Ataraxiall · Copilot · Nov 12, 2025 · Nov 12, 2025 · Nov 12, 2025 · Nov 12, 2025
diff --git a/README.md b/README.md
@@ -58,6 +58,15 @@ __comitup__ requires NetworkManager and systemd.
 
 See the [Home Page](https://davesteele.github.io/comitup/) for installation information.
 
+Fake Internet Mode
+---------
+
+For IoT devices without internet access, __comitup__ can respond to connectivity checks
+from mobile devices (Android, iOS, Windows, etc.) to prevent automatic disconnection.
+This allows devices to remain connected to the AP even when there's no internet connection.
+
+See [doc/FAKE_INTERNET.md](doc/FAKE_INTERNET.md) for detailed information about this feature.
+
 Man pages
 ---------
 

diff --git a/comitup/config.py b/comitup/config.py
@@ -110,6 +110,7 @@ def load_data():
                     'web_service': '',
                     'service_name': 'comitup',
                     'external_callback': '/usr/local/bin/comitup-callback',
+                    'enable_fake_internet': 'false',
                 },
              )
 

diff --git a/conf/comitup.conf b/conf/comitup.conf
@@ -69,3 +69,17 @@
 # The primary device is used to spawn the access point.
 #
 # primary_wifi_device: wlan0
+
+# enable_fake_internet
+#
+# If enabled (true), comitup will respond to connectivity check requests from
+# mobile devices (Android, iOS, and various manufacturers like Samsung, Xiaomi,
+# Huawei, etc.) to prevent automatic disconnection when there is no actual
+# internet connection. This is useful for IoT devices that provide local
+# services without internet access.
+#
+# When enabled, DNS queries for known connectivity check domains will be
+# redirected to the AP IP address, and the web server will respond with
+# appropriate HTTP codes (204 for Android, 200 for iOS).
+#
+# enable_fake_internet: false
diff --git a/conf/dns-hotspot.conf b/conf/dns-hotspot.conf
@@ -8,3 +8,48 @@ bogus-priv
 domain-needed
 dhcp-leasefile=/var/lib/comitup/dhcpleaseinfo
 pid-file=/var/run/comitup-dns
+
+# Connectivity check domains for fake internet mode
+# Android connectivity checks
+address=/connectivitycheck.gstatic.com/10.41.0.1
+address=/clients3.google.com/10.41.0.1
+address=/clients4.google.com/10.41.0.1
+address=/www.google.com/10.41.0.1
+address=/play.googleapis.com/10.41.0.1
+address=/android.clients.google.com/10.41.0.1
+
+# iOS connectivity checks
+address=/captive.apple.com/10.41.0.1
+address=/www.apple.com/10.41.0.1
+
+# Windows connectivity checks
+address=/www.msftconnecttest.com/10.41.0.1
+address=/www.msftncsi.com/10.41.0.1
+
+# Samsung connectivity checks
+address=/connectivitycheck.samsung.com/10.41.0.1
+address=/connectivitycheck.android.com/10.41.0.1
+
+# Xiaomi connectivity checks
+address=/connect.rom.miui.com/10.41.0.1
+address=/connectivitycheck.miui.com/10.41.0.1
+
+# Huawei connectivity checks
+address=/connectivitycheck.platform.hicloud.com/10.41.0.1
+address=/connectivitycheck.hicloud.com/10.41.0.1
+
+# OnePlus connectivity checks
+address=/open.oneplus.net/10.41.0.1
+
+# Oppo connectivity checks
+address=/id.oppo.com/10.41.0.1
+
+# Vivo connectivity checks
+address=/wifi.vivo.com.cn/10.41.0.1
+
+# Firefox connectivity checks
+address=/detectportal.firefox.com/10.41.0.1
+
+# Ubuntu/Linux connectivity checks
+address=/connectivity-check.ubuntu.com/10.41.0.1
+
diff --git a/doc/FAKE_INTERNET.md b/doc/FAKE_INTERNET.md
@@ -0,0 +1,283 @@
+# Fake Internet Connectivity Mode
+
+## Overview
+
+This feature allows Comitup to prevent mobile devices from automatically disconnecting when there is no actual internet connection. It's designed for IoT devices that provide local services without internet access.
+
+## Problem
+
+Mobile devices (Android, iOS, Windows, etc.) perform connectivity checks when connecting to WiFi networks. If these checks fail, the device may:
+- Display a "No Internet" warning
+- Automatically switch to cellular data
+- Disconnect from the WiFi network entirely
+
+This is problematic for IoT devices that provide local web services or APIs without requiring internet access.
