add DestroyTable and SetDestroyElements (#322)

These methods are like their DeleteTable and SetDeleteElements counterparts, but they do not return an error if the specified table/set does not exist.

nftables_test.go

@@ -128,6 +128,47 @@ func ifname(n string) []byte {
 	return b
 }
 
+func TestTableCreateDestroy(t *testing.T) {
+	c, newNS := nftest.OpenSystemConn(t, *enableSysTests)
+	defer nftest.CleanupSystemConn(t, newNS)
+	defer c.FlushRuleset()
+
+	filter := &nftables.Table{
+		Family: nftables.TableFamilyIPv4,
+		Name:   "filter",
+	}
+	c.DestroyTable(filter)
+	c.AddTable(filter)
+	err := c.Flush()
+	if err != nil {
+		t.Fatalf("on Flush: %q", err.Error())
+	}
+
+	lookupMyTable := func() bool {
+		ts, err := c.ListTables()
+		if err != nil {
+			t.Fatalf("on ListTables: %q", err.Error())
+		}
+		return slices.ContainsFunc(ts, func(t *nftables.Table) bool {
+			return t.Name == filter.Name && t.Family == filter.Family
+		})
+	}
+	if !lookupMyTable() {
+		t.Fatal("AddTable doesn't create my table!")
+	}
+
+	c.DestroyTable(filter)
+	if err = c.Flush(); err != nil {
+		t.Fatalf("on Flush: %q", err.Error())
+	}
+
+	if lookupMyTable() {
+		t.Fatal("DestroyTable doesn't delete my table!")
+	}
+
+	c.DestroyTable(filter) // just for test that 'destroy' ignore error 'not found'
+}
+
 func TestRuleOperations(t *testing.T) {
 	// Create a new network namespace to test these operations,
 	// and tear down the namespace at test completion.
@@ -3777,7 +3818,7 @@ func TestDeleteElementNamedSet(t *testing.T) {
 		Name:    "test",
 		KeyType: nftables.TypeInetService,
 	}
-	if err := c.AddSet(portSet, []nftables.SetElement{{Key: []byte{0, 22}}, {Key: []byte{0, 23}}}); err != nil {
+	if err := c.AddSet(portSet, []nftables.SetElement{{Key: []byte{0, 22}}, {Key: []byte{0, 23}}, {Key: []byte{0, 24}}}); err != nil {
 		t.Errorf("c.AddSet(portSet) failed: %v", err)
 	}
 	if err := c.Flush(); err != nil {
@@ -3794,6 +3835,22 @@ func TestDeleteElementNamedSet(t *testing.T) {
 	if err != nil {
 		t.Errorf("c.GetSets() failed: %v", err)
 	}
+	if len(elems) != 2 {
+		t.Fatalf("len(elems) = %d, want 2", len(elems))
+	}
+
+	c.SetDestroyElements(portSet, []nftables.SetElement{{Key: []byte{0, 24}}})
+	c.SetDestroyElements(portSet, []nftables.SetElement{{Key: []byte{0, 24}}})
+	c.SetDestroyElements(portSet, []nftables.SetElement{{Key: []byte{0, 99}}})
+
+	if err := c.Flush(); err != nil {
+		t.Errorf("Third c.Flush() failed: %v", err)
+	}
+
+	elems, err = c.GetSetElements(portSet)
+	if err != nil {
+		t.Errorf("c.GetSets() failed: %v", err)
+	}
 	if len(elems) != 1 {
 		t.Fatalf("len(elems) = %d, want 1", len(elems))
 	}

set.go

@@ -44,6 +44,9 @@ const (
 	NFTA_SET_ELEM_KEY_END = 10
 	// https://git.netfilter.org/nftables/tree/include/linux/netfilter/nf_tables.h?id=d1289bff58e1878c3162f574c603da993e29b113#n429
 	NFTA_SET_ELEM_EXPRESSIONS = 0x11
+	// FIXME: in sys@v0.34.0 no unix.NFT_MSG_DESTROYSETELEM const yet.
+	// See nf_tables_msg_types enum in https://git.netfilter.org/nftables/tree/include/linux/netfilter/nf_tables.h
+	NFT_MSG_DESTROYSETELEM = 0x1e
 )
 
 // SetDatatype represents a datatype declared by nft.
@@ -391,6 +394,16 @@ func (cc *Conn) SetDeleteElements(s *Set, vals []SetElement) error {
 	return cc.appendElemList(s, vals, unix.NFT_MSG_DELSETELEM)
 }
 
+// SetDestroyElements like SetDeleteElements, but not an error if setelement doesn't exists
+func (cc *Conn) SetDestroyElements(s *Set, vals []SetElement) error {
+	cc.mu.Lock()
+	defer cc.mu.Unlock()
+	if s.Anonymous {
+		return errors.New("anonymous sets cannot be updated")
+	}
+	return cc.appendElemList(s, vals, NFT_MSG_DESTROYSETELEM)
+}
+
 // maxElemBatchSize is the maximum size in bytes of encoded set elements which
 // are sent in one netlink message. The size field of a netlink attribute is a
 // uint16, and 1024 bytes is more than enough for the per-message headers.
@@ -826,8 +839,9 @@ func parseSetDatatype(magic uint32) (SetDatatype, error) {
 }
 
 const (
-	newElemHeaderType = netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_NEWSETELEM)
-	delElemHeaderType = netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_DELSETELEM)
+	newElemHeaderType     = netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_NEWSETELEM)
+	delElemHeaderType     = netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_DELSETELEM)
+	destroyElemHeaderType = netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | NFT_MSG_DESTROYSETELEM)
 )
 
 func elementsFromMsg(fam byte, msg netlink.Message) ([]SetElement, error) {

table.go

@@ -24,6 +24,10 @@ import (
 const (
 	newTableHeaderType = netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_NEWTABLE)
 	delTableHeaderType = netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_DELTABLE)
+
+	// FIXME: in sys@v0.34.0 no unix.NFT_MSG_DESTROYTABLE const yet.
+	// See nf_tables_msg_types enum in https://git.netfilter.org/nftables/tree/include/linux/netfilter/nf_tables.h
+	destroyTableHeaderType = netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | 0x1a)
 )
 
 // TableFamily specifies the address family for this table.
@@ -51,15 +55,25 @@ type Table struct {
 
 // DelTable deletes a specific table, along with all chains/rules it contains.
 func (cc *Conn) DelTable(t *Table) {
+	cc.delTable(t, delTableHeaderType)
+}
+
+// DestroyTable is like DelTable, but not an error if table doesn't exists
+func (cc *Conn) DestroyTable(t *Table) {
+	cc.delTable(t, destroyTableHeaderType)
+}
+
+func (cc *Conn) delTable(t *Table, hdrType netlink.HeaderType) {
 	cc.mu.Lock()
 	defer cc.mu.Unlock()
 	data := cc.marshalAttr([]netlink.Attribute{
 		{Type: unix.NFTA_TABLE_NAME, Data: []byte(t.Name + "\x00")},
 		{Type: unix.NFTA_TABLE_FLAGS, Data: []byte{0, 0, 0, 0}},
 	})
+
 	cc.messages = append(cc.messages, netlinkMessage{
 		Header: netlink.Header{
-			Type:  netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_DELTABLE),
+			Type:  hdrType,
 			Flags: netlink.Request | netlink.Acknowledge,
 		},
 		Data: append(extraHeader(uint8(t.Family), 0), data...),