281 lines
8.7 KiB
C++
281 lines
8.7 KiB
C++
/*
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* Copyright (C) 2008 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#define LOG_NDEBUG 0
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#include <string>
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#include <vector>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <string.h>
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#include <arpa/inet.h>
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#include <linux/in.h>
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#include <netinet/in.h>
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#include <sys/socket.h>
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#include <sys/stat.h>
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#include <sys/wait.h>
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#define LOG_TAG "NatController"
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#include <android-base/strings.h>
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#include <android-base/stringprintf.h>
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#include <cutils/log.h>
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#include <cutils/properties.h>
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#include <logwrap/logwrap.h>
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#include "NatController.h"
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#include "NetdConstants.h"
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#include "RouteController.h"
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using android::base::Join;
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using android::base::StringPrintf;
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const char* NatController::LOCAL_FORWARD = "natctrl_FORWARD";
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const char* NatController::LOCAL_MANGLE_FORWARD = "natctrl_mangle_FORWARD";
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const char* NatController::LOCAL_NAT_POSTROUTING = "natctrl_nat_POSTROUTING";
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const char* NatController::LOCAL_RAW_PREROUTING = "natctrl_raw_PREROUTING";
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const char* NatController::LOCAL_TETHER_COUNTERS_CHAIN = "natctrl_tether_counters";
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auto NatController::execFunction = android_fork_execvp;
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auto NatController::iptablesRestoreFunction = execIptablesRestore;
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NatController::NatController() {
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}
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NatController::~NatController() {
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}
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struct CommandsAndArgs {
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/* The array size doesn't really matter as the compiler will barf if too many initializers are specified. */
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const char *cmd[32];
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bool checkRes;
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};
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int NatController::setupIptablesHooks() {
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int res;
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res = setDefaults();
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if (res < 0) {
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return res;
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}
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// Used to limit downstream mss to the upstream pmtu so we don't end up fragmenting every large
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// packet tethered devices send. This is IPv4-only, because in IPv6 we send the MTU in the RA.
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// This is no longer optional and tethering will fail to start if it fails.
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std::string mssRewriteCommand = StringPrintf(
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"*mangle\n"
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"-A %s -p tcp --tcp-flags SYN SYN -j TCPMSS --clamp-mss-to-pmtu\n"
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"COMMIT\n", LOCAL_MANGLE_FORWARD);
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// This is for tethering counters. This chain is reached via --goto, and then RETURNS.
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std::string defaultCommands = StringPrintf(
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"*filter\n"
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":%s -\n"
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"COMMIT\n", LOCAL_TETHER_COUNTERS_CHAIN);
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res = iptablesRestoreFunction(V4, mssRewriteCommand);
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if (res < 0) {
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return res;
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}
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res = iptablesRestoreFunction(V4V6, defaultCommands);
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if (res < 0) {
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return res;
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}
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ifacePairList.clear();
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return 0;
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}
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int NatController::setDefaults() {
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std::string v4Cmd = StringPrintf(
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"*filter\n"
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":%s -\n"
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"-A %s -j DROP\n"
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"COMMIT\n"
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"*nat\n"
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":%s -\n"
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"COMMIT\n", LOCAL_FORWARD, LOCAL_FORWARD, LOCAL_NAT_POSTROUTING);
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std::string v6Cmd = StringPrintf(
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"*filter\n"
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":%s -\n"
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"COMMIT\n"
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"*raw\n"
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":%s -\n"
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"COMMIT\n", LOCAL_FORWARD, LOCAL_RAW_PREROUTING);
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int res = iptablesRestoreFunction(V4, v4Cmd);
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if (res < 0) {
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return res;
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}
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res = iptablesRestoreFunction(V6, v6Cmd);
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if (res < 0) {
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return res;
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}
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natCount = 0;
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return 0;
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}
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int NatController::enableNat(const char* intIface, const char* extIface) {
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ALOGV("enableNat(intIface=<%s>, extIface=<%s>)",intIface, extIface);
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if (!isIfaceName(intIface) || !isIfaceName(extIface)) {
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errno = ENODEV;
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return -1;
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}
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/* Bug: b/9565268. "enableNat wlan0 wlan0". For now we fail until java-land is fixed */
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if (!strcmp(intIface, extIface)) {
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ALOGE("Duplicate interface specified: %s %s", intIface, extIface);
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errno = EINVAL;
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return -1;
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}
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// add this if we are the first added nat
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if (natCount == 0) {
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std::vector<std::string> v4Cmds = {
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"*nat",
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StringPrintf("-A %s -o %s -j MASQUERADE", LOCAL_NAT_POSTROUTING, extIface),
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"COMMIT\n"
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};
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/*
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* IPv6 tethering doesn't need the state-based conntrack rules, so
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* it unconditionally jumps to the tether counters chain all the time.
