netfilter: flowtable: simplify route logic

Grab reference to dst from skbuff earlier to simplify route caching.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Florian Westphal <fw@strlen.de>

include/net/netfilter/nf_flow_table.h

@@ -263,8 +263,8 @@ nf_flow_table_offload_del_cb(struct nf_flowtable *flow_table,
 	up_write(&flow_table->flow_block_lock);
 }
 
-int flow_offload_route_init(struct flow_offload *flow,
-			    const struct nf_flow_route *route);
+void flow_offload_route_init(struct flow_offload *flow,
+			     const struct nf_flow_route *route);
 
 int flow_offload_add(struct nf_flowtable *flow_table, struct flow_offload *flow);
 void flow_offload_refresh(struct nf_flowtable *flow_table,

net/netfilter/nf_flow_table_core.c

@@ -125,9 +125,6 @@ static int flow_offload_fill_route(struct flow_offload *flow,
 		break;
 	case FLOW_OFFLOAD_XMIT_XFRM:
 	case FLOW_OFFLOAD_XMIT_NEIGH:
-		if (!dst_hold_safe(route->tuple[dir].dst))
-			return -1;
-
 		flow_tuple->dst_cache = dst;
 		flow_tuple->dst_cookie = flow_offload_dst_cookie(flow_tuple);
 		break;
@@ -148,27 +145,12 @@ static void nft_flow_dst_release(struct flow_offload *flow,
 		dst_release(flow->tuplehash[dir].tuple.dst_cache);
 }
 
-int flow_offload_route_init(struct flow_offload *flow,
+void flow_offload_route_init(struct flow_offload *flow,
 			    const struct nf_flow_route *route)
 {
-	int err;
-
-	err = flow_offload_fill_route(flow, route, FLOW_OFFLOAD_DIR_ORIGINAL);
-	if (err < 0)
-		return err;
-
-	err = flow_offload_fill_route(flow, route, FLOW_OFFLOAD_DIR_REPLY);
-	if (err < 0)
-		goto err_route_reply;
-
+	flow_offload_fill_route(flow, route, FLOW_OFFLOAD_DIR_ORIGINAL);
+	flow_offload_fill_route(flow, route, FLOW_OFFLOAD_DIR_REPLY);
 	flow->type = NF_FLOW_OFFLOAD_ROUTE;
-
-	return 0;
-
-err_route_reply:
-	nft_flow_dst_release(flow, FLOW_OFFLOAD_DIR_ORIGINAL);
-
-	return err;
 }
 EXPORT_SYMBOL_GPL(flow_offload_route_init);
 

net/netfilter/nft_flow_offload.c

@@ -250,9 +250,14 @@ static int nft_flow_route(const struct nft_pktinfo *pkt,
 		break;
 	}
 
+	if (!dst_hold_safe(this_dst))
+		return -ENOENT;
+
 	nf_route(nft_net(pkt), &other_dst, &fl, false, nft_pf(pkt));
-	if (!other_dst)
+	if (!other_dst) {
+		dst_release(this_dst);
 		return -ENOENT;
+	}
 
 	nft_default_forward_path(route, this_dst, dir);
 	nft_default_forward_path(route, other_dst, !dir);
@@ -349,8 +354,7 @@ static void nft_flow_offload_eval(const struct nft_expr *expr,
 	if (!flow)
 		goto err_flow_alloc;
 
-	if (flow_offload_route_init(flow, &route) < 0)
-		goto err_flow_add;
+	flow_offload_route_init(flow, &route);
 
 	if (tcph) {
 		ct->proto.tcp.seen[0].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
@@ -361,12 +365,12 @@ static void nft_flow_offload_eval(const struct nft_expr *expr,
 	if (ret < 0)
 		goto err_flow_add;
 
-	dst_release(route.tuple[!dir].dst);
 	return;
 
 err_flow_add:
 	flow_offload_free(flow);
 err_flow_alloc:
+	dst_release(route.tuple[dir].dst);
 	dst_release(route.tuple[!dir].dst);
 err_flow_route:
 	clear_bit(IPS_OFFLOAD_BIT, &ct->status);