[PATCH v2 bpf-next 0/5] bpf: Add support for XDP programs in DEVMAP entries

[PATCH v2 bpf-next 0/5] bpf: Add support for XDP programs in DEVMAP entries

[David Ahern]

Implementation of Daniel's proposal for allowing DEVMAP entries to be
a device index, program fd pair.

Programs are run after XDP_REDIRECT and have access to both Rx device
and Tx device.

v2
- moved dev_map_ext_val definition to uapi to formalize the API for devmap
  extensions; add bpf_ prefix to the prog_fd and prog_id entries
- changed devmap code to handle struct in a way that it can support future
  extensions
- fixed subject in libbpf patch

v1
- fixed prog put on invalid program - Toke
- changed write value from id to fd per Toke's comments about capabilities
- add test cases

David Ahern (5):
  devmap: Formalize map value as a named struct
  bpf: Add support to attach bpf program to a devmap entry
  xdp: Add xdp_txq_info to xdp_buff
  libbpf: Add SEC name for xdp programs attached to device map
  selftest: Add tests for XDP programs in devmap entries

 include/linux/bpf.h                           |   5 +
 include/net/xdp.h                             |   5 +
 include/uapi/linux/bpf.h                      |  12 ++
 kernel/bpf/devmap.c                           | 119 +++++++++++++++---
 net/core/dev.c                                |  18 +++
 net/core/filter.c                             |  17 +++
 tools/include/uapi/linux/bpf.h                |  12 ++
 tools/lib/bpf/libbpf.c                        |   2 +
 .../bpf/prog_tests/xdp_devmap_attach.c        |  94 ++++++++++++++
 .../selftests/bpf/progs/test_xdp_devmap.c     |  19 +++
 .../selftests/bpf/progs/test_xdp_devmap2.c    |  19 +++
 .../bpf/progs/test_xdp_with_devmap.c          |  17 +++
 12 files changed, 322 insertions(+), 17 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_devmap.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_devmap2.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c

-- 
2.21.1 (Apple Git-122.3)

[PATCH v2 bpf-next 1/5] devmap: Formalize map value as a named struct

[David Ahern]

From: David Ahern <dsahern@gmail.com>

Add 'struct devmap_val' to the bpf uapi to formalize the
expected values that can be passed in for a DEVMAP.
Update devmap code to use the struct.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 include/uapi/linux/bpf.h       |  5 ++++
 kernel/bpf/devmap.c            | 43 ++++++++++++++++++++--------------
 tools/include/uapi/linux/bpf.h |  5 ++++
 3 files changed, 35 insertions(+), 18 deletions(-)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 54b93f8b49b8..d27302ecaa9c 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3625,6 +3625,11 @@ struct xdp_md {
 	__u32 rx_queue_index;  /* rxq->queue_index  */
 };
 
+/* DEVMAP values */
+struct devmap_val {
+	__u32 ifindex;   /* device index */
+};
+
 enum sk_action {
 	SK_DROP = 0,
 	SK_PASS,
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index a51d9fb7a359..069a50113e26 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -66,6 +66,7 @@ struct bpf_dtab_netdev {
 	struct bpf_dtab *dtab;
 	struct rcu_head rcu;
 	unsigned int idx;
+	struct devmap_val val;
 };
 
 struct bpf_dtab {
@@ -110,7 +111,8 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
 
 	/* check sanity of attributes */
 	if (attr->max_entries == 0 || attr->key_size != 4 ||
-	    attr->value_size != 4 || attr->map_flags & ~DEV_CREATE_FLAG_MASK)
+	    attr->value_size > sizeof(struct devmap_val) ||
+	    attr->map_flags & ~DEV_CREATE_FLAG_MASK)
 		return -EINVAL;
 
 	/* Lookup returns a pointer straight to dev->ifindex, so make sure the
@@ -472,18 +474,15 @@ int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
 static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key);
-	struct net_device *dev = obj ? obj->dev : NULL;
 
-	return dev ? &dev->ifindex : NULL;
+	return obj ? &obj->val : NULL;
 }
 
 static void *dev_map_hash_lookup_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_dtab_netdev *obj = __dev_map_hash_lookup_elem(map,
 								*(u32 *)key);
-	struct net_device *dev = obj ? obj->dev : NULL;
-
-	return dev ? &dev->ifindex : NULL;
+	return obj ? &obj->val : NULL;
 }
 
 static void __dev_map_entry_free(struct rcu_head *rcu)
@@ -541,7 +540,7 @@ 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,
+						    struct devmap_val *val,
 						    unsigned int idx)
 {
 	struct bpf_dtab_netdev *dev;
@@ -551,16 +550,18 @@ static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
 	if (!dev)
 		return ERR_PTR(-ENOMEM);
 
-	dev->dev = dev_get_by_index(net, ifindex);
-	if (!dev->dev) {
-		kfree(dev);
-		return ERR_PTR(-EINVAL);
-	}
+	dev->dev = dev_get_by_index(net, val->ifindex);
+	if (!dev->dev)
+		goto err_out;
 
 	dev->idx = idx;
 	dev->dtab = dtab;
+	dev->val.ifindex = val->ifindex;
 
 	return dev;
+err_out:
+	kfree(dev);
+	return ERR_PTR(-EINVAL);
 }
 
 static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
@@ -568,7 +569,7 @@ 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 ifindex = *(u32 *)value;
+	struct devmap_val val = { };
 	u32 i = *(u32 *)key;
 
 	if (unlikely(map_flags > BPF_EXIST))
@@ -578,10 +579,13 @@ static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
 	if (unlikely(map_flags == BPF_NOEXIST))
 		return -EEXIST;
 
-	if (!ifindex) {
+	/* already verified value_size <= sizeof val */
+	memcpy(&val, value, map->value_size);
+
+	if (!val.ifindex) {
 		dev = NULL;
 	} else {
-		dev = __dev_map_alloc_node(net, dtab, ifindex, i);
+		dev = __dev_map_alloc_node(net, dtab, &val, i);
 		if (IS_ERR(dev))
 			return PTR_ERR(dev);
 	}
@@ -609,12 +613,15 @@ 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;
+	struct devmap_val val = { };
 	u32 idx = *(u32 *)key;
 	unsigned long flags;
 	int err = -EEXIST;
 
