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Date: Fri, 22 May 2020 18:02:54 +0200
From: Toke Høiland-Jørgensen <toke@...hat.com>
To: David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org
Cc: davem@...emloft.net, kuba@...nel.org, brouer@...hat.com,
daniel@...earbox.net, john.fastabend@...il.com, ast@...nel.org,
kafai@...com, songliubraving@...com, yhs@...com, andriin@...com,
dsahern@...il.com, David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH RFC bpf-next 2/4] bpf: Add support to attach bpf program to a devmap
David Ahern <dsahern@...nel.org> writes:
> Add BPF_XDP_DEVMAP attach type for use with programs associated with a
> DEVMAP.
>
> DEVMAPs can associate a program with a device entry by setting the
> value to <index,id> pair. The program associated with the id must have
> type XDP with expected attach type BPF_XDP_DEVMAP. When a program is
> associated with a device index, the program is run on an XDP_REDIRECT
> and before the buffer is added to the per-cpu queue. At this point
> rxq data is still valid; the next patch adds tx device information
> allowing the prorgam to see both ingress and egress device indices.
>
> XDP generic is skb based and XDP programs do not work with skb's. Block
> the use case by walking maps used by a program that is to be attached
> via xdpgeneric and fail if any of them are DEVMAP / DEVMAP_HASH with
> 8-bytes values.
>
> Signed-off-by: David Ahern <dsahern@...nel.org>
> ---
> include/linux/bpf.h | 5 +++
> include/uapi/linux/bpf.h | 1 +
> kernel/bpf/devmap.c | 82 +++++++++++++++++++++++++++++++---
> net/core/dev.c | 18 ++++++++
> tools/include/uapi/linux/bpf.h | 1 +
> 5 files changed, 102 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index efe8836b5c48..088751bc09aa 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -1242,6 +1242,7 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
> struct net_device *dev_rx);
> int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
> struct bpf_prog *xdp_prog);
> +bool dev_map_can_have_prog(struct bpf_map *map);
>
> struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key);
> void __cpu_map_flush(void);
> @@ -1355,6 +1356,10 @@ static inline struct net_device *__dev_map_hash_lookup_elem(struct bpf_map *map
> {
> return NULL;
> }
> +static inline bool dev_map_can_have_prog(struct bpf_map *map)
> +{
> + return false;
> +}
>
> static inline void __dev_flush(void)
> {
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 97e1fd19ff58..8c2c0d0c9a0e 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -224,6 +224,7 @@ enum bpf_attach_type {
> BPF_CGROUP_INET6_GETPEERNAME,
> BPF_CGROUP_INET4_GETSOCKNAME,
> BPF_CGROUP_INET6_GETSOCKNAME,
> + BPF_XDP_DEVMAP,
> __MAX_BPF_ATTACH_TYPE
> };
>
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index 2c01ce434306..06f4c746fa7c 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -70,6 +70,7 @@ 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 bpf_prog *xdp_prog;
> struct rcu_head rcu;
> unsigned int idx;
> struct dev_map_ext_val val;
> @@ -228,6 +229,8 @@ static void dev_map_free(struct bpf_map *map)
>
> hlist_for_each_entry_safe(dev, next, head, index_hlist) {
> hlist_del_rcu(&dev->index_hlist);
> + if (dev->xdp_prog)
> + bpf_prog_put(dev->xdp_prog);
> dev_put(dev->dev);
> kfree(dev);
> }
> @@ -242,6 +245,8 @@ static void dev_map_free(struct bpf_map *map)
> if (!dev)
> continue;
>
> + if (dev->xdp_prog)
> + bpf_prog_put(dev->xdp_prog);
> dev_put(dev->dev);
> kfree(dev);
> }
> @@ -328,6 +333,16 @@ static int dev_map_hash_get_next_key(struct bpf_map *map, void *key,
> return -ENOENT;
> }
>
> +bool dev_map_can_have_prog(struct bpf_map *map)
> +{
> + if ((map->map_type == BPF_MAP_TYPE_DEVMAP ||
> + map->map_type == BPF_MAP_TYPE_DEVMAP_HASH) &&
> + map->value_size == 8)
> + return true;
> +
> + return false;
> +}
> +
> static int bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
> {
> struct net_device *dev = bq->dev;
> @@ -452,6 +467,39 @@ static inline int __xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
> return bq_enqueue(dev, xdpf, dev_rx);
> }
>
> +static struct xdp_buff *dev_map_run_prog(struct net_device *dev,
> + struct xdp_buff *xdp,
> + struct bpf_prog *xdp_prog)
> +{
> + u32 act;
> +
> + act = bpf_prog_run_xdp(xdp_prog, xdp);
> + switch (act) {
> + case XDP_DROP:
> + fallthrough;
> + case XDP_PASS:
> + break;
> + case XDP_TX:
> + fallthrough;
> + case XDP_REDIRECT:
> + fallthrough;
> + default:
> + bpf_warn_invalid_xdp_action(act);
> + fallthrough;
> + case XDP_ABORTED:
> + trace_xdp_exception(dev, xdp_prog, act);
> + act = XDP_DROP;
> + break;
> + }
> +
> + if (act == XDP_DROP) {
> + xdp_return_buff(xdp);
> + xdp = NULL;
> + }
> +
> + return xdp;
> +}
> +
> int dev_xdp_enqueue(struct net_device *dev, struct xdp_buff *xdp,
> struct net_device *dev_rx)
> {
> @@ -463,6 +511,11 @@ int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
> {
> struct net_device *dev = dst->dev;
>
> + if (dst->xdp_prog) {
> + xdp = dev_map_run_prog(dev, xdp, dst->xdp_prog);
> + if (!xdp)
> + return 0;
> + }
> return __xdp_enqueue(dev, xdp, dev_rx);
> }
>
> @@ -499,6 +552,8 @@ static void __dev_map_entry_free(struct rcu_head *rcu)
> struct bpf_dtab_netdev *dev;
>
> dev = container_of(rcu, struct bpf_dtab_netdev, rcu);
> + if (dev->xdp_prog)
> + bpf_prog_put(dev->xdp_prog);
> dev_put(dev->dev);
> kfree(dev);
> }
> @@ -549,9 +604,10 @@ static int dev_map_hash_delete_elem(struct bpf_map *map, void *key)
>
> static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
> struct bpf_dtab *dtab,
> - u32 ifindex,
> + u32 ifindex, u32 prog_id,
> unsigned int idx)
> {
> + struct bpf_prog *prog = NULL;
> struct bpf_dtab_netdev *dev;
>
> dev = kmalloc_node(sizeof(*dev), GFP_ATOMIC | __GFP_NOWARN,
> @@ -563,12 +619,23 @@ static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
> if (!dev->dev)
> goto err_out;
>
> + if (prog_id) {
> + prog = bpf_prog_by_id(prog_id);
> + if (IS_ERR(prog) || prog->type != BPF_PROG_TYPE_XDP ||
> + prog->expected_attach_type != BPF_XDP_DEVMAP)
If the second or third condition fails here you never bpf_prog_put() the
prog ref.
