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Message-ID: <167335890996.17820.293620523946399247@kwain.local> Date: Tue, 10 Jan 2023 14:55:09 +0100 From: Antoine Tenart <atenart@...nel.org> To: Sabrina Dubroca <sd@...asysnail.net> Cc: ehakim@...dia.com, netdev@...r.kernel.org, raeds@...dia.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com Subject: Re: [PATCH net-next v7 1/2] macsec: add support for IFLA_MACSEC_OFFLOAD in macsec_changelink Quoting Sabrina Dubroca (2023-01-10 11:44:13) > 2023-01-10, 09:43:37 +0100, Antoine Tenart wrote: > > Quoting Sabrina Dubroca (2023-01-09 16:14:32) > > > 2023-01-09, 10:55:56 +0200, ehakim@...dia.com wrote: > > > > @@ -3840,6 +3835,12 @@ static int macsec_changelink(struct net_device *dev, struct nlattr *tb[], > > > > if (ret) > > > > goto cleanup; > > > > > > > > + if (data[IFLA_MACSEC_OFFLOAD]) { > > > > + ret = macsec_update_offload(dev, nla_get_u8(data[IFLA_MACSEC_OFFLOAD])); > > > > + if (ret) > > > > + goto cleanup; > > > > + } > > > > + > > > > /* If h/w offloading is available, propagate to the device */ > > > > if (macsec_is_offloaded(macsec)) { > > > > const struct macsec_ops *ops; > > > > > > There's a missing rollback of the offloading status in the (probably > > > quite unlikely) case that mdo_upd_secy fails, no? We can't fail > > > macsec_get_ops because macsec_update_offload would have failed > > > already, but I guess the driver could fail in mdo_upd_secy, and then > > > "goto cleanup" doesn't restore the offloading state. Sorry I didn't > > > notice this earlier. > > > > > > In case the IFLA_MACSEC_OFFLOAD attribute is provided and we're > > > enabling offload, we also end up calling the driver's mdo_add_secy, > > > and then immediately afterwards mdo_upd_secy, which probably doesn't > > > make much sense. > > > > > > Maybe we could turn that into: > > > > > > if (data[IFLA_MACSEC_OFFLOAD]) { > > > > If data[IFLA_MACSEC_OFFLOAD] is provided but doesn't change the > > offloading state, then macsec_update_offload will return early and > > mdo_upd_secy won't be called. > > Ouch, thanks for catching this. > > > > > > ... macsec_update_offload > > > } else if (macsec_is_offloaded(macsec)) { > > > /* If h/w offloading is available, propagate to the device */ > > > ... mdo_upd_secy > > > } > > > > > > Antoine, does that look reasonable to you? > > > > But yes I agree we can improve the logic. Maybe something like: > > > > prev_offload = macsec->offload; > > offload = data[IFLA_MACSEC_OFFLOAD]; > > That needs to be under if (data[IFLA_MACSEC_OFFLOAD]) and then the > rest gets a bit messy. > > > > > if (prev_offload != offload) { > > macsec_update_offload(...) > > } else if (macsec_is_offloaded(macsec)) { > > ... > > prev_offload can be used to restore the offloading state on > > failure here. > > } > > We also have a prev != new test at the start of macsec_update_offload, > the duplication is a bit ugly. We could move it out and then only call > macsec_update_offload when there is a change to do, both from > macsec_changelink and macsec_upd_offload. Agreed. > Since we don't need to restore in the second branch, and we can only > fetch IFLA_MACSEC_OFFLOAD when it's present, maybe: > > change = false; > if (data[IFLA_MACSEC_OFFLOAD]) { > offload = nla_get_u8(data[IFLA_MACSEC_OFFLOAD]); > if (macsec->offload != offload) { > change = true; > macsec_update_offload ...cleanup > } > } > > if (!change && macsec_is_offloaded(macsec)) { > ... > } > > Or let macsec_update_offload do the macsec->offload != offload test > and pass &change so that changelink can know what to do next. Either solutions work for me. Thanks! Antoine
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