[PATCH RFC bpf-next 1/4] bpf: Handle 8-byte values in DEVMAP and DEVMAP_HASH

[David Ahern]

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.

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
@@ -472,18 +483,15 @@ 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)
@@ -552,15 +560,18 @@ static struct bpf_dtab_netdev 
*__dev_map_alloc_node(struct net *net,
                return ERR_PTR(-ENOMEM);
 
        dev->dev = dev_get_by_index(net, ifindex);
-       if (!dev->dev) {
-               kfree(dev);
-               return ERR_PTR(-EINVAL);
-       }
+       if (!dev->dev)
+               goto err_out;
 
        dev->idx = idx;
        dev->dtab = dtab;
 
+       dev->val.ifindex = ifindex;
+
        return dev;
+err_out:
+       kfree(dev);
+       return ERR_PTR(-EINVAL);
 }
 
 static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
@@ -568,8 +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;
-- 
2.21.1 (Apple Git-122.3)