/*
* 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.
*/
#include <map>
#include <string>
#include <arpa/inet.h>
#include <errno.h>
#include <linux/if_arp.h>
#include <linux/if_tun.h>
#include <linux/ioctl.h>
#include <net/if.h>
#include <netinet/in.h>
#include <spawn.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#define LOG_TAG "ClatdController"
#include <log/log.h>
#include "ClatdController.h"
#include "android-base/properties.h"
#include "android-base/scopeguard.h"
#include "android-base/stringprintf.h"
#include "android-base/unique_fd.h"
#include "bpf/BpfMap.h"
#include "netdbpf/bpf_shared.h"
#include "netdutils/DumpWriter.h"
extern "C" {
#include "netutils/checksum.h"
}
#include "ClatUtils.h"
#include "Fwmark.h"
#include "NetdConstants.h"
#include "NetworkController.h"
#include "netid_client.h"
static const char* kClatdPath = "/system/bin/clatd";
// For historical reasons, start with 192.0.0.4, and after that, use all subsequent addresses in
// 192.0.0.0/29 (RFC 7335).
static const char* kV4AddrString = "192.0.0.4";
static const in_addr kV4Addr = {inet_addr(kV4AddrString)};
static const int kV4AddrLen = 29;
using android::base::StringPrintf;
using android::base::unique_fd;
using android::bpf::BpfMap;
using android::netdutils::DumpWriter;
using android::netdutils::ScopedIndent;
namespace android {
namespace net {
void ClatdController::init(void) {
std::lock_guard guard(mutex);
// TODO: should refactor into separate function for testability
if (bpf::getBpfSupportLevel() == bpf::BpfLevel::NONE) {
ALOGI("Pre-4.9 kernel or pre-P api shipping level - disabling clat ebpf.");
mClatEbpfMode = ClatEbpfDisabled;
return;
}
// We know the device initially shipped with at least P...,
// but did it ship with at least Q?
uint64_t api_level = base::GetUintProperty<uint64_t>("ro.product.first_api_level", 0);
if (api_level == 0) {
ALOGE("Cannot determine initial API level of the device.");
api_level = base::GetUintProperty<uint64_t>("ro.build.version.sdk", 0);
}
// Note: MINIMUM_API_REQUIRED is for eBPF as a whole and is thus P
if (api_level > bpf::MINIMUM_API_REQUIRED) {
ALOGI("4.9+ kernel and device shipped with Q+ - clat ebpf should work.");
mClatEbpfMode = ClatEbpfEnabled;
} else {
// We cannot guarantee that 4.9-P kernels will include NET_CLS_BPF support.
ALOGI("4.9+ kernel and device shipped with P - clat ebpf might work.");
mClatEbpfMode = ClatEbpfMaybe;
}
int rv = openNetlinkSocket();
if (rv < 0) {
ALOGE("openNetlinkSocket() failure: %s", strerror(-rv));
mClatEbpfMode = ClatEbpfDisabled;
return;
}
mNetlinkFd.reset(rv);
rv = getClatIngressMapFd();
if (rv < 0) {
ALOGE("getClatIngressMapFd() failure: %s", strerror(-rv));
mClatEbpfMode = ClatEbpfDisabled;
mNetlinkFd.reset(-1);
return;
}
mClatIngressMap.reset(rv);
int netlinkFd = mNetlinkFd.get();
// TODO: perhaps this initial cleanup should be in its own function?
const auto del = [&netlinkFd](const ClatIngressKey& key,
const BpfMap<ClatIngressKey, ClatIngressValue>&) {
ALOGW("Removing stale clat config on interface %d.", key.iif);
int rv = tcQdiscDelDevClsact(netlinkFd, key.iif);
if (rv < 0) ALOGE("tcQdiscDelDevClsact() failure: %s", strerror(-rv));
return netdutils::status::ok; // keep on going regardless
};
auto ret = mClatIngressMap.iterate(del);
if (!isOk(ret)) ALOGE("mClatIngressMap.iterate() failure: %s", strerror(ret.code()));
ret = mClatIngressMap.clear();
if (!isOk(ret)) ALOGE("mClatIngressMap.clear() failure: %s", strerror(ret.code()));
}
bool ClatdController::isIpv4AddressFree(in_addr_t addr) {
int s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
if (s == -1) {
return 0;
}
// Attempt to connect to the address. If the connection succeeds and getsockname returns the
// same then the address is already assigned to the system and we can't use it.
