Add GetRuleByHandle, ResetRule & ResetRules methods (#326)

This commit introduces the following methods:

  - GetRuleByHandle
  - ResetRule
  - ResetRules

It also refactors GetRules and the deprecated GetRule methods to share
a common getRules implementation.

nftables_test.go

@@ -7560,3 +7560,229 @@ func TestFlushWithGenID(t *testing.T) {
 		t.Errorf("expected table to not exist, got: %v", table)
 	}
 }
+
+func TestGetRuleByHandle(t *testing.T) {
+	conn, newNS := nftest.OpenSystemConn(t, *enableSysTests)
+	defer nftest.CleanupSystemConn(t, newNS)
+	defer conn.FlushRuleset()
+
+	table := conn.AddTable(&nftables.Table{
+		Name:   "test-table",
+		Family: nftables.TableFamilyIPv4,
+	})
+
+	chain := conn.AddChain(&nftables.Chain{
+		Name:  "test-chain",
+		Table: table,
+	})
+
+	for i := range 3 {
+		conn.AddRule(&nftables.Rule{
+			Table:    table,
+			Chain:    chain,
+			UserData: fmt.Appendf([]byte{}, "rule-%d", i+1),
+			Exprs: []expr.Any{
+				&expr.Verdict{
+					Kind: expr.VerdictAccept,
+				},
+			},
+		})
+	}
+
+	if err := conn.Flush(); err != nil {
+		t.Fatalf("failed to flush: %v", err)
+	}
+
+	rules, err := conn.GetRules(table, chain)
+	if err != nil {
+		t.Fatalf("GetRules failed: %v", err)
+	}
+
+	want := rules[1]
+
+	got, err := conn.GetRuleByHandle(table, chain, want.Handle)
+	if err != nil {
+		t.Fatalf("GetRuleByHandle failed: %v", err)
+	}
+	if !bytes.Equal(got.UserData, want.UserData) {
+		t.Fatalf("expected userdata %q, got %q", got.UserData, want.UserData)
+	}
+}
+
+func TestResetRule(t *testing.T) {
+	conn, newNS := nftest.OpenSystemConn(t, *enableSysTests)
+	defer nftest.CleanupSystemConn(t, newNS)
+	defer conn.FlushRuleset()
+
+	table := conn.AddTable(&nftables.Table{
+		Name:   "test-table",
+		Family: nftables.TableFamilyIPv4,
+	})
+
+	chain := conn.AddChain(&nftables.Chain{
+		Name:  "test-chain",
+		Table: table,
+	})
+
+	tests := [...]struct {
+		Bytes   uint64
+		Packets uint64
+		Reset   bool
+	}{
+		{
+			Bytes:   1024,
+			Packets: 1,
+			Reset:   false,
+		},
+		{
+			Bytes:   2048,
+			Packets: 2,
+			Reset:   true,
+		},
+		{
+			Bytes:   4096,
+			Packets: 4,
+			Reset:   false,
+		},
+	}
+
+	for _, tt := range tests {
+		conn.AddRule(&nftables.Rule{
+			Table: table,
+			Chain: chain,
+			Exprs: []expr.Any{
+				&expr.Counter{
+					Bytes:   tt.Bytes,
+					Packets: tt.Packets,
+				},
+				&expr.Verdict{
+					Kind: expr.VerdictAccept,
+				},
+			},
+		})
+	}
+
+	if err := conn.Flush(); err != nil {
+		t.Fatalf("flush failed: %v", err)
+	}
+
+	rules, err := conn.GetRules(table, chain)
+	if err != nil {
+		t.Fatalf("GetRules failed: %v", err)
+	}
