nebula/overlay/tun_reload_linux_test.go

//go:build !e2e_testing

package overlay

import (
	"net/netip"
	"testing"

	"github.com/slackhq/nebula/config"
	"github.com/slackhq/nebula/routing"
	"github.com/slackhq/nebula/test"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// Only tun.mtu changes. The system calls fail without a real device, what matters is the routes nebula keeps
func TestReloadMTUOnlyKeepsRoutes(t *testing.T) {
	routes := "  unsafe_routes:\n    - route: 192.168.100.0/24\n      via: 10.1.0.1\n"
	c := config.NewC(test.NewLogger())
	require.NoError(t, c.LoadString("tun:\n  mtu: 1300\n"+routes))

	tn := &tun{
		l:                test.NewLogger(),
		vpnNetworks:      []netip.Prefix{netip.MustParsePrefix("10.1.0.2/24")},
		ioctlFd:          ^uintptr(0),
		routesFromSystem: map[netip.Prefix]routing.Gateways{},
	}
	require.NoError(t, tn.reload(c, true))

	require.NoError(t, c.ReloadConfigString("tun:\n  mtu: 1400\n"+routes))
	_ = tn.reload(c, false)

	got := *tn.Routes.Load()
	require.Len(t, got, 1)
	assert.Equal(t, netip.MustParsePrefix("192.168.100.0/24"), got[0].Cidr)
	assert.Equal(t, 1400, got[0].MTU)
	assert.Equal(t, 1400, tn.DefaultMTU)
}

// The device mtu has to fit the largest route mtu, wherever it sits in the list
func TestReloadMaxMTUIsTheLargestRoute(t *testing.T) {
	c := config.NewC(test.NewLogger())
	require.NoError(t, c.LoadString("tun:\n  mtu: 1300\n  unsafe_routes:\n"+
		"    - route: 192.168.100.0/24\n      via: 10.1.0.1\n      mtu: 1500\n"+
		"    - route: 192.168.101.0/24\n      via: 10.1.0.1\n      mtu: 1400\n"))

	tn := &tun{
		l:                test.NewLogger(),
		vpnNetworks:      []netip.Prefix{netip.MustParsePrefix("10.1.0.2/24")},
		ioctlFd:          ^uintptr(0),
		routesFromSystem: map[netip.Prefix]routing.Gateways{},
	}
	require.NoError(t, tn.reload(c, true))
	assert.Equal(t, 1500, tn.MaxMTU)
	assert.Equal(t, 1300, tn.DefaultMTU)
}