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 #include <stdlib.h>
18 #include <errno.h>
19 #include <fcntl.h>
20 #include <netdb.h>
21 #include <string.h>
22
23 #include <sys/socket.h>
24 #include <sys/stat.h>
25 #include <sys/types.h>
26 #include <sys/wait.h>
27
28 #include <netinet/in.h>
29 #include <arpa/inet.h>
30
31 #define LOG_TAG "TetherController"
32 #include <cutils/log.h>
33 #include <cutils/properties.h>
34
35 #include "Fwmark.h"
36 #include "NetdConstants.h"
37 #include "Permission.h"
38 #include "InterfaceController.h"
39 #include "TetherController.h"
40
41 namespace {
42
43 const char BP_TOOLS_MODE[] = "bp-tools";
44 const char IPV4_FORWARDING_PROC_FILE[] = "/proc/sys/net/ipv4/ip_forward";
45 const char IPV6_FORWARDING_PROC_FILE[] = "/proc/sys/net/ipv6/conf/all/forwarding";
46 const char SEPARATOR[] = "|";
47
writeToFile(const char * filename,const char * value)48 bool writeToFile(const char* filename, const char* value) {
49 int fd = open(filename, O_WRONLY);
50 if (fd < 0) {
51 ALOGE("Failed to open %s: %s", filename, strerror(errno));
52 return false;
53 }
54
55 const ssize_t len = strlen(value);
56 if (write(fd, value, len) != len) {
57 ALOGE("Failed to write %s to %s: %s", value, filename, strerror(errno));
58 close(fd);
59 return false;
60 }
61 close(fd);
62 return true;
63 }
64
configureForIPv6Router(const char * interface)65 bool configureForIPv6Router(const char *interface) {
66 return (InterfaceController::setEnableIPv6(interface, 0) == 0)
67 && (InterfaceController::setAcceptIPv6Ra(interface, 0) == 0)
68 && (InterfaceController::setAcceptIPv6Dad(interface, 0) == 0)
69 && (InterfaceController::setIPv6DadTransmits(interface, "0") == 0)
70 && (InterfaceController::setEnableIPv6(interface, 1) == 0);
71 }
72
configureForIPv6Client(const char * interface)73 void configureForIPv6Client(const char *interface) {
74 InterfaceController::setAcceptIPv6Ra(interface, 1);
75 InterfaceController::setAcceptIPv6Dad(interface, 1);
76 InterfaceController::setIPv6DadTransmits(interface, "1");
77 InterfaceController::setEnableIPv6(interface, 0);
78 }
79
inBpToolsMode()80 bool inBpToolsMode() {
81 // In BP tools mode, do not disable IP forwarding
82 char bootmode[PROPERTY_VALUE_MAX] = {0};
83 property_get("ro.bootmode", bootmode, "unknown");
84 return !strcmp(BP_TOOLS_MODE, bootmode);
85 }
86
87 } // namespace
88
TetherController()89 TetherController::TetherController() {
90 mDnsNetId = 0;
91 mDaemonFd = -1;
92 mDaemonPid = 0;
93 if (inBpToolsMode()) {
94 enableForwarding(BP_TOOLS_MODE);
95 } else {
96 setIpFwdEnabled();
97 }
98 }
99
~TetherController()100 TetherController::~TetherController() {
101 mInterfaces.clear();
102 mDnsForwarders.clear();
103 mForwardingRequests.clear();
104 }
105
setIpFwdEnabled()106 bool TetherController::setIpFwdEnabled() {
107 bool success = true;
108 const char* value = mForwardingRequests.empty() ? "0" : "1";
109 ALOGD("Setting IP forward enable = %s", value);
110 success &= writeToFile(IPV4_FORWARDING_PROC_FILE, value);
111 success &= writeToFile(IPV6_FORWARDING_PROC_FILE, value);
112 return success;
113 }
114
enableForwarding(const char * requester)115 bool TetherController::enableForwarding(const char* requester) {
116 // Don't return an error if this requester already requested forwarding. Only return errors for
117 // things that the caller caller needs to care about, such as "couldn't write to the file to
118 // enable forwarding".
