Enable DNS proxying for ipvlan-l3

The internal DNS resolver should only forward requests to external
resolvers if the libnetwork.Sandbox served by the resolver has external
network access (so, no forwarding for '--internal' networks).

The test for external network access was whether the Sandbox had an
Endpoint with a gateway configured.

However, an ipvlan-l3 networks with external network access does not
have a gateway, it has a default route bound to an interface.

Also, we document that an ipvlan network with no parent interface is
equivalent to a '--internal' network. But, in this case, an ipvlan-l2
network was configured with a gateway. So, DNS proxying would be enabled
in the internal resolver (and, if the host's resolver was on a localhost
address, requests to external resolvers from the host's network
namespace would succeed).

So, this change adjusts the test for enabling DNS proxying to include
a check for '--internal' (as a shortcut) and, for non-internal networks,
checks for a default route as well as a gateway. It also disables
configuration of a gateway or a default route for an ipvlan Endpoint if
no parent interface is specified.

(Note if a parent interface with no external network is supplied as
'-o parent=<dummy>', the gateway/default route will still be set up
and external DNS proxying will be enabled. The network must be
configured as '--internal' to prevent that from happening.)

Signed-off-by: Rob Murray <rob.murray@docker.com>

integration/network/ipvlan/ipvlan_test.go

@@ -4,12 +4,15 @@ package ipvlan // import "github.com/docker/docker/integration/network/ipvlan"
 
 import (
 	"context"
+	"fmt"
 	"os"
 	"os/exec"
 	"strings"
 	"sync"
 	"testing"
 
+	"github.com/docker/docker/api/types"
+	containertypes "github.com/docker/docker/api/types/container"
 	dclient "github.com/docker/docker/client"
 	"github.com/docker/docker/integration/internal/container"
 	net "github.com/docker/docker/integration/internal/network"
@@ -17,6 +20,7 @@ import (
 	"github.com/docker/docker/testutil"
 	"github.com/docker/docker/testutil/daemon"
 	"gotest.tools/v3/assert"
+	is "gotest.tools/v3/assert/cmp"
 	"gotest.tools/v3/skip"
 )
 
@@ -79,14 +83,20 @@ func TestDockerNetworkIpvlan(t *testing.T) {
 			name: "L3InternalMode",
 			test: testIpvlanL3InternalMode,
 		}, {
-			name: "L2MultiSubnet",
-			test: testIpvlanL2MultiSubnet,
+			name: "L2MultiSubnetWithParent",
+			test: testIpvlanL2MultiSubnetWithParent,
+		}, {
+			name: "L2MultiSubnetNoParent",
+			test: testIpvlanL2MultiSubnetNoParent,
 		}, {
 			name: "L3MultiSubnet",
 			test: testIpvlanL3MultiSubnet,
 		}, {
-			name: "Addressing",
-			test: testIpvlanAddressing,
+			name: "L2Addressing",
+			test: testIpvlanL2Addressing,
+		}, {
+			name: "L3Addressing",
+			test: testIpvlanL3Addressing,
 		},
 	} {
 
@@ -225,10 +235,21 @@ func testIpvlanL3InternalMode(t *testing.T, ctx context.Context, client dclient.
 	assert.NilError(t, err)
 }
 
-func testIpvlanL2MultiSubnet(t *testing.T, ctx context.Context, client dclient.APIClient) {
+func testIpvlanL2MultiSubnetWithParent(t *testing.T, ctx context.Context, client dclient.APIClient) {
+	const parentIfName = "di-dummy0"
+	n.CreateMasterDummy(ctx, t, parentIfName)
+	defer n.DeleteInterface(ctx, t, parentIfName)
+	testIpvlanL2MultiSubnet(t, ctx, client, parentIfName)
+}
+
+func testIpvlanL2MultiSubnetNoParent(t *testing.T, ctx context.Context, client dclient.APIClient) {
+	testIpvlanL2MultiSubnet(t, ctx, client, "")
+}
+
+func testIpvlanL2MultiSubnet(t *testing.T, ctx context.Context, client dclient.APIClient, parent string) {
 	netName := "dualstackl2"
 	net.CreateNoError(ctx, t, client, netName,
-		net.WithIPvlan("", ""),
+		net.WithIPvlan(parent, ""),
 		net.WithIPv6(),
 		net.WithIPAM("172.28.200.0/24", ""),
 		net.WithIPAM("172.28.202.0/24", "172.28.202.254"),
@@ -250,11 +271,22 @@ func testIpvlanL2MultiSubnet(t *testing.T, ctx context.Context, client dclient.A
 	)
 	c1, err := client.ContainerInspect(ctx, id1)
 	assert.NilError(t, err)
+	if parent == "" {
+		// Inspect the v4 gateway to ensure no default GW was assigned
+		assert.Check(t, is.Equal(c1.NetworkSettings.Networks[netName].Gateway, ""))
+		// Inspect the v6 gateway to ensure no default GW was assigned
+		assert.Check(t, is.Equal(c1.NetworkSettings.Networks[netName].IPv6Gateway, ""))
+	} else {
+		// Inspect the v4 gateway to ensure the proper default GW was assigned
+		assert.Check(t, is.Equal(c1.NetworkSettings.Networks[netName].Gateway, "172.28.200.1"))
+		// Inspect the v6 gateway to ensure the proper default GW was assigned
+		assert.Check(t, is.Equal(c1.NetworkSettings.Networks[netName].IPv6Gateway, "2001:db8:abc8::1"))
+	}
 
