Re: [PATCH v1 net-next 06/13] tcp: Set NULL to sk->sk_prot->h.hashinfo.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From:   Eric Dumazet <edumazet@google.com>
Date:   Fri, 26 Aug 2022 08:40:49 -0700
> On Thu, Aug 25, 2022 at 5:07 PM Kuniyuki Iwashima <kuniyu@amazon.com> wrote:
> >
> > We will soon introduce an optional per-netns ehash.
> >
> > This means we cannot use the global sk->sk_prot->h.hashinfo
> > to fetch a TCP hashinfo.
> >
> > Instead, set NULL to sk->sk_prot->h.hashinfo for TCP and get
> > a proper hashinfo from net->ipv4.tcp_death_row->hashinfo.
> >
> > Note that we need not use sk->sk_prot->h.hashinfo if DCCP is
> > disabled.
> >
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> > ---
> >  include/net/inet_hashtables.h   | 10 ++++++++++
> >  net/ipv4/af_inet.c              |  2 +-
> >  net/ipv4/inet_connection_sock.c |  6 +++---
> >  net/ipv4/inet_hashtables.c      | 14 +++++++-------
> >  net/ipv4/tcp_ipv4.c             |  2 +-
> >  net/ipv6/tcp_ipv6.c             |  2 +-
> >  6 files changed, 23 insertions(+), 13 deletions(-)
> >
> > diff --git a/include/net/inet_hashtables.h b/include/net/inet_hashtables.h
> > index 44a419b9e3d5..2c866112433e 100644
> > --- a/include/net/inet_hashtables.h
> > +++ b/include/net/inet_hashtables.h
> > @@ -170,6 +170,16 @@ struct inet_hashinfo {
> >         struct inet_listen_hashbucket   *lhash2;
> >  };
> >
> > +static inline struct inet_hashinfo *inet_get_hashinfo(const struct sock *sk)
> > +{
> > +#if IS_ENABLED(CONFIG_IP_DCCP)
> > +       return sk->sk_prot->h.hashinfo ? :
> > +               sock_net(sk)->ipv4.tcp_death_row->hashinfo;
> > +#else
> > +       return sock_net(sk)->ipv4.tcp_death_row->hashinfo;
> > +#endif
> > +}
> >
> 
> If the sk_prot->h.hashinfo must disappear, I would rather add a new
> inet->hashinfo field
> 
> return inet_sk(sk)->hashinfo
> 
> Conceptually, the pointer no longer belongs to sk_prot, and not in struct net,
> otherwise you should name this helper   tcp_or_dccp_get_hashinfo() to avoid
> any temptation to use it for other inet protocol.

That makes sense.

To keep the series simple, I'll use tcp_or_dccp_get_hashinfo() in v2 and
post follow-up patch to add inet_sk(sk)->hashinfo, which needs a little
bit more work/test I think.

Thank you!