Add a reset command for network impairments in netem tool (srl-labs#2488)

* Add reset command for network impairments in netem tool

* fix test

* format

---------

Co-authored-by: Roman Dodin <[email protected]>

Author: FloSch62

cmd/tools_netem.go

@@ -63,6 +63,13 @@ func init() {
 	netemCmd.AddCommand(netemShowCmd)
 	netemShowCmd.Flags().StringVarP(&netemNode, "node", "n", "", "node to apply impairment to")
 	netemShowCmd.Flags().StringVarP(&netemFormat, "format", "f", "table", "output format (table, json)")
+
+	// Add reset command
+	netemCmd.AddCommand(netemResetCmd)
+	netemResetCmd.Flags().StringVarP(&netemNode, "node", "n", "", "node to reset impairment on")
+	netemResetCmd.Flags().StringVarP(&netemInterface, "interface", "i", "", "interface to reset impairment on")
+	netemResetCmd.MarkFlagRequired("node")
+	netemResetCmd.MarkFlagRequired("interface")
 }
 
 var netemCmd = &cobra.Command{
@@ -87,6 +94,14 @@ var netemShowCmd = &cobra.Command{
 	RunE:    netemShowFn,
 }
 
+var netemResetCmd = &cobra.Command{
+	Use:     "reset",
+	Short:   "reset link impairments",
+	Long:    `Reset network impairments by deleting the netem qdisc from the specified interface.`,
+	PreRunE: validateInputAndRoot,
+	RunE:    netemResetFn,
+}
+
 func netemSetFn(_ *cobra.Command, _ []string) error {
 	// Ensure that the sch_netem kernel module is loaded (for Fedora/RHEL compatibility)
 	if err := exec.Command("modprobe", "sch_netem").Run(); err != nil {
@@ -384,3 +399,67 @@ func netemShowFn(_ *cobra.Command, _ []string) error {
 
 	return err
 }
+
+func netemResetFn(_ *cobra.Command, _ []string) error {
+	// Get the runtime initializer.
+	_, rinit, err := clab.RuntimeInitializer(common.Runtime)
+	if err != nil {
+		return err
+	}
+
+	// init the runtime
+	rt := rinit()
+	err = rt.Init(
+		runtime.WithConfig(
+			&runtime.RuntimeConfig{
+				Timeout: common.Timeout,
+			},
+		),
+	)
+	if err != nil {
+		return err
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	// retrieve the container's NSPath
+	nodeNsPath, err := rt.GetNSPath(ctx, netemNode)
+	if err != nil {
+		return err
+	}
+
+	var nodeNs ns.NetNS
+	if nodeNs, err = ns.GetNS(nodeNsPath); err != nil {
+		return err
+	}
+
+	tcnl, err := tc.NewTC(int(nodeNs.Fd()))
+	if err != nil {
+		return err
+	}
+	defer func() {
+		if err := tcnl.Close(); err != nil {
+			log.Errorf("could not close rtnetlink socket: %v\n", err)
+		}
+	}()
+
+	err = nodeNs.Do(func(_ ns.NetNS) error {
+		netemIfLink, err := netlink.LinkByName(links.SanitiseInterfaceName(netemInterface))
+		if err != nil {
+			return err
+		}
+		// Retrieve the standard net.Interface from the netlink.Link name.
+		netemIfIface, err := net.InterfaceByName(netemIfLink.Attrs().Name)
+		if err != nil {
+			return err
+		}
+		if err := tc.DeleteImpairments(tcnl, netemIfIface); err != nil {
+			return err
+		}
+		fmt.Printf("Reset impairments on node %q, interface %q\n", netemNode, netemIfLink.Attrs().Name)
+		return nil
+	})
+
+	return err
+}

docs/cmd/tools/netem/reset.md

@@ -0,0 +1,49 @@
+# Resetting Link Impairments
+
+With the `containerlab tools netem reset` command users can remove (reset) all network impairments on a specified interface of a containerlab node. This command deletes the netem qdisc associated with the interface, restoring it to its default state. If no impairments are present, the command will complete successfully without error.
+
+## Usage
+
+```bash
+containerlab tools netem reset [local-flags]
+```
+
+## Flags
+
+### node
+
+The mandatory `--node | -n` flag specifies the name of the containerlab node on which to reset link impairments.
+
+### interface
+
+The mandatory `--interface | -i` flag specifies the interface on which the netem impairments should be reset.
+
+## Examples
+
+### Resetting impairments on an interface
+
+This example resets the impairments on the interface `eth1` of node `clab-netem-r1`:
+
+```bash
+containerlab tools netem reset -n clab-netem-r1 -i eth1
+```
+
+Output:
+
+```bash
+Reset impairments on node "clab-netem-r1", interface "eth1"
+```
+
+### Resetting impairments when none are set
+
+If no impairments are configured on the specified interface, the command will complete without error:
+
+```bash
+containerlab tools netem reset -n clab-netem-r1 -i eth0
+```
+
+Output:
+
+```bash
+Reset impairments on node "clab-netem-r1", interface "eth0"
+```

docs/manual/impairments.md

@@ -8,8 +8,9 @@ Labs are meant to be a reflection of real-world scenarios. To make simulated net
 
