On Fri, Mar 5, 2021 at 4:27 PM John Fastabend <john.fastabend@xxxxxxxxx> wrote:
>
> Cong Wang wrote:
> > On Tue, Mar 2, 2021 at 10:23 AM Cong Wang <xiyou.wangcong@xxxxxxxxx> wrote:
> > >
> > > On Tue, Mar 2, 2021 at 8:22 AM Lorenz Bauer <lmb@xxxxxxxxxxxxxx> wrote:
> > > >
> > > > On Tue, 2 Mar 2021 at 02:37, Cong Wang <xiyou.wangcong@xxxxxxxxx> wrote:
> > > >
> > > > ...
> > > > > static inline void sk_psock_restore_proto(struct sock *sk,
> > > > > struct sk_psock *psock)
> > > > > {
> > > > > sk->sk_prot->unhash = psock->saved_unhash;
> > > >
> > > > Not related to your patch set, but why do an extra restore of
> > > > sk_prot->unhash here? At this point sk->sk_prot is one of our tcp_bpf
> > > > / udp_bpf protos, so overwriting that seems wrong?
>
> "extra"? restore_proto should only be called when the psock ref count
> is zero and we need to transition back to the original socks proto
> handlers. To trigger this we can simply delete a sock from the map.
> In the case where we are deleting the psock overwriting the tcp_bpf
> protos is exactly what we want.?
Why do you want to overwrite tcp_bpf_prots->unhash? Overwriting
tcp_bpf_prots is correct, but overwriting tcp_bpf_prots->unhash is not.
Because once you overwrite it, the next time you use it to replace
sk->sk_prot, it would be a different one rather than sock_map_unhash():
// tcp_bpf_prots->unhash == sock_map_unhash
sk_psock_restore_proto();
// Now tcp_bpf_prots->unhash is inet_unhash
...
sk_psock_update_proto();
// sk->sk_proto is now tcp_bpf_prots again,
// so its ->unhash now is inet_unhash
// but it should be sock_map_unhash here
Thanks.
