LineageOS/android_packages_modules_Connectivity
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Add helper method to generate a v6 NAT-T keepalive packet

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This is a part of preliminary work for sending a v6 NAT-T
keepalive packet in a v6 only network. This commit
release the constraint on constructing a v6 NAT-T keepalive
packet.

Bug: 196453719
Test: Manually connect to v6 only network and check if the
      keepalive packets are sent with subsequent commit
Test: atest FrameworksNetTests with the updated test
Change-Id: I9dc96e840265c5dee6b9e3ef2b3901a0aeb4ff9e
This commit is contained in:
chiachangwang
2023-06-09 06:09:44 +00:00
parent 60179ec28e
commit c18f0bbbb3
3 changed files with 69 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

51
framework/src/android/net/NattKeepalivePacketData.java
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@@ -29,7 +29,9 @@ import android.system.OsConstants;
import com.android.net.module.util.IpUtils;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.util.Objects;
@@ -38,6 +40,7 @@ import java.util.Objects;
@SystemApi
public final class NattKeepalivePacketData extends KeepalivePacketData implements Parcelable {
private static final int IPV4_HEADER_LENGTH = 20;
private static final int IPV6_HEADER_LENGTH = 40;
private static final int UDP_HEADER_LENGTH = 8;
// This should only be constructed via static factory methods, such as
@@ -59,13 +62,25 @@ public final class NattKeepalivePacketData extends KeepalivePacketData implement
throw new InvalidPacketException(ERROR_INVALID_PORT);
}
if (!(srcAddress instanceof Inet4Address) || !(dstAddress instanceof Inet4Address)) {
// Convert IPv4 mapped v6 address to v4 if any.
final InetAddress srcAddr, dstAddr;
try {
srcAddr = InetAddress.getByAddress(srcAddress.getAddress());
dstAddr = InetAddress.getByAddress(dstAddress.getAddress());
} catch (UnknownHostException e) {
throw new InvalidPacketException(ERROR_INVALID_IP_ADDRESS);
}
return nattKeepalivePacketv4(
(Inet4Address) srcAddress, srcPort,
(Inet4Address) dstAddress, dstPort);
if (srcAddr instanceof Inet4Address && dstAddr instanceof Inet4Address) {
return nattKeepalivePacketv4(
(Inet4Address) srcAddr, srcPort, (Inet4Address) dstAddr, dstPort);
} else if (srcAddr instanceof Inet6Address && dstAddress instanceof Inet6Address) {
return nattKeepalivePacketv6(
(Inet6Address) srcAddr, srcPort, (Inet6Address) dstAddr, dstPort);
} else {
// Destination address and source address should be the same IP family.
throw new InvalidPacketException(ERROR_INVALID_IP_ADDRESS);
}
}
private static NattKeepalivePacketData nattKeepalivePacketv4(
@@ -82,14 +97,14 @@ public final class NattKeepalivePacketData extends KeepalivePacketData implement
// /proc/sys/net/ipv4/ip_default_ttl. Use hard-coded 64 for simplicity.
buf.put((byte) 64); // TTL
buf.put((byte) OsConstants.IPPROTO_UDP);
int ipChecksumOffset = buf.position();
final int ipChecksumOffset = buf.position();
buf.putShort((short) 0); // IP checksum
buf.put(srcAddress.getAddress());
buf.put(dstAddress.getAddress());
buf.putShort((short) srcPort);
buf.putShort((short) dstPort);
buf.putShort((short) (UDP_HEADER_LENGTH + 1)); // UDP length
int udpChecksumOffset = buf.position();
final int udpChecksumOffset = buf.position();
buf.putShort((short) 0); // UDP checksum
buf.put((byte) 0xff); // NAT-T keepalive
buf.putShort(ipChecksumOffset, IpUtils.ipChecksum(buf, 0));
@@ -98,6 +113,30 @@ public final class NattKeepalivePacketData extends KeepalivePacketData implement
return new NattKeepalivePacketData(srcAddress, srcPort, dstAddress, dstPort, buf.array());
}
private static NattKeepalivePacketData nattKeepalivePacketv6(
Inet6Address srcAddress, int srcPort, Inet6Address dstAddress, int dstPort)
throws InvalidPacketException {
final ByteBuffer buf = ByteBuffer.allocate(IPV6_HEADER_LENGTH + UDP_HEADER_LENGTH + 1);
buf.order(ByteOrder.BIG_ENDIAN);
buf.putInt(0x60000000); // IP version, traffic class and flow label
buf.putShort((short) (UDP_HEADER_LENGTH + 1)); // Payload length
buf.put((byte) OsConstants.IPPROTO_UDP); // Next header
// For native ipv6, this hop limit value should use the per interface v6 hoplimit sysctl.
// For 464xlat, this value should use the v4 ttl sysctl.
// Either way, for simplicity, just hard code 64.
buf.put((byte) 64); // Hop limit
buf.put(srcAddress.getAddress());
buf.put(dstAddress.getAddress());
// UDP
buf.putShort((short) srcPort);
buf.putShort((short) dstPort);
buf.putShort((short) (UDP_HEADER_LENGTH + 1)); // UDP length = Payload length
final int udpChecksumOffset = buf.position();
buf.putShort((short) 0); // UDP checksum
buf.put((byte) 0xff); // NAT-T keepalive. 1 byte of data
buf.putShort(udpChecksumOffset, IpUtils.udpChecksum(buf, 0, IPV6_HEADER_LENGTH));
return new NattKeepalivePacketData(srcAddress, srcPort, dstAddress, dstPort, buf.array());
}
/** Parcelable Implementation */
public int describeContents() {
return 0;