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
17package android.net.netlink;
18
19import android.net.netlink.NetlinkConstants;
20import android.net.netlink.NetlinkErrorMessage;
21import android.net.netlink.RtNetlinkNeighborMessage;
22import android.net.netlink.StructNlAttr;
23import android.net.netlink.StructNlMsgHdr;
24import android.util.Log;
25
26import java.nio.ByteBuffer;
27
28
29/**
30 * NetlinkMessage base class for other, more specific netlink message types.
31 *
32 * Classes that extend NetlinkMessage should:
33 *     - implement a public static parse(StructNlMsgHdr, ByteBuffer) method
34 *     - returning either null (parse errors) or a new object of the subclass
35 *       type (cast-able to NetlinkMessage)
36 *
37 * NetlinkMessage.parse() should be updated to know which nlmsg_type values
38 * correspond with which message subclasses.
39 *
40 * @hide
41 */
42public class NetlinkMessage {
43    private final static String TAG = "NetlinkMessage";
44
45    public static NetlinkMessage parse(ByteBuffer byteBuffer) {
46        final int startPosition = (byteBuffer != null) ? byteBuffer.position() : -1;
47        final StructNlMsgHdr nlmsghdr = StructNlMsgHdr.parse(byteBuffer);
48        if (nlmsghdr == null) {
49            return null;
50        }
51
52        int payloadLength = NetlinkConstants.alignedLengthOf(nlmsghdr.nlmsg_len);
53        payloadLength -= StructNlMsgHdr.STRUCT_SIZE;
54        if (payloadLength < 0 || payloadLength > byteBuffer.remaining()) {
55            // Malformed message or runt buffer.  Pretend the buffer was consumed.
56            byteBuffer.position(byteBuffer.limit());
57            return null;
58        }
59
60        switch (nlmsghdr.nlmsg_type) {
61            //case NetlinkConstants.NLMSG_NOOP:
62            case NetlinkConstants.NLMSG_ERROR:
63                return (NetlinkMessage) NetlinkErrorMessage.parse(nlmsghdr, byteBuffer);
64            case NetlinkConstants.NLMSG_DONE:
65                byteBuffer.position(byteBuffer.position() + payloadLength);
66                return new NetlinkMessage(nlmsghdr);
67            //case NetlinkConstants.NLMSG_OVERRUN:
68            case NetlinkConstants.RTM_NEWNEIGH:
69            case NetlinkConstants.RTM_DELNEIGH:
70            case NetlinkConstants.RTM_GETNEIGH:
71                return (NetlinkMessage) RtNetlinkNeighborMessage.parse(nlmsghdr, byteBuffer);
72            default:
73                if (nlmsghdr.nlmsg_type <= NetlinkConstants.NLMSG_MAX_RESERVED) {
74                    // Netlink control message.  Just parse the header for now,
75                    // pretending the whole message was consumed.
76                    byteBuffer.position(byteBuffer.position() + payloadLength);
77                    return new NetlinkMessage(nlmsghdr);
78                }
79                return null;
80        }
81    }
82
83    protected StructNlMsgHdr mHeader;
84
85    public NetlinkMessage(StructNlMsgHdr nlmsghdr) {
86        mHeader = nlmsghdr;
87    }
88
89    public StructNlMsgHdr getHeader() {
90        return mHeader;
91    }
92
93    @Override
94    public String toString() {
95        return "NetlinkMessage{" + (mHeader == null ? "" : mHeader.toString()) + "}";
96    }
97}
98