dumped that AI-Shitt and rebuild from scratch . works now

src/dhcp_server.py

@@ -1,35 +1,377 @@
+import os
+import socket
+import struct
+import threading
+import time
+import select
+from collections import deque
+from typing import Dict, List, Optional, Tuple
+import ipaddress
+
+
+MAGIC_COOKIE = b"\x63\x82\x53\x63"
+
+# DHCP message types
+DHCPDISCOVER = 1
+DHCPOFFER    = 2
+DHCPREQUEST  = 3
+DHCPDECLINE  = 4
+DHCPACK      = 5
+DHCPNAK      = 6
+DHCPRELEASE  = 7
+DHCPINFORM   = 8
+
+LEASE_SECONDS = 3600  # 1 hour leases
+
+
+def mac_bytes_to_str(b: bytes) -> str:
+    return ":".join(f"{x:02X}" for x in b)
+
+
+def parse_dhcp_options(opts: bytes) -> Dict[int, bytes]:
+    res: Dict[int, bytes] = {}
+    i = 0
+    while i < len(opts):
+        code = opts[i]
+        i += 1
+        if code == 0:  # pad
+            continue
+        if code == 255:  # end
+            break
+        if i >= len(opts):
+            break
+        ln = opts[i]
+        i += 1
+        val = opts[i:i+ln]
+        i += ln
+        res[code] = val
+    return res
+
+
+def build_options(pairs: List[Tuple[int, bytes]]) -> bytes:
+    out = bytearray()
+    out += MAGIC_COOKIE
+    for code, val in pairs:
+        out += bytes([code, len(val)]) + val
+    out += b"\xff"  # END
+    return bytes(out)
+
+
+def ip2bytes(ip: str) -> bytes:
+    return socket.inet_aton(ip)
+
+
+def bytes2ip(b: bytes) -> str:
+    return socket.inet_ntoa(b)
+
+
 class DHCPServer:
-    def __init__(self):
+    """
-        self.leases = {}
+    Minimal functional IPv4 DHCP server for lab/testing.
-        self.active_clients = []
+    - Binds to the specified interface (SO_BINDTODEVICE on Linux).
+    - Listens on UDP/67, answers DISCOVER with OFFER and REQUEST with ACK.
+    - Very simple lease pool carved from start_ip within the interface's subnet.
+    - No persistence; in-memory leases.
+    """
 
