// Apache License v2.0 (copyright Cloud Native Labs & Rancher Labs)
// - modified from https://github.com/cloudnativelabs/kube-router/blob/ee9f6d890d10609284098229fa1e283ab5d83b93/pkg/controllers/netpol/pod.go

// +build !windows

package netpol

import (
	"crypto/sha256"
	"encoding/base32"
	"fmt"
	"strings"

	"github.com/coreos/go-iptables/iptables"
	api "k8s.io/api/core/v1"
	"k8s.io/client-go/tools/cache"
	glog "k8s.io/klog"
)

func (npc *NetworkPolicyController) newPodEventHandler() cache.ResourceEventHandler {
	return cache.ResourceEventHandlerFuncs{
		AddFunc: func(obj interface{}) {
			npc.OnPodUpdate(obj)

		},
		UpdateFunc: func(oldObj, newObj interface{}) {
			newPoObj := newObj.(*api.Pod)
			oldPoObj := oldObj.(*api.Pod)
			if newPoObj.Status.Phase != oldPoObj.Status.Phase || newPoObj.Status.PodIP != oldPoObj.Status.PodIP {
				// for the network policies, we are only interested in pod status phase change or IP change
				npc.OnPodUpdate(newObj)
			}
		},
		DeleteFunc: func(obj interface{}) {
			npc.handlePodDelete(obj)
		},
	}
}

// OnPodUpdate handles updates to pods from the Kubernetes api server
func (npc *NetworkPolicyController) OnPodUpdate(obj interface{}) {
	pod := obj.(*api.Pod)
	glog.V(2).Infof("Received update to pod: %s/%s", pod.Namespace, pod.Name)

	npc.RequestFullSync()
}

func (npc *NetworkPolicyController) handlePodDelete(obj interface{}) {
	pod, ok := obj.(*api.Pod)
	if !ok {
		tombstone, ok := obj.(cache.DeletedFinalStateUnknown)
		if !ok {
			glog.Errorf("unexpected object type: %v", obj)
			return
		}
		if pod, ok = tombstone.Obj.(*api.Pod); !ok {
			glog.Errorf("unexpected object type: %v", obj)
			return
		}
	}
	glog.V(2).Infof("Received pod: %s/%s delete event", pod.Namespace, pod.Name)

	npc.RequestFullSync()
}

func (npc *NetworkPolicyController) syncPodFirewallChains(networkPoliciesInfo []networkPolicyInfo, version string) (map[string]bool, error) {

	activePodFwChains := make(map[string]bool)

	iptablesCmdHandler, err := iptables.New()
	if err != nil {
		glog.Fatalf("Failed to initialize iptables executor: %s", err.Error())
	}

	dropUnmarkedTrafficRules := func(podName, podNamespace, podFwChainName string) error {
		// add rule to log the packets that will be dropped due to network policy enforcement
		comment := "rule to log dropped traffic POD name:" + podName + " namespace: " + podNamespace
		args := []string{"-m", "comment", "--comment", comment, "-m", "mark", "!", "--mark", "0x10000/0x10000", "-j", "NFLOG", "--nflog-group", "100", "-m", "limit", "--limit", "10/minute", "--limit-burst", "10"}
		err = iptablesCmdHandler.AppendUnique("filter", podFwChainName, args...)
		if err != nil {
			return fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}

		// add rule to DROP if no applicable network policy permits the traffic
		comment = "rule to REJECT traffic destined for POD name:" + podName + " namespace: " + podNamespace
		args = []string{"-m", "comment", "--comment", comment, "-m", "mark", "!", "--mark", "0x10000/0x10000", "-j", "REJECT"}
		err = iptablesCmdHandler.AppendUnique("filter", podFwChainName, args...)
		if err != nil {
			return fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}

