RE: [EXT] Re: [v3,net-next 1/4] net: qos: introduce a gate control flow action

[Po Liu]

> -----Original Message-----
> From: Vlad Buslov <vlad@xxxxxxxxxx>
> Sent: 2020å4æ23æ 15:43
> To: Po Liu <po.liu@xxxxxxx>
> Cc: Vlad Buslov <vlad@xxxxxxxxxx>; davem@xxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx;
> vinicius.gomes@xxxxxxxxx; Claudiu Manoil <claudiu.manoil@xxxxxxx>;
> Vladimir Oltean <vladimir.oltean@xxxxxxx>; Alexandru Marginean
> <alexandru.marginean@xxxxxxx>; michael.chan@xxxxxxxxxxxx;
> vishal@xxxxxxxxxxx; saeedm@xxxxxxxxxxxx; leon@xxxxxxxxxx;
> jiri@xxxxxxxxxxxx; idosch@xxxxxxxxxxxx;
> alexandre.belloni@xxxxxxxxxxx; UNGLinuxDriver@xxxxxxxxxxxxx;
> kuba@xxxxxxxxxx; jhs@xxxxxxxxxxxx; xiyou.wangcong@xxxxxxxxx;
> simon.horman@xxxxxxxxxxxxx; pablo@xxxxxxxxxxxxx;
> moshe@xxxxxxxxxxxx; m-karicheri2@xxxxxx;
> andre.guedes@xxxxxxxxxxxxxxx; stephen@xxxxxxxxxxxxxxxxxx
> Subject: Re: [EXT] Re: [v3,net-next 1/4] net: qos: introduce a gate control
> flow action
> 
> Caution: EXT Email
> 
> On Thu 23 Apr 2020 at 06:14, Po Liu <po.liu@xxxxxxx> wrote:
> > Hi Vlad Buslov,
> >
> >> -----Original Message-----
> >> From: Vlad Buslov <vlad@xxxxxxxxxx>
> >> Sent: 2020å4æ22æ 21:23
> >> To: Po Liu <po.liu@xxxxxxx>
> >> Cc: davem@xxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> >> netdev@xxxxxxxxxxxxxxx; vinicius.gomes@xxxxxxxxx; Claudiu Manoil
> >> <claudiu.manoil@xxxxxxx>; Vladimir Oltean
> <vladimir.oltean@xxxxxxx>;
> >> Alexandru Marginean <alexandru.marginean@xxxxxxx>;
> >> michael.chan@xxxxxxxxxxxx; vishal@xxxxxxxxxxx;
> saeedm@xxxxxxxxxxxx;
> >> leon@xxxxxxxxxx; jiri@xxxxxxxxxxxx; idosch@xxxxxxxxxxxx;
> >> alexandre.belloni@xxxxxxxxxxx; UNGLinuxDriver@xxxxxxxxxxxxx;
> >> kuba@xxxxxxxxxx; jhs@xxxxxxxxxxxx; xiyou.wangcong@xxxxxxxxx;
> >> simon.horman@xxxxxxxxxxxxx; pablo@xxxxxxxxxxxxx;
> moshe@xxxxxxxxxxxx;
> >> m-karicheri2@xxxxxx; andre.guedes@xxxxxxxxxxxxxxx;
> >> stephen@xxxxxxxxxxxxxxxxxx
> >> Subject: [EXT] Re: [v3,net-next 1/4] net: qos: introduce a gate
> >> control flow action
> >>
> >> Caution: EXT Email
> >>
> >> Hi Po,
> >>
> >> On Wed 22 Apr 2020 at 05:48, Po Liu <Po.Liu@xxxxxxx> wrote:
> >> > Introduce a ingress frame gate control flow action.
> >> > Tc gate action does the work like this:
> >> > Assume there is a gate allow specified ingress frames can be passed
> >> > at specific time slot, and be dropped at specific time slot. Tc
> >> > filter chooses the ingress frames, and tc gate action would specify
> >> > what slot does these frames can be passed to device and what time
> >> > slot would be dropped.
> >> > Tc gate action would provide an entry list to tell how much time
> >> > gate keep open and how much time gate keep state close. Gate
> action
> >> > also assign a start time to tell when the entry list start. Then
> >> > driver would repeat the gate entry list cyclically.
