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Message-ID: <Y8jEpg+8KSxTLFPF@t14s.localdomain>
Date: Thu, 19 Jan 2023 01:18:46 -0300
From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To: Vlad Buslov <vladbu@...dia.com>
Cc: davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
pablo@...filter.org, netdev@...r.kernel.org,
netfilter-devel@...r.kernel.org, jhs@...atatu.com,
xiyou.wangcong@...il.com, jiri@...nulli.us, ozsh@...dia.com,
simon.horman@...igine.com
Subject: Re: [PATCH net-next v2 6/7] net/sched: act_ct: offload UDP NEW
connections
On Tue, Jan 17, 2023 at 09:12:26PM +0200, Vlad Buslov wrote:
> On Tue 17 Jan 2023 at 14:56, Marcelo Ricardo Leitner <marcelo.leitner@...il.com> wrote:
> > On Tue, Jan 17, 2023 at 07:36:42PM +0200, Vlad Buslov wrote:
> >>
> >> On Tue 17 Jan 2023 at 12:41, Marcelo Ricardo Leitner <marcelo.leitner@...il.com> wrote:
> >> > On Fri, Jan 13, 2023 at 05:55:47PM +0100, Vlad Buslov wrote:
> >> >> When processing connections allow offloading of UDP connections that don't
> >> >> have IPS_ASSURED_BIT set as unidirectional. When performing table lookup
> >> >
> >> > Hmm. Considering that this is now offloading one direction only
> >> > already, what about skipping this grace period:
> >> >
> >> > In nf_conntrack_udp_packet(), it does:
> >> >
> >> > /* If we've seen traffic both ways, this is some kind of UDP
> >> > * stream. Set Assured.
> >> > */
> >> > if (test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {
> >> > ...
> >> > /* Still active after two seconds? Extend timeout. */
> >> > if (time_after(jiffies, ct->proto.udp.stream_ts)) {
> >> > extra = timeouts[UDP_CT_REPLIED];
> >> > stream = true;
> >> > }
> >> > ...
> >> > /* Also, more likely to be important, and not a probe */
> >> > if (stream && !test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
> >> > nf_conntrack_event_cache(IPCT_ASSURED, ct);
> >> >
> >> > Maybe the patch should be relying on IPS_SEEN_REPLY_BIT instead of
> >> > ASSURED for UDP? Just a thought here, but I'm not seeing why not.
> >>
> >> The issue with this is that if we offload both directions early, then
> >> conntrack state machine will not receive any more packets and,
> >> consecutively, will never change the flow state to assured. I guess that
> >
> > I'm missing how it would offload each direction independently.
> > Wouldn't CT state machine see the 1st reply, because it is not
> > offloaded yet, and match it to the original direction?
>
(ok, better reply this too instead of radio silence)
> What I meant is that if both directions are offloaded as soon as
> IPS_SEEN_REPLY_BIT is set, then nf_conntrack_udp_packet() will not be
> called for that connection anymore and would never be able to transition
> the connection to assured state. But main thing is, as I said in the
Oh, right!
> previous reply, that we don't need to offload such connection ATM. It
> could be done in a follow-up if there is a use-case for it, maybe even
> made somehow configurable (with BPF! :)), so it could be dynamically
> controlled.
>
> >
> >> could be mitigated somehow by periodically checking the hw stats and
> >> transitioning the flow to assured based on them, but as I said in
> >> previous email we don't want to over-complicate this series even more.
> >> Also, offloading to hardware isn't free and costs both memory and CPU,
> >> so it is not like offloading as early as possible is strictly beneficial
> >> for all cases...
> >
> > Yup.
> >
> >>
> >> >
> >> >> for reply packets check the current connection status: If UDP
> >> >> unidirectional connection became assured also promote the corresponding
> >> >> flow table entry to bidirectional and set the 'update' bit, else just set
> >> >> the 'update' bit since reply directional traffic will most likely cause
> >> >> connection status to become 'established' which requires updating the
> >> >> offload state.