		// reset mark to let traffic pass through rest of the chains
		args = []string{"-j", "MARK", "--set-mark", "0/0x10000"}
		err = iptablesCmdHandler.AppendUnique("filter", podFwChainName, args...)
		if err != nil {
			return fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}

		return nil
	}

	// loop through the pods running on the node which to which ingress network policies to be applied
	ingressNetworkPolicyEnabledPods, err := npc.getIngressNetworkPolicyEnabledPods(networkPoliciesInfo, npc.nodeIP.String())
	if err != nil {
		return nil, err
	}
	for _, pod := range *ingressNetworkPolicyEnabledPods {

		// below condition occurs when we get trasient update while removing or adding pod
		// subsequent update will do the correct action
		if len(pod.ip) == 0 || pod.ip == "" {
			continue
		}

		// ensure pod specific firewall chain exist for all the pods that need ingress firewall
		podFwChainName := podFirewallChainName(pod.namespace, pod.name, version)
		err = iptablesCmdHandler.NewChain("filter", podFwChainName)
		if err != nil && err.(*iptables.Error).ExitStatus() != 1 {
			return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}
		activePodFwChains[podFwChainName] = true

		// add entries in pod firewall to run through required network policies
		for _, policy := range networkPoliciesInfo {
			if _, ok := policy.targetPods[pod.ip]; ok {
				comment := "run through nw policy " + policy.name
				policyChainName := networkPolicyChainName(policy.namespace, policy.name, version)
				args := []string{"-m", "comment", "--comment", comment, "-j", policyChainName}
				exists, err := iptablesCmdHandler.Exists("filter", podFwChainName, args...)
				if err != nil {
					return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
				}
				if !exists {
					err := iptablesCmdHandler.Insert("filter", podFwChainName, 1, args...)
					if err != nil && err.(*iptables.Error).ExitStatus() != 1 {
						return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
					}
				}
			}
		}

		comment := "rule to permit the traffic traffic to pods when source is the pod's local node"
		args := []string{"-m", "comment", "--comment", comment, "-m", "addrtype", "--src-type", "LOCAL", "-d", pod.ip, "-j", "ACCEPT"}
		exists, err := iptablesCmdHandler.Exists("filter", podFwChainName, args...)
		if err != nil {
			return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}
		if !exists {
			err := iptablesCmdHandler.Insert("filter", podFwChainName, 1, args...)
			if err != nil {
				return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
			}
		}

		// ensure statefull firewall, that permits return traffic for the traffic originated by the pod
		comment = "rule for stateful firewall for pod"
		args = []string{"-m", "comment", "--comment", comment, "-m", "conntrack", "--ctstate", "RELATED,ESTABLISHED", "-j", "ACCEPT"}
		exists, err = iptablesCmdHandler.Exists("filter", podFwChainName, args...)
		if err != nil {
			return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}
		if !exists {
			err := iptablesCmdHandler.Insert("filter", podFwChainName, 1, args...)
			if err != nil {
				return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
			}
		}

		// ensure there is rule in filter table and FORWARD chain to jump to pod specific firewall chain
		// this rule applies to the traffic getting routed (coming for other node pods)
		comment = "rule to jump traffic destined to POD name:" + pod.name + " namespace: " + pod.namespace +
			" to chain " + podFwChainName
		args = []string{"-m", "comment", "--comment", comment, "-d", pod.ip, "-j", podFwChainName}
		exists, err = iptablesCmdHandler.Exists("filter", kubeForwardChainName, args...)
		if err != nil {
			return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}
		if !exists {
			err := iptablesCmdHandler.Insert("filter", kubeForwardChainName, 1, args...)
			if err != nil {
				return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
			}
		}

		// ensure there is rule in filter table and OUTPUT chain to jump to pod specific firewall chain
		// this rule applies to the traffic from a pod getting routed back to another pod on same node by service proxy
		exists, err = iptablesCmdHandler.Exists("filter", kubeOutputChainName, args...)
		if err != nil {
			return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}
		if !exists {
			err := iptablesCmdHandler.Insert("filter", kubeOutputChainName, 1, args...)
			if err != nil {
				return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
			}
		}

