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/*
* Copyright (C) 2020 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.
*/
package com.android.net.module.util.ip;
import static com.android.net.module.util.netlink.ConntrackMessage.DYING_MASK;
import static com.android.net.module.util.netlink.ConntrackMessage.ESTABLISHED_MASK;
import android.annotation.NonNull;
import android.os.Handler;
import android.system.OsConstants;
import com.android.internal.annotations.VisibleForTesting;
import com.android.net.module.util.SharedLog;
import com.android.net.module.util.netlink.ConntrackMessage;
import com.android.net.module.util.netlink.NetlinkConstants;
import com.android.net.module.util.netlink.NetlinkMessage;
import java.util.Objects;
/**
* ConntrackMonitor.
*
* Monitors the netfilter conntrack notifications and presents to callers
* ConntrackEvents describing each event.
*
* @hide
*/
public class ConntrackMonitor extends NetlinkMonitor {
private static final String TAG = ConntrackMonitor.class.getSimpleName();
private static final boolean DBG = false;
private static final boolean VDBG = false;
// Reference kernel/uapi/linux/netfilter/nfnetlink_compat.h
public static final int NF_NETLINK_CONNTRACK_NEW = 1;
public static final int NF_NETLINK_CONNTRACK_UPDATE = 2;
public static final int NF_NETLINK_CONNTRACK_DESTROY = 4;
// The socket receive buffer size in bytes. If too many conntrack messages are sent too
// quickly, the conntrack messages can overflow the socket receive buffer. This can happen
// if too many connections are disconnected by losing network and so on. Use a large-enough
// buffer to avoid the error ENOBUFS while listening to the conntrack messages.
private static final int SOCKET_RECV_BUFSIZE = 6 * 1024 * 1024;
/**
* A class for describing parsed netfilter conntrack events.
*/
public static class ConntrackEvent {
/**
* Conntrack event type.
*/
public final short msgType;
/**
* Original direction conntrack tuple.
*/
public final ConntrackMessage.Tuple tupleOrig;
/**
* Reply direction conntrack tuple.
*/
public final ConntrackMessage.Tuple tupleReply;
/**
* Connection status. A bitmask of ip_conntrack_status enum flags.
*/
public final int status;
/**
* Conntrack timeout.
*/
public final int timeoutSec;
public ConntrackEvent(ConntrackMessage msg) {
this.msgType = msg.getHeader().nlmsg_type;
this.tupleOrig = msg.tupleOrig;
this.tupleReply = msg.tupleReply;
this.status = msg.status;
this.timeoutSec = msg.timeoutSec;
}
@VisibleForTesting
public ConntrackEvent(short msgType, ConntrackMessage.Tuple tupleOrig,
ConntrackMessage.Tuple tupleReply, int status, int timeoutSec) {
this.msgType = msgType;
this.tupleOrig = tupleOrig;
this.tupleReply = tupleReply;
this.status = status;
this.timeoutSec = timeoutSec;
}
@Override
@VisibleForTesting
public boolean equals(Object o) {
if (!(o instanceof ConntrackEvent)) return false;
ConntrackEvent that = (ConntrackEvent) o;
return this.msgType == that.msgType
&& Objects.equals(this.tupleOrig, that.tupleOrig)
&& Objects.equals(this.tupleReply, that.tupleReply)
&& this.status == that.status
&& this.timeoutSec == that.timeoutSec;
}
@Override
public int hashCode() {
return Objects.hash(msgType, tupleOrig, tupleReply, status, timeoutSec);
}
@Override
public String toString() {
return "ConntrackEvent{"
+ "msg_type{"
+ NetlinkConstants.stringForNlMsgType(msgType, OsConstants.NETLINK_NETFILTER)
+ "}, "
+ "tuple_orig{" + tupleOrig + "}, "
+ "tuple_reply{" + tupleReply + "}, "
+ "status{"
+ status + "(" + ConntrackMessage.stringForIpConntrackStatus(status) + ")"
+ "}, "
+ "timeout_sec{" + Integer.toUnsignedLong(timeoutSec) + "}"
+ "}";
}
/**
* Check the established NAT session conntrack message.
*
* @param msg the conntrack message to check.
* @return true if an established NAT message, false if not.
*/
public static boolean isEstablishedNatSession(@NonNull ConntrackMessage msg) {
if (msg.getMessageType() != NetlinkConstants.IPCTNL_MSG_CT_NEW) return false;
if (msg.tupleOrig == null) return false;
if (msg.tupleReply == null) return false;
if (msg.timeoutSec == 0) return false;
if ((msg.status & ESTABLISHED_MASK) != ESTABLISHED_MASK) return false;
return true;
}
/**
* Check the dying NAT session conntrack message.
* Note that IPCTNL_MSG_CT_DELETE event has no CTA_TIMEOUT attribute.
*
* @param msg the conntrack message to check.
* @return true if a dying NAT message, false if not.
*/
public static boolean isDyingNatSession(@NonNull ConntrackMessage msg) {
if (msg.getMessageType() != NetlinkConstants.IPCTNL_MSG_CT_DELETE) return false;
if (msg.tupleOrig == null) return false;
if (msg.tupleReply == null) return false;
if (msg.timeoutSec != 0) return false;
if ((msg.status & DYING_MASK) != DYING_MASK) return false;
return true;
}
}
/**
* A callback to caller for conntrack event.
*/
public interface ConntrackEventConsumer {
/**
* Every conntrack event received on the netlink socket is passed in
* here.
*/
void accept(@NonNull ConntrackEvent event);
}
private final ConntrackEventConsumer mConsumer;
public ConntrackMonitor(@NonNull Handler h, @NonNull SharedLog log,
@NonNull ConntrackEventConsumer cb) {
super(h, log, TAG, OsConstants.NETLINK_NETFILTER, NF_NETLINK_CONNTRACK_NEW
| NF_NETLINK_CONNTRACK_UPDATE | NF_NETLINK_CONNTRACK_DESTROY, SOCKET_RECV_BUFSIZE);
mConsumer = cb;
}
@Override
public void processNetlinkMessage(NetlinkMessage nlMsg, final long whenMs) {
if (!(nlMsg instanceof ConntrackMessage)) {
mLog.e("non-conntrack msg: " + nlMsg);
return;
}
final ConntrackMessage conntrackMsg = (ConntrackMessage) nlMsg;
if (!(ConntrackEvent.isEstablishedNatSession(conntrackMsg)
|| ConntrackEvent.isDyingNatSession(conntrackMsg))) {
return;
}
mConsumer.accept(new ConntrackEvent(conntrackMsg));
}
}
|
