Fetch MTU from the nodeIP interface

daemon/cmd/daemon.go

@@ -289,7 +289,13 @@ func NewDaemon(ctx context.Context, dp datapath.Datapath) (*Daemon, *endpointRes
 		return nil, nil, fmt.Errorf("unable to setup encryption: %s", err)
 	}
 
-	mtuConfig := mtu.NewConfiguration(authKeySize, option.Config.EnableIPSec, option.Config.Tunnel != option.TunnelDisabled, configuredMTU)
+	var mtuConfig mtu.Configuration
+	externalIP := node.GetExternalIPv4()
+	if externalIP == nil {
+		externalIP = node.GetIPv6()
+	}
+	// ExternalIP could be nil but we are covering that case inside NewConfiguration
+	mtuConfig = mtu.NewConfiguration(authKeySize, option.Config.EnableIPSec, option.Config.Tunnel != option.TunnelDisabled, configuredMTU, externalIP)
 
 	nodeMngr, err := nodemanager.NewManager("all", dp.Node(), ipcache.IPIdentityCache, option.Config)
 	if err != nil {

daemon/cmd/status_test.go

@@ -82,7 +82,7 @@ func (g *GetNodesSuite) Test_getNodesHandle(c *C) {
 		{
 			name: "create a client ID and store it locally",
 			setupArgs: func() args {
-				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0), &cnitypes.NetConf{})
+				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0, nil), &cnitypes.NetConf{})
 				nodeDiscovery.LocalNode.Name = "foo"
 				return args{
 					params: GetClusterNodesParams{
@@ -114,7 +114,7 @@ func (g *GetNodesSuite) Test_getNodesHandle(c *C) {
 		{
 			name: "retrieve nodes diff from a client that was already present",
 			setupArgs: func() args {
-				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0), &cnitypes.NetConf{})
+				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0, nil), &cnitypes.NetConf{})
 				nodeDiscovery.LocalNode.Name = "foo"
 				return args{
 					params: GetClusterNodesParams{
@@ -168,7 +168,7 @@ func (g *GetNodesSuite) Test_getNodesHandle(c *C) {
 		{
 			name: "retrieve nodes from an expired client, it should be ok because the clean up only happens when on insertion",
 			setupArgs: func() args {
-				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0), &cnitypes.NetConf{})
+				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0, nil), &cnitypes.NetConf{})
 				nodeDiscovery.LocalNode.Name = "foo"
 				return args{
 					params: GetClusterNodesParams{
@@ -223,7 +223,7 @@ func (g *GetNodesSuite) Test_getNodesHandle(c *C) {
 		{
 			name: "retrieve nodes for a new client, the expired client should be deleted",
 			setupArgs: func() args {
-				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0), &cnitypes.NetConf{})
+				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0, nil), &cnitypes.NetConf{})
 				nodeDiscovery.LocalNode.Name = "foo"
 				return args{
 					params: GetClusterNodesParams{
@@ -273,7 +273,7 @@ func (g *GetNodesSuite) Test_getNodesHandle(c *C) {
 		{
 			name: "retrieve nodes for a new client, however the randomizer allocated an existing clientID, so we should return a empty clientID",
 			setupArgs: func() args {
-				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0), &cnitypes.NetConf{})
+				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0, nil), &cnitypes.NetConf{})
 				nodeDiscovery.LocalNode.Name = "foo"
 				return args{
 					params: GetClusterNodesParams{
@@ -323,7 +323,7 @@ func (g *GetNodesSuite) Test_getNodesHandle(c *C) {
 		{
 			name: "retrieve nodes for a client that does not want to have diffs, leave all other stored clients alone",
 			setupArgs: func() args {
-				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0), &cnitypes.NetConf{})
+				nodeDiscovery := nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0, nil), &cnitypes.NetConf{})
 				nodeDiscovery.LocalNode.Name = "foo"
 				return args{
 					params: GetClusterNodesParams{},
@@ -433,7 +433,7 @@ func (g *GetNodesSuite) Test_cleanupClients(c *C) {
 		h := &getNodes{
 			clients: args.clients,
 			d: &Daemon{
-				nodeDiscovery: nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0), &cnitypes.NetConf{}),
+				nodeDiscovery: nodediscovery.NewNodeDiscovery(nm, mtu.NewConfiguration(0, false, false, 0, nil), &cnitypes.NetConf{}),
 			},
 		}
 		h.cleanupClients()

