Erik Kline | 6193aa3 | 2015-01-20 12:28:26 +0900 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright (C) 2015 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package android.net.netlink; |
| 18 | |
| 19 | import android.system.Os; |
| 20 | import android.system.OsConstants; |
| 21 | |
| 22 | import java.nio.ByteBuffer; |
| 23 | |
| 24 | |
| 25 | /** |
| 26 | * struct nda_cacheinfo |
| 27 | * |
| 28 | * see: <linux_src>/include/uapi/linux/neighbour.h |
| 29 | * |
| 30 | * @hide |
| 31 | */ |
| 32 | public class StructNdaCacheInfo { |
| 33 | // Already aligned. |
| 34 | public static final int STRUCT_SIZE = 16; |
| 35 | |
| 36 | private static boolean hasAvailableSpace(ByteBuffer byteBuffer) { |
| 37 | return byteBuffer != null && byteBuffer.remaining() >= STRUCT_SIZE; |
| 38 | } |
| 39 | |
| 40 | public static StructNdaCacheInfo parse(ByteBuffer byteBuffer) { |
| 41 | if (!hasAvailableSpace(byteBuffer)) { return null; } |
| 42 | |
| 43 | // The ByteOrder must have already been set by the caller. In most |
| 44 | // cases ByteOrder.nativeOrder() is correct, with the possible |
| 45 | // exception of usage within unittests. |
| 46 | final StructNdaCacheInfo struct = new StructNdaCacheInfo(); |
| 47 | struct.ndm_used = byteBuffer.getInt(); |
| 48 | struct.ndm_confirmed = byteBuffer.getInt(); |
| 49 | struct.ndm_updated = byteBuffer.getInt(); |
| 50 | struct.ndm_refcnt = byteBuffer.getInt(); |
| 51 | return struct; |
| 52 | } |
| 53 | |
| 54 | // TODO: investigate whether this can change during device runtime and |
| 55 | // decide what (if anything) should be done about that. |
| 56 | private static final long CLOCK_TICKS_PER_SECOND = Os.sysconf(OsConstants._SC_CLK_TCK); |
| 57 | |
| 58 | private static long ticksToMilliSeconds(int intClockTicks) { |
| 59 | final long longClockTicks = (long) intClockTicks & 0xffffffff; |
| 60 | return (longClockTicks * 1000) / CLOCK_TICKS_PER_SECOND; |
| 61 | } |
| 62 | |
| 63 | /** |
| 64 | * Explanatory notes, for reference. |
| 65 | * |
| 66 | * Before being returned to user space, the neighbor entry times are |
| 67 | * converted to clock_t's like so: |
| 68 | * |
| 69 | * ndm_used = jiffies_to_clock_t(now - neigh->used); |
| 70 | * ndm_confirmed = jiffies_to_clock_t(now - neigh->confirmed); |
| 71 | * ndm_updated = jiffies_to_clock_t(now - neigh->updated); |
| 72 | * |
| 73 | * meaning that these values are expressed as "clock ticks ago". To |
| 74 | * convert these clock ticks to seconds divide by sysconf(_SC_CLK_TCK). |
| 75 | * When _SC_CLK_TCK is 100, for example, the ndm_* times are expressed |
| 76 | * in centiseconds. |
| 77 | * |
| 78 | * These values are unsigned, but fortunately being expressed as "some |
| 79 | * clock ticks ago", these values are typically very small (and |
| 80 | * 2^31 centiseconds = 248 days). |
| 81 | * |
| 82 | * By observation, it appears that: |
| 83 | * ndm_used: the last time ARP/ND took place for this neighbor |
| 84 | * ndm_confirmed: the last time ARP/ND succeeded for this neighbor OR |
| 85 | * higher layer confirmation (TCP or MSG_CONFIRM) |
| 86 | * was received |
| 87 | * ndm_updated: the time when the current NUD state was entered |
| 88 | */ |
| 89 | public int ndm_used; |
| 90 | public int ndm_confirmed; |
| 91 | public int ndm_updated; |
| 92 | public int ndm_refcnt; |
| 93 | |
| 94 | public StructNdaCacheInfo() {} |
| 95 | |
| 96 | public long lastUsed() { |
| 97 | return ticksToMilliSeconds(ndm_used); |
| 98 | } |
| 99 | |
| 100 | public long lastConfirmed() { |
| 101 | return ticksToMilliSeconds(ndm_confirmed); |
| 102 | } |
| 103 | |
| 104 | public long lastUpdated() { |
| 105 | return ticksToMilliSeconds(ndm_updated); |
| 106 | } |
| 107 | |
| 108 | @Override |
| 109 | public String toString() { |
| 110 | return "NdaCacheInfo{ " |
| 111 | + "ndm_used{" + lastUsed() + "}, " |
| 112 | + "ndm_confirmed{" + lastConfirmed() + "}, " |
| 113 | + "ndm_updated{" + lastUpdated() + "}, " |
| 114 | + "ndm_refcnt{" + ndm_refcnt + "} " |
| 115 | + "}"; |
| 116 | } |
| 117 | } |