net: sched: only keep the available bits when setting vxlan md->gbp

As we can see from vxlan_build/parse_gbp_hdr(), when processing metadata
on vxlan rx/tx path, only dont_learn/policy_applied/policy_id fields can
be set to or parse from the packet for vxlan gbp option.

So we'd better do the mask when set it in act_tunnel_key and cls_flower.
Otherwise, when users don't know these bits, they may configure with a
value which can never be matched.
Reported-by: Shuang Li <shuali@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/vxlan.h

@@ -121,6 +121,9 @@ struct vxlanhdr_gbp {
 #define VXLAN_GBP_POLICY_APPLIED	(BIT(3) << 16)
 #define VXLAN_GBP_ID_MASK		(0xFFFF)
 
+#define VXLAN_GBP_MASK (VXLAN_GBP_DONT_LEARN | VXLAN_GBP_POLICY_APPLIED | \
+			VXLAN_GBP_ID_MASK)
+
 /*
  * VXLAN Generic Protocol Extension (VXLAN_F_GPE):
  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

net/sched/act_tunnel_key.c

@@ -156,6 +156,7 @@ tunnel_key_copy_vxlan_opt(const struct nlattr *nla, void *dst, int dst_len,
 		struct vxlan_metadata *md = dst;
 
 		md->gbp = nla_get_u32(tb[TCA_TUNNEL_KEY_ENC_OPT_VXLAN_GBP]);
+		md->gbp &= VXLAN_GBP_MASK;
 	}
 
 	return sizeof(struct vxlan_metadata);

net/sched/cls_flower.c

@@ -1175,8 +1175,10 @@ static int fl_set_vxlan_opt(const struct nlattr *nla, struct fl_flow_key *key,
 		return -EINVAL;
 	}
 
-	if (tb[TCA_FLOWER_KEY_ENC_OPT_VXLAN_GBP])
+	if (tb[TCA_FLOWER_KEY_ENC_OPT_VXLAN_GBP]) {
 		md->gbp = nla_get_u32(tb[TCA_FLOWER_KEY_ENC_OPT_VXLAN_GBP]);
+		md->gbp &= VXLAN_GBP_MASK;
+	}
 
 	return sizeof(*md);
 }