src/android/net/apf/ApfConstant.java

/*
 * Copyright (C) 2024 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.apf;

/**
 * The class which declares constants used in ApfFilter and unit tests.
 */
public final class ApfConstant {

    private ApfConstant() {}
    public static final int ETH_HEADER_LEN = 14;
    public static final int ETH_DEST_ADDR_OFFSET = 0;
    public static final int ETH_ETHERTYPE_OFFSET = 12;
    public static final int ETH_TYPE_MIN = 0x0600;
    public static final int ETH_TYPE_MAX = 0xFFFF;
    // TODO: Make these offsets relative to end of link-layer header; don't include ETH_HEADER_LEN.
    public static final int IPV4_TOTAL_LENGTH_OFFSET = ETH_HEADER_LEN + 2;
    public static final int IPV4_FRAGMENT_OFFSET_OFFSET = ETH_HEADER_LEN + 6;
    // Endianness is not an issue for this constant because the APF interpreter always operates in
    // network byte order.
    public static final int IPV4_FRAGMENT_OFFSET_MASK = 0x1fff;
    public static final int IPV4_FRAGMENT_MORE_FRAGS_MASK = 0x2000;
    public static final int IPV4_PROTOCOL_OFFSET = ETH_HEADER_LEN + 9;
    public static final int IPV4_SRC_ADDR_OFFSET = ETH_HEADER_LEN + 12;
    public static final int IPV4_DEST_ADDR_OFFSET = ETH_HEADER_LEN + 16;
    public static final int IPV4_ANY_HOST_ADDRESS = 0;
    public static final int IPV4_BROADCAST_ADDRESS = -1; // 255.255.255.255

    // Traffic class and Flow label are not byte aligned. Luckily we
    // don't care about either value so we'll consider bytes 1-3 of the
    // IPv6 header as don't care.
    public static final int IPV6_FLOW_LABEL_OFFSET = ETH_HEADER_LEN + 1;
    public static final int IPV6_FLOW_LABEL_LEN = 3;
    public static final int IPV6_NEXT_HEADER_OFFSET = ETH_HEADER_LEN + 6;
    public static final int IPV6_SRC_ADDR_OFFSET = ETH_HEADER_LEN + 8;
    public static final int IPV6_DEST_ADDR_OFFSET = ETH_HEADER_LEN + 24;
    public static final int IPV6_HEADER_LEN = 40;
    // The IPv6 all nodes address ff02::1
    public static final byte[] IPV6_ALL_NODES_ADDRESS =
            { (byte) 0xff, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 };

    public static final int ICMP6_TYPE_OFFSET = ETH_HEADER_LEN + IPV6_HEADER_LEN;

    public static final int IPPROTO_HOPOPTS = 0;

    // NOTE: this must be added to the IPv4 header length in MemorySlot.IPV4_HEADER_SIZE
    public static final int TCP_UDP_DESTINATION_PORT_OFFSET = ETH_HEADER_LEN + 2;
    public static final int UDP_HEADER_LEN = 8;

    public static final int TCP_HEADER_SIZE_OFFSET = 12;

    public static final int DHCP_SERVER_PORT = 67;
    public static final int DHCP_CLIENT_PORT = 68;

    public static final int ARP_HEADER_OFFSET = ETH_HEADER_LEN;
    public static final byte[] ARP_IPV4_HEADER = {
            0, 1, // Hardware type: Ethernet (1)
            8, 0, // Protocol type: IP (0x0800)
            6,    // Hardware size: 6
            4,    // Protocol size: 4
    };
    public static final int ARP_OPCODE_OFFSET = ARP_HEADER_OFFSET + 6;
    // Opcode: ARP request (0x0001), ARP reply (0x0002)
    public static final short ARP_OPCODE_REQUEST = 1;
    public static final short ARP_OPCODE_REPLY = 2;
    public static final int ARP_SOURCE_IP_ADDRESS_OFFSET = ARP_HEADER_OFFSET + 14;
    public static final int ARP_TARGET_IP_ADDRESS_OFFSET = ARP_HEADER_OFFSET + 24;
    // Limit on the Black List size to cap on program usage for this
    // TODO: Select a proper max length
    public static final int APF_MAX_ETH_TYPE_BLACK_LIST_LEN = 20;

    public static final byte[] ETH_MULTICAST_MDNS_V4_MAC_ADDRESS =
            {(byte) 0x01, (byte) 0x00, (byte) 0x5e, (byte) 0x00, (byte) 0x00, (byte) 0xfb};
    public static final byte[] ETH_MULTICAST_MDNS_V6_MAC_ADDRESS =
            {(byte) 0x33, (byte) 0x33, (byte) 0x00, (byte) 0x00, (byte) 0x00, (byte) 0xfb};
    public static final int MDNS_PORT = 5353;

    public static final int ECHO_PORT = 7;
    public static final int DNS_HEADER_LEN = 12;
    public static final int DNS_QDCOUNT_OFFSET = 4;
    // NOTE: this must be added to the IPv4 header length in MemorySlot.IPV4_HEADER_SIZE, or the
    // IPv6 header length.
    public static final int DHCP_CLIENT_MAC_OFFSET = ETH_HEADER_LEN + UDP_HEADER_LEN + 28;
    public static final int MDNS_QDCOUNT_OFFSET =
            ETH_HEADER_LEN + UDP_HEADER_LEN + DNS_QDCOUNT_OFFSET;
    public static final int MDNS_QNAME_OFFSET =
            ETH_HEADER_LEN + UDP_HEADER_LEN + DNS_HEADER_LEN;

    /**
     * Fixed byte sequence representing the following part of the ARP reply header:
     * EtherType + HTYPE + PTYPE + HLEN + PLEN + ops reply (0x0002)
     */
    public static final byte[] FIXED_ARP_REPLY_HEADER =
            new byte[]{0x08, 0x06, 0x00, 0x01, 0x08, 0x00, 0x06, 0x04, 0x00, 0x02};
}