Android系统连接WIFI显示网络连接受限

问题描述

使用Android设备打开设置，选择WIFI输入正确密码连接，会显示已连接，无网络，然后变成网络连接受限，实际可以使用此WIFI进行上网。

问题分析

异常Log

D NetworkMonitor/100: PROBE_DNS www.谷歌.com 107ms OK 104.244.46.85
D NetworkMonitor/100: PROBE_DNS connectivitycheck.gstatic.com 118ms OK 203.208.50.66
D NetworkMonitor/100: PROBE_HTTP http://connectivitycheck.gstatic.com/generate_204 time=35ms ret=302 request={Connection=[close], User-Agent=[Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.32 Safari/537.36]} headers={null=[HTTP/1.0 302 Moved Temporarily], Allow=[GET,POST,HEAD], Location=[http://10.10.1.2:8080/cn/index.html], MIME-Version=[1.0], Pragma=[No-Cache], Server=[AP Server 1.0], X-Android-Received-Millis=[1615220820212], X-Android-Response-Source=[NETWORK 302], X-Android-Selected-Protocol=[http/1.0], X-Android-Sent-Millis=[1615220820196]}
D NetworkMonitor/100: PROBE_HTTPS https://www.谷歌.com/generate_204 Probe failed with exception javax.net.ssl.SSLHandshakeException: java.security.cert.CertPathValidatorException: Trust anchor for certification path not found.
D NetworkMonitor/100: isCaptivePortal: isSuccessful()=false isPortal()=true RedirectUrl=http://10.10.1.2:8080/cn/index.html isPartialConnectivity()=false Time=172ms

从Log中可以看出来，连接WIFI会进行网络的校验，从而判断是否可用，HTTP校验成功，但是HTTPS校验失败，因此会显示网络连接受限，其连接过程中会出现短暂的已连接，无网络是正常现象。HTTPS校验的网址https://www.谷歌.com/generate_204，由于在国内无法访问，所以会校验失败，可采取的做法是替换此网址。

packages/modules/NetworkStack/src/com/android/server/connectivity/NetworkMonitor.java 

#校验源码部分
private CaptivePortalProbeResult sendDnsAndHttpProbes(ProxyInfo proxy, URL url, int probeType) {
        // Pre-resolve the captive portal server host so we can log it.
        // Only do this if HttpURLConnection is about to, to avoid any potentially
        // unnecessary resolution.
        final String host = (proxy != null) ? proxy.getHost() : url.getHost();
        // This method cannot safely report probe results because it might not be running on the
        // state machine thread. Reporting results here would cause races and potentially send
        // information to callers that does not make sense because the state machine has already
        // changed state.
        sendDnsProbe(host);
        return sendHttpProbe(url, probeType, null);
}

# HTTPS网址相关源码
private final URL mCaptivePortalHttpsUrl;
mCaptivePortalHttpsUrl = makeURL(getCaptivePortalServerHttpsUrl());
public String getCaptivePortalServerHttpUrl() {
    return getSettingFromResource(mContext, R.string.config_captive_portal_http_url,
            R.string.default_captive_portal_http_url, CAPTIVE_PORTAL_HTTP_URL);
}

解决方案

packages/modules/NetworkStack/res/values/config.xml 

<!-- HTTP URL for network validation, to use for detecting captive portals. -->
<string name="default_captive_portal_http_url" translatable="false">http://connectivitycheck.gstatic.com/generate_204</string>
<!-- HTTPS URL for network validation, to use for confirming internet connectivity. -->
- <string name="default_captive_portal_https_url" translatable="false">https://www.谷歌.com/generate_204</string>
  <string name="default_captive_portal_https_url" translatable="false">https://developers.谷歌.cn/generate_204</string>

网上还有另一种解法如下，就是关闭校验，此解法可以实现不显示网络连接受限的问题，但是在连接需要登陆的WIFI时，无法连接

frameworks/base/packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java

loadSetting(stmt, Settings.Global.LID_BEHAVIOR, defaultLidBehavior);
loadStringSetting(stmt, Settings.Global.NTP_SERVER_2,
            R.string.def_ntp_server_2);
  loadSetting(stmt, Global.CAPTIVE_PORTAL_MODE, Global.CAPTIVE_PORTAL_MODE_IGNORE);

关于captive_portal_mode的值
0：彻底禁用检测
1：检测到需要登录则弹窗提醒（默认值）
2：检测到需要登录则自动断开此热点并不再自动连接

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