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/*
* Copyright (C) 2019 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 java.net.InetAddress;
import java.net.UnknownHostException;
import java.nio.ByteOrder;
import java.nio.ByteBuffer;
/**
* struct nlattr
*
* see: <linux_src>/include/uapi/linux/netlink.h
*
* @hide
*/
public class StructNlAttr {
// Already aligned.
public static final int NLA_HEADERLEN = 4;
public static final int NLA_F_NESTED = (1 << 15);
public static short makeNestedType(short type) {
return (short) (type | NLA_F_NESTED);
}
// Return a (length, type) object only, without consuming any bytes in
// |byteBuffer| and without copying or interpreting any value bytes.
// This is used for scanning over a packed set of struct nlattr's,
// looking for instances of a particular type.
public static StructNlAttr peek(ByteBuffer byteBuffer) {
if (byteBuffer == null || byteBuffer.remaining() < NLA_HEADERLEN) {
return null;
}
final int baseOffset = byteBuffer.position();
// Assume the byte order of the buffer is the expected byte order of the value.
final StructNlAttr struct = new StructNlAttr(byteBuffer.order());
// The byte order of nla_len and nla_type is always native.
final ByteOrder originalOrder = byteBuffer.order();
byteBuffer.order(ByteOrder.nativeOrder());
try {
struct.nla_len = byteBuffer.getShort();
struct.nla_type = byteBuffer.getShort();
} finally {
byteBuffer.order(originalOrder);
}
byteBuffer.position(baseOffset);
if (struct.nla_len < NLA_HEADERLEN) {
// Malformed.
return null;
}
return struct;
}
public static StructNlAttr parse(ByteBuffer byteBuffer) {
final StructNlAttr struct = peek(byteBuffer);
if (struct == null || byteBuffer.remaining() < struct.getAlignedLength()) {
return null;
}
final int baseOffset = byteBuffer.position();
byteBuffer.position(baseOffset + NLA_HEADERLEN);
int valueLen = ((int) struct.nla_len) & 0xffff;
valueLen -= NLA_HEADERLEN;
if (valueLen > 0) {
struct.nla_value = new byte[valueLen];
byteBuffer.get(struct.nla_value, 0, valueLen);
byteBuffer.position(baseOffset + struct.getAlignedLength());
}
return struct;
}
public short nla_len = (short) NLA_HEADERLEN;
public short nla_type;
public byte[] nla_value;
// The byte order used to read/write the value member. Netlink length and
// type members are always read/written in native order.
private ByteOrder mByteOrder = ByteOrder.nativeOrder();
public StructNlAttr() {}
public StructNlAttr(ByteOrder byteOrder) {
mByteOrder = byteOrder;
}
public StructNlAttr(short type, byte value) {
nla_type = type;
setValue(new byte[1]);
nla_value[0] = value;
}
public StructNlAttr(short type, short value) {
this(type, value, ByteOrder.nativeOrder());
}
public StructNlAttr(short type, short value, ByteOrder order) {
this(order);
nla_type = type;
setValue(new byte[Short.BYTES]);
getValueAsByteBuffer().putShort(value);
}
public StructNlAttr(short type, int value) {
this(type, value, ByteOrder.nativeOrder());
}
public StructNlAttr(short type, int value, ByteOrder order) {
this(order);
nla_type = type;
setValue(new byte[Integer.BYTES]);
getValueAsByteBuffer().putInt(value);
}
public StructNlAttr(short type, InetAddress ip) {
nla_type = type;
setValue(ip.getAddress());
}
public StructNlAttr(short type, StructNlAttr... nested) {
this();
nla_type = makeNestedType(type);
int payloadLength = 0;
for (StructNlAttr nla : nested) payloadLength += nla.getAlignedLength();
setValue(new byte[payloadLength]);
final ByteBuffer buf = getValueAsByteBuffer();
for (StructNlAttr nla : nested) {
nla.pack(buf);
}
}
public int getAlignedLength() {
return NetlinkConstants.alignedLengthOf(nla_len);
}
public ByteBuffer getValueAsByteBuffer() {
if (nla_value == null) { return null; }
final ByteBuffer byteBuffer = ByteBuffer.wrap(nla_value);
byteBuffer.order(mByteOrder);
return byteBuffer;
}
public int getValueAsInt(int defaultValue) {
final ByteBuffer byteBuffer = getValueAsByteBuffer();
if (byteBuffer == null || byteBuffer.remaining() != Integer.BYTES) {
return defaultValue;
}
return getValueAsByteBuffer().getInt();
}
public InetAddress getValueAsInetAddress() {
if (nla_value == null) { return null; }
try {
return InetAddress.getByAddress(nla_value);
} catch (UnknownHostException ignored) {
return null;
}
}
public void pack(ByteBuffer byteBuffer) {
final ByteOrder originalOrder = byteBuffer.order();
final int originalPosition = byteBuffer.position();
byteBuffer.order(ByteOrder.nativeOrder());
try {
byteBuffer.putShort(nla_len);
byteBuffer.putShort(nla_type);
if (nla_value != null) byteBuffer.put(nla_value);
} finally {
byteBuffer.order(originalOrder);
}
byteBuffer.position(originalPosition + getAlignedLength());
}
private void setValue(byte[] value) {
nla_value = value;
nla_len = (short) (NLA_HEADERLEN + ((nla_value != null) ? nla_value.length : 0));
}
@Override
public String toString() {
return "StructNlAttr{ "
+ "nla_len{" + nla_len + "}, "
+ "nla_type{" + nla_type + "}, "
+ "nla_value{" + NetlinkConstants.hexify(nla_value) + "}, "
+ "}";
}
}
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