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, 4 insertions, 42 deletions

diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c
index 2eab1e0400f4..90d396814798 100644
--- a/net/netfilter/ipvs/ip_vs_xmit.c
+++ b/net/netfilter/ipvs/ip_vs_xmit.c
@@ -678,7 +678,6 @@ ip_vs_bypass_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 
 	EnterFunction(10);
 
-	rcu_read_lock();
 	if (__ip_vs_get_out_rt(cp->ipvs, cp->af, skb, NULL, iph->daddr,
 			       IP_VS_RT_MODE_NON_LOCAL, NULL, ipvsh) < 0)
 		goto tx_error;
@@ -689,14 +688,12 @@ ip_vs_bypass_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 	skb->ignore_df = 1;
 
 	ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 0);
-	rcu_read_unlock();
 
 	LeaveFunction(10);
 	return NF_STOLEN;
 
  tx_error:
 	kfree_skb(skb);
-	rcu_read_unlock();
 	LeaveFunction(10);
 	return NF_STOLEN;
 }
@@ -710,7 +707,6 @@ ip_vs_bypass_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 
 	EnterFunction(10);
 
-	rcu_read_lock();
 	if (__ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, NULL,
 				  &iph->daddr, NULL,
 				  ipvsh, 0, IP_VS_RT_MODE_NON_LOCAL) < 0)
@@ -720,14 +716,12 @@ ip_vs_bypass_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 	skb->ignore_df = 1;
 
 	ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 0);
-	rcu_read_unlock();
 
 	LeaveFunction(10);
 	return NF_STOLEN;
 
  tx_error:
 	kfree_skb(skb);
-	rcu_read_unlock();
 	LeaveFunction(10);
 	return NF_STOLEN;
 }
@@ -746,7 +740,6 @@ ip_vs_nat_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 
 	EnterFunction(10);
 
-	rcu_read_lock();
 	/* check if it is a connection of no-client-port */
 	if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT)) {
 		__be16 _pt, *p;
@@ -815,14 +808,12 @@ ip_vs_nat_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 	skb->ignore_df = 1;
 
 	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV4, skb, cp, local);
-	rcu_read_unlock();
 
 	LeaveFunction(10);
 	return rc;
 
   tx_error:
 	kfree_skb(skb);
-	rcu_read_unlock();
 	LeaveFunction(10);
 	return NF_STOLEN;
 }
@@ -837,7 +828,6 @@ ip_vs_nat_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 
 	EnterFunction(10);
 
-	rcu_read_lock();
 	/* check if it is a connection of no-client-port */
 	if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT && !ipvsh->fragoffs)) {
 		__be16 _pt, *p;
@@ -906,7 +896,6 @@ ip_vs_nat_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 	skb->ignore_df = 1;
 
 	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV6, skb, cp, local);
-	rcu_read_unlock();
 
 	LeaveFunction(10);
 	return rc;
@@ -914,7 +903,6 @@ ip_vs_nat_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 tx_error:
 	LeaveFunction(10);
 	kfree_skb(skb);
-	rcu_read_unlock();
 	return NF_STOLEN;
 }
 #endif
@@ -1035,7 +1023,6 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 
 	EnterFunction(10);
 
-	rcu_read_lock();
 	local = __ip_vs_get_out_rt(ipvs, cp->af, skb, cp->dest, cp->daddr.ip,
 				   IP_VS_RT_MODE_LOCAL |
 				   IP_VS_RT_MODE_NON_LOCAL |
@@ -1043,10 +1030,8 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 				   IP_VS_RT_MODE_TUNNEL, &saddr, ipvsh);
 	if (local < 0)
 		goto tx_error;
-	if (local) {
-		rcu_read_unlock();
+	if (local)
 		return ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 1);
-	}
 
 	rt = skb_rtable(skb);
 	tdev = rt->dst.dev;
@@ -1095,7 +1080,6 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 		ip_local_out(net, skb->sk, skb);
 	else if (ret == NF_DROP)
 		kfree_skb(skb);
-	rcu_read_unlock();
 
 	LeaveFunction(10);
 
@@ -1104,7 +1088,6 @@ ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
   tx_error:
 	if (!IS_ERR(skb))
 		kfree_skb(skb);
-	rcu_read_unlock();
 	LeaveFunction(10);
 	return NF_STOLEN;
 }
@@ -1127,7 +1110,6 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 
 	EnterFunction(10);
 
