netdev - Re: [PATCH v2 bpf 2/2] bpf, sockmap: sk_prot needs inuse

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Date:   Mon, 05 Jul 2021 09:28:54 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        John Fastabend <john.fastabend@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 bpf 2/2] bpf, sockmap: sk_prot needs inuse_idx for proc
 stats

Cong Wang wrote:
> On Thu, Jul 1, 2021 at 5:12 PM John Fastabend <john.fastabend@...il.com> wrote:
> >
> > Proc socket stats use sk_prot->inuse_idx value to record inuse sock stats.
> > We currently do not set this correctly from sockmap side. The result is
> > reading sock stats '/proc/net/sockstat' gives incorrect values. The
> > socket counter is incremented correctly, but because we don't set the
> > counter correctly when we replace sk_prot we may omit the decrement.
> >
> > Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
> > Signed-off-by: John Fastabend <john.fastabend@...il.com>
> > ---
> >  net/core/sock_map.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> > index 60decd6420ca..016ea5460f8f 100644
> > --- a/net/core/sock_map.c
> > +++ b/net/core/sock_map.c
> > @@ -222,6 +222,9 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
> >         struct bpf_prog *msg_parser = NULL;
> >         struct sk_psock *psock;
> >         int ret;
> > +#ifdef CONFIG_PROC_FS
> > +       int idx;
> > +#endif
> >
> >         /* Only sockets we can redirect into/from in BPF need to hold
> >          * refs to parser/verdict progs and have their sk_data_ready
> > @@ -293,9 +296,15 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
> >         if (msg_parser)
> >                 psock_set_prog(&psock->progs.msg_parser, msg_parser);
> >
> > +#ifdef CONFIG_PROC_FS
> > +       idx = sk->sk_prot->inuse_idx;
> > +#endif
> >         ret = sock_map_init_proto(sk, psock);
> >         if (ret < 0)
> >                 goto out_drop;
> > +#ifdef CONFIG_PROC_FS
> > +       sk->sk_prot->inuse_idx = idx;
> > +#endif
> 
> I think it is better to put these into sock_map_init_proto()
> so that sock_map_link() does not need to worry about the sk_prot
> details.
> 
> Thanks.

Sure, that is fine.