On 08/02/2026 13:51, Michael S. Tsirkin wrote:
> On Thu, Feb 05, 2026 at 04:47:00PM -0600, Daniel Jurgens wrote:
>> When probing a virtnet device, attempt to read the flow filter
>> capabilities. In order to use the feature the caps must also
>> be set. For now setting what was read is sufficient.
>>
>> This patch adds uapi definitions virtio_net flow filters define in
>> version 1.4 of the VirtIO spec.
>>
>> Signed-off-by: Daniel Jurgens <[email protected]>
>> Reviewed-by: Parav Pandit <[email protected]>
>> Reviewed-by: Shahar Shitrit <[email protected]>
>>
>> ---
>> v4:
>> - Validate the length in the selector caps
>> - Removed __free usage.
>> - Removed for(int.
>> v5:
>> - Remove unneed () after MAX_SEL_LEN macro (test bot)
>> v6:
>> - Fix sparse warning "array of flexible structures" Jakub K/Simon H
>> - Use new variable and validate ff_mask_size before set_cap. MST
>> v7:
>> - Set ff->ff_{caps, mask, actions} NULL in error path. Paolo Abeni
>> - Return errors from virtnet_ff_init, -ENOTSUPP is not fatal. Xuan
>>
>> v8:
>> - Use real_ff_mask_size when setting the selector caps. Jason Wang
>>
>> v9:
>> - Set err after failed memory allocations. Simon Horman
>>
>> v10:
>> - Return -EOPNOTSUPP in virnet_ff_init before allocing any memory.
>> Jason/Paolo.
>>
>> v11:
>> - Return -EINVAL if any resource limit is 0. Simon Horman
>> - Ensure we don't overrun alloced space of ff->ff_mask by moving the
>> real_ff_mask_size > ff_mask_size check into the loop. Simon Horman
>>
>> v12:
>> - Move uapi includes to virtio_net.c vs header file. MST
>> - Remove kernel.h header in virtio_net_ff uapi. MST
>> - WARN_ON_ONCE in error paths validating selectors. MST
>> - Move includes from .h to .c files. MST
>> - Add WARN_ON_ONCE if obj_destroy fails. MST
>> - Comment cleanup in virito_net_ff.h uapi. MST
>> - Add 2 byte pad to the end of virtio_net_ff_cap_data.
>>
>> https://lore.kernel.org/virtio-comment/[email protected]/T/#m930988a5d3db316c68546d8b61f4b94f6ebda030
>> - Cleanup and reinit in the freeze/restore path. MST
>>
>> v13:
>> - Added /* private: */ comment before reserved field. Jakub
>> - Change ff_mask validation to break at unkonwn selector type. This
>> will allow compatability with newer controllers if the types of
>> selectors is expanded. MST
>>
>> v14:
>> - Handle err from virtnet_ff_init in virtnet_restore_up. MST
>>
>> v15:
>> - In virtnet_restore_up only call virtnet_close in err path if
>> netif_runnig. AI
>>
>> v16:
>> - Return 0 from virtnet_restore_up if virtnet_init_ff return not
>> supported. AI
>>
>> v17:
>> - During restore freeze_down on error during ff_init. AI
>>
>> v18:
>> - Changed selector cap validation to verify size for each type
>> instead of just checking they weren't bigger than max size. AI
>> - Added __count_by attribute to flexible members in uapi. Paolo A
>>
>> v19:
>> - Fixed ;; and incorrect plural in comment. AI
>>
>> v20:
>> - include uapi/linux/stddef.h for __counted_by. AI
>
> AI has led you astray, sadly (
will fix in v21
