Implement helper for extracting OVS-managed bridges from an iface list

achilleasa · achilleasa · commit 8b45eb830d6b · 2020-05-15T14:35:20.000+01:00
The helper makes use of the 'ovs-vsctl' command to get a list of
OVS-managed bridges and use this information to filter a provided list
of interfaces.
diff --git a/container/broker/broker.go b/container/broker/broker.go
@@ -4,6 +4,7 @@
 package broker
 
 import (
+	"os/exec"
 	"strings"
 
 	"github.com/juju/collections/set"
@@ -25,6 +26,9 @@ import (
 
 var logger = loggo.GetLogger("juju.container.broker")
 
+// Overridden by tests
+var getCommandOutput = func(cmd *exec.Cmd) ([]byte, error) { return cmd.Output() }
+
 //go:generate go run github.com/golang/mock/mockgen -package mocks -destination mocks/apicalls_mock.go github.com/juju/juju/container/broker APICalls
 type APICalls interface {
 	ContainerConfig() (params.ContainerConfig, error)
@@ -261,3 +265,33 @@ func proxyConfigurationFromContainerCfg(cfg params.ContainerConfig) instancecfg.
 		SnapStoreProxyURL:   cfg.SnapStoreProxyURL,
 	}
 }
+
+// ovsManagedBridges returns a filtered version of ifaceList that only contains
+// bridge interfaces managed by openvswitch.
+func ovsManagedBridges(ifaceList corenetwork.InterfaceInfos) (corenetwork.InterfaceInfos, error) {
+	if _, err := exec.LookPath("ovs-vsctl"); err != nil {
+		// ovs tools not installed; nothing to do
+		if execErr, isExecErr := err.(*exec.Error); isExecErr && execErr.Unwrap() == exec.ErrNotFound {
+			return nil, nil
+		}
+
+		return nil, errors.Annotate(err, "ovsManagedBridges: looking for ovs-vsctl")
+	}
+
+	// Query list of ovs-managed device names
+	res, err := getCommandOutput(exec.Command("ovs-vsctl", "list-br"))
+	if err != nil {
+		return nil, errors.Annotate(err, "querying ovs-managed bridges via ovs-vsctl")
+	}
+
+	ovsBridges := set.NewStrings()
+	for _, iface := range strings.Split(string(res), "\n") {
+		if iface = strings.TrimSpace(iface); iface != "" {
+			ovsBridges.Add(iface)
+		}
+	}
+
+	return ifaceList.Filter(func(iface corenetwork.InterfaceInfo) bool {
+		return ovsBridges.Contains(iface.InterfaceName)
+	}), nil
+}
diff --git a/container/broker/broker_internal_test.go b/container/broker/broker_internal_test.go
@@ -0,0 +1,77 @@
+// Copyright 2020 Canonical Ltd.
+// Licensed under the AGPLv3, see LICENCE file for details.
+
+package broker
+
+import (
+	"os/exec"
+
+	"github.com/juju/testing"
+	jc "github.com/juju/testing/checkers"
+	gc "gopkg.in/check.v1"
+
+	"github.com/juju/juju/core/network"
+)
+
+type brokerSuite struct {
+	testing.IsolationSuite
+}
+
+var _ = gc.Suite(&brokerSuite{})
+
+func (s *brokerSuite) SetUpSuite(c *gc.C) {
+	s.IsolationSuite.SetUpSuite(c)
+}
+
+func (s *brokerSuite) SetUpTest(c *gc.C) {
+	s.IsolationSuite.SetUpTest(c)
+}
+
+func (s *brokerSuite) TestExistingOVSManagedBridges(c *gc.C) {
+	// Patch output for "ovs-vsctl list-br" and make sure exec.LookPath can
+	// detect it in the path
+	testing.PatchExecutableAsEchoArgs(c, s, "ovs-vsctl", 0)
+	s.PatchValue(&getCommandOutput, func(cmd *exec.Cmd) ([]byte, error) {
+		c.Assert(cmd.Args, gc.DeepEquals, []string{"ovs-vsctl", "list-br"}, gc.Commentf("expected ovs-vsctl to be invoked with 'list-br' as an argument"))
+		return []byte("ovsbr1" + "\n"), nil
+	})
+
+	ifaces := network.InterfaceInfos{
+		{InterfaceName: "eth0"},
+		{InterfaceName: "eth1"},
+		{InterfaceName: "lxdbr0"},
+		{InterfaceName: "ovsbr1"},
+	}
+
+	ovsIfaces, err := ovsManagedBridges(ifaces)
+	c.Assert(err, jc.ErrorIsNil)
+	c.Assert(ovsIfaces, gc.HasLen, 1, gc.Commentf("expected ovs-managed bridge list to contain a single entry"))
+	c.Assert(ovsIfaces[0].InterfaceName, gc.Equals, "ovsbr1", gc.Commentf("expected ovs-managed bridge list to contain iface 'ovsbr1'"))
+}
+
+func (s *brokerSuite) TestNonExistingOVSManagedBridges(c *gc.C) {
+	// Patch output for "ovs-vsctl list-br" and make sure exec.LookPath can
+	// detect it in the path
+	testing.PatchExecutableAsEchoArgs(c, s, "ovs-vsctl", 0)
+	s.PatchValue(&getCommandOutput, func(cmd *exec.Cmd) ([]byte, error) {
+		c.Assert(cmd.Args, gc.DeepEquals, []string{"ovs-vsctl", "list-br"}, gc.Commentf("expected ovs-vsctl to be invoked with 'list-br' as an argument"))
+		return []byte("\n"), nil
+	})
+
+	ifaces := network.InterfaceInfos{
+		{InterfaceName: "eth0"},
+		{InterfaceName: "eth1"},
+		{InterfaceName: "lxdbr0"},
+	}
+
+	ovsIfaces, err := ovsManagedBridges(ifaces)
+	c.Assert(err, jc.ErrorIsNil)
+	c.Assert(ovsIfaces, gc.HasLen, 0, gc.Commentf("expected ovs-managed bridge list to be empty"))
+}
+
+func (s *brokerSuite) TestMissingOVSTools(c *gc.C) {
+	ifaces := network.InterfaceInfos{{InterfaceName: "eth0"}}
+	ovsIfaces, err := ovsManagedBridges(ifaces)
+	c.Assert(err, jc.ErrorIsNil)
+	c.Assert(ovsIfaces, gc.HasLen, 0, gc.Commentf("expected ovs-managed bridge list to be empty"))
+}