		// ensure there is rule in filter table and forward chain to jump to pod specific firewall chain
		// this rule applies to the traffic getting switched (coming for same node pods)
		comment = "rule to jump traffic destined to POD name:" + pod.name + " namespace: " + pod.namespace +
			" to chain " + podFwChainName
		args = []string{"-m", "physdev", "--physdev-is-bridged",
			"-m", "comment", "--comment", comment,
			"-d", pod.ip,
			"-j", podFwChainName}
		exists, err = iptablesCmdHandler.Exists("filter", kubeForwardChainName, args...)
		if err != nil {
			return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}
		if !exists {
			err = iptablesCmdHandler.Insert("filter", kubeForwardChainName, 1, args...)
			if err != nil {
				return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
			}
		}

		err = dropUnmarkedTrafficRules(pod.name, pod.namespace, podFwChainName)
		if err != nil {
			return nil, err
		}
	}

	// loop through the pods running on the node which egress network policies to be applied
	egressNetworkPolicyEnabledPods, err := npc.getEgressNetworkPolicyEnabledPods(networkPoliciesInfo, npc.nodeIP.String())
	if err != nil {
		return nil, err
	}
	for _, pod := range *egressNetworkPolicyEnabledPods {

		// below condition occurs when we get trasient update while removing or adding pod
		// subsequent update will do the correct action
		if len(pod.ip) == 0 || pod.ip == "" {
			continue
		}

		// ensure pod specific firewall chain exist for all the pods that need egress firewall
		podFwChainName := podFirewallChainName(pod.namespace, pod.name, version)
		err = iptablesCmdHandler.NewChain("filter", podFwChainName)
		if err != nil && err.(*iptables.Error).ExitStatus() != 1 {
			return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}
		activePodFwChains[podFwChainName] = true

		// add entries in pod firewall to run through required network policies
		for _, policy := range networkPoliciesInfo {
			if _, ok := policy.targetPods[pod.ip]; ok {
				comment := "run through nw policy " + policy.name
				policyChainName := networkPolicyChainName(policy.namespace, policy.name, version)
				args := []string{"-m", "comment", "--comment", comment, "-j", policyChainName}
				exists, err := iptablesCmdHandler.Exists("filter", podFwChainName, args...)
				if err != nil {
					return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
				}
				if !exists {
					err := iptablesCmdHandler.Insert("filter", podFwChainName, 1, args...)
					if err != nil && err.(*iptables.Error).ExitStatus() != 1 {
						return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
					}
				}
			}
		}

		// ensure statefull firewall, that permits return traffic for the traffic originated by the pod
		comment := "rule for stateful firewall for pod"
		args := []string{"-m", "comment", "--comment", comment, "-m", "conntrack", "--ctstate", "RELATED,ESTABLISHED", "-j", "ACCEPT"}
		exists, err := iptablesCmdHandler.Exists("filter", podFwChainName, args...)
		if err != nil {
			return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}
		if !exists {
			err := iptablesCmdHandler.Insert("filter", podFwChainName, 1, args...)
			if err != nil {
				return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
			}
		}

		egressFilterChains := []string{kubeInputChainName, kubeForwardChainName, kubeOutputChainName}
		for _, chain := range egressFilterChains {
			// ensure there is rule in filter table and FORWARD chain to jump to pod specific firewall chain
			// this rule applies to the traffic getting forwarded/routed (traffic from the pod destinted
			// to pod on a different node)
			comment = "rule to jump traffic from POD name:" + pod.name + " namespace: " + pod.namespace +
				" to chain " + podFwChainName
			args = []string{"-m", "comment", "--comment", comment, "-s", pod.ip, "-j", podFwChainName}
			exists, err = iptablesCmdHandler.Exists("filter", chain, args...)
			if err != nil {
				return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
			}
			if !exists {
				err := iptablesCmdHandler.AppendUnique("filter", chain, args...)
				if err != nil {
					return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
				}
			}
		}

