[NETFILTER]: connection tracking event notifiers

This adds a notifier chain based event mechanism for ip_conntrack state
changes.  As opposed to the previous implementations in patch-o-matic, we
do no longer need a field in the skb to achieve this.

Thanks to the valuable input from Patrick McHardy and Rusty on the idea
of a per_cpu implementation.
Signed-off-by: NHarald Welte <laforge@netfilter.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/linux/netfilter_ipv4/ip_conntrack.h

@@ -65,6 +65,63 @@ enum ip_conntrack_status {
 
 	/* Both together */
 	IPS_NAT_DONE_MASK = (IPS_DST_NAT_DONE | IPS_SRC_NAT_DONE),
+
+	/* Connection is dying (removed from lists), can not be unset. */
+	IPS_DYING_BIT = 9,
+	IPS_DYING = (1 << IPS_DYING_BIT),
+};
+
+/* Connection tracking event bits */
+enum ip_conntrack_events
+{
+	/* New conntrack */
+	IPCT_NEW_BIT = 0,
+	IPCT_NEW = (1 << IPCT_NEW_BIT),
+
+	/* Expected connection */
+	IPCT_RELATED_BIT = 1,
+	IPCT_RELATED = (1 << IPCT_RELATED_BIT),
+
+	/* Destroyed conntrack */
+	IPCT_DESTROY_BIT = 2,
+	IPCT_DESTROY = (1 << IPCT_DESTROY_BIT),
+
+	/* Timer has been refreshed */
+	IPCT_REFRESH_BIT = 3,
+	IPCT_REFRESH = (1 << IPCT_REFRESH_BIT),
+
+	/* Status has changed */
+	IPCT_STATUS_BIT = 4,
+	IPCT_STATUS = (1 << IPCT_STATUS_BIT),
+
+	/* Update of protocol info */
+	IPCT_PROTOINFO_BIT = 5,
+	IPCT_PROTOINFO = (1 << IPCT_PROTOINFO_BIT),
+
+	/* Volatile protocol info */
+	IPCT_PROTOINFO_VOLATILE_BIT = 6,
+	IPCT_PROTOINFO_VOLATILE = (1 << IPCT_PROTOINFO_VOLATILE_BIT),
+
+	/* New helper for conntrack */
+	IPCT_HELPER_BIT = 7,
+	IPCT_HELPER = (1 << IPCT_HELPER_BIT),
+
+	/* Update of helper info */
+	IPCT_HELPINFO_BIT = 8,
+	IPCT_HELPINFO = (1 << IPCT_HELPINFO_BIT),
+
+	/* Volatile helper info */
+	IPCT_HELPINFO_VOLATILE_BIT = 9,
+	IPCT_HELPINFO_VOLATILE = (1 << IPCT_HELPINFO_VOLATILE_BIT),
+
+	/* NAT info */
+	IPCT_NATINFO_BIT = 10,
+	IPCT_NATINFO = (1 << IPCT_NATINFO_BIT),
+};
+
+enum ip_conntrack_expect_events {
+	IPEXP_NEW_BIT = 0,
+	IPEXP_NEW = (1 << IPEXP_NEW_BIT),
 };
 
 #ifdef __KERNEL__
@@ -280,6 +337,11 @@ static inline int is_confirmed(struct ip_conntrack *ct)
 	return test_bit(IPS_CONFIRMED_BIT, &ct->status);
 }
 
+static inline int is_dying(struct ip_conntrack *ct)
+{
+	return test_bit(IPS_DYING_BIT, &ct->status);
+}
+
 extern unsigned int ip_conntrack_htable_size;
  
 struct ip_conntrack_stat
@@ -303,6 +365,88 @@ struct ip_conntrack_stat
 
 #define CONNTRACK_STAT_INC(count) (__get_cpu_var(ip_conntrack_stat).count++)
 
