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Date:	Mon, 22 Dec 2014 17:28:29 -0800
From:	Tom Herbert <therbert@...gle.com>
To:	Jesse Gross <jesse@...ira.com>
Cc:	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Joe Stringer <joestringer@...ira.com>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net] net: Generalize ndo_gso_check to ndo_features_check

On Mon, Dec 22, 2014 at 8:03 AM, Jesse Gross <jesse@...ira.com> wrote:
> GSO isn't the only offload feature with restrictions that
> potentially can't be expressed with the current features mechanism.
> Checksum is another although it's a general issue that could in
> theory apply to anything. Even if it may be possible to
> implement these restrictions in other ways, it can result in
> duplicate code or inefficient per-packet behavior.
>
> This generalizes ndo_gso_check so that drivers can remove any
> features that don't make sense for a given packet, similar to
> netif_skb_features(). It also converts existing driver
> restrictions to the new format, completing the work that was
> done to support tunnel protocols since the issues apply to
> checksums as well.
>
It's a nice feature, but I really hope that this is not used for
checksums. We already have a sufficiently general interface for that
and checksum is already computed in drivers to work around HW bugs.

Acked-by:  Tom Herbert <therbert@...gle.com>

> CC: Tom Herbert <therbert@...gle.com>
> CC: Joe Stringer <joestringer@...ira.com>
> CC: Eric Dumazet <edumazet@...gle.com>
> Signed-off-by: Jesse Gross <jesse@...ira.com>
> Fixes: 04ffcb255f22 ("net: Add ndo_gso_check")
> ---
>  drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c |  8 ++++---
>  drivers/net/ethernet/emulex/benet/be_main.c      |  8 ++++---
>  drivers/net/ethernet/mellanox/mlx4/en_netdev.c   | 10 +++++----
>  drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c |  8 ++++---
>  include/linux/netdevice.h                        | 20 +++++++++--------
>  include/net/vxlan.h                              | 28 ++++++++++++++++++++----
>  net/core/dev.c                                   | 28 ++++++++++++++++--------
>  7 files changed, 75 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c
> index 9f5e387..72eef9f 100644
> --- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c
> +++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_main.c
> @@ -12553,9 +12553,11 @@ static int bnx2x_get_phys_port_id(struct net_device *netdev,
>         return 0;
>  }
>
> -static bool bnx2x_gso_check(struct sk_buff *skb, struct net_device *dev)
> +static netdev_features_t bnx2x_features_check(struct sk_buff *skb,
> +                                             struct net_device *dev,
> +                                             netdev_features_t features)
>  {
> -       return vxlan_gso_check(skb);
> +       return vxlan_features_check(skb, features);
>  }
>
>  static const struct net_device_ops bnx2x_netdev_ops = {
> @@ -12589,7 +12591,7 @@ static const struct net_device_ops bnx2x_netdev_ops = {
>  #endif
>         .ndo_get_phys_port_id   = bnx2x_get_phys_port_id,
>         .ndo_set_vf_link_state  = bnx2x_set_vf_link_state,
> -       .ndo_gso_check          = bnx2x_gso_check,
> +       .ndo_features_check     = bnx2x_features_check,
>  };
>
>  static int bnx2x_set_coherency_mask(struct bnx2x *bp)
> diff --git a/drivers/net/ethernet/emulex/benet/be_main.c b/drivers/net/ethernet/emulex/benet/be_main.c
> index 1960731..41a0a54 100644
> --- a/drivers/net/ethernet/emulex/benet/be_main.c
> +++ b/drivers/net/ethernet/emulex/benet/be_main.c
> @@ -4459,9 +4459,11 @@ done:
>         adapter->vxlan_port_count--;
>  }
>
> -static bool be_gso_check(struct sk_buff *skb, struct net_device *dev)
> +static netdev_features_t be_features_check(struct sk_buff *skb,
> +                                          struct net_device *dev,
> +                                          netdev_features_t features)
>  {
> -       return vxlan_gso_check(skb);
> +       return vxlan_features_check(skb, features);
>  }
>  #endif
>
> @@ -4492,7 +4494,7 @@ static const struct net_device_ops be_netdev_ops = {
>  #ifdef CONFIG_BE2NET_VXLAN