-	if (unlikely(map_flags > BPF_EXIST || !ifindex))
+	/* already verified value_size <= sizeof val */
+	memcpy(&val, value, map->value_size);
+
+	if (unlikely(map_flags > BPF_EXIST || !val.ifindex))
 		return -EINVAL;
 
 	spin_lock_irqsave(&dtab->index_lock, flags);
@@ -623,7 +630,7 @@ 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, &val, idx);
 	if (IS_ERR(dev)) {
 		err = PTR_ERR(dev);
 		goto out_err;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 54b93f8b49b8..d27302ecaa9c 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3625,6 +3625,11 @@ struct xdp_md {
 	__u32 rx_queue_index;  /* rxq->queue_index  */
 };
 
+/* DEVMAP values */
+struct devmap_val {
+	__u32 ifindex;   /* device index */
+};
+
 enum sk_action {
 	SK_DROP = 0,
 	SK_PASS,
-- 
2.21.1 (Apple Git-122.3)

Re: [PATCH v2 bpf-next 1/5] devmap: Formalize map value as a named struct

[Andrii Nakryiko]

On Wed, May 27, 2020 at 5:15 PM David Ahern <dsahern@kernel.org> wrote:
>
> From: David Ahern <dsahern@gmail.com>
>
> Add 'struct devmap_val' to the bpf uapi to formalize the
> expected values that can be passed in for a DEVMAP.
> Update devmap code to use the struct.
>
> Signed-off-by: David Ahern <dsahern@gmail.com>
> ---
>  include/uapi/linux/bpf.h       |  5 ++++
>  kernel/bpf/devmap.c            | 43 ++++++++++++++++++++--------------
>  tools/include/uapi/linux/bpf.h |  5 ++++
>  3 files changed, 35 insertions(+), 18 deletions(-)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 54b93f8b49b8..d27302ecaa9c 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3625,6 +3625,11 @@ struct xdp_md {
>         __u32 rx_queue_index;  /* rxq->queue_index  */
>  };
>
> +/* DEVMAP values */
> +struct devmap_val {
> +       __u32 ifindex;   /* device index */
> +};
> +

can DEVMAP be used outside of BPF ecosystem? If not, shouldn't this be
`struct bpf_devmap_val`, to be consistent with the rest of the type
names?

>  enum sk_action {
>         SK_DROP = 0,
>         SK_PASS,
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index a51d9fb7a359..069a50113e26 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -66,6 +66,7 @@ struct bpf_dtab_netdev {
>         struct bpf_dtab *dtab;
>         struct rcu_head rcu;
>         unsigned int idx;
> +       struct devmap_val val;
>  };
>
>  struct bpf_dtab {
> @@ -110,7 +111,8 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
>
>         /* check sanity of attributes */
>         if (attr->max_entries == 0 || attr->key_size != 4 ||
> -           attr->value_size != 4 || attr->map_flags & ~DEV_CREATE_FLAG_MASK)
> +           attr->value_size > sizeof(struct devmap_val) ||

So is 0, 1, 2, 3, and after next patch 5, 6, and 7 all allowed as
well? Isn't that a bit too permissive?

> +           attr->map_flags & ~DEV_CREATE_FLAG_MASK)
>                 return -EINVAL;
>

[...]

Re: [PATCH v2 bpf-next 1/5] devmap: Formalize map value as a named struct

[David Ahern]

On 5/28/20 1:01 AM, Andrii Nakryiko wrote:
> On Wed, May 27, 2020 at 5:15 PM David Ahern <dsahern@kernel.org> wrote:
>>
>> From: David Ahern <dsahern@gmail.com>
>>
>> Add 'struct devmap_val' to the bpf uapi to formalize the
>> expected values that can be passed in for a DEVMAP.
>> Update devmap code to use the struct.
>>
>> Signed-off-by: David Ahern <dsahern@gmail.com>
>> ---
>>  include/uapi/linux/bpf.h       |  5 ++++
>>  kernel/bpf/devmap.c            | 43 ++++++++++++++++++++--------------
>>  tools/include/uapi/linux/bpf.h |  5 ++++
>>  3 files changed, 35 insertions(+), 18 deletions(-)
>>
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index 54b93f8b49b8..d27302ecaa9c 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -3625,6 +3625,11 @@ struct xdp_md {
>>         __u32 rx_queue_index;  /* rxq->queue_index  */
>>  };
>>
>> +/* DEVMAP values */
>> +struct devmap_val {
>> +       __u32 ifindex;   /* device index */
>> +};
>> +
> 
> can DEVMAP be used outside of BPF ecosystem? If not, shouldn't this be
> `struct bpf_devmap_val`, to be consistent with the rest of the type
> names?

sure, added 'bpf_' to the name.

> 
>>  enum sk_action {
>>         SK_DROP = 0,
>>         SK_PASS,
>> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
>> index a51d9fb7a359..069a50113e26 100644
>> --- a/kernel/bpf/devmap.c
>> +++ b/kernel/bpf/devmap.c
>> @@ -66,6 +66,7 @@ struct bpf_dtab_netdev {
>>         struct bpf_dtab *dtab;
>>         struct rcu_head rcu;
>>         unsigned int idx;
>> +       struct devmap_val val;
>>  };
>>
>>  struct bpf_dtab {
>> @@ -110,7 +111,8 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
>>
>>         /* check sanity of attributes */
>>         if (attr->max_entries == 0 || attr->key_size != 4 ||
>> -           attr->value_size != 4 || attr->map_flags & ~DEV_CREATE_FLAG_MASK)
>> +           attr->value_size > sizeof(struct devmap_val) ||
> 
> So is 0, 1, 2, 3, and after next patch 5, 6, and 7 all allowed as
> well? Isn't that a bit too permissive?

sure, I should check that it is at least 4-bytes - the existing size of
the values. After that the struct can vary as user and kernel differ.
The key is that newer userspace can not send down a higher value size
than the kernel supports  and older userspace can send fewer bytes
(e.g., 4-byte ifindex only vs 8-byte ifindex + fd). I'll revert this to
v1 where I check for specific known value sizes.

> 
>> +           attr->map_flags & ~DEV_CREATE_FLAG_MASK)
>>                 return -EINVAL;
>>
> 
> [...]
> 

[PATCH v2 bpf-next 2/5] bpf: Add support to attach bpf program to a devmap entry

[David Ahern]

From: David Ahern <dsahern@gmail.com>

Add BPF_XDP_DEVMAP attach type for use with programs associated with a
DEVMAP entry.

Allow DEVMAPs to associate a program with a device entry by adding
a bpf_prog_fd to 'struct devmap_val'. Values read show the program
id, so the fd and id are a union.

The program associated with the fd 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
 > 4-byte values.

