Remove partial userspace firewall mode and open foreign chains via a table-less allower

client/firewall/nftables/interface_allower_integration_linux_test.go

@@ -0,0 +1,90 @@
+//go:build integration && !android
+
+package nftables
+
+import (
+	"bytes"
+	"os"
+	"testing"
+
+	"github.com/google/nftables"
+	"github.com/stretchr/testify/require"
+
+	"github.com/netbirdio/netbird/client/iface"
+)
+
+// TestInterfaceAllowerInputOnly verifies the userspace-mode allower opens the
+// interface on the INPUT hook of foreign chains only (not FORWARD, since the
+// userspace router never forwards in the kernel), creates no netbird work
+// table, and removes its rules on Close.
+func TestInterfaceAllowerInputOnly(t *testing.T) {
+	if os.Geteuid() != 0 {
+		t.Skip("root required")
+	}
+
+	require.False(t, ipTableExists(t, getTableName()), "precondition: no stale netbird table")
+
+	conn := &nftables.Conn{}
+	extTable := conn.AddTable(&nftables.Table{Name: "nbtest_extchains", Family: nftables.TableFamilyINet})
+	inputChain := conn.AddChain(&nftables.Chain{
+		Name: "ext_input", Table: extTable,
+		Hooknum: nftables.ChainHookInput, Priority: nftables.ChainPriorityFilter, Type: nftables.ChainTypeFilter,
+	})
+	forwardChain := conn.AddChain(&nftables.Chain{
+		Name: "ext_forward", Table: extTable,
+		Hooknum: nftables.ChainHookForward, Priority: nftables.ChainPriorityFilter, Type: nftables.ChainTypeFilter,
+	})
+	require.NoError(t, conn.Flush(), "create external table and chains")
+	t.Cleanup(func() {
+		c := &nftables.Conn{}
+		c.DelTable(extTable)
+		_ = c.Flush()
+	})
+
+	allower, err := NewInterfaceAllower(ifaceMock, iface.DefaultMTU)
+	require.NoError(t, err, "create allower")
+	require.NoError(t, allower.Apply(), "apply")
+
+	require.True(t, chainHasUserData(t, extTable, inputChain, userDataAcceptInputRule),
+		"external INPUT chain should get the accept rule")
+	require.Len(t, listRules(t, extTable, forwardChain), 0,
+		"external FORWARD chain must not be opened in userspace mode")
+	require.False(t, ipTableExists(t, getTableName()),
+		"allower must not create a netbird work table")
+
+	require.NoError(t, allower.Close(), "close")
+	require.False(t, chainHasUserData(t, extTable, inputChain, userDataAcceptInputRule),
+		"accept rule should be removed on close")
+}
+
+func listRules(t *testing.T, table *nftables.Table, chain *nftables.Chain) []*nftables.Rule {
+	t.Helper()
+	c := &nftables.Conn{}
+	rules, err := c.GetRules(table, chain)
+	require.NoError(t, err)
+	return rules
+}
+
+func chainHasUserData(t *testing.T, table *nftables.Table, chain *nftables.Chain, ud string) bool {
+	for _, r := range listRules(t, table, chain) {
+		if bytes.Equal(r.UserData, []byte(ud)) {
+			return true
+		}
+	}
+	return false
+}
+
+func ipTableExists(t *testing.T, name string) bool {
+	t.Helper()
+	c := &nftables.Conn{}
+	for _, fam := range []nftables.TableFamily{nftables.TableFamilyIPv4, nftables.TableFamilyIPv6} {
+		tbls, err := c.ListTablesOfFamily(fam)
+		require.NoError(t, err)
+		for _, tb := range tbls {
+			if tb.Name == name {
+				return true
+			}
+		}
+	}
+	return false
+}