oem_iptables_hook.cpp revision c462177bd58e3bf0ac4f618934dae060569e3e0b 
1/*
2 * Copyright (C) 2012 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 <stdio.h>
18#include <stdlib.h>
19#include <sys/types.h>
20#include <sys/wait.h>
21#include <errno.h>
22#include <string.h>
23#include <unistd.h>
24
25#define LOG_TAG "OemIptablesHook"
26#include <cutils/log.h>
27#include "NetdConstants.h"
28
29extern "C" int system_nosh(const char *command);
30
31
32static int runIptablesCmd(const char *cmd) {
33    char *buffer;
34    size_t len = strnlen(cmd, 255);
35    int res;
36
37    if (len == 255) {
38        ALOGE("command too long");
39        return -1;
40    }
41
42    asprintf(&buffer, "%s %s", IPTABLES_PATH, cmd);
43    res = system_nosh(buffer);
44    free(buffer);
45    return res;
46}
47
48static bool oemSetupHooks() {
49    // Order is important!
50    // -N to create the chain (no-op if already exist).
51    // -D to delete any pre-existing jump rule, to prevent dupes (no-op if doesn't exist)
52    // -I to insert our jump rule into the default chain
53
54    runIptablesCmd("-N oem_out");
55    runIptablesCmd("-D OUTPUT -j oem_out");
56    if (runIptablesCmd("-I OUTPUT -j oem_out"))
57        return false;
58
59    runIptablesCmd("-N oem_fwd");
60    runIptablesCmd("-D FORWARD -j oem_fwd");
61    if (runIptablesCmd("-I FORWARD -j oem_fwd"))
62        return false;
63
64    runIptablesCmd("-t nat -N oem_nat_pre");
65    runIptablesCmd("-t nat -D PREROUTING -j oem_nat_pre");
66    if (runIptablesCmd("-t nat -I PREROUTING -j oem_nat_pre"))
67        return false;
68
69    return true;
70}
71
72static bool oemCleanupHooks() {
73    // Order is important!
74    // -D to remove ref to the chain
75    // -F to empty the chain
76    // -X to delete the chain
77
78    runIptablesCmd("-D OUTPUT -j oem_out");
79    runIptablesCmd("-F oem_out");
80    runIptablesCmd("-X oem_out");
81
82    runIptablesCmd("-D FORWARD -j oem_fwd");
83    runIptablesCmd("-F oem_fwd");
84    runIptablesCmd("-X oem_fwd");
85
86    runIptablesCmd("-t nat -D PREROUTING -j oem_nat_pre");
87    runIptablesCmd("-t nat -F oem_nat_pre");
88    runIptablesCmd("-t nat -X oem_nat_pre");
89
90    return true;
91}
92
93static bool oemInitChains() {
94    int ret = system(OEM_SCRIPT_PATH);
95    if ((-1 == ret) || (0 != WEXITSTATUS(ret))) {
96        ALOGE("%s failed: %s", OEM_SCRIPT_PATH, strerror(errno));
97        oemCleanupHooks();
98        return false;
99    }
100    return true;
101}
102
103
104void setupOemIptablesHook() {
105    if (0 == access(OEM_SCRIPT_PATH, R_OK | X_OK)) {
106        // The call to oemCleanupHooks() is superfluous when done on bootup,
107        // but is needed for the case where netd has crashed/stopped and is
108        // restarted.
109        if (oemCleanupHooks() && oemSetupHooks() && oemInitChains()) {
110            ALOGI("OEM iptable hook installed.");
111        }
112    }
113}
114