Subject: Re: [PATCH net-next v5 05/12] virtio_net: Query and set flow filter caps

From: "Michael S. Tsirkin" <[email-masked]>
Date: Tue, 21 Oct 2025 09:18:58 -0400

On Thu, Oct 16, 2025 at 12:00:48AM -0500, Daniel Jurgens wrote:
> +	/* VIRTIO_NET_FF_MASK_TYPE start at 1 */
> +	for (i = 1; i <= VIRTIO_NET_FF_MASK_TYPE_MAX; i++)
> +		ff_mask_size += get_mask_size(i);
> +
> +	ff->ff_mask = kzalloc(ff_mask_size, GFP_KERNEL);
> +	if (!ff->ff_mask)
> +		goto err_ff;
> +
> +	err = virtio_admin_cap_get(vdev,
> +				   VIRTIO_NET_FF_SELECTOR_CAP,
> +				   ff->ff_mask,
> +				   ff_mask_size);
> +
> +	if (err)
> +		goto err_ff_mask;
> +
> +	ff->ff_actions = kzalloc(sizeof(*ff->ff_actions) +
> +					VIRTIO_NET_FF_ACTION_MAX,
> +					GFP_KERNEL);
> +	if (!ff->ff_actions)
> +		goto err_ff_mask;
> +
> +	err = virtio_admin_cap_get(vdev,
> +				   VIRTIO_NET_FF_ACTION_CAP,
> +				   ff->ff_actions,
> +				   sizeof(*ff->ff_actions) + VIRTIO_NET_FF_ACTION_MAX);
> +
> +	if (err)
> +		goto err_ff_action;
> +
> +	err = virtio_admin_cap_set(vdev,
> +				   VIRTIO_NET_FF_RESOURCE_CAP,
> +				   ff->ff_caps,
> +				   sizeof(*ff->ff_caps));
> +	if (err)
> +		goto err_ff_action;
> +
> +	ff_mask_size = sizeof(struct virtio_net_ff_cap_mask_data);

overriding ff_mask_size seems unncessarily funky.
use a variable reflecting what this is?

> +	sel = &ff->ff_mask->selectors[0];
> +
> +	for (i = 0; i < ff->ff_mask->count; i++) {
> +		if (sel->length > MAX_SEL_LEN) {
> +			err = -EINVAL;
> +			goto err_ff_action;
> +		}

You also need to validate this is all within allocated size.

> +		ff_mask_size += sizeof(struct virtio_net_ff_selector) + sel->length;
> +		sel = (void *)sel + sizeof(*sel) + sel->length;