> + goto err_dev;
> + }
> +
> dev->idx = idx;
> dev->dtab = dtab;
>
> + dev->xdp_prog = prog;
> dev->val.ifindex = ifindex;
> + dev->val.prog_id = prog_id;
>
> return dev;
> +err_dev:
> + dev_put(dev->dev);
> err_out:
> kfree(dev);
> return ERR_PTR(-EINVAL);
> @@ -580,7 +647,7 @@ 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 i = *(u32 *)key;
> - u32 ifindex;
> + u32 ifindex, id = 0;
>
> if (map->value_size == 4) {
> ifindex = *(u32 *)value;
> @@ -588,6 +655,7 @@ static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
> struct dev_map_ext_val *val = value;
>
> ifindex = val->ifindex;
> + id = val->prog_id;
> }
>
> if (unlikely(map_flags > BPF_EXIST))
> @@ -599,8 +667,11 @@ static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
>
> if (!ifindex) {
> dev = NULL;
> + /* can not specify id if ifindex is 0 */
> + if (id)
> + return -EINVAL;
> } else {
> - dev = __dev_map_alloc_node(net, dtab, ifindex, i);
> + dev = __dev_map_alloc_node(net, dtab, ifindex, id, i);
> if (IS_ERR(dev))
> return PTR_ERR(dev);
> }
> @@ -630,8 +701,8 @@ static int __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
> struct bpf_dtab_netdev *dev, *old_dev;
> u32 idx = *(u32 *)key;
> unsigned long flags;
> + u32 ifindex, id = 0;
> int err = -EEXIST;
> - u32 ifindex;
>
> if (map->value_size == 4) {
> ifindex = *(u32 *)value;
> @@ -639,6 +710,7 @@ static int __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
> struct dev_map_ext_val *val = value;
>
> ifindex = val->ifindex;
> + id = val->prog_id;
> }
>
> if (unlikely(map_flags > BPF_EXIST || !ifindex))
> @@ -650,7 +722,7 @@ static int __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
> if (old_dev && (map_flags & BPF_NOEXIST))
> goto out_err;
>
> - dev = __dev_map_alloc_node(net, dtab, ifindex, idx);
> + dev = __dev_map_alloc_node(net, dtab, ifindex, id, idx);
> if (IS_ERR(dev)) {
> err = PTR_ERR(dev);
> goto out_err;
> diff --git a/net/core/dev.c b/net/core/dev.c
> index f36bd3b21997..2571a8976cd4 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -5410,6 +5410,18 @@ static int generic_xdp_install(struct net_device *dev, struct netdev_bpf *xdp)
> struct bpf_prog *new = xdp->prog;
> int ret = 0;
>
> + if (new) {
> + u32 i;
> +
> + /* generic XDP does not work with DEVMAPs that can
> + * have a bpf_prog installed
> + */
> + for (i = 0; i < new->aux->used_map_cnt; i++) {
> + if (dev_map_can_have_prog(new->aux->used_maps[i]))
> + return -EINVAL;
> + }
> + }
> +
> switch (xdp->command) {
> case XDP_SETUP_PROG:
> rcu_assign_pointer(dev->xdp_prog, new);
> @@ -8825,6 +8837,12 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
> return -EINVAL;
> }
>
> + if (prog->expected_attach_type == BPF_XDP_DEVMAP) {
> + NL_SET_ERR_MSG(extack, "BPF_XDP_DEVMAP programs can not be attached to a device");
> + bpf_prog_put(prog);
> + return -EINVAL;
> + }
> +
> /* prog->aux->id may be 0 for orphaned device-bound progs */
> if (prog->aux->id && prog->aux->id == prog_id) {
> bpf_prog_put(prog);
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 97e1fd19ff58..8c2c0d0c9a0e 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -224,6 +224,7 @@ enum bpf_attach_type {
> BPF_CGROUP_INET6_GETPEERNAME,
> BPF_CGROUP_INET4_GETSOCKNAME,
> BPF_CGROUP_INET6_GETSOCKNAME,
> + BPF_XDP_DEVMAP,
> __MAX_BPF_ATTACH_TYPE
> };
>
> --
> 2.21.1 (Apple Git-122.3)
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