> >> > For the software simulation, gate action requires the user assign a
> >> > time clock type.
> >> >
> >> > Below is the setting example in user space. Tc filter a stream
> >> > source ip address is 192.168.0.20 and gate action own two time
> >> > slots. One is last 200ms gate open let frame pass another is last
> >> > 100ms gate close let frames dropped. When the frames have passed
> >> > total frames over
> >> > 8000000 bytes, frames will be dropped in one 200000000ns time slot.
> >> >
> >> >> tc qdisc add dev eth0 ingress
> >> >
> >> >> tc filter add dev eth0 parent ffff: protocol ip \
> >> >          flower src_ip 192.168.0.20 \
> >> >          action gate index 2 clockid CLOCK_TAI \
> >> >          sched-entry open 200000000 -1 8000000 \
> >> >          sched-entry close 100000000 -1 -1
> >> >
> >> >> tc chain del dev eth0 ingress chain 0
> >> >
> >> > "sched-entry" follow the name taprio style. Gate state is
> >> > "open"/"close". Follow with period nanosecond. Then next item is
> >> > internal priority value means which ingress queue should put. "-1"
> >> > means wildcard. The last value optional specifies the maximum
> >> > number of MSDU octets that are permitted to pass the gate during
> >> > the specified time interval.
> >> > Base-time is not set will be 0 as default, as result start time
> >> > would be ((N + 1) * cycletime) which is the minimal of future time.
> >> >
> >> > Below example shows filtering a stream with destination mac address
> >> > is
> >> > 10:00:80:00:00:00 and ip type is ICMP, follow the action gate. The
> >> > gate action would run with one close time slot which means always
> >> > keep
> >> close.
> >> > The time cycle is total 200000000ns. The base-time would calculate by:
> >> >
> >> >  1357000000000 + (N + 1) * cycletime
> >> >
> >> > When the total value is the future time, it will be the start time.
> >> > The cycletime here would be 200000000ns for this case.
> >> >
> >> >> tc filter add dev eth0 parent ffff:  protocol ip \
> >> >          flower skip_hw ip_proto icmp dst_mac 10:00:80:00:00:00 \
> >> >          action gate index 12 base-time 1357000000000 \
> >> >          sched-entry close 200000000 -1 -1 \
> >> >          clockid CLOCK_TAI
> >> >
> >> > Signed-off-by: Po Liu <Po.Liu@xxxxxxx>
> >> > ---
> >> >  include/net/tc_act/tc_gate.h        |  54 +++
> >> >  include/uapi/linux/pkt_cls.h        |   1 +
> >> >  include/uapi/linux/tc_act/tc_gate.h |  47 ++
> >> >  net/sched/Kconfig                   |  13 +
> >> >  net/sched/Makefile                  |   1 +
> >> >  net/sched/act_gate.c                | 647
> ++++++++++++++++++++++++++++
> >> >  6 files changed, 763 insertions(+)  create mode 100644
> >> > include/net/tc_act/tc_gate.h  create mode 100644
> >> > include/uapi/linux/tc_act/tc_gate.h
> >> >  create mode 100644 net/sched/act_gate.c
> >> >
> >> > diff --git a/include/net/tc_act/tc_gate.h
> >> > b/include/net/tc_act/tc_gate.h new file mode 100644 index
> >> > 000000000000..b0ace55b2aaa
> >> > --- /dev/null
> >> > +++ b/include/net/tc_act/tc_gate.h
> >> > @@ -0,0 +1,54 @@
> >> > +/* SPDX-License-Identifier: GPL-2.0-or-later */
> >> > +/* Copyright 2020 NXP */
> >> > +
> >> > +#ifndef __NET_TC_GATE_H
> >> > +#define __NET_TC_GATE_H
> >> > +
> >> > +#include <net/act_api.h>
> >> > +#include <linux/tc_act/tc_gate.h>
> >> > +
> >> > +struct tcfg_gate_entry {
> >> > +     int                     index;
