Always add the default gateway to the cni config file

`podman network create` should always add a gateway to the cni config.
If no gateway is given use the first ip in the subnet. CNI does not require
the gateway field but we need it because of network inspect.

This worked with previous version but was dropped in Commit(e7a72d72fd).

Fixes #8748

Signed-off-by: Paul Holzinger <paul.holzinger@web.de>

libpod/network/netconflist.go

@@ -95,6 +95,10 @@ func NewIPAMLocalHostRange(subnet *net.IPNet, ipRange *net.IPNet, gw net.IP) ([]
 	}
 	if gw != nil {
 		hostRange.Gateway = gw.String()
+	} else {
+		// Add first ip in subnet as gateway. It is not required
+		// by cni but should be included because of network inspect.
+		hostRange.Gateway = CalcGatewayIP(subnet).String()
 	}
 	ranges = append(ranges, hostRange)
 	return ranges, nil

libpod/network/netconflist_test.go

@@ -51,7 +51,8 @@ func TestNewIPAMLocalHostRange(t *testing.T) {
 			subnet: &net.IPNet{IP: net.IPv4(192, 168, 0, 0), Mask: net.IPv4Mask(255, 255, 255, 0)},
 			want: []IPAMLocalHostRangeConf{
 				{
-					Subnet: "192.168.0.0/24",
+					Subnet:  "192.168.0.0/24",
+					Gateway: "192.168.0.1",
 				},
 			},
 		},
@@ -74,7 +75,8 @@ func TestNewIPAMLocalHostRange(t *testing.T) {
 			subnet: &net.IPNet{IP: net.ParseIP("2001:DB8::"), Mask: net.IPMask(net.ParseIP("ffff:ffff:ffff::"))},
 			want: []IPAMLocalHostRangeConf{
 				{
-					Subnet: "2001:db8::/48",
+					Subnet:  "2001:db8::/48",
+					Gateway: "2001:db8::1",
 				},
 			},
 		},

test/e2e/network_create_test.go

@@ -106,6 +106,7 @@ var _ = Describe("Podman network create", func() {
 		Expect(bridgePlugin.IPAM.Routes[0].Dest).To(Equal("0.0.0.0/0"))
 		Expect(bridgePlugin.IsGW).To(BeTrue())
 		Expect(bridgePlugin.IPMasq).To(BeTrue())
+		Expect(bridgePlugin.IPAM.Ranges[0][0].Gateway).ToNot(BeEmpty())
 		Expect(portMapPlugin.Capabilities["portMappings"]).To(BeTrue())
 
 	})
@@ -153,6 +154,8 @@ var _ = Describe("Podman network create", func() {
 		// JSON the bridge info
 		bridgePlugin, err := genericPluginsToBridge(result["plugins"], "bridge")
 		Expect(err).To(BeNil())
+		// check that gateway is added to config
+		Expect(bridgePlugin.IPAM.Ranges[0][0].Gateway).To(Equal("10.11.12.1"))
 
 		// Once a container executes a new network, the nic will be created. We should clean those up
 		// best we can