Re: [PATCH net-next v3] tcp: Dump bound-only sockets in inet_diag.

[Guillaume Nault <gnault@redhat.com>]

On Thu, Nov 30, 2023 at 05:17:57PM +0100, Eric Dumazet wrote:
> On Thu, Nov 30, 2023 at 4:40 PM Guillaume Nault <gnault@redhat.com> wrote:
> >
> > Walk the hashinfo->bhash2 table so that inet_diag can dump TCP sockets
> > that are bound but haven't yet called connect() or listen().
> >
> > The code is inspired by the ->lhash2 loop. However there's no manual
> > test of the source port, since this kind of filtering is already
> > handled by inet_diag_bc_sk(). Also, a maximum of 16 sockets are dumped
> > at a time, to avoid running with bh disabled for too long.
> >
> > There's no TCP state for bound but otherwise inactive sockets. Such
> > sockets normally map to TCP_CLOSE. However, "ss -l", which is supposed
> > to only dump listening sockets, actually requests the kernel to dump
> > sockets in either the TCP_LISTEN or TCP_CLOSE states. To avoid dumping
> > bound-only sockets with "ss -l", we therefore need to define a new
> > pseudo-state (TCP_BOUND_INACTIVE) that user space will be able to set
> > explicitly.
> >
> > With an IPv4, an IPv6 and an IPv6-only socket, bound respectively to
> > 40000, 64000, 60000, an updated version of iproute2 could work as
> > follow:
> >
> >   $ ss -t state bound-inactive
> >   Recv-Q   Send-Q     Local Address:Port       Peer Address:Port   Process
> >   0        0                0.0.0.0:40000           0.0.0.0:*
> >   0        0                   [::]:60000              [::]:*
> >   0        0                      *:64000                 *:*
> >
> > Signed-off-by: Guillaume Nault <gnault@redhat.com>
> > ---
> >
> > v3:
> >   * Grab sockets with sock_hold(), instead of refcount_inc_not_zero()
> >     (Kuniyuki Iwashima).
> >   * Use a new TCP pseudo-state (TCP_BOUND_INACTIVE), to dump bound-only
> >     sockets, so that "ss -l" won't print them (Eric Dumazet).
> >
> 
> 
> > +pause_bind_walk:
> > +                       spin_unlock_bh(&ibb->lock);
> > +
> > +                       res = 0;
> > +                       for (idx = 0; idx < accum; idx++) {
> > +                               if (res >= 0) {
> > +                                       res = inet_sk_diag_fill(sk_arr[idx],
> > +                                                               NULL, skb, cb,
> > +                                                               r, NLM_F_MULTI,
> > +                                                               net_admin);
> > +                                       if (res < 0)
> > +                                               num = num_arr[idx];
> > +                               }
> > +                               sock_gen_put(sk_arr[idx]);
> 
> nit: this could be a mere sock_put(), because only full sockets are
> hashed in bhash2[]

Yes, makes sense.
I'll send a v4.

> Reviewed-by: Eric Dumazet <edumazet@google.com>
>