[PATCH 1/1] Remove flow offload when ct is removed from userspace

[Sven Auhagen <sven.auhagen@xxxxxxxxxxxx>]

When a ct is removed from user space through a netlink
message it currently returns an error. This
effectively makes a flow undeleteable from user space.

This causes issues when for example the interface IP changes
when using DHCP since the flow has SNAT and DNAT information
attached that are now not updated.

Signed-off-by: Sven Auhagen <sven.auhagen@xxxxxxxxxxxx>
---
 include/net/netfilter/nf_flow_table.h |  2 ++
 net/netfilter/nf_conntrack_netlink.c  | 10 ++++++++++
 net/netfilter/nf_flow_table_core.c    | 24 ++++++++++++++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index c54a7f707e50..51e300e30e62 100644
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -177,6 +177,8 @@ struct flow_offload_tuple_rhash *flow_offload_lookup(struct nf_flowtable *flow_t
 						     struct flow_offload_tuple *tuple);
 void nf_flow_table_cleanup(struct net_device *dev);
 
+void nf_flow_table_ct_remove(struct nf_conn *ct);
+
 int nf_flow_table_init(struct nf_flowtable *flow_table);
 void nf_flow_table_free(struct nf_flowtable *flow_table);
 
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 9ddfcd002d3b..0048a2b597a0 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -51,6 +51,10 @@
 #include <net/netfilter/nf_nat_helper.h>
 #endif
 
+#if IS_ENABLED(CONFIG_NF_FLOW_TABLE_INET)
+#include <net/netfilter/nf_flow_table.h>
+#endif
+
 #include <linux/netfilter/nfnetlink.h>
 #include <linux/netfilter/nfnetlink_conntrack.h>
 
@@ -1310,8 +1314,14 @@ static int ctnetlink_del_conntrack(struct net *net, struct sock *ctnl,
 	ct = nf_ct_tuplehash_to_ctrack(h);
 
 	if (test_bit(IPS_OFFLOAD_BIT, &ct->status)) {
+#if IS_ENABLED(CONFIG_NF_FLOW_TABLE_INET)
+		nf_flow_table_ct_remove(ct);
+		nf_ct_put(ct);
+		return 0;
+#else
 		nf_ct_put(ct);
 		return -EBUSY;
+#endif
 	}
 
 	if (cda[CTA_ID]) {
diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 42da6e337276..9660448ca2d3 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -607,6 +607,30 @@ void nf_flow_table_cleanup(struct net_device *dev)
 }
 EXPORT_SYMBOL_GPL(nf_flow_table_cleanup);
 
+static void nf_flow_offload_ct_remove_step(struct flow_offload *flow,
+					   void *data)
+{
+	struct nf_conn *ct = data;
+
+	if (ct == flow->ct)
+		set_bit(NF_FLOW_TEARDOWN, &flow->flags);
+}
+
+void nf_flow_table_ct_remove(struct nf_conn *ct)
+{
+	struct nf_flowtable *flow_table;
+
+	if (!test_bit(IPS_OFFLOAD_BIT, &ct->status))
+		return;
+
+	list_for_each_entry(flow_table, &flowtables, list) {
+		nf_flow_table_iterate(flow_table,
+				      nf_flow_offload_ct_remove_step,
+				      ct);
+	}
+}
+EXPORT_SYMBOL_GPL(nf_flow_table_ct_remove);
+
 void nf_flow_table_free(struct nf_flowtable *flow_table)
 {
 	mutex_lock(&flowtable_lock);
-- 
2.20.1