>
>
>
>
>> ---
>> drivers/net/virtio_net.c | 231 ++++++++++++++++++++++++++++-
>> include/uapi/linux/virtio_net_ff.h | 91 ++++++++++++
>> 2 files changed, 321 insertions(+), 1 deletion(-)
>> create mode 100644 include/uapi/linux/virtio_net_ff.h
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index db88dcaefb20..2cfa37e2f83f 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -26,6 +26,11 @@
>> #include <net/netdev_rx_queue.h>
>> #include <net/netdev_queues.h>
>> #include <net/xdp_sock_drv.h>
>> +#include <linux/virtio_admin.h>
>> +#include <net/ipv6.h>
>> +#include <net/ip.h>
>> +#include <uapi/linux/virtio_pci.h>
>> +#include <uapi/linux/virtio_net_ff.h>
>>
>> static int napi_weight = NAPI_POLL_WEIGHT;
>> module_param(napi_weight, int, 0444);
>> @@ -281,6 +286,14 @@ static const struct virtnet_stat_desc
>> virtnet_stats_tx_speed_desc_qstat[] = {
>> VIRTNET_STATS_DESC_TX_QSTAT(speed, ratelimit_packets,
>> hw_drop_ratelimits),
>> };
>>
>> +struct virtnet_ff {
>> + struct virtio_device *vdev;
>> + bool ff_supported;
>> + struct virtio_net_ff_cap_data *ff_caps;
>> + struct virtio_net_ff_cap_mask_data *ff_mask;
>> + struct virtio_net_ff_actions *ff_actions;
>> +};
>> +
>> #define VIRTNET_Q_TYPE_RX 0
>> #define VIRTNET_Q_TYPE_TX 1
>> #define VIRTNET_Q_TYPE_CQ 2
>> @@ -488,6 +501,7 @@ struct virtnet_info {
>> TRAILING_OVERLAP(struct virtio_net_rss_config_trailer, rss_trailer,
>> hash_key_data,
>> u8 rss_hash_key_data[VIRTIO_NET_RSS_MAX_KEY_SIZE];
>> );
>> + struct virtnet_ff ff;
>> };
>> static_assert(offsetof(struct virtnet_info, rss_trailer.hash_key_data) ==
>> offsetof(struct virtnet_info, rss_hash_key_data));
>> @@ -526,6 +540,7 @@ static struct sk_buff *virtnet_skb_append_frag(struct
>> sk_buff *head_skb,
>> struct page *page, void *buf,
>> int len, int truesize);
>> static void virtnet_xsk_completed(struct send_queue *sq, int num);
>> +static void remove_vq_common(struct virtnet_info *vi);
>>
>> enum virtnet_xmit_type {
>> VIRTNET_XMIT_TYPE_SKB,
>> @@ -5684,6 +5699,192 @@ static const struct netdev_stat_ops virtnet_stat_ops
>> = {
>> .get_base_stats = virtnet_get_base_stats,
>> };
>>
>> +static size_t get_mask_size(u16 type)
>> +{
>> + switch (type) {
>> + case VIRTIO_NET_FF_MASK_TYPE_ETH:
>> + return sizeof(struct ethhdr);
>> + case VIRTIO_NET_FF_MASK_TYPE_IPV4:
>> + return sizeof(struct iphdr);
>> + case VIRTIO_NET_FF_MASK_TYPE_IPV6:
>> + return sizeof(struct ipv6hdr);
>> + case VIRTIO_NET_FF_MASK_TYPE_TCP:
>> + return sizeof(struct tcphdr);
>> + case VIRTIO_NET_FF_MASK_TYPE_UDP:
>> + return sizeof(struct udphdr);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int virtnet_ff_init(struct virtnet_ff *ff, struct virtio_device
>> *vdev)
>> +{
>> + size_t ff_mask_size = sizeof(struct virtio_net_ff_cap_mask_data) +
>> + sizeof(struct virtio_net_ff_selector) *
>> + VIRTIO_NET_FF_MASK_TYPE_MAX;
>> + struct virtio_admin_cmd_query_cap_id_result *cap_id_list;
>> + struct virtio_net_ff_selector *sel;
>> + unsigned long sel_types = 0;