> +	}
> +
> +	err = virtio_admin_cap_set(vdev,
> +				   VIRTIO_NET_FF_SELECTOR_CAP,
> +				   ff->ff_mask,
> +				   ff_mask_size);
> +	if (err)
> +		goto err_ff_action;
> +
> +	err = virtio_admin_cap_set(vdev,
> +				   VIRTIO_NET_FF_ACTION_CAP,
> +				   ff->ff_actions,
> +				   sizeof(*ff->ff_actions) + VIRTIO_NET_FF_ACTION_MAX);
> +	if (err)
> +		goto err_ff_action;
> +
> +	ff->vdev = vdev;
> +	ff->ff_supported = true;
> +
> +	kfree(cap_id_list);
> +
> +	return;
> +
> +err_ff_action:
> +	kfree(ff->ff_actions);
> +err_ff_mask:
> +	kfree(ff->ff_mask);
> +err_ff:
> +	kfree(ff->ff_caps);
> +err_cap_list:
> +	kfree(cap_id_list);
> +}
> +
> +static void virtnet_ff_cleanup(struct virtnet_ff *ff)
> +{
> +	if (!ff->ff_supported)
> +		return;
> +
> +	kfree(ff->ff_actions);
> +	kfree(ff->ff_mask);
> +	kfree(ff->ff_caps);
> +}
> +
>  static int virtnet_probe(struct virtio_device *vdev)
>  {
>  	int i, err = -ENOMEM;
> @@ -7116,6 +7277,8 @@ static int virtnet_probe(struct virtio_device *vdev)
>  	}
>  	vi->guest_offloads_capable = vi->guest_offloads;
>  
> +	virtnet_ff_init(&vi->ff, vi->vdev);
> +
>  	rtnl_unlock();
>  
>  	err = virtnet_cpu_notif_add(vi);
> @@ -7131,6 +7294,7 @@ static int virtnet_probe(struct virtio_device *vdev)
>  
>  free_unregister_netdev:
>  	unregister_netdev(dev);
> +	virtnet_ff_cleanup(&vi->ff);
>  free_failover:
>  	net_failover_destroy(vi->failover);
>  free_vqs:
> @@ -7180,6 +7344,7 @@ static void virtnet_remove(struct virtio_device *vdev)
>  	virtnet_free_irq_moder(vi);
>  
>  	unregister_netdev(vi->dev);
> +	virtnet_ff_cleanup(&vi->ff);
>  
>  	net_failover_destroy(vi->failover);
>  
> diff --git a/include/linux/virtio_admin.h b/include/linux/virtio_admin.h
> index 039b996f73ec..db0f42346ca9 100644
> --- a/include/linux/virtio_admin.h
> +++ b/include/linux/virtio_admin.h
> @@ -3,6 +3,7 @@
>   * Header file for virtio admin operations
>   */
>  #include <uapi/linux/virtio_pci.h>
> +#include <uapi/linux/virtio_net_ff.h>
>  
>  #ifndef _LINUX_VIRTIO_ADMIN_H
>  #define _LINUX_VIRTIO_ADMIN_H
> diff --git a/include/uapi/linux/virtio_net_ff.h b/include/uapi/linux/virtio_net_ff.h
> new file mode 100644
> index 000000000000..1a4738889403
> --- /dev/null
> +++ b/include/uapi/linux/virtio_net_ff.h
> @@ -0,0 +1,91 @@
> +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note
> + *
> + * Header file for virtio_net flow filters
> + */
> +#ifndef _LINUX_VIRTIO_NET_FF_H
> +#define _LINUX_VIRTIO_NET_FF_H
> +
> +#include <linux/types.h>
> +#include <linux/kernel.h>
> +
> +#define VIRTIO_NET_FF_RESOURCE_CAP 0x800
> +#define VIRTIO_NET_FF_SELECTOR_CAP 0x801
> +#define VIRTIO_NET_FF_ACTION_CAP 0x802
> +
> +/**
> + * struct virtio_net_ff_cap_data - Flow filter resource capability limits
> + * @groups_limit: maximum number of flow filter groups supported by the device
> + * @classifiers_limit: maximum number of classifiers supported by the device
> + * @rules_limit: maximum number of rules supported device-wide across all groups
> + * @rules_per_group_limit: maximum number of rules allowed in a single group
> + * @last_rule_priority: priority value associated with the lowest-priority rule
> + * @selectors_per_classifier_limit: maximum selectors allowed in one classifier
> + *
> + * The limits are reported by the device and describe resource capacities for
> + * flow filters. Multi-byte fields are little-endian.
> + */
> +struct virtio_net_ff_cap_data {
> +	__le32 groups_limit;
> +	__le32 classifiers_limit;
> +	__le32 rules_limit;
> +	__le32 rules_per_group_limit;
> +	__u8 last_rule_priority;
> +	__u8 selectors_per_classifier_limit;
> +};
> +
> +/**
> + * struct virtio_net_ff_selector - Selector mask descriptor
> + * @type: selector type, one of VIRTIO_NET_FF_MASK_TYPE_* constants
> + * @flags: selector flags, see VIRTIO_NET_FF_MASK_F_* constants
> + * @reserved: must be set to 0 by the driver and ignored by the device
> + * @length: size in bytes of @mask
> + * @reserved1: must be set to 0 by the driver and ignored by the device
> + * @mask: variable-length mask payload for @type, length given by @length
> + *
> + * A selector describes a header mask that a classifier can apply. The format
> + * of @mask depends on @type.
> + */
> +struct virtio_net_ff_selector {
> +	__u8 type;
> +	__u8 flags;
> +	__u8 reserved[2];
> +	__u8 length;
> +	__u8 reserved1[3];
> +	__u8 mask[];
> +};
> +
> +#define VIRTIO_NET_FF_MASK_TYPE_ETH  1
> +#define VIRTIO_NET_FF_MASK_TYPE_IPV4 2
> +#define VIRTIO_NET_FF_MASK_TYPE_IPV6 3
> +#define VIRTIO_NET_FF_MASK_TYPE_TCP  4
> +#define VIRTIO_NET_FF_MASK_TYPE_UDP  5
> +#define VIRTIO_NET_FF_MASK_TYPE_MAX  VIRTIO_NET_FF_MASK_TYPE_UDP
> +
> +/**
> + * struct virtio_net_ff_cap_mask_data - Supported selector mask formats
> + * @count: number of entries in @selectors
> + * @reserved: must be set to 0 by the driver and ignored by the device
> + * @selectors: array of supported selector descriptors
> + */
> +struct virtio_net_ff_cap_mask_data {
> +	__u8 count;
> +	__u8 reserved[7];
> +	struct virtio_net_ff_selector selectors[];
> +};
> +#define VIRTIO_NET_FF_MASK_F_PARTIAL_MASK (1 << 0)
> +
> +#define VIRTIO_NET_FF_ACTION_DROP 1
> +#define VIRTIO_NET_FF_ACTION_RX_VQ 2
> +#define VIRTIO_NET_FF_ACTION_MAX  VIRTIO_NET_FF_ACTION_RX_VQ
> +/**
> + * struct virtio_net_ff_actions - Supported flow actions
> + * @count: number of supported actions in @actions
> + * @reserved: must be set to 0 by the driver and ignored by the device
> + * @actions: array of action identifiers (VIRTIO_NET_FF_ACTION_*)
> + */
> +struct virtio_net_ff_actions {
> +	__u8 count;
> +	__u8 reserved[7];
> +	__u8 actions[];
> +};
> +#endif
> -- 
> 2.50.1