[strongSwan] ESN support for IKEv1

[Martin Willi]

Hi,

>  The wiki mentions this ESN support is only for IKEv2. Is it so?

Yes.

> As per my understanding this ESN feature refers to sequence
> numbers in ESP. So why is this support dependent on version of IKE?

ESN support must be negotiated, as defined in RFC 4304, 2.2.1:

>    To support high-speed IPsec implementations, Extended Sequence
>    Numbers (ESNs) SHOULD be implemented, as an extension to the current,
>    32-bit sequence number field.  Use of an ESN MUST be negotiated by an
>    SA management protocol.  Note that in IKEv2, this negotiation is
>    implicit; the default is ESN unless 32-bit sequence numbers are
>    explicitly negotiated.

ESN negotiation for IKEv1 is defined in RFC 4304, but we currently do
not support this extension in strongSwan.

Regards
Martin