[PATCH V3] netfilter: netns nf_conntrack: per-netns net.netfilter.nf_conntrack_max sysctl

lvxiafei
2025-04-09T04:26:01Z

From: lvxiafei <lvxiafei@sensetime.com>

Support net.netfilter.nf_conntrack_max settings in
different netns, net.netfilter.nf_conntrack_max is
used to more flexibly limit the ct_count in different
netns. The default value belongs to the global (ancestral)
limit and no implicit limit is inherited from the parent
namespace.

After net.netfilter.nf_conntrack_max is set in different
netns, it is not allowed to be greater than the global
(ancestral) limit net.nf_conntrack_max when working.

Signed-off-by: lvxiafei <lvxiafei@sensetime.com>
---
include/net/netns/conntrack.h | 1 +
net/netfilter/nf_conntrack_core.c | 12 +++++++-----
net/netfilter/nf_conntrack_standalone.c | 5 +++--
3 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
index bae914815aa3..dd31ba205419 100644
--- a/include/net/netns/conntrack.h
+++ b/include/net/netns/conntrack.h
@@ -102,6 +102,7 @@ struct netns_ct {
u8 sysctl_acct;
u8 sysctl_tstamp;
u8 sysctl_checksum;
+ u8 sysctl_max;

struct ip_conntrack_stat __percpu *stat;
struct nf_ct_event_notifier __rcu *nf_conntrack_event_cb;
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 7f8b245e287a..4116c2f2b57f 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1498,7 +1498,7 @@ static bool gc_worker_can_early_drop(const struct nf_conn *ct)

static void gc_worker(struct work_struct *work)
{
- unsigned int i, hashsz, nf_conntrack_max95 = 0;
+ unsigned int i, hashsz;
u32 end_time, start_time = nfct_time_stamp;
struct conntrack_gc_work *gc_work;
unsigned int expired_count = 0;
@@ -1509,8 +1509,6 @@ static void gc_worker(struct work_struct *work)
gc_work = container_of(work, struct conntrack_gc_work, dwork.work);

i = gc_work->next_bucket;
- if (gc_work->early_drop)
- nf_conntrack_max95 = nf_conntrack_max / 100u * 95u;

if (i == 0) {
gc_work->avg_timeout = GC_SCAN_INTERVAL_INIT;
@@ -1538,6 +1536,7 @@ static void gc_worker(struct work_struct *work)
}

hlist_nulls_for_each_entry_rcu(h, n, &ct_hash[i], hnnode) {
+ unsigned int nf_conntrack_max95 = 0;
struct nf_conntrack_net *cnet;
struct net *net;
long expires;
@@ -1567,11 +1566,14 @@ 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;
+ net = nf_ct_net(tmp);
+
+ if (gc_work->early_drop)
+ nf_conntrack_max95 = min(nf_conntrack_max, net->ct.sysctl_max) / 100u * 95u;

if (nf_conntrack_max95 == 0 || gc_worker_skip_ct(tmp))
continue;

- net = nf_ct_net(tmp);
cnet = nf_ct_pernet(net);
if (atomic_read(&cnet->count) < nf_conntrack_max95)
continue;
@@ -1654,7 +1656,7 @@ __nf_conntrack_alloc(struct net *net,
/* We don't want any race condition at early drop stage */
ct_count = atomic_inc_return(&cnet->count);

- if (nf_conntrack_max && unlikely(ct_count > nf_conntrack_max)) {
+ if (net->ct.sysctl_max && unlikely(ct_count > min(nf_conntrack_max, net->ct.sysctl_max))) {
if (!early_drop(net, hash)) {
if (!conntrack_gc_work.early_drop)
conntrack_gc_work.early_drop = true;
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 2f666751c7e7..4a073c4de1b7 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -615,7 +615,7 @@ enum nf_ct_sysctl_index {
static struct ctl_table nf_ct_sysctl_table[] = {
[NF_SYSCTL_CT_MAX] = {
.procname = "nf_conntrack_max",
- .data = &nf_conntrack_max,
+ .data = &init_net.ct.sysctl_max,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
@@ -1063,6 +1063,7 @@ static int nf_conntrack_standalone_init_sysctl(struct net *net)

table[NF_SYSCTL_CT_COUNT].data = &cnet->count;
table[NF_SYSCTL_CT_CHECKSUM].data = &net->ct.sysctl_checksum;
+ table[NF_SYSCTL_CT_MAX].data = &net->ct.sysctl_max;
table[NF_SYSCTL_CT_LOG_INVALID].data = &net->ct.sysctl_log_invalid;
table[NF_SYSCTL_CT_ACCT].data = &net->ct.sysctl_acct;
#ifdef CONFIG_NF_CONNTRACK_EVENTS
@@ -1087,7 +1088,6 @@ static int nf_conntrack_standalone_init_sysctl(struct net *net)

/* Don't allow non-init_net ns to alter global sysctls */
if (!net_eq(&init_net, net)) {
- table[NF_SYSCTL_CT_MAX].mode = 0444;
table[NF_SYSCTL_CT_EXPECT_MAX].mode = 0444;
table[NF_SYSCTL_CT_BUCKETS].mode = 0444;
}
@@ -1139,6 +1139,7 @@ static int nf_conntrack_pernet_init(struct net *net)
int ret;

net->ct.sysctl_checksum = 1;
+ net->ct.sysctl_max = nf_conntrack_max;

ret = nf_conntrack_standalone_init_sysctl(net);
if (ret < 0)
--
2.40.1