[PATCH 2/2] XFRM: Drop packets when replay counter would overflow

[David Miller]

From: Paul Moore <paul.moore at hp.com>
Date: Fri, 21 Dec 2007 09:15:00 -0500

> According to RFC4303, section 3.3.3 we need to drop outgoing packets which
> cause the replay counter to overflow:
> 
>    3.3.3.  Sequence Number Generation
> 
>    The sender's counter is initialized to 0 when an SA is established.
>    The sender increments the sequence number (or ESN) counter for this
>    SA and inserts the low-order 32 bits of the value into the Sequence
>    Number field.  Thus, the first packet sent using a given SA will
>    contain a sequence number of 1.
> 
>    If anti-replay is enabled (the default), the sender checks to ensure
>    that the counter has not cycled before inserting the new value in the
>    Sequence Number field.  In other words, the sender MUST NOT send a
>    packet on an SA if doing so would cause the sequence number to cycle.
>    An attempt to transmit a packet that would result in sequence number
>    overflow is an auditable event.  The audit log entry for this event
>    SHOULD include the SPI value, current date/time, Source Address,
>    Destination Address, and (in IPv6) the cleartext Flow ID.
> 
> Signed-off-by: Paul Moore <paul.moore at hp.com>

Applied.