Package io.github.mahmoudimus.quic.connection

Class PacketNumberFilter

java.lang.Object

io.github.mahmoudimus.quic.connection.PacketNumberFilter

public final class PacketNumberFilter
extends Object

Mitigates optimistic ACK attacks (RFC 9000 section 21.4) by occasionally skipping a packet number in the application data space: an ACK of a skipped number proves the peer acknowledges packets it never received. Skips get exponentially rarer, since a peer that behaved for long is less likely to start misbehaving.

Threads. Not thread-safe; owned by one connection.

Constructor Summary

Constructors

Constructor	Description
PacketNumberFilter(RandomGenerator random)	A filter whose first skip is somewhere in packet numbers 0 to 63.

Method Summary

Modifier and Type	Method	Description
long	allocate(RandomGenerator random, PacketSpace space)	Allocates the next packet number, skipping it if it is the chosen one.
void	checkAck(SpaceId space, long smallest, long largest)	Rejects an ACK of the skipped packet number.
static PacketNumberFilter	disabled()	A filter that never skips, for tests.
long	peek(PacketSpace space)	The packet number allocate(java.util.random.RandomGenerator, io.github.mahmoudimus.quic.connection.PacketSpace) would return next.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

PacketNumberFilter

public PacketNumberFilter(RandomGenerator random)

A filter whose first skip is somewhere in packet numbers 0 to 63.

Parameters:

random - the source of randomness

Method Details

disabled

public static PacketNumberFilter disabled()

A filter that never skips, for tests.

Returns:

the filter

peek

public long peek(PacketSpace space)

The packet number allocate(java.util.random.RandomGenerator, io.github.mahmoudimus.quic.connection.PacketSpace) would return next.

Parameters:

space - the application data space

Returns:

the packet number

allocate

public long allocate(RandomGenerator random,
 PacketSpace space)

Allocates the next packet number, skipping it if it is the chosen one.

Parameters:

random - the source of randomness

space - the application data space

Returns:

the packet number to send

checkAck

public void checkAck(SpaceId space,
 long smallest,
 long largest)
              throws QuicException

Rejects an ACK of the skipped packet number.

Parameters:

space - the space the ACK arrived in

smallest - the smallest packet number of an acknowledged range

largest - the largest packet number of the range

Throws:

QuicException - PROTOCOL_VIOLATION if the range covers a skipped packet number