openvswitch: Allow user space to announce ability to accept unaligned Netlink messages

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Reviewed-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 50d7782..6a9b0cb 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -1040,6 +1040,7 @@
 static const struct nla_policy datapath_policy[OVS_DP_ATTR_MAX + 1] = {
 	[OVS_DP_ATTR_NAME] = { .type = NLA_NUL_STRING, .len = IFNAMSIZ - 1 },
 	[OVS_DP_ATTR_UPCALL_PID] = { .type = NLA_U32 },
+	[OVS_DP_ATTR_USER_FEATURES] = { .type = NLA_U32 },
 };
 
 static struct genl_family dp_datapath_genl_family = {
@@ -1098,6 +1099,9 @@
 			&dp_megaflow_stats))
 		goto nla_put_failure;
 
+	if (nla_put_u32(skb, OVS_DP_ATTR_USER_FEATURES, dp->user_features))
+		goto nla_put_failure;
+
 	return genlmsg_end(skb, ovs_header);
 
 nla_put_failure:
@@ -1144,6 +1148,12 @@
 	return dp ? dp : ERR_PTR(-ENODEV);
 }
 
+static void ovs_dp_change(struct datapath *dp, struct nlattr **a)
+{
+	if (a[OVS_DP_ATTR_USER_FEATURES])
+		dp->user_features = nla_get_u32(a[OVS_DP_ATTR_USER_FEATURES]);
+}
+
 static int ovs_dp_cmd_new(struct sk_buff *skb, struct genl_info *info)
 {
 	struct nlattr **a = info->attrs;
@@ -1202,6 +1212,8 @@
 	parms.port_no = OVSP_LOCAL;
 	parms.upcall_portid = nla_get_u32(a[OVS_DP_ATTR_UPCALL_PID]);
 
+	ovs_dp_change(dp, a);
+
 	vport = new_vport(&parms);
 	if (IS_ERR(vport)) {
 		err = PTR_ERR(vport);
@@ -1305,6 +1317,8 @@
 	if (IS_ERR(dp))
 		goto unlock;
 
+	ovs_dp_change(dp, info->attrs);
+
 	reply = ovs_dp_cmd_build_info(dp, info, OVS_DP_CMD_NEW);
 	if (IS_ERR(reply)) {
 		err = PTR_ERR(reply);
diff --git a/net/openvswitch/datapath.h b/net/openvswitch/datapath.h
index ba13be4..62619a4 100644
--- a/net/openvswitch/datapath.h
+++ b/net/openvswitch/datapath.h
@@ -88,6 +88,8 @@
 	/* Network namespace ref. */
 	struct net *net;
 #endif
+
+	u32 user_features;
 };
 
 /**