Delay port redirect until packet reaches container

With port redirect in the ingress path happening before ipvs in the
ingess sandbox, there is a chance of 5-tuple collision in the ipvs
connection table for two entirely different services have different
PublishedPorts but the same TargetPort. To disambiguate the ipvs
connection table, delay the port redirect from PublishedPort to
TargetPort until after the loadbalancing has happened in ipvs. To be
specific, perform the redirect after the packet enters the real backend
container namespace.

Signed-off-by: Jana Radhakrishnan <mrjana@docker.com>

libnetwork/service_linux.go

@@ -26,6 +26,7 @@ import (
 
 func init() {
 	reexec.Register("fwmarker", fwMarker)
+	reexec.Register("redirecter", redirecter)
 }
 
 func newService(name string, id string, ingressPorts []*PortConfig, aliases []string) *service {
@@ -275,6 +276,12 @@ func (sb *sandbox) populateLoadbalancers(ep *endpoint) {
 	n := ep.getNetwork()
 	eIP := ep.Iface().Address()
 
+	if n.ingress {
+		if err := addRedirectRules(sb.Key(), eIP, ep.ingressPorts); err != nil {
+			logrus.Errorf("Failed to add redirect rules for ep %s: %v", ep.Name(), err)
+		}
+	}
+
 	if sb.ingress {
 		// For the ingress sandbox if this is not gateway
 		// endpoint do nothing.
@@ -390,7 +397,7 @@ func (sb *sandbox) addLBBackend(ip, vip net.IP, fwMark uint32, ingressPorts []*P
 		}
 
 		logrus.Debugf("Creating service for vip %s fwMark %d ingressPorts %#v", vip, fwMark, ingressPorts)
-		if err := invokeFWMarker(sb.Key(), vip, fwMark, ingressPorts, filteredPorts, eIP, false); err != nil {
+		if err := invokeFWMarker(sb.Key(), vip, fwMark, ingressPorts, eIP, false); err != nil {
 			logrus.Errorf("Failed to add firewall mark rule in sbox %s: %v", sb.Key(), err)
 			return
 		}
@@ -461,7 +468,7 @@ func (sb *sandbox) rmLBBackend(ip, vip net.IP, fwMark uint32, ingressPorts []*Po
 			}
 		}
 
-		if err := invokeFWMarker(sb.Key(), vip, fwMark, ingressPorts, filteredPorts, eIP, true); err != nil {
+		if err := invokeFWMarker(sb.Key(), vip, fwMark, ingressPorts, eIP, true); err != nil {
 			logrus.Errorf("Failed to add firewall mark rule in sbox %s: %v", sb.Key(), err)
 		}
 	}
@@ -755,11 +762,8 @@ func readPortsFromFile(fileName string) ([]*PortConfig, error) {
 
 // Invoke fwmarker reexec routine to mark vip destined packets with
 // the passed firewall mark.
-func invokeFWMarker(path string, vip net.IP, fwMark uint32, ingressPorts []*PortConfig, filteredPorts []*PortConfig, eIP *net.IPNet, isDelete bool) error {
-	var (
-		ingressPortsFile  string
-		filteredPortsFile string
-	)
+func invokeFWMarker(path string, vip net.IP, fwMark uint32, ingressPorts []*PortConfig, eIP *net.IPNet, isDelete bool) error {
+	var ingressPortsFile string
 
 	if len(ingressPorts) != 0 {
 		var err error
@@ -767,14 +771,8 @@ func invokeFWMarker(path string, vip net.IP, fwMark uint32, ingressPorts []*Port
 		if err != nil {
 			return err
 		}
-	}
 
-	if len(filteredPorts) != 0 {
-		var err error
-		filteredPortsFile, err = writePortsToFile(filteredPorts)
-		if err != nil {
-			return err
-		}
+		defer os.Remove(ingressPortsFile)
 	}
 
 	addDelOpt := "-A"
@@ -784,7 +782,7 @@ func invokeFWMarker(path string, vip net.IP, fwMark uint32, ingressPorts []*Port
 
 	cmd := &exec.Cmd{
 		Path:   reexec.Self(),
-		Args:   append([]string{"fwmarker"}, path, vip.String(), fmt.Sprintf("%d", fwMark), addDelOpt, ingressPortsFile, filteredPortsFile, eIP.String()),
+		Args:   append([]string{"fwmarker"}, path, vip.String(), fmt.Sprintf("%d", fwMark), addDelOpt, ingressPortsFile, eIP.String()),
 		Stdout: os.Stdout,
 		Stderr: os.Stderr,
 	}
@@ -801,13 +799,12 @@ func fwMarker() {
 	runtime.LockOSThread()
 	defer runtime.UnlockOSThread()
 