-	// verify ipv4 connectivity to the explicit --ipv address second to first
+	// verify ipv4 connectivity to the explicit --ip address second to first
 	_, err = container.Exec(ctx, client, id2, []string{"ping", "-c", "1", c1.NetworkSettings.Networks[netName].IPAddress})
 	assert.NilError(t, err)
-	// verify ipv6 connectivity to the explicit --ipv6 address second to first
+	// verify ipv6 connectivity to the explicit --ip6 address second to first
 	_, err = container.Exec(ctx, client, id2, []string{"ping6", "-c", "1", c1.NetworkSettings.Networks[netName].GlobalIPv6Address})
 	assert.NilError(t, err)
 
@@ -271,22 +303,24 @@ func testIpvlanL2MultiSubnet(t *testing.T, ctx context.Context, client dclient.A
 	)
 	c3, err := client.ContainerInspect(ctx, id3)
 	assert.NilError(t, err)
+	if parent == "" {
+		// Inspect the v4 gateway to ensure no default GW was assigned
+		assert.Check(t, is.Equal(c3.NetworkSettings.Networks[netName].Gateway, ""))
+		// Inspect the v6 gateway to ensure no default GW was assigned
+		assert.Check(t, is.Equal(c3.NetworkSettings.Networks[netName].IPv6Gateway, ""))
+	} else {
+		// Inspect the v4 gateway to ensure the proper explicitly assigned default GW was assigned
+		assert.Check(t, is.Equal(c3.NetworkSettings.Networks[netName].Gateway, "172.28.202.254"))
+		// Inspect the v6 gateway to ensure the proper explicitly assigned default GW was assigned
+		assert.Check(t, is.Equal(c3.NetworkSettings.Networks[netName].IPv6Gateway, "2001:db8:abc6::254"))
+	}
 
-	// verify ipv4 connectivity to the explicit --ipv address from third to fourth
+	// verify ipv4 connectivity to the explicit --ip address from third to fourth
 	_, err = container.Exec(ctx, client, id4, []string{"ping", "-c", "1", c3.NetworkSettings.Networks[netName].IPAddress})
 	assert.NilError(t, err)
-	// verify ipv6 connectivity to the explicit --ipv6 address from third to fourth
+	// verify ipv6 connectivity to the explicit --ip6 address from third to fourth
 	_, err = container.Exec(ctx, client, id4, []string{"ping6", "-c", "1", c3.NetworkSettings.Networks[netName].GlobalIPv6Address})
 	assert.NilError(t, err)
-
-	// Inspect the v4 gateway to ensure the proper default GW was assigned
-	assert.Equal(t, c1.NetworkSettings.Networks[netName].Gateway, "172.28.200.1")
-	// Inspect the v6 gateway to ensure the proper default GW was assigned
-	assert.Equal(t, c1.NetworkSettings.Networks[netName].IPv6Gateway, "2001:db8:abc8::1")
-	// Inspect the v4 gateway to ensure the proper explicitly assigned default GW was assigned
-	assert.Equal(t, c3.NetworkSettings.Networks[netName].Gateway, "172.28.202.254")
-	// Inspect the v6 gateway to ensure the proper explicitly assigned default GW was assigned
-	assert.Equal(t, c3.NetworkSettings.Networks[netName].IPv6Gateway, "2001:db8:abc6::254")
 }
 
 func testIpvlanL3MultiSubnet(t *testing.T, ctx context.Context, client dclient.APIClient) {
@@ -353,51 +387,61 @@ func testIpvlanL3MultiSubnet(t *testing.T, ctx context.Context, client dclient.A
 	assert.Equal(t, c3.NetworkSettings.Networks[netName].IPv6Gateway, "")
 }
 
