Martin Lau wrote:

On Fri, Jan 10, 2020 at 11:50:23AM +0100, Jakub Sitnicki wrote:

quoted

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@cloudflare.com>
---

[...]
 

quoted

+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,

+1 drop it. The normal rcu annotations/splats should catch anything here.

Acked-by: Martin KaFai Lau <redacted>