openvswitch: Specify the minimal length of OVS_PACKET_ATTR_PACKET in the policy

Specifying the minimal length in the policy makes it reuseable
and documents the interface.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: Jesse Gross <jesse@nicira.com>

net/openvswitch/datapath.c

@@ -662,8 +662,7 @@ static int ovs_packet_cmd_execute(struct sk_buff *skb, struct genl_info *info)
 
 	err = -EINVAL;
 	if (!a[OVS_PACKET_ATTR_PACKET] || !a[OVS_PACKET_ATTR_KEY] ||
-	    !a[OVS_PACKET_ATTR_ACTIONS] ||
-	    nla_len(a[OVS_PACKET_ATTR_PACKET]) < ETH_HLEN)
+	    !a[OVS_PACKET_ATTR_ACTIONS])
 		goto err;
 
 	len = nla_len(a[OVS_PACKET_ATTR_PACKET]);
@@ -744,7 +743,7 @@ err:
 }
 
 static const struct nla_policy packet_policy[OVS_PACKET_ATTR_MAX + 1] = {
-	[OVS_PACKET_ATTR_PACKET] = { .type = NLA_UNSPEC },
+	[OVS_PACKET_ATTR_PACKET] = { .len = ETH_HLEN },
 	[OVS_PACKET_ATTR_KEY] = { .type = NLA_NESTED },
 	[OVS_PACKET_ATTR_ACTIONS] = { .type = NLA_NESTED },
 };