> >> > +     u8                      gate_state;
> >> > +     u32                     interval;
> >> > +     s32                     ipv;
> >> > +     s32                     maxoctets;
> >> > +     struct list_head        list;
> >> > +};
> >> > +
> >> > +struct tcf_gate_params {
> >> > +     s32                     tcfg_priority;
> >> > +     u64                     tcfg_basetime;
> >> > +     u64                     tcfg_cycletime;
> >> > +     u64                     tcfg_cycletime_ext;
> >> > +     u32                     tcfg_flags;
> >> > +     s32                     tcfg_clockid;
> >> > +     size_t                  num_entries;
> >> > +     struct list_head        entries;
> >> > +};
> >> > +
> >> > +#define GATE_ACT_GATE_OPEN   BIT(0)
> >> > +#define GATE_ACT_PENDING     BIT(1)
> >> > +struct gate_action {
> >> > +     struct tcf_gate_params param;
> >> > +     spinlock_t entry_lock;
> >> > +     u8 current_gate_status;
> >> > +     ktime_t current_close_time;
> >> > +     u32 current_entry_octets;
> >> > +     s32 current_max_octets;
> >> > +     struct tcfg_gate_entry __rcu *next_entry;
> >> > +     struct hrtimer hitimer;
> >> > +     enum tk_offsets tk_offset;
> >> > +     struct rcu_head rcu;
> >> > +};
> >> > +
> >> > +struct tcf_gate {
> >> > +     struct tc_action                common;
> >> > +     struct gate_action __rcu        *actg;
> >> > +};
> >> > +#define to_gate(a) ((struct tcf_gate *)a)
> >> > +
> >> > +#define get_gate_param(act) ((struct tcf_gate_params *)act)
> >> > +#define
> >> > +get_gate_action(p) ((struct gate_action *)p)
> >> > +
> >> > +#endif
> >> > diff --git a/include/uapi/linux/pkt_cls.h
> >> > b/include/uapi/linux/pkt_cls.h index 9f06d29cab70..fc672b232437
> >> 100644
> >> > --- a/include/uapi/linux/pkt_cls.h
> >> > +++ b/include/uapi/linux/pkt_cls.h
> >> > @@ -134,6 +134,7 @@ enum tca_id {
> >> >       TCA_ID_CTINFO,
> >> >       TCA_ID_MPLS,
> >> >       TCA_ID_CT,
> >> > +     TCA_ID_GATE,
> >> >       /* other actions go here */
> >> >       __TCA_ID_MAX = 255
> >> >  };
> >> > diff --git a/include/uapi/linux/tc_act/tc_gate.h
> >> > b/include/uapi/linux/tc_act/tc_gate.h
> >> > new file mode 100644
> >> > index 000000000000..f214b3a6d44f
> >> > --- /dev/null
> >> > +++ b/include/uapi/linux/tc_act/tc_gate.h
> >> > @@ -0,0 +1,47 @@
> >> > +/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
> >> > +/* Copyright 2020 NXP */
> >> > +
> >> > +#ifndef __LINUX_TC_GATE_H
> >> > +#define __LINUX_TC_GATE_H
> >> > +
> >> > +#include <linux/pkt_cls.h>
> >> > +
> >> > +struct tc_gate {
> >> > +     tc_gen;
> >> > +};
> >> > +
> >> > +enum {
> >> > +     TCA_GATE_ENTRY_UNSPEC,
> >> > +     TCA_GATE_ENTRY_INDEX,
> >> > +     TCA_GATE_ENTRY_GATE,
> >> > +     TCA_GATE_ENTRY_INTERVAL,
> >> > +     TCA_GATE_ENTRY_IPV,
> >> > +     TCA_GATE_ENTRY_MAX_OCTETS,
> >> > +     __TCA_GATE_ENTRY_MAX,
> >> > +};
> >> > +#define TCA_GATE_ENTRY_MAX (__TCA_GATE_ENTRY_MAX - 1)
> >> > +
> >> > +enum {
> >> > +     TCA_GATE_ONE_ENTRY_UNSPEC,
> >> > +     TCA_GATE_ONE_ENTRY,
> >> > +     __TCA_GATE_ONE_ENTRY_MAX,
> >> > +};
> >> > +#define TCA_GATE_ONE_ENTRY_MAX
> (__TCA_GATE_ONE_ENTRY_MAX
> >> - 1)
> >> > +
> >> > +enum {
> >> > +     TCA_GATE_UNSPEC,
> >> > +     TCA_GATE_TM,
> >> > +     TCA_GATE_PARMS,
> >> > +     TCA_GATE_PAD,
> >> > +     TCA_GATE_PRIORITY,
> >> > +     TCA_GATE_ENTRY_LIST,
> >> > +     TCA_GATE_BASE_TIME,
> >> > +     TCA_GATE_CYCLE_TIME,
