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SubjectRe: [PATCH v2 1/3] virtio-net: Introduce extended RSC feature
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.benditovich@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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