net: move the nat function to nf_nat_ovs for ovs and tc

There are two nat functions are nearly the same in both OVS and
TC code, (ovs_)ct_nat_execute() and ovs_ct_nat/tcf_ct_act_nat().

This patch creates nf_nat_ovs.c under netfilter and moves them
there then exports nf_ct_nat() so that it can be shared by both
OVS and TC, and keeps the nat (type) check and nat flag update
in OVS and TC's own place, as these parts are different between
OVS and TC.

Note that in OVS nat function it was using skb->protocol to get
the proto as it already skips vlans in key_extract(), while it
doesn't in TC, and TC has to call skb_protocol() to get proto.
So in nf_ct_nat_execute(), we keep using skb_protocol() which
works for both OVS and TC contrack.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Aaron Conole <aconole@redhat.com>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 12 insertions, 125 deletions

diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index 4662a6ce8a7e..777d6b50505c 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -977,6 +977,7 @@ config NET_ACT_TUNNEL_KEY
 config NET_ACT_CT
 	tristate "connection tracking tc action"
 	depends on NET_CLS_ACT && NF_CONNTRACK && (!NF_NAT || NF_NAT) && NF_FLOW_TABLE
+	select NF_NAT_OVS if NF_NAT
 	help
 	  Say Y here to allow sending the packets to conntrack module.
 
diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
index eac4e07eb56b..0ca2bb8ed026 100644
--- a/net/sched/act_ct.c
+++ b/net/sched/act_ct.c
@@ -864,90 +864,6 @@ static void tcf_ct_params_free_rcu(struct rcu_head *head)
 	tcf_ct_params_free(params);
 }
 
-#if IS_ENABLED(CONFIG_NF_NAT)
-/* Modelled after nf_nat_ipv[46]_fn().
- * range is only used for new, uninitialized NAT state.
- * Returns either NF_ACCEPT or NF_DROP.
- */
-static int ct_nat_execute(struct sk_buff *skb, struct nf_conn *ct,
-			  enum ip_conntrack_info ctinfo,
-			  const struct nf_nat_range2 *range,
-			  enum nf_nat_manip_type maniptype)
-{
-	__be16 proto = skb_protocol(skb, true);
-	int hooknum, err = NF_ACCEPT;
-
-	/* See HOOK2MANIP(). */
-	if (maniptype == NF_NAT_MANIP_SRC)
-		hooknum = NF_INET_LOCAL_IN; /* Source NAT */
-	else
-		hooknum = NF_INET_LOCAL_OUT; /* Destination NAT */
-
-	switch (ctinfo) {
-	case IP_CT_RELATED:
-	case IP_CT_RELATED_REPLY:
-		if (proto == htons(ETH_P_IP) &&
-		    ip_hdr(skb)->protocol == IPPROTO_ICMP) {
-			if (!nf_nat_icmp_reply_translation(skb, ct, ctinfo,
-							   hooknum))
-				err = NF_DROP;
-			goto out;
-		} else if (IS_ENABLED(CONFIG_IPV6) && proto == htons(ETH_P_IPV6)) {
-			__be16 frag_off;
-			u8 nexthdr = ipv6_hdr(skb)->nexthdr;
-			int hdrlen = ipv6_skip_exthdr(skb,
-						      sizeof(struct ipv6hdr),
-						      &nexthdr, &frag_off);
-
-			if (hdrlen >= 0 && nexthdr == IPPROTO_ICMPV6) {
-				if (!nf_nat_icmpv6_reply_translation(skb, ct,
-								     ctinfo,
-								     hooknum,
-								     hdrlen))
-					err = NF_DROP;
-				goto out;
-			}
-		}
-		/* Non-ICMP, fall thru to initialize if needed. */
-		fallthrough;
-	case IP_CT_NEW:
-		/* Seen it before?  This can happen for loopback, retrans,
-		 * or local packets.
-		 */
-		if (!nf_nat_initialized(ct, maniptype)) {
-			/* Initialize according to the NAT action. */
-			err = (range && range->flags & NF_NAT_RANGE_MAP_IPS)
-				/* Action is set up to establish a new
-				 * mapping.
-				 */
-				? nf_nat_setup_info(ct, range, maniptype)
-				: nf_nat_alloc_null_binding(ct, hooknum);
-			if (err != NF_ACCEPT)
-				goto out;
-		}
-		break;
-
-	case IP_CT_ESTABLISHED:
-	case IP_CT_ESTABLISHED_REPLY:
-		break;
-
-	default:
-		err = NF_DROP;
-		goto out;
-	}
-
-	err = nf_nat_packet(ct, ctinfo, hooknum, skb);
-out:
-	if (err == NF_ACCEPT) {
-		if (maniptype == NF_NAT_MANIP_SRC)
-			tc_skb_cb(skb)->post_ct_snat = 1;
-		if (maniptype == NF_NAT_MANIP_DST)
-			tc_skb_cb(skb)->post_ct_dnat = 1;
-	}
-	return err;
-}
-#endif /* CONFIG_NF_NAT */
-
 static void tcf_ct_act_set_mark(struct nf_conn *ct, u32 mark, u32 mask)
 {
 #if IS_ENABLED(CONFIG_NF_CONNTRACK_MARK)
@@ -987,52 +903,22 @@ static int tcf_ct_act_nat(struct sk_buff *skb,
 			  bool commit)
 {
 #if IS_ENABLED(CONFIG_NF_NAT)
-	int err;
-	enum nf_nat_manip_type maniptype;
+	int err, action = 0;
 