-func testIpvlanAddressing(t *testing.T, ctx context.Context, client dclient.APIClient) {
-	// Verify ipvlan l2 mode sets the proper default gateway routes via netlink
-	// for either an explicitly set route by the user or inferred via default IPAM
+// Verify ipvlan l2 mode sets the proper default gateway routes via netlink
+// for either an explicitly set route by the user or inferred via default IPAM
+func testIpvlanL2Addressing(t *testing.T, ctx context.Context, client dclient.APIClient) {
+	const parentIfName = "di-dummy0"
+	n.CreateMasterDummy(ctx, t, parentIfName)
+	defer n.DeleteInterface(ctx, t, parentIfName)
+
 	netNameL2 := "dualstackl2"
 	net.CreateNoError(ctx, t, client, netNameL2,
-		net.WithIPvlan("", "l2"),
+		net.WithIPvlan(parentIfName, "l2"),
 		net.WithIPv6(),
 		net.WithIPAM("172.28.140.0/24", "172.28.140.254"),
 		net.WithIPAM("2001:db8:abcb::/64", ""),
 	)
 	assert.Check(t, n.IsNetworkAvailable(ctx, client, netNameL2))
 
-	id1 := container.Run(ctx, t, client,
+	id := container.Run(ctx, t, client,
 		container.WithNetworkMode(netNameL2),
 	)
 	// Validate ipvlan l2 mode defaults gateway sets the default IPAM next-hop inferred from the subnet
-	result, err := container.Exec(ctx, client, id1, []string{"ip", "route"})
+	result, err := container.Exec(ctx, client, id, []string{"ip", "route"})
 	assert.NilError(t, err)
-	assert.Check(t, strings.Contains(result.Combined(), "default via 172.28.140.254 dev eth0"))
+	assert.Check(t, is.Contains(result.Combined(), "default via 172.28.140.254 dev eth0"))
 	// Validate ipvlan l2 mode sets the v6 gateway to the user specified default gateway/next-hop
-	result, err = container.Exec(ctx, client, id1, []string{"ip", "-6", "route"})
+	result, err = container.Exec(ctx, client, id, []string{"ip", "-6", "route"})
 	assert.NilError(t, err)
-	assert.Check(t, strings.Contains(result.Combined(), "default via 2001:db8:abcb::1 dev eth0"))
+	assert.Check(t, is.Contains(result.Combined(), "default via 2001:db8:abcb::1 dev eth0"))
+}
+
+// Validate ipvlan l3 mode sets the v4 gateway to dev eth0 and disregards any explicit or inferred next-hops
+func testIpvlanL3Addressing(t *testing.T, ctx context.Context, client dclient.APIClient) {
+	const parentIfName = "di-dummy0"
+	n.CreateMasterDummy(ctx, t, parentIfName)
+	defer n.DeleteInterface(ctx, t, parentIfName)
 
-	// Validate ipvlan l3 mode sets the v4 gateway to dev eth0 and disregards any explicit or inferred next-hops
 	netNameL3 := "dualstackl3"
 	net.CreateNoError(ctx, t, client, netNameL3,
-		net.WithIPvlan("", "l3"),
+		net.WithIPvlan(parentIfName, "l3"),
 		net.WithIPv6(),
 		net.WithIPAM("172.28.160.0/24", "172.28.160.254"),
 		net.WithIPAM("2001:db8:abcd::/64", "2001:db8:abcd::254"),
 	)
 	assert.Check(t, n.IsNetworkAvailable(ctx, client, netNameL3))
 
-	id2 := container.Run(ctx, t, client,
+	id := container.Run(ctx, t, client,
 		container.WithNetworkMode(netNameL3),
 	)
 	// Validate ipvlan l3 mode sets the v4 gateway to dev eth0 and disregards any explicit or inferred next-hops
-	result, err = container.Exec(ctx, client, id2, []string{"ip", "route"})
+	result, err := container.Exec(ctx, client, id, []string{"ip", "route"})
 	assert.NilError(t, err)
-	assert.Check(t, strings.Contains(result.Combined(), "default dev eth0"))
+	assert.Check(t, is.Contains(result.Combined(), "default dev eth0"))
 	// Validate ipvlan l3 mode sets the v6 gateway to dev eth0 and disregards any explicit or inferred next-hops
-	result, err = container.Exec(ctx, client, id2, []string{"ip", "-6", "route"})
+	result, err = container.Exec(ctx, client, id, []string{"ip", "-6", "route"})
 	assert.NilError(t, err)
-	assert.Check(t, strings.Contains(result.Combined(), "default dev eth0"))
+	assert.Check(t, is.Contains(result.Combined(), "default dev eth0"))
 }
 
