[NETFILTER 4/8]: Handle NAT module load race

[Patrick McHardy <kaber@trash.net>]

[-- Attachment #1: 04.diff --]
[-- Type: text/x-patch, Size: 3628 bytes --]

[NETFILTER]: Handle NAT module load race

When the NAT module is loaded when connections are already confirmed
it must not change their tuples anymore. This is especially important
with CONFIG_NETFILTER_DEBUG, the netfilter listhelp functions will
refuse to remove an entry from a list when it can not be found on
the list, so when a changed tuple hashes to a new bucket the entry
is kept in the list until and after the conntrack is freed.

Allocate the exact conntrack tuple for NAT for already confirmed
connections or drop them if that fails.

Signed-off-by: Patrick McHardy <kaber@trash.net>

---
commit 92d69138354a34bf06d5429ffa485e3b43282b3f
tree 52ef057d54e84cb1c25ca6ffb0a5864a18196764
parent a5abc2029ac642c6d4d13aedfcb75de752aa7f11
author Patrick McHardy <kaber@trash.net> Sun, 04 Sep 2005 18:23:10 +0200
committer Patrick McHardy <kaber@trash.net> Sun, 04 Sep 2005 18:23:10 +0200

 include/linux/netfilter_ipv4/ip_nat_rule.h |    5 +++++
 net/ipv4/netfilter/ip_nat_rule.c           |   21 +++++++++++++++++++++
 net/ipv4/netfilter/ip_nat_standalone.c     |    8 ++++++--
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/include/linux/netfilter_ipv4/ip_nat_rule.h b/include/linux/netfilter_ipv4/ip_nat_rule.h
--- a/include/linux/netfilter_ipv4/ip_nat_rule.h
+++ b/include/linux/netfilter_ipv4/ip_nat_rule.h
@@ -19,5 +19,10 @@ extern unsigned int
 alloc_null_binding(struct ip_conntrack *conntrack,
 		   struct ip_nat_info *info,
 		   unsigned int hooknum);
+
+extern unsigned int
+alloc_null_binding_confirmed(struct ip_conntrack *conntrack,
+			     struct ip_nat_info *info,
+			     unsigned int hooknum);
 #endif
 #endif /* _IP_NAT_RULE_H */
diff --git a/net/ipv4/netfilter/ip_nat_rule.c b/net/ipv4/netfilter/ip_nat_rule.c
--- a/net/ipv4/netfilter/ip_nat_rule.c
+++ b/net/ipv4/netfilter/ip_nat_rule.c
@@ -255,6 +255,27 @@ alloc_null_binding(struct ip_conntrack *
 	return ip_nat_setup_info(conntrack, &range, hooknum);
 }
 
+unsigned int
+alloc_null_binding_confirmed(struct ip_conntrack *conntrack,
+                             struct ip_nat_info *info,
+                             unsigned int hooknum)
+{
+	u_int32_t ip
+		= (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
+		   ? conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip
+		   : conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);
+	u_int16_t all
+		= (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC
+		   ? conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u.all
+		   : conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.src.u.all);
+	struct ip_nat_range range
+		= { IP_NAT_RANGE_MAP_IPS, ip, ip, { all }, { all } };
+
+	DEBUGP("Allocating NULL binding for confirmed %p (%u.%u.%u.%u)\n",
+	       conntrack, NIPQUAD(ip));
+	return ip_nat_setup_info(conntrack, &range, hooknum);
+}
+
 int ip_nat_rule_find(struct sk_buff **pskb,
 		     unsigned int hooknum,
 		     const struct net_device *in,
diff --git a/net/ipv4/netfilter/ip_nat_standalone.c b/net/ipv4/netfilter/ip_nat_standalone.c
--- a/net/ipv4/netfilter/ip_nat_standalone.c
+++ b/net/ipv4/netfilter/ip_nat_standalone.c
@@ -123,8 +123,12 @@ ip_nat_fn(unsigned int hooknum,
 		if (!ip_nat_initialized(ct, maniptype)) {
 			unsigned int ret;
 
-			/* LOCAL_IN hook doesn't have a chain!  */
-			if (hooknum == NF_IP_LOCAL_IN)
+			if (unlikely(is_confirmed(ct)))
+				/* NAT module was loaded late */
+				ret = alloc_null_binding_confirmed(ct, info,
+				                                   hooknum);
+			else if (hooknum == NF_IP_LOCAL_IN)
+				/* LOCAL_IN hook doesn't have a chain!  */
 				ret = alloc_null_binding(ct, info, hooknum);
 			else
 				ret = ip_nat_rule_find(pskb, hooknum,