On Fri, Jan 10, 2020 at 11:50:23AM +0100, Jakub Sitnicki wrote:
> Tooling that populates the SOCKMAP with sockets from user-space needs a way
> to inspect its contents. Returning the struct sock * that SOCKMAP holds to
> user-space is neither safe nor useful. An approach established by
> REUSEPORT_SOCKARRAY is to return a socket cookie (a unique identifier)
> instead.
>
> Since socket cookies are u64 values SOCKMAP needs to support such a value
> size for lookup to be possible. This requires special handling on update,
> though. Attempts to do a lookup on SOCKMAP holding u32 values will be met
> with ENOSPC error.
>
> Signed-off-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
> ---
> net/core/sock_map.c | 31 +++++++++++++++++++++++++++++--
> 1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index d1a91e41ff82..3731191a7d1e 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -10,6 +10,7 @@
> #include <linux/skmsg.h>
> #include <linux/list.h>
> #include <linux/jhash.h>
> +#include <linux/sock_diag.h>
>
> struct bpf_stab {
> struct bpf_map map;
> @@ -31,7 +32,8 @@ static struct bpf_map *sock_map_alloc(union bpf_attr *attr)
> return ERR_PTR(-EPERM);
> if (attr->max_entries == 0 ||
> attr->key_size != 4 ||
> - attr->value_size != 4 ||
> + (attr->value_size != sizeof(u32) &&
> + attr->value_size != sizeof(u64)) ||
> attr->map_flags & ~SOCK_CREATE_FLAG_MASK)
> return ERR_PTR(-EINVAL);
>
> @@ -298,6 +300,23 @@ static void *sock_map_lookup(struct bpf_map *map, void *key)
> return ERR_PTR(-EOPNOTSUPP);
> }
>
> +static void *sock_map_lookup_sys(struct bpf_map *map, void *key)
> +{
> + struct sock *sk;
> +
> + WARN_ON_ONCE(!rcu_read_lock_held());
It seems unnecessary. It is only called by syscall.c which
holds the rcu_read_lock(). Other than that,
Acked-by: Martin KaFai Lau <kafai@xxxxxx>
> +
> + if (map->value_size != sizeof(u64))
> + return ERR_PTR(-ENOSPC);
> +
> + sk = __sock_map_lookup_elem(map, *(u32 *)key);
> + if (!sk)
> + return ERR_PTR(-ENOENT);
> +
> + sock_gen_cookie(sk);
> + return &sk->sk_cookie;
> +}
> +