 var (
@@ -420,3 +464,85 @@ func ipvlanKernelSupport(t *testing.T) bool {
 
 	return ipvlanSupported
 }
+
+// TestIPVlanDNS checks whether DNS is forwarded, for combinations of l2/l3 mode,
+// with/without a parent interface, and with '--internal'. Note that, there's no
+// attempt here to give the ipvlan network external connectivity - when this test
+// supplies a parent interface, it's a dummy. External DNS lookups only work
+// because the daemon is configured to see a host resolver on a loopback
+// interface, so the external DNS lookup happens in the host's namespace. The
+// test is checking that an automatically configured dummy interface causes the
+// network to behave as if it was '--internal'. Regression test for
+// https://github.com/moby/moby/issues/47662
+func TestIPVlanDNS(t *testing.T) {
+	skip.If(t, testEnv.IsRootless, "rootless mode has different view of network")
+
+	ctx := testutil.StartSpan(baseContext, t)
+
+	net.StartDaftDNS(t, "127.0.0.1")
+
+	tmpFileName := net.WriteTempResolvConf(t, "127.0.0.1")
+	d := daemon.New(t, daemon.WithEnvVars("DOCKER_TEST_RESOLV_CONF_PATH="+tmpFileName))
+	d.StartWithBusybox(ctx, t)
+	t.Cleanup(func() { d.Stop(t) })
+	c := d.NewClientT(t)
+
+	const parentIfName = "di-dummy0"
+	n.CreateMasterDummy(ctx, t, parentIfName)
+	defer n.DeleteInterface(ctx, t, parentIfName)
+
+	const netName = "ipvlan-dns-net"
+
+	testcases := []struct {
+		name     string
+		parent   string
+		internal bool
+		expDNS   bool
+	}{
+		{
+			name:   "with parent",
+			parent: parentIfName,
+			// External DNS should be used (even though the network has no external connectivity).
+			expDNS: true,
+		},
+		{
+			name: "no parent",
+			// External DNS should not be used, equivalent to '--internal'.
+		},
+		{
+			name:     "with parent, internal",
+			parent:   parentIfName,
+			internal: true,
+			// External DNS should not be used.
+		},
+	}
+
+	for _, mode := range []string{"l2", "l3"} {
+		for _, tc := range testcases {
+			name := fmt.Sprintf("Mode=%v/HasParent=%v/Internal=%v", mode, tc.parent != "", tc.internal)
+			t.Run(name, func(t *testing.T) {
+				ctx := testutil.StartSpan(ctx, t)
+				createOpts := []func(*types.NetworkCreate){
+					net.WithIPvlan(tc.parent, mode),
+				}
+				if tc.internal {
+					createOpts = append(createOpts, net.WithInternal())
+				}
+				net.CreateNoError(ctx, t, c, netName, createOpts...)
+				defer c.NetworkRemove(ctx, netName)
+
+				ctrId := container.Run(ctx, t, c, container.WithNetworkMode(netName))
+				defer c.ContainerRemove(ctx, ctrId, containertypes.RemoveOptions{Force: true})
+				res, err := container.Exec(ctx, c, ctrId, []string{"nslookup", "test.example"})
+				assert.NilError(t, err)
+				if tc.expDNS {
+					assert.Check(t, is.Equal(res.ExitCode, 0))
+					assert.Check(t, is.Contains(res.Stdout(), net.DNSRespAddr))
+				} else {
+					assert.Check(t, is.Equal(res.ExitCode, 1))
+					assert.Check(t, is.Contains(res.Stdout(), "SERVFAIL"))
+				}
+			})
+		}
+	}
+}

libnetwork/drivers/ipvlan/ipvlan_joinleave.go

@@ -122,6 +122,10 @@ func (d *driver) Join(nid, eid string, sboxKey string, jinfo driverapi.JoinInfo,
 			log.G(context.TODO()).Debugf("Ipvlan Endpoint Joined with IPv6_Addr: %s IpVlan_Mode: %s, Parent: %s",
 				ep.addrv6.IP.String(), n.config.IpvlanMode, n.config.Parent)
 		}
+		// If n.config.Internal was set locally by the driver because there's no parent
+		// interface, libnetwork doesn't know the network is internal. So, stop it from
+		// adding a gateway endpoint.
+		jinfo.DisableGatewayService()
 	}
 	iNames := jinfo.InterfaceName()
 	err = iNames.SetNames(vethName, containerVethPrefix)

libnetwork/drivers/ipvlan/ipvlan_network.go

@@ -41,6 +41,7 @@ func (d *driver) CreateNetwork(nid string, option map[string]interface{}, nInfo
 	// if parent interface not specified, create a dummy type link to use named dummy+net_id
 	if config.Parent == "" {
 		config.Parent = getDummyName(stringid.TruncateID(config.ID))
+		config.Internal = true
 	}
 	foundExisting, err := d.createNetwork(config)
 	if err != nil {

libnetwork/endpoint.go

@@ -569,12 +569,12 @@ func (ep *Endpoint) sbJoin(sb *Sandbox, options ...EndpointOption) (err error) {
 		return sb.setupDefaultGW()
 	}
 