 * [`tools netem set`](../cmd/tools/netem/set.md)
 * [`tools netem show`](../cmd/tools/netem/show.md)
+* [`tools netem reset`](../cmd/tools/netem/reset.md)
 
-These commands allow users to set link impairments (delay, jitter, packet loss) on any link that belongs to a container node and create labs simulating real-world network conditions.
+These commands allow users to set, show and reset link impairments (delay, jitter, packet loss) on any link that belongs to a container node and create labs simulating real-world network conditions.
 
 ```bash title="setting packet loss at 10% rate on eth1 interface of clab-netem-r1 node"
 containerlab tools netem set -n clab-netem-r1 -i eth1 --loss 10

internal/tc/tc.go

@@ -84,6 +84,24 @@ func SetImpairments(tcnl *tc.Tc, nodeName string, link *net.Interface, delay, ji
 	return nil, fmt.Errorf("could not find qdisc for interface %q", link.Name)
 }
 
+// DeleteImpairments deletes the netem impairments from the given interface.
+func DeleteImpairments(tcnl *tc.Tc, link *net.Interface) error {
+	qdisc := tc.Object{
+		Msg: tc.Msg{
+			Family:  unix.AF_UNSPEC,
+			Ifindex: uint32(link.Index),
+			Handle:  core.BuildHandle(0x1, 0x0),
+			Parent:  tc.HandleRoot,
+			Info:    0,
+		},
+		Attribute: tc.Attribute{
+			Kind:  "netem",
+			Netem: &tc.Netem{},
+		},
+	}
+	return tcnl.Qdisc().Delete(&qdisc)
+}
+
 // setDelay sets delay and jitter to the qdisc.
 func setDelay(qdisc *tc.Object, delay, jitter time.Duration) error {
 	delayTcTime, err := core.Duration2TcTime(delay)

links/link_macvlan.go

@@ -156,7 +156,8 @@ func (l *LinkMacVlan) Deploy(ctx context.Context, _ Endpoint) error {
 	// enable promiscuous mode
 	err = netlink.SetPromiscOn(mvInterface)
 	if err != nil {
-		return fmt.Errorf("failed setting promiscuous mode for interface %s (%s:%s): %v", l.NodeEndpoint.GetRandIfaceName(), l.NodeEndpoint.GetNode().GetShortName(), l.NodeEndpoint.GetIfaceName(), err)
+		return fmt.Errorf("failed setting promiscuous mode for interface %s (%s:%s): %v",
+			l.NodeEndpoint.GetRandIfaceName(), l.NodeEndpoint.GetNode().GetShortName(), l.NodeEndpoint.GetIfaceName(), err)
 	}
 
 	// add the link to the Node Namespace

tests/01-smoke/08-tools-cmds.robot

@@ -67,3 +67,21 @@ Show link impairments in JSON format
     Should Contain    ${output}    10
     Should Contain    ${output}    1000
     Should Contain    ${output}    2
+
+Reset link impairments
+    ${rc}    ${output} =    Run And Return Rc And Output
+    ...    ${CLAB_BIN} --runtime ${runtime} tools netem reset -n clab-${lab-name}-l1 -i eth3
+    Log    ${output}
+    Should Be Equal As Integers    ${rc}    0
+    Should Contain    ${output}    Reset impairments on node "clab-${lab-name}-l1", interface "eth3"
+
+    # Show impairments again to verify they have been reset.
+    ${rc}    ${output} =    Run And Return Rc And Output
+    ...    ${CLAB_BIN} --runtime ${runtime} tools netem show -n clab-${lab-name}-l1
+    Log    ${output}
+    Should Be Equal As Integers    ${rc}    0
+    # Verify that the previous impairment values are no longer present.
+    Should Not Contain    ${output}    100ms
+    Should Not Contain    ${output}    2ms
+    Should Not Contain    ${output}    10.00%
+    Should Not Contain    ${output}    1000