Block attach of BPF_XDP_DEVMAP programs to devices.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 include/linux/bpf.h            |  5 +++
 include/uapi/linux/bpf.h       |  5 +++
 kernel/bpf/devmap.c            | 79 +++++++++++++++++++++++++++++++++-
 net/core/dev.c                 | 18 ++++++++
 tools/include/uapi/linux/bpf.h |  5 +++
 5 files changed, 110 insertions(+), 2 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 d27302ecaa9c..2d9927b7a922 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
 };
 
@@ -3628,6 +3629,10 @@ struct xdp_md {
 /* DEVMAP values */
 struct devmap_val {
 	__u32 ifindex;   /* device index */
+	union {
+		int   bpf_prog_fd;  /* prog fd on map write */
+		__u32 bpf_prog_id;  /* prog id on map read */
+	};
 };
 
 enum sk_action {
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 069a50113e26..a628585a31e1 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -64,6 +64,7 @@ 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 devmap_val val;
@@ -219,6 +220,8 @@ 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);
 			}
@@ -233,6 +236,8 @@ 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);
 		}
@@ -319,6 +324,16 @@ 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 != 4)
+		return true;
+
+	return false;
+}
+
 static int bq_xmit_all(struct xdp_dev_bulk_queue *bq, u32 flags)
 {
 	struct net_device *dev = bq->dev;
@@ -443,6 +458,35 @@ 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;
+	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)
 {
@@ -454,6 +498,11 @@ 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);
 }
 
@@ -490,6 +539,8 @@ 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);
 }
@@ -543,6 +594,7 @@ static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
 						    struct devmap_val *val,
 						    unsigned int idx)
 {
+	struct bpf_prog *prog = NULL;
 	struct bpf_dtab_netdev *dev;
 
 	dev = kmalloc_node(sizeof(*dev), GFP_ATOMIC | __GFP_NOWARN,
@@ -554,11 +606,31 @@ static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
 	if (!dev->dev)
 		goto err_out;
 
+	if (val->bpf_prog_fd >= 0) {
+		prog = bpf_prog_get_type_dev(val->bpf_prog_fd,
+					     BPF_PROG_TYPE_XDP, false);
+		if (IS_ERR(prog))
+			goto err_put_dev;
+		if (prog->expected_attach_type != BPF_XDP_DEVMAP)
+			goto err_put_prog;
+	}
+
 	dev->idx = idx;
 	dev->dtab = dtab;
+	if (prog) {
+		dev->xdp_prog = prog;
+		dev->val.bpf_prog_id = prog->aux->id;
+	} else {
+		dev->xdp_prog = NULL;
+		dev->val.bpf_prog_id = 0;
+	}
 	dev->val.ifindex = val->ifindex;
 
 	return dev;
+err_put_prog:
+	bpf_prog_put(prog);
+err_put_dev:
+	dev_put(dev->dev);
 err_out:
 	kfree(dev);
 	return ERR_PTR(-EINVAL);
@@ -568,8 +640,8 @@ static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
 				 void *key, void *value, u64 map_flags)
 {
 	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+	struct devmap_val val = { .bpf_prog_fd = -1 };
 	struct bpf_dtab_netdev *dev, *old_dev;
-	struct devmap_val val = { };
 	u32 i = *(u32 *)key;
 
 	if (unlikely(map_flags > BPF_EXIST))
@@ -584,6 +656,9 @@ static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
 
 	if (!val.ifindex) {
 		dev = NULL;
+		/* can not specify fd if ifindex is 0 */
+		if (val.bpf_prog_fd != -1)
+			return -EINVAL;
 	} else {
 		dev = __dev_map_alloc_node(net, dtab, &val, i);
 		if (IS_ERR(dev))
@@ -612,8 +687,8 @@ static int __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
 				     void *key, void *value, u64 map_flags)
 {
 	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+	struct devmap_val val = { .bpf_prog_fd = -1 };
 	struct bpf_dtab_netdev *dev, *old_dev;
-	struct devmap_val val = { };
 	u32 idx = *(u32 *)key;
 	unsigned long flags;
 	int err = -EEXIST;
diff --git a/net/core/dev.c b/net/core/dev.c
index ae37586f6ee8..10684833f864 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5420,6 +5420,18 @@ 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 on an entry
+		 */
+		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);
@@ -8835,6 +8847,12 @@ 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 d27302ecaa9c..2d9927b7a922 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
 };
 
@@ -3628,6 +3629,10 @@ struct xdp_md {
 /* DEVMAP values */
 struct devmap_val {
 	__u32 ifindex;   /* device index */
+	union {
+		int   bpf_prog_fd;  /* prog fd on map write */
+		__u32 bpf_prog_id;  /* prog id on map read */
+	};
 };
 
 enum sk_action {
-- 
2.21.1 (Apple Git-122.3)

Re: [PATCH v2 bpf-next 2/5] bpf: Add support to attach bpf program to a devmap entry

[Andrii Nakryiko]

On Wed, May 27, 2020 at 5:17 PM David Ahern <dsahern@kernel.org> wrote:
>
> From: David Ahern <dsahern@gmail.com>
>
> Add BPF_XDP_DEVMAP attach type for use with programs associated with a
> DEVMAP entry.
>
> Allow DEVMAPs to associate a program with a device entry by adding
> a bpf_prog_fd to 'struct devmap_val'. Values read show the program
> id, so the fd and id are a union.
>
> The program associated with the fd 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
>  > 4-byte values.
>
> Block attach of BPF_XDP_DEVMAP programs to devices.
>
> Signed-off-by: David Ahern <dsahern@gmail.com>
> ---

Please cc bpf@vger.kernel.org in the future for patches related to BPF
in general.

>  include/linux/bpf.h            |  5 +++
>  include/uapi/linux/bpf.h       |  5 +++
>  kernel/bpf/devmap.c            | 79 +++++++++++++++++++++++++++++++++-
>  net/core/dev.c                 | 18 ++++++++
>  tools/include/uapi/linux/bpf.h |  5 +++
>  5 files changed, 110 insertions(+), 2 deletions(-)
>

[...]

>
> +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;

nit: I don't think fallthrough is necessary for cases like:

case XDP_DROP:
case XDP_PASS:
    /* do something */

> +       case XDP_PASS:
> +               break;
> +       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;

hm.. if you move XDP_DROP case to after XDP_ABORTED and do fallthrough
from XDP_ABORTED, you won't even need to override act and it will just
handle all the cases, no?

switch (act) {
case XDP_PASS:
    return xdp;
default:
    bpf_warn_invalid_xdp_action(act);
    fallthrough;
case XDP_ABORTED:
    trace_xdp_exception(dev, xdp_prog, act);
    fallthrough;
case XDP_DROP:
    xdp_return_buff(xdp);
    return NULL;
}

Wouldn't this be simpler?