struct sockaddr_in sin = {.sin_family = AF_INET, .sin_addr = {addr}, .sin_port = 53};
socklen_t len = sizeof(sin);
bool inuse = connect(s, (struct sockaddr*)&sin, sizeof(sin)) == 0 &&
getsockname(s, (struct sockaddr*)&sin, &len) == 0 && (size_t)len >= sizeof(sin) &&
sin.sin_addr.s_addr == addr;
close(s);
return !inuse;
}
// Picks a free IPv4 address, starting from ip and trying all addresses in the prefix in order.
// ip - the IP address from the configuration file
// prefixlen - the length of the prefix from which addresses may be selected.
// returns: the IPv4 address, or INADDR_NONE if no addresses were available
in_addr_t ClatdController::selectIpv4Address(const in_addr ip, int16_t prefixlen) {
// Don't accept prefixes that are too large because we scan addresses one by one.
if (prefixlen < 16 || prefixlen > 32) {
return INADDR_NONE;
}
// All these are in host byte order.
in_addr_t mask = 0xffffffff >> (32 - prefixlen) << (32 - prefixlen);
in_addr_t ipv4 = ntohl(ip.s_addr);
in_addr_t first_ipv4 = ipv4;
in_addr_t prefix = ipv4 & mask;
// Pick the first IPv4 address in the pool, wrapping around if necessary.
// So, for example, 192.0.0.4 -> 192.0.0.5 -> 192.0.0.6 -> 192.0.0.7 -> 192.0.0.0.
do {
if (isIpv4AddressFreeFunc(htonl(ipv4))) {
return htonl(ipv4);
}
ipv4 = prefix | ((ipv4 + 1) & ~mask);
} while (ipv4 != first_ipv4);
return INADDR_NONE;
}
// Alters the bits in the IPv6 address to make them checksum neutral with v4 and nat64Prefix.
void ClatdController::makeChecksumNeutral(in6_addr* v6, const in_addr v4,
const in6_addr& nat64Prefix) {
// Fill last 8 bytes of IPv6 address with random bits.
arc4random_buf(&v6->s6_addr[8], 8);
// Make the IID checksum-neutral. That is, make it so that:
// checksum(Local IPv4 | Remote IPv4) = checksum(Local IPv6 | Remote IPv6)
// in other words (because remote IPv6 = NAT64 prefix | Remote IPv4):
// checksum(Local IPv4) = checksum(Local IPv6 | NAT64 prefix)
// Do this by adjusting the two bytes in the middle of the IID.
uint16_t middlebytes = (v6->s6_addr[11] << 8) + v6->s6_addr[12];
uint32_t c1 = ip_checksum_add(0, &v4, sizeof(v4));
uint32_t c2 = ip_checksum_add(0, &nat64Prefix, sizeof(nat64Prefix)) +
ip_checksum_add(0, v6, sizeof(*v6));
uint16_t delta = ip_checksum_adjust(middlebytes, c1, c2);
v6->s6_addr[11] = delta >> 8;
v6->s6_addr[12] = delta & 0xff;
}
// Picks a random interface ID that is checksum neutral with the IPv4 address and the NAT64 prefix.
