On Thu, 21 May 2020 19:05:23 -0600
David Ahern <dsah...@kernel.org> wrote:
> Add support to DEVMAP and DEVMAP_HASH to support 8-byte values as a
> <device index, program id> pair. To do this, a new struct is needed in
> bpf_dtab_netdev to hold the values to return on lookup.
I would like to see us leverage BTF instead of checking on the size
attr->value_size. E.g do the sanity check based on BTF.
Given I don't know the exact details on how this should be done, I will
look into it... I already promised Lorenzo, as we have already
discussed this on IRC.
So, you can Lorenzo can go ahead with this approach, and test the
use-case. And I'll try to figure out if-and-how we can leverage BTF
here. Input from BTF experts will be much appreciated.
> Signed-off-by: David Ahern <dsah...@kernel.org>
> ---
> kernel/bpf/devmap.c | 53 ++++++++++++++++++++++++++++++++++-----------
> 1 file changed, 40 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index a51d9fb7a359..2c01ce434306 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -60,12 +60,19 @@ struct xdp_dev_bulk_queue {
> unsigned int count;
> };
>
> +/* devmap value can be dev index or dev index + prog id */
> +struct dev_map_ext_val {
> + u32 ifindex; /* must be first for compat with 4-byte values */
> + u32 prog_id;
> +};
> +
> struct bpf_dtab_netdev {
> struct net_device *dev; /* must be first member, due to tracepoint */
> struct hlist_node index_hlist;
> struct bpf_dtab *dtab;
> struct rcu_head rcu;
> unsigned int idx;
> + struct dev_map_ext_val val;
> };
>
> struct bpf_dtab {
> @@ -108,9 +115,13 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union
> bpf_attr *attr)
> u64 cost = 0;
> int err;
>
> - /* check sanity of attributes */
> + /* check sanity of attributes. 2 value sizes supported:
> + * 4 bytes: ifindex
> + * 8 bytes: ifindex + prog id
> + */
> if (attr->max_entries == 0 || attr->key_size != 4 ||
> - attr->value_size != 4 || attr->map_flags & ~DEV_CREATE_FLAG_MASK)
> + (attr->value_size != 4 && attr->value_size != 8) ||
> + attr->map_flags & ~DEV_CREATE_FLAG_MASK)
> return -EINVAL;
>
> /* Lookup returns a pointer straight to dev->ifindex, so make sure the
[...]
> static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
> @@ -568,8 +579,16 @@ static int __dev_map_update_elem(struct net *net, struct
> bpf_map *map,
> {
> struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
> struct bpf_dtab_netdev *dev, *old_dev;
> - u32 ifindex = *(u32 *)value;
> u32 i = *(u32 *)key;
> + u32 ifindex;
> +
> + if (map->value_size == 4) {
> + ifindex = *(u32 *)value;
> + } else {
> + struct dev_map_ext_val *val = value;
> +
> + ifindex = val->ifindex;
> + }
>
> if (unlikely(map_flags > BPF_EXIST))
> return -EINVAL;
> @@ -609,10 +628,18 @@ static int __dev_map_hash_update_elem(struct net *net,
> struct bpf_map *map,
> {
> struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
> struct bpf_dtab_netdev *dev, *old_dev;
> - u32 ifindex = *(u32 *)value;
> u32 idx = *(u32 *)key;
> unsigned long flags;
> int err = -EEXIST;
> + u32 ifindex;
> +
> + if (map->value_size == 4) {
> + ifindex = *(u32 *)value;
> + } else {
> + struct dev_map_ext_val *val = value;
> +
> + ifindex = val->ifindex;
> + }
>
> if (unlikely(map_flags > BPF_EXIST || !ifindex))
> return -EINVAL;
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