>         .ndo_add_vxlan_port     = be_add_vxlan_port,
>         .ndo_del_vxlan_port     = be_del_vxlan_port,
> -       .ndo_gso_check          = be_gso_check,
> +       .ndo_features_check     = be_features_check,
>  #endif
>  };
>
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> index 190cbd9..d0d6dc1 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> @@ -2365,9 +2365,11 @@ static void mlx4_en_del_vxlan_port(struct  net_device *dev,
>         queue_work(priv->mdev->workqueue, &priv->vxlan_del_task);
>  }
>
> -static bool mlx4_en_gso_check(struct sk_buff *skb, struct net_device *dev)
> +static netdev_features_t mlx4_en_features_check(struct sk_buff *skb,
> +                                               struct net_device *dev,
> +                                               netdev_features_t features)
>  {
> -       return vxlan_gso_check(skb);
> +       return vxlan_features_check(skb, features);
>  }
>  #endif
>
> @@ -2400,7 +2402,7 @@ static const struct net_device_ops mlx4_netdev_ops = {
>  #ifdef CONFIG_MLX4_EN_VXLAN
>         .ndo_add_vxlan_port     = mlx4_en_add_vxlan_port,
>         .ndo_del_vxlan_port     = mlx4_en_del_vxlan_port,
> -       .ndo_gso_check          = mlx4_en_gso_check,
> +       .ndo_features_check     = mlx4_en_features_check,
>  #endif
>  };
>
> @@ -2434,7 +2436,7 @@ static const struct net_device_ops mlx4_netdev_ops_master = {
>  #ifdef CONFIG_MLX4_EN_VXLAN
>         .ndo_add_vxlan_port     = mlx4_en_add_vxlan_port,
>         .ndo_del_vxlan_port     = mlx4_en_del_vxlan_port,
> -       .ndo_gso_check          = mlx4_en_gso_check,
> +       .ndo_features_check     = mlx4_en_features_check,
>  #endif
>  };
>
> diff --git a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
> index 1aa25b1..9929b97 100644
> --- a/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
> +++ b/drivers/net/ethernet/qlogic/qlcnic/qlcnic_main.c
> @@ -505,9 +505,11 @@ static void qlcnic_del_vxlan_port(struct net_device *netdev,
>         adapter->flags |= QLCNIC_DEL_VXLAN_PORT;
>  }
>
> -static bool qlcnic_gso_check(struct sk_buff *skb, struct net_device *dev)
> +static netdev_features_t qlcnic_features_check(struct sk_buff *skb,
> +                                              struct net_device *dev,
> +                                              netdev_features_t features)
>  {
> -       return vxlan_gso_check(skb);
> +       return vxlan_features_check(skb, features);
>  }
>  #endif
>
> @@ -532,7 +534,7 @@ static const struct net_device_ops qlcnic_netdev_ops = {
>  #ifdef CONFIG_QLCNIC_VXLAN
>         .ndo_add_vxlan_port     = qlcnic_add_vxlan_port,
>         .ndo_del_vxlan_port     = qlcnic_del_vxlan_port,
> -       .ndo_gso_check          = qlcnic_gso_check,
> +       .ndo_features_check     = qlcnic_features_check,
>  #endif
>  #ifdef CONFIG_NET_POLL_CONTROLLER
>         .ndo_poll_controller = qlcnic_poll_controller,
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index c31f74d..679e6e9 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1012,12 +1012,15 @@ typedef u16 (*select_queue_fallback_t)(struct net_device *dev,
>   *     Callback to use for xmit over the accelerated station. This
>   *     is used in place of ndo_start_xmit on accelerated net
>   *     devices.
> - * bool        (*ndo_gso_check) (struct sk_buff *skb,
> - *                       struct net_device *dev);
> + * netdev_features_t (*ndo_features_check) (struct sk_buff *skb,
> + *                                         struct net_device *dev
> + *                                         netdev_features_t features);
>   *     Called by core transmit path to determine if device is capable of
> - *     performing GSO on a packet. The device returns true if it is
> - *     able to GSO the packet, false otherwise. If the return value is
> - *     false the stack will do software GSO.
> + *     performing offload operations on a given packet. This is to give
> + *     the device an opportunity to implement any restrictions that cannot
> + *     be otherwise expressed by feature flags. The check is called with
> + *     the set of features that the stack has calculated and it returns
> + *     those the driver believes to be appropriate.
