[PATCH 5.19 256/717] netfilter: conntrack: fix the gc rescheduling delay

Greg Kroah-Hartman
2022-10-22T07:55:03Z

From: Antoine Tenart <atenart@kernel.org>

[ Upstream commit 95eabdd207024312876d0ebed90b4c977e050e85 ]

Commit 2cfadb761d3d ("netfilter: conntrack: revisit gc autotuning")
changed the eviction rescheduling to the use average expiry of scanned
entries (within 1-60s) by doing:

for (...) {
expires = clamp(nf_ct_expires(tmp), ...);
next_run += expires;
next_run /= 2;
}

The issue is the above will make the average ('next_run' here) more
dependent on the last expiration values than the firsts (for sets > 2).
Depending on the expiration values used to compute the average, the
result can be quite different than what's expected. To fix this we can
do the following:

for (...) {
expires = clamp(nf_ct_expires(tmp), ...);
next_run += (expires - next_run) / ++count;
}

Fixes: 2cfadb761d3d ("netfilter: conntrack: revisit gc autotuning")
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: Antoine Tenart <atenart@kernel.org>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nf_conntrack_core.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 369aeabb94fe..6fdbffc85222 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -67,6 +67,7 @@ struct conntrack_gc_work {
struct delayed_work dwork;
u32 next_bucket;
u32 avg_timeout;
+ u32 count;
u32 start_time;
bool exiting;
bool early_drop;
@@ -1468,6 +1469,7 @@ static void gc_worker(struct work_struct *work)
unsigned int expired_count = 0;
unsigned long next_run;
s32 delta_time;
+ long count;

gc_work = container_of(work, struct conntrack_gc_work, dwork.work);

@@ -1477,10 +1479,12 @@ static void gc_worker(struct work_struct *work)

if (i == 0) {
gc_work->avg_timeout = GC_SCAN_INTERVAL_INIT;
+ gc_work->count = 1;
gc_work->start_time = start_time;
}

next_run = gc_work->avg_timeout;
+ count = gc_work->count;

end_time = start_time + GC_SCAN_MAX_DURATION;

@@ -1500,8 +1504,8 @@ static void gc_worker(struct work_struct *work)

hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[i], hnnode) {
struct nf_conntrack_net *cnet;
- unsigned long expires;
struct net *net;
+ long expires;

tmp = nf_ct_tuplehash_to_ctrack(h);

@@ -1515,6 +1519,7 @@ static void gc_worker(struct work_struct *work)

gc_work->next_bucket = i;
gc_work->avg_timeout = next_run;
+ gc_work->count = count;

delta_time = nfct_time_stamp - gc_work->start_time;

@@ -1530,8 +1535,8 @@ static void gc_worker(struct work_struct *work)
}

expires = clamp(nf_ct_expires(tmp), GC_SCAN_INTERVAL_MIN, GC_SCAN_INTERVAL_CLAMP);
+ expires = (expires - (long)next_run) / ++count;
next_run += expires;
- next_run /= 2u;

if (nf_conntrack_max95 == 0 || gc_worker_skip_ct(tmp))
continue;
@@ -1572,6 +1577,7 @@ static void gc_worker(struct work_struct *work)
delta_time = nfct_time_stamp - end_time;
if (delta_time > 0 && i < hashsz) {
gc_work->avg_timeout = next_run;
+ gc_work->count = count;
gc_work->next_bucket = i;
next_run = 0;
goto early_exit;
--
2.35.1