netdev - Re: [PATCH RFC (resend) net-next 3/6] virtio_net: Add basic skeleton for handling vnet header extensions.

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Date:   Tue, 18 Apr 2017 10:52:42 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Vladislav Yasevich <vyasevich@...il.com>, netdev@...r.kernel.org
Cc:     virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org, mst@...hat.com,
        maxime.coquelin@...hat.com,
        Vladislav Yasevich <vyasevic@...hat.com>
Subject: Re: [PATCH RFC (resend) net-next 3/6] virtio_net: Add basic skeleton
 for handling vnet header extensions.



On 2017年04月16日 00:38, Vladislav Yasevich wrote:
> This is the basic sceleton which will be fleshed out by individiual
> extensions.
>
> Signed-off-by: Vladislav Yasevich <vyasevic@...hat.com>
> ---
>   drivers/net/virtio_net.c        | 21 +++++++++++++++++++++
>   include/linux/virtio_net.h      | 12 ++++++++++++
>   include/uapi/linux/virtio_net.h | 11 +++++++++++
>   3 files changed, 44 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 5ad6ee6..08e2709 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -145,6 +145,10 @@ struct virtnet_info {
>   	/* Packet virtio header size */
>   	u8 hdr_len;
>   
> +	/* Header extensions were negotiated */
> +	bool hdr_ext;
> +	u32 ext_mask;
> +
>   	/* Active statistics */
>   	struct virtnet_stats __percpu *stats;
>   
> @@ -174,6 +178,11 @@ struct virtnet_info {
>   	u32 speed;
>   };
>   
> +struct virtio_net_hdr_max {
> +	struct virtio_net_hdr_mrg_rxbuf hdr;
> +	struct virtio_net_ext_hdr ext_hdr;
> +};
> +
>   static inline u8 padded_vnet_hdr(struct virtnet_info *vi)
>   {
>   	u8 hdr_len = vi->hdr_len;
> @@ -214,6 +223,7 @@ static int rxq2vq(int rxq)
>   
>   static inline struct virtio_net_hdr_mrg_rxbuf *skb_vnet_hdr(struct sk_buff *skb)
>   {
> +	BUILD_BUG_ON(sizeof(struct virtio_net_hdr_max) > sizeof(skb->cb));
>   	return (struct virtio_net_hdr_mrg_rxbuf *)skb->cb;
>   }
>   
> @@ -767,6 +777,12 @@ static int receive_buf(struct virtnet_info *vi, struct receive_queue *rq,
>   		goto frame_err;
>   	}
>   
> +	if (vi->hdr_ext &&
> +	    virtio_net_ext_to_skb(skb,
> +				  (struct virtio_net_ext_hdr *)(hdr + 1))) {
> +		goto frame_err;
> +	}
> +
>   	skb->protocol = eth_type_trans(skb, dev);
>   	pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
>   		 ntohs(skb->protocol), skb->len, skb->pkt_type);
> @@ -1106,6 +1122,11 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
>   	if (vi->mergeable_rx_bufs)
>   		hdr->num_buffers = 0;
>   
> +	if (vi->hdr_ext &&
> +	    virtio_net_ext_from_skb(skb, (struct virtio_net_ext_hdr *)(hdr + 1),
> +				    vi->ext_mask))
> +		BUG();
> +
>   	sg_init_table(sq->sg, skb_shinfo(skb)->nr_frags + (can_push ? 1 : 2));
>   	if (can_push) {
>   		__skb_push(skb, hdr_len);
> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index 5209b5e..eaa524f 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -100,4 +100,16 @@ static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
>   	return 0;
>   }
>   
> +static inline int virtio_net_ext_to_skb(struct sk_buff *skb,
> +					struct virtio_net_ext_hdr *ext)
> +{
> +	return 0;
> +}
> +
> +static inline int virtio_net_ext_from_skb(const struct sk_buff *skb,
> +					  struct virtio_net_ext_hdr *ext,
> +					  __u32 ext_mask)
> +{
> +	return 0;
> +}
>   #endif /* _LINUX_VIRTIO_NET_H */
> diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h
> index fc353b5..0039b72 100644
> --- a/include/uapi/linux/virtio_net.h
> +++ b/include/uapi/linux/virtio_net.h
> @@ -88,6 +88,7 @@ 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_VNET_EXT	4	/* Vnet extensions present */
>   	__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) */
> @@ -102,6 +103,16 @@ struct virtio_net_hdr_v1 {
>   	__virtio16 num_buffers;	/* Number of merged rx buffers */
>   };
>   
> +/* If IRTIO_NET_HDR_F_VNET_EXT flags is set, this header immediately
> + * follows the virtio_net_hdr.  The flags in this header will indicate
> + * which extension will follow.  The extnsion data will immidiately follow

s/extnsion/extension/

> + * this header.
> + */
> +struct virtio_net_ext_hdr {
> +	__u32 flags;
> +	__u8 extensions[];
> +};
> +
>   #ifndef VIRTIO_NET_NO_LEGACY
>   /* This header comes first in the scatter-gather list.
>    * For legacy virtio, if VIRTIO_F_ANY_LAYOUT is not negotiated, it must