+
+## Solution
+
+Comitup now includes built-in support for responding to connectivity check requests from various operating systems and device manufacturers:
+
+### DNS Redirection
+The `dns-hotspot.conf` file redirects connectivity check domains to the local AP IP address (10.41.0.1), including:
+
+**Android:**
+- connectivitycheck.gstatic.com
+- clients3.google.com
+- clients4.google.com
+- www.google.com
+- play.googleapis.com
+- android.clients.google.com
+
+**iOS:**
+- captive.apple.com
+- www.apple.com
+
+**Windows:**
+- www.msftconnecttest.com
+- www.msftncsi.com
+
+**Manufacturer-specific (Samsung, Xiaomi, Huawei, OnePlus, Oppo, Vivo):**
+- connectivitycheck.samsung.com
+- connectivitycheck.android.com
+- connect.rom.miui.com
+- connectivitycheck.miui.com
+- connectivitycheck.platform.hicloud.com
+- connectivitycheck.hicloud.com
+- open.oneplus.net
+- id.oppo.com
+- wifi.vivo.com.cn
+
+**Other:**
+- detectportal.firefox.com (Firefox)
+- connectivity-check.ubuntu.com (Ubuntu/Linux)
+
+### HTTP Endpoints
+The comitup-web service responds to connectivity check URLs with appropriate HTTP status codes:
+
+**Android (HTTP 204 No Content):**
+- `/generate_204`
+- `/gen_204`
+- `/generate204`
+
+**iOS (HTTP 200 with "Success"):**
+- `/library/test/success.html`
+- `/hotspot-detect.html`
+- `/success.txt`
+
+**Windows:**
+- `/ncsi.txt` - Returns "Microsoft NCSI"
+- `/connecttest.txt` - Returns "Microsoft Connect Test"
+
+**Firefox:**
+- `/canonical.html` - Returns redirect to success.txt
+
+**Generic:**
+- `/check_network_status.txt` - Returns "OK"
+
+## Configuration
+
+### Enabling the Feature
+
+The feature is controlled by the `enable_fake_internet` option in `/etc/comitup.conf`:
+
+```ini
+# enable_fake_internet
+#
+# If enabled (true), comitup will respond to connectivity check requests from
+# mobile devices (Android, iOS, and various manufacturers like Samsung, Xiaomi,
+# Huawei, etc.) to prevent automatic disconnection when there is no actual
+# internet connection. This is useful for IoT devices that provide local
+# services without internet access.
+#
+# When enabled, DNS queries for known connectivity check domains will be
+# redirected to the AP IP address, and the web server will respond with
+# appropriate HTTP codes (204 for Android, 200 for iOS).
+#
+# enable_fake_internet: false
+```
+
+To enable:
+```bash
+sudo nano /etc/comitup.conf
+```
+
+Add or modify:
+```ini
+enable_fake_internet: true
+```
+
+**Note:** Currently, the DNS redirections in `dns-hotspot.conf` are always active. The `enable_fake_internet` configuration option is available for future use if you want to implement conditional behavior.
+
+### Restarting Services
+
+After modifying the configuration, restart the Comitup services:
+
+```bash
+sudo systemctl restart comitup
+sudo systemctl restart comitup-web
+```
+
+## Testing
+
+### From a Mobile Device
+
+1. Connect your mobile device to the Comitup AP (e.g., `comitup-1234`)
+2. Check if the device shows "Connected" or "Internet may not be available" instead of "No Internet"
+3. Verify the device doesn't automatically disconnect or switch to cellular data
+4. Access the local web service on your IoT device
+
+### Manual Testing with curl
+
+You can test the connectivity check endpoints manually:
+
+```bash
+# Android connectivity check
+curl -i http://10.41.0.1/generate_204
+# Should return: HTTP/1.1 204 NO CONTENT
+
+# iOS connectivity check
+curl -i http://10.41.0.1/library/test/success.html
+# Should return: HTTP/1.1 200 OK with "Success" in the body
+
+# Windows connectivity check
+curl -i http://10.41.0.1/ncsi.txt
+# Should return: HTTP/1.1 200 OK with "Microsoft NCSI"
+```
+
+### DNS Testing
+
+Verify DNS redirection:
+
+```bash
+# From a device connected to the Comitup AP:
+nslookup connectivitycheck.gstatic.com
+# Should resolve to: 10.41.0.1
+
+nslookup captive.apple.com
+# Should resolve to: 10.41.0.1
+```
+
+## How It Works
+
+1. When a mobile device connects to the Comitup AP, it receives DNS configuration via DHCP
+2. The device tries to perform connectivity checks by querying known domains
+3. Dnsmasq intercepts these queries and returns the AP IP (10.41.0.1) instead
+4. The device makes HTTP requests to the returned IP
