netdev - Re: [PATCH net-next v3] tcp: Dump bound-only sockets in inet

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Date: Thu, 30 Nov 2023 17:17:57 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Guillaume Nault <gnault@...hat.com>
Cc: David Miller <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, 
	David Ahern <dsahern@...nel.org>, Kuniyuki Iwashima <kuniyu@...zon.com>, 
	Michal Kubecek <mkubecek@...e.cz>
Subject: Re: [PATCH net-next v3] tcp: Dump bound-only sockets in inet_diag.

On Thu, Nov 30, 2023 at 4:40 PM Guillaume Nault <gnault@...hat.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@...hat.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[]

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