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*/
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std::vector<std::string> v6Cmds = {
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"*filter",
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StringPrintf("-A %s -g %s", LOCAL_FORWARD, LOCAL_TETHER_COUNTERS_CHAIN),
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"COMMIT\n"
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};
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if (iptablesRestoreFunction(V4, Join(v4Cmds, '\n')) ||
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iptablesRestoreFunction(V6, Join(v6Cmds, '\n'))) {
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ALOGE("Error setting postroute rule: iface=%s", extIface);
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// unwind what's been done, but don't care about success - what more could we do?
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setDefaults();
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return -1;
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}
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}
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if (setForwardRules(true, intIface, extIface) != 0) {
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ALOGE("Error setting forward rules");
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if (natCount == 0) {
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setDefaults();
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}
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errno = ENODEV;
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return -1;
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}
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natCount++;
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return 0;
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}
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bool NatController::checkTetherCountingRuleExist(const std::string& pair_name) {
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return std::find(ifacePairList.begin(), ifacePairList.end(), pair_name) != ifacePairList.end();
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}
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/* static */
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std::string NatController::makeTetherCountingRule(const char *if1, const char *if2) {
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return StringPrintf("-A %s -i %s -o %s -j RETURN", LOCAL_TETHER_COUNTERS_CHAIN, if1, if2);
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}
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int NatController::setForwardRules(bool add, const char *intIface, const char *extIface) {
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const char *op = add ? "-A" : "-D";
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std::string rpfilterCmd = StringPrintf(
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"*raw\n"
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"%s %s -i %s -m rpfilter --invert ! -s fe80::/64 -j DROP\n"
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"COMMIT\n", op, LOCAL_RAW_PREROUTING, intIface);
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if (iptablesRestoreFunction(V6, rpfilterCmd) == -1 && add) {
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return -1;
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}
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std::vector<std::string> v4 = {
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"*filter",
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StringPrintf("%s %s -i %s -o %s -m state --state ESTABLISHED,RELATED -g %s",
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op, LOCAL_FORWARD, extIface, intIface, LOCAL_TETHER_COUNTERS_CHAIN),
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StringPrintf("%s %s -i %s -o %s -m state --state INVALID -j DROP",
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op, LOCAL_FORWARD, intIface, extIface),
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StringPrintf("%s %s -i %s -o %s -g %s",
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op, LOCAL_FORWARD, intIface, extIface, LOCAL_TETHER_COUNTERS_CHAIN),
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};
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std::vector<std::string> v6 = {
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"*filter",
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};
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/* We only ever add tethering quota rules so that they stick. */
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std::string pair1 = StringPrintf("%s_%s", intIface, extIface);
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if (add && !checkTetherCountingRuleExist(pair1)) {
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v4.push_back(makeTetherCountingRule(intIface, extIface));
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v6.push_back(makeTetherCountingRule(intIface, extIface));
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}
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std::string pair2 = StringPrintf("%s_%s", extIface, intIface);
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if (add && !checkTetherCountingRuleExist(pair2)) {
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v4.push_back(makeTetherCountingRule(extIface, intIface));
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v6.push_back(makeTetherCountingRule(extIface, intIface));
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}
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// Always make sure the drop rule is at the end.
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// TODO: instead of doing this, consider just rebuilding LOCAL_FORWARD completely from scratch
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// every time, starting with ":natctrl_FORWARD -\n". This method would likely be a bit simpler.
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if (add) {
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v4.push_back(StringPrintf("-D %s -j DROP", LOCAL_FORWARD));
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v4.push_back(StringPrintf("-A %s -j DROP", LOCAL_FORWARD));
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}
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v4.push_back("COMMIT\n");
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v6.push_back("COMMIT\n");
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// We only add IPv6 rules here, never remove them.
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if (iptablesRestoreFunction(V4, Join(v4, '\n')) == -1 ||
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(add && iptablesRestoreFunction(V6, Join(v6, '\n')) == -1)) {
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// unwind what's been done, but don't care about success - what more could we do?
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if (add) {
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setForwardRules(false, intIface, extIface);
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}
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return -1;
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}
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if (add && !checkTetherCountingRuleExist(pair1)) {
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ifacePairList.push_front(pair1);
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}
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if (add && !checkTetherCountingRuleExist(pair2)) {
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ifacePairList.push_front(pair2);
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}
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return 0;
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}
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int NatController::disableNat(const char* intIface, const char* extIface) {
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if (!isIfaceName(intIface) || !isIfaceName(extIface)) {
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errno = ENODEV;
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return -1;
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}
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setForwardRules(false, intIface, extIface);
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if (--natCount <= 0) {
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// handle decrement to 0 case (do reset to defaults) and erroneous dec below 0
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setDefaults();
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}
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return 0;
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}
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