Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx> wrote:
> After commit b87a2f9199ea ("netfilter: conntrack: add gc worker to remove
> timed-out entries"), netlink conntrack deletion events may be sent with a
> huge delay (5 minutes).
>
> There is two ways to evict conntrack:
> - during a conntrack lookup;
> - during a conntrack dump.
> Let's do a full scan of conntrack entries after a period of inactivity
> (no conntrack lookup).
>
> CC: Florian Westphal <fw@xxxxxxxxx>
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
> ---
>
> Here is another proposal to try to fix the problem.
> Comments are welcomed,
> Nicolas
Hmm, I don't think its good idea in practice.
If goal is to avoid starving arbitrary 'dead' ct for too long,
then simple ping will defeat the logic here, because...
> net/netfilter/nf_conntrack_core.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> index ba6a1d421222..3dbb27bd9582 100644
> --- a/net/netfilter/nf_conntrack_core.c
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -87,6 +87,7 @@ static __read_mostly bool nf_conntrack_locks_all;
> #define GC_MAX_BUCKETS 8192u
> #define GC_INTERVAL (5 * HZ)
> #define GC_MAX_EVICTS 256u
> +static bool gc_full_scan = true;
>
> static struct conntrack_gc_work conntrack_gc_work;
>
> @@ -511,6 +512,7 @@ ____nf_conntrack_find(struct net *net, const struct nf_conntrack_zone *zone,
> unsigned int bucket, hsize;
>
> begin:
> + gc_full_scan = false;
... we do periodic lookup (but always in same slot), so no full scan is
triggered.
If you think its useful, consider sending patch that rescheds worker
instantly in case budget expired, otherwise I will do this later this
week.
[ I am aware doing instant restart might be too late, but at least we
would then reap more entries once we stumble upon large number of
expired ones ].
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