1 /*
2  * Copyright (C) 2008 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.server.location;
18 
19 import android.net.TrafficStats;
20 import android.text.TextUtils;
21 import android.util.Log;
22 
23 import com.android.internal.util.TrafficStatsConstants;
24 
25 import java.io.ByteArrayOutputStream;
26 import java.io.IOException;
27 import java.io.InputStream;
28 import java.net.HttpURLConnection;
29 import java.net.URL;
30 import java.util.Properties;
31 import java.util.Random;
32 import java.util.concurrent.TimeUnit;
33 
34 /**
35  * A class for downloading GPS PSDS data.
36  *
37  * {@hide}
38  */
39 public class GpsPsdsDownloader {
40 
41     private static final String TAG = "GpsPsdsDownloader";
42     private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
43     private static final long MAXIMUM_CONTENT_LENGTH_BYTES = 1000000;  // 1MB.
44     private static final String DEFAULT_USER_AGENT = "Android";
45     private static final int CONNECTION_TIMEOUT_MS = (int) TimeUnit.SECONDS.toMillis(30);
46     private static final int READ_TIMEOUT_MS = (int) TimeUnit.SECONDS.toMillis(60);
47 
48     private final String[] mPsdsServers;
49     // to load balance our server requests
50     private int mNextServerIndex;
51     private final String mUserAgent;
52 
GpsPsdsDownloader(Properties properties)53     GpsPsdsDownloader(Properties properties) {
54         // read PSDS servers from the Properties object
55         int count = 0;
56         String server1 = properties.getProperty("XTRA_SERVER_1");
57         String server2 = properties.getProperty("XTRA_SERVER_2");
58         String server3 = properties.getProperty("XTRA_SERVER_3");
59         if (server1 != null) count++;
60         if (server2 != null) count++;
61         if (server3 != null) count++;
62 
63         // Set User Agent from properties, if possible.
64         String agent = properties.getProperty("XTRA_USER_AGENT");
65         if (TextUtils.isEmpty(agent)) {
66             mUserAgent = DEFAULT_USER_AGENT;
67         } else {
68             mUserAgent = agent;
69         }
70 
71         if (count == 0) {
72             Log.e(TAG, "No PSDS servers were specified in the GPS configuration");
73             mPsdsServers = null;
74         } else {
75             mPsdsServers = new String[count];
76             count = 0;
77             if (server1 != null) mPsdsServers[count++] = server1;
78             if (server2 != null) mPsdsServers[count++] = server2;
79             if (server3 != null) mPsdsServers[count++] = server3;
80 
81             // randomize first server
82             Random random = new Random();
83             mNextServerIndex = random.nextInt(count);
84         }
85     }
86 
downloadPsdsData()87     byte[] downloadPsdsData() {
88         byte[] result = null;
89         int startIndex = mNextServerIndex;
90 
91         if (mPsdsServers == null) {
92             return null;
93         }
94 
95         // load balance our requests among the available servers
96         while (result == null) {
97             final int oldTag = TrafficStats.getAndSetThreadStatsTag(
98                     TrafficStatsConstants.TAG_SYSTEM_GPS);
99             try {
100                 result = doDownload(mPsdsServers[mNextServerIndex]);
101             } finally {
102                 TrafficStats.setThreadStatsTag(oldTag);
103             }
104 
105             // increment mNextServerIndex and wrap around if necessary
106             mNextServerIndex++;
107             if (mNextServerIndex == mPsdsServers.length) {
108                 mNextServerIndex = 0;
109             }
110             // break if we have tried all the servers
111             if (mNextServerIndex == startIndex) break;
112         }
113 
114         return result;
115     }
116 
doDownload(String url)117     protected byte[] doDownload(String url) {
118         if (DEBUG) Log.d(TAG, "Downloading PSDS data from " + url);
119 
120         HttpURLConnection connection = null;
121         try {
122             connection = (HttpURLConnection) (new URL(url)).openConnection();
123             connection.setRequestProperty(
124                     "Accept",
125                     "*/*, application/vnd.wap.mms-message, application/vnd.wap.sic");
126             connection.setRequestProperty(
127                     "x-wap-profile",
128                     "http://www.openmobilealliance.org/tech/profiles/UAPROF/ccppschema-20021212#");
129             connection.setConnectTimeout(CONNECTION_TIMEOUT_MS);
130             connection.setReadTimeout(READ_TIMEOUT_MS);
131 
132             connection.connect();
133             int statusCode = connection.getResponseCode();
134             if (statusCode != HttpURLConnection.HTTP_OK) {
135                 if (DEBUG) Log.d(TAG, "HTTP error downloading gps PSDS: " + statusCode);
136                 return null;
137             }
138 
139             try (InputStream in = connection.getInputStream()) {
140                 ByteArrayOutputStream bytes = new ByteArrayOutputStream();
141                 byte[] buffer = new byte[1024];
142                 int count;
143                 while ((count = in.read(buffer)) != -1) {
144                     bytes.write(buffer, 0, count);
145                     if (bytes.size() > MAXIMUM_CONTENT_LENGTH_BYTES) {
146                         if (DEBUG) Log.d(TAG, "PSDS file too large");
147                         return null;
148                     }
149                 }
150                 return bytes.toByteArray();
151             }
152         } catch (IOException ioe) {
153             if (DEBUG) Log.d(TAG, "Error downloading gps PSDS: ", ioe);
154         } finally {
155             if (connection != null) {
156                 connection.disconnect();
157             }
158         }
159         return null;
160     }
161 
162 }
163 
164