int ClatdController::generateIpv6Address(const char* iface, const in_addr v4,
const in6_addr& nat64Prefix, in6_addr* v6) {
unique_fd s(socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, 0));
if (s == -1) return -errno;
if (setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE, iface, strlen(iface) + 1) == -1) {
return -errno;
}
sockaddr_in6 sin6 = {.sin6_family = AF_INET6, .sin6_addr = nat64Prefix};
if (connect(s, reinterpret_cast<struct sockaddr*>(&sin6), sizeof(sin6)) == -1) {
return -errno;
}
socklen_t len = sizeof(sin6);
if (getsockname(s, reinterpret_cast<struct sockaddr*>(&sin6), &len) == -1) {
return -errno;
}
*v6 = sin6.sin6_addr;
if (IN6_IS_ADDR_UNSPECIFIED(v6) || IN6_IS_ADDR_LOOPBACK(v6) || IN6_IS_ADDR_LINKLOCAL(v6) ||
IN6_IS_ADDR_SITELOCAL(v6) || IN6_IS_ADDR_ULA(v6)) {
return -ENETUNREACH;
}
makeChecksumNeutral(v6, v4, nat64Prefix);
return 0;
}
void ClatdController::maybeStartBpf(const ClatdTracker& tracker) {
if (mClatEbpfMode == ClatEbpfDisabled) return;
int rv = hardwareAddressType(tracker.iface);
if (rv < 0) {
ALOGE("hardwareAddressType(%s[%d]) failure: %s", tracker.iface, tracker.ifIndex,
strerror(-rv));
return;
}
bool isEthernet;
switch (rv) {
case ARPHRD_ETHER:
isEthernet = true;
break;
case ARPHRD_RAWIP: // in Linux 4.14+ rmnet support was upstreamed and this is 519
case 530: // this is ARPHRD_RAWIP on some Android 4.9 kernels with rmnet
isEthernet = false;
break;
default:
ALOGE("hardwareAddressType(%s[%d]) returned unknown type %d.", tracker.iface,
tracker.ifIndex, rv);
return;
}
rv = getClatIngressProgFd(isEthernet);
if (rv < 0) {
ALOGE("getClatIngressProgFd(%d) failure: %s", isEthernet, strerror(-rv));
return;
}
unique_fd progFd(rv);
ClatIngressKey key = {
.iif = tracker.ifIndex,
.pfx96 = tracker.pfx96,
.local6 = tracker.v6,
};
ClatIngressValue value = {
// TODO: move all the clat code to eBPF and remove the tun interface entirely.
.oif = tracker.v4ifIndex,
.local4 = tracker.v4,
};
auto ret = mClatIngressMap.writeValue(key, value, BPF_ANY);
if (!isOk(ret)) {
ALOGE("mClatIngress.Map.writeValue failure: %s", strerror(ret.code()));
return;
}
// We do tc setup *after* populating map, so scanning through map
// can always be used to tell us what needs cleanup.
rv = tcQdiscAddDevClsact(mNetlinkFd, tracker.ifIndex);
if (rv) {
ALOGE("tcQdiscAddDevClsact(%d[%s]) failure: %s", tracker.ifIndex, tracker.iface,
strerror(-rv));
ret = mClatIngressMap.deleteValue(key);
if (!isOk(ret)) ALOGE("mClatIngressMap.deleteValue failure: %s", strerror(ret.code()));
return;
}
rv = tcFilterAddDevBpf(mNetlinkFd, tracker.ifIndex, progFd, isEthernet);
if (rv) {
if ((rv == -ENOENT) && (mClatEbpfMode == ClatEbpfMaybe)) {
ALOGI("tcFilterAddDevBpf(%d[%s], %d): %s", tracker.ifIndex, tracker.iface, isEthernet,
strerror(-rv));
} else {
ALOGE("tcFilterAddDevBpf(%d[%s], %d) failure: %s", tracker.ifIndex, tracker.iface,
isEthernet, strerror(-rv));
}
rv = tcQdiscDelDevClsact(mNetlinkFd, tracker.ifIndex);
if (rv)
ALOGE("tcQdiscDelDevClsact(%d[%s]) failure: %s", tracker.ifIndex, tracker.iface,
strerror(-rv));
ret = mClatIngressMap.deleteValue(key);
if (!isOk(ret)) ALOGE("mClatIngressMap.deleteValue failure: %s", strerror(ret.code()));
return;
}
// success
}
void ClatdController::maybeSetIptablesDropRule(bool add, const char* pfx96Str, const char* v6Str) {
if (mClatEbpfMode == ClatEbpfDisabled) return;
std::string cmd = StringPrintf(
"*raw\n"
"%s %s -s %s/96 -d %s -j DROP\n"
"COMMIT\n",
(add ? "-A" : "-D"), LOCAL_RAW_PREROUTING, pfx96Str, v6Str);
iptablesRestoreFunction(V6, cmd);
}
void ClatdController::maybeStopBpf(const ClatdTracker& tracker) {
if (mClatEbpfMode == ClatEbpfDisabled) return;
// No need to remove filter, since we remove qdisc it is attached to,
// which automatically removes everything attached to the qdisc.
