[PATCH net-next,v3 1/9] netfilter: flowtable: add hash offset field to tuple

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

Add a placeholder field to calculate hash tuple offset. Similar to
2c407aca6497 ("netfilter: conntrack: avoid gcc-10 zero-length-bounds
warning").

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
 include/net/netfilter/nf_flow_table.h | 4 ++++
 net/netfilter/nf_flow_table_core.c    | 6 +++---
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/net/netfilter/nf_flow_table.h b/include/net/netfilter/nf_flow_table.h
index 16e8b2f8d006..54c4d5c908a5 100644
--- a/include/net/netfilter/nf_flow_table.h
+++ b/include/net/netfilter/nf_flow_table.h
@@ -107,6 +107,10 @@ struct flow_offload_tuple {
 
 	u8				l3proto;
 	u8				l4proto;
+
+	/* All members above are keys for lookups, see flow_offload_hash(). */
+	struct { }			__hash;
+
 	u8				dir;
 
 	u16				mtu;
diff --git a/net/netfilter/nf_flow_table_core.c b/net/netfilter/nf_flow_table_core.c
index 513f78db3cb2..55fca71ace26 100644
--- a/net/netfilter/nf_flow_table_core.c
+++ b/net/netfilter/nf_flow_table_core.c
@@ -191,14 +191,14 @@ static u32 flow_offload_hash(const void *data, u32 len, u32 seed)
 {
 	const struct flow_offload_tuple *tuple = data;
 
-	return jhash(tuple, offsetof(struct flow_offload_tuple, dir), seed);
+	return jhash(tuple, offsetof(struct flow_offload_tuple, __hash), seed);
 }
 
 static u32 flow_offload_hash_obj(const void *data, u32 len, u32 seed)
 {
 	const struct flow_offload_tuple_rhash *tuplehash = data;
 
-	return jhash(&tuplehash->tuple, offsetof(struct flow_offload_tuple, dir), seed);
+	return jhash(&tuplehash->tuple, offsetof(struct flow_offload_tuple, __hash), seed);
 }
 
 static int flow_offload_hash_cmp(struct rhashtable_compare_arg *arg,
@@ -207,7 +207,7 @@ static int flow_offload_hash_cmp(struct rhashtable_compare_arg *arg,
 	const struct flow_offload_tuple *tuple = arg->key;
 	const struct flow_offload_tuple_rhash *x = ptr;
 
-	if (memcmp(&x->tuple, tuple, offsetof(struct flow_offload_tuple, dir)))
+	if (memcmp(&x->tuple, tuple, offsetof(struct flow_offload_tuple, __hash)))
 		return 1;
 
 	return 0;
-- 
2.20.1