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fq_codel: generalise ce_threshold marking for subset of traffic

Browse source 
Commit e72aeb9ee0 ("fq_codel: implement L4S style ce_threshold_ect1
marking") expanded the ce_threshold feature of FQ-CoDel so it can
be applied to a subset of the traffic, using the ECT(1) bit of the ECN
field as the classifier. However, hard-coding ECT(1) as the only
classifier for this feature seems limiting, so let's expand it to be more
general.

To this end, change the parameter from a ce_threshold_ect1 boolean, to a
one-byte selector/mask pair (ce_threshold_{selector,mask}) which is applied
to the whole diffserv/ECN field in the IP header. This makes it possible to
classify packets by any value in either the ECN field or the diffserv
field. In particular, setting a selector of INET_ECN_ECT_1 and a mask of
INET_ECN_MASK corresponds to the functionality before this patch, and a
mask of ~INET_ECN_MASK allows using the selector as a straight-forward
match against a diffserv code point:

 # apply ce_threshold to ECT(1) traffic
 tc qdisc replace dev eth0 root fq_codel ce_threshold 1ms ce_threshold_selector 0x1/0x3

 # apply ce_threshold to ECN-capable traffic marked as diffserv AF22
 tc qdisc replace dev eth0 root fq_codel ce_threshold 1ms ce_threshold_selector 0x50/0xfc

Regardless of the selector chosen, the normal rules for ECN-marking of
packets still apply, i.e., the flow must still declare itself ECN-capable
by setting one of the bits in the ECN field to get marked at all.

v2:
- Add tc usage examples to patch description

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20211019174709.69081-1-toke@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Toke Høiland-Jørgensen 2021-10-19 19:47:09 +02:00 committed by Jakub Kicinski
parent 2641b62d2f
commit dfcb63ce1d
5 changed files with 25 additions and 15 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

7
include/net/codel.h
View file

@ -102,7 +102,9 @@ static inline u32 codel_time_to_us(codel_time_t val)
* @interval: width of moving time window
* @mtu: device mtu, or minimal queue backlog in bytes.
* @ecn: is Explicit Congestion Notification enabled
* @ce_threshold_ect1: if ce_threshold only marks ECT(1) packets
* @ce_threshold_selector: apply ce_threshold to packets matching this value
* in the diffserv/ECN byte of the IP header
* @ce_threshold_mask: mask to apply to ce_threshold_selector comparison
*/
struct codel_params {
codel_time_t target;
@ -110,7 +112,8 @@ struct codel_params {
codel_time_t interval;
u32 mtu;
bool ecn;
bool ce_threshold_ect1;
u8 ce_threshold_selector;
u8 ce_threshold_mask;
};
/**

14
include/net/codel_impl.h
View file

@ -54,7 +54,8 @@ static void codel_params_init(struct codel_params *params)
params->interval = MS2TIME(100);
params->target = MS2TIME(5);
params->ce_threshold = CODEL_DISABLED_THRESHOLD;
params->ce_threshold_ect1 = false;
params->ce_threshold_mask = 0;
params->ce_threshold_selector = 0;
params->ecn = false;
}
@ -250,13 +251,12 @@ static struct sk_buff *codel_dequeue(void *ctx,
if (skb && codel_time_after(vars->ldelay, params->ce_threshold)) {
bool set_ce = true;
if (params->ce_threshold_ect1) {
/* Note: if skb_get_dsfield() returns -1, following
* gives INET_ECN_MASK, which is != INET_ECN_ECT_1.
*/
u8 ecn = skb_get_dsfield(skb) & INET_ECN_MASK;
if (params->ce_threshold_mask) {
int dsfield = skb_get_dsfield(skb);
set_ce = (ecn == INET_ECN_ECT_1);
set_ce = (dsfield >= 0 &&
(((u8)dsfield & params->ce_threshold_mask) ==
params->ce_threshold_selector));
}
if (set_ce && INET_ECN_set_ce(skb))
stats->ce_mark++;

3
include/uapi/linux/pkt_sched.h
View file

@ -840,7 +840,8 @@ enum {
TCA_FQ_CODEL_CE_THRESHOLD,
TCA_FQ_CODEL_DROP_BATCH_SIZE,
TCA_FQ_CODEL_MEMORY_LIMIT,
TCA_FQ_CODEL_CE_THRESHOLD_ECT1,
TCA_FQ_CODEL_CE_THRESHOLD_SELECTOR,
TCA_FQ_CODEL_CE_THRESHOLD_MASK,
__TCA_FQ_CODEL_MAX
};

3
net/mac80211/sta_info.c
View file

@ -513,7 +513,8 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
sta->cparams.target = MS2TIME(20);
sta->cparams.interval = MS2TIME(100);
sta->cparams.ecn = true;
sta->cparams.ce_threshold_ect1 = false;
sta->cparams.ce_threshold_selector = 0;
sta->cparams.ce_threshold_mask = 0;
sta_dbg(sdata, "Allocated STA %pM\n", sta->sta.addr);

13
net/sched/sch_fq_codel.c
View file

@ -362,7 +362,8 @@ static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = {
[TCA_FQ_CODEL_CE_THRESHOLD] = { .type = NLA_U32 },
[TCA_FQ_CODEL_DROP_BATCH_SIZE] = { .type = NLA_U32 },
[TCA_FQ_CODEL_MEMORY_LIMIT] = { .type = NLA_U32 },
[TCA_FQ_CODEL_CE_THRESHOLD_ECT1] = { .type = NLA_U8 },
[TCA_FQ_CODEL_CE_THRESHOLD_SELECTOR] = { .type = NLA_U8 },
[TCA_FQ_CODEL_CE_THRESHOLD_MASK] = { .type = NLA_U8 },
};
static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt,
@ -409,8 +410,10 @@ static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt,
q->cparams.ce_threshold = (val * NSEC_PER_USEC) >> CODEL_SHIFT;
}
if (tb[TCA_FQ_CODEL_CE_THRESHOLD_ECT1])
q->cparams.ce_threshold_ect1 = !!nla_get_u8(tb[TCA_FQ_CODEL_CE_THRESHOLD_ECT1]);
if (tb[TCA_FQ_CODEL_CE_THRESHOLD_SELECTOR])
q->cparams.ce_threshold_selector = nla_get_u8(tb[TCA_FQ_CODEL_CE_THRESHOLD_SELECTOR]);
if (tb[TCA_FQ_CODEL_CE_THRESHOLD_MASK])
q->cparams.ce_threshold_mask = nla_get_u8(tb[TCA_FQ_CODEL_CE_THRESHOLD_MASK]);
if (tb[TCA_FQ_CODEL_INTERVAL]) {
u64 interval = nla_get_u32(tb[TCA_FQ_CODEL_INTERVAL]);
@ -552,7 +555,9 @@ static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb)
if (nla_put_u32(skb, TCA_FQ_CODEL_CE_THRESHOLD,
codel_time_to_us(q->cparams.ce_threshold)))
goto nla_put_failure;
if (nla_put_u8(skb, TCA_FQ_CODEL_CE_THRESHOLD_ECT1, q->cparams.ce_threshold_ect1))
if (nla_put_u8(skb, TCA_FQ_CODEL_CE_THRESHOLD_SELECTOR, q->cparams.ce_threshold_selector))
goto nla_put_failure;
if (nla_put_u8(skb, TCA_FQ_CODEL_CE_THRESHOLD_MASK, q->cparams.ce_threshold_mask))
goto nla_put_failure;
}