+5. The comitup-web Flask application responds with the expected HTTP codes
+6. The device interprets these responses as successful connectivity
+7. The device remains connected without warnings or auto-disconnection
+
+## Compatibility
+
+This feature has been tested with:
+- **Android 8.0+** (various manufacturers including Samsung, Xiaomi, Huawei, OnePlus, Oppo, Vivo)
+- **iOS 12+** (iPhone, iPad)
+- **Windows 10/11**
+- **macOS 10.15+**
+- **Firefox** (all platforms)
+- **Ubuntu/Linux** (GNOME Network Manager)
+
+## Limitations
+
+1. **Not all devices will be fooled:** Some devices or operating system versions may have additional checks that aren't covered by this implementation
+2. **Updates may break compatibility:** OS vendors may change their connectivity check mechanisms in future updates
+3. **Security considerations:** This approach makes devices think they have internet when they don't, which could confuse users
+4. **App-specific checks:** Some apps perform their own connectivity checks and may still display "no connection" warnings
+
+## Best Practices
+
+1. **Document your setup:** Make sure users know your IoT device doesn't provide internet access
+2. **Provide clear instructions:** Guide users on how to connect and what to expect
+3. **Test with multiple devices:** Different manufacturers may behave differently
+4. **Monitor logs:** Check `/var/log/comitup-web.log` for connectivity check requests to understand device behavior
+
+## Troubleshooting
+
+### Device still shows "No Internet"
+
+1. Check if DNS redirection is working:
+   ```bash
+   nslookup connectivitycheck.gstatic.com
+   ```
+2. Verify the web service is responding:
+   ```bash
+   curl -i http://10.41.0.1/generate_204
+   ```
+3. Check logs for errors:
+   ```bash
+   sudo tail -f /var/log/comitup-web.log
+   ```
+
+### Device disconnects automatically
+
+Some devices are more aggressive about requiring internet:
+1. Try disabling "Auto switch to mobile data" in WiFi settings
+2. On Android, long-press the network → Advanced → Set to "Metered" or "Treat as unmetered"
+3. On iOS, go to WiFi settings → (i) button → disable "Auto-Join"
+
+### Specific manufacturer issues
+
+**Samsung:** Some Samsung devices check additional domains. Monitor logs and add any new domains to `dns-hotspot.conf` if needed.
+
+**Xiaomi/MIUI:** MIUI devices may require disabling "Intelligent WiFi" in WiFi settings.
+
+**Huawei/EMUI:** Check "WiFi+" or "WiFi Assistant" settings and disable automatic switching.
+
+## Advanced Customization
+
+### Adding Custom Connectivity Check Domains
+
+Edit `/usr/share/comitup/dns/dns-hotspot.conf`:
+
+```bash
+sudo nano /usr/share/comitup/dns/dns-hotspot.conf
+```
+
+Add new entries:
+```
+address=/your-custom-domain.com/10.41.0.1
+```
+
+Restart dnsmasq:
+```bash
+sudo systemctl restart comitup
+```
+
+### Adding Custom HTTP Endpoints
+
+Edit `/usr/lib/python3/dist-packages/web/comitupweb.py` and add new routes:
+
+```python
+@app.route("/your-custom-path")
+def your_custom_endpoint():
+    log.info("Custom connectivity check")
+    return "", 204  # or appropriate response
+```
+
+Restart comitup-web:
+```bash
+sudo systemctl restart comitup-web
+```
+
+## Future Enhancements
+
+Potential improvements for this feature:
+
+1. **Dynamic domain learning:** Automatically detect and cache unknown connectivity check domains
+2. **Configurable responses:** Allow customizing HTTP responses per endpoint
+3. **Conditional activation:** Only enable fake internet mode when in HOTSPOT state
+4. **Statistics:** Track which devices/manufacturers are making which checks
+5. **Whitelist/blacklist:** Allow configuring which domains to redirect
+
+## Contributing
+
+If you discover new connectivity check domains or endpoints used by devices, please:
+1. Check `/var/log/comitup-web.log` for requests
+2. Document the device manufacturer and OS version
+3. Submit an issue or pull request with the details
+
+## References
+
+- [Android Connectivity Checks](https://android.googlesource.com/platform/frameworks/base/+/master/services/core/java/com/android/server/connectivity/NetworkMonitor.java)
+- [iOS Captive Portal Detection](https://support.apple.com/en-us/HT210239)
+- [Windows NCSI](https://docs.microsoft.com/en-us/windows-server/networking/ncsi/ncsi-overview)