需求：
如果存在用户配置的DNS服务器，则切面拦截运行商下发的DNS,替换为用户自己配置的DNS.
实现：
直接上代码：
1:TelephonyProperties 内新增属性保存用户设置的dns
//QSSI.13/frameworks/base/telephony/java/com/android/internal/telephony/TelephonyProperties.java/*** PROPERTY_SIM_DEFAULT_DNS is to set the default DNS*/static String PROPERTY_SIM_DEFAULT_DNS = "sim.default.dns";
这里我们注意下TelephonyProperties 为接口类，系统未找到相关的实现类，其实此处的用法类似于aidl文件到java文件的转换，是编译脚本进行转换（build/soong/sysprop/sysprop_library.go）
即会将libsysprop目录下的.sysprop文件编译成对应的.jar给系统调用，即会编译为：PlatformProperties.jar，我们可以把以下目录中的源码文件拖到AS看下
目录：QSSI.13\out\soong\.intermediates\system\libsysprop\srcs\PlatformProperties\android_common\javac\PlatformProperties.jar
我们截取部分TelephonyProperties.class代码看下
public static Optional<Boolean> airplane_mode_on() {String value = SystemProperties.get("persist.radio.airplane_mode_on");return Optional.ofNullable(tryParseBoolean(value));
}public static void airplane_mode_on(Boolean value) {SystemProperties.set("persist.radio.airplane_mode_on", value == null ? "" : (value ? "1" : "0"));
}
从这个反编译出来的文件可以看到，实际上就是对SystemProperties做了一层封装。
2：在TelephonyProperties.sysprop 中定义属性
//QSSI.13/system/libsysprop/srcs/android/sysprop/TelephonyProperties.sysprop
# set default dns list
prop {api_name: "sim_default_dns"type: StringListscope: Publicaccess: ReadWriteprop_name: "sim.default.dns"
}
注意我们新增了属性，需要执行如下指令，更新api文件，具体的详见脚本文件：/build/soong/scripts/freeze-sysprop-api-files.sh
m PlatformProperties-dump-api && rm -rf system/libsysprop/srcs/api/PlatformProperties-current.txt && cp -f out/soong/.intermediates/system/libsysprop/srcs/PlatformProperties_sysprop_library/api-dump.txt system/libsysprop/srcs/api/PlatformProperties-current.txt
执行上述指令以后会更新如下文件
//QSSI.13/system/libsysprop/srcs/api/PlatformProperties-current.txt
prop {api_name: "sim_default_dns"type: StringListaccess: ReadWriteprop_name: "sim.default.dns"}
3：我们新增了属性为sim.default.dns，我们还需要增加selinux权限，即为此属性配置上下文,可直接使用之前系统定义好的上下文
//QSSI.13/system/sepolicy/private/property_contexts
sim.default.dns u:object_r:telephony_status_prop:s0 exact string
//QSSI.13/system/sepolicy/prebuilts/api/33.0/private/property_contexts
sim.default.dns u:object_r:telephony_status_prop:s0 exact string
4：经过上述步骤，我们即可在TelephonyManager内对属性sim.default.dns进行读写
//QSSI.13/frameworks/base/telephony/java/android/telephony/TelephonyManager.java/*** Set TelephonyProperties.default_dns for dns.** @hide*/public void setSimDnsServers(int phoneId, String dnsStr) {if (SubscriptionManager.isValidPhoneId(phoneId)) {List<String> newList = new ArrayList();if (!TextUtils.isEmpty(dnsStr)) {List<String> tList = updateTelephonyProperty(TelephonyProperties.sim_default_dns(), phoneId, dnsStr);newList.addAll(tList);}for (int i = 0; i < newList.size(); i++) {Log.e(TAG, "setSimDns...." + newList.get(i));}Log.e(TAG, "setSimDnsList...." + dnsStr + ":" + newList);TelephonyProperties.sim_default_dns(newList);}}/*** get TelephonyProperties.default_dns** @hide*/public String getSimDnsServers(int phoneId) {return getTelephonyProperty(phoneId, TelephonyProperties.sim_default_dns(), "");}
5:我们在建立datacall的时候，就可以读取配置的dns服务器，然后更新,我是在DataNetwork 中处理的，当然也可以在ConnectivityService内处理
//QSSI.13/frameworks/opt/telephony/src/java/com/android/internal/telephony/data/DataNetwork.java/*** Update data network based on the latest {@link DataCallResponse}.** @param response The data call response from data service.*/private void updateDataNetwork(@NonNull DataCallResponse response) {.......//phoebe add for set default dns// Set DNS serversList<InetAddress> defaultDns = getDefaultDns(mPhone.getPhoneId());if (defaultDns != null && defaultDns.size() > 0) {loge("set default dns:" + defaultDns);linkProperties.setDnsServers(defaultDns);} else {if (response.getDnsAddresses().size() > 0) {for (InetAddress dns : response.getDnsAddresses()) {if (!dns.isAnyLocalAddress()) {linkProperties.addDnsServer(dns);}}} else {loge("Empty dns response");}}....}public List<InetAddress> getDefaultDns(int phoneId) {String dnsStr = mTelephonyManager.getSimDnsServers(phoneId);logl("zmm add for getDefaultDns..." + dnsStr);String[] split = TextUtils.isEmpty(dnsStr) ? null : dnsStr.trim().split(",");if (split == null || split.length == 0) {return null;}List<InetAddress> dnsService = new ArrayList<>();try {for (String str : split) {if (!str.trim().isEmpty()) {InetAddress dns = InetAddress.parseNumericAddress(str);logl("zmm add for default dns..." + dns);dnsService.add(dns);}}} catch (Exception e) {e.printStackTrace();loge("zmm add for default dns..." + e.getMessage());}return dnsService;}
6：设置客户自定义的dns,我是在SIMRecords中设置默认的dns的，当然也可在别的地方通过mTelephonyManager.setSimDnsServers()方法设置不同sim卡的不同dns
当然需要再setdatacall建立成功之前，就设置到属性中去。
//QSSI.13/frameworks/opt/telephony/src/java/com/android/internal/telephony/uicc/SIMRecords.java
多个dns服务器用逗号隔开
mTelephonyManager.setSimDnsServers(mPhoneId(), "dns1,dns2");