int rv = tcQdiscDelDevClsact(mNetlinkFd, tracker.ifIndex);
if (rv < 0)
ALOGE("tcQdiscDelDevClsact(%d[%s]) failure: %s", tracker.ifIndex, tracker.iface,
strerror(-rv));
// We cleanup map last, so scanning through map can be used to
// determine what still needs cleanup.
ClatIngressKey key = {
.iif = tracker.ifIndex,
.pfx96 = tracker.pfx96,
.local6 = tracker.v6,
};
auto ret = mClatIngressMap.deleteValue(key);
if (!isOk(ret)) ALOGE("mClatIngressMap.deleteValue failure: %s", strerror(ret.code()));
}
// Finds the tracker of the clatd running on interface |interface|, or nullptr if clatd has not been
// started on |interface|.
ClatdController::ClatdTracker* ClatdController::getClatdTracker(const std::string& interface) {
auto it = mClatdTrackers.find(interface);
return (it == mClatdTrackers.end() ? nullptr : &it->second);
}
// Initializes a ClatdTracker for the specified interface.
int ClatdController::ClatdTracker::init(unsigned networkId, const std::string& interface,
const std::string& v4interface,
const std::string& nat64Prefix) {
netId = networkId;
fwmark.netId = netId;
fwmark.explicitlySelected = true;
fwmark.protectedFromVpn = true;
fwmark.permission = PERMISSION_SYSTEM;
snprintf(fwmarkString, sizeof(fwmarkString), "0x%x", fwmark.intValue);
snprintf(netIdString, sizeof(netIdString), "%u", netId);
strlcpy(iface, interface.c_str(), sizeof(iface));
ifIndex = if_nametoindex(iface);
strlcpy(v4iface, v4interface.c_str(), sizeof(v4iface));
v4ifIndex = if_nametoindex(v4iface);
// Pass in everything that clatd needs: interface, a netid to use for DNS lookups, a fwmark for
// outgoing packets, the NAT64 prefix, and the IPv4 and IPv6 addresses.
// Validate the prefix and strip off the prefix length.
uint8_t family;
uint8_t prefixLen;
int res = parsePrefix(nat64Prefix.c_str(), &family, &pfx96, sizeof(pfx96), &prefixLen);
// clatd only supports /96 prefixes.
if (res != sizeof(pfx96)) return res;
if (family != AF_INET6) return -EAFNOSUPPORT;
if (prefixLen != 96) return -EINVAL;
if (!inet_ntop(AF_INET6, &pfx96, pfx96String, sizeof(pfx96String))) return -errno;
// Pick an IPv4 address.
// TODO: this picks the address based on other addresses that are assigned to interfaces, but
// the address is only actually assigned to an interface once clatd starts up. So we could end
// up with two clatd instances with the same IPv4 address.
// Stop doing this and instead pick a free one from the kV4Addr pool.
v4 = {selectIpv4Address(kV4Addr, kV4AddrLen)};
if (v4.s_addr == INADDR_NONE) {
ALOGE("No free IPv4 address in %s/%d", kV4AddrString, kV4AddrLen);
return -EADDRNOTAVAIL;
}
if (!inet_ntop(AF_INET, &v4, v4Str, sizeof(v4Str))) return -errno;
// Generate a checksum-neutral IID.
