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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Sabrina Dubroca , Jiri Pirko , Ido Schimmel , Shuah Khan , Stanislav Fomichev , Stanislav Fomichev , Kuniyuki Iwashima , Alexander Lobakin , bridge@lists.linux.dev, linux-kselftest@vger.kernel.org Subject: Re: [PATCHv4 net-next 1/4] net: add a common function to compute features from lowers devices Message-ID: References: <20251014080217.47988-1-liuhangbin@gmail.com> <20251014080217.47988-2-liuhangbin@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hi Simon, Thanks for the comments, I will fix all of them. Regards Hangbin On Tue, Oct 14, 2025 at 03:02:23PM +0100, Simon Horman wrote: > On Tue, Oct 14, 2025 at 08:02:14AM +0000, Hangbin Liu wrote: > > ... > > > diff --git a/net/core/dev.c b/net/core/dev.c > > index a64cef2c537e..54f0e792fbd2 100644 > > --- a/net/core/dev.c > > +++ b/net/core/dev.c > > @@ -12616,6 +12616,101 @@ netdev_features_t netdev_increment_features(netdev_features_t all, > > } > > EXPORT_SYMBOL(netdev_increment_features); > > > > +/** > > + * netdev_compute_features_from_lowers - compute feature from lowers > > + * @dev: the upper device > > + * @update_header: whether to update upper device's header_len/headroom/tailroom > > + * > > + * Recompute the upper device's feature based on all lower devices. > > + */ > > +void netdev_compute_features_from_lowers(struct net_device *dev, bool update_header) > > +{ > > + unsigned int dst_release_flag = IFF_XMIT_DST_RELEASE | IFF_XMIT_DST_RELEASE_PERM; > > + netdev_features_t gso_partial_features = VIRTUAL_DEV_GSO_PARTIAL_FEATURES; > > +#ifdef CONFIG_XFRM_OFFLOAD > > + netdev_features_t xfrm_features = VIRTUAL_DEV_XFRM_FEATURES; > > +#endif > > Hi Hangbin, > > It would be nice to avoid the #ifdefs in this function. > > Could xfrm_features be declared unconditoinally. > And then used behind if(IS_ENABLED(CONFIG_XFRM_OFFLOAD)) conditions? > This would increase compile coverage (and readability IMHO). > > > + netdev_features_t mpls_features = VIRTUAL_DEV_MPLS_FEATURES; > > + netdev_features_t vlan_features = VIRTUAL_DEV_VLAN_FEATURES; > > + netdev_features_t enc_features = VIRTUAL_DEV_ENC_FEATURES; > > + unsigned short max_header_len = ETH_HLEN; > > + unsigned int tso_max_size = TSO_MAX_SIZE; > > + u16 tso_max_segs = TSO_MAX_SEGS; > > + struct net_device *lower_dev; > > + unsigned short max_headroom; > > + unsigned short max_tailroom; > > + struct list_head *iter; > > + > > + mpls_features = netdev_base_features(mpls_features); > > + vlan_features = netdev_base_features(vlan_features); > > + enc_features = netdev_base_features(enc_features); > > + > > + netdev_for_each_lower_dev(dev, lower_dev, iter) { > > + gso_partial_features = netdev_increment_features(gso_partial_features, > > + lower_dev->gso_partial_features, > > + VIRTUAL_DEV_GSO_PARTIAL_FEATURES); > > + > > + vlan_features = netdev_increment_features(vlan_features, > > + lower_dev->vlan_features, > > + VIRTUAL_DEV_VLAN_FEATURES); > > + > > + enc_features = netdev_increment_features(enc_features, > > + lower_dev->hw_enc_features, > > + VIRTUAL_DEV_ENC_FEATURES); > > + > > +#ifdef CONFIG_XFRM_OFFLOAD > > + xfrm_features = netdev_increment_features(xfrm_features, > > + lower_dev->hw_enc_features, > > + VIRTUAL_DEV_XFRM_FEATURES); > > +#endif > > + > > + mpls_features = netdev_increment_features(mpls_features, > > + lower_dev->mpls_features, > > + VIRTUAL_DEV_MPLS_FEATURES); > > + > > + dst_release_flag &= lower_dev->priv_flags; > > + > > + if (update_header) { > > + max_header_len = max_t(unsigned short, max_header_len, > > + lower_dev->hard_header_len); > > Both the type of max_header_len and .hard_header_len is unsigned short. > So I think max() can be used here instead of max_t(). Likewise for the > following two lines. > > > + max_headroom = max_t(unsigned short, max_headroom, > > + lower_dev->needed_headroom); > > Max Headroom [1] is used uninitialised the first time we reach here. > Likewise for max_tailroom below. > > [1] https://en.wikipedia.org/wiki/Max_Headroom > > Flagged by Smatch. > > > + max_tailroom = max_t(unsigned short, max_tailroom, > > + lower_dev->needed_tailroom); > > + } > > + > > + tso_max_size = min(tso_max_size, lower_dev->tso_max_size); > > + tso_max_segs = min(tso_max_segs, lower_dev->tso_max_segs); > > + } > > + > > + dev->gso_partial_features = gso_partial_features; > > + dev->vlan_features = vlan_features; > > + dev->hw_enc_features = enc_features | NETIF_F_GSO_ENCAP_ALL | > > + NETIF_F_HW_VLAN_CTAG_TX | > > + NETIF_F_HW_VLAN_STAG_TX; > > +#ifdef CONFIG_XFRM_OFFLOAD > > + dev->hw_enc_features |= xfrm_features; > > +#endif > > + dev->mpls_features = mpls_features; > > + > > + dev->priv_flags &= ~IFF_XMIT_DST_RELEASE; > > + if ((dev->priv_flags & IFF_XMIT_DST_RELEASE_PERM) && > > + dst_release_flag == (IFF_XMIT_DST_RELEASE | IFF_XMIT_DST_RELEASE_PERM)) > > + dev->priv_flags |= IFF_XMIT_DST_RELEASE; > > + > > + if (update_header) { > > + dev->hard_header_len = max_header_len; > > + dev->needed_headroom = max_headroom; > > + dev->needed_tailroom = max_tailroom; > > Also, maybe it can't happen in practice. But I think that max_headroom and > max_tailroom will may be used uninitialised here if the previous > 'update_header' condition is never reached/met. > > Also flagged by Smatch. > > > + } > > + > > + netif_set_tso_max_segs(dev, tso_max_segs); > > + netif_set_tso_max_size(dev, tso_max_size); > > + > > + netdev_change_features(dev); > > +} > > +EXPORT_SYMBOL(netdev_compute_features_from_lowers); > > + > > ...