> +       }
> +
> +       return xdp;
> +}
> +

[...]

Re: [PATCH v2 bpf-next 2/5] bpf: Add support to attach bpf program to a devmap entry

[David Ahern]

On 5/28/20 1:01 AM, Andrii Nakryiko wrote:
> 
> Please cc bpf@vger.kernel.org in the future for patches related to BPF
> in general.

added to my script

> 
>>  include/linux/bpf.h            |  5 +++
>>  include/uapi/linux/bpf.h       |  5 +++
>>  kernel/bpf/devmap.c            | 79 +++++++++++++++++++++++++++++++++-
>>  net/core/dev.c                 | 18 ++++++++
>>  tools/include/uapi/linux/bpf.h |  5 +++
>>  5 files changed, 110 insertions(+), 2 deletions(-)
>>
> 
> [...]
> 
>>
>> +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;
> 
> nit: I don't think fallthrough is necessary for cases like:
> 
> case XDP_DROP:
> case XDP_PASS:
>     /* do something */
> 
>> +       case XDP_PASS:
>> +               break;
>> +       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;
> 
> hm.. if you move XDP_DROP case to after XDP_ABORTED and do fallthrough
> from XDP_ABORTED, you won't even need to override act and it will just
> handle all the cases, no?
> 
> switch (act) {
> case XDP_PASS:
>     return xdp;
> default:
>     bpf_warn_invalid_xdp_action(act);
>     fallthrough;
> case XDP_ABORTED:
>     trace_xdp_exception(dev, xdp_prog, act);
>     fallthrough;
> case XDP_DROP:
>     xdp_return_buff(xdp);
>     return NULL;
> }
> 
> Wouldn't this be simpler?
> 

Switched it to this which captures your intent with a more traditional
return location.

        act = bpf_prog_run_xdp(xdp_prog, xdp);
        switch (act) {
        case XDP_PASS:
                return xdp;
        case XDP_DROP:
                break;
        default:
                bpf_warn_invalid_xdp_action(act);
                fallthrough;
        case XDP_ABORTED:
                trace_xdp_exception(dev, xdp_prog, act);
                break;
        }

        xdp_return_buff(xdp);
        return NULL;

Re: [PATCH v2 bpf-next 2/5] bpf: Add support to attach bpf program to a devmap entry

[Andrii Nakryiko]

On Thu, May 28, 2020 at 3:40 PM David Ahern <dsahern@gmail.com> wrote:
>
> On 5/28/20 1:01 AM, Andrii Nakryiko wrote:
> >
> > Please cc bpf@vger.kernel.org in the future for patches related to BPF
> > in general.
>
> added to my script
>
> >
> >>  include/linux/bpf.h            |  5 +++
> >>  include/uapi/linux/bpf.h       |  5 +++
> >>  kernel/bpf/devmap.c            | 79 +++++++++++++++++++++++++++++++++-
> >>  net/core/dev.c                 | 18 ++++++++
> >>  tools/include/uapi/linux/bpf.h |  5 +++
> >>  5 files changed, 110 insertions(+), 2 deletions(-)
> >>
> >
> > [...]
> >
> >>
> >> +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;
> >
> > nit: I don't think fallthrough is necessary for cases like:
> >
> > case XDP_DROP:
> > case XDP_PASS:
> >     /* do something */
> >
> >> +       case XDP_PASS:
> >> +               break;
> >> +       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;
> >
> > hm.. if you move XDP_DROP case to after XDP_ABORTED and do fallthrough
> > from XDP_ABORTED, you won't even need to override act and it will just
> > handle all the cases, no?
> >
> > switch (act) {
> > case XDP_PASS:
> >     return xdp;
> > default:
> >     bpf_warn_invalid_xdp_action(act);
> >     fallthrough;
> > case XDP_ABORTED:
> >     trace_xdp_exception(dev, xdp_prog, act);
> >     fallthrough;
> > case XDP_DROP:
> >     xdp_return_buff(xdp);
> >     return NULL;
> > }
> >
> > Wouldn't this be simpler?
> >
>
> Switched it to this which captures your intent with a more traditional
> return location.
>
>         act = bpf_prog_run_xdp(xdp_prog, xdp);
>         switch (act) {
>         case XDP_PASS:
>                 return xdp;
>         case XDP_DROP:
>                 break;
>         default:
>                 bpf_warn_invalid_xdp_action(act);
>                 fallthrough;
>         case XDP_ABORTED:
>                 trace_xdp_exception(dev, xdp_prog, act);
>                 break;
>         }
>
>         xdp_return_buff(xdp);
>         return NULL;

looks good as well, thanks

Re: [PATCH v2 bpf-next 2/5] bpf: Add support to attach bpf program to a devmap entry

[Toke Høiland-Jørgensen]

David Ahern <dsahern@kernel.org> writes:

> From: David Ahern <dsahern@gmail.com>
>
> Add BPF_XDP_DEVMAP attach type for use with programs associated with a
> DEVMAP entry.
>
> Allow DEVMAPs to associate a program with a device entry by adding
> a bpf_prog_fd to 'struct devmap_val'. Values read show the program
> id, so the fd and id are a union.
>
> The program associated with the fd 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
>  > 4-byte values.
>
> Block attach of BPF_XDP_DEVMAP programs to devices.
>
> Signed-off-by: David Ahern <dsahern@gmail.com>
> ---
>  include/linux/bpf.h            |  5 +++
>  include/uapi/linux/bpf.h       |  5 +++
>  kernel/bpf/devmap.c            | 79 +++++++++++++++++++++++++++++++++-
>  net/core/dev.c                 | 18 ++++++++
>  tools/include/uapi/linux/bpf.h |  5 +++
>  5 files changed, 110 insertions(+), 2 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 d27302ecaa9c..2d9927b7a922 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
>  };
>  
> @@ -3628,6 +3629,10 @@ struct xdp_md {
>  /* DEVMAP values */
>  struct devmap_val {
>  	__u32 ifindex;   /* device index */
> +	union {
> +		int   bpf_prog_fd;  /* prog fd on map write */
> +		__u32 bpf_prog_id;  /* prog id on map read */
> +	};
>  };
>  
>  enum sk_action {
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index 069a50113e26..a628585a31e1 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -64,6 +64,7 @@ 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 devmap_val val;
> @@ -219,6 +220,8 @@ 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);
>  			}
> @@ -233,6 +236,8 @@ 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);
>  		}
> @@ -319,6 +324,16 @@ 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 != 4)

nit (since you've gotten rid of the magic sizes everywhere else) how about:

map->value_size != sizeof_field(struct devmap_val, ifindex)

[PATCH v2 bpf-next 3/5] xdp: Add xdp_txq_info to xdp_buff

[David Ahern]

From: David Ahern <dsahern@gmail.com>

Add xdp_txq_info as the Tx counterpart to xdp_rxq_info. At the
moment only the device is added. Other fields (queue_index)
can be added as use cases arise.