>> + size_t real_ff_mask_size;
>> + int err;
>> + int i;
>> +
>> + if (!vdev->config->admin_cmd_exec)
>> + return -EOPNOTSUPP;
>> +
>> + cap_id_list = kzalloc(sizeof(*cap_id_list), GFP_KERNEL);
>> + if (!cap_id_list)
>> + return -ENOMEM;
>> +
>> + err = virtio_admin_cap_id_list_query(vdev, cap_id_list);
>> + if (err)
>> + goto err_cap_list;
>> +
>> + if (!(VIRTIO_CAP_IN_LIST(cap_id_list,
>> + VIRTIO_NET_FF_RESOURCE_CAP) &&
>> + VIRTIO_CAP_IN_LIST(cap_id_list,
>> + VIRTIO_NET_FF_SELECTOR_CAP) &&
>> + VIRTIO_CAP_IN_LIST(cap_id_list,
>> + VIRTIO_NET_FF_ACTION_CAP))) {
>> + err = -EOPNOTSUPP;
>> + goto err_cap_list;
>> + }
>> +
>> + ff->ff_caps = kzalloc(sizeof(*ff->ff_caps), GFP_KERNEL);
>> + if (!ff->ff_caps) {
>> + err = -ENOMEM;
>> + goto err_cap_list;
>> + }
>> +
>> + err = virtio_admin_cap_get(vdev,
>> + VIRTIO_NET_FF_RESOURCE_CAP,
>> + ff->ff_caps,
>> + sizeof(*ff->ff_caps));
>> +
>> + if (err)
>> + goto err_ff;
>> +
>> + if (!ff->ff_caps->groups_limit ||
>> + !ff->ff_caps->classifiers_limit ||
>> + !ff->ff_caps->rules_limit ||
>> + !ff->ff_caps->rules_per_group_limit) {
>> + err = -EINVAL;
>> + goto err_ff;
>> + }
>> +
>> + /* 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) {
>> + err = -ENOMEM;
>> + goto err_ff;
>> + }
>> +
>> + err = virtio_admin_cap_get(vdev,
>> + VIRTIO_NET_FF_SELECTOR_CAP,
>> + ff->ff_mask,
>> + ff_mask_size);
>
> So ff_actions is from device and ff_actions->count does not seem to be
> checked.
>
> If device somehow gains a larger mask down the road, can it not then overflow?
> or malicious?
see below
>
>
>> +
>> + 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) {
>> + err = -ENOMEM;
>> + 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);
>
> So ff_actions is from device and ff_actions->count is not checked.
>
> If device gains a ton of actions down the road, can it not then overflow?
> or malicious?
it can't overflow, as it can write up to sizeof(*ff->ff_actions) +
VIRTIO_NET_FF_ACTION_MAX bytes. But it is a valid concern in case of
someone in the future iterates on count. Better to handle it now so it
won't be forgotten. Checking that ff_actions->count doesn't exceed
VIRTIO_NET_FF_ACTION_MAX can break backward compatibility. If this max
value is extended in a new spec/controller then this driver would fail
to load. Instead, I will assign ff->ff_actions->count with the minimum
of what we got and the 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;
>> +
>> + real_ff_mask_size = sizeof(struct virtio_net_ff_cap_mask_data);
>> + sel = (void *)&ff->ff_mask->selectors;
>> +
>> + for (i = 0; i < ff->ff_mask->count; i++) {
>> + /* If the selector type is unknown it may indicate the spec
>> + * has been revised to include new types of selectors
>> + */
>> + if (sel->type > VIRTIO_NET_FF_MASK_TYPE_MAX)
>
> do you want to check sel->type 0 too?
yes, will add in v21.
>
>> + break;
>
> but count remains unchanged? should we not to reduce count here
> so device knows what driver can drive?
we should. will add it in v21.