-    def start(self, interface, ip_range, subnet):
+    def __init__(self) -> None:
-        # Start the DHCP server on the specified interface
+        self._thread: Optional[threading.Thread] = None
+        self._stop_evt = threading.Event()
+        self._lock = threading.Lock()
+
+        self.interface: Optional[str] = None
+        self.ip_start: Optional[str] = None
+        self.subnet_mask: Optional[str] = None
+        self.server_ip: Optional[str] = None  # inferred from interface IP
+
+        self._leases: Dict[str, Tuple[str, float]] = {}  # MAC -> (IP, expiry_ts)
+        self._active_clients: List[str] = []             # list of MACs
+        self._sock: Optional[socket.socket] = None
+
+        self._pool: List[str] = []  # IP pool
+        self._log = deque(maxlen=500)
+        self._status = "idle"
+
+    # -------------------- Public API --------------------
+    def start(self, interface: str, start_ip: str, mask: str) -> None:
+        if self.is_running():
+            raise RuntimeError("Server is already running.")
+        self.interface = interface
+        self.ip_start = start_ip
+        self.subnet_mask = mask
+
+        # build pool based on interface network
+        self.server_ip = start_ip  # We use the provided IP as "server identifier"; typically you'd use iface IP
+        self._pool = self._build_pool(start_ip, mask)
+
+        self._stop_evt.clear()
+        self._thread = threading.Thread(target=self._run_loop, name="DHCPWorker", daemon=True)
+        self._thread.start()
+
+    def stop(self) -> None:
+        if not self.is_running():
+            return
+        self._stop_evt.set()
+        if self._sock:
+            try:
+                self._sock.close()
+            except Exception:
+                pass
+        if self._thread and self._thread.is_alive():
+            self._thread.join(timeout=3.0)
+        self._thread = None
+        self._sock = None
+        self._set_status("stopped")
+        self._log_line("Server stopped.")
+
+    def is_running(self) -> bool:
+        return self._thread is not None and self._thread.is_alive() and not self._stop_evt.is_set()
+
+    def get_active_clients(self) -> List[str]:
+        with self._lock:
+            return list(self._active_clients)
+
+    def get_leases(self) -> Dict[str, str]:
+        with self._lock:
+            return {mac: ip for mac, (ip, _) in self._leases.items()}
+
+    def get_status(self) -> str:
+        return self._status
+
+    def pop_logs(self, max_items: int = 100) -> List[str]:
+        items: List[str] = []
+        with self._lock:
+            while self._log and len(items) < max_items:
+                items.append(self._log.popleft())
+        return items
+
+    # -------------------- Internals --------------------
+    def _run_loop(self) -> None:
+        try:
+            self._set_status("starting")
+            self._log_line(f"Starting on '{self.interface}' with start {self.ip_start}, mask {self.subnet_mask}")
+            self._sock = self._open_socket(self.interface)
+            self._set_status("running")
+            self._log_line("Listening on UDP/67. WARNING: Requires root privileges.")
+
+            while not self._stop_evt.is_set():
+                r, _, _ = select.select([self._sock], [], [], 0.5)
+                if not r:
+                    self._expire_leases()
+                    continue
+                try:
+                    data, addr = self._sock.recvfrom(4096)
+                except OSError:
+                    break
+                self._handle_packet(data, addr)
+
+        except PermissionError as e:
+            self._set_status("error")
+            self._log_line(f"Permission error (need root?): {e}")
+        except Exception as e:
+            self._set_status("error")
+            self._log_line(f"ERROR: {e!r}")
+        finally:
+            try:
+                if self._sock:
+                    self._sock.close()
+            except Exception:
                 pass
 
-    def stop(self):
+    def _open_socket(self, iface: str) -> socket.socket:
-        # Stop the DHCP server
+        # Basic root check; binding will fail anyway if not root
+        if hasattr(os, "geteuid") and os.geteuid() != 0:
+            raise PermissionError("Root privileges required to bind DHCP server port 67.")
+
+        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        # Make sure we can reuse
+        try:
+            s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        except Exception:
+            pass
+        try:
+            SO_REUSEPORT = getattr(socket, "SO_REUSEPORT", None)
+            if SO_REUSEPORT is not None:
+                s.setsockopt(socket.SOL_SOCKET, SO_REUSEPORT, 1)
+        except Exception:
+            pass
+        try:
+            s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+        except Exception:
             pass
 