From a UAPI perspective, add egress_ifindex to xdp context for
bpf programs to see the Tx device.

Update the verifier to only allow accesses to egress_ifindex by
XDP programs with BPF_XDP_DEVMAP expected attach type.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 include/net/xdp.h              |  5 +++++
 include/uapi/linux/bpf.h       |  2 ++
 kernel/bpf/devmap.c            |  3 +++
 net/core/filter.c              | 17 +++++++++++++++++
 tools/include/uapi/linux/bpf.h |  2 ++
 5 files changed, 29 insertions(+)

diff --git a/include/net/xdp.h b/include/net/xdp.h
index 90f11760bd12..d54022959491 100644
--- a/include/net/xdp.h
+++ b/include/net/xdp.h
@@ -61,12 +61,17 @@ struct xdp_rxq_info {
 	struct xdp_mem_info mem;
 } ____cacheline_aligned; /* perf critical, avoid false-sharing */
 
+struct xdp_txq_info {
+	struct net_device *dev;
+};
+
 struct xdp_buff {
 	void *data;
 	void *data_end;
 	void *data_meta;
 	void *data_hard_start;
 	struct xdp_rxq_info *rxq;
+	struct xdp_txq_info *txq;
 	u32 frame_sz; /* frame size to deduce data_hard_end/reserved tailroom*/
 };
 
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2d9927b7a922..a0ebbbe066b2 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3624,6 +3624,8 @@ struct xdp_md {
 	/* Below access go through struct xdp_rxq_info */
 	__u32 ingress_ifindex; /* rxq->dev->ifindex */
 	__u32 rx_queue_index;  /* rxq->queue_index  */
+
+	__u32 egress_ifindex;  /* txq->dev->ifindex */
 };
 
 /* DEVMAP values */
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index a628585a31e1..73e4a6cd6c2b 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -462,8 +462,11 @@ static struct xdp_buff *dev_map_run_prog(struct net_device *dev,
 					 struct xdp_buff *xdp,
 					 struct bpf_prog *xdp_prog)
 {
+	struct xdp_txq_info txq = { .dev = dev };
 	u32 act;
 
+	xdp->txq = &txq;
+
 	act = bpf_prog_run_xdp(xdp_prog, xdp);
 	switch (act) {
 	case XDP_DROP:
diff --git a/net/core/filter.c b/net/core/filter.c
index a6fc23447f12..2e9dbfd8e60c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7014,6 +7014,13 @@ static bool xdp_is_valid_access(int off, int size,
 				const struct bpf_prog *prog,
 				struct bpf_insn_access_aux *info)
 {
+	if (prog->expected_attach_type != BPF_XDP_DEVMAP) {
+		switch (off) {
+		case offsetof(struct xdp_md, egress_ifindex):
+			return false;
+		}
+	}
+
 	if (type == BPF_WRITE) {
 		if (bpf_prog_is_dev_bound(prog->aux)) {
 			switch (off) {
@@ -7967,6 +7974,16 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type,
 				      offsetof(struct xdp_rxq_info,
 					       queue_index));
 		break;
+	case offsetof(struct xdp_md, egress_ifindex):
+		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_buff, txq),
+				      si->dst_reg, si->src_reg,
+				      offsetof(struct xdp_buff, txq));
+		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct xdp_txq_info, dev),
+				      si->dst_reg, si->dst_reg,
+				      offsetof(struct xdp_txq_info, dev));
+		*insn++ = BPF_LDX_MEM(BPF_W, si->dst_reg, si->dst_reg,
+				      offsetof(struct net_device, ifindex));
+		break;
 	}
 
 	return insn - insn_buf;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 2d9927b7a922..a0ebbbe066b2 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3624,6 +3624,8 @@ struct xdp_md {
 	/* Below access go through struct xdp_rxq_info */
 	__u32 ingress_ifindex; /* rxq->dev->ifindex */
 	__u32 rx_queue_index;  /* rxq->queue_index  */
+
+	__u32 egress_ifindex;  /* txq->dev->ifindex */
 };
 
 /* DEVMAP values */
-- 
2.21.1 (Apple Git-122.3)

[PATCH v2 bpf-next 4/5] libbpf: Add SEC name for xdp programs attached to device map

[David Ahern]

Support SEC("xdp_dm*") as a short cut for loading the program with
type BPF_PROG_TYPE_XDP and expected attach type BPF_XDP_DEVMAP.

Signed-off-by: David Ahern <dsahern@kernel.org>
---
 tools/lib/bpf/libbpf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 5d60de6fd818..493909d5d3d3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -6657,6 +6657,8 @@ static const struct bpf_sec_def section_defs[] = {
 		.expected_attach_type = BPF_TRACE_ITER,
 		.is_attach_btf = true,
 		.attach_fn = attach_iter),
+	BPF_EAPROG_SEC("xdp_dm",		BPF_PROG_TYPE_XDP,
+						BPF_XDP_DEVMAP),
 	BPF_PROG_SEC("xdp",			BPF_PROG_TYPE_XDP),
 	BPF_PROG_SEC("perf_event",		BPF_PROG_TYPE_PERF_EVENT),
 	BPF_PROG_SEC("lwt_in",			BPF_PROG_TYPE_LWT_IN),
-- 
2.21.1 (Apple Git-122.3)

Re: [PATCH v2 bpf-next 4/5] libbpf: Add SEC name for xdp programs attached to device map

[Andrii Nakryiko]

On Wed, May 27, 2020 at 5:17 PM David Ahern <dsahern@kernel.org> wrote:
>
> Support SEC("xdp_dm*") as a short cut for loading the program with
> type BPF_PROG_TYPE_XDP and expected attach type BPF_XDP_DEVMAP.
>
> Signed-off-by: David Ahern <dsahern@kernel.org>
> ---
>  tools/lib/bpf/libbpf.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 5d60de6fd818..493909d5d3d3 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -6657,6 +6657,8 @@ static const struct bpf_sec_def section_defs[] = {
>                 .expected_attach_type = BPF_TRACE_ITER,
>                 .is_attach_btf = true,
>                 .attach_fn = attach_iter),
> +       BPF_EAPROG_SEC("xdp_dm",                BPF_PROG_TYPE_XDP,
> +                                               BPF_XDP_DEVMAP),

naming is hard and subjective, but does "dm" really associate with
DEVMAP to you, rather than "direct message" or "direct memory" or
something along those line? Is there any harm to call this
"xdp_devmap"? It's still short enough, IMO.

