/*
 * Copyright (C) 2015 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 android.system.OsConstants;

import java.nio.ByteBuffer;


/**
 * Various constants and static helper methods for netlink communications.
 *
 * Values taken from:
 *
 *     <linux_src>/include/uapi/linux/netlink.h
 *     <linux_src>/include/uapi/linux/rtnetlink.h
 *
 * @hide
 */
public class NetlinkConstants {
    private NetlinkConstants() {}

    public static final int NLA_ALIGNTO = 4;
    /**
     * Flag for dumping struct tcp_info.
     * Corresponding to enum definition in external/strace/linux/inet_diag.h.
     */
    public static final int INET_DIAG_MEMINFO = 1;

    public static final int SOCKDIAG_MSG_HEADER_SIZE =
            StructNlMsgHdr.STRUCT_SIZE + StructInetDiagMsg.STRUCT_SIZE;

    public static final int alignedLengthOf(short length) {
        final int intLength = (int) length & 0xffff;
        return alignedLengthOf(intLength);
    }

    public static final int alignedLengthOf(int length) {
        if (length <= 0) { return 0; }
        return (((length + NLA_ALIGNTO - 1) / NLA_ALIGNTO) * NLA_ALIGNTO);
    }

    public static String stringForAddressFamily(int family) {
        if (family == OsConstants.AF_INET) { return "AF_INET"; }
        if (family == OsConstants.AF_INET6) { return "AF_INET6"; }
        if (family == OsConstants.AF_NETLINK) { return "AF_NETLINK"; }
        return String.valueOf(family);
    }

    public static String stringForProtocol(int protocol) {
        if (protocol == OsConstants.IPPROTO_TCP) { return "IPPROTO_TCP"; }
        if (protocol == OsConstants.IPPROTO_UDP) { return "IPPROTO_UDP"; }
        return String.valueOf(protocol);
    }

    public static String hexify(byte[] bytes) {
        if (bytes == null) { return "(null)"; }
        return toHexString(bytes, 0, bytes.length);
    }

    public static String hexify(ByteBuffer buffer) {
        if (buffer == null) { return "(null)"; }
        return toHexString(
                buffer.array(), buffer.position(), buffer.remaining());
    }

    // Known values for struct nlmsghdr nlm_type.
    public static final short NLMSG_NOOP         = 1;   // Nothing
    public static final short NLMSG_ERROR        = 2;   // Error
    public static final short NLMSG_DONE         = 3;   // End of a dump
    public static final short NLMSG_OVERRUN      = 4;   // Data lost
    public static final short NLMSG_MAX_RESERVED = 15;  // Max reserved value

    public static final short RTM_NEWLINK        = 16;
    public static final short RTM_DELLINK        = 17;
    public static final short RTM_GETLINK        = 18;
    public static final short RTM_SETLINK        = 19;
    public static final short RTM_NEWADDR        = 20;
    public static final short RTM_DELADDR        = 21;
    public static final short RTM_GETADDR        = 22;
    public static final short RTM_NEWROUTE       = 24;
    public static final short RTM_DELROUTE       = 25;
    public static final short RTM_GETROUTE       = 26;
    public static final short RTM_NEWNEIGH       = 28;
    public static final short RTM_DELNEIGH       = 29;
    public static final short RTM_GETNEIGH       = 30;
    public static final short RTM_NEWRULE        = 32;
    public static final short RTM_DELRULE        = 33;
    public static final short RTM_GETRULE        = 34;
    public static final short RTM_NEWNDUSEROPT   = 68;

    /* see &lt;linux_src&gt;/include/uapi/linux/sock_diag.h */
    public static final short SOCK_DIAG_BY_FAMILY = 20;

    // Netlink groups.
    public static final int RTNLGRP_ND_USEROPT = 20;
    public static final int RTMGRP_ND_USEROPT = 1 << (RTNLGRP_ND_USEROPT - 1);

    public static String stringForNlMsgType(short nlm_type) {
        switch (nlm_type) {
            case NLMSG_NOOP: return "NLMSG_NOOP";
            case NLMSG_ERROR: return "NLMSG_ERROR";
            case NLMSG_DONE: return "NLMSG_DONE";
            case NLMSG_OVERRUN: return "NLMSG_OVERRUN";
            case RTM_NEWLINK: return "RTM_NEWLINK";
            case RTM_DELLINK: return "RTM_DELLINK";
            case RTM_GETLINK: return "RTM_GETLINK";
            case RTM_SETLINK: return "RTM_SETLINK";
            case RTM_NEWADDR: return "RTM_NEWADDR";
            case RTM_DELADDR: return "RTM_DELADDR";
            case RTM_GETADDR: return "RTM_GETADDR";
            case RTM_NEWROUTE: return "RTM_NEWROUTE";
            case RTM_DELROUTE: return "RTM_DELROUTE";
            case RTM_GETROUTE: return "RTM_GETROUTE";
            case RTM_NEWNEIGH: return "RTM_NEWNEIGH";
            case RTM_DELNEIGH: return "RTM_DELNEIGH";
            case RTM_GETNEIGH: return "RTM_GETNEIGH";
            case RTM_NEWRULE: return "RTM_NEWRULE";
            case RTM_DELRULE: return "RTM_DELRULE";
            case RTM_GETRULE: return "RTM_GETRULE";
            case RTM_NEWNDUSEROPT: return "RTM_NEWNDUSEROPT";
            default:
                return "unknown RTM type: " + String.valueOf(nlm_type);
        }
    }

    private static final char[] HEX_DIGITS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
            'A', 'B', 'C', 'D', 'E', 'F' };
    /**
     * Convert a byte array to a hexadecimal string.
     */
    public static String toHexString(byte[] array, int offset, int length) {
        char[] buf = new char[length * 2];

        int bufIndex = 0;
        for (int i = offset; i < offset + length; i++) {
            byte b = array[i];
            buf[bufIndex++] = HEX_DIGITS[(b >>> 4) & 0x0F];
            buf[bufIndex++] = HEX_DIGITS[b & 0x0F];
        }

        return new String(buf);
    }
}