> >> > +     TCA_GATE_CYCLE_TIME_EXT,
> >> > +     TCA_GATE_FLAGS,
> >> > +     TCA_GATE_CLOCKID,
> >> > +     __TCA_GATE_MAX,
> >> > +};
> >> > +#define TCA_GATE_MAX (__TCA_GATE_MAX - 1)
> >> > +
> >> > +#endif
> >> > diff --git a/net/sched/Kconfig b/net/sched/Kconfig index
> >> > bfbefb7bff9d..1314549c7567 100644
> >> > --- a/net/sched/Kconfig
> >> > +++ b/net/sched/Kconfig
> >> > @@ -981,6 +981,19 @@ config NET_ACT_CT
> >> >         To compile this code as a module, choose M here: the
> >> >         module will be called act_ct.
> >> >
> >> > +config NET_ACT_GATE
> >> > +     tristate "Frame gate entry list control tc action"
> >> > +     depends on NET_CLS_ACT
> >> > +     help
> >> > +       Say Y here to allow to control the ingress flow to be passed at
> >> > +       specific time slot and be dropped at other specific time slot by
> >> > +       the gate entry list. The manipulation will simulate the IEEE
> >> > +       802.1Qci stream gate control behavior.
> >> > +
> >> > +       If unsure, say N.
> >> > +       To compile this code as a module, choose M here: the
> >> > +       module will be called act_gate.
> >> > +
> >> >  config NET_IFE_SKBMARK
> >> >       tristate "Support to encoding decoding skb mark on IFE action"
> >> >       depends on NET_ACT_IFE
> >> > diff --git a/net/sched/Makefile b/net/sched/Makefile index
> >> > 31c367a6cd09..66bbf9a98f9e 100644
> >> > --- a/net/sched/Makefile
> >> > +++ b/net/sched/Makefile
> >> > @@ -30,6 +30,7 @@ obj-$(CONFIG_NET_IFE_SKBPRIO)       +=
> >> act_meta_skbprio.o
> >> >  obj-$(CONFIG_NET_IFE_SKBTCINDEX)     += act_meta_skbtcindex.o
> >> >  obj-$(CONFIG_NET_ACT_TUNNEL_KEY)+= act_tunnel_key.o
> >> >  obj-$(CONFIG_NET_ACT_CT)     += act_ct.o
> >> > +obj-$(CONFIG_NET_ACT_GATE)   += act_gate.o
> >> >  obj-$(CONFIG_NET_SCH_FIFO)   += sch_fifo.o
> >> >  obj-$(CONFIG_NET_SCH_CBQ)    += sch_cbq.o
> >> >  obj-$(CONFIG_NET_SCH_HTB)    += sch_htb.o
> >> > diff --git a/net/sched/act_gate.c b/net/sched/act_gate.c new file
> >> > mode
> >> > 100644 index 000000000000..e932f402b4f1
> >> > --- /dev/null
> >> > +++ b/net/sched/act_gate.c
> >> > @@ -0,0 +1,647 @@
> >> > +// SPDX-License-Identifier: GPL-2.0-or-later
> >> > +/* Copyright 2020 NXP */
> >> > +
> >> > +#include <linux/module.h>
> >> > +#include <linux/types.h>
> >> > +#include <linux/kernel.h>
> >> > +#include <linux/string.h>
> >> > +#include <linux/errno.h>
> >> > +#include <linux/skbuff.h>
> >> > +#include <linux/rtnetlink.h>
> >> > +#include <linux/init.h>
> >> > +#include <linux/slab.h>
> >> > +#include <net/act_api.h>
> >> > +#include <net/netlink.h>
> >> > +#include <net/pkt_cls.h>
> >> > +#include <net/tc_act/tc_gate.h>
> >> > +
> >> > +static unsigned int gate_net_id;
> >> > +static struct tc_action_ops act_gate_ops;
> >> > +
> >> > +static ktime_t gate_get_time(struct gate_action *gact) {
> >> > +     ktime_t mono = ktime_get();
> >> > +
> >> > +     switch (gact->tk_offset) {
> >> > +     case TK_OFFS_MAX:
> >> > +             return mono;
> >> > +     default:
> >> > +             return ktime_mono_to_any(mono, gact->tk_offset);
> >> > +     }
> >> > +
> >> > +     return KTIME_MAX;
> >> > +}
> >> > +
> >> > +static int gate_get_start_time(struct gate_action *gact, ktime_t
> >> > +*start) {
> >> > +     struct tcf_gate_params *param = get_gate_param(gact);
> >> > +     ktime_t now, base, cycle;
> >> > +     u64 n;
> >> > +
