On Tue, Oct 14, 2025 at 08:02:14AM +0000, Hangbin Liu wrote:
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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);
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