libnetwork/netavark: allow same subnet with different vlan

When a vlan is used there should be no subnet conflict check. As the
vlan separates the routing it should be valid.

Fixes: containers/podman#25736

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

Author: Luap99

libnetwork/netavark/config.go

@@ -185,6 +185,10 @@ func (n *netavarkNetwork) networkCreate(newNetwork *types.Network, defaultNet bo
 				if err != nil {
 					return nil, err
 				}
+				// Unset used networks here to ensure that when using vlan networks
+				// we do not error if the subnet is already in use on the host.
+				// https://github.com/containers/podman/issues/25736
+				usedNetworks = nil
 				// If there is no vlan there should be no other config with the same bridge.
 				// However with vlan we want to allow that so that you can have different
 				// configs on the same bridge but different vlans

libnetwork/netavark/config_test.go

@@ -957,6 +957,28 @@ var _ = Describe("Config", func() {
 			Expect(network2.Options).To(HaveKeyWithValue("vlan", "99"))
 		})
 
+		It("create two networks with vlan option and same subnet", func() {
+			subnet := "10.0.0.0/24"
+			n, _ := types.ParseCIDR(subnet)
+			networkOpts := types.Network{
+				Subnets: []types.Subnet{{Subnet: n}},
+			}
+			network1, err := libpodNet.NetworkCreate(networkOpts, nil)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(network1.Driver).To(Equal("bridge"))
+			Expect(network1.Subnets).To(HaveLen(1))
+
+			// set a new vlan on the options
+			networkOpts.Options = map[string]string{types.VLANOption: "99"}
+
+			network2, err := libpodNet.NetworkCreate(networkOpts, nil)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(network2.Driver).To(Equal("bridge"))
+			Expect(network2.Options).To(HaveKeyWithValue("vlan", "99"))
+			Expect(network2.Subnets).To(HaveLen(1))
+			Expect(network2.Subnets).To(Equal(network1.Subnets))
+		})
+
 		It("create network with vrf option", func() {
 			network := types.Network{
 				Options: map[string]string{