-	if len(os.Args) < 8 {
+	if len(os.Args) < 7 {
 		logrus.Error("invalid number of arguments..")
 		os.Exit(1)
 	}
 
 	var ingressPorts []*PortConfig
-	var filteredPorts []*PortConfig
 	if os.Args[5] != "" {
 		var err error
 		ingressPorts, err = readPortsFromFile(os.Args[5])
@@ -817,15 +814,6 @@ func fwMarker() {
 		}
 	}
 
-	if os.Args[6] != "" {
-		var err error
-		filteredPorts, err = readPortsFromFile(os.Args[6])
-		if err != nil {
-			logrus.Errorf("Failed reading filtered ports file: %v", err)
-			os.Exit(7)
-		}
-	}
-
 	vip := os.Args[2]
 	fwMark, err := strconv.ParseUint(os.Args[3], 10, 32)
 	if err != nil {
@@ -835,12 +823,6 @@ func fwMarker() {
 	addDelOpt := os.Args[4]
 
 	rules := [][]string{}
-	for _, iPort := range filteredPorts {
-		rule := strings.Fields(fmt.Sprintf("-t nat %s PREROUTING -p %s --dport %d -j REDIRECT --to-port %d",
-			addDelOpt, strings.ToLower(PortConfig_Protocol_name[int32(iPort.Protocol)]), iPort.PublishedPort, iPort.TargetPort))
-		rules = append(rules, rule)
-	}
-
 	for _, iPort := range ingressPorts {
 		rule := strings.Fields(fmt.Sprintf("-t mangle %s PREROUTING -p %s --dport %d -j MARK --set-mark %d",
 			addDelOpt, strings.ToLower(PortConfig_Protocol_name[int32(iPort.Protocol)]), iPort.PublishedPort, fwMark))
@@ -860,9 +842,9 @@ func fwMarker() {
 	}
 
 	if addDelOpt == "-A" {
-		eIP, subnet, err := net.ParseCIDR(os.Args[7])
+		eIP, subnet, err := net.ParseCIDR(os.Args[6])
 		if err != nil {
-			logrus.Errorf("Failed to parse endpoint IP %s: %v", os.Args[7], err)
+			logrus.Errorf("Failed to parse endpoint IP %s: %v", os.Args[6], err)
 			os.Exit(9)
 		}
 
@@ -889,3 +871,82 @@ func fwMarker() {
 		}
 	}
 }
+
+func addRedirectRules(path string, eIP *net.IPNet, ingressPorts []*PortConfig) error {
+	var ingressPortsFile string
+
+	if len(ingressPorts) != 0 {
+		var err error
+		ingressPortsFile, err = writePortsToFile(ingressPorts)
+		if err != nil {
+			return err
+		}
+		defer os.Remove(ingressPortsFile)
+	}
+
+	cmd := &exec.Cmd{
+		Path:   reexec.Self(),
+		Args:   append([]string{"redirecter"}, path, eIP.String(), ingressPortsFile),
+		Stdout: os.Stdout,
+		Stderr: os.Stderr,
+	}
+
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("reexec failed: %v", err)
+	}
+
+	return nil
+}
+
+// Redirecter reexec function.
+func redirecter() {
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	if len(os.Args) < 4 {
+		logrus.Error("invalid number of arguments..")
+		os.Exit(1)
+	}
+
+	var ingressPorts []*PortConfig
+	if os.Args[3] != "" {
+		var err error
+		ingressPorts, err = readPortsFromFile(os.Args[3])
+		if err != nil {
+			logrus.Errorf("Failed reading ingress ports file: %v", err)
+			os.Exit(2)
+		}
+	}
+
+	eIP, _, err := net.ParseCIDR(os.Args[2])
+	if err != nil {
+		logrus.Errorf("Failed to parse endpoint IP %s: %v", os.Args[2], err)
+		os.Exit(3)
+	}
+
+	rules := [][]string{}
+	for _, iPort := range ingressPorts {
+		rule := strings.Fields(fmt.Sprintf("-t nat -A PREROUTING -d %s -p %s --dport %d -j REDIRECT --to-port %d",
+			eIP.String(), strings.ToLower(PortConfig_Protocol_name[int32(iPort.Protocol)]), iPort.PublishedPort, iPort.TargetPort))
+		rules = append(rules, rule)
+	}
+
+	ns, err := netns.GetFromPath(os.Args[1])
+	if err != nil {
+		logrus.Errorf("failed get network namespace %q: %v", os.Args[1], err)
+		os.Exit(4)
+	}
+	defer ns.Close()
+
+	if err := netns.Set(ns); err != nil {
+		logrus.Errorf("setting into container net ns %v failed, %v", os.Args[1], err)
+		os.Exit(5)
+	}
+
+	for _, rule := range rules {
+		if err := iptables.RawCombinedOutputNative(rule...); err != nil {
+			logrus.Errorf("setting up rule failed, %v: %v", rule, err)
+			os.Exit(5)
+		}
+	}
+}