Date:   Sun, 16 Apr 2017 09:56:13 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, xiyou.wangcong@...il.com,
        eric.dumazet@...il.com, jiri@...nulli.us,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: [PATCH net-next 1/1] net sched actions: add time filter for action dumping

From: Jamal Hadi Salim <jhs@...atatu.com>

This adds support for filtering based on time since last used.
When we are dumping a large number of actions it is useful to
have the option of filtering based on when the action was last
used to reduce the amount of data crossing to user space.

With this patch the user space app sets the FILTER_ACCESS_TIME flag
(in the pad1 flags area) and the "time of interest since now" in seconds
when the action was last used (in the pad2 area).  The kernel converts
this to jiffies and does the filtering comparison matching entries that
have seen activity since then and returns them to user space.
Old kernels and old tc continue to work in legacy mode.

Some example (we have 400 actions bound to 400 filters); at installation
time using  hacked tc which sets the time of interest to 120 seconds:

prompt$ hackedtc actions ls action gact | grep index | wc -l
400

go get some coffee and  wait for > 120 seconds and try again:

prompt$ hackedtc actions ls action gact | grep index | wc -l
0

Lets see a filter bound to one of these actions:
..
filter pref 10 u32
filter pref 10 u32 fh 800: ht divisor 1
filter pref 10 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:10  (rule hit 2 success 1)
  match 7f000002/ffffffff at 12 (success 1 )
	action order 1: gact action pass
	 random type none pass val 0
	 index 23 ref 2 bind 1 installed 1145 sec used 802 sec
 	Action statistics:
	Sent 84 bytes 1 pkt (dropped 0, overlimits 0 requeues 0)
	backlog 0b 0p requeues 0
....

Now lets ping -c 1 127.0.0.2, then run the actions again:

prompt$ hackedtc actions ls action gact | grep index | wc -l
1

More details please:

prompt$ hackedtc -s actions ls action gact
total acts 1 flags 0x3

	action order 0: gact action pass
	 random type none pass val 0
	 index 23 ref 2 bind 1 installed 1270 sec used 30 sec
 	Action statistics:
	Sent 168 bytes 2 pkt (dropped 0, overlimits 0 requeues 0)
	backlog 0b 0p requeues 0

And the filter?

filter pref 10 u32
filter pref 10 u32 fh 800: ht divisor 1
filter pref 10 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:10  (rule hit 4 success 2)
  match 7f000002/ffffffff at 12 (success 2 )
	action order 1: gact action pass
	 random type none pass val 0
	 index 23 ref 2 bind 1 installed 1324 sec used 84 sec
 	Action statistics:
	Sent 168 bytes 2 pkt (dropped 0, overlimits 0 requeues 0)
	backlog 0b 0p requeues 0

Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
---
 net/sched/act_api.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 90cc774..4dd55f2 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -84,11 +84,13 @@ static int tcf_dump_walker(struct tcf_hashinfo *hinfo, struct sk_buff *skb,
 {
 	int err = 0, index = -1, i = 0, s_i = 0, n_i = 0;
 	unsigned short act_flags = cb->args[2];
+	unsigned long jiffy_filter = cb->args[3];
+
 	struct nlattr *nest;
 
 	spin_lock_bh(&hinfo->lock);
 
-	s_i = cb->args[0];
+	s_i = cb->args[4];
 
 	for (i = 0; i < (hinfo->hmask + 1); i++) {
 		struct hlist_head *head;
@@ -101,6 +103,12 @@ static int tcf_dump_walker(struct tcf_hashinfo *hinfo, struct sk_buff *skb,
 			if (index < s_i)
 				continue;
 
+			if (jiffy_filter &&
+			    time_after(jiffy_filter,
+				       (unsigned long)p->tcfa_tm.lastuse)) {
+				continue;
+			}
+
 			nest = nla_nest_start(skb, n_i);
 			if (nest == NULL)
 				goto nla_put_failure;
@@ -118,6 +126,8 @@ static int tcf_dump_walker(struct tcf_hashinfo *hinfo, struct sk_buff *skb,
 		}
 	}
 done:
+	if (index > 0)
+		cb->args[4] = index + 1;
 	spin_unlock_bh(&hinfo->lock);
 	if (n_i) {
 		cb->args[0] += n_i;
@@ -1086,8 +1096,10 @@ static int tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
 	struct tc_action_ops *a_o;
 	int ret = 0;
 	struct tcamsg *t = (struct tcamsg *) nlmsg_data(cb->nlh);
-	unsigned char act_flags = t->tca__pad1;
 	struct nlattr *kind = find_dump_kind(cb->nlh);
+	unsigned char act_flags = t->tca__pad1;
+	unsigned short secs = t->tca__pad2;
+	unsigned long jiffy_wanted = 0;
 
 	if (kind == NULL) {
 		pr_info("tc_dump_action: action bad kind\n");
@@ -1103,7 +1115,15 @@ static int tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
 	if (!nlh)
 		goto out_module_put;
 
+	if (act_flags & ACT_FILTER_TIME_ACCESS) {
+		const unsigned int m = secs * 1000L;
+		unsigned long jiffy_msecs = msecs_to_jiffies(m);
+
+		jiffy_wanted = jiffies - jiffy_msecs;
+	}
+
 	cb->args[2] = act_flags;
+	cb->args[3] = jiffy_wanted;
 
 	t = nlmsg_data(nlh);
 	t->tca_family = AF_UNSPEC;
-- 
1.9.1

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