[PATCH net-next v4 2/2] net sched actions: add time filter for action dumping

Jamal Hadi Salim
2017-04-19T11:57:45Z

From: Jamal Hadi Salim <jhs@mojatatu.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 TCAA_ACT_TIME_FILTER
attribute with the value in milliseconds with "time of interest
since now". 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 since
they dont specify this attribute.

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
....

that coffee took long, no? It was good.

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

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@mojatatu.com>
---
include/uapi/linux/rtnetlink.h | 1 +
net/sched/act_api.c | 25 +++++++++++++++++++++++--
2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index c7080ec..1b36cc0 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -680,6 +680,7 @@ enum {
TCAA_ACT_TAB,
TCAA_ACT_FLAGS,
TCAA_ACT_COUNT,
+ TCAA_ACT_TIME_FILTER,
__TCAA_MAX
};

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 45e1cf7..b03863a 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -84,11 +84,12 @@ 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 +102,11 @@ 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 +124,9 @@ 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;
@@ -1000,6 +1009,7 @@ static int tcf_action_add(struct net *net, struct nlattr *nla,

static const struct nla_policy tcaa_policy[TCAA_MAX + 1] = {
[TCAA_ACT_FLAGS] = { .type = NLA_U32 },
+ [TCAA_ACT_TIME_FILTER] = { .type = NLA_U32 },
};

static int tc_ctl_action(struct sk_buff *skb, struct nlmsghdr *n,
@@ -1090,13 +1100,14 @@ static int tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
struct tcamsg *t = (struct tcamsg *) nlmsg_data(cb->nlh);
struct nlattr *kind = NULL;
u32 act_flags = 0;
+ u32 msecs_filter = 0;
+ unsigned long jiffy_wanted = 0;

ret = nlmsg_parse(cb->nlh, sizeof(struct tcamsg), tcaa, TCAA_MAX,
tcaa_policy, NULL);
if (ret < 0)
return ret;

-
kind = find_dump_kind(tcaa);
if (kind == NULL) {
pr_info("tc_dump_action: action bad kind\n");
@@ -1110,12 +1121,22 @@ static int tc_dump_action(struct sk_buff *skb, struct netlink_callback *cb)
if (tcaa[TCAA_ACT_FLAGS])
act_flags = nla_get_u32(tcaa[TCAA_ACT_FLAGS]);

+ if (tcaa[TCAA_ACT_TIME_FILTER])
+ msecs_filter = nla_get_u32(tcaa[TCAA_ACT_TIME_FILTER]);
+
nlh = nlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
cb->nlh->nlmsg_type, sizeof(*t), 0);
if (!nlh)
goto out_module_put;

+ if (msecs_filter) {
+ unsigned long jiffy_msecs = msecs_to_jiffies(msecs_filter);
+
+ 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