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Stop macvlan with no parent from using ext-dns

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We document that an macvlan network with no parent interface is
equivalent to a '--internal' network. But, in this case, an macvlan
network was still 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).

This change disables configuration of a gateway for a macvlan Endpoint
if no parent interface is specified.

(Note if a parent interface with no external network is supplied as
'-o parent=<dummy>', the gateway will still be set up. Documentation
will need to be updated to note that '--internal' should be used to
prevent DNS request forwarding in this case.)

Signed-off-by: Rob Murray <rob.murray@docker.com>
This commit is contained in:
Rob Murray 2024-04-03 19:06:46 +01:00
parent 7b570f00ba
commit dc2755273e
3 changed files with 135 additions and 18 deletions
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148
integration/network/macvlan/macvlan_test.go
View file

@ -7,6 +7,8 @@ import (
"strings"
"testing"
"github.com/docker/docker/api/types"
containertypes "github.com/docker/docker/api/types/container"
"github.com/docker/docker/client"
"github.com/docker/docker/integration/internal/container"
net "github.com/docker/docker/integration/internal/network"
@ -14,6 +16,7 @@ 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"
)
@ -66,8 +69,11 @@ func TestDockerNetworkMacvlan(t *testing.T) {
name: "InternalMode",
test: testMacvlanInternalMode,
}, {
name: "MultiSubnet",
test: testMacvlanMultiSubnet,
name: "MultiSubnetWithParent",
test: testMacvlanMultiSubnetWithParent,
}, {
name: "MultiSubnetNoParent",
test: testMacvlanMultiSubnetNoParent,
}, {
name: "Addressing",
test: testMacvlanAddressing,
@ -173,10 +179,21 @@ func testMacvlanInternalMode(t *testing.T, ctx context.Context, client client.AP
assert.Check(t, err == nil)
}
func testMacvlanMultiSubnet(t *testing.T, ctx context.Context, client client.APIClient) {
func testMacvlanMultiSubnetWithParent(t *testing.T, ctx context.Context, client client.APIClient) {
const parentIfName = "dm-dummy0"
n.CreateMasterDummy(ctx, t, parentIfName)
defer n.DeleteInterface(ctx, t, parentIfName)
testMacvlanMultiSubnet(t, ctx, client, parentIfName)
}
func testMacvlanMultiSubnetNoParent(t *testing.T, ctx context.Context, client client.APIClient) {
testMacvlanMultiSubnet(t, ctx, client, "")
}
func testMacvlanMultiSubnet(t *testing.T, ctx context.Context, client client.APIClient, parent string) {
netName := "dualstackbridge"
net.CreateNoError(ctx, t, client, netName,
net.WithMacvlan(""),
net.WithMacvlan(parent),
net.WithIPv6(),
net.WithIPAM("172.28.100.0/24", ""),
net.WithIPAM("172.28.102.0/24", "172.28.102.254"),
@ -199,11 +216,22 @@ func testMacvlanMultiSubnet(t *testing.T, ctx context.Context, client client.API
)
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["dualstackbridge"].Gateway, ""))
// Inspect the v6 gateway to ensure no default GW was assigned
assert.Check(t, is.Equal(c1.NetworkSettings.Networks["dualstackbridge"].IPv6Gateway, ""))
} else {
// Inspect the v4 gateway to ensure the proper default GW was assigned
assert.Check(t, is.Equal(c1.NetworkSettings.Networks["dualstackbridge"].Gateway, "172.28.100.1"))
// Inspect the v6 gateway to ensure the proper default GW was assigned
assert.Check(t, is.Equal(c1.NetworkSettings.Networks["dualstackbridge"].IPv6Gateway, "2001:db8:abc2::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["dualstackbridge"].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["dualstackbridge"].GlobalIPv6Address})
