[NETFILTER]: nf_conntrack: add nf_copy() to safely copy members in skb

This unifies the codes to copy netfilter related datas. Before copying,
nf_copy() puts original members in destination skb.
Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -1514,9 +1514,22 @@ static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src)
 #endif
 }
 
+static inline void nf_copy(struct sk_buff *dst, const struct sk_buff *src)
+{
+	nf_conntrack_put(dst->nfct);
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+	nf_conntrack_put_reasm(dst->nfct_reasm);
+#endif
+#ifdef CONFIG_BRIDGE_NETFILTER
+	nf_bridge_put(dst->nf_bridge);
+#endif
+	__nf_copy(dst, src);
+}
+
 #else /* CONFIG_NETFILTER */
 static inline void nf_reset(struct sk_buff *skb) {}
 static inline void __nf_copy(struct sk_buff *dst, const struct sk_buff *src) {}
+static inline void nf_copy(struct sk_buff *dst, const struct sk_buff *src) {}
 #endif /* CONFIG_NETFILTER */
 
 #ifdef CONFIG_NETWORK_SECMARK

net/ipv4/ip_output.c

@@ -384,20 +384,9 @@ static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 #ifdef CONFIG_NET_SCHED
 	to->tc_index = from->tc_index;
 #endif
-#ifdef CONFIG_NETFILTER
-	/* Connection association is same as pre-frag packet */
-	nf_conntrack_put(to->nfct);
-	to->nfct = from->nfct;
-	nf_conntrack_get(to->nfct);
-	to->nfctinfo = from->nfctinfo;
+	nf_copy(to, from);
 #if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
 	to->ipvs_property = from->ipvs_property;
-#endif
-#ifdef CONFIG_BRIDGE_NETFILTER
-	nf_bridge_put(to->nf_bridge);
-	to->nf_bridge = from->nf_bridge;
-	nf_bridge_get(to->nf_bridge);
-#endif
 #endif
 	skb_copy_secmark(to, from);
 }

net/ipv6/ip6_output.c

@@ -504,23 +504,7 @@ static void ip6_copy_metadata(struct sk_buff *to, struct sk_buff *from)
 #ifdef CONFIG_NET_SCHED
 	to->tc_index = from->tc_index;
 #endif
-#ifdef CONFIG_NETFILTER
-	/* Connection association is same as pre-frag packet */
-	nf_conntrack_put(to->nfct);
-	to->nfct = from->nfct;
-	nf_conntrack_get(to->nfct);
-	to->nfctinfo = from->nfctinfo;
-#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
-	nf_conntrack_put_reasm(to->nfct_reasm);
-	to->nfct_reasm = from->nfct_reasm;
-	nf_conntrack_get_reasm(to->nfct_reasm);
-#endif
-#ifdef CONFIG_BRIDGE_NETFILTER
-	nf_bridge_put(to->nf_bridge);
-	to->nf_bridge = from->nf_bridge;
-	nf_bridge_get(to->nf_bridge);
-#endif
-#endif
+	nf_copy(to, from);
 	skb_copy_secmark(to, from);
 }