netfilter: conntrack: avoid zeroing timer

add a __nfct_init_offset annotation member to struct nf_conn to make
it clear which members are covered by the memset when the conntrack
is allocated.

This avoids zeroing timer_list and ct_net; both are already inited
explicitly.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_conntrack.h

@@ -92,12 +92,18 @@ struct nf_conn {
 	/* Have we seen traffic both ways yet? (bitset) */
 	unsigned long status;
 
-	/* If we were expected by an expectation, this will be it */
-	struct nf_conn *master;
-
 	/* Timer function; drops refcnt when it goes off. */
 	struct timer_list timeout;
 
+#ifdef CONFIG_NET_NS
+	struct net *ct_net;
+#endif
+	/* all members below initialized via memset */
+	u8 __nfct_init_offset[0];
+
+	/* If we were expected by an expectation, this will be it */
+	struct nf_conn *master;
+
 #if defined(CONFIG_NF_CONNTRACK_MARK)
 	u_int32_t mark;
 #endif
@@ -108,9 +114,6 @@ struct nf_conn {
 
 	/* Extensions */
 	struct nf_ct_ext *ext;
-#ifdef CONFIG_NET_NS
-	struct net *ct_net;
-#endif
 
 	/* Storage reserved for other modules, must be the last member */
 	union nf_conntrack_proto proto;

net/netfilter/nf_conntrack_core.c

@@ -826,22 +826,19 @@ __nf_conntrack_alloc(struct net *net, u16 zone,
 		atomic_dec(&net->ct.count);
 		return ERR_PTR(-ENOMEM);
 	}
-	/*
-	 * Let ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode.next
-	 * and ct->tuplehash[IP_CT_DIR_REPLY].hnnode.next unchanged.
-	 */
-	memset(&ct->tuplehash[IP_CT_DIR_MAX], 0,
-	       offsetof(struct nf_conn, proto) -
-	       offsetof(struct nf_conn, tuplehash[IP_CT_DIR_MAX]));
 	spin_lock_init(&ct->lock);
 	ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple = *orig;
 	ct->tuplehash[IP_CT_DIR_ORIGINAL].hnnode.pprev = NULL;
 	ct->tuplehash[IP_CT_DIR_REPLY].tuple = *repl;
 	/* save hash for reusing when confirming */
 	*(unsigned long *)(&ct->tuplehash[IP_CT_DIR_REPLY].hnnode.pprev) = hash;
+	ct->status = 0;
 	/* Don't set timer yet: wait for confirmation */
 	setup_timer(&ct->timeout, death_by_timeout, (unsigned long)ct);
 	write_pnet(&ct->ct_net, net);
+	memset(&ct->__nfct_init_offset[0], 0,
+	       offsetof(struct nf_conn, proto) -
+	       offsetof(struct nf_conn, __nfct_init_offset[0]));
 #ifdef CONFIG_NF_CONNTRACK_ZONES
 	if (zone) {
 		struct nf_conntrack_zone *nf_ct_zone;