assert.NilError(t, err)
@ -220,29 +248,35 @@ func testMacvlanMultiSubnet(t *testing.T, ctx context.Context, client client.API
)
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["dualstackbridge"].Gateway, ""))
// Inspect the v6 gateway to ensure no default GW was assigned
assert.Check(t, is.Equal(c3.NetworkSettings.Networks["dualstackbridge"].IPv6Gateway, ""))
} else {
// Inspect the v4 gateway to ensure the proper explicitly assigned default GW was assigned
assert.Check(t, is.Equal(c3.NetworkSettings.Networks["dualstackbridge"].Gateway, "172.28.102.254"))
// Inspect the v6 gateway to ensure the proper explicitly assigned default GW was assigned
assert.Check(t, is.Equal(c3.NetworkSettings.Networks["dualstackbridge"].IPv6Gateway, "2001:db8:abc4::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["dualstackbridge"].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["dualstackbridge"].GlobalIPv6Address})
assert.NilError(t, err)
// Inspect the v4 gateway to ensure the proper default GW was assigned
assert.Equal(t, c1.NetworkSettings.Networks["dualstackbridge"].Gateway, "172.28.100.1")
// Inspect the v6 gateway to ensure the proper default GW was assigned
assert.Equal(t, c1.NetworkSettings.Networks["dualstackbridge"].IPv6Gateway, "2001:db8:abc2::1")
// Inspect the v4 gateway to ensure the proper explicitly assigned default GW was assigned
assert.Equal(t, c3.NetworkSettings.Networks["dualstackbridge"].Gateway, "172.28.102.254")
// Inspect the v6 gateway to ensure the proper explicitly assigned default GW was assigned
assert.Equal(t, c3.NetworkSettings.Networks["dualstackbridge"].IPv6Gateway, "2001:db8:abc4::254")
}
func testMacvlanAddressing(t *testing.T, ctx context.Context, client client.APIClient) {
const parentIfName = "dm-dummy0"
n.CreateMasterDummy(ctx, t, parentIfName)
defer n.DeleteInterface(ctx, t, parentIfName)
// Ensure the default gateways, next-hops and default dev devices are properly set
netName := "dualstackbridge"
net.CreateNoError(ctx, t, client, netName,
net.WithMacvlan(""),
net.WithMacvlan(parentIfName),
net.WithIPv6(),
net.WithOption("macvlan_mode", "bridge"),
net.WithIPAM("172.28.130.0/24", ""),
@ -263,3 +297,81 @@ func testMacvlanAddressing(t *testing.T, ctx context.Context, client client.APIC
assert.NilError(t, err)
assert.Check(t, strings.Contains(result.Combined(), "default via 2001:db8:abca::254 dev eth0"))
}
// TestMACVlanDNS checks whether DNS is forwarded, with/without a parent
// interface, and with '--internal'. Note that there's no attempt here to give
// the macvlan 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'.
func TestMACVlanDNS(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 = "dm-dummy0"
n.CreateMasterDummy(ctx, t, parentIfName)
defer n.DeleteInterface(ctx, t, parentIfName)
const netName = "macvlan-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,
expDNS: false,
},
}
for _, tc := range testcases {
t.Run(tc.name, func(t *testing.T) {
ctx := testutil.StartSpan(ctx, t)
createOpts := []func(*types.NetworkCreate){
net.WithMacvlan(tc.parent),
}
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"))
}
})
}
}

4
libnetwork/drivers/macvlan/macvlan_joinleave.go
View file

@ -83,6 +83,10 @@ func (d *driver) Join(nid, eid string, sboxKey string, jinfo driverapi.JoinInfo,
log.G(context.TODO()).Debugf("Macvlan Endpoint Joined with IPv6_Addr: %s MacVlan_Mode: %s, Parent: %s",
ep.addrv6.IP.String(), n.config.MacvlanMode, 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)

1
libnetwork/drivers/macvlan/macvlan_network.go
View file

@ -31,6 +31,7 @@ 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 {