Merge "Facilitate network validation on networks with a per-network PAC." into lmp-mr1-dev

import android.net.NetworkCapabilities;

import android.net.NetworkInfo;

import android.net.NetworkRequest;

import android.net.ProxyInfo;

import android.net.TrafficStats;

import android.net.Uri;

import android.net.wifi.WifiInfo;

        int httpResponseCode = 599;

        try {

            URL url = new URL("http", mServer, "/generate_204");

            // On networks with a PAC instead of fetching a URL that should result in a 204

            // reponse, we instead simply fetch the PAC script.  This is done for a few reasons:

            // 1. At present our PAC code does not yet handle multiple PACs on multiple networks

            //    until something like https://android-review.googlesource.com/#/c/115180/ lands.

            //    Network.openConnection() will ignore network-specific PACs and instead fetch

            //    using NO_PROXY.  If a PAC is in place, the only fetch we know will succeed with

            //    NO_PROXY is the fetch of the PAC itself.

            // 2. To proxy the generate_204 fetch through a PAC would require a number of things

            //    happen before the fetch can commence, namely:

            //        a) the PAC script be fetched

            //        b) a PAC script resolver service be fired up and resolve mServer

            //    Network validation could be delayed until these prerequisities are satisifed or

            //    could simply be left to race them.  Neither is an optimal solution.

            // 3. PAC scripts are sometimes used to block or restrict Internet access and may in

            //    fact block fetching of the generate_204 URL which would lead to false negative

            //    results for network validation.

            boolean fetchPac = false;

            {

                final ProxyInfo proxyInfo = mNetworkAgentInfo.linkProperties.getHttpProxy();

                if (proxyInfo != null && !Uri.EMPTY.equals(proxyInfo.getPacFileUrl())) {

                    url = new URL(proxyInfo.getPacFileUrl().toString());

                    fetchPac = true;

                }

            }

            if (DBG) {

                log("Checking " + url.toString() + " on " +

                        mNetworkAgentInfo.networkInfo.getExtraInfo());

            }

            urlConnection = (HttpURLConnection) mNetworkAgentInfo.network.openConnection(url);

            urlConnection.setInstanceFollowRedirects(false);

            urlConnection.setInstanceFollowRedirects(fetchPac);

            urlConnection.setConnectTimeout(SOCKET_TIMEOUT_MS);

            urlConnection.setReadTimeout(SOCKET_TIMEOUT_MS);

            urlConnection.setUseCaches(false);

                httpResponseCode = 204;

            }

            if (httpResponseCode == 200 && fetchPac) {

                if (DBG) log("PAC fetch 200 response interpreted as 204 response.");

                httpResponseCode = 204;

            }

            sendNetworkConditionsBroadcast(true /* response received */,

                    httpResponseCode != 204 /* isCaptivePortal */,

                    requestTimestamp, responseTimestamp);