-	currentExtEp := sb.getGatewayEndpoint()
 	// Enable upstream forwarding if the sandbox gained external connectivity.
 	if sb.resolver != nil {
-		sb.resolver.SetForwardingPolicy(currentExtEp != nil)
+		sb.resolver.SetForwardingPolicy(sb.hasExternalAccess())
 	}
 
+	currentExtEp := sb.getGatewayEndpoint()
 	moveExtConn := currentExtEp != extEp
 	if moveExtConn {
 		if extEp != nil {
@@ -767,13 +767,13 @@ func (ep *Endpoint) sbLeave(sb *Sandbox, force bool) error {
 		return sb.setupDefaultGW()
 	}
 
-	// New endpoint providing external connectivity for the sandbox
-	extEp = sb.getGatewayEndpoint()
 	// Disable upstream forwarding if the sandbox lost external connectivity.
 	if sb.resolver != nil {
-		sb.resolver.SetForwardingPolicy(extEp != nil)
+		sb.resolver.SetForwardingPolicy(sb.hasExternalAccess())
 	}
 
+	// New endpoint providing external connectivity for the sandbox
+	extEp = sb.getGatewayEndpoint()
 	if moveExtConn && extEp != nil {
 		log.G(context.TODO()).Debugf("Programming external connectivity on endpoint %s (%s)", extEp.Name(), extEp.ID())
 		extN, err := extEp.getNetworkFromStore()

libnetwork/endpoint_info.go

@@ -382,6 +382,31 @@ func (ep *Endpoint) SetGatewayIPv6(gw6 net.IP) error {
 	return nil
 }
 
+// hasGatewayOrDefaultRoute returns true if ep has a gateway, or a route to '0.0.0.0'/'::'.
+func (ep *Endpoint) hasGatewayOrDefaultRoute() bool {
+	ep.mu.Lock()
+	defer ep.mu.Unlock()
+
+	if ep.joinInfo != nil {
+		if len(ep.joinInfo.gw) > 0 {
+			return true
+		}
+		for _, route := range ep.joinInfo.StaticRoutes {
+			if route.Destination.IP.IsUnspecified() && net.IP(route.Destination.Mask).IsUnspecified() {
+				return true
+			}
+		}
+	}
+	if ep.iface != nil {
+		for _, route := range ep.iface.routes {
+			if route.IP.IsUnspecified() && net.IP(route.Mask).IsUnspecified() {
+				return true
+			}
+		}
+	}
+	return false
+}
+
 func (ep *Endpoint) retrieveFromStore() (*Endpoint, error) {
 	n, err := ep.getNetworkFromStore()
 	if err != nil {

libnetwork/sandbox.go

@@ -507,6 +507,21 @@ func (sb *Sandbox) resolveName(ctx context.Context, nameOrAlias string, networkN
 	return nil, ipv6Miss
 }
 
+// hasExternalAccess returns true if any of sb's Endpoints appear to have external
+// network access.
+func (sb *Sandbox) hasExternalAccess() bool {
+	for _, ep := range sb.Endpoints() {
+		nw := ep.getNetwork()
+		if nw.Internal() || nw.Type() == "null" || nw.Type() == "host" {
+			continue
+		}
+		if ep.hasGatewayOrDefaultRoute() {
+			return true
+		}
+	}
+	return false
+}
+
 // EnableService makes a managed container's service available by adding the
 // endpoint to the service load balancer and service discovery.
 func (sb *Sandbox) EnableService() (err error) {

libnetwork/sandbox_dns_unix.go

@@ -48,7 +48,7 @@ func (sb *Sandbox) startResolver(restore bool) {
 		// have a gateway. So, if the Sandbox is only connected to an 'internal' network,
 		// it will not forward DNS requests to external resolvers. The resolver's
 		// proxyDNS setting is then updated as network Endpoints are added/removed.
-		sb.resolver = NewResolver(resolverIPSandbox, sb.getGatewayEndpoint() != nil, sb)
+		sb.resolver = NewResolver(resolverIPSandbox, sb.hasExternalAccess(), sb)
 		defer func() {
 			if err != nil {
 				sb.resolver = nil