Add helper method to generate a v6 NAT-T keepalive packet
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
diff --git a/framework/src/android/net/NattKeepalivePacketData.java b/framework/src/android/net/NattKeepalivePacketData.java
index a18e713..a524859 100644
--- a/framework/src/android/net/NattKeepalivePacketData.java
+++ b/framework/src/android/net/NattKeepalivePacketData.java
@@ -29,7 +29,9 @@
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 @@
@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 @@
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 @@
// /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 @@
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;