netfilter: nf_nat: change sequence number adjustments to 32 bits

Using 16 bits is too small, when many adjustments happen the offsets might
overflow and break the connection.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/linux/netfilter.h

@@ -330,7 +330,7 @@ extern struct nfq_ct_hook __rcu *nfq_ct_hook;
 
 struct nfq_ct_nat_hook {
 	void (*seq_adjust)(struct sk_buff *skb, struct nf_conn *ct,
-			   u32 ctinfo, int off);
+			   u32 ctinfo, s32 off);
 };
 extern struct nfq_ct_nat_hook __rcu *nfq_ct_nat_hook;
 #else

include/net/netfilter/nf_conntrack.h

@@ -234,7 +234,7 @@ static inline bool nf_ct_kill(struct nf_conn *ct)
 }
 
 /* These are for NAT.  Icky. */
-extern s16 (*nf_ct_nat_offset)(const struct nf_conn *ct,
+extern s32 (*nf_ct_nat_offset)(const struct nf_conn *ct,
 			       enum ip_conntrack_dir dir,
 			       u32 seq);
 

include/net/netfilter/nf_nat.h

@@ -19,7 +19,7 @@ struct nf_nat_seq {
 	u_int32_t correction_pos;
 
 	/* sequence number offset before and after last modification */
-	int16_t offset_before, offset_after;
+	int32_t offset_before, offset_after;
 };
 
 #include <linux/list.h>

include/net/netfilter/nf_nat_helper.h

@@ -41,7 +41,7 @@ extern int nf_nat_mangle_udp_packet(struct sk_buff *skb,
 
 extern void nf_nat_set_seq_adjust(struct nf_conn *ct,
 				  enum ip_conntrack_info ctinfo,
-				  __be32 seq, s16 off);
+				  __be32 seq, s32 off);
 extern int nf_nat_seq_adjust(struct sk_buff *skb,
 			     struct nf_conn *ct,
 			     enum ip_conntrack_info ctinfo,
@@ -56,11 +56,11 @@ extern int (*nf_nat_seq_adjust_hook)(struct sk_buff *skb,
 extern void nf_nat_follow_master(struct nf_conn *ct,
 				 struct nf_conntrack_expect *this);
 
-extern s16 nf_nat_get_offset(const struct nf_conn *ct,
+extern s32 nf_nat_get_offset(const struct nf_conn *ct,
 			     enum ip_conntrack_dir dir,
 			     u32 seq);
 
 extern void nf_nat_tcp_seq_adjust(struct sk_buff *skb, struct nf_conn *ct,
-				  u32 dir, int off);
+				  u32 dir, s32 off);
 
 #endif

net/netfilter/nf_conntrack_core.c

@@ -1695,7 +1695,7 @@ int nf_conntrack_init_net(struct net *net)
 	return ret;
 }
 
-s16 (*nf_ct_nat_offset)(const struct nf_conn *ct,
+s32 (*nf_ct_nat_offset)(const struct nf_conn *ct,
 			enum ip_conntrack_dir dir,
 			u32 seq);
 EXPORT_SYMBOL_GPL(nf_ct_nat_offset);

net/netfilter/nf_conntrack_proto_tcp.c

@@ -496,7 +496,7 @@ static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,
 }
 
 #ifdef CONFIG_NF_NAT_NEEDED
-static inline s16 nat_offset(const struct nf_conn *ct,
+static inline s32 nat_offset(const struct nf_conn *ct,
 			     enum ip_conntrack_dir dir,
 			     u32 seq)
 {
@@ -525,7 +525,7 @@ static bool tcp_in_window(const struct nf_conn *ct,
 	struct ip_ct_tcp_state *receiver = &state->seen[!dir];
 	const struct nf_conntrack_tuple *tuple = &ct->tuplehash[dir].tuple;
 	__u32 seq, ack, sack, end, win, swin;
-	s16 receiver_offset;
+	s32 receiver_offset;
 	bool res;
 
 	/*

net/netfilter/nf_nat_helper.c

@@ -68,13 +68,13 @@ adjust_tcp_sequence(u32 seq,
 }
 
 /* Get the offset value, for conntrack */
-s16 nf_nat_get_offset(const struct nf_conn *ct,
+s32 nf_nat_get_offset(const struct nf_conn *ct,
 		      enum ip_conntrack_dir dir,
 		      u32 seq)
 {
 	struct nf_conn_nat *nat = nfct_nat(ct);
 	struct nf_nat_seq *this_way;
-	s16 offset;
+	s32 offset;
 
 	if (!nat)
 		return 0;
@@ -143,7 +143,7 @@ static int enlarge_skb(struct sk_buff *skb, unsigned int extra)
 }
 
 void nf_nat_set_seq_adjust(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
-			   __be32 seq, s16 off)
+			   __be32 seq, s32 off)
 {
 	if (!off)
 		return;
@@ -370,7 +370,7 @@ nf_nat_seq_adjust(struct sk_buff *skb,
 	struct tcphdr *tcph;
 	int dir;
 	__be32 newseq, newack;
-	s16 seqoff, ackoff;
+	s32 seqoff, ackoff;
 	struct nf_conn_nat *nat = nfct_nat(ct);
 	struct nf_nat_seq *this_way, *other_way;
 	int res;