> >> >>
> >> >> Signed-off-by: Vlad Buslov <vladbu@...dia.com>
> >> >> ---
> >> >> net/sched/act_ct.c | 48 ++++++++++++++++++++++++++++++++++------------
> >> >> 1 file changed, 36 insertions(+), 12 deletions(-)
> >> >>
> >> >> diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
> >> >> index bfddb462d2bc..563cbdd8341c 100644
> >> >> --- a/net/sched/act_ct.c
> >> >> +++ b/net/sched/act_ct.c
> >> >> @@ -369,7 +369,7 @@ static void tcf_ct_flow_tc_ifidx(struct flow_offload *entry,
> >> >>
> >> >> static void tcf_ct_flow_table_add(struct tcf_ct_flow_table *ct_ft,
> >> >> struct nf_conn *ct,
> >> >> - bool tcp)
> >> >> + bool tcp, bool bidirectional)
> >> >> {
> >> >> struct nf_conn_act_ct_ext *act_ct_ext;
> >> >> struct flow_offload *entry;
> >> >> @@ -388,6 +388,8 @@ static void tcf_ct_flow_table_add(struct tcf_ct_flow_table *ct_ft,
> >> >> ct->proto.tcp.seen[0].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
> >> >> ct->proto.tcp.seen[1].flags |= IP_CT_TCP_FLAG_BE_LIBERAL;
> >> >> }
> >> >> + if (bidirectional)
> >> >> + __set_bit(NF_FLOW_HW_BIDIRECTIONAL, &entry->flags);
> >> >>
> >> >> act_ct_ext = nf_conn_act_ct_ext_find(ct);
> >> >> if (act_ct_ext) {
> >> >> @@ -411,26 +413,34 @@ static void tcf_ct_flow_table_process_conn(struct tcf_ct_flow_table *ct_ft,
> >> >> struct nf_conn *ct,
> >> >> enum ip_conntrack_info ctinfo)
> >> >> {
> >> >> - bool tcp = false;
> >> >> -
> >> >> - if ((ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) ||
> >> >> - !test_bit(IPS_ASSURED_BIT, &ct->status))
> >> >> - return;
> >> >> + bool tcp = false, bidirectional = true;
> >> >>
> >> >> switch (nf_ct_protonum(ct)) {
> >> >> case IPPROTO_TCP:
> >> >> - tcp = true;
> >> >> - if (ct->proto.tcp.state != TCP_CONNTRACK_ESTABLISHED)
> >> >> + if ((ctinfo != IP_CT_ESTABLISHED &&
> >> >> + ctinfo != IP_CT_ESTABLISHED_REPLY) ||
> >> >> + !test_bit(IPS_ASSURED_BIT, &ct->status) ||
> >> >> + ct->proto.tcp.state != TCP_CONNTRACK_ESTABLISHED)
> >> >> return;
> >> >> +
> >> >> + tcp = true;
> >> >> break;
> >> >> case IPPROTO_UDP:
> >> >> + if (!nf_ct_is_confirmed(ct))
> >> >> + return;
> >> >> + if (!test_bit(IPS_ASSURED_BIT, &ct->status))
> >> >> + bidirectional = false;
> >> >> break;
> >> >> #ifdef CONFIG_NF_CT_PROTO_GRE
> >> >> case IPPROTO_GRE: {
> >> >> struct nf_conntrack_tuple *tuple;
> >> >>
> >> >> - if (ct->status & IPS_NAT_MASK)
> >> >> + if ((ctinfo != IP_CT_ESTABLISHED &&
> >> >> + ctinfo != IP_CT_ESTABLISHED_REPLY) ||
> >> >> + !test_bit(IPS_ASSURED_BIT, &ct->status) ||
> >> >> + ct->status & IPS_NAT_MASK)
> >> >> return;
> >> >> +
> >> >> tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
> >> >> /* No support for GRE v1 */
> >> >> if (tuple->src.u.gre.key || tuple->dst.u.gre.key)
> >> >> @@ -446,7 +456,7 @@ static void tcf_ct_flow_table_process_conn(struct tcf_ct_flow_table *ct_ft,
> >> >> ct->status & IPS_SEQ_ADJUST)
> >> >> return;
> >> >>
> >> >> - tcf_ct_flow_table_add(ct_ft, ct, tcp);
> >> >> + tcf_ct_flow_table_add(ct_ft, ct, tcp, bidirectional);
> >> >> }
> >> >>
> >> >> static bool
> >> >> @@ -625,13 +635,27 @@ static bool tcf_ct_flow_table_lookup(struct tcf_ct_params *p,
> >> >> flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
> >> >> ct = flow->ct;
> >> >>
> >> >> + if (dir == FLOW_OFFLOAD_DIR_REPLY &&
> >> >> + !test_bit(NF_FLOW_HW_BIDIRECTIONAL, &flow->flags)) {
> >> >> + /* Only offload reply direction after connection became
> >> >> + * assured.
> >> >> + */
> >> >> + if (test_bit(IPS_ASSURED_BIT, &ct->status))
> >> >> + set_bit(NF_FLOW_HW_BIDIRECTIONAL, &flow->flags);
> >> >> + set_bit(NF_FLOW_HW_UPDATE, &flow->flags);
> >> >> + return false;
> >> >> + }
> >> >> +
> >> >> if (tcph && (unlikely(tcph->fin || tcph->rst))) {
> >> >> flow_offload_teardown(flow);
> >> >> return false;
> >> >> }
> >> >>
> >> >> - ctinfo = dir == FLOW_OFFLOAD_DIR_ORIGINAL ? IP_CT_ESTABLISHED :
> >> >> - IP_CT_ESTABLISHED_REPLY;
> >> >> + if (dir == FLOW_OFFLOAD_DIR_ORIGINAL)
> >> >> + ctinfo = test_bit(IPS_SEEN_REPLY_BIT, &ct->status) ?
> >> >> + IP_CT_ESTABLISHED : IP_CT_NEW;
> >> >> + else
> >> >> + ctinfo = IP_CT_ESTABLISHED_REPLY;
> >> >>
> >> >> flow_offload_refresh(nf_ft, flow);
> >> >> nf_conntrack_get(&ct->ct_general);
> >> >> --
> >> >> 2.38.1
> >> >>
> >>
>
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