> >> > +     base = ns_to_ktime(param->tcfg_basetime);
> >> > +     now = gate_get_time(gact);
> >> > +
> >> > +     if (ktime_after(base, now)) {
> >> > +             *start = base;
> >> > +             return 0;
> >> > +     }
> >> > +
> >> > +     cycle = param->tcfg_cycletime;
> >> > +
> >> > +     /* cycle time should not be zero */
> >> > +     if (WARN_ON(!cycle))
> >> > +             return -EFAULT;
> >>
> >> Looking at the init code it seems that this value can be set to 0
> >> directly from netlink packet without further validation, which would
> >> allow user to trigger warning here.
> >
> > Yes,  will avoid at ahead point.
> >
> >>
> >> > +
> >> > +     n = div64_u64(ktime_sub_ns(now, base), cycle);
> >> > +     *start = ktime_add_ns(base, (n + 1) * cycle);
> >> > +     return 0;
> >> > +}
> >> > +
> >> > +static void gate_start_timer(struct gate_action *gact, ktime_t
> >> > +start) {
> >> > +     ktime_t expires;
> >> > +
> >> > +     expires = hrtimer_get_expires(&gact->hitimer);
> >> > +     if (expires == 0)
> >> > +             expires = KTIME_MAX;
> >> > +
> >> > +     start = min_t(ktime_t, start, expires);
> >> > +
> >> > +     hrtimer_start(&gact->hitimer, start, HRTIMER_MODE_ABS); }
> >> > +
> >> > +static enum hrtimer_restart gate_timer_func(struct hrtimer *timer) {
> >> > +     struct gate_action *gact = container_of(timer, struct gate_action,
> >> > +                                             hitimer);
> >> > +     struct tcf_gate_params *p = get_gate_param(gact);
> >> > +     struct tcfg_gate_entry *next;
> >> > +     ktime_t close_time, now;
> >> > +
> >> > +     spin_lock(&gact->entry_lock);
> >> > +
> >> > +     next = rcu_dereference_protected(gact->next_entry,
> >> > +
> >> > + lockdep_is_held(&gact->entry_lock));
> >> > +
> >> > +     /* cycle start, clear pending bit, clear total octets */
> >> > +     gact->current_gate_status = next->gate_state ?
> >> GATE_ACT_GATE_OPEN : 0;
> >> > +     gact->current_entry_octets = 0;
> >> > +     gact->current_max_octets = next->maxoctets;
> >> > +
> >> > +     gact->current_close_time = ktime_add_ns(gact-
> >current_close_time,
> >> > +                                             next->interval);
> >> > +
> >> > +     close_time = gact->current_close_time;
> >> > +
> >> > +     if (list_is_last(&next->list, &p->entries))
> >> > +             next = list_first_entry(&p->entries,
> >> > +                                     struct tcfg_gate_entry, list);
> >> > +     else
> >> > +             next = list_next_entry(next, list);
> >> > +
> >> > +     now = gate_get_time(gact);
> >> > +
> >> > +     if (ktime_after(now, close_time)) {
> >> > +             ktime_t cycle, base;
> >> > +             u64 n;
> >> > +
> >> > +             cycle = p->tcfg_cycletime;
> >> > +             base = ns_to_ktime(p->tcfg_basetime);
> >> > +             n = div64_u64(ktime_sub_ns(now, base), cycle);
> >> > +             close_time = ktime_add_ns(base, (n + 1) * cycle);
> >> > +     }
> >> > +
> >> > +     rcu_assign_pointer(gact->next_entry, next);
> >> > +     spin_unlock(&gact->entry_lock);
> >>
> >> I have couple of question about synchronization here:
> >>
> >> - Why do you need next_entry to be rcu pointer? It is only assigned
> >> here with entry_lock protection and in init code before action is
> >> visible to concurrent users. I don't see any unlocked rcu-protected
> >> readers here that could benefit from it.
