net/sched: add skbprio scheduler
Skbprio (SKB Priority Queue) is a queueing discipline that prioritizes packets according to their skb->priority field. Under congestion, already-enqueued lower priority packets will be dropped to make space available for higher priority packets. Skbprio was conceived as a solution for denial-of-service defenses that need to route packets with different priorities as a means to overcome DoS attacks. v5 *Do not reference qdisc_dev(sch)->tx_queue_len for setting limit. Instead set default sch->limit to 64. v4 *Drop Documentation/networking/sch_skbprio.txt doc file to move it to tc man page for Skbprio, in iproute2. v3 *Drop max_limit parameter in struct skbprio_sched_data and instead use sch->limit. *Reference qdisc_dev(sch)->tx_queue_len only once, during initialisation for qdisc (previously being referenced every time qdisc changes). *Move qdisc's detailed description from in-code to Documentation/networking. *When qdisc is saturated, enqueue incoming packet first before dequeueing lowest priority packet in queue - improves usage of call stack registers. *Introduce and use overlimit stat to keep track of number of dropped packets. v2 *Use skb->priority field rather than DS field. Rename queueing discipline as SKB Priority Queue (previously Gatekeeper Priority Queue). *Queueing discipline is made classful to expose Skbprio's internal priority queues. Signed-off-by: Nishanth Devarajan <ndev2021@gmail.com> Reviewed-by: Sachin Paryani <sachin.paryani@gmail.com> Reviewed-by: Cody Doucette <doucette@bu.edu> Reviewed-by: Michel Machado <michel@digirati.com.br> Acked-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nishanth Devarajan
David S. Miller
parent
b8f8c8eb40
commit
aea5f654e6
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@ -124,6 +124,21 @@ struct tc_fifo_qopt {
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__u32 limit; /* Queue length: bytes for bfifo, packets for pfifo */
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};
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/* SKBPRIO section */
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/*
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* Priorities go from zero to (SKBPRIO_MAX_PRIORITY - 1).
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* SKBPRIO_MAX_PRIORITY should be at least 64 in order for skbprio to be able
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* to map one to one the DS field of IPV4 and IPV6 headers.
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* Memory allocation grows linearly with SKBPRIO_MAX_PRIORITY.
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*/
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#define SKBPRIO_MAX_PRIORITY 64
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struct tc_skbprio_qopt {
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__u32 limit; /* Queue length in packets. */
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};
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/* PRIO section */
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#define TCQ_PRIO_BANDS 16
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@ -251,6 +251,19 @@ config NET_SCH_MQPRIO
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If unsure, say N.
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config NET_SCH_SKBPRIO
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tristate "SKB priority queue scheduler (SKBPRIO)"
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help
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Say Y here if you want to use the SKB priority queue
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scheduler. This schedules packets according to skb->priority,
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which is useful for request packets in DoS mitigation systems such
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as Gatekeeper.
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To compile this driver as a module, choose M here: the module will
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be called sch_skbprio.
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If unsure, say N.
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config NET_SCH_CHOKE
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tristate "CHOose and Keep responsive flow scheduler (CHOKE)"
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help
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@ -46,6 +46,7 @@ obj-$(CONFIG_NET_SCH_NETEM) += sch_netem.o
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obj-$(CONFIG_NET_SCH_DRR) += sch_drr.o
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obj-$(CONFIG_NET_SCH_PLUG) += sch_plug.o
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obj-$(CONFIG_NET_SCH_MQPRIO) += sch_mqprio.o
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obj-$(CONFIG_NET_SCH_SKBPRIO) += sch_skbprio.o
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obj-$(CONFIG_NET_SCH_CHOKE) += sch_choke.o
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obj-$(CONFIG_NET_SCH_QFQ) += sch_qfq.o
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obj-$(CONFIG_NET_SCH_CODEL) += sch_codel.o
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@ -0,0 +1,320 @@
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/*
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* net/sched/sch_skbprio.c SKB Priority Queue.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Authors: Nishanth Devarajan, <ndev2021@gmail.com>
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* Cody Doucette, <doucette@bu.edu>
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* original idea by Michel Machado, Cody Doucette, and Qiaobin Fu
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*/
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#include <linux/string.h>
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#include <linux/module.h>
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#include <linux/slab.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/skbuff.h>
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#include <net/pkt_sched.h>
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#include <net/sch_generic.h>
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#include <net/inet_ecn.h>
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/* SKB Priority Queue
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* =================================
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*
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* Skbprio (SKB Priority Queue) is a queueing discipline that prioritizes
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* packets according to their skb->priority field. Under congestion,
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* Skbprio drops already-enqueued lower priority packets to make space
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* available for higher priority packets; it was conceived as a solution
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* for denial-of-service defenses that need to route packets with different
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* priorities as a mean to overcome DoS attacks.
