add logic for dynamic IP lookup for deltachat links and install #31

app/routes.py

@@ -1,5 +1,6 @@
 import io
 import re
+import socket
 import subprocess
 
 from app import app
@@ -26,6 +27,39 @@ from install_madmail import run_madmail_installer
 CHANGES_REQUIRING_RESTART = ['wifi_password', 'ssid', 'enable_access_point', 'enable_chat', 'enable_delta_chat', 'butterbox_hostname', 'ssh_access_settings', 'root_account_settings', 'root_password']
 RASPAP_INSTALLED = os.path.exists("/var/www/html/raspap")
 
+def resolve_butterbox_ip() -> str:
+    """Best-effort lookup of the address clients should use to reach this box.
+
+    ``BUTTERBOX_DEFAULT_IP`` is only correct while the box serves its own
+    access point. When it's joined to another network its address differs, so
+    try to discover the real one and only fall back to the configured default.
+    """
+    hostname = get_setting('butterbox_hostname') or app.config['BUTTERBOX_HOSTNAME']
+
+    # 1. Resolve the box's own mDNS/.local name. This is the same name the
+    #    DeltaChat link uses for the mail host, so avahi/nss-mdns is present.
+    try:
+        ip = socket.gethostbyname(f"{hostname}.local")
+        if ip and not ip.startswith("127."):
+            return ip
+    except OSError:
+        pass
+
+    # 2. Fall back to the address of the primary outbound interface. The
+    #    connect() picks a route without sending any packets.
+    try:
+        with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as s:
+            s.connect(("8.8.8.8", 80))
+            ip = s.getsockname()[0]
+            if ip and not ip.startswith("127."):
+                return ip
+    except OSError:
+        pass
+
+    # 3. Give up and use the configured access-point default.
+    return app.config['BUTTERBOX_DEFAULT_IP']
+
+
 def gen_username() -> str:
     words = top_n_list("en", 5000)
     prefix = random.randint(1000, 9999)
@@ -370,7 +404,7 @@ def messaging():
 
 @app.route("/deltachat_credentials", methods=["POST"])
 def deltachat_credentials():
-    ip = app.config['BUTTERBOX_DEFAULT_IP']
+    ip = resolve_butterbox_ip()
     username = gen_username()
     password = gen_password()
     hostname = f"{get_setting('butterbox_hostname')}.local"