+#ifdef CONFIG_IP_NF_CONNTRACK_EVENTS
+#include <linux/notifier.h>
+
+struct ip_conntrack_ecache {
+	struct ip_conntrack *ct;
+	unsigned int events;
+};
+DECLARE_PER_CPU(struct ip_conntrack_ecache, ip_conntrack_ecache);
+
+#define CONNTRACK_ECACHE(x)	(__get_cpu_var(ip_conntrack_ecache).x)
+ 
+extern struct notifier_block *ip_conntrack_chain;
+extern struct notifier_block *ip_conntrack_expect_chain;
+
+static inline int ip_conntrack_register_notifier(struct notifier_block *nb)
+{
+	return notifier_chain_register(&ip_conntrack_chain, nb);
+}
+
+static inline int ip_conntrack_unregister_notifier(struct notifier_block *nb)
+{
+	return notifier_chain_unregister(&ip_conntrack_chain, nb);
+}
+
+static inline int 
+ip_conntrack_expect_register_notifier(struct notifier_block *nb)
+{
+	return notifier_chain_register(&ip_conntrack_expect_chain, nb);
+}
+
+static inline int
+ip_conntrack_expect_unregister_notifier(struct notifier_block *nb)
+{
+	return notifier_chain_unregister(&ip_conntrack_expect_chain, nb);
+}
+
+static inline void 
+ip_conntrack_event_cache(enum ip_conntrack_events event,
+			 const struct sk_buff *skb)
+{
+	struct ip_conntrack_ecache *ecache = 
+					&__get_cpu_var(ip_conntrack_ecache);
+
+	if (unlikely((struct ip_conntrack *) skb->nfct != ecache->ct)) {
+		if (net_ratelimit()) {
+			printk(KERN_ERR "ctevent: skb->ct != ecache->ct !!!\n");
+			dump_stack();
+		}
+	}
+	ecache->events |= event;
+}
+
+extern void 
+ip_conntrack_deliver_cached_events_for(const struct ip_conntrack *ct);
+extern void ip_conntrack_event_cache_init(const struct sk_buff *skb);
+
+static inline void ip_conntrack_event(enum ip_conntrack_events event,
+				      struct ip_conntrack *ct)
+{
+	if (is_confirmed(ct) && !is_dying(ct))
+		notifier_call_chain(&ip_conntrack_chain, event, ct);
+}
+
+static inline void 
+ip_conntrack_expect_event(enum ip_conntrack_expect_events event,
+			  struct ip_conntrack_expect *exp)
+{
+	notifier_call_chain(&ip_conntrack_expect_chain, event, exp);
+}
+#else /* CONFIG_IP_NF_CONNTRACK_EVENTS */
+static inline void ip_conntrack_event_cache(enum ip_conntrack_events event, 
+					    const struct sk_buff *skb) {}
+static inline void ip_conntrack_event(enum ip_conntrack_events event, 
+				      struct ip_conntrack *ct) {}
+static inline void ip_conntrack_deliver_cached_events_for(
+						struct ip_conntrack *ct) {}
+static inline void ip_conntrack_event_cache_init(const struct sk_buff *skb) {}
+static inline void 
+ip_conntrack_expect_event(enum ip_conntrack_expect_events event, 
+			  struct ip_conntrack_expect *exp) {}
+#endif /* CONFIG_IP_NF_CONNTRACK_EVENTS */
+
 #ifdef CONFIG_IP_NF_NAT_NEEDED
 static inline int ip_nat_initialized(struct ip_conntrack *conntrack,
 				     enum ip_nat_manip_type manip)

include/linux/netfilter_ipv4/ip_conntrack_core.h

@@ -38,12 +38,21 @@ extern int __ip_conntrack_confirm(struct sk_buff **pskb);
 /* Confirm a connection: returns NF_DROP if packet must be dropped. */
 static inline int ip_conntrack_confirm(struct sk_buff **pskb)
 {
-	if ((*pskb)->nfct
-	    && !is_confirmed((struct ip_conntrack *)(*pskb)->nfct))
-		return __ip_conntrack_confirm(pskb);
-	return NF_ACCEPT;
+	struct ip_conntrack *ct = (struct ip_conntrack *)(*pskb)->nfct;
+	int ret = NF_ACCEPT;
+
+	if (ct && !is_confirmed(ct))
+		ret = __ip_conntrack_confirm(pskb);
+	ip_conntrack_deliver_cached_events_for(ct);
+
+	return ret;
 }
 
