Refactor table management to use a dedicated API and improve command handling.

internal/command/command.go

@@ -0,0 +1,37 @@
+package command
+
+import (
+	"errors"
+	"os/exec"
+)
+
+type NFT interface {
+	Run(arg ...string) error
+}
+
+type execNFT struct {
+	nftPath string
+}
+
+func New(path string) (NFT, error) {
+	if err := checkingNFT(path); err != nil {
+		return nil, err
+	}
+
+	return &execNFT{
+		nftPath: path,
+	}, nil
+}
+
+func (r *execNFT) Run(arg ...string) error {
+	cmd := exec.Command(r.nftPath, arg...)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		if len(out) > 0 {
+			return errors.New(string(out))
+		}
+		return err
+	}
+
+	return nil
+}

internal/command/utils.go

@@ -0,0 +1,51 @@
+package command
+
+import (
+	"errors"
+	"fmt"
+	"os/exec"
+	"regexp"
+	"strings"
+)
+
+func checkingNFT(path string) error {
+	if path == "" {
+		return errors.New("path is empty")
+	}
+
+	cmd := exec.Command(path, "-V")
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return errors.New("nftables not found")
+	}
+
+	lines := regexp.MustCompile("\r?\n").Split(strings.TrimSpace(string(out)), -1)
+	json := false
+	for index, line := range lines {
+		line = strings.TrimSpace(line)
+
+		if index == 0 {
+			if !strings.HasPrefix(line, "nftables") {
+				return errors.New("nftables not found")
+			}
+			continue
+		}
+
+		if strings.HasPrefix(line, "json:") && strings.HasSuffix(line, "yes") {
+			json = true
+		}
+	}
+
+	if !json {
+		return errors.New("nftables disabled json")
+	}
+
+	cmd = exec.Command(path, "list", "ruleset")
+	out, err = cmd.CombinedOutput()
+
+	if err != nil {
+		return fmt.Errorf("nftables is not available or not supported by the kernel: %s", string(out))
+	}
+
+	return nil
+}

internal/table/table.go

@@ -0,0 +1,51 @@
+package table
+
+import (
+	"git.kor-elf.net/kor-elf-shield/go-nftables-client/family"
+	"git.kor-elf.net/kor-elf-shield/go-nftables-client/internal/command"
+)
+
+type API interface {
+	// AddTable adds a new table.
+	//
+	// This command is equivalent to:
+	//     nft add table (ip|ip6|inet|arp|bridge) {table_name}
+	Add(family family.Type, tableName string) error
+
+	// DeleteTable deletes a table.
+	//
+	// This command is equivalent to:
+	//     nft delete table (ip|ip6|inet|arp|bridge) {table_name}
+	Delete(family family.Type, tableName string) error
+
+	// ClearTable clears all rules in a table.
+	//
+	// This command is equivalent to:
+	//     nft flush table (ip|ip6|inet|arp|bridge) {table_name}
+	Clear(family family.Type, tableName string) error
+}
+
+type table struct {
+	command command.NFT
+}
+
+func New(command command.NFT) API {
+	return &table{
+		command: command,
+	}
+}
+
+func (t *table) Add(family family.Type, tableName string) error {
+	args := []string{"add", "table", family.String(), tableName}
+	return t.command.Run(args...)
+}
+
+func (t *table) Delete(family family.Type, tableName string) error {
+	args := []string{"delete", "table", family.String(), tableName}
+	return t.command.Run(args...)
+}
+
+func (t *table) Clear(family family.Type, tableName string) error {
+	args := []string{"flush", "table", family.String(), tableName}
+	return t.command.Run(args...)
+}