Re: [PATCH net-next v11 09/12] virtio_net: Implement IPv4 ethtool flow rules

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Nov 19, 2025 at 10:33:31AM -0600, Dan Jurgens wrote:
> On 11/19/25 3:18 AM, Michael S. Tsirkin wrote:
> > On Tue, Nov 18, 2025 at 04:31:09PM -0500, Michael S. Tsirkin wrote:
> >>> +static int setup_ip_key_mask(struct virtio_net_ff_selector *selector,
> >>> +			     u8 *key,
> >>> +			     const struct ethtool_rx_flow_spec *fs)
> >>> +{
> >>> +	struct iphdr *v4_m = (struct iphdr *)&selector->mask;
> >>> +	struct iphdr *v4_k = (struct iphdr *)key;
> >>> +
> >>> +	selector->type = VIRTIO_NET_FF_MASK_TYPE_IPV4;
> >>> +	selector->length = sizeof(struct iphdr);
> >>> +
> >>> +	if (fs->h_u.usr_ip4_spec.l4_4_bytes ||
> >>> +	    fs->h_u.usr_ip4_spec.tos ||
> >>> +	    fs->h_u.usr_ip4_spec.ip_ver != ETH_RX_NFC_IP4)
> >>> +		return -EOPNOTSUPP;
> >>
> >> So include/uapi/linux/ethtool.h says:
> >>
> >>  * struct ethtool_usrip4_spec - general flow specification for IPv4
> >>  * @ip4src: Source host
> >>  * @ip4dst: Destination host
> >>  * @l4_4_bytes: First 4 bytes of transport (layer 4) header
> >>  * @tos: Type-of-service
> >>  * @ip_ver: Value must be %ETH_RX_NFC_IP4; mask must be 0
> >>  * @proto: Transport protocol number; mask must be 0
> >>
> >> I guess this ETH_RX_NFC_IP4 check validates that userspace follows this
> >> documentation? But then shouldn't you check the mask
> >> as well? and mask for proto?
> >>
> >>
> >>
> > 
> > in fact, what if e.g. tos is 0 but mask is non-zero? should not
> > this be rejected, too?
> > 
> 
> Actually the tos check should be removed, there's no guidance it should
> be 0, like the other fields. Our hardware doesn't support it, but this
> will be caught in validate_classifier_selectors.

same question for l4_4_bytes then.

-- 
MST