+#ifdef CONFIG_IP_NF_CONNTRACK_EVENTS
+struct ip_conntrack_ecache;
+extern void __ip_ct_deliver_cached_events(struct ip_conntrack_ecache *ec);
+#endif
+
 extern struct list_head *ip_conntrack_hash;
 extern struct list_head ip_conntrack_expect_list;
 extern rwlock_t ip_conntrack_lock;

net/ipv4/netfilter/Kconfig

@@ -40,6 +40,16 @@ config IP_NF_CONNTRACK_MARK
 	  of packets, but this mark value is kept in the conntrack session
 	  instead of the individual packets.
 	
+config IP_NF_CONNTRACK_EVENTS
+	bool "Connection tracking events"
+	depends on IP_NF_CONNTRACK
+	help
+	  If this option is enabled, the connection tracking code will
+	  provide a notifier chain that can be used by other kernel code
+	  to get notified about changes in the connection tracking state.
+	  
+	  IF unsure, say `N'.
+
 config IP_NF_CT_PROTO_SCTP
 	tristate  'SCTP protocol connection tracking support (EXPERIMENTAL)'
 	depends on IP_NF_CONNTRACK && EXPERIMENTAL

net/ipv4/netfilter/ip_conntrack_core.c

@@ -37,6 +37,7 @@
 #include <linux/err.h>
 #include <linux/percpu.h>
 #include <linux/moduleparam.h>
+#include <linux/notifier.h>
 
 /* ip_conntrack_lock protects the main hash table, protocol/helper/expected
    registrations, conntrack timers*/
@@ -49,7 +50,7 @@
 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
 #include <linux/netfilter_ipv4/listhelp.h>
 
-#define IP_CONNTRACK_VERSION	"2.1"
+#define IP_CONNTRACK_VERSION	"2.2"
 
 #if 0
 #define DEBUGP printk
@@ -76,6 +77,81 @@ unsigned int ip_ct_log_invalid;
 static LIST_HEAD(unconfirmed);
 static int ip_conntrack_vmalloc;
 
+#ifdef CONFIG_IP_NF_CONNTRACK_EVENTS
+struct notifier_block *ip_conntrack_chain;
+struct notifier_block *ip_conntrack_expect_chain;
+
+DEFINE_PER_CPU(struct ip_conntrack_ecache, ip_conntrack_ecache);
+
+static inline void __deliver_cached_events(struct ip_conntrack_ecache *ecache)
+{
+	if (is_confirmed(ecache->ct) && !is_dying(ecache->ct) && ecache->events)
+		notifier_call_chain(&ip_conntrack_chain, ecache->events,
+				    ecache->ct);
+	ecache->events = 0;
+}
+
+void __ip_ct_deliver_cached_events(struct ip_conntrack_ecache *ecache)
+{
+	__deliver_cached_events(ecache);
+}
+
+/* Deliver all cached events for a particular conntrack. This is called
+ * by code prior to async packet handling or freeing the skb */
+void 
+ip_conntrack_deliver_cached_events_for(const struct ip_conntrack *ct)
+{
+	struct ip_conntrack_ecache *ecache = 
+					&__get_cpu_var(ip_conntrack_ecache);
+
+	if (!ct)
+		return;
+
+	if (ecache->ct == ct) {
+		DEBUGP("ecache: delivering event for %p\n", ct);
+		__deliver_cached_events(ecache);
+	} else {
+		if (net_ratelimit())
+			printk(KERN_WARNING "ecache: want to deliver for %p, "
+				"but cache has %p\n", ct, ecache->ct);
+	}
+
+	/* signalize that events have already been delivered */
+	ecache->ct = NULL;
+}
+
+/* Deliver cached events for old pending events, if current conntrack != old */
+void ip_conntrack_event_cache_init(const struct sk_buff *skb)
+{
+	struct ip_conntrack *ct = (struct ip_conntrack *) skb->nfct;
+	struct ip_conntrack_ecache *ecache = 
+					&__get_cpu_var(ip_conntrack_ecache);
+
+	/* take care of delivering potentially old events */
+	if (ecache->ct != ct) {
+		enum ip_conntrack_info ctinfo;
+		/* we have to check, since at startup the cache is NULL */
+		if (likely(ecache->ct)) {
+			DEBUGP("ecache: entered for different conntrack: "
+			       "ecache->ct=%p, skb->nfct=%p. delivering "
+			       "events\n", ecache->ct, ct);
+			__deliver_cached_events(ecache);
+			ip_conntrack_put(ecache->ct);
+		} else {
+			DEBUGP("ecache: entered for conntrack %p, "
+				"cache was clean before\n", ct);
+		}
+
+		/* initialize for this conntrack/packet */
+		ecache->ct = ip_conntrack_get(skb, &ctinfo);
+		/* ecache->events cleared by __deliver_cached_devents() */
+	} else {
+		DEBUGP("ecache: re-entered for conntrack %p.\n", ct);
+	}
+}
+
+#endif /* CONFIG_IP_NF_CONNTRACK_EVENTS */
+
 DEFINE_PER_CPU(struct ip_conntrack_stat, ip_conntrack_stat);
 