 	if (!(ct_action & TCA_CT_ACT_NAT))
 		return NF_ACCEPT;
+	if (ct_action & TCA_CT_ACT_NAT_SRC)
+		action |= BIT(NF_NAT_MANIP_SRC);
+	if (ct_action & TCA_CT_ACT_NAT_DST)
+		action |= BIT(NF_NAT_MANIP_DST);
 
-	/* Add NAT extension if not confirmed yet. */
-	if (!nf_ct_is_confirmed(ct) && !nf_ct_nat_ext_add(ct))
-		return NF_DROP;   /* Can't NAT. */
-
-	if (ctinfo != IP_CT_NEW && (ct->status & IPS_NAT_MASK) &&
-	    (ctinfo != IP_CT_RELATED || commit)) {
-		/* NAT an established or related connection like before. */
-		if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY)
-			/* This is the REPLY direction for a connection
-			 * for which NAT was applied in the forward
-			 * direction.  Do the reverse NAT.
-			 */
-			maniptype = ct->status & IPS_SRC_NAT
-				? NF_NAT_MANIP_DST : NF_NAT_MANIP_SRC;
-		else
-			maniptype = ct->status & IPS_SRC_NAT
-				? NF_NAT_MANIP_SRC : NF_NAT_MANIP_DST;
-	} else if (ct_action & TCA_CT_ACT_NAT_SRC) {
-		maniptype = NF_NAT_MANIP_SRC;
-	} else if (ct_action & TCA_CT_ACT_NAT_DST) {
-		maniptype = NF_NAT_MANIP_DST;
-	} else {
-		return NF_ACCEPT;
-	}
+	err = nf_ct_nat(skb, ct, ctinfo, &action, range, commit);
+
+	if (action & BIT(NF_NAT_MANIP_SRC))
+		tc_skb_cb(skb)->post_ct_snat = 1;
+	if (action & BIT(NF_NAT_MANIP_DST))
+		tc_skb_cb(skb)->post_ct_dnat = 1;
 
-	err = ct_nat_execute(skb, ct, ctinfo, range, maniptype);
-	if (err == NF_ACCEPT && ct->status & IPS_DST_NAT) {
-		if (ct->status & IPS_SRC_NAT) {
-			if (maniptype == NF_NAT_MANIP_SRC)
-				maniptype = NF_NAT_MANIP_DST;
-			else
-				maniptype = NF_NAT_MANIP_SRC;
-
-			err = ct_nat_execute(skb, ct, ctinfo, range,
-					     maniptype);
-		} else if (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) {
-			err = ct_nat_execute(skb, ct, ctinfo, NULL,
-					     NF_NAT_MANIP_SRC);
-		}
-	}
 	return err;
 #else
 	return NF_ACCEPT;