moare fixes

internal/firewall/nftables/input.go

@@ -63,7 +63,7 @@ func (f *Firewall) AcceptInputToPort(_ context.Context, intf string, port uint16
 	}
 
 	table, inputChain, _, _ := setupFilterWithBaseChains(conn)
-	portBytes := []byte{byte(port >> 8), byte(port)} //nolint:mnd
+	portBytes := []byte{byte(port >> 8), byte(port)} //nolint:mnd,gosec // network byte order
 	const tcp, udp uint8 = 6, 17
 	protocols := []uint8{tcp, udp}
 

internal/firewall/nftables/output.go

@@ -215,6 +215,126 @@ func (f *Firewall) AcceptOutputTrafficToVPN(_ context.Context, defaultInterface
 	return nil
 }
 
+func (f *Firewall) AcceptOutput(_ context.Context, protocol, intf string,
+	ip netip.Addr, port uint16, remove bool,
+) error {
+	f.mutex.Lock()
+	defer f.mutex.Unlock()
+
+	conn, err := nftables.New()
+	if err != nil {
+		return fmt.Errorf("creating nftables connection: %w", err)
+	}
+
+	table, _, _, outputChain := setupFilterWithBaseChains(conn)
+
+	const maxExprsLen = 7
+	exprs := make([]expr.Any, 0, maxExprsLen)
+
+	if intf != "" && intf != "*" {
+		exprs = append(exprs,
+			&expr.Meta{Key: expr.MetaKeyOIFNAME, Register: 1},
+			&expr.Cmp{Op: expr.CmpOpEq, Register: 1, Data: []byte(intf + "\x00")},
+		)
+	}
+
+	if ip.Is4() {
+		exprs = append(exprs,
+			&expr.Payload{
+				DestRegister: 1,
+				Base:         expr.PayloadBaseNetworkHeader,
+				Offset:       16, //nolint:mnd
+				Len:          4,  //nolint:mnd
+			},
+			&expr.Cmp{
+				Op:       expr.CmpOpEq,
+				Register: 1,
+				Data:     ip.AsSlice(),
+			},
+		)
+	} else {
+		exprs = append(exprs,
+			&expr.Payload{
+				DestRegister: 1,
+				Base:         expr.PayloadBaseNetworkHeader,
+				Offset:       24, //nolint:mnd
+				Len:          16, //nolint:mnd
+			},
+			&expr.Cmp{
+				Op:       expr.CmpOpEq,
+				Register: 1,
+				Data:     ip.AsSlice(),
+			},
+		)
+	}
+
+	var protocolByte uint8
+	switch protocol {
+	case "tcp":
+		protocolByte = 6
+	case "udp":
+		protocolByte = 17
+	default:
+		return fmt.Errorf("unsupported protocol: %s", protocol)
+	}
+
+	exprs = append(exprs,
+		&expr.Payload{
+			DestRegister: 1,
+			Base:         expr.PayloadBaseTransportHeader,
+			Offset:       3, //nolint:mnd
+			Len:          1,
+		},
+		&expr.Cmp{
+			Op:       expr.CmpOpEq,
+			Register: 1,
+			Data:     []byte{protocolByte},
+		},
+	)
+
+	portBytes := []byte{byte(port >> 8), byte(port)} //nolint:mnd,gosec
+	exprs = append(exprs,
+		&expr.Payload{
+			DestRegister: 1,
+			Base:         expr.PayloadBaseTransportHeader,
+			Offset:       2, //nolint:mnd
+			Len:          2, //nolint:mnd
+		},
+		&expr.Cmp{
+			Op:       expr.CmpOpEq,
+			Register: 1,
+			Data:     portBytes,
+		},
+		&expr.Verdict{Kind: expr.VerdictAccept},
+	)
+
+	rule := &nftables.Rule{
+		Table: table,
+		Chain: outputChain,
+		Exprs: exprs,
+	}
+
+	if !remove {
+		conn.AddRule(rule)
+		f.rules = append(f.rules, rule)
+	} else {
+		err = f.deleteRule(conn, rule)
+		if err != nil {
+			return fmt.Errorf("deleting rule: %w", err)
+		}
+	}
+
+	err = conn.Flush()
+	if err != nil {
+		if !remove {
+			f.rules = f.rules[:len(f.rules)-1]
+		}
+		return fmt.Errorf("flushing: %w", err)
+	}
+
+	return nil
+}
+
 func (f *Firewall) AcceptOutputFromIPPortToIPPort(_ context.Context, protocol, intf string,
 	source, destination netip.AddrPort, remove bool,
 ) error {
@@ -228,7 +348,7 @@ func (f *Firewall) AcceptOutputFromIPPortToIPPort(_ context.Context, protocol, i
 
 	table, _, _, outputChain := setupFilterWithBaseChains(conn)
 
-	const maxExprsLen = 10 //nolint:mnd
+	const maxExprsLen = 10
 	exprs := make([]expr.Any, 0, maxExprsLen)
 
 	if intf != "" && intf != "*" {
@@ -301,11 +421,11 @@ func (f *Firewall) AcceptOutputFromIPPortToIPPort(_ context.Context, protocol, i
 	var protocolByte uint8
 	switch protocol {
 	case "tcp":
-		protocolByte = 6 //nolint:mnd
+		protocolByte = 6
 	case "udp":
-		protocolByte = 17 //nolint:mnd
+		protocolByte = 17
 	default:
-		return fmt.Errorf("unsupported protocol: %s", protocol) //nolint:err113
+		return fmt.Errorf("unsupported protocol: %s", protocol)
 	}
 
 	exprs = append(exprs,
@@ -317,13 +437,13 @@ func (f *Firewall) AcceptOutputFromIPPortToIPPort(_ context.Context, protocol, i
 		},
 	)
 