pkg/datapath/linux/node_linux_test.go

@@ -71,7 +71,7 @@ const (
 func (s *linuxPrivilegedBaseTestSuite) SetUpTest(c *check.C, addressing datapath.NodeAddressing, enableIPv6, enableIPv4 bool) {
 	bpf.ConfigureResourceLimits()
 	s.nodeAddressing = addressing
-	s.mtuConfig = mtu.NewConfiguration(0, false, false, 1500)
+	s.mtuConfig = mtu.NewConfiguration(0, false, false, 1500, nil)
 	s.enableIPv6 = enableIPv6
 	s.enableIPv4 = enableIPv4
 

pkg/logging/logfields/logfields.go

@@ -168,6 +168,9 @@ const (
 	// CIDR is a IPv4/IPv4 subnet/CIDR
 	CIDR = "cidr"
 
+	// MTU is the maximum transmission unit of one interface
+	MTU = "mtu"
+
 	// Interface is an interface id/name on the system
 	Interface = "interface"
 

pkg/mtu/detect_darwin.go

@@ -16,6 +16,12 @@
 
 package mtu
 
+import "net"
+
 func autoDetect() (int, error) {
 	return EthernetMTU, nil
 }
+
+func getMTUFromIf(net.IP) (int, error) {
+	return EthernetMTU, nil
+}

pkg/mtu/detect_linux.go

@@ -20,6 +20,10 @@ import (
 	"fmt"
 	"net"
 
+	"github.com/cilium/cilium/pkg/logging/logfields"
+
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 	"github.com/vishvananda/netlink"
 )
 
@@ -75,3 +79,44 @@ func autoDetect() (int, error) {
 
 	return EthernetMTU, nil
 }
+
+// getMTUFromIf finds the interface that holds the ip and returns its mtu
+func getMTUFromIf(ip net.IP) (int, error) {
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		return 0, errors.Wrap(err, "Unable to list interfaces")
+	}
+
+	for _, iface := range ifaces {
+		addrs, err := iface.Addrs()
+		if err != nil {
+			log.WithFields(logrus.Fields{
+				logfields.Device: iface.Name,
+			}).Warning("Unable to list all addresses")
+			continue
+		}
+
+		for _, addr := range addrs {
+			myIP, _, err := net.ParseCIDR(addr.String())
+
+			if err != nil {
+				log.WithFields(logrus.Fields{
+					logfields.Device: iface.Name,
+					logfields.IPAddr: addr,
+				}).Warning("Unable parse the address")
+				continue
+			}
+
+			if myIP.Equal(ip) == true {
+				myMTU := iface.MTU
+				log.WithFields(logrus.Fields{
+					logfields.Device: iface.Name,
+					logfields.IPAddr: ip,
+					logfields.MTU:    myMTU,
+				}).Info("Inheriting MTU from external network interface")
+				return myMTU, nil
+			}
+		}
+	}
+	return 0, fmt.Errorf("No interface contains the provided ip: %v", ip)
+}

pkg/mtu/mtu.go

@@ -14,6 +14,8 @@
 
 package mtu
 
+import "net"
+
 const (
 	// MaxMTU is the highest MTU that can be used for devices and routes
 	// handled by Cilium. It will typically be used to configure inbound
@@ -96,13 +98,17 @@ type Configuration struct {
 // specified, otherwise it will be automatically detected. if encapEnabled is
 // true, the MTU is adjusted to account for encapsulation overhead for all
 // routes involved in node to node communication.
-func NewConfiguration(authKeySize int, encryptEnabled bool, encapEnabled bool, mtu int) Configuration {
+func NewConfiguration(authKeySize int, encryptEnabled bool, encapEnabled bool, mtu int, mtuDetectIP net.IP) Configuration {
 	encryptOverhead := 0
 
 	if mtu == 0 {
 		var err error
 
-		mtu, err = autoDetect()
+		if mtuDetectIP != nil {
+			mtu, err = getMTUFromIf(mtuDetectIP)
+		} else {
+			mtu, err = autoDetect()
+		}
 		if err != nil {
 			log.WithError(err).Warning("Unable to automatically detect MTU")
 			mtu = EthernetMTU

pkg/mtu/mtu_test.go

@@ -17,6 +17,7 @@
 package mtu
 
 import (
+	"net"
 	"testing"
 
 	. "gopkg.in/check.v1"
@@ -30,48 +31,63 @@ var _ = Suite(&MTUSuite{})
 
 func (m *MTUSuite) TestNewConfiguration(c *C) {
 	// Add routes with no encryption or tunnel
-	conf := NewConfiguration(0, false, false, 0)
+	conf := NewConfiguration(0, false, false, 0, nil)
 	c.Assert(conf.GetDeviceMTU(), Not(Equals), 0)
 	c.Assert(conf.GetRouteMTU(), Equals, conf.GetDeviceMTU())
 
