Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 5 Mar 2020 18:24:53 +0100
From:   Michal Kubecek <mkubecek@suse.cz>
To:     Era Mayflower <mayflowerera@gmail.com>
Cc:     netdev@vger.kernel.org, davem@davemloft.net,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] macsec: Netlink support of XPN cipher suites (IEEE
 802.1AEbw)
Message-ID: <20200305172453.GB28693@unicorn.suse.cz>
References: <20200305220108.18780-1-mayflowerera@gmail.com>
 <20200305220108.18780-2-mayflowerera@gmail.com>
 <20200305140241.GA28693@unicorn.suse.cz>
 <CAMdQvKv9tSoSBfyOyhtctQ9D7aU2WUmuMUsoLn_WZ8whD=3AzA@mail.gmail.com>
 <CAMdQvKuzaBuKGj1-HR6+r=FY4X9GhZPvEHwRt3BjErFiu1+bgw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAMdQvKuzaBuKGj1-HR6+r=FY4X9GhZPvEHwRt3BjErFiu1+bgw@mail.gmail.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Mar 05, 2020 at 11:53:29PM +0000, Era Mayflower wrote:
> Do you think that inserting those new enum values after *_PAD would be
> a good solution?

Yes, new attribute identifiers should always be added as last so that
you don't change existing values.

Michal

> On Thu, Mar 5, 2020 at 11:51 PM Era Mayflower <mayflowerera@gmail.com> wrote:
> >
> > Do you think that inserting those new enum values after *_PAD would be a good solution?
> >
> > On Thu, Mar 5, 2020 at 2:02 PM Michal Kubecek <mkubecek@suse.cz> wrote:
> >>
> >> On Thu, Mar 05, 2020 at 10:01:08PM +0000, Era Mayflower wrote:
> >> > Netlink support of extended packet number cipher suites,
> >> > allows adding and updating XPN macsec interfaces.
> >> >
> >> > Added support in:
> >> >     * Creating interfaces with GCM-AES-XPN-128 and GCM-AES-XPN-256.
> >> >     * Setting and getting packet numbers with 64bit of SAs.
> >> >     * Settings and getting ssci of SCs.
> >> >     * Settings and getting salt of SecYs.
> >> >
> >> > Depends on: macsec: Support XPN frame handling - IEEE 802.1AEbw.
> >> >
> >> > Signed-off-by: Era Mayflower <mayflowerera@gmail.com>
> >> > ---
> >> [...]
> >> > diff --git a/include/net/macsec.h b/include/net/macsec.h
> >> > index a0b1d0b5c..3c7914ff1 100644
> >> > --- a/include/net/macsec.h
> >> > +++ b/include/net/macsec.h
> >> > @@ -11,6 +11,9 @@
> >> >  #include <uapi/linux/if_link.h>
> >> >  #include <uapi/linux/if_macsec.h>
> >> >
> >> > +#define MACSEC_DEFAULT_PN_LEN 4
> >> > +#define MACSEC_XPN_PN_LEN 8
> >> > +
> >> >  #define MACSEC_SALT_LEN 12
> >> >
> >> >  typedef u64 __bitwise sci_t;
> >> > diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> >> > index 024af2d1d..ee424d915 100644
> >> > --- a/include/uapi/linux/if_link.h
> >> > +++ b/include/uapi/linux/if_link.h
> >> > @@ -462,6 +462,8 @@ enum {
> >> >       IFLA_MACSEC_SCB,
> >> >       IFLA_MACSEC_REPLAY_PROTECT,
> >> >       IFLA_MACSEC_VALIDATION,
> >> > +     IFLA_MACSEC_SSCI,
> >> > +     IFLA_MACSEC_SALT,
> >> >       IFLA_MACSEC_PAD,
> >> >       __IFLA_MACSEC_MAX,
> >> >  };
> >>
> >> Doesn't this break backword compatibility? You change the value of
> >> IFLA_MACSEC_PAD; even if it's only used as padding, if an old client
> >> uses it, new kernel will interpret it as IFLA_MACSEC_SSCI (an the same
> >> holds for new client with old kernel).
> >>
> >> > diff --git a/include/uapi/linux/if_macsec.h b/include/uapi/linux/if_macsec.h
> >> > index 1d63c43c3..c8fab9673 100644
> >> > --- a/include/uapi/linux/if_macsec.h
> >> > +++ b/include/uapi/linux/if_macsec.h
> >> > @@ -25,6 +25,8 @@
> >> >  /* cipher IDs as per IEEE802.1AEbn-2011 */
> >> >  #define MACSEC_CIPHER_ID_GCM_AES_128 0x0080C20001000001ULL
> >> >  #define MACSEC_CIPHER_ID_GCM_AES_256 0x0080C20001000002ULL
> >> > +#define MACSEC_CIPHER_ID_GCM_AES_XPN_128 0x0080C20001000003ULL
> >> > +#define MACSEC_CIPHER_ID_GCM_AES_XPN_256 0x0080C20001000004ULL
> >> >
> >> >  /* deprecated cipher ID for GCM-AES-128 */
> >> >  #define MACSEC_DEFAULT_CIPHER_ID     0x0080020001000001ULL
> >> > @@ -66,6 +68,8 @@ enum macsec_secy_attrs {
> >> >       MACSEC_SECY_ATTR_INC_SCI,
> >> >       MACSEC_SECY_ATTR_ES,
> >> >       MACSEC_SECY_ATTR_SCB,
> >> > +     MACSEC_SECY_ATTR_SSCI,
> >> > +     MACSEC_SECY_ATTR_SALT,
> >> >       MACSEC_SECY_ATTR_PAD,
> >> >       __MACSEC_SECY_ATTR_END,
> >> >       NUM_MACSEC_SECY_ATTR = __MACSEC_SECY_ATTR_END,
> >> > @@ -78,6 +82,7 @@ enum macsec_rxsc_attrs {
> >> >       MACSEC_RXSC_ATTR_ACTIVE,  /* config/dump, u8 0..1 */
> >> >       MACSEC_RXSC_ATTR_SA_LIST, /* dump, nested */
> >> >       MACSEC_RXSC_ATTR_STATS,   /* dump, nested, macsec_rxsc_stats_attr */
> >> > +     MACSEC_RXSC_ATTR_SSCI,    /* config/dump, u32 */
> >> >       MACSEC_RXSC_ATTR_PAD,
> >> >       __MACSEC_RXSC_ATTR_END,
> >> >       NUM_MACSEC_RXSC_ATTR = __MACSEC_RXSC_ATTR_END,
> >>
> >> The same problem with these two.
> >>
> >> I'm also a bit unsure about the change of type and length of
> >> MACSEC_SA_ATTR_PN but I would have to get more familiar with the code to
> >> see if it is really a problem.
> >>
> >> Michal