netfilter: Remove duplicated rcu_read_lock.

This patch removes duplicate rcu_read_lock().

1. IPVS part:

According to Julian Anastasov's mention, contexts of ipvs are described
at: http://marc.info/?l=netfilter-devel&m=149562884514072&w=2, in summary:

 - packet RX/TX: does not need locks because packets come from hooks.
 - sync msg RX: backup server uses RCU locks while registering new
   connections.
 - ip_vs_ctl.c: configuration get/set, RCU locks needed.
 - xt_ipvs.c: It is a netfilter match, running from hook context.

As result, rcu_read_lock and rcu_read_unlock can be removed from:

 - ip_vs_core.c: all
 - ip_vs_ctl.c:
   - only from ip_vs_has_real_service
 - ip_vs_ftp.c: all
 - ip_vs_proto_sctp.c: all
 - ip_vs_proto_tcp.c: all
 - ip_vs_proto_udp.c: all
 - ip_vs_xmit.c: all (contains only packet processing)

2. Netfilter part:

There are three types of functions that are guaranteed the rcu_read_lock().
First, as result, functions are only called by nf_hook():

 - nf_conntrack_broadcast_help(), pptp_expectfn(), set_expected_rtp_rtcp().
 - tcpmss_reverse_mtu(), tproxy_laddr4(), tproxy_laddr6().
 - match_lookup_rt6(), check_hlist(), hashlimit_mt_common().
 - xt_osf_match_packet().

Second, functions that caller already held the rcu_read_lock().
 - destroy_conntrack(), ctnetlink_conntrack_event().
 - ctnl_timeout_find_get(), nfqnl_nf_hook_drop().

Third, functions that are mixed with type1 and type2.

These functions are called by nf_hook() also these are called by
ordinary functions that already held the rcu_read_lock():

 - __ctnetlink_glue_build(), ctnetlink_expect_event().
 - ctnetlink_proto_size().

Applied files are below:

- nf_conntrack_broadcast.c, nf_conntrack_core.c, nf_conntrack_netlink.c.
- nf_conntrack_pptp.c, nf_conntrack_sip.c, nfnetlink_cttimeout.c.
- nfnetlink_queue.c, xt_TCPMSS.c, xt_TPROXY.c, xt_addrtype.c.
- xt_connlimit.c, xt_hashlimit.c, xt_osf.c

Detailed calltrace can be found at:
http://marc.info/?l=netfilter-devel&m=149667610710350&w=2

Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 0 insertions, 12 deletions

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 7999e70c3bfb..4dba71de4de7 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -539,13 +539,11 @@ static inline size_t ctnetlink_proto_size(const struct nf_conn *ct)
 	struct nf_conntrack_l4proto *l4proto;
 	size_t len = 0;
 
-	rcu_read_lock();
 	l3proto = __nf_ct_l3proto_find(nf_ct_l3num(ct));
 	len += l3proto->nla_size;
 
 	l4proto = __nf_ct_l4proto_find(nf_ct_l3num(ct), nf_ct_protonum(ct));
 	len += l4proto->nla_size;
-	rcu_read_unlock();
 
 	return len;
 }
@@ -664,7 +662,6 @@ ctnetlink_conntrack_event(unsigned int events, struct nf_ct_event *item)
 	nfmsg->version	= NFNETLINK_V0;
 	nfmsg->res_id	= 0;
 
-	rcu_read_lock();
 	zone = nf_ct_zone(ct);
 
 	nest_parms = nla_nest_start(skb, CTA_TUPLE_ORIG | NLA_F_NESTED);
@@ -736,8 +733,6 @@ ctnetlink_conntrack_event(unsigned int events, struct nf_ct_event *item)
 	    && ctnetlink_dump_mark(skb, ct) < 0)
 		goto nla_put_failure;
 #endif
-	rcu_read_unlock();
-
 	nlmsg_end(skb, nlh);
 	err = nfnetlink_send(skb, net, item->portid, group, item->report,
 			     GFP_ATOMIC);
@@ -747,7 +742,6 @@ ctnetlink_conntrack_event(unsigned int events, struct nf_ct_event *item)
 	return 0;
 
 nla_put_failure:
-	rcu_read_unlock();
 	nlmsg_cancel(skb, nlh);
 nlmsg_failure:
 	kfree_skb(skb);
@@ -2213,7 +2207,6 @@ static int __ctnetlink_glue_build(struct sk_buff *skb, struct nf_conn *ct)
 	const struct nf_conntrack_zone *zone;
 	struct nlattr *nest_parms;
 
-	rcu_read_lock();
 	zone = nf_ct_zone(ct);
 
 	nest_parms = nla_nest_start(skb, CTA_TUPLE_ORIG | NLA_F_NESTED);
@@ -2272,11 +2265,9 @@ static int __ctnetlink_glue_build(struct sk_buff *skb, struct nf_conn *ct)
 #endif
 	if (ctnetlink_dump_labels(skb, ct) < 0)
 		goto nla_put_failure;
-	rcu_read_unlock();
 	return 0;
 
 nla_put_failure:
-	rcu_read_unlock();
 	return -ENOSPC;
 }
 
@@ -2661,17 +2652,14 @@ ctnetlink_expect_event(unsigned int events, struct nf_exp_event *item)
 	nfmsg->version	    = NFNETLINK_V0;
 	nfmsg->res_id	    = 0;
 
-	rcu_read_lock();
 	if (ctnetlink_exp_dump_expect(skb, exp) < 0)
 		goto nla_put_failure;
-	rcu_read_unlock();
 
 	nlmsg_end(skb, nlh);
 	nfnetlink_send(skb, net, item->portid, group, item->report, GFP_ATOMIC);
 	return 0;
 
 nla_put_failure:
-	rcu_read_unlock();
 	nlmsg_cancel(skb, nlh);
 nlmsg_failure:
 	kfree_skb(skb);