+
+	if len(rules) != len(tests) {
+		t.Fatalf("expected %d rules, got %d", len(tests), len(rules))
+	}
+
+	for i, r := range rules {
+		if !tests[i].Reset {
+			continue
+		}
+		_, err := conn.ResetRule(table, chain, r.Handle)
+		if err != nil {
+			t.Fatalf("ResetRule failed: %v", err)
+		}
+	}
+
+	rules, err = conn.GetRules(table, chain)
+	if err != nil {
+		t.Fatalf("GetRules failed: %v", err)
+	}
+
+	for i, r := range rules {
+		counter, ok := r.Exprs[0].(*expr.Counter)
+		if !ok {
+			t.Errorf("expected first expr to be Counter, got %T", r.Exprs[0])
+		}
+
+		if tests[i].Reset {
+			if counter.Bytes != 0 || counter.Packets != 0 {
+				t.Errorf(
+					"expected counter values to be reset to zero, got Bytes=%d, Packets=%d",
+					counter.Bytes,
+					counter.Packets,
+				)
+			}
+		} else {
+			// Making sure that only the selected rules were reset
+			if counter.Bytes != tests[i].Bytes || counter.Packets != tests[i].Packets {
+				t.Errorf(
+					"unexpected counter values: got Bytes=%d, Packets=%d, want Bytes=%d, Packets=%d",
+					counter.Bytes,
+					counter.Packets,
+					tests[i].Bytes,
+					tests[i].Packets)
+			}
+		}
+	}
+}
+
+func TestResetRules(t *testing.T) {
+	conn, newNS := nftest.OpenSystemConn(t, *enableSysTests)
+	defer nftest.CleanupSystemConn(t, newNS)
+	defer conn.FlushRuleset()
+
+	table := conn.AddTable(&nftables.Table{
+		Name:   "test-table",
+		Family: nftables.TableFamilyIPv4,
+	})
+
+	chain := conn.AddChain(&nftables.Chain{
+		Name:  "test-chain",
+		Table: table,
+	})
+
+	for range 3 {
+		conn.AddRule(&nftables.Rule{
+			Table: table,
+			Chain: chain,
+			Exprs: []expr.Any{
+				&expr.Counter{
+					Bytes:   1,
+					Packets: 1,
+				},
+				&expr.Verdict{
+					Kind: expr.VerdictAccept,
+				},
+			},
+		})
+	}
+
+	if err := conn.Flush(); err != nil {
+		t.Fatalf("flush failed: %v", err)
+	}
+
+	rules, err := conn.GetRules(table, chain)
+	if err != nil {
+		t.Fatalf("GetRules failed: %v", err)
+	}
+
+	if len(rules) != 3 {
+		t.Fatalf("expected %d rules, got %d", 3, len(rules))
+	}
+
+	if _, err := conn.ResetRules(table, chain); err != nil {
+		t.Fatalf("ResetRules failed: %v", err)
+	}
+
+	rules, err = conn.GetRules(table, chain)
+	if err != nil {
+		t.Fatalf("GetRules failed: %v", err)
+	}
+
+	for _, r := range rules {
+		counter, ok := r.Exprs[0].(*expr.Counter)
+		if !ok {
+			t.Errorf("expected first expr to be Counter, got %T", r.Exprs[0])
+		}
+
+		if counter.Bytes != 0 || counter.Packets != 0 {
+			t.Errorf(
+				"expected counter values to be reset to zero, got Bytes=%d, Packets=%d",
+				counter.Bytes,
+				counter.Packets,
+			)
+		}
+	}
+}

