Subject: Re: [PATCH net] virtio-net: restore VIRTIO_HDR_F_DATA_VALID on receiving

From: "Michael S. Tsirkin" <[email-masked]>
Date: Fri, 20 Jan 2017 18:45:11 +0200

On Fri, Jan 20, 2017 at 02:32:42PM +0800, Jason Wang wrote:
> Commit 501db511397f ("virtio: don't set VIRTIO_NET_HDR_F_DATA_VALID on
> xmit") in fact disables VIRTIO_HDR_F_DATA_VALID on receiving path too,
> fixing this by adding a hint (has_data_valid) and set it only on the
> receiving path.
> 
> Cc: Rolf Neugebauer <[email-masked]>
> Signed-off-by: Jason Wang <[email-masked]>
> ---
>  drivers/net/macvtap.c      | 2 +-
>  drivers/net/tun.c          | 2 +-
>  drivers/net/virtio_net.c   | 2 +-
>  include/linux/virtio_net.h | 6 +++++-
>  net/packet/af_packet.c     | 4 ++--
>  5 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> index 5c26653..4026185 100644
> --- a/drivers/net/macvtap.c
> +++ b/drivers/net/macvtap.c
> @@ -825,7 +825,7 @@ static ssize_t macvtap_put_user(struct macvtap_queue *q,
>  			return -EINVAL;
>  
>  		if (virtio_net_hdr_from_skb(skb, &vnet_hdr,
> -					    macvtap_is_little_endian(q)))
> +					    macvtap_is_little_endian(q), true))
>  			BUG();
>  
>  		if (copy_to_iter(&vnet_hdr, sizeof(vnet_hdr), iter) !=
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index cd8e02c..2cd10b2 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -1360,7 +1360,7 @@ static ssize_t tun_put_user(struct tun_struct *tun,
>  			return -EINVAL;
>  
>  		if (virtio_net_hdr_from_skb(skb, &gso,
> -					    tun_is_little_endian(tun))) {
> +					    tun_is_little_endian(tun), true)) {
>  			struct skb_shared_info *sinfo = skb_shinfo(skb);
>  			pr_err("unexpected GSO type: "
>  			       "0x%x, gso_size %d, hdr_len %d\n",
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 4a10500..3474243 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1104,7 +1104,7 @@ static int xmit_skb(struct send_queue *sq, struct sk_buff *skb)
>  		hdr = skb_vnet_hdr(skb);
>  
>  	if (virtio_net_hdr_from_skb(skb, &hdr->hdr,
> -				    virtio_is_little_endian(vi->vdev)))
> +				    virtio_is_little_endian(vi->vdev), false))
>  		BUG();
>  
>  	if (vi->mergeable_rx_bufs)
> diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
> index 5643647..5209b5e 100644
> --- a/include/linux/virtio_net.h
> +++ b/include/linux/virtio_net.h
> @@ -56,7 +56,8 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
>  
>  static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
>  					  struct virtio_net_hdr *hdr,
> -					  bool little_endian)
> +					  bool little_endian,
> +					  bool has_data_valid)
>  {
>  	memset(hdr, 0, sizeof(*hdr));   /* no info leak */
>  

I would prefer naming it is_rx. Callers should not know about
internal details like data valid, the issue we are trying to fix
here is that tx and tx headers are slightly different.

> @@ -91,6 +92,9 @@ static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
>  				skb_checksum_start_offset(skb));
>  		hdr->csum_offset = __cpu_to_virtio16(little_endian,
>  				skb->csum_offset);
> +	} else if (has_data_valid &&
> +		   skb->ip_summed == CHECKSUM_UNNECESSARY) {
> +		hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
>  	} /* else everything is zero */
>  
>  	return 0;
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index b9e1a13..3d555c7 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -1976,7 +1976,7 @@ static int packet_rcv_vnet(struct msghdr *msg, const struct sk_buff *skb,
>  		return -EINVAL;
>  	*len -= sizeof(vnet_hdr);
>  
> -	if (virtio_net_hdr_from_skb(skb, &vnet_hdr, vio_le()))
> +	if (virtio_net_hdr_from_skb(skb, &vnet_hdr, vio_le(), true))
>  		return -EINVAL;
>  
>  	return memcpy_to_msg(msg, (void *)&vnet_hdr, sizeof(vnet_hdr));
> @@ -2237,7 +2237,7 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
>  	if (po->has_vnet_hdr) {
>  		if (virtio_net_hdr_from_skb(skb, h.raw + macoff -
>  					    sizeof(struct virtio_net_hdr),
> -					    vio_le())) {
> +					    vio_le(), true)) {
>  			spin_lock(&sk->sk_receive_queue.lock);
>  			goto drop_n_account;
>  		}
> -- 
> 2.7.4