netdev - Re: [PATCH RFC v3 2/5] net: Add NETIF_F_GRO

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Date:   Wed, 18 Sep 2019 12:10:31 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH RFC v3 2/5] net: Add NETIF_F_GRO_LIST feature

On Wed, Sep 18, 2019 at 3:25 AM Steffen Klassert
<steffen.klassert@...unet.com> wrote:
>
> This adds a new NETIF_F_GRO_LIST feature flag. I will be used
> to configure listfyed GRO what will be implemented with some
> followup paches.

This should probably simultaneously introduce SKB_GSO_FRAGLIST as well
as a BUILD_BUG_ON in net_gso_ok.

Please also in the commit describe the constraints of skbs that have
this type. If I'm not mistaken, an skb with either gso_size linear
data or one gso_sized frag, followed by a frag_list of the same. With
the exception of the last frag_list member, whose mss may be less than
gso_size. This will help when reasoning about all the types of skbs we
may see at segmentation, as we recently had to do [1]

Minor nit: I think it's listified, not listifyed.

[1] https://lore.kernel.org/netdev/CA+FuTSfVsgNDi7c=GUU8nMg2hWxF2SjCNLXetHeVPdnxAW5K-w@mail.gmail.com/

> Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
> ---



>  include/linux/netdev_features.h | 2 ++
>  net/core/ethtool.c              | 1 +
>  2 files changed, 3 insertions(+)
>
> diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
> index 4b19c544c59a..1b6baa1b6fe9 100644
> --- a/include/linux/netdev_features.h
> +++ b/include/linux/netdev_features.h
> @@ -80,6 +80,7 @@ enum {
>
>         NETIF_F_GRO_HW_BIT,             /* Hardware Generic receive offload */
>         NETIF_F_HW_TLS_RECORD_BIT,      /* Offload TLS record */
> +       NETIF_F_GRO_LIST_BIT,           /* Listifyed GRO */
>
>         /*
>          * Add your fresh new feature above and remember to update
> @@ -150,6 +151,7 @@ enum {
>  #define NETIF_F_GSO_UDP_L4     __NETIF_F(GSO_UDP_L4)
>  #define NETIF_F_HW_TLS_TX      __NETIF_F(HW_TLS_TX)
>  #define NETIF_F_HW_TLS_RX      __NETIF_F(HW_TLS_RX)
> +#define NETIF_F_GRO_LIST       __NETIF_F(GRO_LIST)
>
>  /* Finds the next feature with the highest number of the range of start till 0.
>   */
> diff --git a/net/core/ethtool.c b/net/core/ethtool.c
> index 6288e69e94fc..ee8d2b58c2d7 100644
> --- a/net/core/ethtool.c
> +++ b/net/core/ethtool.c
> @@ -111,6 +111,7 @@ static const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN]
>         [NETIF_F_HW_TLS_RECORD_BIT] =   "tls-hw-record",
>         [NETIF_F_HW_TLS_TX_BIT] =        "tls-hw-tx-offload",
>         [NETIF_F_HW_TLS_RX_BIT] =        "tls-hw-rx-offload",
> +       [NETIF_F_GRO_LIST_BIT] =         "rx-gro-list",
>  };
>
>  static const char
> --
> 2.17.1
>