Pass a canonical subnet to ipallocator

- Currently both network and host bits in the subnet are passed
  when requesting an address from ipallocator.
  The way ip allocator determines the first available
  IP is tainted when caller passes the subnet host bits.

- Verified this patch applied to libnetwork vendored in docker
  fixes the issue when starting the daemon.

- Fixes #287

Signed-off-by: Alessandro Boch <aboch@docker.com>

libnetwork/drivers/bridge/bridge.go

@@ -877,7 +877,9 @@ func (d *driver) CreateEndpoint(nid, eid types.UUID, epInfo driverapi.EndpointIn
 	}
 
 	// v4 address for the sandbox side pipe interface
-	ip4, err := ipAllocator.RequestIP(n.bridge.bridgeIPv4, nil)
+	sub := types.GetIPNetCopy(n.bridge.bridgeIPv4)
+	sub.IP = sub.IP.Mask(sub.Mask)
+	ip4, err := ipAllocator.RequestIP(sub, nil)
 	if err != nil {
 		return err
 	}

libnetwork/drivers/bridge/bridge_test.go

@@ -23,11 +23,21 @@ func TestCreateFullOptions(t *testing.T) {
 		EnableIPForwarding: true,
 	}
 
+	// Test this scenario: Default gw address does not belong to
+	// container network and it's greater than bridge address
+	cip, cnw, _ := net.ParseCIDR("172.16.122.0/24")
+	cnw.IP = cip
+	ip, nw, _ := net.ParseCIDR("172.16.0.10/16")
+	nw.IP = ip
+	gw := net.ParseIP("172.16.0.1")
+
 	netConfig := &networkConfiguration{
-		BridgeName:     DefaultBridgeName,
-		EnableIPv6:     true,
-		FixedCIDR:      bridgeNetworks[0],
-		EnableIPTables: true,
+		BridgeName:         DefaultBridgeName,
+		AddressIPv4:        nw,
+		FixedCIDR:          cnw,
+		DefaultGatewayIPv4: gw,
+		EnableIPv6:         true,
+		EnableIPTables:     true,
 	}
 	_, netConfig.FixedCIDRv6, _ = net.ParseCIDR("2001:db8::/48")
 	genericOption := make(map[string]interface{})

libnetwork/drivers/bridge/setup_ipv4.go

@@ -8,6 +8,7 @@ import (
 
 	log "github.com/Sirupsen/logrus"
 	"github.com/docker/libnetwork/netutils"
+	"github.com/docker/libnetwork/types"
 	"github.com/vishvananda/netlink"
 )
 
@@ -109,7 +110,11 @@ func setupGatewayIPv4(config *networkConfiguration, i *bridgeInterface) error {
 	if !i.bridgeIPv4.Contains(config.DefaultGatewayIPv4) {
 		return &ErrInvalidGateway{}
 	}
-	if _, err := ipAllocator.RequestIP(i.bridgeIPv4, config.DefaultGatewayIPv4); err != nil {
+
+	// Pass the real network subnet to ip allocator (no host bits set)
+	sub := types.GetIPNetCopy(i.bridgeIPv4)
+	sub.IP = sub.IP.Mask(sub.Mask)
+	if _, err := ipAllocator.RequestIP(sub, config.DefaultGatewayIPv4); err != nil {
 		return err
 	}