Add --me flag to display local and public IPs with CGNAT detection

This commit introduces the --me flag, which allows users to quickly display
their current local IPv4 and public IPv4/IPv6 addresses.

The public IPs are retrieved using ifconfig.me via curl, ensuring accurate
detection even in CGNAT or split-DNS scenarios. Local IPv4 is determined
via the system's active route through the configured resolver.

The output also includes a CGNAT detection based on private IP ranges and
the reserved 100.64.0.0/10 block, providing a helpful warning if detected.

IPv6 privacy extensions are common, so local IPv6 detection has been removed
to avoid redundant or unstable information.

chkip.py

@@ -5,6 +5,7 @@
 chkip.py – DNS- und Mailserver-Check-Tool
 
 Erstellt von Pascal Bouquet am 17.04.2025
+Aktualisiert am 19.04.2025
 
 Dieses Programm ist freie Software: Sie können es unter den Bedingungen der
 GNU General Public License, wie von der Free Software Foundation veröffentlicht,
@@ -20,6 +21,7 @@ Sie sollten eine Kopie der GNU General Public License zusammen mit diesem
 Programm erhalten haben. Falls nicht, siehe <https://www.gnu.org/licenses/>.
 """
 
+
 import sys
 import re
 import ipaddress
@@ -28,6 +30,8 @@ import dns.reversename
 import requests
 import argparse
 import json
+import socket
+import subprocess
 
 # Resolver festlegen
 resolver = dns.resolver.Resolver()
@@ -122,6 +126,43 @@ def resolve_tlsa(domain, mx_host):
     except:
         return "No TLSA record found"
 
+def get_local_ipv4():
+    try:
+        ip = next((ip for ip in resolver.nameservers if '.' in ip), '1.1.1.1')
+        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        s.connect((ip, 80))
+        local_ip = s.getsockname()[0]
+        s.close()
+        return local_ip
+    except:
+        return "unavailable"
+
+def get_my_ip():
+    def run_curl(protocol_flag):
+        try:
+            result = subprocess.run(
+                ["curl", "-s", protocol_flag, "ifconfig.me/ip"],
+                stdout=subprocess.PIPE,
+                stderr=subprocess.DEVNULL,
+                timeout=2,
+                text=True
+            )
+            return result.stdout.strip()
+        except:
+            return "unavailable"
+
+    local_v4 = get_local_ipv4()
+    public_v4 = run_curl("-4")
+    public_v6 = run_curl("-6")
+    return local_v4, public_v4, public_v6
+
+def is_cgnat(ip):
+    try:
+        ip_obj = ipaddress.ip_address(ip)
+        return ip_obj.is_private or ip_obj in ipaddress.ip_network("100.64.0.0/10")
+    except:
+        return False
+
 def print_json(output):
     print(json.dumps(output, indent=2))
 
@@ -165,15 +206,29 @@ def print_text(output, is_ip_mode=False):
 
 def main():
     parser = argparse.ArgumentParser(description="chkip.py – DNS- und Mailserver-Check-Tool")
-    parser.add_argument("domain", help="Domain oder IP-Adresse")
+    parser.add_argument("domain", nargs="?", help="Domain oder IP-Adresse")
     parser.add_argument("-sS", "--spf", action="store_true", help="Prüft den SPF-Eintrag")
     parser.add_argument("-sD", "--dmarc", action="store_true", help="Prüft den DMARC-Eintrag")
     parser.add_argument("-sM", "--mta_sts", action="store_true", help="Prüft den MTA-STS-Eintrag")
     parser.add_argument("-sT", "--tlsa", action="store_true", help="Prüft den TLSA-Eintrag")
     parser.add_argument("-sDK", "--dkim", type=str, help="Prüft den DKIM-Eintrag für den angegebenen Selector")
     parser.add_argument("--json", action="store_true", help="Ausgabe als JSON")
+    parser.add_argument("--me", action="store_true", help="Zeigt lokale & öffentliche IPs und prüft auf CGNAT")
     args = parser.parse_args()
 
+    if args.me:
+        local_v4, public_v4, public_v6 = get_my_ip()
+        print(f"Your local IPv4:  {local_v4}")
+        print(f"Your public IPv4: {public_v4}")
+        print(f"Your public IPv6: {public_v6}")
+        if is_cgnat(public_v4):
+            print("⚠️  Hinweis: Du befindest dich möglicherweise hinter CGNAT (Carrier-Grade NAT)")
+        return
+
+    if not args.domain:
+        parser.print_help()
+        return
+
     domain = args.domain
     is_ip = is_ip_address(domain)
     output = {}
@@ -192,7 +247,7 @@ def main():
             print_json(output)
         else:
             print_text(output, is_ip_mode=True)
-        return  # ✅ wichtig!
+        return
 
     # Domain-Zweig
     output["A"] = resolve_a(domain) or "No A record"