datapath: Build flow cmd netlink reply only if needed.

Use netlink_has_listeners() and NLM_F_ECHO flag to determine if a
reply is needed or not for OVS_FLOW_CMD_NEW, OVS_FLOW_CMD_SET, or
OVS_FLOW_CMD_DEL.  Currently, OVS userspace does not request a reply
for OVS_FLOW_CMD_NEW, but usually does for OVS_FLOW_CMD_DEL, as stats
may have changed.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 93f8e36..d1b0155 100644 (file)
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -64,6 +64,15 @@
 
 int ovs_net_id __read_mostly;
 
+/* Check if need to build a reply message.
+ * OVS userspace sets the NLM_F_ECHO flag if it needs the reply. */
+static bool ovs_must_notify(struct genl_info *info,
+                           const struct genl_multicast_group *grp)
+{
+       return info->nlhdr->nlmsg_flags & NLM_F_ECHO ||
+               netlink_has_listeners(genl_info_net(info)->genl_sock, grp->id);
+}
+
 static void ovs_notify(struct sk_buff *skb, struct genl_info *info,
                       struct genl_multicast_group *grp)
 {
@@ -747,27 +756,37 @@ error:
 
 /* Must be called with ovs_mutex. */
 static struct sk_buff *ovs_flow_cmd_alloc_info(struct sw_flow *flow,
-                                              struct genl_info *info)
+                                              struct genl_info *info,
+                                              bool always)
 {
+       struct sk_buff *skb;
        size_t len;
 
+       if (!always && !ovs_must_notify(info, &ovs_dp_flow_multicast_group))
+               return NULL;
+
        len = ovs_flow_cmd_msg_size(ovsl_dereference(flow->sf_acts));
 
-       return genlmsg_new_unicast(len, info, GFP_KERNEL);
+       skb = genlmsg_new_unicast(len, info, GFP_KERNEL);
+
+       if (!skb)
+               return ERR_PTR(-ENOMEM);
+
+       return skb;
 }
 
 /* Must be called with ovs_mutex. */
 static struct sk_buff *ovs_flow_cmd_build_info(struct sw_flow *flow,
                                               struct datapath *dp,
                                               struct genl_info *info,
-                                              u8 cmd)
+                                              u8 cmd, bool always)
 {
        struct sk_buff *skb;
        int retval;
 
-       skb = ovs_flow_cmd_alloc_info(flow, info);
-       if (!skb)
-               return ERR_PTR(-ENOMEM);
+       skb = ovs_flow_cmd_alloc_info(flow, info, always);
+       if (!skb || IS_ERR(skb))
+               return skb;
 
        retval = ovs_flow_cmd_fill_info(flow, dp, skb, info->snd_portid,
                                        info->snd_seq, 0, cmd);
@@ -851,7 +870,8 @@ static int ovs_flow_cmd_new_or_set(struct sk_buff *skb, struct genl_info *info)
                        goto err_flow_free;
                }
 
-               reply = ovs_flow_cmd_build_info(flow, dp, info, OVS_FLOW_CMD_NEW);
+               reply = ovs_flow_cmd_build_info(flow, dp, info,
+                                               OVS_FLOW_CMD_NEW, false);
        } else {
                /* We found a matching flow. */
                /* Bail out if we're not allowed to modify an existing flow.
@@ -877,7 +897,8 @@ static int ovs_flow_cmd_new_or_set(struct sk_buff *skb, struct genl_info *info)
                        rcu_assign_pointer(flow->sf_acts, acts);
                        ovs_nla_free_flow_actions(old_acts);
                }
-               reply = ovs_flow_cmd_build_info(flow, dp, info, OVS_FLOW_CMD_NEW);
+               reply = ovs_flow_cmd_build_info(flow, dp, info,
+                                               OVS_FLOW_CMD_NEW, false);
 
                /* Clear stats. */
                if (a[OVS_FLOW_ATTR_CLEAR])
@@ -885,11 +906,14 @@ static int ovs_flow_cmd_new_or_set(struct sk_buff *skb, struct genl_info *info)
        }
        ovs_unlock();
 
-       if (!IS_ERR(reply))
-               ovs_notify(reply, info, &ovs_dp_flow_multicast_group);
-       else
-               netlink_set_err(sock_net(skb->sk)->genl_sock, 0,
-                               ovs_dp_flow_multicast_group.id, PTR_ERR(reply));
+       if (reply) {
+               if (!IS_ERR(reply))
+                       ovs_notify(reply, info, &ovs_dp_flow_multicast_group);
+               else
+                       netlink_set_err(sock_net(skb->sk)->genl_sock, 0,
+                                       ovs_dp_flow_multicast_group.id,
+                                       PTR_ERR(reply));
+       }
        return 0;
 
 err_flow_free:
@@ -936,7 +960,7 @@ static int ovs_flow_cmd_get(struct sk_buff *skb, struct genl_info *info)
                goto unlock;
        }
 
-       reply = ovs_flow_cmd_build_info(flow, dp, info, OVS_FLOW_CMD_NEW);
+       reply = ovs_flow_cmd_build_info(flow, dp, info, OVS_FLOW_CMD_NEW, true);
        if (IS_ERR(reply)) {
                err = PTR_ERR(reply);
                goto unlock;
@@ -983,22 +1007,26 @@ static int ovs_flow_cmd_del(struct sk_buff *skb, struct genl_info *info)
                goto unlock;
        }
 
-       reply = ovs_flow_cmd_alloc_info(flow, info);
-       if (!reply) {
-               err = -ENOMEM;
+       reply = ovs_flow_cmd_alloc_info(flow, info, false);
+       if (IS_ERR(reply)) {
+               err = PTR_ERR(reply);
                goto unlock;
        }
 
        ovs_flow_tbl_remove(&dp->table, flow);
 
-       err = ovs_flow_cmd_fill_info(flow, dp, reply, info->snd_portid,
-                                    info->snd_seq, 0, OVS_FLOW_CMD_DEL);
-       BUG_ON(err < 0);
+       if (reply) {
+               err = ovs_flow_cmd_fill_info(flow, dp, reply, info->snd_portid,
+                                            info->snd_seq, 0,
+                                            OVS_FLOW_CMD_DEL);
+               BUG_ON(err < 0);
+       }
 
        ovs_flow_free(flow, true);
        ovs_unlock();
 
-       ovs_notify(reply, info, &ovs_dp_flow_multicast_group);
+       if (reply)
+               ovs_notify(reply, info, &ovs_dp_flow_multicast_group);
        return 0;
 unlock:
        ovs_unlock();