1 //
2 // Copyright (C) 2014 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 "apmanager/dhcp_server.h"
18
19 #include <net/if.h>
20 #include <signal.h>
21
22 #include <base/strings/stringprintf.h>
23
24 #include "apmanager/daemon.h"
25
26 using std::string;
27
28 namespace apmanager {
29
30 // static.
31 #if !defined(__ANDROID__)
32 const char DHCPServer::kDnsmasqPath[] = "/usr/sbin/dnsmasq";
33 const char DHCPServer::kDnsmasqConfigFilePathFormat[] =
34 "/var/run/apmanager/dnsmasq/dhcpd-%d.conf";
35 const char DHCPServer::kDHCPLeasesFilePathFormat[] =
36 "/var/run/apmanager/dnsmasq/dhcpd-%d.leases";
37 #else
38 const char DHCPServer::kDnsmasqPath[] = "/system/bin/dnsmasq";
39 const char DHCPServer::kDnsmasqConfigFilePathFormat[] =
40 "/data/misc/apmanager/dnsmasq/dhcpd-%d.conf";
41 const char DHCPServer::kDHCPLeasesFilePathFormat[] =
42 "/data/misc/apmanager/dnsmasq/dhcpd-%d.leases";
43 const char DHCPServer::kDnsmasqPidFilePath[] =
44 "/data/misc/apmanager/dnsmasq/dnsmasq.pid";
45 #endif // __ANDROID__
46
47 const char DHCPServer::kServerAddressFormat[] = "192.168.%d.254";
48 const char DHCPServer::kAddressRangeLowFormat[] = "192.168.%d.1";
49 const char DHCPServer::kAddressRangeHighFormat[] = "192.168.%d.128";
50 const int DHCPServer::kServerAddressPrefix = 24;
51 const int DHCPServer::kTerminationTimeoutSeconds = 2;
52
DHCPServer(uint16_t server_address_index,const string & interface_name)53 DHCPServer::DHCPServer(uint16_t server_address_index,
54 const string& interface_name)
55 : server_address_index_(server_address_index),
56 interface_name_(interface_name),
57 server_address_(shill::IPAddress::kFamilyIPv4),
58 rtnl_handler_(shill::RTNLHandler::GetInstance()),
59 file_writer_(FileWriter::GetInstance()),
60 process_factory_(ProcessFactory::GetInstance()) {}
61
~DHCPServer()62 DHCPServer::~DHCPServer() {
63 if (dnsmasq_process_) {
64 // The destructor of the Process will send a SIGKILL signal if it is not
65 // already terminated.
66 dnsmasq_process_->Kill(SIGTERM, kTerminationTimeoutSeconds);
67 dnsmasq_process_.reset();
68 rtnl_handler_->RemoveInterfaceAddress(
69 rtnl_handler_->GetInterfaceIndex(interface_name_), server_address_);
70 }
71 }
72
Start()73 bool DHCPServer::Start() {
74 if (dnsmasq_process_) {
75 LOG(ERROR) << "DHCP Server already running";
76 return false;
77 }
78
79 // Generate dnsmasq config file.
80 string config_str = GenerateConfigFile();
81 string file_name = base::StringPrintf(kDnsmasqConfigFilePathFormat,
82 server_address_index_);
83 if (!file_writer_->Write(file_name, config_str)) {
84 LOG(ERROR) << "Failed to write configuration to a file";
85 return false;
86 }
87
88 // Setup local server address and bring up the interface in case it is down.
89 server_address_.SetAddressFromString(
90 base::StringPrintf(kServerAddressFormat, server_address_index_));
91 server_address_.set_prefix(kServerAddressPrefix);
92 int interface_index = rtnl_handler_->GetInterfaceIndex(interface_name_);
93 rtnl_handler_->AddInterfaceAddress(
94 interface_index,
95 server_address_,
96 server_address_.GetDefaultBroadcast(),
97 shill::IPAddress(shill::IPAddress::kFamilyIPv4));
98 rtnl_handler_->SetInterfaceFlags(interface_index, IFF_UP, IFF_UP);
99
100 // Start a dnsmasq process.
101 dnsmasq_process_.reset(process_factory_->CreateProcess());
102 dnsmasq_process_->AddArg(kDnsmasqPath);
103 dnsmasq_process_->AddArg(base::StringPrintf("--conf-file=%s",
104 file_name.c_str()));
105 #if defined(__ANDROID__)
106 // dnsmasq normally creates a pid file in /var/run/dnsmasq.pid. Overwrite
107 // this file path for Android.
108 dnsmasq_process_->AddArg(
109 base::StringPrintf("--pid-file=%s", kDnsmasqPidFilePath));
110 #endif // __ANDROID__
111 if (!dnsmasq_process_->Start()) {
112 rtnl_handler_->RemoveInterfaceAddress(interface_index, server_address_);
113 dnsmasq_process_.reset();
114 LOG(ERROR) << "Failed to start dnsmasq process";
115 return false;
116 }
117
118 return true;
119 }
120
GenerateConfigFile()121 string DHCPServer::GenerateConfigFile() {
122 string server_address = base::StringPrintf(kServerAddressFormat,
123 server_address_index_);
124 string address_low = base::StringPrintf(kAddressRangeLowFormat,
125 server_address_index_);
126 string address_high = base::StringPrintf(kAddressRangeHighFormat,
127 server_address_index_);
128 string lease_file_path = base::StringPrintf(kDHCPLeasesFilePathFormat,
129 server_address_index_);
130 string config;
131 config += "port=0\n";
132 config += "bind-interfaces\n";
133 config += "log-dhcp\n";
134 // By default, dnsmasq process will spawn off another process to run the
135 // dnsmasq task in the "background" and exit the current process immediately.
136 // This means the daemon would not have any knowledge of the background
137 // dnsmasq process, and it will continue to run even after the AP service is
138 // terminated. Configure dnsmasq to run in "foreground" so no extra process
139 // will be spawned.
140 config += "keep-in-foreground\n";
141 base::StringAppendF(
142 &config, "dhcp-range=%s,%s\n", address_low.c_str(), address_high.c_str());
143 base::StringAppendF(&config, "interface=%s\n", interface_name_.c_str());
144 // Explicitly set the user to apmanager. If not set, dnsmasq will default to
145 // run as "nobody".
146 base::StringAppendF(&config, "user=%s\n", Daemon::kAPManagerUserName);
147 base::StringAppendF(&config, "dhcp-leasefile=%s\n", lease_file_path.c_str());
148 return config;
149 }
150
151 } // namespace apmanager
152