 void 
@@ -223,6 +299,8 @@ destroy_conntrack(struct nf_conntrack *nfct)
 	IP_NF_ASSERT(atomic_read(&nfct->use) == 0);
 	IP_NF_ASSERT(!timer_pending(&ct->timeout));
 
+	set_bit(IPS_DYING_BIT, &ct->status);
+
 	/* To make sure we don't get any weird locking issues here:
 	 * destroy_conntrack() MUST NOT be called with a write lock
 	 * to ip_conntrack_lock!!! -HW */
@@ -261,6 +339,7 @@ static void death_by_timeout(unsigned long ul_conntrack)
 {
 	struct ip_conntrack *ct = (void *)ul_conntrack;
 
+	ip_conntrack_event(IPCT_DESTROY, ct);
 	write_lock_bh(&ip_conntrack_lock);
 	/* Inside lock so preempt is disabled on module removal path.
 	 * Otherwise we can get spurious warnings. */
@@ -374,6 +453,16 @@ __ip_conntrack_confirm(struct sk_buff **pskb)
 		set_bit(IPS_CONFIRMED_BIT, &ct->status);
 		CONNTRACK_STAT_INC(insert);
 		write_unlock_bh(&ip_conntrack_lock);
+		if (ct->helper)
+			ip_conntrack_event_cache(IPCT_HELPER, *pskb);
+#ifdef CONFIG_IP_NF_NAT_NEEDED
+		if (test_bit(IPS_SRC_NAT_DONE_BIT, &ct->status) ||
+		    test_bit(IPS_DST_NAT_DONE_BIT, &ct->status))
+			ip_conntrack_event_cache(IPCT_NATINFO, *pskb);
+#endif
+		ip_conntrack_event_cache(master_ct(ct) ?
+					 IPCT_RELATED : IPCT_NEW, *pskb);
+
 		return NF_ACCEPT;
 	}
 
@@ -607,7 +696,7 @@ unsigned int ip_conntrack_in(unsigned int hooknum,
 	struct ip_conntrack *ct;
 	enum ip_conntrack_info ctinfo;
 	struct ip_conntrack_protocol *proto;
-	int set_reply;
+	int set_reply = 0;
 	int ret;
 
 	/* Previously seen (loopback or untracked)?  Ignore. */
@@ -666,6 +755,8 @@ unsigned int ip_conntrack_in(unsigned int hooknum,
 
 	IP_NF_ASSERT((*pskb)->nfct);
 
+	ip_conntrack_event_cache_init(*pskb);
+
 	ret = proto->packet(ct, *pskb, ctinfo);
 	if (ret < 0) {
 		/* Invalid: inverse of the return code tells
@@ -676,8 +767,8 @@ unsigned int ip_conntrack_in(unsigned int hooknum,
 		return -ret;
 	}
 
