Martin Lau wrote:
> 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>
> > ---
[...]
> > +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 <kafai@xxxxxx>
