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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 com.android.net.module.util.netlink;
import android.system.OsConstants;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import java.nio.ByteBuffer;
/**
* NetlinkMessage base class for other, more specific netlink message types.
*
* Classes that extend NetlinkMessage should:
* - implement a public static parse(StructNlMsgHdr, ByteBuffer) method
* - returning either null (parse errors) or a new object of the subclass
* type (cast-able to NetlinkMessage)
*
* NetlinkMessage.parse() should be updated to know which nlmsg_type values
* correspond with which message subclasses.
*
* @hide
*/
public class NetlinkMessage {
private static final String TAG = "NetlinkMessage";
/**
* Parsing netlink messages for reserved control message or specific netlink message. The
* netlink family is required for parsing specific netlink message. See man-pages/netlink.
*/
@Nullable
public static NetlinkMessage parse(@NonNull ByteBuffer byteBuffer, int nlFamily) {
final int startPosition = (byteBuffer != null) ? byteBuffer.position() : -1;
final StructNlMsgHdr nlmsghdr = StructNlMsgHdr.parse(byteBuffer);
if (nlmsghdr == null) {
return null;
}
final int messageLength = NetlinkConstants.alignedLengthOf(nlmsghdr.nlmsg_len);
final int payloadLength = messageLength - StructNlMsgHdr.STRUCT_SIZE;
if (payloadLength < 0 || payloadLength > byteBuffer.remaining()) {
// Malformed message or runt buffer. Pretend the buffer was consumed.
byteBuffer.position(byteBuffer.limit());
return null;
}
// Reserved control messages. The netlink family is ignored.
// See NLMSG_MIN_TYPE in include/uapi/linux/netlink.h.
if (nlmsghdr.nlmsg_type <= NetlinkConstants.NLMSG_MAX_RESERVED) {
return parseCtlMessage(nlmsghdr, byteBuffer, payloadLength);
}
// Netlink family messages. The netlink family is required. Note that the reason for using
// if-statement is that switch-case can't be used because the OsConstants.NETLINK_* are
// not constant.
final NetlinkMessage parsed;
if (nlFamily == OsConstants.NETLINK_ROUTE) {
parsed = parseRtMessage(nlmsghdr, byteBuffer);
} else if (nlFamily == OsConstants.NETLINK_INET_DIAG) {
parsed = parseInetDiagMessage(nlmsghdr, byteBuffer);
} else if (nlFamily == OsConstants.NETLINK_NETFILTER) {
parsed = parseNfMessage(nlmsghdr, byteBuffer);
} else {
parsed = null;
}
// Advance to the end of the message, regardless of whether the parsing code consumed
// all of it or not.
byteBuffer.position(startPosition + messageLength);
return parsed;
}
@NonNull
protected final StructNlMsgHdr mHeader;
public NetlinkMessage(@NonNull StructNlMsgHdr nlmsghdr) {
mHeader = nlmsghdr;
}
@NonNull
public StructNlMsgHdr getHeader() {
return mHeader;
}
@Override
public String toString() {
// The netlink family is not provided to StructNlMsgHdr#toString because NetlinkMessage
// doesn't store the information. So the netlink message type can't be transformed into
// a string by StructNlMsgHdr#toString and just keep as an integer. The specific message
// which inherits NetlinkMessage could override NetlinkMessage#toString and provide the
// specific netlink family to StructNlMsgHdr#toString.
return "NetlinkMessage{" + mHeader.toString() + "}";
}
@NonNull
private static NetlinkMessage parseCtlMessage(@NonNull StructNlMsgHdr nlmsghdr,
@NonNull ByteBuffer byteBuffer, int payloadLength) {
switch (nlmsghdr.nlmsg_type) {
case NetlinkConstants.NLMSG_ERROR:
return (NetlinkMessage) NetlinkErrorMessage.parse(nlmsghdr, byteBuffer);
default: {
// Other netlink control messages. Just parse the header for now,
// pretending the whole message was consumed.
byteBuffer.position(byteBuffer.position() + payloadLength);
return new NetlinkMessage(nlmsghdr);
}
}
}
@Nullable
private static NetlinkMessage parseRtMessage(@NonNull StructNlMsgHdr nlmsghdr,
@NonNull ByteBuffer byteBuffer) {
switch (nlmsghdr.nlmsg_type) {
case NetlinkConstants.RTM_NEWLINK:
case NetlinkConstants.RTM_DELLINK:
return (NetlinkMessage) RtNetlinkLinkMessage.parse(nlmsghdr, byteBuffer);
case NetlinkConstants.RTM_NEWADDR:
case NetlinkConstants.RTM_DELADDR:
return (NetlinkMessage) RtNetlinkAddressMessage.parse(nlmsghdr, byteBuffer);
case NetlinkConstants.RTM_NEWROUTE:
case NetlinkConstants.RTM_DELROUTE:
return (NetlinkMessage) RtNetlinkRouteMessage.parse(nlmsghdr, byteBuffer);
case NetlinkConstants.RTM_NEWNEIGH:
case NetlinkConstants.RTM_DELNEIGH:
case NetlinkConstants.RTM_GETNEIGH:
return (NetlinkMessage) RtNetlinkNeighborMessage.parse(nlmsghdr, byteBuffer);
case NetlinkConstants.RTM_NEWNDUSEROPT:
return (NetlinkMessage) NduseroptMessage.parse(nlmsghdr, byteBuffer);
default: return null;
}
}
@Nullable
private static NetlinkMessage parseInetDiagMessage(@NonNull StructNlMsgHdr nlmsghdr,
@NonNull ByteBuffer byteBuffer) {
switch (nlmsghdr.nlmsg_type) {
case NetlinkConstants.SOCK_DIAG_BY_FAMILY:
return (NetlinkMessage) InetDiagMessage.parse(nlmsghdr, byteBuffer);
default: return null;
}
}
@Nullable
private static NetlinkMessage parseNfMessage(@NonNull StructNlMsgHdr nlmsghdr,
@NonNull ByteBuffer byteBuffer) {
switch (nlmsghdr.nlmsg_type) {
case NetlinkConstants.NFNL_SUBSYS_CTNETLINK << 8
| NetlinkConstants.IPCTNL_MSG_CT_NEW:
case NetlinkConstants.NFNL_SUBSYS_CTNETLINK << 8
| NetlinkConstants.IPCTNL_MSG_CT_DELETE:
return (NetlinkMessage) ConntrackMessage.parse(nlmsghdr, byteBuffer);
default: return null;
}
}
}
|
