| /* |
| * Copyright (C) 2015 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 android.net.netlink; |
| |
| import android.system.Os; |
| import android.system.OsConstants; |
| |
| import java.nio.ByteBuffer; |
| |
| |
| /** |
| * struct nda_cacheinfo |
| * |
| * see: <linux_src>/include/uapi/linux/neighbour.h |
| * |
| * @hide |
| */ |
| public class StructNdaCacheInfo { |
| // Already aligned. |
| public static final int STRUCT_SIZE = 16; |
| |
| private static boolean hasAvailableSpace(ByteBuffer byteBuffer) { |
| return byteBuffer != null && byteBuffer.remaining() >= STRUCT_SIZE; |
| } |
| |
| public static StructNdaCacheInfo parse(ByteBuffer byteBuffer) { |
| if (!hasAvailableSpace(byteBuffer)) { return null; } |
| |
| // The ByteOrder must have already been set by the caller. In most |
| // cases ByteOrder.nativeOrder() is correct, with the possible |
| // exception of usage within unittests. |
| final StructNdaCacheInfo struct = new StructNdaCacheInfo(); |
| struct.ndm_used = byteBuffer.getInt(); |
| struct.ndm_confirmed = byteBuffer.getInt(); |
| struct.ndm_updated = byteBuffer.getInt(); |
| struct.ndm_refcnt = byteBuffer.getInt(); |
| return struct; |
| } |
| |
| // TODO: investigate whether this can change during device runtime and |
| // decide what (if anything) should be done about that. |
| private static final long CLOCK_TICKS_PER_SECOND = Os.sysconf(OsConstants._SC_CLK_TCK); |
| |
| private static long ticksToMilliSeconds(int intClockTicks) { |
| final long longClockTicks = (long) intClockTicks & 0xffffffff; |
| return (longClockTicks * 1000) / CLOCK_TICKS_PER_SECOND; |
| } |
| |
| /** |
| * Explanatory notes, for reference. |
| * |
| * Before being returned to user space, the neighbor entry times are |
| * converted to clock_t's like so: |
| * |
| * ndm_used = jiffies_to_clock_t(now - neigh->used); |
| * ndm_confirmed = jiffies_to_clock_t(now - neigh->confirmed); |
| * ndm_updated = jiffies_to_clock_t(now - neigh->updated); |
| * |
| * meaning that these values are expressed as "clock ticks ago". To |
| * convert these clock ticks to seconds divide by sysconf(_SC_CLK_TCK). |
| * When _SC_CLK_TCK is 100, for example, the ndm_* times are expressed |
| * in centiseconds. |
| * |
| * These values are unsigned, but fortunately being expressed as "some |
| * clock ticks ago", these values are typically very small (and |
| * 2^31 centiseconds = 248 days). |
| * |
| * By observation, it appears that: |
| * ndm_used: the last time ARP/ND took place for this neighbor |
| * ndm_confirmed: the last time ARP/ND succeeded for this neighbor OR |
| * higher layer confirmation (TCP or MSG_CONFIRM) |
| * was received |
| * ndm_updated: the time when the current NUD state was entered |
| */ |
| public int ndm_used; |
| public int ndm_confirmed; |
| public int ndm_updated; |
| public int ndm_refcnt; |
| |
| public StructNdaCacheInfo() {} |
| |
| public long lastUsed() { |
| return ticksToMilliSeconds(ndm_used); |
| } |
| |
| public long lastConfirmed() { |
| return ticksToMilliSeconds(ndm_confirmed); |
| } |
| |
| public long lastUpdated() { |
| return ticksToMilliSeconds(ndm_updated); |
| } |
| |
| @Override |
| public String toString() { |
| return "NdaCacheInfo{ " |
| + "ndm_used{" + lastUsed() + "}, " |
| + "ndm_confirmed{" + lastConfirmed() + "}, " |
| + "ndm_updated{" + lastUpdated() + "}, " |
| + "ndm_refcnt{" + ndm_refcnt + "} " |
| + "}"; |
| } |
| } |