netdev - RE: [PATCH net-next 1/4] vlan: Add MACsec offload operations for VLAN interface

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Date:   Wed, 29 Mar 2023 11:07:53 +0000
From:   Emeel Hakim <ehakim@...dia.com>
To:     Francois Romieu <romieu@...zoreil.com>
CC:     Jakub Kicinski <kuba@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "sd@...asysnail.net" <sd@...asysnail.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH net-next 1/4] vlan: Add MACsec offload operations for VLAN
 interface



> -----Original Message-----
> From: Francois Romieu <romieu@...zoreil.com>
> Sent: Tuesday, 28 March 2023 21:21
> To: Emeel Hakim <ehakim@...dia.com>
> Cc: Jakub Kicinski <kuba@...nel.org>; davem@...emloft.net; pabeni@...hat.com;
> edumazet@...gle.com; sd@...asysnail.net; netdev@...r.kernel.org
> Subject: Re: [PATCH net-next 1/4] vlan: Add MACsec offload operations for VLAN
> interface
> 
> External email: Use caution opening links or attachments
> 
> 
> Emeel Hakim <ehakim@...dia.com> :
> > > -----Original Message-----
> > > From: Jakub Kicinski <kuba@...nel.org>
> [...]
> > > > +#if IS_ENABLED(CONFIG_MACSEC)
> > > > +#define VLAN_MACSEC_MDO(mdo) \
> > > > +static int vlan_macsec_ ## mdo(struct macsec_context *ctx) \ { \
> > > > +     const struct macsec_ops *ops; \
> > > > +     ops =  vlan_dev_priv(ctx->netdev)->real_dev->macsec_ops; \
> > > > +     return ops ? ops->mdo_ ## mdo(ctx) : -EOPNOTSUPP; \ }
> > > > +
> > > > +#define VLAN_MACSEC_DECLARE_MDO(mdo) vlan_macsec_ ## mdo
> > > > +
> > > > +VLAN_MACSEC_MDO(add_txsa);
> > > > +VLAN_MACSEC_MDO(upd_txsa);
> > > > +VLAN_MACSEC_MDO(del_txsa);
> > > > +
> > > > +VLAN_MACSEC_MDO(add_rxsa);
> > > > +VLAN_MACSEC_MDO(upd_rxsa);
> > > > +VLAN_MACSEC_MDO(del_rxsa);
> > > > +
> > > > +VLAN_MACSEC_MDO(add_rxsc);
> > > > +VLAN_MACSEC_MDO(upd_rxsc);
> > > > +VLAN_MACSEC_MDO(del_rxsc);
> > > > +
> > > > +VLAN_MACSEC_MDO(add_secy);
> > > > +VLAN_MACSEC_MDO(upd_secy);
> > > > +VLAN_MACSEC_MDO(del_secy);
> > >
> > > -1
> > >
> > > impossible to grep for the functions :( but maybe others don't care
> >
> > Thank you for bringing up the issue you noticed. However, I decided to
> > go with this approach because the functions are simple and look very similar, so
> there wasn't much to debug.
> > Using a macro allowed for cleaner code instead of having to resort to ugly code
> duplication.
> 
> Sometime it's also nice to be able to use such modern tools as tags and grep.
> 
> While it still implies some duplication and it doesn't automagically prevent wrongly
> mixing vlan_macsec_foo() and ops->mdo_bar(), the code below may be considered
> as a trade-off:
> 
> #define _B(mdo) \
>         const struct macsec_ops *ops; \
>         ops = vlan_dev_priv(ctx->netdev)->real_dev->macsec_ops; \
>         return ops ? ops->mdo_ ## mdo(ctx) : -EOPNOTSUPP; \
> 
> 
> static int vlan_macsec_add_txsa(struct macsec_context *ctx) { _B(add_txsa) } static
> int vlan_macsec_upd_txsa(struct macsec_context *ctx) { _B(upd_txsa) } [...] #undef
> _B

I think that’s a reasonable compromise, I can do that and resend.

> On a tangent topic, both codes expand 12 times the accessor
> 
> vlan_dev_priv(ctx->netdev)->real_dev->macsec_ops.
> 
> It imvho deserves an helper function so that the compiler can make some choice.

Agreed.

> As a final remark, VLAN_MACSEC_DECLARE_MDO above does not buy much.
> Compare:
> 
> static const struct macsec_ops macsec_offload_ops = {
>         .mdo_add_txsa = VLAN_MACSEC_DECLARE_MDO(add_txsa),
>         .mdo_upd_txsa = VLAN_MACSEC_DECLARE_MDO(upd_txsa),
> [...]
> 
> vs
> 
> static const struct macsec_ops macsec_offload_ops = {
>         .mdo_add_txsa = vlan_macsec_add_txsa,
>         .mdo_upd_txsa = vlan_macsec_upd_txsa, [...]
> 
> This one could probably be:
> 
> #define _I(mdo) .mdo_ ## mdo = vlan_macsec_ ## mdo
> 
> static const struct macsec_ops macsec_offload_ops = {
>         _I(add_txsa),
>         _I(upd_txsa),
> [...]
> #undef _I

I agree I will do that.

> --
> Ueimor