-	sourcePortBytes := []byte{byte(source.Port() >> 8), byte(source.Port())}                //nolint:mnd
-	destinationPortBytes := []byte{byte(destination.Port() >> 8), byte(destination.Port())} //nolint:mnd
+	sourcePortBytes := []byte{byte(source.Port() >> 8), byte(source.Port())}                //nolint:mnd,gosec
+	destinationPortBytes := []byte{byte(destination.Port() >> 8), byte(destination.Port())} //nolint:mnd,gosec
 	exprs = append(exprs,
 		&expr.Payload{
 			DestRegister: 1,
 			Base:         expr.PayloadBaseTransportHeader,
-			Offset:       0, //nolint:mnd
+			Offset:       0,
 			Len:          2, //nolint:mnd
 		},
 		&expr.Cmp{
@@ -440,7 +560,7 @@ func (f *Firewall) AcceptOutputFromIPToSubnet(_ context.Context, intf string, as
 				DestRegister:   1,
 				Len:            4, //nolint:mnd
 				Mask:           mask,
-				Xor:            []byte{0, 0, 0, 0}, //nolint:mnd
+				Xor:            []byte{0, 0, 0, 0},
 			},
 			&expr.Cmp{
 				Op:       expr.CmpOpEq,
@@ -463,7 +583,7 @@ func (f *Firewall) AcceptOutputFromIPToSubnet(_ context.Context, intf string, as
 				DestRegister:   1,
 				Len:            16, //nolint:mnd
 				Mask:           mask,
-				Xor:            []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, //nolint:mnd
+				Xor:            []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
 			},
 			&expr.Cmp{
 				Op:       expr.CmpOpEq,

internal/firewall/nftables/redirect.go

@@ -42,8 +42,8 @@ func (f *Firewall) RedirectPort(_ context.Context, intf string,
 		Priority: nftables.ChainPriorityNATDest,
 	})
 
-	sourcePortBytes := []byte{byte(sourcePort >> 8), byte(sourcePort)}                //nolint:mnd
-	destinationPortBytes := []byte{byte(destinationPort >> 8), byte(destinationPort)} //nolint:mnd
+	sourcePortBytes := []byte{byte(sourcePort >> 8), byte(sourcePort)}                //nolint:mnd,gosec
+	destinationPortBytes := []byte{byte(destinationPort >> 8), byte(destinationPort)} //nolint:mnd,gosec
 	const tcp, udp uint8 = 6, 17                                                      //nolint:mnd
 	protocols := []uint8{tcp, udp}
 

internal/firewall/nftables/support.go

@@ -33,7 +33,7 @@ func (f *Firewall) Version(ctx context.Context) (string, error) {
 	outputStr := strings.TrimSpace(string(output))
 	words := strings.Fields(outputStr)
 	if len(words) == 0 {
-		return "", errors.New(emptyVersionError) //nolint:err113
+		return "", errors.New(emptyVersionError)
 	}
 	return words[0], nil
 }

internal/firewall/nftables/tcp.go

@@ -94,16 +94,16 @@ func (f *Firewall) TempDropOutputTCPRST(_ context.Context,
 	// Match TCP protocol (6)
 	exprs = append(exprs,
 		&expr.Meta{Key: expr.MetaKeyL4PROTO, Register: 1},
-		&expr.Cmp{Op: expr.CmpOpEq, Register: 1, Data: []byte{6}}, //nolint:mnd
+		&expr.Cmp{Op: expr.CmpOpEq, Register: 1, Data: []byte{6}},
 	)
 
 	// Match source port
-	srcPortBytes := []byte{byte(src.Port() >> 8), byte(src.Port())} //nolint:mnd
+	srcPortBytes := []byte{byte(src.Port() >> 8), byte(src.Port())} //nolint:mnd,gosec // network byte order
 	exprs = append(exprs,
 		&expr.Payload{
 			DestRegister: 1,
 			Base:         expr.PayloadBaseTransportHeader,
-			Offset:       0, //nolint:mnd
+			Offset:       0,
 			Len:          2, //nolint:mnd
 		},
 		&expr.Cmp{
@@ -114,7 +114,7 @@ func (f *Firewall) TempDropOutputTCPRST(_ context.Context,
 	)
 
 	// Match destination port
-	dstPortBytes := []byte{byte(dst.Port() >> 8), byte(dst.Port())} //nolint:mnd
+	dstPortBytes := []byte{byte(dst.Port() >> 8), byte(dst.Port())} //nolint:mnd,gosec // network byte order
 	exprs = append(exprs,
 		&expr.Payload{
 			DestRegister: 1,
@@ -143,12 +143,12 @@ func (f *Firewall) TempDropOutputTCPRST(_ context.Context,
 		&expr.Cmp{
 			Op:       expr.CmpOpEq,
 			Register: 1,
-			Data:     []byte{0x04}, //nolint:mnd
+			Data:     []byte{0x04},
 		},
 	)
 
 	// Exclude packets with the mark using mark != excludeMark
-	markData := []byte{
+	markData := []byte{ //nolint:gosec // mark is int (32-bit), byte conversions are intentional
 		byte(excludeMark), byte(excludeMark >> 8), byte(excludeMark >> 16), byte(excludeMark >> 24), //nolint:mnd
 	}
 	exprs = append(exprs,