-    def handle_request(self, request):
+        # Bind to the specific device (Linux)
-        # Handle incoming DHCP requests
+        try:
+            SO_BINDTODEVICE = 25
+            s.setsockopt(socket.SOL_SOCKET, SO_BINDTODEVICE, iface.encode())
+            self._log_line(f"SO_BINDTODEVICE set to {iface}")
+        except Exception as e:
+            # If not available, better abort to avoid affecting other interfaces
+            s.close()
+            raise PermissionError("SO_BINDTODEVICE not available; cannot restrict to selected interface.") from e
+
+        # Bind to server port
+        s.bind(("0.0.0.0", 67))
+        return s
+
+    def _expire_leases(self) -> None:
+        now = time.time()
+        with self._lock:
+            expired = [mac for mac, (_, t) in self._leases.items() if t <= now]
+            for mac in expired:
+                self._leases.pop(mac, None)
+                if mac in self._active_clients:
+                    self._active_clients.remove(mac)
+
+    def _build_pool(self, start_ip: str, mask: str) -> List[str]:
+        # Build pool from the network containing start_ip with provided mask
+        net = ipaddress.IPv4Network((start_ip, mask), strict=False)
+        all_hosts = list(net.hosts())
+        # Begin at start_ip position (or nearest host) and go upwards, excluding start_ip itself for server identity
+        try:
+            start_idx = all_hosts.index(ipaddress.IPv4Address(start_ip))
+        except ValueError:
+            # pick the first host >= start_ip, else 0
+            start_idx = 0
+            for i, h in enumerate(all_hosts):
+                if int(h) >= int(ipaddress.IPv4Address(start_ip)):
+                    start_idx = i
+                    break
+        pool = [str(h) for h in all_hosts[start_idx:]]
+        # Ensure server_ip isn't handed out
+        if start_ip in pool:
+            pool.remove(start_ip)
+        return pool
+
+    def _next_free_ip(self) -> Optional[str]:
+        with self._lock:
+            used = {ip for ip, _ in self._leases.values()}
+            for ip in self._pool:
+                if ip not in used:
+                    return ip
+        return None
+
+    def _handle_packet(self, data: bytes, addr) -> None:
+        # Basic BOOTP header length check (fixed 236 + cookie 4 -> options after)
+        if len(data) < 240:
+            self._log_line("Drop: packet too short")
+            return
+
+        op, htype, hlen, hops, xid, secs, flags = struct.unpack("!BBBBIHH", data[:12])
+        ciaddr = data[12:16]
+        yiaddr = data[16:20]
+        siaddr = data[20:24]
+        giaddr = data[24:28]
+        chaddr = data[28:44]  # 16 bytes
+        # sname: data[44:108]; file: data[108:236]
+
+        # Options
+        cookie = data[236:240]
+        if cookie != MAGIC_COOKIE:
+            self._log_line("Drop: bad magic cookie")
+            return
+        opts = parse_dhcp_options(data[240:])
+
+        mac = mac_bytes_to_str(chaddr[:hlen])
+        msgtype = opts.get(53, b"\x00")
+        m = msgtype[0] if msgtype else 0
+
+        self._log_line(f"RX {len(data)}B from {addr[0]}:{addr[1]} op={op} mac={mac} type={m}")
+
+        if m == DHCPDISCOVER:
+            self._dhcp_offer(mac, xid, giaddr)
+        elif m == DHCPREQUEST:
+            # honor requested IP (opt 50) if possible, else next free
+            req_ip = opts.get(50, None)
+            ipstr = bytes2ip(req_ip) if req_ip and len(req_ip) == 4 else None
+            self._dhcp_ack(mac, xid, giaddr, requested_ip=ipstr)
+        elif m == DHCPRELEASE:
+            with self._lock:
+                self._leases.pop(mac, None)
+                if mac in self._active_clients:
+                    self._active_clients.remove(mac)
+            self._log_line(f"RELEASE {mac}")
+        else:
+            # ignore other types in this minimal server
             pass
 
-    def add_lease(self, client_ip, client_mac):
+    def _dhcp_offer(self, mac: str, xid: int, giaddr: bytes) -> None:
-        # Add a new lease for a client
+        ip = self._next_free_ip()
-        self.leases[client_mac] = client_ip
+        if not ip:
-        self.active_clients.append(client_mac)
+            self._log_line("No free IP to offer.")
+            return
+        self._log_line(f"OFFER {ip} to {mac}")
+        pkt = self._build_reply_packet(
+            msg_type=DHCPOFFER, mac=mac, xid=xid, yiaddr=ip, giaddr=giaddr
+        )
+        self._send_broadcast(pkt)
 
