Preserve canonical Linux subnet CIDR in default network

Author: cursoragent

lib/network/bridge_linux.go

@@ -1094,13 +1094,25 @@ func (m *manager) queryNetworkState(bridgeName string) (*Network, error) {
 
 	// Bridge existence plus an IPv4 address is sufficient. OperState may be
 	// OperUp or OperUnknown; both are functional for this bridge.
+	subnet := canonicalSubnetCIDR(gatewayAddr.IPNet)
 	return &Network{
 		Bridge:  bridgeName,
 		Gateway: gatewayAddr.IP.String(),
-		Subnet:  gatewayAddr.IPNet.String(),
+		Subnet:  subnet,
 	}, nil
 }
 
+func canonicalSubnetCIDR(ipNet *net.IPNet) string {
+	if ipNet == nil {
+		return ""
+	}
+
+	return (&net.IPNet{
+		IP:   ipNet.IP.Mask(ipNet.Mask),
+		Mask: ipNet.Mask,
+	}).String()
+}
+
 func selectBridgeGatewayAddr(addrs []netlink.Addr, preferredGateway net.IP) netlink.Addr {
 	for _, addr := range addrs {
 		if addr.IP.Equal(preferredGateway) {

lib/network/default_network_linux_test.go

@@ -55,6 +55,15 @@ func TestSelectBridgeGatewayAddrPrefersConfiguredGateway(t *testing.T) {
 	assert.Equal(t, "10.123.0.1", selected.IP.String())
 }
 
+func TestCanonicalSubnetCIDRUsesNetworkAddress(t *testing.T) {
+	subnet := canonicalSubnetCIDR(&net.IPNet{
+		IP:   net.ParseIP("10.123.0.1"),
+		Mask: net.CIDRMask(16, 32),
+	})
+
+	assert.Equal(t, "10.123.0.0/16", subnet)
+}
+
 func TestGetDefaultNetworkPreservesLookupError(t *testing.T) {
 	cfg := &config.Config{
 		Network: config.NetworkConfig{BridgeName: "hypeman-no-such-bridge"},