 	// Add routes with no encryption or tunnel and set MTU
-	conf = NewConfiguration(0, false, false, 1400)
+	conf = NewConfiguration(0, false, false, 1400, nil)
 	c.Assert(conf.GetDeviceMTU(), Equals, 1400)
 	c.Assert(conf.GetRouteMTU(), Equals, conf.GetDeviceMTU())
 
 	// Add routes with tunnel
-	conf = NewConfiguration(0, false, true, 1400)
+	conf = NewConfiguration(0, false, true, 1400, nil)
 	c.Assert(conf.GetDeviceMTU(), Equals, 1400)
 	c.Assert(conf.GetRouteMTU(), Equals, conf.GetDeviceMTU()-TunnelOverhead)
 
 	// Add routes with tunnel and set MTU
-	conf = NewConfiguration(0, false, true, 1400)
+	conf = NewConfiguration(0, false, true, 1400, nil)
 	c.Assert(conf.GetDeviceMTU(), Equals, 1400)
 	c.Assert(conf.GetRouteMTU(), Equals, conf.GetDeviceMTU()-TunnelOverhead)
 
 	// Add routes with encryption and set MTU using standard 128bit, larger 256bit and smaller 96bit ICVlen keys
-	conf = NewConfiguration(16, true, false, 1400)
+	conf = NewConfiguration(16, true, false, 1400, nil)
 	c.Assert(conf.GetDeviceMTU(), Equals, 1400)
 	c.Assert(conf.GetRouteMTU(), Equals, conf.GetDeviceMTU()-EncryptionIPsecOverhead)
 
-	conf = NewConfiguration(32, true, false, 1400)
+	conf = NewConfiguration(32, true, false, 1400, nil)
 	c.Assert(conf.GetDeviceMTU(), Equals, 1400)
 	c.Assert(conf.GetRouteMTU(), Equals, conf.GetDeviceMTU()-(EncryptionIPsecOverhead+16))
 
-	conf = NewConfiguration(12, true, false, 1400)
+	conf = NewConfiguration(12, true, false, 1400, nil)
 	c.Assert(conf.GetDeviceMTU(), Equals, 1400)
 	c.Assert(conf.GetRouteMTU(), Equals, conf.GetDeviceMTU()-(EncryptionIPsecOverhead-4))
 
 	// Add routes with encryption and tunnels using standard 128bit, larger 256bit and smaller 96bit ICVlen keys
-	conf = NewConfiguration(16, true, true, 1400)
+	conf = NewConfiguration(16, true, true, 1400, nil)
 	c.Assert(conf.GetDeviceMTU(), Equals, 1400)
 	c.Assert(conf.GetRouteMTU(), Equals, conf.GetDeviceMTU()-(TunnelOverhead+EncryptionIPsecOverhead))
 
-	conf = NewConfiguration(32, true, true, 1400)
+	conf = NewConfiguration(32, true, true, 1400, nil)
 	c.Assert(conf.GetDeviceMTU(), Equals, 1400)
 	c.Assert(conf.GetRouteMTU(), Equals, conf.GetDeviceMTU()-(TunnelOverhead+EncryptionIPsecOverhead+16))
 
-	conf = NewConfiguration(32, true, true, 1400)
+	conf = NewConfiguration(32, true, true, 1400, nil)
 	c.Assert(conf.GetDeviceMTU(), Equals, 1400)
 	c.Assert(conf.GetRouteMTU(), Equals, conf.GetDeviceMTU()-(TunnelOverhead+EncryptionIPsecOverhead+16))
+
+	testIP1 := net.IPv4(0, 0, 0, 0)
+	testIP2 := net.IPv4(127, 0, 0, 1)
+	result, _ := getMTUFromIf(testIP1)
+	c.Assert(result, Equals, 0)
+
+	conf = NewConfiguration(0, true, true, 1400, testIP1)
+	c.Assert(conf.GetDeviceMTU(), Equals, 1400)
+
+	conf = NewConfiguration(0, true, true, 0, testIP1)
+	c.Assert(conf.GetDeviceMTU(), Equals, 1500)
+
+	// Assuming loopback interface always exists and has mtu=65536
+	conf = NewConfiguration(0, true, true, 0, testIP2)
+	c.Assert(conf.GetDeviceMTU(), Equals, 65536)
 }