if (generateIpv6Address(iface, v4, pfx96, &v6)) {
ALOGE("Unable to find global source address on %s for %s", iface, pfx96String);
return -EADDRNOTAVAIL;
}
if (!inet_ntop(AF_INET6, &v6, v6Str, sizeof(v6Str))) return -errno;
ALOGD("starting clatd on %s v4=%s v6=%s pfx96=%s", iface, v4Str, v6Str, pfx96String);
return 0;
}
int ClatdController::startClatd(const std::string& interface, const std::string& nat64Prefix,
std::string* v6Str) {
std::lock_guard guard(mutex);
// 1. fail if pre-existing tracker already exists
ClatdTracker* existing = getClatdTracker(interface);
if (existing != nullptr) {
ALOGE("clatd pid=%d already started on %s", existing->pid, interface.c_str());
return -EBUSY;
}
// 2. get network id associated with this external interface
unsigned networkId = mNetCtrl->getNetworkForInterface(interface.c_str());
if (networkId == NETID_UNSET) {
ALOGE("Interface %s not assigned to any netId", interface.c_str());
return -ENODEV;
}
// 3. open the tun device in non blocking mode as required by clatd
int res = open("/dev/tun", O_RDWR | O_NONBLOCK | O_CLOEXEC);
if (res == -1) {
res = errno;
ALOGE("open of tun device failed (%s)", strerror(res));
return -res;
}
unique_fd tmpTunFd(res);
// 4. create the v4-... tun interface
std::string v4interface("v4-");
v4interface += interface;
struct ifreq ifr = {
.ifr_flags = IFF_TUN,
};
strlcpy(ifr.ifr_name, v4interface.c_str(), sizeof(ifr.ifr_name));
res = ioctl(tmpTunFd, TUNSETIFF, &ifr, sizeof(ifr));
if (res == -1) {
res = errno;
ALOGE("ioctl(TUNSETIFF) failed (%s)", strerror(res));
return -res;
}
// 5. initialize tracker object
ClatdTracker tracker;
int ret = tracker.init(networkId, interface, v4interface, nat64Prefix);
if (ret) return ret;
// 6. create a throwaway socket to reserve a file descriptor number
res = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC, 0);
if (res == -1) {
res = errno;
ALOGE("socket(ipv6/udp) failed (%s)", strerror(res));
return -res;
}
unique_fd passedTunFd(res);
// 7. this is the FD we'll pass to clatd on the cli, so need it as a string
char passedTunFdStr[INT32_STRLEN];
snprintf(passedTunFdStr, sizeof(passedTunFdStr), "%d", passedTunFd.get());
// 8. we're going to use this as argv[0] to clatd to make ps output more useful
std::string progname("clatd-");
progname += tracker.iface;
// clang-format off
const char* args[] = {progname.c_str(),
"-i", tracker.iface,
"-n", tracker.netIdString,
"-m", tracker.fwmarkString,
"-p", tracker.pfx96String,
"-4", tracker.v4Str,
"-6", tracker.v6Str,
"-t", passedTunFdStr,
nullptr};
// clang-format on
// 9. register vfork requirement
posix_spawnattr_t attr;
res = posix_spawnattr_init(&attr);
if (res) {
ALOGE("posix_spawnattr_init failed (%s)", strerror(res));
return -res;
}
const android::base::ScopeGuard attrGuard = [&] { posix_spawnattr_destroy(&attr); };
res = posix_spawnattr_setflags(&attr, POSIX_SPAWN_USEVFORK);
if (res) {
ALOGE("posix_spawnattr_setflags failed (%s)", strerror(res));
return -res;
}
// 10. register dup2() action: this is what 'clears' the CLOEXEC flag
// on the tun fd that we want the child clatd process to inherit
// (this will happen after the vfork, and before the execve)
posix_spawn_file_actions_t fa;
res = posix_spawn_file_actions_init(&fa);
if (res) {
ALOGE("posix_spawn_file_actions_init failed (%s)", strerror(res));
return -res;
}
const android::base::ScopeGuard faGuard = [&] { posix_spawn_file_actions_destroy(&fa); };
res = posix_spawn_file_actions_adddup2(&fa, tmpTunFd, passedTunFd);
if (res) {
ALOGE("posix_spawn_file_actions_adddup2 failed (%s)", strerror(res));
return -res;
}
// 11. If necessary, add the drop rule for iptables.