>         BPF_PROG_SEC("xdp",                     BPF_PROG_TYPE_XDP),
>         BPF_PROG_SEC("perf_event",              BPF_PROG_TYPE_PERF_EVENT),
>         BPF_PROG_SEC("lwt_in",                  BPF_PROG_TYPE_LWT_IN),
> --
> 2.21.1 (Apple Git-122.3)
>

Re: [PATCH v2 bpf-next 4/5] libbpf: Add SEC name for xdp programs attached to device map

[David Ahern]

On 5/28/20 1:04 AM, Andrii Nakryiko wrote:
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index 5d60de6fd818..493909d5d3d3 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -6657,6 +6657,8 @@ static const struct bpf_sec_def section_defs[] = {
>>                 .expected_attach_type = BPF_TRACE_ITER,
>>                 .is_attach_btf = true,
>>                 .attach_fn = attach_iter),
>> +       BPF_EAPROG_SEC("xdp_dm",                BPF_PROG_TYPE_XDP,
>> +                                               BPF_XDP_DEVMAP),
> 
> naming is hard and subjective, but does "dm" really associate with
> DEVMAP to you, rather than "direct message" or "direct memory" or

Yes it does b/c of the XDP context. Program name lengths being limited
to 15 characters makes me shorten all prefixes to leave some usable
characters for id'ing the program.


> something along those line? Is there any harm to call this
> "xdp_devmap"? It's still short enough, IMO.
> 

but for the SEC name, I switched it to xdp_devmap.

[PATCH v2 bpf-next 5/5] selftest: Add tests for XDP programs in devmap entries

[David Ahern]

Add tests to verify ability to add an XDP program to a
entry in a DEVMAP.

Add negative tests to show DEVMAP programs can not be
attached to devices as a normal XDP program, and accesses
to egress_ifindex require BPF_XDP_DEVMAP attach type.

Signed-off-by: David Ahern <dsahern@kernel.org>
---
 .../bpf/prog_tests/xdp_devmap_attach.c        | 94 +++++++++++++++++++
 .../selftests/bpf/progs/test_xdp_devmap.c     | 19 ++++
 .../selftests/bpf/progs/test_xdp_devmap2.c    | 19 ++++
 .../bpf/progs/test_xdp_with_devmap.c          | 17 ++++
 4 files changed, 149 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_devmap.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_devmap2.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
new file mode 100644
index 000000000000..d81b2b366f39
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <uapi/linux/bpf.h>
+#include <linux/if_link.h>
+#include <test_progs.h>
+
+#define IFINDEX_LO 1
+
+void test_xdp_devmap_attach(void)
+{
+	struct bpf_prog_load_attr attr = {
+		.prog_type = BPF_PROG_TYPE_XDP,
+	};
+	struct bpf_object *obj, *dm_obj = NULL;
+	int err, dm_fd = -1, fd = -1, map_fd;
+	struct bpf_prog_info info = {};
+	struct devmap_val val = {
+		.ifindex = IFINDEX_LO,
+	};
+	__u32 id, len = sizeof(info);
+	__u32 duration = 0, idx = 0;
+
+	attr.file = "./test_xdp_with_devmap.o",
+	err = bpf_prog_load_xattr(&attr, &obj, &fd);
+	if (CHECK(err, "load of xdp program with 8-byte devmap",
+		  "err %d errno %d\n", err, errno))
+		return;
+
+	/* can not attach program with DEVMAPs that allow programs */
+	err = bpf_set_link_xdp_fd(IFINDEX_LO, fd, XDP_FLAGS_SKB_MODE);
+	CHECK(err == 0, "Generic attach of program with 8-byte devmap",
+	      "should have failed\n");
+
+	map_fd = bpf_object__find_map_fd_by_name(obj, "dm_ports");
+	if (CHECK(map_fd < 0, "Lookup dm_ports map",
+		  "err %d errno %d\n", err, errno))
+		goto out_close;
+
+	/*
+	 * basic test - load program to be installed in devmap;
+	 * also verifies access to ingress and egress ifindices.
+	 */
+	attr.expected_attach_type = BPF_XDP_DEVMAP;
+	attr.file = "./test_xdp_devmap.o";
+	err = bpf_prog_load_xattr(&attr, &dm_obj, &dm_fd);
+	if (CHECK(err, "Load of BPF_XDP_DEVMAP program",
+		  "err %d errno %d\n", err, errno))
+		goto out_close;
+
+	err = bpf_obj_get_info_by_fd(dm_fd, &info, &len);
+	if (CHECK_FAIL(err))
+		goto out_close;
+
+	val.bpf_prog_fd = dm_fd;
+	err = bpf_map_update_elem(map_fd, &idx, &val, 0);
+	CHECK(err, "Add program to devmap entry",
+	      "err %d errno %d\n", err, errno);
+
+	err = bpf_map_lookup_elem(map_fd, &id, &val);
+	CHECK(err, "Read devmap entry",
+	      "err %d errno %d\n", err, errno);
+	CHECK(info.id != val.bpf_prog_id, "Expected program id in devmap entry",
+	      "expected %u read %u\n", info.id, val.bpf_prog_id);
+
+	/* can not attach BPF_XDP_DEVMAP program to a device */
+	err = bpf_set_link_xdp_fd(IFINDEX_LO, dm_fd, XDP_FLAGS_SKB_MODE);
+	CHECK(err == 0, "Attach of BPF_XDP_DEVMAP program",
+	      "should have failed\n");
+
+	bpf_object__close(dm_obj);
+
+	/* Load of BPF_XDP_DEVMAP as XDP should fail because of egress index */
+	attr.expected_attach_type = 0;
+	err = bpf_prog_load_xattr(&attr, &dm_obj, &dm_fd);
+	if (CHECK(err == 0,
+		  "Load of XDP program accessing egress ifindex without attach type",
+		  "should have failed\n"))
+		bpf_object__close(dm_obj);
+
+	attr.file = "./xdp_dummy.o";
+	err = bpf_prog_load_xattr(&attr, &dm_obj, &dm_fd);
+	if (CHECK_FAIL(err))
+		goto out_close;
+
+	val.ifindex = 1;
+	val.bpf_prog_fd = dm_fd;
+	err = bpf_map_update_elem(map_fd, &idx, &val, 0);
+	CHECK(err == 0, "Add non-BPF_XDP_DEVMAP program to devmap entry",
+	      "should have failed\n");
+
+	bpf_object__close(dm_obj);
+
+out_close:
+	bpf_object__close(obj);
+}
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_devmap.c b/tools/testing/selftests/bpf/progs/test_xdp_devmap.c
new file mode 100644
index 000000000000..64fc2c3cae01
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_xdp_devmap.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0
+/* program inserted into devmap entry */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+SEC("xdp_devmap_log")
+int xdpdm_devlog(struct xdp_md *ctx)
+{
+	char fmt[] = "devmap redirect: dev %u -> dev %u len %u\n";
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data = (void *)(long)ctx->data;
+	unsigned int len = data_end - data;
+
+	bpf_trace_printk(fmt, sizeof(fmt), ctx->ingress_ifindex, ctx->egress_ifindex, len);
+
+	return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_devmap2.c b/tools/testing/selftests/bpf/progs/test_xdp_devmap2.c
new file mode 100644
index 000000000000..64fc2c3cae01
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_xdp_devmap2.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0
+/* program inserted into devmap entry */
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+SEC("xdp_devmap_log")
+int xdpdm_devlog(struct xdp_md *ctx)
+{
+	char fmt[] = "devmap redirect: dev %u -> dev %u len %u\n";
+	void *data_end = (void *)(long)ctx->data_end;
+	void *data = (void *)(long)ctx->data;
+	unsigned int len = data_end - data;
+
+	bpf_trace_printk(fmt, sizeof(fmt), ctx->ingress_ifindex, ctx->egress_ifindex, len);
+
+	return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c b/tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c
new file mode 100644
index 000000000000..815cd59b4866
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+
+struct bpf_map_def SEC("maps") dm_ports = {
+	.type = BPF_MAP_TYPE_DEVMAP,
+	.key_size = sizeof(__u32),
+	.value_size = sizeof(struct devmap_val),
+	.max_entries = 4,
+};
+
+SEC("xdp_devmap")
+int xdp_with_devmap(struct xdp_md *ctx)
+{
+	return bpf_redirect_map(&dm_ports, 1, 0);
+}
-- 
2.21.1 (Apple Git-122.3)

