[PATCH net-next 13/14] netfilter: flowtable: teardown flow if cached mtu is stale

[Pablo Neira Ayuso <pablo@netfilter.org>]

Tear down the flow entry in the unlikely case that the interface mtu
changes, this gives the flow a chance to refresh the cached mtu,
otherwise such refresh does not occur until flow entry expires.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 net/netfilter/nf_flow_table_ip.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
index 98edcaa37b38..a22856106383 100644
--- a/net/netfilter/nf_flow_table_ip.c
+++ b/net/netfilter/nf_flow_table_ip.c
@@ -377,8 +377,10 @@ static int nf_flow_offload_forward(struct nf_flowtable_ctx *ctx,
 	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 
 	mtu = flow->tuplehash[dir].tuple.mtu + ctx->offset;
-	if (unlikely(nf_flow_exceeds_mtu(skb, mtu)))
+	if (unlikely(nf_flow_exceeds_mtu(skb, mtu))) {
+		flow_offload_teardown(flow);
 		return 0;
+	}
 
 	iph = (struct iphdr *)(skb_network_header(skb) + ctx->offset);
 	thoff = (iph->ihl * 4) + ctx->offset;
@@ -656,8 +658,10 @@ static int nf_flow_offload_ipv6_forward(struct nf_flowtable_ctx *ctx,
 	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 
 	mtu = flow->tuplehash[dir].tuple.mtu + ctx->offset;
-	if (unlikely(nf_flow_exceeds_mtu(skb, mtu)))
+	if (unlikely(nf_flow_exceeds_mtu(skb, mtu))) {
+		flow_offload_teardown(flow);
 		return 0;
+	}
 
 	ip6h = (struct ipv6hdr *)(skb_network_header(skb) + ctx->offset);
 	thoff = sizeof(*ip6h) + ctx->offset;
-- 
2.30.2