[NETFILTER] nf_conntrack: clean up to reduce size of 'struct nf_conn'

This patch moves all helper related data fields of 'struct nf_conn'
into a separate structure 'struct nf_conn_help'.  This new structure
is only present in conntrack entries for which we actually have a
helper loaded.

Also, this patch cleans up the nf_conntrack 'features' mechanism to
resemble what the original idea was: Just glue the feature-specific
data structures at the end of 'struct nf_conn', and explicitly
re-calculate the pointer to it when needed rather than keeping
pointers around.

Saves 20 bytes per conntrack on my x86_64 box. A non-helped conntrack
is 276 bytes. We still need to save another 20 bytes in order to fit
into to target of 256bytes.

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netfilter/nf_conntrack.h

@@ -67,6 +67,18 @@ do {									\
 
 struct nf_conntrack_helper;
 
+/* nf_conn feature for connections that have a helper */
+struct nf_conn_help {
+	/* Helper. if any */
+	struct nf_conntrack_helper *helper;
+
+	union nf_conntrack_help help;
+
+	/* Current number of expected connections */
+	unsigned int expecting;
+};
+
+
 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
 struct nf_conn
 {
@@ -81,45 +93,32 @@ 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_NF_CT_ACCT
 	/* Accounting Information (same cache line as other written members) */
 	struct ip_conntrack_counter counters[IP_CT_DIR_MAX];
 #endif
-	/* If we were expected by an expectation, this will be it */
-	struct nf_conn *master;
-
-	/* Current number of expected connections */
-	unsigned int expecting;
 
 	/* Unique ID that identifies this conntrack*/
 	unsigned int id;
 
-	/* Helper. if any */
-	struct nf_conntrack_helper *helper;
-
 	/* features - nat, helper, ... used by allocating system */
 	u_int32_t features;
 
-	/* Storage reserved for other modules: */
-
-	union nf_conntrack_proto proto;
-
 #if defined(CONFIG_NF_CONNTRACK_MARK)
 	u_int32_t mark;
 #endif
 
-	/* These members are dynamically allocated. */
-
-	union nf_conntrack_help *help;
+	/* Storage reserved for other modules: */
+	union nf_conntrack_proto proto;
 
-	/* Layer 3 dependent members. (ex: NAT) */
-	union {
-		struct nf_conntrack_ipv4 *ipv4;
-	} l3proto;
-	void *data[0];
+	/* features dynamically at the end: helper, nat (both optional) */
+	char data[0];
 };
 
 struct nf_conntrack_expect
@@ -373,10 +372,23 @@ nf_conntrack_expect_event(enum ip_conntrack_expect_events event,
 #define NF_CT_F_NUM	4
 
 extern int
-nf_conntrack_register_cache(u_int32_t features, const char *name, size_t size,
-			    int (*init_conntrack)(struct nf_conn *, u_int32_t));
+nf_conntrack_register_cache(u_int32_t features, const char *name, size_t size);
 extern void
 nf_conntrack_unregister_cache(u_int32_t features);
 
+/* valid combinations:
+ * basic: nf_conn, nf_conn .. nf_conn_help
+ * nat: nf_conn .. nf_conn_nat, nf_conn .. nf_conn_nat, nf_conn help
+ */
+static inline struct nf_conn_help *nfct_help(const struct nf_conn *ct)
+{
+	unsigned int offset = sizeof(struct nf_conn);
+
+	if (!(ct->features & NF_CT_F_HELP))
+		return NULL;
+
+	return (struct nf_conn_help *) ((void *)ct + offset);
+}
+
 #endif /* __KERNEL__ */
 #endif /* _NF_CONNTRACK_H */

net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c

@@ -141,19 +141,21 @@ static unsigned int ipv4_conntrack_help(unsigned int hooknum,
 {
 	struct nf_conn *ct;
 	enum ip_conntrack_info ctinfo;
+	struct nf_conn_help *help;
 
 	/* This is where we call the helper: as the packet goes out. */
 	ct = nf_ct_get(*pskb, &ctinfo);
-	if (ct && ct->helper) {
-		unsigned int ret;
-		ret = ct->helper->help(pskb,
-				       (*pskb)->nh.raw - (*pskb)->data
-						       + (*pskb)->nh.iph->ihl*4,
-				       ct, ctinfo);
-		if (ret != NF_ACCEPT)
-			return ret;
-	}
-	return NF_ACCEPT;
+	if (!ct)
+		return NF_ACCEPT;
+
+	help = nfct_help(ct);
+	if (!help || !help->helper)
+		return NF_ACCEPT;
+
+	return help->helper->help(pskb,
+			       (*pskb)->nh.raw - (*pskb)->data
+					       + (*pskb)->nh.iph->ihl*4,
+			       ct, ctinfo);
 }
 
 static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,

net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c

@@ -179,31 +179,36 @@ static unsigned int ipv6_confirm(unsigned int hooknum,
 				 int (*okfn)(struct sk_buff *))
 {
 	struct nf_conn *ct;
+	struct nf_conn_help *help;
 	enum ip_conntrack_info ctinfo;
+	unsigned int ret, protoff;
+	unsigned int extoff = (u8*)((*pskb)->nh.ipv6h + 1)
+			      - (*pskb)->data;
+	unsigned char pnum = (*pskb)->nh.ipv6h->nexthdr;
+
 
 	/* This is where we call the helper: as the packet goes out. */
 	ct = nf_ct_get(*pskb, &ctinfo);
-	if (ct && ct->helper) {
-		unsigned int ret, protoff;
-		unsigned int extoff = (u8*)((*pskb)->nh.ipv6h + 1)
-				      - (*pskb)->data;
-		unsigned char pnum = (*pskb)->nh.ipv6h->nexthdr;
-
-		protoff = nf_ct_ipv6_skip_exthdr(*pskb, extoff, &pnum,
-						 (*pskb)->len - extoff);
-		if (protoff < 0 || protoff > (*pskb)->len ||
-		    pnum == NEXTHDR_FRAGMENT) {
-			DEBUGP("proto header not found\n");
-			return NF_ACCEPT;
-		}
+	if (!ct)
+		goto out;
 
-		ret = ct->helper->help(pskb, protoff, ct, ctinfo);
-		if (ret != NF_ACCEPT)
-			return ret;
+	help = nfct_help(ct);
+	if (!help || !help->helper)
+		goto out;
+
+	protoff = nf_ct_ipv6_skip_exthdr(*pskb, extoff, &pnum,
+					 (*pskb)->len - extoff);
+	if (protoff < 0 || protoff > (*pskb)->len ||
+	    pnum == NEXTHDR_FRAGMENT) {
+		DEBUGP("proto header not found\n");
+		return NF_ACCEPT;
 	}
 
+	ret = help->helper->help(pskb, protoff, ct, ctinfo);
+	if (ret != NF_ACCEPT)
+		return ret;
+out:
 	/* We've seen it coming out the other side: confirm it */
-
 	return nf_conntrack_confirm(pskb);
 }