// +build linux

/*
Copyright 2018 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 kubelet

import (
	"fmt"

	"k8s.io/klog"
	utiliptables "k8s.io/kubernetes/pkg/util/iptables"
)

// syncNetworkUtil ensures the network utility are present on host.
// Network util includes:
// 1. 	In nat table, KUBE-MARK-DROP rule to mark connections for dropping
// 	Marked connection will be drop on INPUT/OUTPUT Chain in filter table
// 2. 	In nat table, KUBE-MARK-MASQ rule to mark connections for SNAT
// 	Marked connection will get SNAT on POSTROUTING Chain in nat table
func (kl *Kubelet) syncNetworkUtil() {
	if kl.iptablesMasqueradeBit < 0 || kl.iptablesMasqueradeBit > 31 {
		klog.Errorf("invalid iptables-masquerade-bit %v not in [0, 31]", kl.iptablesMasqueradeBit)
		return
	}

	if kl.iptablesDropBit < 0 || kl.iptablesDropBit > 31 {
		klog.Errorf("invalid iptables-drop-bit %v not in [0, 31]", kl.iptablesDropBit)
		return
	}

	if kl.iptablesDropBit == kl.iptablesMasqueradeBit {
		klog.Errorf("iptables-masquerade-bit %v and iptables-drop-bit %v must be different", kl.iptablesMasqueradeBit, kl.iptablesDropBit)
		return
	}

	// Setup KUBE-MARK-DROP rules
	dropMark := getIPTablesMark(kl.iptablesDropBit)
	if _, err := kl.iptClient.EnsureChain(utiliptables.TableNAT, KubeMarkDropChain); err != nil {
		klog.Errorf("Failed to ensure that %s chain %s exists: %v", utiliptables.TableNAT, KubeMarkDropChain, err)
		return
	}
	if _, err := kl.iptClient.EnsureRule(utiliptables.Append, utiliptables.TableNAT, KubeMarkDropChain, "-j", "MARK", "--set-xmark", dropMark); err != nil {
		klog.Errorf("Failed to ensure marking rule for %v: %v", KubeMarkDropChain, err)
		return
	}
	if _, err := kl.iptClient.EnsureChain(utiliptables.TableFilter, KubeFirewallChain); err != nil {
		klog.Errorf("Failed to ensure that %s chain %s exists: %v", utiliptables.TableFilter, KubeFirewallChain, err)
		return
	}
	if _, err := kl.iptClient.EnsureRule(utiliptables.Append, utiliptables.TableFilter, KubeFirewallChain,
		"-m", "comment", "--comment", "kubernetes firewall for dropping marked packets",
		"-m", "mark", "--mark", dropMark,
		"-j", "DROP"); err != nil {
		klog.Errorf("Failed to ensure rule to drop packet marked by %v in %v chain %v: %v", KubeMarkDropChain, utiliptables.TableFilter, KubeFirewallChain, err)
		return
	}
	if _, err := kl.iptClient.EnsureRule(utiliptables.Prepend, utiliptables.TableFilter, utiliptables.ChainOutput, "-j", string(KubeFirewallChain)); err != nil {
		klog.Errorf("Failed to ensure that %s chain %s jumps to %s: %v", utiliptables.TableFilter, utiliptables.ChainOutput, KubeFirewallChain, err)
		return
	}
	if _, err := kl.iptClient.EnsureRule(utiliptables.Prepend, utiliptables.TableFilter, utiliptables.ChainInput, "-j", string(KubeFirewallChain)); err != nil {
		klog.Errorf("Failed to ensure that %s chain %s jumps to %s: %v", utiliptables.TableFilter, utiliptables.ChainInput, KubeFirewallChain, err)
		return
	}

	// Setup KUBE-MARK-MASQ rules
	masqueradeMark := getIPTablesMark(kl.iptablesMasqueradeBit)
	if _, err := kl.iptClient.EnsureChain(utiliptables.TableNAT, KubeMarkMasqChain); err != nil {
		klog.Errorf("Failed to ensure that %s chain %s exists: %v", utiliptables.TableNAT, KubeMarkMasqChain, err)
		return
	}
	if _, err := kl.iptClient.EnsureChain(utiliptables.TableNAT, KubePostroutingChain); err != nil {
		klog.Errorf("Failed to ensure that %s chain %s exists: %v", utiliptables.TableNAT, KubePostroutingChain, err)
		return
	}
	if _, err := kl.iptClient.EnsureRule(utiliptables.Append, utiliptables.TableNAT, KubeMarkMasqChain, "-j", "MARK", "--set-xmark", masqueradeMark); err != nil {
		klog.Errorf("Failed to ensure marking rule for %v: %v", KubeMarkMasqChain, err)
		return
	}
	if _, err := kl.iptClient.EnsureRule(utiliptables.Prepend, utiliptables.TableNAT, utiliptables.ChainPostrouting,
		"-m", "comment", "--comment", "kubernetes postrouting rules", "-j", string(KubePostroutingChain)); err != nil {
		klog.Errorf("Failed to ensure that %s chain %s jumps to %s: %v", utiliptables.TableNAT, utiliptables.ChainPostrouting, KubePostroutingChain, err)
		return
	}
	if _, err := kl.iptClient.EnsureRule(utiliptables.Append, utiliptables.TableNAT, KubePostroutingChain,
		"-m", "comment", "--comment", "kubernetes service traffic requiring SNAT",
		"-m", "mark", "--mark", masqueradeMark, "-j", "MASQUERADE"); err != nil {
		klog.Errorf("Failed to ensure SNAT rule for packets marked by %v in %v chain %v: %v", KubeMarkMasqChain, utiliptables.TableNAT, KubePostroutingChain, err)
		return
	}
}

// getIPTablesMark returns the fwmark given the bit
func getIPTablesMark(bit int) string {
	value := 1 << uint(bit)
	return fmt.Sprintf("%#08x/%#08x", value, value)
}
