allow filter networks by dangling status

add the ability to filter networks by their dangling status via:

`network ls --filter dangling=true/false`

Fixes: #14595
Signed-off-by: Carlo Lobrano <c.lobrano@gmail.com>

docs/source/markdown/podman-network-ls.1.md

@@ -25,6 +25,7 @@ Supported filters:
 | label      | Filter by network with (or without, in the case of label!=[...] is used) the specified labels.   |
 | name       | Filter by network name (accepts `regex`).                                                        |
 | until      | Filter by networks created before given timestamp.                                               |
+| dangling   | Filter by networks with no containers attached.                                                  |
 
 
 The `driver` filter accepts values: `bridge`, `macvlan`, `ipvlan`.
@@ -33,6 +34,8 @@ The `label` *filter* accepts two formats. One is the `label`=*key* or `label`=*k
 
 The `until` *filter* can be Unix timestamps, date formatted timestamps, or Go duration strings (e.g. 10m, 1h30m) computed relative to the machine’s time.
 
+The `dangling` *filter* accepts values `true` or `false`.
+
 #### **--format**=*format*
 
 Change the default output format.  This can be of a supported type like 'json'

pkg/domain/infra/abi/network.go

@@ -2,6 +2,7 @@ package abi
 
 import (
 	"context"
+	"strconv"
 
 	"github.com/containers/common/libnetwork/types"
 	netutil "github.com/containers/common/libnetwork/util"
@@ -12,10 +13,39 @@ import (
 )
 
 func (ic *ContainerEngine) NetworkList(ctx context.Context, options entities.NetworkListOptions) ([]types.Network, error) {
+	// dangling filter is not provided by netutil
+	var wantDangling bool
+
+	val, filterDangling := options.Filters["dangling"]
+	if filterDangling {
+		switch len(val) {
+		case 0:
+			return nil, errors.Errorf("got no values for filter key \"dangling\"")
+		case 1:
+			var err error
+			wantDangling, err = strconv.ParseBool(val[0])
+			if err != nil {
+				return nil, errors.Errorf("invalid dangling filter value \"%v\"", val[0])
+			}
+			delete(options.Filters, "dangling")
+		default:
+			return nil, errors.Errorf("got more than one value for filter key \"dangling\"")
+		}
+	}
+
 	filters, err := netutil.GenerateNetworkFilters(options.Filters)
 	if err != nil {
 		return nil, err
 	}
+
+	if filterDangling {
+		danglingFilterFunc, err := ic.createDanglingFilterFunc(wantDangling)
+		if err != nil {
+			return nil, err
+		}
+
+		filters = append(filters, danglingFilterFunc)
+	}
 	nets, err := ic.Libpod.Network().NetworkList(filters...)
 	return nets, err
 }
@@ -144,6 +174,33 @@ func (ic *ContainerEngine) NetworkExists(ctx context.Context, networkname string
 
 // Network prune removes unused cni networks
 func (ic *ContainerEngine) NetworkPrune(ctx context.Context, options entities.NetworkPruneOptions) ([]*entities.NetworkPruneReport, error) {
+	// get all filters
+	filters, err := netutil.GenerateNetworkPruneFilters(options.Filters)
+	if err != nil {
+		return nil, err
+	}
+	danglingFilterFunc, err := ic.createDanglingFilterFunc(true)
+	if err != nil {
+		return nil, err
+	}
+	filters = append(filters, danglingFilterFunc)
+	nets, err := ic.Libpod.Network().NetworkList(filters...)
+	if err != nil {
+		return nil, err
+	}
+
+	pruneReport := make([]*entities.NetworkPruneReport, 0, len(nets))
+	for _, net := range nets {
+		pruneReport = append(pruneReport, &entities.NetworkPruneReport{
+			Name:  net.Name,
+			Error: ic.Libpod.Network().NetworkRemove(net.Name),
+		})
+	}
+	return pruneReport, nil
+}
+
+// danglingFilter function is special and not implemented in libnetwork filters
+func (ic *ContainerEngine) createDanglingFilterFunc(wantDangling bool) (types.FilterFunc, error) {
 	cons, err := ic.Libpod.GetAllContainers()
 	if err != nil {
 		return nil, err
@@ -163,31 +220,12 @@ func (ic *ContainerEngine) NetworkPrune(ctx context.Context, options entities.Ne
 	// ignore the default network, this one cannot be deleted
 	networksToKeep[ic.Libpod.GetDefaultNetworkName()] = true
 
-	// get all filters
-	filters, err := netutil.GenerateNetworkPruneFilters(options.Filters)
-	if err != nil {
-		return nil, err
-	}
-	danglingFilterFunc := func(net types.Network) bool {
+	return func(net types.Network) bool {
 		for network := range networksToKeep {
 			if network == net.Name {
-				return false
+				return !wantDangling
 			}
 		}
-		return true
-	}
-	filters = append(filters, danglingFilterFunc)
-	nets, err := ic.Libpod.Network().NetworkList(filters...)
-	if err != nil {
-		return nil, err
-	}
-
-	pruneReport := make([]*entities.NetworkPruneReport, 0, len(nets))
-	for _, net := range nets {
-		pruneReport = append(pruneReport, &entities.NetworkPruneReport{
-			Name:  net.Name,
-			Error: ic.Libpod.Network().NetworkRemove(net.Name),
-		})
-	}
-	return pruneReport, nil
+		return wantDangling
+	}, nil
 }

test/apiv2/35-networks.at

@@ -78,8 +78,8 @@ t GET networks?filters="{\"id\":[\"$network1_id\"]}" 200 \
   .[0].Name=network1 \
   .[0].Id=$network1_id
 # invalid filter
-t GET networks?filters='{"dangling":["1"]}' 500 \
-  .cause='invalid filter "dangling"'
+t GET networks?filters='{"dangling":["true","0"]}' 500 \
+  .cause="got more than one value for filter key \"dangling\""
 # (#9293 with no networks the endpoint should return empty array instead of null)
 t GET networks?filters='{"name":["doesnotexists"]}' 200 \
   "[]"

test/e2e/network_test.go

@@ -163,6 +163,26 @@ var _ = Describe("Podman network", func() {
 		Expect(session.OutputToString()).To(Not(ContainSubstring(name)))
 	})
 
+	It("podman network list --filter dangling", func() {
+		name, path := generateNetworkConfig(podmanTest)
+		defer removeConf(path)
+
+		session := podmanTest.Podman([]string{"network", "ls", "--filter", "dangling=true"})
+		session.WaitWithDefaultTimeout()
+		Expect(session).Should(Exit(0))
+		Expect(session.OutputToString()).To(ContainSubstring(name))
+
+		session = podmanTest.Podman([]string{"network", "ls", "--filter", "dangling=false"})
+		session.WaitWithDefaultTimeout()
+		Expect(session).Should(Exit(0))
+		Expect(session.OutputToString()).NotTo(ContainSubstring(name))
+
+		session = podmanTest.Podman([]string{"network", "ls", "--filter", "dangling=foo"})
+		session.WaitWithDefaultTimeout()
+		Expect(session).To(ExitWithError())
+		Expect(session.ErrorToString()).To(ContainSubstring(`invalid dangling filter value "foo"`))
+	})
+
 	It("podman network ID test", func() {
 		net := "networkIDTest"
 		// the network id should be the sha256 hash of the network name