/*
* Copyright (C) 2008 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#define LOG_NDEBUG 0
#include <stdlib.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <cutils/properties.h>
#define LOG_TAG "NatController"
#include <cutils/log.h>
#include <logwrap/logwrap.h>
#include "NatController.h"
#include "NetdConstants.h"
#include "RouteController.h"
const char* NatController::LOCAL_FORWARD = "natctrl_FORWARD";
const char* NatController::LOCAL_MANGLE_FORWARD = "natctrl_mangle_FORWARD";
const char* NatController::LOCAL_NAT_POSTROUTING = "natctrl_nat_POSTROUTING";
const char* NatController::LOCAL_TETHER_COUNTERS_CHAIN = "natctrl_tether_counters";
NatController::NatController() {
}
NatController::~NatController() {
}
struct CommandsAndArgs {
/* The array size doesn't really matter as the compiler will barf if too many initializers are specified. */
const char *cmd[32];
bool checkRes;
};
int NatController::runCmd(int argc, const char **argv) {
int res;
res = android_fork_execvp(argc, (char **)argv, NULL, false, false);
#if !LOG_NDEBUG
std::string full_cmd = argv[0];
argc--; argv++;
/*
* HACK: Sometimes runCmd() is called with a ridcously large value (32)
* and it works because the argv[] contains a NULL after the last
* true argv. So here we use the NULL argv[] to terminate when the argc
* is horribly wrong, and argc for the normal cases.
*/
for (; argc && argv[0]; argc--, argv++) {
full_cmd += " ";
full_cmd += argv[0];
}
ALOGV("runCmd(%s) res=%d", full_cmd.c_str(), res);
#endif
return res;
}
int NatController::setupIptablesHooks() {
int res;
res = setDefaults();
if (res < 0) {
return res;
}
struct CommandsAndArgs defaultCommands[] = {
/*
* First chain is for tethering counters.
* This chain is reached via --goto, and then RETURNS.
*
* Second chain is used to limit downstream mss to the upstream pmtu
* so we don't end up fragmenting every large packet tethered devices
* send. Note this feature requires kernel support with flag
* CONFIG_NETFILTER_XT_TARGET_TCPMSS=y, which not all builds will have,
* so the final rule is allowed to fail.
* Bug 17629786 asks to make the failure more obvious, or even fatal
* so that all builds eventually gain the performance improvement.
*/
{{IPTABLES_PATH, "-F", LOCAL_TETHER_COUNTERS_CHAIN,}, 0},
{{IPTABLES_PATH, "-X", LOCAL_TETHER_COUNTERS_CHAIN,}, 0},
{{IPTABLES_PATH, "-N", LOCAL_TETHER_COUNTERS_CHAIN,}, 1},
{{IPTABLES_PATH, "-t", "mangle", "-A", LOCAL_MANGLE_FORWARD, "-p", "tcp", "--tcp-flags",
"SYN", "SYN", "-j", "TCPMSS", "--clamp-mss-to-pmtu"}, 0},
};
for (unsigned int cmdNum = 0; cmdNum < ARRAY_SIZE(defaultCommands); cmdNum++) {
if (runCmd(ARRAY_SIZE(defaultCommands[cmdNum].cmd), defaultCommands[cmdNum].cmd) &&
defaultCommands[cmdNum].checkRes) {
return -1;
}
}
ifacePairList.clear();
return 0;
}
int NatController::setDefaults() {
/*
* The following only works because:
* - the defaultsCommands[].cmd array is padded with NULL, and
* - the 1st argc of runCmd() will just be the max for the CommandsAndArgs[].cmd, and
* - internally it will be memcopied to an array and terminated with a NULL.
*/
struct CommandsAndArgs defaultCommands[] = {
{{IPTABLES_PATH, "-F", LOCAL_FORWARD,}, 1},
{{IPTABLES_PATH, "-A", LOCAL_FORWARD, "-j", "DROP"}, 1},
{{IPTABLES_PATH, "-t", "nat", "-F", LOCAL_NAT_POSTROUTING}, 1},
};
for (unsigned int cmdNum = 0; cmdNum < ARRAY_SIZE(defaultCommands); cmdNum++) {
if (runCmd(ARRAY_SIZE(defaultCommands[cmdNum].cmd), defaultCommands[cmdNum].cmd) &&
defaultCommands[cmdNum].checkRes) {
return -1;
}
}
natCount = 0;
return 0;
}
int NatController::enableNat(const char* intIface, const char* extIface) {
ALOGV("enableNat(intIface=<%s>, extIface=<%s>)",intIface, extIface);
if (!isIfaceName(intIface) || !isIfaceName(extIface)) {
errno = ENODEV;
return -1;
}
/* Bug: b/9565268. "enableNat wlan0 wlan0". For now we fail until java-land is fixed */
if (!strcmp(intIface, extIface)) {
ALOGE("Duplicate interface specified: %s %s", intIface, extIface);
errno = EINVAL;
return -1;
}
// add this if we are the first added nat
if (natCount == 0) {
const char *cmd[] = {
IPTABLES_PATH,
"-t",
"nat",
"-A",
LOCAL_NAT_POSTROUTING,
"-o",
extIface,
"-j",
"MASQUERADE"
};
if (runCmd(ARRAY_SIZE(cmd), cmd)) {
ALOGE("Error setting postroute rule: iface=%s", extIface);
// unwind what's been done, but don't care about success - what more could we do?