maybeSetIptablesDropRule(true, tracker.pfx96String, tracker.v6Str);
// 12. actually perform vfork/dup2/execve
res = posix_spawn(&tracker.pid, kClatdPath, &fa, &attr, (char* const*)args, nullptr);
if (res) {
ALOGE("posix_spawn failed (%s)", strerror(res));
return -res;
}
// 13. configure eBPF offload - if possible
maybeStartBpf(tracker);
mClatdTrackers[interface] = tracker;
ALOGD("clatd started on %s", interface.c_str());
*v6Str = tracker.v6Str;
return 0;
}
int ClatdController::stopClatd(const std::string& interface) {
std::lock_guard guard(mutex);
ClatdTracker* tracker = getClatdTracker(interface);
if (tracker == nullptr) {
ALOGE("clatd already stopped");
return -ENODEV;
}
ALOGD("Stopping clatd pid=%d on %s", tracker->pid, interface.c_str());
maybeStopBpf(*tracker);
kill(tracker->pid, SIGTERM);
waitpid(tracker->pid, nullptr, 0);
maybeSetIptablesDropRule(false, tracker->pfx96String, tracker->v6Str);
mClatdTrackers.erase(interface);
ALOGD("clatd on %s stopped", interface.c_str());
return 0;
}
void ClatdController::dump(DumpWriter& dw) {
std::lock_guard guard(mutex);
ScopedIndent clatdIndent(dw);
dw.println("ClatdController");
{
ScopedIndent trackerIndent(dw);
dw.println("Trackers: iif[iface] nat64Prefix v6Addr -> v4Addr v4iif[v4iface] [netId]");
ScopedIndent trackerDetailIndent(dw);
for (const auto& pair : mClatdTrackers) {
const ClatdTracker& tracker = pair.second;
dw.println("%u[%s] %s/96 %s -> %s %u[%s] [%u]", tracker.ifIndex, tracker.iface,
tracker.pfx96String, tracker.v6Str, tracker.v4Str, tracker.v4ifIndex,
tracker.v4iface, tracker.netId);
}
}
int mapFd = getClatIngressMapFd();
if (mapFd < 0) return; // if unsupported just don't dump anything
BpfMap<ClatIngressKey, ClatIngressValue> configMap(mapFd);
ScopedIndent bpfIndent(dw);
dw.println("BPF ingress map: iif(iface) nat64Prefix v6Addr -> v4Addr oif(iface)");
ScopedIndent bpfDetailIndent(dw);
const auto printClatMap = [&dw](const ClatIngressKey& key, const ClatIngressValue& value,
const BpfMap<ClatIngressKey, ClatIngressValue>&) {
char iifStr[IFNAMSIZ] = "?";
char pfx96Str[INET6_ADDRSTRLEN] = "?";
char local6Str[INET6_ADDRSTRLEN] = "?";
char local4Str[INET_ADDRSTRLEN] = "?";
char oifStr[IFNAMSIZ] = "?";
if_indextoname(key.iif, iifStr);
inet_ntop(AF_INET6, &key.pfx96, pfx96Str, sizeof(pfx96Str));
inet_ntop(AF_INET6, &key.local6, local6Str, sizeof(local6Str));
inet_ntop(AF_INET, &value.local4, local4Str, sizeof(local4Str));
if_indextoname(value.oif, oifStr);
dw.println("%u(%s) %s/96 %s -> %s %u(%s)", key.iif, iifStr, pfx96Str, local6Str, local4Str,
value.oif, oifStr);
return netdutils::status::ok;
};
auto res = configMap.iterateWithValue(printClatMap);
if (!isOk(res)) {
dw.println("Error printing BPF map: %s", res.msg().c_str());
}
}
auto ClatdController::isIpv4AddressFreeFunc = isIpv4AddressFree;
auto ClatdController::iptablesRestoreFunction = execIptablesRestore;
} // namespace net
} // namespace android