-    def remove_lease(self, client_mac):
+    def _dhcp_ack(self, mac: str, xid: int, giaddr: bytes, requested_ip: Optional[str]) -> None:
-        # Remove a lease for a client
+        # If requested IP is available or already leased to this MAC, use it; else choose next free
-        if client_mac in self.leases:
+        with self._lock:
-            del self.leases[client_mac]
+            current = self._leases.get(mac, (None, 0))[0]
-            self.active_clients.remove(client_mac)
+        ip = requested_ip or current or self._next_free_ip()
+        if not ip:
+            self._log_line("No IP available for ACK.")
+            return
+        # Register/renew lease
+        expiry = time.time() + LEASE_SECONDS
+        with self._lock:
+            self._leases[mac] = (ip, expiry)
+            if mac not in self._active_clients:
+                self._active_clients.append(mac)
+        self._log_line(f"ACK {ip} to {mac}")
+        pkt = self._build_reply_packet(
+            msg_type=DHCPACK, mac=mac, xid=xid, yiaddr=ip, giaddr=giaddr
+        )
+        self._send_broadcast(pkt)
 
-    def get_active_clients(self):
+    def _build_reply_packet(self, msg_type: int, mac: str, xid: int, yiaddr: str, giaddr: bytes) -> bytes:
-        # Return a list of active clients
+        # BOOTP header
-        return self.active_clients
+        op = 2  # reply
+        htype = 1
+        hlen = 6
+        hops = 0
+        secs = 0
+        flags = 0x0000  # could set broadcast flag if desired
+        ciaddr = b"\x00\x00\x00\x00"
+        yiaddr_b = ip2bytes(yiaddr)
+        siaddr = ip2bytes(self.server_ip or "0.0.0.0")
+        giaddr_b = giaddr if len(giaddr) == 4 else b"\x00\x00\x00\x00"
+        chaddr = bytes.fromhex(mac.replace(":", "")) + b"\x00" * 10  # pad to 16
+        sname = b"\x00" * 64
+        filef = b"\x00" * 128
 
-    def get_leases(self):
+        hdr = struct.pack("!BBBBIHH4s4s4s4s16s64s128s",
-        # Return the current leases
+                          op, htype, hlen, hops, xid, secs, flags,
-        return self.leases
+                          ciaddr, yiaddr_b, siaddr, giaddr_b, chaddr, sname, filef)
+
+        # Options: message type, server id, subnet mask, router (server), lease time
+        options = [
+            (53, bytes([msg_type])),
+            (54, siaddr),  # server identifier
+        ]
+        if self.subnet_mask:
+            options.append((1, ip2bytes(self.subnet_mask)))        # subnet mask
+        if self.server_ip:
+            options.append((3, ip2bytes(self.server_ip)))          # router
+            options.append((6, ip2bytes(self.server_ip)))          # DNS (for lab convenience)
+        options.append((51, struct.pack("!I", LEASE_SECONDS)))     # lease time
+
+        return hdr + build_options(options)
+
+    def _send_broadcast(self, pkt: bytes) -> None:
+        if not self._sock:
+            return
+        try:
+            self._sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+        except Exception:
+            pass
+        self._sock.sendto(pkt, ("255.255.255.255", 68))
+
+    def _log_line(self, msg: str) -> None:
+        with self._lock:
+            self._log.append(time.strftime("[%H:%M:%S] ") + msg)
+
+    def _set_status(self, st: str) -> None:
+        self._status = st

src/gui.py

@@ -1,68 +1,209 @@
-from tkinter import Tk, Label, Button, Entry, StringVar, OptionMenu, Listbox, END
+import os
-import psutil
+import socket
+import tkinter as tk
+from tkinter import messagebox, ttk
+from typing import Optional
+
 from dhcp_server import DHCPServer
+import utils
 
-class DHCPApp:
-    def __init__(self, master):
-        self.master = master
-        master.title("DHCP Server")
 
-        self.interface_label = Label(master, text="Select Network Interface:")
+WARNING_TEXT = (
-        self.interface_label.pack()
+    "ACHTUNG!\n\n"
+    "Ein DHCP-Server im falschen Netz kann massive Störungen verursachen "
+    "(IP-Konflikte, Netzwerkausfall, heilloses Chaos). "
+    "Stelle sicher, dass du auf einem isolierten Testnetz oder dem "
+    "korrekten Interface arbeitest.\n\n"
+    "Willst du den Server wirklich starten?"
+)
 
