如何通过短信下发APN配置及修改Android的apns-full-conf.xml？

Hey there, let's break down how to handle APN configuration delivery via SMS for both iOS and Android, since you mentioned having questions about the Android implementation specifically:

针对iOS的实现 #

iOS supports APN configuration imports via .mobileconfig files (XML-based payloads), which can be delivered via SMS easily:

1. Create a .mobileconfig file with your APN details. Here's a simplified example structure:

   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
   <plist version="1.0">
   <dict>
       <key>PayloadContent</key>
       <array>
           <dict>
               <key>PayloadType</key>
               <string>com.apple.cellular</string>
               <key>PayloadVersion</key>
               <integer>1</integer>
               <key>PayloadIdentifier</key>
               <string>com.yourcompany.apn.carrierxyz</string>
               <key>PayloadUUID</key>
               <string>GENERATE_A_UNIQUE_UUID_HERE</string>
               <key>PayloadDisplayName</key>
               <string>CarrierXYZ APN Settings</string>
               <key>APNs</key>
               <array>
                   <dict>
                       <key>APN</key>
                       <string>carrierxyz</string>
                       <key>CarrierName</key>
                       <string>CarrierXYZ</string>
                       <key>MCC</key>
                       <string>123</string>
                       <key>MNC</key>
                       <string>123</string>
                       <key>MMSEnable</key>
                       <true/>
                       <key>MMSC</key>
                       <string>http://mms.carrierxyz.com</string>
                       <key>MMSProxy</key>
                       <string>0.0.0.0</string>
                       <key>MMSPort</key>
                       <string>80</string>
                       <key>APNType</key>
                       <string>default,supl,mms,ims,cbs</string>
                   </dict>
               </array>
           </dict>
       </array>
       <key>PayloadType</key>
       <string>Configuration</string>
       <key>PayloadVersion</key>
       <integer>1</integer>
       <key>PayloadIdentifier</key>
       <string>com.yourcompany.apn</string>
       <key>PayloadUUID</key>
       <string>ANOTHER_UNIQUE_UUID_HERE</string>
       <key>PayloadDisplayName</key>
       <string>CarrierXYZ APN Setup</string>
       <key>PayloadDescription</key>
       <string>Install this profile to setup CarrierXYZ APN settings.</string>
   </dict>
   </plist>
   

2. Host this .mobileconfig file on a secure server (HTTPS is preferred for iOS trust).
3. Send a SMS to users with a link to the file. When users tap the link, iOS will prompt them to install the profile, which adds the APN configuration automatically (no jailbreak required).

针对Android的实现（核心痛点解决） #

You're correct that /etc/apns-full-conf.xml is a system-level file storing APN configurations, but modifying it requires root access because it's located in the read-only system partition. Here's how to implement this, along with options for SMS delivery:

1. Root-based direct file modification (proven approach, matches your success case) #

If the device is rooted, you can modify the XML file directly:

• Step 1: Backup the original file (critical to avoid breaking connectivity):

  su
  cp /etc/apns-full-conf.xml /etc/apns-full-conf.xml.bak
  

• Step 2: Add your APN entry to the XML file. Insert your provided <apn> node inside the root <apns> tag, alongside existing entries:

  <apn carrier="CarrierXYZ" mcc="123" mnc="123" apn="carrierxyz" type="default,supl,mms,ims,cbs" mmsc="http://mms.carrierxyz.com" mmsproxy="0.0.0.0" mmsport="80" bearer_bitmask="4|5|6|7|8|12" />
  

• Step 3: Fix file permissions to ensure the system can read the modified file:

  chmod 644 /etc/apns-full-conf.xml
  

• Step 4: Apply changes – either reboot the device, or restart the telephony service (requires root):

  am stopservice com.android.phone
  am startservice com.android.phone
  

2. SMS-triggered APN import (for end-users) #

To deliver this via SMS so users can import it automatically:

• Option A (Root required): Build a lightweight app that requests root access. Send an SMS with your APN parameters (or a base64-encoded XML snippet). The app listens for incoming SMS, parses the data, then runs the above commands to modify /etc/apns-full-conf.xml and apply changes.
• Option B (No root, limited compatibility): For non-rooted devices, you'd need an app with the WRITE_APN_SETTINGS permission. However, this is a system-level permission on Android 6.0+ – most devices restrict it to system apps, unless users manually grant it via hidden settings (not user-friendly). If you can get this permission, you can use the ContentResolver to insert the APN directly into the system's APN database:

  ContentResolver resolver = getContentResolver();
  ContentValues values = new ContentValues();
  values.put("carrier", "CarrierXYZ");
  values.put("mcc", "123");
  values.put("mnc", "123");
  values.put("apn", "carrierxyz");
  values.put("type", "default,supl,mms,ims,cbs");
  values.put("mmsc", "http://mms.carrierxyz.com");
  values.put("mmsproxy", "0.0.0.0");
  values.put("mmsport", "80");
  resolver.insert(Uri.parse("content://telephony/carriers"), values);
  

  You could trigger this via SMS by having the app listen for a specific message format, then run the insertion code.

关键注意事项 #

• Android OEM variations: Some manufacturers store APN configurations in a database instead of (or in addition to) /etc/apns-full-conf.xml. To ensure compatibility, after modifying the XML, you should also insert the APN into the content://telephony/carriers content provider (as shown in Option B above) – this ensures the system recognizes the new APN.
• iOS profile signing: To avoid iOS blocking the profile, sign the .mobileconfig file with an Apple Developer certificate. Self-signed certificates work too, but users will need to manually trust the certificate in Settings > General > VPN & Device Management.

内容的提问来源于stack exchange，提问作者Africa Matji