LineageOS/android_packages_modules_Connectivity
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Set DF flag on NAT-T keepalive packet

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- Set the DF flag on the NAT-T keepalive packet
- Add comment for TTL value
- Do some cleanups

Bug: 196453719
Test: m
Change-Id: I401ae52d8f16e43120210cdea223fd251d53ea3b
This commit is contained in:
chiachangwang
2023-06-06 06:51:35 +00:00
committed by Chiachang Wang
parent df347448a1
commit c6a2f6faf5
1 changed files with 11 additions and 8 deletions
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19
framework/src/android/net/NattKeepalivePacketData.java
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@@ -72,23 +72,26 @@ public final class NattKeepalivePacketData extends KeepalivePacketData implement
Inet4Address srcAddress, int srcPort, Inet4Address dstAddress, int dstPort)
throws InvalidPacketException {
int length = IPV4_HEADER_LENGTH + UDP_HEADER_LENGTH + 1;
ByteBuffer buf = ByteBuffer.allocate(length);
final ByteBuffer buf = ByteBuffer.allocate(length);
buf.order(ByteOrder.BIG_ENDIAN);
buf.putShort((short) 0x4500); // IP version and TOS
buf.putShort((short) 0x4500); // IP version and TOS
buf.putShort((short) length);
buf.putInt(0); // ID, flags, offset
buf.put((byte) 64); // TTL
buf.putShort((short) 0); // ID
buf.putShort((short) 0x4000); // Flags(DF), offset
// Technically speaking, this should be reading/using the v4 sysctl
// /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();
buf.putShort((short) 0); // IP checksum
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) (length - 20)); // UDP length
buf.putShort((short) (UDP_HEADER_LENGTH + 1)); // UDP length
int udpChecksumOffset = buf.position();
buf.putShort((short) 0); // UDP checksum
buf.put((byte) 0xff); // NAT-T keepalive
buf.putShort((short) 0); // UDP checksum
buf.put((byte) 0xff); // NAT-T keepalive
buf.putShort(ipChecksumOffset, IpUtils.ipChecksum(buf, 0));
buf.putShort(udpChecksumOffset, IpUtils.udpChecksum(buf, 0, IPV4_HEADER_LENGTH));