@@ -190,26 +190,19 @@ func (sb *Sandbox) getGatewayEndpoint() (ep4, ep6 *Endpoint) {

 			continue

 		}

 		gw4, gw6 := ep.hasGatewayOrDefaultRoute()

-		if gw4 && gw6 {

-			// The first dual-stack endpoint is the gateway, no need to search further.

-			//

-			// FIXME(robmry) - this means a dual-stack gateway is preferred over single-stack

-			// gateways with higher gateway-priorities. A dual-stack network should probably

-			// be preferred over two single-stack networks, if they all have equal priorities.

-			// It'd probably also be better to use a dual-stack endpoint as the gateway for

-			// a single address family, if there's a higher-priority single-stack gateway for

-			// the other address family. (But, priority is currently a Sandbox property, not

-			// an Endpoint property. So, this function doesn't have access to priorities.)

-			return ep, ep

-		}

 		if gw4 && ep4 == nil {

-			// Found the best IPv4-only gateway, keep searching for an IPv6 or dual-stack gateway.

+			// Endpoints are already sorted according to Endpoint.Less(). The

+			// first endpoint with IPv4 connectivity is the IPv4 gateway.

 			ep4 = ep

 		}

 		if gw6 && ep6 == nil {

-			// Found the best IPv6-only gateway, keep searching for an IPv4 or dual-stack gateway.

+			// The first endpoint with IPv6 connectivity is the IPv6 gateway.

 			ep6 = ep

 		}

+		if ep4 != nil && ep6 != nil {

+			// Found both; we're done.

+			break

+		}

 	}

 	return ep4, ep6

 }

@@ -206,6 +206,51 @@ func TestSandboxAddMultiPrio(t *testing.T) {

 	}

 }

+func TestGatewayEndpointRespectsPriorityPerAddressFamily(t *testing.T) {

+	defer netnsutils.SetupTestOSContext(t)()

+	ctx := t.Context()

+

+	opts := [][]NetworkOption{

+		{

+			NetworkOptionEnableIPv4(true),

+			NetworkOptionEnableIPv6(true),

+			NetworkOptionIpam(defaultipam.DriverName, "",

+				[]*IpamConf{{PreferredPool: "172.30.0.0/24", Gateway: "172.30.0.1"}},

+				[]*IpamConf{{PreferredPool: "fe90::/64", Gateway: "fe90::1"}}, nil),

+		},

+		{

+			NetworkOptionEnableIPv4(true),

+			NetworkOptionIpam(defaultipam.DriverName, "",

+				[]*IpamConf{{PreferredPool: "172.31.0.0/24", Gateway: "172.31.0.1"}},

+				nil, nil),

+		},

+	}

+

+	ctrlr, nws := getTestEnv(t, opts...)

+

+	sbx, err := ctrlr.NewSandbox(ctx, "sandbox-prio-per-family")

+	assert.NilError(t, err)

+

+	epDual, err := nws[0].CreateEndpoint(ctx, "ep-dual")

+	assert.NilError(t, err)

+	epV4, err := nws[1].CreateEndpoint(ctx, "ep-v4")

+	assert.NilError(t, err)

+

+	err = epDual.Join(ctx, sbx)

+	assert.NilError(t, err)

+	err = epV4.Join(ctx, sbx, JoinOptionPriority(1000))

+	assert.NilError(t, err)

+

+	gwep4, gwep6 := sbx.getGatewayEndpoint()

+	assert.Assert(t, gwep4 != nil)

+	assert.Assert(t, gwep6 != nil)

+	assert.Check(t, is.Equal(gwep4.ID(), epV4.ID()))

+	assert.Check(t, is.Equal(gwep6.ID(), epDual.ID()))

+

+	err = sbx.Delete(ctx)

+	assert.NilError(t, err)

+}

+

 func TestSandboxAddSamePrio(t *testing.T) {

 	defer netnsutils.SetupTestOSContext(t)()