netfilter: flowtable: refresh flow if hardware offload fails

If nf_flow_offload_add() fails to add the flow to hardware, then the
NF_FLOW_HW_REFRESH flag bit is set and the flow remains in the flowtable
software path.

If flowtable hardware offload is enabled, this patch enqueues a new
request to offload this flow to hardware.
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_flow_table.h

@@ -95,6 +95,7 @@ enum nf_flow_flags {
 	NF_FLOW_HW,
 	NF_FLOW_HW_DYING,
 	NF_FLOW_HW_DEAD,
+	NF_FLOW_HW_REFRESH,
 };
 
 enum flow_offload_type {

net/netfilter/nf_flow_table_core.c

@@ -243,8 +243,10 @@ int flow_offload_add(struct nf_flowtable *flow_table, struct flow_offload *flow)
 		return err;
 	}
 
-	if (nf_flowtable_hw_offload(flow_table))
+	if (nf_flowtable_hw_offload(flow_table)) {
+		__set_bit(NF_FLOW_HW, &flow->flags);
 		nf_flow_offload_add(flow_table, flow);
+	}
 
 	return 0;
 }

net/netfilter/nf_flow_table_ip.c

@@ -232,6 +232,13 @@ static unsigned int nf_flow_xmit_xfrm(struct sk_buff *skb,
 	return NF_STOLEN;
 }
 
+static bool nf_flow_offload_refresh(struct nf_flowtable *flow_table,
+				    struct flow_offload *flow)
+{
+	return nf_flowtable_hw_offload(flow_table) &&
+	       test_and_clear_bit(NF_FLOW_HW_REFRESH, &flow->flags);
+}
+
 unsigned int
 nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
 			const struct nf_hook_state *state)
@@ -272,6 +279,9 @@ nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
 	if (nf_flow_state_check(flow, ip_hdr(skb)->protocol, skb, thoff))
 		return NF_ACCEPT;
 
+	if (unlikely(nf_flow_offload_refresh(flow_table, flow)))
+		nf_flow_offload_add(flow_table, flow);
+
 	if (nf_flow_offload_dst_check(&rt->dst)) {
 		flow_offload_teardown(flow);
 		return NF_ACCEPT;
@@ -498,6 +508,9 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 				sizeof(*ip6h)))
 		return NF_ACCEPT;
 
+	if (unlikely(nf_flow_offload_refresh(flow_table, flow)))
+		nf_flow_offload_add(flow_table, flow);
+
 	if (nf_flow_offload_dst_check(&rt->dst)) {
 		flow_offload_teardown(flow);
 		return NF_ACCEPT;

net/netfilter/nf_flow_table_offload.c

@@ -654,20 +654,20 @@ static int flow_offload_rule_add(struct flow_offload_work *offload,
 	return 0;
 }
 
-static int flow_offload_work_add(struct flow_offload_work *offload)
+static void flow_offload_work_add(struct flow_offload_work *offload)
 {
 	struct nf_flow_rule *flow_rule[FLOW_OFFLOAD_DIR_MAX];
 	int err;
 
 	err = nf_flow_offload_alloc(offload, flow_rule);
 	if (err < 0)
-		return -ENOMEM;
+		return;
 
 	err = flow_offload_rule_add(offload, flow_rule);
+	if (err < 0)
+		set_bit(NF_FLOW_HW_REFRESH, &offload->flow->flags);
 
 	nf_flow_offload_destroy(flow_rule);
-
-	return err;
 }
 
 static void flow_offload_work_del(struct flow_offload_work *offload)
@@ -712,7 +712,6 @@ static void flow_offload_work_handler(struct work_struct *work)
 {
 	struct flow_offload_work *offload, *next;
 	LIST_HEAD(offload_pending_list);
-	int ret;
 
 	spin_lock_bh(&flow_offload_pending_list_lock);
 	list_replace_init(&flow_offload_pending_list, &offload_pending_list);
@@ -721,9 +720,7 @@ static void flow_offload_work_handler(struct work_struct *work)
 	list_for_each_entry_safe(offload, next, &offload_pending_list, list) {
 		switch (offload->cmd) {
 		case FLOW_CLS_REPLACE:
-			ret = flow_offload_work_add(offload);
-			if (ret < 0)
-				__clear_bit(NF_FLOW_HW, &offload->flow->flags);
+			flow_offload_work_add(offload);
 			break;
 		case FLOW_CLS_DESTROY:
 			flow_offload_work_del(offload);
@@ -776,7 +773,6 @@ void nf_flow_offload_add(struct nf_flowtable *flowtable,
 	if (!offload)
 		return;
 
-	__set_bit(NF_FLOW_HW, &flow->flags);
 	flow_offload_queue_work(offload);
 }