-        self.interface_var = StringVar(master)
-        self.interfaces = self.get_network_interfaces()
-        self.interface_menu = OptionMenu(master, self.interface_var, *self.interfaces)
-        self.interface_menu.pack()
 
-        self.ip_label = Label(master, text="IP Address:")
+def _preflight_require_root_and_bind(iface: str) -> None:
-        self.ip_label.pack()
+    # Root-Check (nur auf Unix relevant; Windows hat kein geteuid)
-        self.ip_entry = Entry(master)
+    if hasattr(os, "geteuid") and os.geteuid() != 0:
-        self.ip_entry.pack()
+        raise PermissionError("Root-Rechte erforderlich (Port 67).")
 
-        self.subnet_label = Label(master, text="Subnet Mask:")
+    # Bind-Test
-        self.subnet_label.pack()
+    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
-        self.subnet_entry = Entry(master)
+    try:
-        self.subnet_entry.pack()
+        try:
+            s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+            SO_REUSEPORT = getattr(socket, "SO_REUSEPORT", None)
+            if SO_REUSEPORT is not None:
+                s.setsockopt(socket.SOL_SOCKET, SO_REUSEPORT, 1)
+            s.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+        except Exception:
+            pass
 
-        self.start_button = Button(master, text="Start DHCP Server", command=self.start_dhcp_server)
+        # strikt an Interface binden
-        self.start_button.pack()
+        try:
+            SO_BINDTODEVICE = 25
+            s.setsockopt(socket.SOL_SOCKET, SO_BINDTODEVICE, iface.encode())
+        except Exception as e:
+            raise PermissionError("SO_BINDTODEVICE nicht verfügbar – kann nicht exklusiv an Interface binden.") from e
 
-        self.stop_button = Button(master, text="Stop DHCP Server", command=self.stop_dhcp_server)
+        # Port 67 testen
-        self.stop_button.pack()
+        s.bind(("0.0.0.0", 67))
+    finally:
+        try:
+            s.close()
+        except Exception:
+            pass
 
-        self.clients_label = Label(master, text="Active Clients:")
-        self.clients_label.pack()
 
-        self.clients_listbox = Listbox(master)
+class DHCPApp(tk.Frame):
-        self.clients_listbox.pack()
+    def __init__(self, master: tk.Tk) -> None:
+        super().__init__(master)
+        master.title("Simple DHCP Server (Lab)")
+        master.minsize(680, 460)
+        self.pack(fill="both", expand=True, padx=12, pady=12)
 
-        self.dhcp_server = None
+        # Single server instance
+        self.server: Optional[DHCPServer] = None
 
-    def get_network_interfaces(self):
+        # --- Top form ---
-        return psutil.net_if_addrs().keys()
+        form = ttk.Frame(self)
+        form.pack(fill="x", pady=(0, 8))
 
-    def start_dhcp_server(self):
+        ttk.Label(form, text="Interface:").grid(row=0, column=0, sticky="w")
-        ip = self.ip_entry.get()
+        self.if_var = tk.StringVar()
-        subnet = self.subnet_entry.get()
+        self.if_menu = ttk.OptionMenu(form, self.if_var, None, *utils.get_network_interfaces(), command=self.on_iface_change)
-        interface = self.interface_var.get()
+        self.if_menu.grid(row=0, column=1, sticky="ew", padx=(6, 16))
-        self.dhcp_server = DHCPServer(interface, ip, subnet)
-        self.dhcp_server.start()
-        self.update_clients_list()
 
-    def stop_dhcp_server(self):
+        ttk.Label(form, text="Server/Start-IP:").grid(row=0, column=2, sticky="w")
-        if self.dhcp_server:
+        self.ip_var = tk.StringVar(value="")
-            self.dhcp_server.stop()
+        self.ip_entry = ttk.Entry(form, textvariable=self.ip_var, width=16)
-            self.dhcp_server = None
+        self.ip_entry.grid(row=0, column=3, sticky="w", padx=(6, 16))
-            self.clients_listbox.delete(0, END)
 
