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
25 #define LOG_TAG "NatController"
26 #include <cutils/log.h>
27
28 #include "NatController.h"
29
30 extern "C" int logwrap(int argc, const char **argv, int background);
31
32 static char IPTABLES_PATH[] = "/system/bin/iptables";
33
NatController()34 NatController::NatController() {
35 natCount = 0;
36 }
37
~NatController()38 NatController::~NatController() {
39 }
40
runIptablesCmd(const char * cmd)41 int NatController::runIptablesCmd(const char *cmd) {
42 char buffer[255];
43
44 strncpy(buffer, cmd, sizeof(buffer)-1);
45
46 const char *args[16];
47 char *next = buffer;
48 char *tmp;
49
50 args[0] = IPTABLES_PATH;
51 args[1] = "--verbose";
52 int i = 2;
53
54 while ((tmp = strsep(&next, " "))) {
55 args[i++] = tmp;
56 if (i == 16) {
57 LOGE("iptables argument overflow");
58 errno = E2BIG;
59 return -1;
60 }
61 }
62 args[i] = NULL;
63
64 return logwrap(i, args, 0);
65 }
66
setDefaults()67 int NatController::setDefaults() {
68
69 if (runIptablesCmd("-P INPUT ACCEPT"))
70 return -1;
71 if (runIptablesCmd("-F INPUT"))
72 return -1;
73 if (runIptablesCmd("-P OUTPUT ACCEPT"))
74 return -1;
75 if (runIptablesCmd("-F OUTPUT"))
76 return -1;
77 if (runIptablesCmd("-P FORWARD DROP"))
78 return -1;
79 if (runIptablesCmd("-F FORWARD"))
80 return -1;
81 if (runIptablesCmd("-t nat -F"))
82 return -1;
83 return 0;
84 }
85
interfaceExists(const char * iface)86 bool NatController::interfaceExists(const char *iface) {
87 // XXX: STOPSHIP - Implement this
88 return true;
89 }
90
doNatCommands(const char * intIface,const char * extIface,bool add)91 int NatController::doNatCommands(const char *intIface, const char *extIface, bool add) {
92 char cmd[255];
93
94 // handle decrement to 0 case (do reset to defaults) and erroneous dec below 0
95 if (add == false) {
96 if (natCount <= 1) {
97 int ret = setDefaults();
98 if (ret == 0) {
99 natCount=0;
100 }
101 return ret;
102 }
103 }
104
105 if (!interfaceExists(intIface) || !interfaceExists (extIface)) {
106 LOGE("Invalid interface specified");
107 errno = ENODEV;
108 return -1;
109 }
110
111 snprintf(cmd, sizeof(cmd),
112 "-%s FORWARD -i %s -o %s -m state --state ESTABLISHED,RELATED -j ACCEPT",
113 (add ? "A" : "D"),
114 extIface, intIface);
115 if (runIptablesCmd(cmd)) {
116 return -1;
117 }
118
119 snprintf(cmd, sizeof(cmd), "-%s FORWARD -i %s -o %s -j ACCEPT", (add ? "A" : "D"),
120 intIface, extIface);
121 if (runIptablesCmd(cmd)) {
122 // unwind what's been done, but don't care about success - what more could we do?
123 snprintf(cmd, sizeof(cmd),
124 "-%s FORWARD -i %s -o %s -m state --state ESTABLISHED,RELATED -j ACCEPT",
125 (!add ? "A" : "D"),
126 extIface, intIface);
127 return -1;
128 }
129
130 // add this if we are the first added nat
131 if (add && natCount == 0) {
132 snprintf(cmd, sizeof(cmd), "-t nat -A POSTROUTING -o %s -j MASQUERADE", extIface);
133 if (runIptablesCmd(cmd)) {
134 // unwind what's been done, but don't care about success - what more could we do?
135 setDefaults();;
136 return -1;
137 }
138 }
139
140 if (add) {
141 natCount++;
142 } else {
143 natCount--;
144 }
145 return 0;
146 }
147
enableNat(const char * intIface,const char * extIface)148 int NatController::enableNat(const char *intIface, const char *extIface) {
149 return doNatCommands(intIface, extIface, true);
150 }
151
disableNat(const char * intIface,const char * extIface)152 int NatController::disableNat(const char *intIface, const char *extIface) {
153 return doNatCommands(intIface, extIface, false);
154 }
155