119 mForwardingRequests.insert(requester);
120 return setIpFwdEnabled();
121 }
122
disableForwarding(const char * requester)123 bool TetherController::disableForwarding(const char* requester) {
124 mForwardingRequests.erase(requester);
125 return setIpFwdEnabled();
126 }
127
forwardingRequestCount()128 size_t TetherController::forwardingRequestCount() {
129 return mForwardingRequests.size();
130 }
131
132 #define TETHER_START_CONST_ARG 8
133
startTethering(int num_addrs,char ** dhcp_ranges)134 int TetherController::startTethering(int num_addrs, char **dhcp_ranges) {
135 if (mDaemonPid != 0) {
136 ALOGE("Tethering already started");
137 errno = EBUSY;
138 return -1;
139 }
140
141 ALOGD("Starting tethering services");
142
143 pid_t pid;
144 int pipefd[2];
145
146 if (pipe(pipefd) < 0) {
147 ALOGE("pipe failed (%s)", strerror(errno));
148 return -1;
149 }
150
151 /*
152 * TODO: Create a monitoring thread to handle and restart
153 * the daemon if it exits prematurely
154 */
155 if ((pid = fork()) < 0) {
156 ALOGE("fork failed (%s)", strerror(errno));
157 close(pipefd[0]);
158 close(pipefd[1]);
159 return -1;
160 }
161
162 if (!pid) {
163 close(pipefd[1]);
164 if (pipefd[0] != STDIN_FILENO) {
165 if (dup2(pipefd[0], STDIN_FILENO) != STDIN_FILENO) {
166 ALOGE("dup2 failed (%s)", strerror(errno));
167 return -1;
168 }
169 close(pipefd[0]);
170 }
171
172 int num_processed_args = TETHER_START_CONST_ARG + (num_addrs/2) + 1;
173 char **args = (char **)malloc(sizeof(char *) * num_processed_args);
174 args[num_processed_args - 1] = NULL;
175 args[0] = (char *)"/system/bin/dnsmasq";
176 args[1] = (char *)"--keep-in-foreground";
177 args[2] = (char *)"--no-resolv";
178 args[3] = (char *)"--no-poll";
179 args[4] = (char *)"--dhcp-authoritative";
180 // TODO: pipe through metered status from ConnService
181 args[5] = (char *)"--dhcp-option-force=43,ANDROID_METERED";
182 args[6] = (char *)"--pid-file";
183 args[7] = (char *)"";
184
185 int nextArg = TETHER_START_CONST_ARG;
186 for (int addrIndex = 0; addrIndex < num_addrs; addrIndex += 2) {
187 asprintf(&(args[nextArg++]),"--dhcp-range=%s,%s,1h",
188 dhcp_ranges[addrIndex], dhcp_ranges[addrIndex+1]);
189 }
190
191 if (execv(args[0], args)) {
192 ALOGE("execl failed (%s)", strerror(errno));
193 }
194 ALOGE("Should never get here!");
195 _exit(-1);
196 } else {
197 close(pipefd[0]);
198 mDaemonPid = pid;
199 mDaemonFd = pipefd[1];
200 applyDnsInterfaces();
201 ALOGD("Tethering services running");
202 }
203
204 return 0;
205 }
206
stopTethering()207 int TetherController::stopTethering() {
208
209 if (mDaemonPid == 0) {
210 ALOGE("Tethering already stopped");
211 return 0;
212 }
213
214 ALOGD("Stopping tethering services");
215
216 kill(mDaemonPid, SIGTERM);
217 waitpid(mDaemonPid, NULL, 0);
218 mDaemonPid = 0;
219 close(mDaemonFd);
220 mDaemonFd = -1;
221 ALOGD("Tethering services stopped");
222 return 0;
223 }
224
isTetheringStarted()225 bool TetherController::isTetheringStarted() {
226 return (mDaemonPid == 0 ? false : true);
227 }
228
229 #define MAX_CMD_SIZE 1024
230
setDnsForwarders(unsigned netId,char ** servers,int numServers)231 int TetherController::setDnsForwarders(unsigned netId, char **servers, int numServers) {
232 int i;
233 char daemonCmd[MAX_CMD_SIZE];
234
235 Fwmark fwmark;
236 fwmark.netId = netId;
237 fwmark.explicitlySelected = true;
238 fwmark.protectedFromVpn = true;
