netdev - [PATCH] netfilter: remove duplicate code

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Message-Id: <20210807062106.2563-1-l4stpr0gr4m@gmail.com>
Date:   Sat,  7 Aug 2021 15:21:06 +0900
From:   Kangmin Park <l4stpr0gr4m@...il.com>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] netfilter: remove duplicate code

nf_nat_ipv4_fn() and nf_nat_ipv6_fn() call nf_nat_inet_fn().
Those two functions are already contains routine that gets nf_conn
object and checks the untrackable situation.
So, the following code is duplicated.

```
ct = nf_ct_get(skb, &ctinfo);
if (!ct)
        return NF_ACCEPT;
```

Therefore, define a function __nf_nat_inet_fn() that has the same
contents as the nf_nat_inet_fn() except for routine gets and checks
the nf_conn object.
Then, separate the nf_nat_inet_fn() into a routine that gets a
nf_conn object and a routine that calls the __nf_nat_inet_fn().

Signed-off-by: Kangmin Park <l4stpr0gr4m@...il.com>
---
 include/net/netfilter/nf_nat.h |  5 +++++
 net/netfilter/nf_nat_core.c    | 37 ++++++++++++++++++++++------------
 net/netfilter/nf_nat_proto.c   |  4 ++--
 3 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/include/net/netfilter/nf_nat.h b/include/net/netfilter/nf_nat.h
index 987111ae5240..a66f617c5054 100644
--- a/include/net/netfilter/nf_nat.h
+++ b/include/net/netfilter/nf_nat.h
@@ -100,6 +100,11 @@ void nf_nat_ipv6_unregister_fn(struct net *net, const struct nf_hook_ops *ops);
 int nf_nat_inet_register_fn(struct net *net, const struct nf_hook_ops *ops);
 void nf_nat_inet_unregister_fn(struct net *net, const struct nf_hook_ops *ops);
 
+unsigned int
+__nf_nat_inet_fn(void *priv, struct sk_buff *skb,
+		 const struct nf_hook_state *state, struct nf_conn *ct,
+		 enum ip_conntrack_info ctinfo);
+
 unsigned int
 nf_nat_inet_fn(void *priv, struct sk_buff *skb,
 	       const struct nf_hook_state *state);
diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 7de595ead06a..98ebba2c0f6d 100644
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -682,25 +682,15 @@ unsigned int nf_nat_packet(struct nf_conn *ct,
 }
 EXPORT_SYMBOL_GPL(nf_nat_packet);
 
 unsigned int
-nf_nat_inet_fn(void *priv, struct sk_buff *skb,
-	       const struct nf_hook_state *state)
+__nf_nat_inet_fn(void *priv, struct sk_buff *skb,
+		 const struct nf_hook_state *state, struct nf_conn *ct,
+		 enum ip_conntrack_info ctinfo)
 {
-	struct nf_conn *ct;
-	enum ip_conntrack_info ctinfo;
 	struct nf_conn_nat *nat;
 	/* maniptype == SRC for postrouting. */
 	enum nf_nat_manip_type maniptype = HOOK2MANIP(state->hook);
 
-	ct = nf_ct_get(skb, &ctinfo);
-	/* Can't track?  It's not due to stress, or conntrack would
-	 * have dropped it.  Hence it's the user's responsibilty to
-	 * packet filter it out, or implement conntrack/NAT for that
-	 * protocol. 8) --RR
-	 */
-	if (!ct)
-		return NF_ACCEPT;
-
 	nat = nfct_nat(ct);
 
 	switch (ctinfo) {
@@ -755,6 +745,26 @@ nf_nat_inet_fn(void *priv, struct sk_buff *skb,
 	nf_ct_kill_acct(ct, ctinfo, skb);
 	return NF_DROP;
 }
+EXPORT_SYMBOL_GPL(__nf_nat_inet_fn);
+
+unsigned int
+nf_nat_inet_fn(void *priv, struct sk_buff *skb,
+	       const struct nf_hook_state *state)
+{
+	struct nf_conn *ct;
+	enum ip_conntrack_info ctinfo;
+
+	ct = nf_ct_get(skb, &ctinfo);
+	/* Can't track?  It's not due to stress, or conntrack would
+	 * have dropped it.  Hence it's the user's responsibilty to
+	 * packet filter it out, or implement conntrack/NAT for that
+	 * protocol. 8) --RR
+	 */
+	if (!ct)
+		return NF_ACCEPT;
+
+	return __nf_nat_inet_fn(priv, skb, state, ct, ctinfo);
+}
 EXPORT_SYMBOL_GPL(nf_nat_inet_fn);
 
 struct nf_nat_proto_clean {
diff --git a/net/netfilter/nf_nat_proto.c b/net/netfilter/nf_nat_proto.c
index 48cc60084d28..897859730078 100644
--- a/net/netfilter/nf_nat_proto.c
+++ b/net/netfilter/nf_nat_proto.c
@@ -642,7 +642,7 @@ nf_nat_ipv4_fn(void *priv, struct sk_buff *skb,
 		}
 	}
 
-	return nf_nat_inet_fn(priv, skb, state);
+	return __nf_nat_inet_fn(priv, skb, state, ct, ctinfo);
 }
 
 static unsigned int
@@ -934,7 +934,7 @@ nf_nat_ipv6_fn(void *priv, struct sk_buff *skb,
 		}
 	}
 
-	return nf_nat_inet_fn(priv, skb, state);
+	return __nf_nat_inet_fn(priv, skb, state, ct, ctinfo);
 }
 
 static unsigned int
-- 
2.26.2