast(version.MustParseGeneric(sc.kernel)) {
+			safeSysctlAllowlist = append(safeSysctlAllowlist, sc.name)
+		} else {
+			klog.ErrorS(nil, "kernel version is too small, dropping the sysctl from safe sysctl list", "kernelVersion", kernelVersion, "sysctl", sc.name)
 		}
 	}
-	return safeSysctlsIncludeReservedPorts
+	return safeSysctlAllowlist
 }
 
 func getKernelVersion() (*version.Version, error) {
@@ -71,6 +93,7 @@ func getKernelVersion() (*version.Version, error) {
 	if err != nil {
 		return nil, fmt.Errorf("failed to get kernel version: %w", err)
 	}
+
 	kernelVersion, err := version.ParseGeneric(kernelVersionStr)
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse kernel version: %w", err)

pkg/kubelet/sysctl/safe_sysctls_test.go

@@ -0,0 +1,85 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package sysctl
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/util/version"
+)
+
+func Test_getSafeSysctlAllowlist(t *testing.T) {
+	tests := []struct {
+		name       string
+		getVersion func() (*version.Version, error)
+		want       []string
+	}{
+		{
+			name: "failed to get kernelVersion, only return safeSysctls with no kernelVersion limit",
+			getVersion: func() (*version.Version, error) {
+				return nil, fmt.Errorf("fork error")
+			},
+			want: []string{
+				"kernel.shm_rmid_forced",
+				"net.ipv4.ip_local_port_range",
+				"net.ipv4.tcp_syncookies",
+				"net.ipv4.ping_group_range",
+				"net.ipv4.ip_unprivileged_port_start",
+			},
+		},
+		{
+			name: "kernelVersion is 3.18.0, return safeSysctls with no kernelVersion limit and net.ipv4.ip_local_reserved_ports",
+			getVersion: func() (*version.Version, error) {
+				kernelVersionStr := "3.18.0-957.27.2.el7.x86_64"
+				return version.ParseGeneric(kernelVersionStr)
+			},
+			want: []string{
+				"kernel.shm_rmid_forced",
+				"net.ipv4.ip_local_port_range",
+				"net.ipv4.tcp_syncookies",
+				"net.ipv4.ping_group_range",
+				"net.ipv4.ip_unprivileged_port_start",
+				"net.ipv4.ip_local_reserved_ports",
+			},
+		},
+		{
+			name: "kernelVersion is 5.15.0, return safeSysctls with no kernelVersion limit and net.ipv4.ip_local_reserved_ports and net.ipv4.tcp_keepalive_time",
+			getVersion: func() (*version.Version, error) {
+				kernelVersionStr := "5.15.0-75-generic"
+				return version.ParseGeneric(kernelVersionStr)
+			},
+			want: []string{
+				"kernel.shm_rmid_forced",
+				"net.ipv4.ip_local_port_range",
+				"net.ipv4.tcp_syncookies",
+				"net.ipv4.ping_group_range",
+				"net.ipv4.ip_unprivileged_port_start",
+				"net.ipv4.ip_local_reserved_ports",
+				"net.ipv4.tcp_keepalive_time",
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := getSafeSysctlAllowlist(tt.getVersion); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("getSafeSysctlAllowlist() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}