# Re: \[PATCH net v3 1/2\] net: core: propagate unreadable flag in skb\_zerocopy

- From: Ilya Maximets \<i.maximets@ovn.org\>
- Date: 2026-08-12 15:52:16 
- List: netdev
- Page: https://ratatoskr.run/netdev/2026/08/17403260
- Thread: https://ratatoskr.run/netdev/2026/08/17398683/t.md

```text
On 8/11/26 9:53 PM, Mina Almasry wrote:
> diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
> index ae69b2cabab9e..482893a5f67dc 100644
> --- a/net/openvswitch/datapath.c
> +++ b/net/openvswitch/datapath.c
> @@ -467,6 +467,9 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
>  	if (!dp_ifindex)
>  		return -ENODEV;
>  
> +	if (!skb_frags_readable(skb))
> +		return -EFAULT;
> +
>  	if (skb_vlan_tag_present(skb)) {
>  		nskb = skb_clone(skb, GFP_ATOMIC);
>  		if (!nskb)
FWIW, the devmem integration doesn't seem well-designed.  I understand
that it is for performance, but IMO there should be a way to copy the
data on a slow path to avoid dropping the packets.  Clamping without
notifying the users that the packet is truncated is not a good solution.
Not for OVS, not for other parts of the kernel networking stack.  It's
a uAPI breakage.

As it is, there is not much we can do here without extensive changes
in userspace applications, so for this OVS block:

Reviewed-by: Ilya Maximets <i.maximets@ovn.org>
```