-	if (set_reply)
-		set_bit(IPS_SEEN_REPLY_BIT, &ct->status);
+	if (set_reply && !test_and_set_bit(IPS_SEEN_REPLY_BIT, &ct->status))
+		ip_conntrack_event_cache(IPCT_STATUS, *pskb);
 
 	return ret;
 }
@@ -824,6 +915,7 @@ int ip_conntrack_expect_related(struct ip_conntrack_expect *expect)
 		evict_oldest_expect(expect->master);
 
 	ip_conntrack_expect_insert(expect);
+	ip_conntrack_expect_event(IPEXP_NEW, expect);
 	ret = 0;
 out:
 	write_unlock_bh(&ip_conntrack_lock);
@@ -861,8 +953,10 @@ int ip_conntrack_helper_register(struct ip_conntrack_helper *me)
 static inline int unhelp(struct ip_conntrack_tuple_hash *i,
 			 const struct ip_conntrack_helper *me)
 {
-	if (tuplehash_to_ctrack(i)->helper == me)
+	if (tuplehash_to_ctrack(i)->helper == me) {
+ 		ip_conntrack_event(IPCT_HELPER, tuplehash_to_ctrack(i));
 		tuplehash_to_ctrack(i)->helper = NULL;
+	}
 	return 0;
 }
 
@@ -924,6 +1018,7 @@ void ip_ct_refresh_acct(struct ip_conntrack *ct,
 		if (del_timer(&ct->timeout)) {
 			ct->timeout.expires = jiffies + extra_jiffies;
 			add_timer(&ct->timeout);
+			ip_conntrack_event_cache(IPCT_REFRESH, skb);
 		}
 		ct_add_counters(ct, ctinfo, skb);
 		write_unlock_bh(&ip_conntrack_lock);
@@ -1012,6 +1107,23 @@ ip_ct_iterate_cleanup(int (*iter)(struct ip_conntrack *i, void *), void *data)
 
 		ip_conntrack_put(ct);
 	}
+
+#ifdef CONFIG_IP_NF_CONNTRACK_EVENTS
+	{
+		/* we need to deliver all cached events in order to drop
+		 * the reference counts */
+		int cpu;
+		for_each_cpu(cpu) {
+			struct ip_conntrack_ecache *ecache = 
+					&per_cpu(ip_conntrack_ecache, cpu);
+			if (ecache->ct) {
+				__ip_ct_deliver_cached_events(ecache);
+				ip_conntrack_put(ecache->ct);
+				ecache->ct = NULL;
+			}
+		}
+	}
+#endif
 }
 
 /* Fast function for those who don't want to parse /proc (and I don't

net/ipv4/netfilter/ip_conntrack_ftp.c

@@ -262,7 +262,8 @@ static int find_nl_seq(u32 seq, const struct ip_ct_ftp_master *info, int dir)
 }
 
 /* We don't update if it's older than what we have. */
-static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir)
+static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir,
+			  struct sk_buff *skb)
 {
 	unsigned int i, oldest = NUM_SEQ_TO_REMEMBER;
 
@@ -276,10 +277,13 @@ static void update_nl_seq(u32 nl_seq, struct ip_ct_ftp_master *info, int dir)
 			oldest = i;
 	}
 
-	if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER)
+	if (info->seq_aft_nl_num[dir] < NUM_SEQ_TO_REMEMBER) {
 		info->seq_aft_nl[dir][info->seq_aft_nl_num[dir]++] = nl_seq;
-	else if (oldest != NUM_SEQ_TO_REMEMBER)
+		ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
+	} else if (oldest != NUM_SEQ_TO_REMEMBER) {
 		info->seq_aft_nl[dir][oldest] = nl_seq;
+		ip_conntrack_event_cache(IPCT_HELPINFO_VOLATILE, skb);
+	}
 }
 
 static int help(struct sk_buff **pskb,
@@ -439,7 +443,7 @@ static int help(struct sk_buff **pskb,
 	/* Now if this ends in \n, update ftp info.  Seq may have been
 	 * adjusted by NAT code. */
 	if (ends_in_nl)
-		update_nl_seq(seq, ct_ftp_info,dir);
+		update_nl_seq(seq, ct_ftp_info,dir, *pskb);
  out:
 	spin_unlock_bh(&ip_ftp_lock);
 	return ret;