rule.go

@@ -71,31 +71,98 @@ type Rule struct {
 
 // GetRule returns the rules in the specified table and chain.
 //
-// Deprecated: use GetRules instead.
+// Deprecated: use GetRuleByHandle instead.
 func (cc *Conn) GetRule(t *Table, c *Chain) ([]*Rule, error) {
 	return cc.GetRules(t, c)
 }
 
+// GetRuleByHandle returns the rule in the specified table and chain by its
+// handle.
+// https://docs.kernel.org/networking/netlink_spec/nftables.html#getrule
+func (cc *Conn) GetRuleByHandle(t *Table, c *Chain, handle uint64) (*Rule, error) {
+	rules, err := cc.getRules(t, c, unix.NFT_MSG_GETRULE, handle)
+	if err != nil {
+		return nil, err
+	}
+
+	if got, want := len(rules), 1; got != want {
+		return nil, fmt.Errorf("expected rule count %d, got %d", want, got)
+	}
+
+	return rules[0], nil
+}
+
 // GetRules returns the rules in the specified table and chain.
 func (cc *Conn) GetRules(t *Table, c *Chain) ([]*Rule, error) {
+	return cc.getRules(t, c, unix.NFT_MSG_GETRULE, 0)
+}
+
+// ResetRule resets the stateful expressions (e.g., counters) of the given
+// rule. The reset is applied immediately (no Flush is required). The returned
+// rule reflects its state prior to the reset. The provided rule must have a
+// valid Handle.
+// https://docs.kernel.org/networking/netlink_spec/nftables.html#getrule-reset
+func (cc *Conn) ResetRule(t *Table, c *Chain, handle uint64) (*Rule, error) {
+	if handle == 0 {
+		return nil, fmt.Errorf("rule must have a valid handle")
+	}
+
+	rules, err := cc.getRules(t, c, unix.NFT_MSG_GETRULE_RESET, handle)
+	if err != nil {
+		return nil, err
+	}
+
+	if got, want := len(rules), 1; got != want {
+		return nil, fmt.Errorf("expected rule count %d, got %d", want, got)
+	}
+
+	return rules[0], nil
+}
+
+// ResetRules resets the stateful expressions (e.g., counters) of all rules
+// in the given table and chain. The reset is applied immediately (no Flush
+// is required). The returned rules reflect their state prior to the reset.
+// state.
+// https://docs.kernel.org/networking/netlink_spec/nftables.html#getrule-reset
+func (cc *Conn) ResetRules(t *Table, c *Chain) ([]*Rule, error) {
+	return cc.getRules(t, c, unix.NFT_MSG_GETRULE_RESET, 0)
+}
+
+// getRules retrieves rules from the given table and chain, using the provided
+// msgType (either unix.NFT_MSG_GETRULE or unix.NFT_MSG_GETRULE_RESET). If the
+// handle is non-zero, the operation applies only to the rule with that handle.
+func (cc *Conn) getRules(t *Table, c *Chain, msgType int, handle uint64) ([]*Rule, error) {
 	conn, closer, err := cc.netlinkConn()
 	if err != nil {
 		return nil, err
 	}
 	defer func() { _ = closer() }()
 
-	data, err := netlink.MarshalAttributes([]netlink.Attribute{
+	attrs := []netlink.Attribute{
 		{Type: unix.NFTA_RULE_TABLE, Data: []byte(t.Name + "\x00")},
 		{Type: unix.NFTA_RULE_CHAIN, Data: []byte(c.Name + "\x00")},
+	}
+
+	var flags netlink.HeaderFlags = netlink.Request | netlink.Acknowledge | netlink.Dump
+
+	if handle != 0 {
+		attrs = append(attrs, netlink.Attribute{
+			Type: unix.NFTA_RULE_HANDLE,
+			Data: binaryutil.BigEndian.PutUint64(handle),
 		})
+
+		flags = netlink.Request | netlink.Acknowledge
+	}
+
+	data, err := netlink.MarshalAttributes(attrs)
 	if err != nil {
 		return nil, err
 	}
 
 	message := netlink.Message{
 		Header: netlink.Header{
-			Type:  netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | unix.NFT_MSG_GETRULE),
+			Type:  netlink.HeaderType((unix.NFNL_SUBSYS_NFTABLES << 8) | msgType),
-			Flags: netlink.Request | netlink.Acknowledge | netlink.Dump,
+			Flags: flags,
 		},
 		Data: append(extraHeader(uint8(t.Family), 0), data...),
 	}