Re: [PATCH v2 bpf-next 5/5] selftest: Add tests for XDP programs in devmap entries

[Andrii Nakryiko]

On Wed, May 27, 2020 at 5:15 PM David Ahern <dsahern@kernel.org> wrote:
>
> Add tests to verify ability to add an XDP program to a
> entry in a DEVMAP.
>
> Add negative tests to show DEVMAP programs can not be
> attached to devices as a normal XDP program, and accesses
> to egress_ifindex require BPF_XDP_DEVMAP attach type.
>
> Signed-off-by: David Ahern <dsahern@kernel.org>
> ---
>  .../bpf/prog_tests/xdp_devmap_attach.c        | 94 +++++++++++++++++++
>  .../selftests/bpf/progs/test_xdp_devmap.c     | 19 ++++
>  .../selftests/bpf/progs/test_xdp_devmap2.c    | 19 ++++
>  .../bpf/progs/test_xdp_with_devmap.c          | 17 ++++
>  4 files changed, 149 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_devmap.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_devmap2.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
> new file mode 100644
> index 000000000000..d81b2b366f39
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
> @@ -0,0 +1,94 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <uapi/linux/bpf.h>
> +#include <linux/if_link.h>
> +#include <test_progs.h>
> +
> +#define IFINDEX_LO 1
> +
> +void test_xdp_devmap_attach(void)
> +{
> +       struct bpf_prog_load_attr attr = {
> +               .prog_type = BPF_PROG_TYPE_XDP,
> +       };
> +       struct bpf_object *obj, *dm_obj = NULL;
> +       int err, dm_fd = -1, fd = -1, map_fd;
> +       struct bpf_prog_info info = {};
> +       struct devmap_val val = {
> +               .ifindex = IFINDEX_LO,
> +       };
> +       __u32 id, len = sizeof(info);
> +       __u32 duration = 0, idx = 0;
> +
> +       attr.file = "./test_xdp_with_devmap.o",
> +       err = bpf_prog_load_xattr(&attr, &obj, &fd);

please use skeletons instead of loading .o files.

> +       if (CHECK(err, "load of xdp program with 8-byte devmap",
> +                 "err %d errno %d\n", err, errno))
> +               return;
> +

[...]

> diff --git a/tools/testing/selftests/bpf/progs/test_xdp_devmap.c b/tools/testing/selftests/bpf/progs/test_xdp_devmap.c
> new file mode 100644
> index 000000000000..64fc2c3cae01
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_xdp_devmap.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* program inserted into devmap entry */
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +SEC("xdp_devmap_log")
> +int xdpdm_devlog(struct xdp_md *ctx)
> +{
> +       char fmt[] = "devmap redirect: dev %u -> dev %u len %u\n";
> +       void *data_end = (void *)(long)ctx->data_end;
> +       void *data = (void *)(long)ctx->data;
> +       unsigned int len = data_end - data;
> +
> +       bpf_trace_printk(fmt, sizeof(fmt), ctx->ingress_ifindex, ctx->egress_ifindex, len);
> +
> +       return XDP_PASS;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> diff --git a/tools/testing/selftests/bpf/progs/test_xdp_devmap2.c b/tools/testing/selftests/bpf/progs/test_xdp_devmap2.c
> new file mode 100644
> index 000000000000..64fc2c3cae01
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_xdp_devmap2.c
> @@ -0,0 +1,19 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* program inserted into devmap entry */
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +SEC("xdp_devmap_log")
> +int xdpdm_devlog(struct xdp_md *ctx)
> +{
> +       char fmt[] = "devmap redirect: dev %u -> dev %u len %u\n";
> +       void *data_end = (void *)(long)ctx->data_end;
> +       void *data = (void *)(long)ctx->data;
> +       unsigned int len = data_end - data;
> +
> +       bpf_trace_printk(fmt, sizeof(fmt), ctx->ingress_ifindex, ctx->egress_ifindex, len);

instead of just printing ifindexes, why not return them through global
variable and validate in a test?

