Add support for IPSec ESN and pass relevant information to crypto layer

[jaz_semihalf.com]

Summary

Implement support for including IPSec ESN (Extended Sequence Number) to
both encrypt and authenticate mode (eg. AES-CBC and SHA256) and combined
mode (eg. AES-GCM). Both ESP and AH protocols are updated. Additionally
pass relevant information about ESN to crypto layer.

For the ETA mode the ESN is stored in separate crp_esn buffer because
the high-order 32 bits of the sequence number are appended after the
Next Header (RFC 4303).

For the AEAD modes the high-order 32 bits of the sequence number
[e.g. RFC 4106, Chapter 5 AAD Construction] are included as part of
crp_aad (SPI + ESN (32 high order bits) + Seq nr (32 low order bits)).

[jaz_semihalf.com]

Align to new OCF

[jhb]

Overall looks fine to me. I can't recall if I had suggested an explicit crp_flag to know when crp_esn was valid (rather than assuming that all operations in an ESN session have it, but perhaps it's ok to use the session flag. With some other flags like SEPARATE_AAD or separate output buffers clients want the option on a per-request basis, but with ESN the client (IPsec) will always be setting it.

sys/netipsec/xform_esp.c

359

Moving this is fine but looks like a no-op?

626

Alternatively, you could move the free(crp->crp_aad, M_XDATA) under the existing if (crp != NULL) below since free(NULL, ..) is defined to be a nop.

933

As below, you can just call free() unconditionally. There is also no need to clear crp_aad.

966

This can just be unconditional like the rest of this block since free(NULL) is ok.

[jhb]

FYI, I've tried to set parent/child relationships for all the ESN-related reviews (you can see the graph in the "Stack" tab).

[jaz_semihalf.com]

Address @jhb comments mostly regarding to freeing crp->crp_aad.

[jaz_semihalf.com]

By mistake previous diff was updated without full context- fix this by uploading diff with full context.

[jaz_semihalf.com]

sys/netipsec/xform_esp.c

359

This was leftover from previous approach - I've undo this change. Thank you.

[gnn]

This patch contains many magic numbers 4, 8 and 32 that should either be removed by the proper use of sizeof() or turned into #defines that are named.

sys/netipsec/xform_ah.c

671

Please change the magic number (4) to either a #define or sizeof(seqh)

1057

Same as previous memcpy

sys/netipsec/xform_esp.c

218

Push else up to } else and please check indenting in this section.

369

Add braces to make this clearer as to which operation goes where.

371

Convert magic number (4) to a #define or const.

753

#dedfine for magic number

[jaz_semihalf.com]

Address @gnn comments: get rid of various magic numbers and improve formatting.

[jhb]

sys/netipsec/xform_esp.c

380

Minor nit: blank line before here.

882

Here as well.

[gnn]

LGTM, thanks!

[jaz_semihalf.com]

@jhb and @gnn thank you for all your review