-    def update_clients_list(self):
+        ttk.Label(form, text="Subnetzmaske:").grid(row=0, column=4, sticky="w")
-        if self.dhcp_server:
+        self.mask_var = tk.StringVar(value="")
-            self.clients_listbox.delete(0, END)
+        self.mask_entry = ttk.Entry(form, textvariable=self.mask_var, width=16)
-            for client in self.dhcp_server.get_active_clients():
+        self.mask_entry.grid(row=0, column=5, sticky="w", padx=(6, 16))
-                self.clients_listbox.insert(END, client)
 
-if __name__ == "__main__":
+        form.columnconfigure(1, weight=1)
-    root = Tk()
+
-    app = DHCPApp(root)
+        # --- Buttons ---
-    root.mainloop()
+        btns = ttk.Frame(self)
+        btns.pack(fill="x", pady=(0, 8))
+        self.btn_start = ttk.Button(btns, text="Start", command=self.start_server)
+        self.btn_stop = ttk.Button(btns, text="Stop", command=self.stop_server, state="disabled")
+        self.btn_start.pack(side="left")
+        self.btn_stop.pack(side="left", padx=(8, 0))
+
+        # --- Clients & Logs Paned Layout ---
+        paned = ttk.Panedwindow(self, orient="horizontal")
+        paned.pack(fill="both", expand=True)
+
+        # Clients list
+        left = ttk.Labelframe(paned, text="Aktive Clients / Leases")
+        self.clients = tk.Listbox(left, height=12)
+        self.clients.pack(fill="both", expand=True, padx=6, pady=6)
+        paned.add(left, weight=1)
+
+        # Logs
+        right = ttk.Labelframe(paned, text="Log")
+        self.log = tk.Text(right, height=12, state="disabled")
+        self.log.pack(fill="both", expand=True, padx=6, pady=6)
+        paned.add(right, weight=2)
+
+        # --- Status bar ---
+        self.status_var = tk.StringVar(value="Bereit.")
+        status = ttk.Label(self, textvariable=self.status_var, anchor="w", relief="sunken")
+        status.pack(fill="x", side="bottom")
+
+        # initial iface autofill (if any interface exists)
+        ifaces = utils.get_network_interfaces()
+        if ifaces:
+            self.if_var.set(ifaces[0])
+            self.on_iface_change(ifaces[0])
+
+        # periodic refresh
+        self.after(400, self._refresh)
+
+    # -------------------- UI logic --------------------
+    def on_iface_change(self, _sel=None):
+        iface = self.if_var.get().strip()
+        ip, mask = utils.get_iface_ipv4_config(iface)
+        if ip:
+            self.ip_var.set(ip)
+        if mask:
+            self.mask_var.set(mask)
+
+    def _set_controls_enabled(self, enabled: bool):
+        state = "normal" if enabled else "disabled"
+        self.if_menu.configure(state=state)
+        self.ip_entry.configure(state=state)
+        self.mask_entry.configure(state=state)
+        self.btn_start.configure(state="normal" if enabled else "disabled")
+        self.btn_stop.configure(state="disabled" if enabled else "normal")
+
+    def start_server(self) -> None:
+        if self.server and self.server.is_running():
+            messagebox.showinfo("Info", "Server läuft bereits.")
+            return
+        # Big fat warning
+        if not messagebox.askyesno("Warnung", WARNING_TEXT, icon="warning"):
+            return
+
+        iface = self.if_var.get().strip()
+        ip = self.ip_var.get().strip()
+        mask = self.mask_var.get().strip()
+        if not iface:
+            messagebox.showerror("Fehler", "Bitte ein Netzwerk-Interface wählen.")
+            return
+        try:
+            ip = utils.format_ip_address(ip)
+            utils.validate_subnet_mask(mask)
+        except Exception as e:
+            messagebox.showerror("Ungültige Eingabe", str(e))
+            return
+
+        # --- Preflight: Root + Bind-Test (SO_BINDTODEVICE) ---
+        try:
+            _preflight_require_root_and_bind(iface)
+        except PermissionError as e:
+            self.status_var.set("Start fehlgeschlagen: Rechte.")
+            messagebox.showerror("Start fehlgeschlagen (Rechte)", f"{e}\n\nBitte mit sudo starten.")
+            return
+        except OSError as e:
+            self.status_var.set("Start fehlgeschlagen: Bind.")
+            messagebox.showerror("Start fehlgeschlagen (Bind)", f"Konnte Port 67 auf {iface} nicht binden:\n{e}")
+            return
+
+        # --- Start ---
+        try:
+            self.server = DHCPServer()
+            self.server.start(iface, ip, mask)
+            self.status_var.set("Server gestartet.")
+            self._set_controls_enabled(False)
+        except Exception as e:
+            self.server = None
+            self.status_var.set("Start fehlgeschlagen.")
+            messagebox.showerror("Start fehlgeschlagen", str(e))
+
+    def stop_server(self) -> None:
+        if self.server:
+            self.server.stop()
+        self._set_controls_enabled(True)
+        self.status_var.set("Server gestoppt.")
+
+    def _append_log(self, lines):
+        if not lines:
+            return
+        self.log.configure(state="normal")
+        for ln in lines:
+            self.log.insert("end", ln + "\n")
+        self.log.see("end")
+        self.log.configure(state="disabled")
+
+    def _refresh(self) -> None:
+        # update clients
+        self.clients.delete(0, "end")
+        if self.server and self.server.is_running():
+            leases = self.server.get_leases()
+            for mac, ip in leases.items():
+                self.clients.insert("end", f"{mac}  →  {ip}")
+            self.status_var.set(f"Status: {self.server.get_status()}")
+            # pull logs
+            self._append_log(self.server.pop_logs(100))
+        self.after(400, self._refresh)