>
>
>> +
>> + if (sel->length != get_mask_size(sel->type) ||
>> + test_and_set_bit(sel->type, &sel_types)) {
>> + WARN_ON_ONCE(true);
>> + err = -EINVAL;
>> + goto err_ff_action;
>> + }
>> + real_ff_mask_size += sizeof(struct virtio_net_ff_selector) +
>> sel->length;
>> + if (real_ff_mask_size > ff_mask_size) {
>> + WARN_ON_ONCE(true);
>> + err = -EINVAL;
>> + goto err_ff_action;
>> + }
>> + sel = (void *)sel + sizeof(*sel) + sel->length;
>> + }
>> +
>> + err = virtio_admin_cap_set(vdev,
>> + VIRTIO_NET_FF_SELECTOR_CAP,
>> + ff->ff_mask,
>> + real_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 0;
>> +
>> +err_ff_action:
>> + kfree(ff->ff_actions);
>> + ff->ff_actions = NULL;
>> +err_ff_mask:
>> + kfree(ff->ff_mask);
>> + ff->ff_mask = NULL;
>> +err_ff:
>> + kfree(ff->ff_caps);
>> + ff->ff_caps = NULL;
>> +err_cap_list:
>> + kfree(cap_id_list);
>> +
>> + return err;
>> +}
>> +
>> +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);
>> + ff->ff_supported = false;
>> +}
>> +
>> static void virtnet_freeze_down(struct virtio_device *vdev)
>> {
>> struct virtnet_info *vi = vdev->priv;
>> @@ -5702,6 +5903,10 @@ static void virtnet_freeze_down(struct virtio_device
>> *vdev)
>> netif_tx_lock_bh(vi->dev);
>> netif_device_detach(vi->dev);
>> netif_tx_unlock_bh(vi->dev);
>> +
>> + rtnl_lock();
>> + virtnet_ff_cleanup(&vi->ff);
>> + rtnl_unlock();
>> }
>>
>> static int init_vqs(struct virtnet_info *vi);
>> @@ -5727,10 +5932,23 @@ static int virtnet_restore_up(struct virtio_device
>> *vdev)
>> return err;
>> }
>>
>> + /* Initialize flow filters. Not supported is an acceptable and common
>> + * return code
>> + */
>> + rtnl_lock();
>> + err = virtnet_ff_init(&vi->ff, vi->vdev);
>> + if (err && err != -EOPNOTSUPP) {
>> + rtnl_unlock();
>> + virtnet_freeze_down(vi->vdev);
>> + remove_vq_common(vi);
>> + return err;
>> + }
>> + rtnl_unlock();
>> +
>> netif_tx_lock_bh(vi->dev);
>> netif_device_attach(vi->dev);
>> netif_tx_unlock_bh(vi->dev);
>> - return err;
>> + return 0;
>> }
>>
>> static int virtnet_set_guest_offloads(struct virtnet_info *vi, u64 offloads)
>> @@ -7058,6 +7276,15 @@ static int virtnet_probe(struct virtio_device *vdev)
>> }
>> vi->guest_offloads_capable = vi->guest_offloads;
>>
>> + /* Initialize flow filters. Not supported is an acceptable and common
>> + * return code
>> + */
>> + err = virtnet_ff_init(&vi->ff, vi->vdev);
>> + if (err && err != -EOPNOTSUPP) {
>> + rtnl_unlock();
>> + goto free_unregister_netdev;
>> + }
>> +
>> rtnl_unlock();
>>
>> err = virtnet_cpu_notif_add(vi);
>> @@ -7073,6 +7300,7 @@ 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:
>> @@ -7121,6 +7349,7 @@ 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/uapi/linux/virtio_net_ff.h
>> b/include/uapi/linux/virtio_net_ff.h
>> new file mode 100644
>> index 000000000000..552a6b3a8a91
>> --- /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 <uapi/linux/stddef.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
>> + */
>> +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;
>> + /* private: */
>> + __u8 reserved[2];
>> +};
>> +
>> +/**
>> + * 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[] __counted_by(length);
>> +};
>> +
>> +#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: packed array of struct virtio_net_ff_selector.
>> + */
>> +struct virtio_net_ff_cap_mask_data {
>> + __u8 count;
>> + __u8 reserved[7];
>> + __u8 selectors[] __counted_by(count);
>
> This looks wrong to me. count is # of selectors (packed entries) not
> bytes.
right, will remove it.
> >
>
>
>> +};
>> +
>> +#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[] __counted_by(count);
>
>
> this too.
count directly represents the number of __u8 elements in actions[], so
the size of the flexible array is count * sizeof(__u8). Therefore, here
it is correct.
>
>> +};
>> +#endif
>> --
>> 2.50.1
>
>
