openvswitch: prepare for stolen verdict coming from conntrack and nat engine

At this time, conntrack either returns NF_ACCEPT or NF_DROP.
To improve debuging it would be nice to be able to replace NF_DROP
verdict with NF_DROP_REASON() helper,

This helper releases the skb instantly (so drop_monitor can pinpoint
precise location) and returns NF_STOLEN.

Prepare call sites to deal with this before introducing such changes
in conntrack and nat core.

Signed-off-by: Florian Westphal <[email protected]>
Reviewed-by: Aaron Conole <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: Florian Westphal

net/openvswitch/conntrack.c

@@ -679,6 +679,8 @@ static int ovs_ct_nat(struct net *net, struct sw_flow_key *key,
 		action |= BIT(NF_NAT_MANIP_DST);
 
 	err = nf_ct_nat(skb, ct, ctinfo, &action, &info->range, info->commit);
+	if (err != NF_ACCEPT)
+		return err;
 
 	if (action & BIT(NF_NAT_MANIP_SRC))
 		ovs_nat_update_key(key, skb, NF_NAT_MANIP_SRC);
@@ -697,6 +699,22 @@ static int ovs_ct_nat(struct net *net, struct sw_flow_key *key,
 }
 #endif
 
+static int verdict_to_errno(unsigned int verdict)
+{
+	switch (verdict & NF_VERDICT_MASK) {
+	case NF_ACCEPT:
+		return 0;
+	case NF_DROP:
+		return -EINVAL;
+	case NF_STOLEN:
+		return -EINPROGRESS;
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
 /* Pass 'skb' through conntrack in 'net', using zone configured in 'info', if
  * not done already.  Update key with new CT state after passing the packet
  * through conntrack.
@@ -735,7 +753,7 @@ static int __ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
 
 		err = nf_conntrack_in(skb, &state);
 		if (err != NF_ACCEPT)
-			return -ENOENT;
+			return verdict_to_errno(err);
 
 		/* Clear CT state NAT flags to mark that we have not yet done
 		 * NAT after the nf_conntrack_in() call.  We can actually clear
@@ -762,9 +780,12 @@ static int __ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
 		 * the key->ct_state.
 		 */
 		if (info->nat && !(key->ct_state & OVS_CS_F_NAT_MASK) &&
-		    (nf_ct_is_confirmed(ct) || info->commit) &&
-		    ovs_ct_nat(net, key, info, skb, ct, ctinfo) != NF_ACCEPT) {
-			return -EINVAL;
+		    (nf_ct_is_confirmed(ct) || info->commit)) {
+			int err = ovs_ct_nat(net, key, info, skb, ct, ctinfo);
+
+			err = verdict_to_errno(err);
+			if (err)
+				return err;
 		}
 
 		/* Userspace may decide to perform a ct lookup without a helper
@@ -795,9 +816,12 @@ static int __ovs_ct_lookup(struct net *net, struct sw_flow_key *key,
 		 * - When committing an unconfirmed connection.
 		 */
 		if ((nf_ct_is_confirmed(ct) ? !cached || add_helper :
-					      info->commit) &&
-		    nf_ct_helper(skb, ct, ctinfo, info->family) != NF_ACCEPT) {
-			return -EINVAL;
+					      info->commit)) {
+			int err = nf_ct_helper(skb, ct, ctinfo, info->family);
+
+			err = verdict_to_errno(err);
+			if (err)
+				return err;
 		}
 
 		if (nf_ct_protonum(ct) == IPPROTO_TCP &&
@@ -1001,10 +1025,9 @@ static int ovs_ct_commit(struct net *net, struct sw_flow_key *key,
 	/* This will take care of sending queued events even if the connection
 	 * is already confirmed.
 	 */
-	if (nf_conntrack_confirm(skb) != NF_ACCEPT)
-		return -EINVAL;
+	err = nf_conntrack_confirm(skb);
 
-	return 0;
+	return verdict_to_errno(err);
 }
 
 /* Returns 0 on success, -EINPROGRESS if 'skb' is stolen, or other nonzero
@@ -1039,6 +1062,10 @@ int ovs_ct_execute(struct net *net, struct sk_buff *skb,
 	else
 		err = ovs_ct_lookup(net, key, info, skb);
 
+	/* conntrack core returned NF_STOLEN */
+	if (err == -EINPROGRESS)
+		return err;
+
 	skb_push_rcsum(skb, nh_ofs);
 	if (err)
 		ovs_kfree_skb_reason(skb, OVS_DROP_CONNTRACK);