setDefaults();
return -1;
}
}
if (setForwardRules(true, intIface, extIface) != 0) {
ALOGE("Error setting forward rules");
if (natCount == 0) {
setDefaults();
}
errno = ENODEV;
return -1;
}
/* Always make sure the drop rule is at the end */
const char *cmd1[] = {
IPTABLES_PATH,
"-D",
LOCAL_FORWARD,
"-j",
"DROP"
};
runCmd(ARRAY_SIZE(cmd1), cmd1);
const char *cmd2[] = {
IPTABLES_PATH,
"-A",
LOCAL_FORWARD,
"-j",
"DROP"
};
runCmd(ARRAY_SIZE(cmd2), cmd2);
if (int ret = RouteController::enableTethering(intIface, extIface)) {
ALOGE("failed to add tethering rule for iif=%s oif=%s", intIface, extIface);
if (natCount == 0) {
setDefaults();
}
errno = -ret;
return -1;
}
natCount++;
return 0;
}
bool NatController::checkTetherCountingRuleExist(const char *pair_name) {
std::list<std::string>::iterator it;
for (it = ifacePairList.begin(); it != ifacePairList.end(); it++) {
if (*it == pair_name) {
/* We already have this counter */
return true;
}
}
return false;
}
int NatController::setTetherCountingRules(bool add, const char *intIface, const char *extIface) {
/* We only ever add tethering quota rules so that they stick. */
if (!add) {
return 0;
}
char *pair_name;
asprintf(&pair_name, "%s_%s", intIface, extIface);
if (checkTetherCountingRuleExist(pair_name)) {
free(pair_name);
return 0;
}
const char *cmd2b[] = {
IPTABLES_PATH,
"-A",
LOCAL_TETHER_COUNTERS_CHAIN,
"-i",
intIface,
"-o",
extIface,
"-j",
"RETURN"
};
if (runCmd(ARRAY_SIZE(cmd2b), cmd2b) && add) {
free(pair_name);
return -1;
}
ifacePairList.push_front(pair_name);
free(pair_name);
asprintf(&pair_name, "%s_%s", extIface, intIface);
if (checkTetherCountingRuleExist(pair_name)) {
free(pair_name);
return 0;
}
const char *cmd3b[] = {
IPTABLES_PATH,
"-A",
LOCAL_TETHER_COUNTERS_CHAIN,
"-i",
extIface,
"-o",
intIface,
"-j",
"RETURN"
};
if (runCmd(ARRAY_SIZE(cmd3b), cmd3b) && add) {
// unwind what's been done, but don't care about success - what more could we do?
free(pair_name);
return -1;
}
ifacePairList.push_front(pair_name);
free(pair_name);
return 0;
}
int NatController::setForwardRules(bool add, const char *intIface, const char *extIface) {
const char *cmd1[] = {
IPTABLES_PATH,
add ? "-A" : "-D",
LOCAL_FORWARD,
"-i",
extIface,
"-o",
intIface,
"-m",
"state",
"--state",
"ESTABLISHED,RELATED",
"-g",
LOCAL_TETHER_COUNTERS_CHAIN
};
int rc = 0;
if (runCmd(ARRAY_SIZE(cmd1), cmd1) && add) {
return -1;
}
const char *cmd2[] = {
IPTABLES_PATH,
add ? "-A" : "-D",
LOCAL_FORWARD,
"-i",
intIface,
"-o",
extIface,
"-m",
"state",
"--state",
"INVALID",
"-j",
"DROP"
};
const char *cmd3[] = {
IPTABLES_PATH,
add ? "-A" : "-D",
LOCAL_FORWARD,
"-i",
intIface,
"-o",
extIface,
"-g",
LOCAL_TETHER_COUNTERS_CHAIN
};
if (runCmd(ARRAY_SIZE(cmd2), cmd2) && add) {
// bail on error, but only if adding
rc = -1;
goto err_invalid_drop;
}
if (runCmd(ARRAY_SIZE(cmd3), cmd3) && add) {
// unwind what's been done, but don't care about success - what more could we do?
rc = -1;
goto err_return;
}
if (setTetherCountingRules(add, intIface, extIface) && add) {
rc = -1;
goto err_return;
}
return 0;
err_return:
cmd2[1] = "-D";
runCmd(ARRAY_SIZE(cmd2), cmd2);
err_invalid_drop:
cmd1[1] = "-D";
runCmd(ARRAY_SIZE(cmd1), cmd1);
return rc;
}
int NatController::disableNat(const char* intIface, const char* extIface) {
if (!isIfaceName(intIface) || !isIfaceName(extIface)) {
errno = ENODEV;
return -1;
}
if (int ret = RouteController::disableTethering(intIface, extIface)) {
ALOGE("failed to remove tethering rule for iif=%s oif=%s", intIface, extIface);
errno = -ret;
return -1;
}
setForwardRules(false, intIface, extIface);
if (--natCount <= 0) {
// handle decrement to 0 case (do reset to defaults) and erroneous dec below 0
setDefaults();
}
return 0;
}