>   *
>   * int (*ndo_switch_parent_id_get)(struct net_device *dev,
>   *                                struct netdev_phys_item_id *psid);
> @@ -1178,8 +1181,9 @@ struct net_device_ops {
>                                                         struct net_device *dev,
>                                                         void *priv);
>         int                     (*ndo_get_lock_subclass)(struct net_device *dev);
> -       bool                    (*ndo_gso_check) (struct sk_buff *skb,
> -                                                 struct net_device *dev);
> +       netdev_features_t       (*ndo_features_check) (struct sk_buff *skb,
> +                                                      struct net_device *dev,
> +                                                      netdev_features_t features);
>  #ifdef CONFIG_NET_SWITCHDEV
>         int                     (*ndo_switch_parent_id_get)(struct net_device *dev,
>                                                             struct netdev_phys_item_id *psid);
> @@ -3611,8 +3615,6 @@ static inline bool netif_needs_gso(struct net_device *dev, struct sk_buff *skb,
>                                    netdev_features_t features)
>  {
>         return skb_is_gso(skb) && (!skb_gso_ok(skb, features) ||
> -               (dev->netdev_ops->ndo_gso_check &&
> -                !dev->netdev_ops->ndo_gso_check(skb, dev)) ||
>                 unlikely((skb->ip_summed != CHECKSUM_PARTIAL) &&
>                          (skb->ip_summed != CHECKSUM_UNNECESSARY)));
>  }
> diff --git a/include/net/vxlan.h b/include/net/vxlan.h
> index 57cccd0..903461a 100644
> --- a/include/net/vxlan.h
> +++ b/include/net/vxlan.h
> @@ -1,6 +1,9 @@
>  #ifndef __NET_VXLAN_H
>  #define __NET_VXLAN_H 1
>
> +#include <linux/ip.h>
> +#include <linux/ipv6.h>
> +#include <linux/if_vlan.h>
>  #include <linux/skbuff.h>
>  #include <linux/netdevice.h>
>  #include <linux/udp.h>
> @@ -51,16 +54,33 @@ int vxlan_xmit_skb(struct vxlan_sock *vs,
>                    __be32 src, __be32 dst, __u8 tos, __u8 ttl, __be16 df,
>                    __be16 src_port, __be16 dst_port, __be32 vni, bool xnet);
>
> -static inline bool vxlan_gso_check(struct sk_buff *skb)
> +static inline netdev_features_t vxlan_features_check(struct sk_buff *skb,
> +                                                    netdev_features_t features)
>  {
> -       if ((skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL) &&
> +       u8 l4_hdr = 0;
> +
> +       if (!skb->encapsulation)
> +               return features;
> +
> +       switch (vlan_get_protocol(skb)) {
> +       case htons(ETH_P_IP):
> +               l4_hdr = ip_hdr(skb)->protocol;
> +               break;
> +       case htons(ETH_P_IPV6):
> +               l4_hdr = ipv6_hdr(skb)->nexthdr;
> +               break;
> +       default:
> +               return features;;
> +       }
> +
> +       if ((l4_hdr == IPPROTO_UDP) &&
>             (skb->inner_protocol_type != ENCAP_TYPE_ETHER ||
>              skb->inner_protocol != htons(ETH_P_TEB) ||
>              (skb_inner_mac_header(skb) - skb_transport_header(skb) !=
>               sizeof(struct udphdr) + sizeof(struct vxlanhdr))))
> -               return false;
> +               return features & ~(NETIF_F_ALL_CSUM | NETIF_F_GSO_MASK);
>
> -       return true;
> +       return features;
>  }
>
>  /* IP header + UDP + VXLAN + Ethernet header */
> diff --git a/net/core/dev.c b/net/core/dev.c
> index f411c28..fc13f72 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2562,7 +2562,7 @@ static netdev_features_t harmonize_features(struct sk_buff *skb,
>
>  netdev_features_t netif_skb_features(struct sk_buff *skb)
>  {
> -       const struct net_device *dev = skb->dev;
> +       struct net_device *dev = skb->dev;
>         netdev_features_t features = dev->features;
>         u16 gso_segs = skb_shinfo(skb)->gso_segs;
>         __be16 protocol = skb->protocol;
> @@ -2570,11 +2570,19 @@ netdev_features_t netif_skb_features(struct sk_buff *skb)
>         if (gso_segs > dev->gso_max_segs || gso_segs < dev->gso_min_segs)
>                 features &= ~NETIF_F_GSO_MASK;
>
> +       /* If encapsulation offload request, verify we are testing
> +        * hardware encapsulation features instead of standard
> +        * features for the netdev
> +        */
> +       if (skb->encapsulation)
> +               features = netdev_intersect_features(features,
> +                                                    dev->hw_enc_features);
> +
>         if (protocol == htons(ETH_P_8021Q) || protocol == htons(ETH_P_8021AD)) {
>                 struct vlan_ethhdr *veh = (struct vlan_ethhdr *)skb->data;
>                 protocol = veh->h_vlan_encapsulated_proto;
>         } else if (!vlan_tx_tag_present(skb)) {
> -               return harmonize_features(skb, features);
> +               goto finalize;
>         }
>
>         features = netdev_intersect_features(features,
> @@ -2591,6 +2599,15 @@ netdev_features_t netif_skb_features(struct sk_buff *skb)
>                                                      NETIF_F_HW_VLAN_CTAG_TX |
>                                                      NETIF_F_HW_VLAN_STAG_TX);
>
> +finalize:
> +       if (dev->netdev_ops->ndo_features_check) {
> +               netdev_features_t dev_features;
> +
> +               dev_features = dev->netdev_ops->ndo_features_check(skb, dev,
> +                                                                  features);
> +               features = netdev_intersect_features(features, dev_features);
> +       }
> +
>         return harmonize_features(skb, features);
>  }
>  EXPORT_SYMBOL(netif_skb_features);
> @@ -2661,13 +2678,6 @@ static struct sk_buff *validate_xmit_skb(struct sk_buff *skb, struct net_device
>         if (unlikely(!skb))
>                 goto out_null;
>
> -       /* If encapsulation offload request, verify we are testing
> -        * hardware encapsulation features instead of standard
> -        * features for the netdev
> -        */
> -       if (skb->encapsulation)
> -               features &= dev->hw_enc_features;
> -
>         if (netif_needs_gso(dev, skb, features)) {
>                 struct sk_buff *segs;
>
> --
> 1.9.1
>
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