netdev - Re: [PATCH v3 2/5] net: tun: don't assume IFF_VNET_HDR in tun_xdp

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Date:   Fri, 25 Jun 2021 14:58:32 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     David Woodhouse <dwmw2@...radead.org>, netdev@...r.kernel.org
Cc:     Eugenio Pérez <eperezma@...hat.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: [PATCH v3 2/5] net: tun: don't assume IFF_VNET_HDR in
 tun_xdp_one() tx path


在 2021/6/24 下午8:30, David Woodhouse 写道:
> From: David Woodhouse <dwmw@...zon.co.uk>
>
> Sometimes it's just a data packet. The virtio_net_hdr processing should be
> conditional on IFF_VNET_HDR, just as it is in tun_get_user().
>
> Fixes: 043d222f93ab ("tuntap: accept an array of XDP buffs through sendmsg()")
> Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>


Acked-by: Jason Wang <jasowang@...hat.com>


> ---
>   drivers/net/tun.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 67b406fa0881..9acd448e6dfc 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2331,7 +2331,7 @@ static int tun_xdp_one(struct tun_struct *tun,
>   {
>   	unsigned int datasize = xdp->data_end - xdp->data;
>   	struct tun_xdp_hdr *hdr = xdp->data_hard_start;
> -	struct virtio_net_hdr *gso = &hdr->gso;
> +	struct virtio_net_hdr *gso = NULL;
>   	struct bpf_prog *xdp_prog;
>   	struct sk_buff *skb = NULL;
>   	u32 rxhash = 0, act;
> @@ -2340,9 +2340,12 @@ static int tun_xdp_one(struct tun_struct *tun,
>   	bool skb_xdp = false;
>   	struct page *page;
>   
> +	if (tun->flags & IFF_VNET_HDR)
> +		gso = &hdr->gso;
> +
>   	xdp_prog = rcu_dereference(tun->xdp_prog);
>   	if (xdp_prog) {
> -		if (gso->gso_type) {
> +		if (gso && gso->gso_type) {
>   			skb_xdp = true;
>   			goto build;
>   		}
> @@ -2388,7 +2391,7 @@ static int tun_xdp_one(struct tun_struct *tun,
>   	skb_reserve(skb, xdp->data - xdp->data_hard_start);
>   	skb_put(skb, xdp->data_end - xdp->data);
>   
> -	if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
> +	if (gso && virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
>   		atomic_long_inc(&tun->rx_frame_errors);
>   		kfree_skb(skb);
>   		err = -EINVAL;