-	rcu_read_lock();
 	local = __ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, cp->dest,
 				      &cp->daddr.in6,
 				      &saddr, ipvsh, 1,
@@ -1136,10 +1118,8 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 				      IP_VS_RT_MODE_TUNNEL);
 	if (local < 0)
 		goto tx_error;
-	if (local) {
-		rcu_read_unlock();
+	if (local)
 		return ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 1);
-	}
 
 	rt = (struct rt6_info *) skb_dst(skb);
 	tdev = rt->dst.dev;
@@ -1185,7 +1165,6 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 		ip6_local_out(cp->ipvs->net, skb->sk, skb);
 	else if (ret == NF_DROP)
 		kfree_skb(skb);
-	rcu_read_unlock();
 
 	LeaveFunction(10);
 
@@ -1194,7 +1173,6 @@ ip_vs_tunnel_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 tx_error:
 	if (!IS_ERR(skb))
 		kfree_skb(skb);
-	rcu_read_unlock();
 	LeaveFunction(10);
 	return NF_STOLEN;
 }
@@ -1213,17 +1191,14 @@ ip_vs_dr_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 
 	EnterFunction(10);
 
-	rcu_read_lock();
 	local = __ip_vs_get_out_rt(cp->ipvs, cp->af, skb, cp->dest, cp->daddr.ip,
 				   IP_VS_RT_MODE_LOCAL |
 				   IP_VS_RT_MODE_NON_LOCAL |
 				   IP_VS_RT_MODE_KNOWN_NH, NULL, ipvsh);
 	if (local < 0)
 		goto tx_error;
-	if (local) {
-		rcu_read_unlock();
+	if (local)
 		return ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 1);
-	}
 
 	ip_send_check(ip_hdr(skb));
 
@@ -1231,14 +1206,12 @@ ip_vs_dr_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 	skb->ignore_df = 1;
 
 	ip_vs_send_or_cont(NFPROTO_IPV4, skb, cp, 0);
-	rcu_read_unlock();
 
 	LeaveFunction(10);
 	return NF_STOLEN;
 
   tx_error:
 	kfree_skb(skb);
-	rcu_read_unlock();
 	LeaveFunction(10);
 	return NF_STOLEN;
 }
@@ -1252,7 +1225,6 @@ ip_vs_dr_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 
 	EnterFunction(10);
 
-	rcu_read_lock();
 	local = __ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, cp->dest,
 				      &cp->daddr.in6,
 				      NULL, ipvsh, 0,
@@ -1261,23 +1233,19 @@ ip_vs_dr_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 				      IP_VS_RT_MODE_KNOWN_NH);
 	if (local < 0)
 		goto tx_error;
-	if (local) {
-		rcu_read_unlock();
+	if (local)
 		return ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 1);
-	}
 
 	/* Another hack: avoid icmp_send in ip_fragment */
 	skb->ignore_df = 1;
 
 	ip_vs_send_or_cont(NFPROTO_IPV6, skb, cp, 0);
-	rcu_read_unlock();
 
 	LeaveFunction(10);
 	return NF_STOLEN;
 
 tx_error:
 	kfree_skb(skb);
-	rcu_read_unlock();
 	LeaveFunction(10);
 	return NF_STOLEN;
 }
@@ -1322,7 +1290,6 @@ ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 	rt_mode = (hooknum != NF_INET_FORWARD) ?
 		  IP_VS_RT_MODE_LOCAL | IP_VS_RT_MODE_NON_LOCAL |
 		  IP_VS_RT_MODE_RDR : IP_VS_RT_MODE_NON_LOCAL;
-	rcu_read_lock();
 	local = __ip_vs_get_out_rt(cp->ipvs, cp->af, skb, cp->dest, cp->daddr.ip, rt_mode,
 				   NULL, iph);
 	if (local < 0)
@@ -1368,12 +1335,10 @@ ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 	skb->ignore_df = 1;
 
 	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV4, skb, cp, local);
-	rcu_read_unlock();
 	goto out;
 
   tx_error:
 	kfree_skb(skb);
-	rcu_read_unlock();
 	rc = NF_STOLEN;
   out:
 	LeaveFunction(10);
@@ -1414,7 +1379,6 @@ ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 	rt_mode = (hooknum != NF_INET_FORWARD) ?
 		  IP_VS_RT_MODE_LOCAL | IP_VS_RT_MODE_NON_LOCAL |
 		  IP_VS_RT_MODE_RDR : IP_VS_RT_MODE_NON_LOCAL;
-	rcu_read_lock();
 	local = __ip_vs_get_out_rt_v6(cp->ipvs, cp->af, skb, cp->dest,
 				      &cp->daddr.in6, NULL, ipvsh, 0, rt_mode);
 	if (local < 0)
@@ -1460,12 +1424,10 @@ ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
 	skb->ignore_df = 1;
 
 	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV6, skb, cp, local);
-	rcu_read_unlock();
 	goto out;
 
 tx_error:
 	kfree_skb(skb);
-	rcu_read_unlock();
 	rc = NF_STOLEN;
 out:
 	LeaveFunction(10);