On Sun, Mar 01, 2020 at 01:07:31PM +0200, Yuri Benditovich wrote:
> VIRTIO_NET_F_RSC_EXT feature bit indicates that the device
> is able to provide extended RSC information. When the feature
> is negotiatede and 'gso_type' field in received packet is not
> GSO_NONE, the device reports number of coalesced packets in
> 'csum_start' field and number of duplicated acks in 'csum_offset'
> field and sets VIRTIO_NET_HDR_F_RSC_INFO in 'flags' field.
> 
> Signed-off-by: Yuri Benditovich <yuri.benditov...@daynix.com>
> ---
>  include/uapi/linux/virtio_net.h | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> index a3715a3224c1..536152fad3c4 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -57,6 +57,7 @@
>                                        * Steering */
>  #define VIRTIO_NET_F_CTRL_MAC_ADDR 23        /* Set MAC address */
>  
> +#define VIRTIO_NET_F_RSC_EXT   61    /* extended coalescing info */
>  #define VIRTIO_NET_F_STANDBY   62    /* Act as standby for another device
>                                        * with the same MAC.
>                                        */
> @@ -104,6 +105,7 @@ struct virtio_net_config {
>  struct virtio_net_hdr_v1 {
>  #define VIRTIO_NET_HDR_F_NEEDS_CSUM  1       /* Use csum_start, csum_offset 
> */
>  #define VIRTIO_NET_HDR_F_DATA_VALID  2       /* Csum is valid */
> +#define VIRTIO_NET_HDR_F_RSC_INFO    4       /* rsc info in csum_ fields */
>       __u8 flags;
>  #define VIRTIO_NET_HDR_GSO_NONE              0       /* Not a GSO frame */
>  #define VIRTIO_NET_HDR_GSO_TCPV4     1       /* GSO frame, IPv4 TCP (TSO) */
> @@ -113,8 +115,14 @@ struct virtio_net_hdr_v1 {
>       __u8 gso_type;
>       __virtio16 hdr_len;     /* Ethernet + IP + tcp/udp hdrs */
>       __virtio16 gso_size;    /* Bytes to append to hdr_len per frame */
> -     __virtio16 csum_start;  /* Position to start checksumming from */
> -     __virtio16 csum_offset; /* Offset after that to place checksum */
> +     union {
> +             __virtio16 csum_start;  /* Position to start checksumming from 
> */
> +             __le16 rsc_ext_num_packets; /* num of coalesced packets */
> +     };
> +     union {
> +             __virtio16 csum_offset; /* Offset after that to place checksum 
> */
> +             __le16 rsc_ext_num_dupacks; /* num of duplicated acks */

dupacks -> dup_acks ?

Also wouldn't it be cleaner to have an rsc struct? And "num" is kind of
extraneous, right?
So how about we group the fields:

union {
        /* Unnamed struct for compatiblity. */
        struct {
                csum_start
                csum_offset
        };
        struct {
                virtio16 start;
                virtio16 offset;
        } csum;
        struct {
                le16 packets;
                le16 dup_acks;
        } rsc;
};


what do you think?


> +     };
>       __virtio16 num_buffers; /* Number of merged rx buffers */
>  };



> -- 
> 2.17.1

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