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*/
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struct skbprio_sched_data {
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/* Queue state. */
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struct sk_buff_head qdiscs[SKBPRIO_MAX_PRIORITY];
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struct gnet_stats_queue qstats[SKBPRIO_MAX_PRIORITY];
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u16 highest_prio;
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u16 lowest_prio;
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};
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static u16 calc_new_high_prio(const struct skbprio_sched_data *q)
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{
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int prio;
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for (prio = q->highest_prio - 1; prio >= q->lowest_prio; prio--) {
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if (!skb_queue_empty(&q->qdiscs[prio]))
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return prio;
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}
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/* SKB queue is empty, return 0 (default highest priority setting). */
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return 0;
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}
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static u16 calc_new_low_prio(const struct skbprio_sched_data *q)
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{
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int prio;
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for (prio = q->lowest_prio + 1; prio <= q->highest_prio; prio++) {
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if (!skb_queue_empty(&q->qdiscs[prio]))
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return prio;
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}
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/* SKB queue is empty, return SKBPRIO_MAX_PRIORITY - 1
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* (default lowest priority setting).
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*/
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return SKBPRIO_MAX_PRIORITY - 1;
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}
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static int skbprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
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struct sk_buff **to_free)
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{
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const unsigned int max_priority = SKBPRIO_MAX_PRIORITY - 1;
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struct skbprio_sched_data *q = qdisc_priv(sch);
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struct sk_buff_head *qdisc;
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struct sk_buff_head *lp_qdisc;
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struct sk_buff *to_drop;
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u16 prio, lp;
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/* Obtain the priority of @skb. */
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prio = min(skb->priority, max_priority);
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qdisc = &q->qdiscs[prio];
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if (sch->q.qlen < sch->limit) {
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__skb_queue_tail(qdisc, skb);
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qdisc_qstats_backlog_inc(sch, skb);
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q->qstats[prio].backlog += qdisc_pkt_len(skb);
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/* Check to update highest and lowest priorities. */
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if (prio > q->highest_prio)
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q->highest_prio = prio;
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if (prio < q->lowest_prio)
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q->lowest_prio = prio;
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sch->q.qlen++;
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return NET_XMIT_SUCCESS;
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}
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/* If this packet has the lowest priority, drop it. */
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lp = q->lowest_prio;
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if (prio <= lp) {
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q->qstats[prio].drops++;
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q->qstats[prio].overlimits++;
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return qdisc_drop(skb, sch, to_free);
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}
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__skb_queue_tail(qdisc, skb);
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qdisc_qstats_backlog_inc(sch, skb);
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q->qstats[prio].backlog += qdisc_pkt_len(skb);
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/* Drop the packet at the tail of the lowest priority qdisc. */
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lp_qdisc = &q->qdiscs[lp];
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to_drop = __skb_dequeue_tail(lp_qdisc);
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BUG_ON(!to_drop);
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qdisc_qstats_backlog_dec(sch, to_drop);
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qdisc_drop(to_drop, sch, to_free);
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q->qstats[lp].backlog -= qdisc_pkt_len(to_drop);
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q->qstats[lp].drops++;
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q->qstats[lp].overlimits++;
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/* Check to update highest and lowest priorities. */
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if (skb_queue_empty(lp_qdisc)) {
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if (q->lowest_prio == q->highest_prio) {
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/* The incoming packet is the only packet in queue. */
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BUG_ON(sch->q.qlen != 1);
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q->lowest_prio = prio;
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q->highest_prio = prio;
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} else {
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q->lowest_prio = calc_new_low_prio(q);
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}
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}
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if (prio > q->highest_prio)
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q->highest_prio = prio;
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return NET_XMIT_CN;
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}
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static struct sk_buff *skbprio_dequeue(struct Qdisc *sch)
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{
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struct skbprio_sched_data *q = qdisc_priv(sch);
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struct sk_buff_head *hpq = &q->qdiscs[q->highest_prio];
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struct sk_buff *skb = __skb_dequeue(hpq);
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if (unlikely(!skb))
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return NULL;
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sch->q.qlen--;
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qdisc_qstats_backlog_dec(sch, skb);
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qdisc_bstats_update(sch, skb);
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q->qstats[q->highest_prio].backlog -= qdisc_pkt_len(skb);
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/* Update highest priority field. */
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if (skb_queue_empty(hpq)) {
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if (q->lowest_prio == q->highest_prio) {
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BUG_ON(sch->q.qlen);
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q->highest_prio = 0;
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q->lowest_prio = SKBPRIO_MAX_PRIORITY - 1;
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} else {
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q->highest_prio = calc_new_high_prio(q);
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}
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}
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return skb;
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}
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static int skbprio_change(struct Qdisc *sch, struct nlattr *opt,
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struct netlink_ext_ack *extack)
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{
