On Tue, 2 Mar 2021 at 18:23, Cong Wang <xiyou.wangcong@xxxxxxxxx> wrote:
>
> > if the function returned a struct proto * like it does at the moment.
> > That way we keep sk->sk_prot manipulation confined to the sockmap code
> > and don't have to copy paste it into every proto.
>
> Well, TCP seems too special to do this, as it could call tcp_update_ulp()
> to update the proto.
I had a quick look, tcp_bpf_update_proto is the only caller of tcp_update_ulp,
which in turn is the only caller of icsk_ulp_ops->update, which in turn is only
implemented as tls_update in tls_main.c. Turns out that tls_update
has another one of these calls:
} else {
/* Pairs with lockless read in sk_clone_lock(). */
WRITE_ONCE(sk->sk_prot, p);
sk->sk_write_space = write_space;
}
Maybe it looks familiar? :o) I think it would be a worthwhile change.
>
> >
> > > diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> > > index 3bddd9dd2da2..13d2af5bb81c 100644
> > > --- a/net/core/sock_map.c
> > > +++ b/net/core/sock_map.c
> > > @@ -184,26 +184,10 @@ static void sock_map_unref(struct sock *sk, void *link_raw)
> > >
> > > static int sock_map_init_proto(struct sock *sk, struct sk_psock *psock)
> > > {
> > > - struct proto *prot;
> > > -
> > > - switch (sk->sk_type) {
> > > - case SOCK_STREAM:
> > > - prot = tcp_bpf_get_proto(sk, psock);
> > > - break;
> > > -
> > > - case SOCK_DGRAM:
> > > - prot = udp_bpf_get_proto(sk, psock);
> > > - break;
> > > -
> > > - default:
> > > + if (!sk->sk_prot->update_proto)
> > > return -EINVAL;
> > > - }
> > > -
> > > - if (IS_ERR(prot))
> > > - return PTR_ERR(prot);
> > > -
> > > - sk_psock_update_proto(sk, psock, prot);
> > > - return 0;
> > > + psock->saved_update_proto = sk->sk_prot->update_proto;
> > > + return sk->sk_prot->update_proto(sk, false);
> >
> > I think reads / writes from sk_prot need READ_ONCE / WRITE_ONCE. We've
> > not been diligent about this so far, but I think it makes sense to be
> > careful in new code.
>
> Hmm, there are many places not using READ_ONCE/WRITE_ONCE,
> for a quick example:
I know! I'll defer to John and Jakub.
--
Lorenz Bauer | Systems Engineer
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