net/ipv4/netfilter/ip_conntrack_proto_icmp.c

@@ -102,6 +102,7 @@ static int icmp_packet(struct ip_conntrack *ct,
 			ct->timeout.function((unsigned long)ct);
 	} else {
 		atomic_inc(&ct->proto.icmp.count);
+		ip_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
 		ip_ct_refresh_acct(ct, ctinfo, skb, ip_ct_icmp_timeout);
 	}
 

net/ipv4/netfilter/ip_conntrack_proto_sctp.c

@@ -404,6 +404,8 @@ static int sctp_packet(struct ip_conntrack *conntrack,
 		}
 
 		conntrack->proto.sctp.state = newconntrack;
+		if (oldsctpstate != newconntrack)
+			ip_conntrack_event_cache(IPCT_PROTOINFO, skb);
 		write_unlock_bh(&sctp_lock);
 	}
 

net/ipv4/netfilter/ip_conntrack_proto_tcp.c

@@ -973,6 +973,10 @@ static int tcp_packet(struct ip_conntrack *conntrack,
 		  ? ip_ct_tcp_timeout_max_retrans : *tcp_timeouts[new_state];
 	write_unlock_bh(&tcp_lock);
 
+	ip_conntrack_event_cache(IPCT_PROTOINFO_VOLATILE, skb);
+	if (new_state != old_state)
+		ip_conntrack_event_cache(IPCT_PROTOINFO, skb);
+
 	if (!test_bit(IPS_SEEN_REPLY_BIT, &conntrack->status)) {
 		/* If only reply is a RST, we can consider ourselves not to
 		   have an established connection: this is a fairly common

net/ipv4/netfilter/ip_conntrack_proto_udp.c

@@ -73,7 +73,8 @@ static int udp_packet(struct ip_conntrack *conntrack,
 		ip_ct_refresh_acct(conntrack, ctinfo, skb, 
 				   ip_ct_udp_timeout_stream);
 		/* Also, more likely to be important, and not a probe */
-		set_bit(IPS_ASSURED_BIT, &conntrack->status);
+		if (!test_and_set_bit(IPS_ASSURED_BIT, &conntrack->status))
+			ip_conntrack_event_cache(IPCT_STATUS, skb);
 	} else
 		ip_ct_refresh_acct(conntrack, ctinfo, skb, ip_ct_udp_timeout);
 

net/ipv4/netfilter/ip_conntrack_standalone.c

@@ -402,6 +402,7 @@ static unsigned int ip_confirm(unsigned int hooknum,
 			       const struct net_device *out,
 			       int (*okfn)(struct sk_buff *))
 {
+	ip_conntrack_event_cache_init(*pskb);
 	/* We've seen it coming out the other side: confirm it */
 	return ip_conntrack_confirm(pskb);
 }
@@ -419,6 +420,7 @@ static unsigned int ip_conntrack_help(unsigned int hooknum,
 	ct = ip_conntrack_get(*pskb, &ctinfo);
 	if (ct && ct->helper) {
 		unsigned int ret;
+		ip_conntrack_event_cache_init(*pskb);
 		ret = ct->helper->help(pskb, ct, ctinfo);
 		if (ret != NF_ACCEPT)
 			return ret;
@@ -889,6 +891,7 @@ static int init_or_cleanup(int init)
 	return ret;
 
  cleanup:
+	synchronize_net();
 #ifdef CONFIG_SYSCTL
  	unregister_sysctl_table(ip_ct_sysctl_header);
  cleanup_localinops:
@@ -971,6 +974,13 @@ void need_ip_conntrack(void)
 {
 }
 
+#ifdef CONFIG_IP_NF_CONNTRACK_EVENTS
+EXPORT_SYMBOL_GPL(ip_conntrack_chain);
+EXPORT_SYMBOL_GPL(ip_conntrack_expect_chain);
+EXPORT_SYMBOL_GPL(ip_conntrack_register_notifier);
+EXPORT_SYMBOL_GPL(ip_conntrack_unregister_notifier);
+EXPORT_PER_CPU_SYMBOL_GPL(ip_conntrack_ecache);
+#endif
 EXPORT_SYMBOL(ip_conntrack_protocol_register);
 EXPORT_SYMBOL(ip_conntrack_protocol_unregister);
 EXPORT_SYMBOL(ip_ct_get_tuple);