239 fwmark.permission = PERMISSION_SYSTEM;
240
241 snprintf(daemonCmd, sizeof(daemonCmd), "update_dns%s0x%x", SEPARATOR, fwmark.intValue);
242 int cmdLen = strlen(daemonCmd);
243
244 mDnsForwarders.clear();
245 for (i = 0; i < numServers; i++) {
246 ALOGD("setDnsForwarders(0x%x %d = '%s')", fwmark.intValue, i, servers[i]);
247
248 addrinfo *res, hints = { .ai_flags = AI_NUMERICHOST };
249 int ret = getaddrinfo(servers[i], NULL, &hints, &res);
250 freeaddrinfo(res);
251 if (ret) {
252 ALOGE("Failed to parse DNS server '%s'", servers[i]);
253 mDnsForwarders.clear();
254 errno = EINVAL;
255 return -1;
256 }
257
258 cmdLen += (strlen(servers[i]) + 1);
259 if (cmdLen + 1 >= MAX_CMD_SIZE) {
260 ALOGD("Too many DNS servers listed");
261 break;
262 }
263
264 strcat(daemonCmd, SEPARATOR);
265 strcat(daemonCmd, servers[i]);
266 mDnsForwarders.push_back(servers[i]);
267 }
268
269 mDnsNetId = netId;
270 if (mDaemonFd != -1) {
271 ALOGD("Sending update msg to dnsmasq [%s]", daemonCmd);
272 if (write(mDaemonFd, daemonCmd, strlen(daemonCmd) +1) < 0) {
273 ALOGE("Failed to send update command to dnsmasq (%s)", strerror(errno));
274 mDnsForwarders.clear();
275 errno = EREMOTEIO;
276 return -1;
277 }
278 }
279 return 0;
280 }
281
getDnsNetId()282 unsigned TetherController::getDnsNetId() {
283 return mDnsNetId;
284 }
285
getDnsForwarders() const286 const std::list<std::string> &TetherController::getDnsForwarders() const {
287 return mDnsForwarders;
288 }
289
applyDnsInterfaces()290 bool TetherController::applyDnsInterfaces() {
291 char daemonCmd[MAX_CMD_SIZE];
292
293 strcpy(daemonCmd, "update_ifaces");
294 int cmdLen = strlen(daemonCmd);
295 bool haveInterfaces = false;
296
297 for (const auto &ifname : mInterfaces) {
298 cmdLen += (ifname.size() + 1);
299 if (cmdLen + 1 >= MAX_CMD_SIZE) {
300 ALOGD("Too many DNS ifaces listed");
301 break;
302 }
303
304 strcat(daemonCmd, SEPARATOR);
305 strcat(daemonCmd, ifname.c_str());
306 haveInterfaces = true;
307 }
308
309 if ((mDaemonFd != -1) && haveInterfaces) {
310 ALOGD("Sending update msg to dnsmasq [%s]", daemonCmd);
311 if (write(mDaemonFd, daemonCmd, strlen(daemonCmd) +1) < 0) {
312 ALOGE("Failed to send update command to dnsmasq (%s)", strerror(errno));
313 return false;
314 }
315 }
316 return true;
317 }
318
tetherInterface(const char * interface)319 int TetherController::tetherInterface(const char *interface) {
320 ALOGD("tetherInterface(%s)", interface);
321 if (!isIfaceName(interface)) {
322 errno = ENOENT;
323 return -1;
324 }
325
326 if (!configureForIPv6Router(interface)) {
327 configureForIPv6Client(interface);
328 return -1;
329 }
330 mInterfaces.push_back(interface);
331
332 if (!applyDnsInterfaces()) {
333 mInterfaces.pop_back();
334 configureForIPv6Client(interface);
335 return -1;
336 } else {
337 return 0;
338 }
339 }
340
untetherInterface(const char * interface)341 int TetherController::untetherInterface(const char *interface) {
342 ALOGD("untetherInterface(%s)", interface);
343
344 for (auto it = mInterfaces.cbegin(); it != mInterfaces.cend(); ++it) {
345 if (!strcmp(interface, it->c_str())) {
346 mInterfaces.erase(it);
347
348 configureForIPv6Client(interface);
349 return applyDnsInterfaces() ? 0 : -1;
350 }
351 }
352 errno = ENOENT;
353 return -1;
354 }
355
getTetheredInterfaceList() const356 const std::list<std::string> &TetherController::getTetheredInterfaceList() const {
357 return mInterfaces;
358 }
359