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 <sys/socket.h>
20 #include <sys/stat.h>
21 #include <fcntl.h>
22 #include <netinet/in.h>
23 #include <arpa/inet.h>
24 #include <string.h>
25 #include <cutils/properties.h>
26
27 #define LOG_TAG "NatController"
28 #include <cutils/log.h>
29
30 #include "NatController.h"
31
32 extern "C" int logwrap(int argc, const char **argv, int background);
33
34 static char IPTABLES_PATH[] = "/system/bin/iptables";
35
NatController()36 NatController::NatController() {
37 natCount = 0;
38 }
39
~NatController()40 NatController::~NatController() {
41 }
42
runIptablesCmd(const char * cmd)43 int NatController::runIptablesCmd(const char *cmd) {
44 char *buffer;
45 size_t len = strnlen(cmd, 255);
46 int res;
47
48 if (len == 255) {
49 LOGE("iptables command too long");
50 errno = E2BIG;
51 return -1;
52 }
53
54 asprintf(&buffer, "%s %s", IPTABLES_PATH, cmd);
55 res = system(buffer);
56 free(buffer);
57 return res;
58 }
59
setDefaults()60 int NatController::setDefaults() {
61
62 if (runIptablesCmd("-P INPUT ACCEPT"))
63 return -1;
64 if (runIptablesCmd("-P OUTPUT ACCEPT"))
65 return -1;
66 if (runIptablesCmd("-P FORWARD DROP"))
67 return -1;
68 if (runIptablesCmd("-F FORWARD"))
69 return -1;
70 if (runIptablesCmd("-t nat -F"))
71 return -1;
72 return 0;
73 }
74
interfaceExists(const char * iface)75 bool NatController::interfaceExists(const char *iface) {
76 // XXX: Implement this
77 return true;
78 }
79
80 // when un-doing NAT, we should report errors, but also try to do as much cleanup
81 // as we can - don't short circuit on error.
doNatCommands(const char * intIface,const char * extIface,bool add)82 int NatController::doNatCommands(const char *intIface, const char *extIface, bool add) {
83 char cmd[255];
84
85 char bootmode[PROPERTY_VALUE_MAX] = {0};
86 property_get("ro.bootmode", bootmode, "unknown");
87 if (0 != strcmp("bp-tools", bootmode)) {
88 // handle decrement to 0 case (do reset to defaults) and erroneous dec below 0
89 if (add == false) {
90 if (natCount <= 1) {
91 int ret = setDefaults();
92 if (ret == 0) {
93 natCount=0;
94 }
95 LOGE("setDefaults returned %d", ret);
96 return ret;
97 }
98 }
99 }
100
101 if (!interfaceExists(intIface) || !interfaceExists (extIface)) {
102 LOGE("Invalid interface specified");
103 errno = ENODEV;
104 return -1;
105 }
106
107 snprintf(cmd, sizeof(cmd),
108 "-%s FORWARD -i %s -o %s -m state --state ESTABLISHED,RELATED -j ACCEPT",
109 (add ? "A" : "D"),
110 extIface, intIface);
111 if (runIptablesCmd(cmd) && add) {
112 // only bail out if we are adding, not removing nat rules
113 return -1;
114 }
115
116 snprintf(cmd, sizeof(cmd),
117 "-%s FORWARD -i %s -o %s -m state --state INVALID -j DROP",
118 (add ? "A" : "D"),
119 intIface, extIface);
120 if (runIptablesCmd(cmd) && add) {
121 // bail on error, but only if adding
122 snprintf(cmd, sizeof(cmd),
123 "-%s FORWARD -i %s -o %s -m state --state ESTABLISHED,RELATED -j ACCEPT",
124 (!add ? "A" : "D"),
125 extIface, intIface);
126 runIptablesCmd(cmd);
127 return -1;
128 }
129
130 snprintf(cmd, sizeof(cmd), "-%s FORWARD -i %s -o %s -j ACCEPT", (add ? "A" : "D"),
131 intIface, extIface);
132 if (runIptablesCmd(cmd) && add) {
133 // unwind what's been done, but don't care about success - what more could we do?
134 snprintf(cmd, sizeof(cmd),
135 "-%s FORWARD -i %s -o %s -m state --state INVALID -j DROP",
136 (!add ? "A" : "D"),
137 intIface, extIface);
138 runIptablesCmd(cmd);
139
140 snprintf(cmd, sizeof(cmd),
141 "-%s FORWARD -i %s -o %s -m state --state ESTABLISHED,RELATED -j ACCEPT",
142 (!add ? "A" : "D"),
143 extIface, intIface);
144 runIptablesCmd(cmd);
145 return -1;
146 }
147
148 // add this if we are the first added nat
149 if (add && natCount == 0) {
150 snprintf(cmd, sizeof(cmd), "-t nat -A POSTROUTING -o %s -j MASQUERADE", extIface);
151 if (runIptablesCmd(cmd)) {
152 if (0 != strcmp("bp-tools", bootmode)) {
153 // unwind what's been done, but don't care about success - what more could we do?
154 setDefaults();;
155 }
156 return -1;
157 }
158 }
159
160 if (add) {
161 natCount++;
162 } else {
163 natCount--;
164 }
165 return 0;
166 }
167
enableNat(const char * intIface,const char * extIface)168 int NatController::enableNat(const char *intIface, const char *extIface) {
169 return doNatCommands(intIface, extIface, true);
170 }
171
disableNat(const char * intIface,const char * extIface)172 int NatController::disableNat(const char *intIface, const char *extIface) {
173 return doNatCommands(intIface, extIface, false);
174 }
175