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.net.netlink.NetlinkConstants;
20 import libcore.io.SizeOf;
21 
22 import java.net.InetAddress;
23 import java.net.UnknownHostException;
24 import java.nio.ByteOrder;
25 import java.nio.ByteBuffer;
26 
27 
28 /**
29  * struct nlattr
30  *
31  * see: <linux_src>/include/uapi/linux/netlink.h
32  *
33  * @hide
34  */
35 public class StructNlAttr {
36     // Already aligned.
37     public static final int NLA_HEADERLEN         = 4;
38 
39     // Return a (length, type) object only, without consuming any bytes in
40     // |byteBuffer| and without copying or interpreting any value bytes.
41     // This is used for scanning over a packed set of struct nlattr's,
42     // looking for instances of a particular type.
peek(ByteBuffer byteBuffer)43     public static StructNlAttr peek(ByteBuffer byteBuffer) {
44         if (byteBuffer == null || byteBuffer.remaining() < NLA_HEADERLEN) {
45             return null;
46         }
47         final int baseOffset = byteBuffer.position();
48 
49         final StructNlAttr struct = new StructNlAttr();
50         struct.nla_len = byteBuffer.getShort();
51         struct.nla_type = byteBuffer.getShort();
52         struct.mByteOrder = byteBuffer.order();
53 
54         byteBuffer.position(baseOffset);
55         if (struct.nla_len < NLA_HEADERLEN) {
56             // Malformed.
57             return null;
58         }
59         return struct;
60     }
61 
parse(ByteBuffer byteBuffer)62     public static StructNlAttr parse(ByteBuffer byteBuffer) {
63         final StructNlAttr struct = peek(byteBuffer);
64         if (struct == null || byteBuffer.remaining() < struct.getAlignedLength()) {
65             return null;
66         }
67 
68         final int baseOffset = byteBuffer.position();
69         byteBuffer.position(baseOffset + NLA_HEADERLEN);
70 
71         int valueLen = ((int) struct.nla_len) & 0xffff;
72         valueLen -= NLA_HEADERLEN;
73         if (valueLen > 0) {
74             struct.nla_value = new byte[valueLen];
75             byteBuffer.get(struct.nla_value, 0, valueLen);
76             byteBuffer.position(baseOffset + struct.getAlignedLength());
77         }
78         return struct;
79     }
80 
81     public short nla_len;
82     public short nla_type;
83     public byte[] nla_value;
84     public ByteOrder mByteOrder;
85 
StructNlAttr()86     public StructNlAttr() {
87         mByteOrder = ByteOrder.nativeOrder();
88     }
89 
getAlignedLength()90     public int getAlignedLength() {
91         return NetlinkConstants.alignedLengthOf(nla_len);
92     }
93 
getValueAsByteBuffer()94     public ByteBuffer getValueAsByteBuffer() {
95         if (nla_value == null) { return null; }
96         final ByteBuffer byteBuffer = ByteBuffer.wrap(nla_value);
97         byteBuffer.order(mByteOrder);
98         return byteBuffer;
99     }
100 
getValueAsInt(int defaultValue)101     public int getValueAsInt(int defaultValue) {
102         final ByteBuffer byteBuffer = getValueAsByteBuffer();
103         if (byteBuffer == null || byteBuffer.remaining() != SizeOf.INT) {
104             return defaultValue;
105         }
106         return getValueAsByteBuffer().getInt();
107     }
108 
getValueAsInetAddress()109     public InetAddress getValueAsInetAddress() {
110         if (nla_value == null) { return null; }
111 
112         try {
113             return InetAddress.getByAddress(nla_value);
114         } catch (UnknownHostException ignored) {
115             return null;
116         }
117     }
118 
pack(ByteBuffer byteBuffer)119     public void pack(ByteBuffer byteBuffer) {
120         final int originalPosition = byteBuffer.position();
121         byteBuffer.putShort(nla_len);
122         byteBuffer.putShort(nla_type);
123         byteBuffer.put(nla_value);
124         byteBuffer.position(originalPosition + getAlignedLength());
125     }
126 
127     @Override
toString()128     public String toString() {
129         return "StructNlAttr{ "
130                 + "nla_len{" + nla_len + "}, "
131                 + "nla_type{" + nla_type + "}, "
132                 + "nla_value{" + NetlinkConstants.hexify(nla_value) + "}, "
133                 + "}";
134     }
135 }
136