> +
> +       return XDP_PASS;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> diff --git a/tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c b/tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c
> new file mode 100644
> index 000000000000..815cd59b4866
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c
> @@ -0,0 +1,17 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +struct bpf_map_def SEC("maps") dm_ports = {
> +       .type = BPF_MAP_TYPE_DEVMAP,
> +       .key_size = sizeof(__u32),
> +       .value_size = sizeof(struct devmap_val),
> +       .max_entries = 4,
> +};
> +

This is an old syntax for maps, all the selftests were converted to
BTF-defined maps. Please update.

> +SEC("xdp_devmap")
> +int xdp_with_devmap(struct xdp_md *ctx)
> +{
> +       return bpf_redirect_map(&dm_ports, 1, 0);
> +}
> --
> 2.21.1 (Apple Git-122.3)
>

Re: [PATCH v2 bpf-next 5/5] selftest: Add tests for XDP programs in devmap entries

[Jesper Dangaard Brouer]

On Thu, 28 May 2020 00:08:34 -0700
Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote:

> > diff --git a/tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c b/tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c
> > new file mode 100644
> > index 000000000000..815cd59b4866
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/test_xdp_with_devmap.c
> > @@ -0,0 +1,17 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include <linux/bpf.h>
> > +#include <bpf/bpf_helpers.h>
> > +
> > +struct bpf_map_def SEC("maps") dm_ports = {
> > +       .type = BPF_MAP_TYPE_DEVMAP,
> > +       .key_size = sizeof(__u32),
> > +       .value_size = sizeof(struct devmap_val),
> > +       .max_entries = 4,
> > +};
> > +  
> 
> This is an old syntax for maps, all the selftests were converted to
> BTF-defined maps. Please update.

LOL - The map type BPF_MAP_TYPE_DEVMAP does not support BTF for key and
value, which it what I've been trying to point out... (and yes, I do
have code that makes it work in my tree.).

That said, you should use the new SEC(".maps") definitions, but you
need to use some tricks to avoid a BTF-ID getting generated.  Let me
help you with something that should work:

/* DEVMAP values */
struct devmap_val {
	__u32 ifindex;   /* device index */
};

struct {
	__uint(type, BPF_MAP_TYPE_DEVMAP);
	__uint(key_size, sizeof(u32));
	__uint(value_size, sizeof(struct devmap_val));
	__uint(max_entries, 4);
} dm_ports SEC(".maps");

Notice by setting key_size and value_size, instead of the "__type",
then a BTF-ID will be generated for this map.
Normally with proper BTF it should look like:

struct {
	__uint(type, BPF_MAP_TYPE_DEVMAP);
	__type(key, u32);
	__type(value, struct devmap_val);
	__uint(max_entries, 4);
} dm_ports_with_BTF SEC(".maps");


-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer

Re: [PATCH v2 bpf-next 5/5] selftest: Add tests for XDP programs in devmap entries

[David Ahern]

On 5/28/20 4:25 AM, Jesper Dangaard Brouer wrote:
> That said, you should use the new SEC(".maps") definitions, but you
> need to use some tricks to avoid a BTF-ID getting generated.  Let me
> help you with something that should work:
> 
> /* DEVMAP values */
> struct devmap_val {
> 	__u32 ifindex;   /* device index */
> };
> 
> struct {
> 	__uint(type, BPF_MAP_TYPE_DEVMAP);
> 	__uint(key_size, sizeof(u32));
> 	__uint(value_size, sizeof(struct devmap_val));
> 	__uint(max_entries, 4);
> } dm_ports SEC(".maps");
> 
> Notice by setting key_size and value_size, instead of the "__type",
> then a BTF-ID will be generated for this map.
> Normally with proper BTF it should look like:
> 
> struct {
> 	__uint(type, BPF_MAP_TYPE_DEVMAP);
> 	__type(key, u32);
> 	__type(value, struct devmap_val);
> 	__uint(max_entries, 4);
> } dm_ports_with_BTF SEC(".maps");
> 
> 

Thanks for the tip.

Re: [PATCH v2 bpf-next 5/5] selftest: Add tests for XDP programs in devmap entries

[David Ahern]

On 5/28/20 1:08 AM, Andrii Nakryiko wrote:
>> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
>> new file mode 100644
>> index 000000000000..d81b2b366f39
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c
>> @@ -0,0 +1,94 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +#include <uapi/linux/bpf.h>
>> +#include <linux/if_link.h>
>> +#include <test_progs.h>
>> +
>> +#define IFINDEX_LO 1
>> +
>> +void test_xdp_devmap_attach(void)
>> +{
>> +       struct bpf_prog_load_attr attr = {
>> +               .prog_type = BPF_PROG_TYPE_XDP,
>> +       };
>> +       struct bpf_object *obj, *dm_obj = NULL;
>> +       int err, dm_fd = -1, fd = -1, map_fd;
>> +       struct bpf_prog_info info = {};
>> +       struct devmap_val val = {
>> +               .ifindex = IFINDEX_LO,
>> +       };
>> +       __u32 id, len = sizeof(info);
>> +       __u32 duration = 0, idx = 0;
>> +
>> +       attr.file = "./test_xdp_with_devmap.o",
>> +       err = bpf_prog_load_xattr(&attr, &obj, &fd);
> 
> please use skeletons instead of loading .o files.

I will look into it.

> 
>> +       if (CHECK(err, "load of xdp program with 8-byte devmap",
>> +                 "err %d errno %d\n", err, errno))
>> +               return;
>> +
> 
> [...]
> 

>> diff --git a/tools/testing/selftests/bpf/progs/test_xdp_devmap2.c b/tools/testing/selftests/bpf/progs/test_xdp_devmap2.c
>> new file mode 100644
>> index 000000000000..64fc2c3cae01
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/test_xdp_devmap2.c
>> @@ -0,0 +1,19 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* program inserted into devmap entry */
>> +#include <linux/bpf.h>
>> +#include <bpf/bpf_helpers.h>
>> +
>> +SEC("xdp_devmap_log")
>> +int xdpdm_devlog(struct xdp_md *ctx)
>> +{
>> +       char fmt[] = "devmap redirect: dev %u -> dev %u len %u\n";
>> +       void *data_end = (void *)(long)ctx->data_end;
>> +       void *data = (void *)(long)ctx->data;
>> +       unsigned int len = data_end - data;
>> +
>> +       bpf_trace_printk(fmt, sizeof(fmt), ctx->ingress_ifindex, ctx->egress_ifindex, len);
> 
> instead of just printing ifindexes, why not return them through global
> variable and validate in a test?

The point of this program to access the egress_ifindex with the expected
attached type NOT set to BPF_XDP_DEVMAP to FAIL the verifier checks.