[PATCH nf] netfilter: nf_conntrack: do not skip entries in /proc/net/nf_conntrack

[PATCH nf] netfilter: nf_conntrack: do not skip entries in /proc/net/nf_conntrack

[Eric Dumazet]

ct_seq_show() has an opportunistic garbage collector :

if (nf_ct_should_gc(ct)) {
    nf_ct_kill(ct);
    goto release;
}

So if one nf_conn is killed there, next time ct_get_next() runs,
we skip the following item in the bucket, even if it should have
been displayed if gc did not take place.

We can decrement st->skip_elems to tell ct_get_next() one of the items
was removed from the chain.

Fixes: 58e207e4983d ("netfilter: evict stale entries when user reads /proc/net/nf_conntrack")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/netfilter/nf_conntrack_standalone.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 1f14ef0436c65fccc8e64956a105d5473e21b55e..708b79380f047f32aa8e6047c52c807b4019f2b9 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -317,6 +317,9 @@ static int ct_seq_show(struct seq_file *s, void *v)
 	smp_acquire__after_ctrl_dep();
 
 	if (nf_ct_should_gc(ct)) {
+		struct ct_iter_state *st = s->private;
+
+		st->skip_elems--;
 		nf_ct_kill(ct);
 		goto release;
 	}
-- 
2.51.0.534.gc79095c0ca-goog

Re: [PATCH nf] netfilter: nf_conntrack: do not skip entries in /proc/net/nf_conntrack

[Florian Westphal]

Eric Dumazet <edumazet@google.com> wrote:
> diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
> index 1f14ef0436c65fccc8e64956a105d5473e21b55e..708b79380f047f32aa8e6047c52c807b4019f2b9 100644
> --- a/net/netfilter/nf_conntrack_standalone.c
> +++ b/net/netfilter/nf_conntrack_standalone.c
> @@ -317,6 +317,9 @@ static int ct_seq_show(struct seq_file *s, void *v)
>  	smp_acquire__after_ctrl_dep();
>  
>  	if (nf_ct_should_gc(ct)) {
> +		struct ct_iter_state *st = s->private;
> +
> +		st->skip_elems--;

I'll route this via nf-next, I don't think there is
a need to add it to nf this close to release.

Thanks Eric!