netfilter: xtables: use percpu rule counters

The binary arp/ip/ip6tables ruleset is stored per cpu.

The only reason left as to why we need percpu duplication are the rule
counters embedded into ipt_entry et al -- since each cpu has its own copy
of the rules, all counters can be lockless.

The downside is that the more cpus are supported, the more memory is
required.  Rules are not just duplicated per online cpu but for each
possible cpu, i.e. if maxcpu is 144, then rule is duplicated 144 times,
not for the e.g. 64 cores present.

To save some memory and also improve utilization of shared caches it
would be preferable to only store the rule blob once.

So we first need to separate counters and the rule blob.

Instead of using entry->counters, allocate this percpu and store the
percpu address in entry->counters.pcnt on CONFIG_SMP.

This change makes no sense as-is; it is merely an intermediate step to
remove the percpu duplication of the rule set in a followup patch.

Suggested-by: Eric Dumazet <edumazet@google.com>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Reported-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 26 insertions, 5 deletions

diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index cdd085f..a1190ee 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -367,6 +367,7 @@ ip6t_do_table(struct sk_buff *skb,
 	do {
 		const struct xt_entry_target *t;
 		const struct xt_entry_match *ematch;
+		struct xt_counters *counter;
 
 		IP_NF_ASSERT(e);
 		acpar.thoff = 0;
@@ -384,7 +385,8 @@ ip6t_do_table(struct sk_buff *skb,
 				goto no_match;
 		}
 
-		ADD_COUNTER(e->counters, skb->len, 1);
+		counter = xt_get_this_cpu_counter(&e->counters);
+		ADD_COUNTER(*counter, skb->len, 1);
 
 		t = ip6t_get_target_c(e);
 		IP_NF_ASSERT(t->u.kernel.target);
@@ -679,6 +681,10 @@ find_check_entry(struct ip6t_entry *e, struct net *net, const char *name,
 	if (ret)
 		return ret;
 
+	e->counters.pcnt = xt_percpu_counter_alloc();
+	if (IS_ERR_VALUE(e->counters.pcnt))
+		return -ENOMEM;
+
 	j = 0;
 	mtpar.net	= net;
 	mtpar.table     = name;
@@ -714,6 +720,9 @@ find_check_entry(struct ip6t_entry *e, struct net *net, const char *name,
 			break;
 		cleanup_match(ematch, net);
 	}
+
+	xt_percpu_counter_free(e->counters.pcnt);
+
 	return ret;
 }
 
@@ -797,6 +806,8 @@ static void cleanup_entry(struct ip6t_entry *e, struct net *net)
 	if (par.target->destroy != NULL)
 		par.target->destroy(&par);
 	module_put(par.target->me);
+
+	xt_percpu_counter_free(e->counters.pcnt);
 }
 
 /* Checks and translates the user-supplied table segment (held in
@@ -901,13 +912,15 @@ get_counters(const struct xt_table_info *t,
 
 		i = 0;
 		xt_entry_foreach(iter, t->entries[cpu], t->size) {
+			struct xt_counters *tmp;
 			u64 bcnt, pcnt;
 			unsigned int start;
 
+			tmp = xt_get_per_cpu_counter(&iter->counters, cpu);
 			do {
 				start = read_seqcount_begin(s);
-				bcnt = iter->counters.bcnt;
-				pcnt = iter->counters.pcnt;
+				bcnt = tmp->bcnt;
+				pcnt = tmp->pcnt;
 			} while (read_seqcount_retry(s, start));
 
 			ADD_COUNTER(counters[i], bcnt, pcnt);
@@ -1374,7 +1387,6 @@ do_add_counters(struct net *net, const void __user *user, unsigned int len,
 		goto free;
 	}
 
-
 	local_bh_disable();
 	private = t->private;
 	if (private->number != num_counters) {
@@ -1388,7 +1400,10 @@ do_add_counters(struct net *net, const void __user *user, unsigned int len,
 	addend = xt_write_recseq_begin();
 	loc_cpu_entry = private->entries[curcpu];
 	xt_entry_foreach(iter, loc_cpu_entry, private->size) {
-		ADD_COUNTER(iter->counters, paddc[i].bcnt, paddc[i].pcnt);
+		struct xt_counters *tmp;
+
+		tmp = xt_get_this_cpu_counter(&iter->counters);
+		ADD_COUNTER(*tmp, paddc[i].bcnt, paddc[i].pcnt);
 		++i;
 	}
 	xt_write_recseq_end(addend);
@@ -1621,6 +1636,9 @@ static int compat_check_entry(struct ip6t_entry *e, struct net *net,
 	struct xt_mtchk_param mtpar;
 	struct xt_entry_match *ematch;
 
+	e->counters.pcnt = xt_percpu_counter_alloc();
+	if (IS_ERR_VALUE(e->counters.pcnt))
+		return -ENOMEM;
 	j = 0;
 	mtpar.net	= net;
 	mtpar.table     = name;
@@ -1645,6 +1663,9 @@ static int compat_check_entry(struct ip6t_entry *e, struct net *net,
 			break;
 		cleanup_match(ematch, net);
 	}
+
+	xt_percpu_counter_free(e->counters.pcnt);
+
 	return ret;
 }