set conntrack max and hashsize on startup

main.go

@@ -33,6 +33,7 @@ import (
 
 	firewallv1 "github.com/metal-stack/firewall-controller/api/v1"
 	"github.com/metal-stack/firewall-controller/controllers"
+	"github.com/metal-stack/firewall-controller/pkg/sysctl"
 	"github.com/metal-stack/firewall-controller/pkg/updater"
 	// +kubebuilder:scaffold:imports
 )
@@ -298,6 +299,11 @@ func main() {
 		}
 	}()
 
+	err = sysctl.Tune(l)
+	if err != nil {
+		l.Errorw("unable to tune kernel", "error", err)
+	}
+
 	if err := seedMgr.Start(ctx); err != nil {
 		l.Errorw("problem running seed controller", "error", err)
 		panic(err)

pkg/sysctl/sysctl.go

@@ -0,0 +1,95 @@
+package sysctl
+
+import (
+	"fmt"
+	"os"
+	"path"
+	"strconv"
+	"strings"
+
+	"go.uber.org/zap"
+)
+
+const (
+	// sysctlBase is the root directory for sysctl values in the proc filesystem
+	sysctlBase = "/proc/sys"
+	// nfConntrackMax defines how many connection track entries can be active at the same time
+	nfConntrackMax = Sysctl("/net/netfilter/nf_conntrack_max")
+	// nfConntrackMaxSetting defines the maximum settable
+	nfConntrackMaxSetting = 4194304
+
+	// moduleBase is the root directory for module specific settings
+	moduleBase = "/sys/module"
+	// nfConntrackHashSize defines the hashsize of the conntrack module
+	nfConntrackHashSize = Module("/nf_conntrack/parameters/hashsize")
+	// nfConntrackHashSizeSetting defines the maximum settable
+	nfConntrackHashSizeSetting = 4194304
+)
+
+type (
+	Sysctl string
+	Module string
+)
+
+func Tune(log *zap.SugaredLogger) error {
+	log.Infow("set sysctl value", "key", nfConntrackMax, "value", nfConntrackMaxSetting)
+	err := Set(nfConntrackMax, nfConntrackMaxSetting)
+	if err != nil {
+		return fmt.Errorf("unable to set value of %q %w", nfConntrackMax, err)
+	}
+
+	conntrackMax, err := Get(nfConntrackMax)
+	if err != nil {
+		return fmt.Errorf("unable to get value of %q %w", nfConntrackMax, err)
+	}
+
+	log.Infow("set module value", "key", nfConntrackHashSize, "value", nfConntrackHashSizeSetting)
+	err = SetModule(nfConntrackHashSize, nfConntrackHashSizeSetting)
+	if err != nil {
+		return fmt.Errorf("unable to set module parameter %w", err)
+	}
+
+	hashSize, err := GetModule(nfConntrackHashSize)
+	if err != nil {
+		return fmt.Errorf("unable to get value of %q %w", nfConntrackMax, err)
+	}
+
+	log.Infow("sysctl and module parameters set", "conntrack max", conntrackMax, "hash size", hashSize)
+	return nil
+}
+
+// Get returns the value for the specified sysctl setting
+func Get(sysctl Sysctl) (int, error) {
+	data, err := os.ReadFile(path.Join(sysctlBase, string(sysctl)))
+	if err != nil {
+		return -1, err
+	}
+	val, err := strconv.Atoi(strings.Trim(string(data), " \n"))
+	if err != nil {
+		return -1, err
+	}
+	return val, nil
+}
+
+// Set modifies the specified sysctl flag to the new value
+func Set(sysctl Sysctl, newVal int) error {
+	return os.WriteFile(path.Join(sysctlBase, string(sysctl)), []byte(strconv.Itoa(newVal)), 0600)
+}
+
+// GetModule returns the value for the specified Module setting
+func GetModule(module Module) (int, error) {
+	data, err := os.ReadFile(path.Join(moduleBase, string(module)))
+	if err != nil {
+		return -1, err
+	}
+	val, err := strconv.Atoi(strings.Trim(string(data), " \n"))
+	if err != nil {
+		return -1, err
+	}
+	return val, nil
+}
+
+// SetModule modifies the specified module flag to the new value
+func SetModule(module Module, newVal int) error {
+	return os.WriteFile(path.Join(moduleBase, string(module)), []byte(strconv.Itoa(newVal)), 0600)
+}