> >>
> >> - Why create dedicated entry_lock instead of using already existing
> >> per- action tcf_lock?
> >
> > Will try to use the tcf_lock for verification.
> > The thoughts came from that the timer period arrived then check
> > through the list and then update next time would take much more time.
> > Action function would be busy when traffic. So use a separate lock
> > here for
> >
> >>
> >> > +
> >> > +     hrtimer_set_expires(&gact->hitimer, close_time);
> >> > +
> >> > +     return HRTIMER_RESTART;
> >> > +}
> >> > +
> >> > +static int tcf_gate_act(struct sk_buff *skb, const struct tc_action *a,
> >> > +                     struct tcf_result *res) {
> >> > +     struct tcf_gate *g = to_gate(a);
> >> > +     struct gate_action *gact;
> >> > +     int action;
> >> > +
> >> > +     tcf_lastuse_update(&g->tcf_tm);
> >> > +     bstats_cpu_update(this_cpu_ptr(g->common.cpu_bstats), skb);
> >> > +
> >> > +     action = READ_ONCE(g->tcf_action);
> >> > +     rcu_read_lock();
> >>
> >> Action fastpath is already rcu read lock protected, you don't need to
> >> manually obtain it.
> >
> > Will be removed.
> >
> >>
> >> > +     gact = rcu_dereference_bh(g->actg);
> >> > +     if (unlikely(gact->current_gate_status & GATE_ACT_PENDING)) {
> >>
> >> Can't current_gate_status be concurrently modified by timer callback?
> >> This function doesn't use entry_lock to synchronize with timer.
> >
> > Will try tcf_lock either.
> >
> >>
> >> > +             rcu_read_unlock();
> >> > +             return action;
> >> > +     }
> >> > +
> >> > +     if (!(gact->current_gate_status & GATE_ACT_GATE_OPEN))
> >>
> >> ...and here
> >>
> >> > +             goto drop;
> >> > +
> >> > +     if (gact->current_max_octets >= 0) {
> >> > +             gact->current_entry_octets += qdisc_pkt_len(skb);
> >> > +             if (gact->current_entry_octets >
> >> > + gact->current_max_octets) {
> >>
> >> here also.
> >>
> >> > +
> >> > + qstats_overlimit_inc(this_cpu_ptr(g->common.cpu_qstats));
> >>
> >> Please use tcf_action_inc_overlimit_qstats() and other wrappers for
> stats.
> >> Otherwise it will crash if user passes
> TCA_ACT_FLAGS_NO_PERCPU_STATS
> >> flag.
> >
> > The tcf_action_inc_overlimit_qstats() can't show limit counts in tc show
> command. Is there anything need to do?
> 
> What do you mean? Internally tcf_action_inc_overlimit_qstats() just calls
> qstats_overlimit_inc, if cpu_qstats percpu counter is not NULL:
> 
> 
>         if (likely(a->cpu_qstats)) {
>                 qstats_overlimit_inc(this_cpu_ptr(a->cpu_qstats));
>                 return;
>         }
> 
> Is there a subtle bug somewhere in this function?

Sorry, I updated using the tcf_action_*, and the counting is ok. I moved back to the qstats_overlimit_inc() because tcf_action_* () include the spin_lock(&a->tcfa_lock). 
I would update to  tcf_action_* () increate. 

> 
> >
> > Br,
> > Po Liu

Thanks a lot.

Br,
Po Liu