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

Florian Westphal
2025-04-10T14:17:07Z

Florian Westphal <fw@strlen.de> wrote:
> lvxiafei <xiafei_xupt@163.com> wrote:
> > Florian Westphal <fw@strlen.de> wrote:
> > > I suggest to remove nf_conntrack_max as a global variable,
> > > make net.nf_conntrack_max use init_net.nf_conntrack_max too internally,
> > > so in the init_net both sysctls remain the same.
> >
> > The nf_conntrack_max global variable is a system calculated
> > value and should not be removed.
> > nf_conntrack_max = max_factor * nf_conntrack_htable_size;
>
> Thats the default calculation for the initial sysctl value:
>
> net/netfilter/nf_conntrack_standalone.c: .data = &nf_conntrack_max,
> net/netfilter/nf_conntrack_standalone.c: .data = &nf_conntrack_max,
>
> You can make an initial patch that replaces all occurences of
> nf_conntrack_max with cnet->sysctl_conntrack_max

Something like this:

diff --git a/include/net/netfilter/nf_conntrack.h b/include/net/netfilter/nf_conntrack.h
--- a/include/net/netfilter/nf_conntrack.h
+++ b/include/net/netfilter/nf_conntrack.h
@@ -320,7 +320,6 @@ int nf_conntrack_hash_resize(unsigned int hashsize);
extern struct hlist_nulls_head *nf_conntrack_hash;
extern unsigned int nf_conntrack_htable_size;
extern seqcount_spinlock_t nf_conntrack_generation;
-extern unsigned int nf_conntrack_max;

/* must be called with rcu read lock held */
static inline void
@@ -360,6 +359,11 @@ static inline struct nf_conntrack_net *nf_ct_pernet(const struct net *net)
return net_generic(net, nf_conntrack_net_id);
}

+static inline unsigned int nf_conntrack_max(const struct net *net)
+{
+ return net->ct.sysctl_conntrack_max;
+}
+
int nf_ct_skb_network_trim(struct sk_buff *skb, int family);
int nf_ct_handle_fragments(struct net *net, struct sk_buff *skb,
u16 zone, u8 family, u8 *proto, u16 *mru);
diff --git a/include/net/netns/conntrack.h b/include/net/netns/conntrack.h
--- 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;
+ unsigned int sysctl_conntrack_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..8ae9c22cfcb3 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -202,8 +202,6 @@ static void nf_conntrack_all_unlock(void)
unsigned int nf_conntrack_htable_size __read_mostly;
EXPORT_SYMBOL_GPL(nf_conntrack_htable_size);

-unsigned int nf_conntrack_max __read_mostly;
-EXPORT_SYMBOL_GPL(nf_conntrack_max);
seqcount_spinlock_t nf_conntrack_generation __read_mostly;
static siphash_aligned_key_t nf_conntrack_hash_rnd;

@@ -1509,8 +1507,7 @@ 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;
+ nf_conntrack_max95 = nf_conntrack_max(&init_net) / 100u * 95u;

if (i == 0) {
gc_work->avg_timeout = GC_SCAN_INTERVAL_INIT;
@@ -1648,13 +1645,14 @@ __nf_conntrack_alloc(struct net *net,
gfp_t gfp, u32 hash)
{
struct nf_conntrack_net *cnet = nf_ct_pernet(net);
- unsigned int ct_count;
+ unsigned int ct_max, ct_count;
struct nf_conn *ct;

/* We don't want any race condition at early drop stage */
ct_count = atomic_inc_return(&cnet->count);
+ ct_max = nf_conntrack_max(&init_net);

- if (nf_conntrack_max && unlikely(ct_count > nf_conntrack_max)) {
+ if (ct_max && unlikely(ct_count > ct_max)) {
if (!early_drop(net, hash)) {
if (!conntrack_gc_work.early_drop)
conntrack_gc_work.early_drop = true;
@@ -2650,7 +2648,7 @@ int nf_conntrack_init_start(void)
if (!nf_conntrack_hash)
return -ENOMEM;

- nf_conntrack_max = max_factor * nf_conntrack_htable_size;
+ init_net.ct.sysctl_conntrack_max = max_factor * nf_conntrack_htable_size;

nf_conntrack_cachep = kmem_cache_create("nf_conntrack",
sizeof(struct nf_conn),
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index db23876a6016..f1938204b827 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -2608,7 +2608,7 @@ ctnetlink_stat_ct_fill_info(struct sk_buff *skb, u32 portid, u32 seq, u32 type,
if (nla_put_be32(skb, CTA_STATS_GLOBAL_ENTRIES, htonl(nr_conntracks)))
goto nla_put_failure;

- if (nla_put_be32(skb, CTA_STATS_GLOBAL_MAX_ENTRIES, htonl(nf_conntrack_max)))
+ if (nla_put_be32(skb, CTA_STATS_GLOBAL_MAX_ENTRIES, htonl(nf_conntrack_max(net))))
goto nla_put_failure;

nlmsg_end(skb, nlh);
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 502cf10aab41..8a185dfd3261 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_conntrack_max,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
@@ -944,7 +944,7 @@ static struct ctl_table nf_ct_sysctl_table[] = {
static struct ctl_table nf_ct_netfilter_table[] = {
{
.procname = "nf_conntrack_max",
- .data = &nf_conntrack_max,
+ .data = &init_net.ct.sysctl_conntrack_max,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,