src/main.py

@@ -1,69 +1,16 @@
 import tkinter as tk
-from tkinter import ttk
+from gui import DHCPApp
-from dhcp_server import DHCPServer
-import utils
 
-class DHCPApp:
+def main():
-    def __init__(self, root):
+    root = tk.Tk()
-        self.root = root
+    try:
-        self.root.title("Simple DHCP Server")
+        import sv_ttk  # optional pretty theme
-
+        sv_ttk.use_dark_theme()
-        self.server = None
+    except Exception:
-
+        pass
-        self.interface_label = tk.Label(root, text="Select Network Interface:")
+    app = DHCPApp(root)
-        self.interface_label.grid(row=0, column=0, padx=10, pady=10)
+    root.geometry("860x540")
-
+    root.mainloop()
-        self.interface_var = tk.StringVar()
-        self.interface_dropdown = ttk.Combobox(root, textvariable=self.interface_var)
-        self.interface_dropdown['values'] = utils.get_network_interfaces()
-        self.interface_dropdown.grid(row=0, column=1, padx=10, pady=10)
-
-        self.ip_label = tk.Label(root, text="DHCP IP Range Start:")
-        self.ip_label.grid(row=1, column=0, padx=10, pady=10)
-
-        self.ip_entry = tk.Entry(root)
-        self.ip_entry.grid(row=1, column=1, padx=10, pady=10)
-
-        self.subnet_label = tk.Label(root, text="Subnet Mask:")
-        self.subnet_label.grid(row=2, column=0, padx=10, pady=10)
-
-        self.subnet_entry = tk.Entry(root)
-        self.subnet_entry.grid(row=2, column=1, padx=10, pady=10)
-
-        self.start_button = tk.Button(root, text="Start DHCP Server", command=self.start_server)
-        self.start_button.grid(row=3, column=0, padx=10, pady=10)
-
-        self.stop_button = tk.Button(root, text="Stop DHCP Server", command=self.stop_server)
-        self.stop_button.grid(row=3, column=1, padx=10, pady=10)
-
-        self.clients_label = tk.Label(root, text="Active Clients:")
-        self.clients_label.grid(row=4, column=0, padx=10, pady=10)
-
-        self.clients_listbox = tk.Listbox(root, width=50)
-        self.clients_listbox.grid(row=5, column=0, columnspan=2, padx=10, pady=10)
-
-    def start_server(self):
-        if not self.server:
-            ip_range = self.ip_entry.get()
-            subnet = self.subnet_entry.get()
-            interface = self.interface_var.get()
-            self.server = DHCPServer(interface, ip_range, subnet)
-            self.server.start()
-            self.update_clients()
-
-    def stop_server(self):
-        if self.server:
-            self.server.stop()
-            self.server = None
-            self.clients_listbox.delete(0, tk.END)
-
-    def update_clients(self):
-        if self.server:
-            self.clients_listbox.delete(0, tk.END)
-            for client in self.server.get_active_clients():
-                self.clients_listbox.insert(tk.END, client)
 