		// ensure there is rule in filter table and forward chain to jump to pod specific firewall chain
		// this rule applies to the traffic getting switched (coming for same node pods)
		comment = "rule to jump traffic from POD name:" + pod.name + " namespace: " + pod.namespace +
			" to chain " + podFwChainName
		args = []string{"-m", "physdev", "--physdev-is-bridged",
			"-m", "comment", "--comment", comment,
			"-s", pod.ip,
			"-j", podFwChainName}
		exists, err = iptablesCmdHandler.Exists("filter", kubeForwardChainName, args...)
		if err != nil {
			return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
		}
		if !exists {
			err = iptablesCmdHandler.Insert("filter", kubeForwardChainName, 1, args...)
			if err != nil {
				return nil, fmt.Errorf("Failed to run iptables command: %s", err.Error())
			}
		}

		err = dropUnmarkedTrafficRules(pod.name, pod.namespace, podFwChainName)
		if err != nil {
			return nil, err
		}
	}

	return activePodFwChains, nil
}

func (npc *NetworkPolicyController) getIngressNetworkPolicyEnabledPods(networkPoliciesInfo []networkPolicyInfo, nodeIP string) (*map[string]podInfo, error) {
	nodePods := make(map[string]podInfo)

	for _, obj := range npc.podLister.List() {
		pod := obj.(*api.Pod)

		if strings.Compare(pod.Status.HostIP, nodeIP) != 0 {
			continue
		}
		for _, policy := range networkPoliciesInfo {
			if policy.namespace != pod.ObjectMeta.Namespace {
				continue
			}
			_, ok := policy.targetPods[pod.Status.PodIP]
			if ok && (policy.policyType == "both" || policy.policyType == "ingress") {
				glog.V(2).Infof("Found pod name: " + pod.ObjectMeta.Name + " namespace: " + pod.ObjectMeta.Namespace + " for which network policies need to be applied.")
				nodePods[pod.Status.PodIP] = podInfo{ip: pod.Status.PodIP,
					name:      pod.ObjectMeta.Name,
					namespace: pod.ObjectMeta.Namespace,
					labels:    pod.ObjectMeta.Labels}
				break
			}
		}
	}
	return &nodePods, nil

}

func (npc *NetworkPolicyController) getEgressNetworkPolicyEnabledPods(networkPoliciesInfo []networkPolicyInfo, nodeIP string) (*map[string]podInfo, error) {

	nodePods := make(map[string]podInfo)

	for _, obj := range npc.podLister.List() {
		pod := obj.(*api.Pod)

		if strings.Compare(pod.Status.HostIP, nodeIP) != 0 {
			continue
		}
		for _, policy := range networkPoliciesInfo {
			if policy.namespace != pod.ObjectMeta.Namespace {
				continue
			}
			_, ok := policy.targetPods[pod.Status.PodIP]
			if ok && (policy.policyType == "both" || policy.policyType == "egress") {
				glog.V(2).Infof("Found pod name: " + pod.ObjectMeta.Name + " namespace: " + pod.ObjectMeta.Namespace + " for which network policies need to be applied.")
				nodePods[pod.Status.PodIP] = podInfo{ip: pod.Status.PodIP,
					name:      pod.ObjectMeta.Name,
					namespace: pod.ObjectMeta.Namespace,
					labels:    pod.ObjectMeta.Labels}
				break
			}
		}
	}
	return &nodePods, nil
}

func podFirewallChainName(namespace, podName string, version string) string {
	hash := sha256.Sum256([]byte(namespace + podName + version))
	encoded := base32.StdEncoding.EncodeToString(hash[:])
	return kubePodFirewallChainPrefix + encoded[:16]
}