netfilter: pptp: attach nat extension when needed

make sure nat extension gets added if the master conntrack is subject to
NAT. This will be required once the nat core stops adding it by default.

Signed-off-by: Florian Westphal <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

net/ipv4/netfilter/nf_nat_pptp.c

···
 	const struct nf_ct_pptp_master *ct_pptp_info;
 	const struct nf_nat_pptp *nat_pptp_info;
 	struct nf_nat_range range;
+	struct nf_conn_nat *nat;
 
+	nat = nf_ct_nat_ext_add(ct);
+	if (WARN_ON_ONCE(!nat))
+		return;
+
+	nat_pptp_info = &nat->help.nat_pptp_info;
 	ct_pptp_info = nfct_help_data(master);
-	nat_pptp_info = &nfct_nat(master)->help.nat_pptp_info;
 
 	/* And here goes the grand finale of corrosion... */
 	if (exp->dir == IP_CT_DIR_ORIGINAL) {
···
 
 {
 	struct nf_ct_pptp_master *ct_pptp_info;
+	struct nf_conn_nat *nat = nfct_nat(ct);
 	struct nf_nat_pptp *nat_pptp_info;
 	u_int16_t msg;
 	__be16 new_callid;
 	unsigned int cid_off;
 
+	if (WARN_ON_ONCE(!nat))
+		return NF_DROP;
+
+	nat_pptp_info = &nat->help.nat_pptp_info;
 	ct_pptp_info = nfct_help_data(ct);
-	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
 
 	new_callid = ct_pptp_info->pns_call_id;
 
···
 	     struct nf_conntrack_expect *expect_reply)
 {
 	const struct nf_conn *ct = expect_orig->master;
+	struct nf_conn_nat *nat = nfct_nat(ct);
 	struct nf_ct_pptp_master *ct_pptp_info;
 	struct nf_nat_pptp *nat_pptp_info;
 
+	if (WARN_ON_ONCE(!nat))
+		return;
+
+	nat_pptp_info = &nat->help.nat_pptp_info;
 	ct_pptp_info = nfct_help_data(ct);
-	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
 
 	/* save original PAC call ID in nat_info */
 	nat_pptp_info->pac_call_id = ct_pptp_info->pac_call_id;
···
 		 union pptp_ctrl_union *pptpReq)
 {
 	const struct nf_nat_pptp *nat_pptp_info;
+	struct nf_conn_nat *nat = nfct_nat(ct);
 	u_int16_t msg;
 	__be16 new_pcid;
 	unsigned int pcid_off;
 
-	nat_pptp_info = &nfct_nat(ct)->help.nat_pptp_info;
+	if (WARN_ON_ONCE(!nat))
+		return NF_DROP;
+
+	nat_pptp_info = &nat->help.nat_pptp_info;
 	new_pcid = nat_pptp_info->pns_call_id;
 
 	switch (msg = ntohs(ctlh->messageType)) {

net/netfilter/nf_conntrack_pptp.c

···
 	goto out_put_both;
 }
 
-static inline int
+static int
 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff,
 		 struct PptpControlHeader *ctlh,
 		 union pptp_ctrl_union *pptpReq,
···
 	return NF_ACCEPT;
 }
 
-static inline int
+static int
 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff,
 		  struct PptpControlHeader *ctlh,
 		  union pptp_ctrl_union *pptpReq,
···
 	int ret;
 	u_int16_t msg;
 
+#if IS_ENABLED(CONFIG_NF_NAT)
+	if (!nf_ct_is_confirmed(ct) && (ct->status & IPS_NAT_MASK)) {
+		struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT);
+
+		if (!nat && !nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC))
+			return NF_DROP;
+	}
+#endif
 	/* don't do any tracking before tcp handshake complete */
 	if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY)
 		return NF_ACCEPT;