 if __name__ == "__main__":
-    root = tk.Tk()
+    main()
-    app = DHCPApp(root)
-    root.mainloop()

src/utils.py

@@ -1,40 +1,33 @@
-def get_available_interfaces():
-    import netifaces
-    return netifaces.interfaces()
-
-def format_ip_address(ip):
-    try:
-        parts = ip.split('.')
-        if len(parts) != 4:
-            raise ValueError("Invalid IP address format")
-        return '.'.join(str(int(part)) for part in parts)
-    except ValueError as e:
-        raise ValueError(f"Error formatting IP address: {e}")
-
-def validate_subnet_mask(mask):
-    valid_masks = [
-        '255.255.255.255', '255.255.255.254', '255.255.255.252',
-        '255.255.255.248', '255.255.255.240', '255.255.255.224',
-        '255.255.255.192', '255.255.255.128', '255.255.255.0',
-        '255.255.254.0', '255.255.252.0', '255.255.248.0',
-        '255.255.240.0', '255.255.224.0', '255.255.192.0',
-        '255.255.128.0', '255.255.0.0', '255.254.0.0',
-        '255.252.0.0', '255.248.0.0', '255.240.0.0',
-        '255.224.0.0', '255.192.0.0', '255.128.0.0',
-        '255.0.0.0', '254.0.0.0', '252.0.0.0',
-        '248.0.0.0', '240.0.0.0', '224.0.0.0',
-        '192.0.0.0', '128.0.0.0', '0.0.0.0'
-    ]
-    if mask not in valid_masks:
-        raise ValueError("Invalid subnet mask")
-
 import socket
+import ipaddress
 import psutil
+from typing import Optional, Tuple
 
 def get_network_interfaces():
+    """Return only interfaces that have an IPv4 address to keep choices sane."""
     interfaces = []
     for iface, addrs in psutil.net_if_addrs().items():
         for addr in addrs:
             if addr.family == socket.AF_INET:
                 interfaces.append(iface)
-    return interfaces
+                break
+    return sorted(interfaces)
+
+def get_iface_ipv4_config(iface: str) -> Tuple[Optional[str], Optional[str]]:
+    """Return (ipv4_addr, netmask) for interface, or (None, None) if not present."""
+    addrs = psutil.net_if_addrs().get(iface, [])
+    for a in addrs:
+        if a.family == socket.AF_INET:
+            return a.address, a.netmask
+    return None, None
+
+def format_ip_address(ip: str) -> str:
+    """Normalize dotted quad; raises on invalid input."""
+    ip_obj = ipaddress.ip_address(ip)
+    if ip_obj.version != 4:
+        raise ValueError("Only IPv4 is supported.")
+    return str(ip_obj)
+
+def validate_subnet_mask(mask: str) -> None:
+    """Accept masks like 255.255.255.0; raise ValueError if invalid."""
+    ipaddress.IPv4Network(f"0.0.0.0/{mask}")