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struct tc_skbprio_qopt *ctl = nla_data(opt);
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sch->limit = ctl->limit;
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return 0;
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}
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static int skbprio_init(struct Qdisc *sch, struct nlattr *opt,
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struct netlink_ext_ack *extack)
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{
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struct skbprio_sched_data *q = qdisc_priv(sch);
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int prio;
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/* Initialise all queues, one for each possible priority. */
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for (prio = 0; prio < SKBPRIO_MAX_PRIORITY; prio++)
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__skb_queue_head_init(&q->qdiscs[prio]);
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memset(&q->qstats, 0, sizeof(q->qstats));
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q->highest_prio = 0;
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q->lowest_prio = SKBPRIO_MAX_PRIORITY - 1;
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sch->limit = 64;
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if (!opt)
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return 0;
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return skbprio_change(sch, opt, extack);
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}
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static int skbprio_dump(struct Qdisc *sch, struct sk_buff *skb)
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{
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struct tc_skbprio_qopt opt;
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opt.limit = sch->limit;
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if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
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return -1;
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return skb->len;
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}
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static void skbprio_reset(struct Qdisc *sch)
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{
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struct skbprio_sched_data *q = qdisc_priv(sch);
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int prio;
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sch->qstats.backlog = 0;
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sch->q.qlen = 0;
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for (prio = 0; prio < SKBPRIO_MAX_PRIORITY; prio++)
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__skb_queue_purge(&q->qdiscs[prio]);
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memset(&q->qstats, 0, sizeof(q->qstats));
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q->highest_prio = 0;
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q->lowest_prio = SKBPRIO_MAX_PRIORITY - 1;
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}
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static void skbprio_destroy(struct Qdisc *sch)
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{
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struct skbprio_sched_data *q = qdisc_priv(sch);
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int prio;
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for (prio = 0; prio < SKBPRIO_MAX_PRIORITY; prio++)
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__skb_queue_purge(&q->qdiscs[prio]);
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}
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static struct Qdisc *skbprio_leaf(struct Qdisc *sch, unsigned long arg)
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{
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return NULL;
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}
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static unsigned long skbprio_find(struct Qdisc *sch, u32 classid)
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{
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return 0;
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}
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static int skbprio_dump_class(struct Qdisc *sch, unsigned long cl,
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struct sk_buff *skb, struct tcmsg *tcm)
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{
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tcm->tcm_handle |= TC_H_MIN(cl);
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return 0;
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}
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static int skbprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
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struct gnet_dump *d)
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{
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struct skbprio_sched_data *q = qdisc_priv(sch);
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if (gnet_stats_copy_queue(d, NULL, &q->qstats[cl - 1],
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q->qstats[cl - 1].qlen) < 0)
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return -1;
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return 0;
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}
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static void skbprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
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{
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unsigned int i;
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if (arg->stop)
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return;
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for (i = 0; i < SKBPRIO_MAX_PRIORITY; i++) {
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if (arg->count < arg->skip) {
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arg->count++;
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continue;
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}
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if (arg->fn(sch, i + 1, arg) < 0) {
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arg->stop = 1;
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break;
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}
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arg->count++;
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}
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}
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static const struct Qdisc_class_ops skbprio_class_ops = {
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.leaf = skbprio_leaf,
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.find = skbprio_find,
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.dump = skbprio_dump_class,
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.dump_stats = skbprio_dump_class_stats,
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.walk = skbprio_walk,
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};
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static struct Qdisc_ops skbprio_qdisc_ops __read_mostly = {
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.cl_ops = &skbprio_class_ops,
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.id = "skbprio",
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.priv_size = sizeof(struct skbprio_sched_data),
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.enqueue = skbprio_enqueue,
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.dequeue = skbprio_dequeue,
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.peek = qdisc_peek_dequeued,
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.init = skbprio_init,
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.reset = skbprio_reset,
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.change = skbprio_change,
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.dump = skbprio_dump,
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.destroy = skbprio_destroy,
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.owner = THIS_MODULE,
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};
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static int __init skbprio_module_init(void)
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{
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return register_qdisc(&skbprio_qdisc_ops);
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}
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static void __exit skbprio_module_exit(void)
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{
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unregister_qdisc(&skbprio_qdisc_ops);
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}
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module_init(skbprio_module_init)
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module_exit(skbprio_module_exit)
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MODULE_LICENSE("GPL");
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