Add ipadm: Go-Tool zur Verwaltung statischer DHCP/DNS-Hosts

tools/ipadm/host.go

@@ -0,0 +1,143 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"sort"
+	"strings"
+	"syscall"
+)
+
+// Host is one static host entry: hostname, IP, optional MAC, free-text comment.
+type Host struct {
+	Name    string
+	IP      string
+	MAC     string // "" if not set
+	Comment string
+}
+
+// Store gives locked read-modify-write access to the flat-file host database.
+// One line per host, tab-separated: name\tip\tmac\tcomment
+// MAC is stored as "-" when empty. Lines starting with '#' and blank lines are ignored.
+type Store struct {
+	path string
+	file *os.File
+}
+
+func openStore(path string) (*Store, error) {
+	if err := os.MkdirAll(dirOf(path), 0755); err != nil {
+		return nil, fmt.Errorf("kann Verzeichnis für %s nicht anlegen: %w", path, err)
+	}
+	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0644)
+	if err != nil {
+		return nil, fmt.Errorf("kann %s nicht öffnen: %w", path, err)
+	}
+	if err := syscall.Flock(int(f.Fd()), syscall.LOCK_EX); err != nil {
+		f.Close()
+		return nil, fmt.Errorf("kann Lock auf %s nicht setzen: %w", path, err)
+	}
+	return &Store{path: path, file: f}, nil
+}
+
+func (s *Store) Close() error {
+	syscall.Flock(int(s.file.Fd()), syscall.LOCK_UN)
+	return s.file.Close()
+}
+
+func (s *Store) Load() ([]Host, error) {
+	if _, err := s.file.Seek(0, 0); err != nil {
+		return nil, err
+	}
+	var hosts []Host
+	sc := bufio.NewScanner(s.file)
+	lineNo := 0
+	for sc.Scan() {
+		lineNo++
+		line := strings.TrimRight(sc.Text(), "\r\n")
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		parts := strings.SplitN(line, "\t", 4)
+		if len(parts) < 3 {
+			return nil, fmt.Errorf("%s:%d: ungültige Zeile (erwarte mind. 3 Tab-getrennte Felder): %q", s.path, lineNo, line)
+		}
+		mac := parts[2]
+		if mac == "-" {
+			mac = ""
+		}
+		comment := ""
+		if len(parts) == 4 {
+			comment = parts[3]
+		}
+		hosts = append(hosts, Host{Name: parts[0], IP: parts[1], MAC: mac, Comment: comment})
+	}
+	if err := sc.Err(); err != nil {
+		return nil, err
+	}
+	return hosts, nil
+}
+
+func (s *Store) Save(hosts []Host) error {
+	sort.Slice(hosts, func(i, j int) bool {
+		return strings.ToLower(hosts[i].Name) < strings.ToLower(hosts[j].Name)
+	})
+	var b strings.Builder
+	b.WriteString("# ipadm host database - managed with `ipadm`, do not edit while ipadm is running\n")
+	b.WriteString("# name\tip\tmac\tcomment\n")
+	for _, h := range hosts {
+		mac := h.MAC
+		if mac == "" {
+			mac = "-"
+		}
+		fmt.Fprintf(&b, "%s\t%s\t%s\t%s\n", h.Name, h.IP, mac, h.Comment)
+	}
+	if err := s.file.Truncate(0); err != nil {
+		return err
+	}
+	if _, err := s.file.Seek(0, 0); err != nil {
+		return err
+	}
+	if _, err := s.file.WriteString(b.String()); err != nil {
+		return err
+	}
+	return s.file.Sync()
+}
+
+func dirOf(path string) string {
+	i := strings.LastIndexByte(path, '/')
+	if i <= 0 {
+		return "."
+	}
+	return path[:i]
+}
+
+func findHost(hosts []Host, name string) int {
+	for i, h := range hosts {
+		if strings.EqualFold(h.Name, name) {
+			return i
+		}
+	}
+	return -1
+}
+
+func findByIP(hosts []Host, ip string, exceptIdx int) int {
+	for i, h := range hosts {
+		if i != exceptIdx && h.IP == ip {
+			return i
+		}
+	}
+	return -1
+}
+
+func findByMAC(hosts []Host, mac string, exceptIdx int) int {
+	if mac == "" {
+		return -1
+	}
+	for i, h := range hosts {
+		if i != exceptIdx && h.MAC != "" && strings.EqualFold(h.MAC, mac) {
+			return i
+		}
+	}
+	return -1
+}