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authorNishanth Devarajan <ndev2021@gmail.com>2018-07-23 19:37:41 +0530
committerDavid S. Miller <davem@davemloft.net>2018-07-24 14:44:00 -0700
commitaea5f654e6b78a0c976f7a25950155932c77a53f (patch)
treed67053f9a2ec1a7a8a379e7480626be85a7e4cf2 /net/sched/sch_skbprio.c
parentnet: phy: add GBit master / slave error detection (diff)
downloadlinux-dev-aea5f654e6b78a0c976f7a25950155932c77a53f.tar.xz
linux-dev-aea5f654e6b78a0c976f7a25950155932c77a53f.zip
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>
Diffstat (limited to 'net/sched/sch_skbprio.c')
-rw-r--r--net/sched/sch_skbprio.c320
1 files changed, 320 insertions, 0 deletions
diff --git a/net/sched/sch_skbprio.c b/net/sched/sch_skbprio.c
new file mode 100644
index 000000000000..52c0b6d8f1d7
--- /dev/null
+++ b/net/sched/sch_skbprio.c
@@ -0,0 +1,320 @@
+/*
+ * net/sched/sch_skbprio.c SKB Priority Queue.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * Authors: Nishanth Devarajan, <ndev2021@gmail.com>
+ * Cody Doucette, <doucette@bu.edu>
+ * original idea by Michel Machado, Cody Doucette, and Qiaobin Fu
+ */
+
+#include <linux/string.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/skbuff.h>
+#include <net/pkt_sched.h>
+#include <net/sch_generic.h>
+#include <net/inet_ecn.h>
+
+/* SKB Priority Queue
+ * =================================
+ *
+ * Skbprio (SKB Priority Queue) is a queueing discipline that prioritizes
+ * packets according to their skb->priority field. Under congestion,
+ * Skbprio drops already-enqueued lower priority packets to make space
+ * available for higher priority packets; it was conceived as a solution
+ * for denial-of-service defenses that need to route packets with different
+ * priorities as a mean to overcome DoS attacks.
+ */
+
+struct skbprio_sched_data {
+ /* Queue state. */
+ struct sk_buff_head qdiscs[SKBPRIO_MAX_PRIORITY];
+ struct gnet_stats_queue qstats[SKBPRIO_MAX_PRIORITY];
+ u16 highest_prio;
+ u16 lowest_prio;
+};
+
+static u16 calc_new_high_prio(const struct skbprio_sched_data *q)
+{
+ int prio;
+
+ for (prio = q->highest_prio - 1; prio >= q->lowest_prio; prio--) {
+ if (!skb_queue_empty(&q->qdiscs[prio]))
+ return prio;
+ }
+
+ /* SKB queue is empty, return 0 (default highest priority setting). */
+ return 0;
+}
+
+static u16 calc_new_low_prio(const struct skbprio_sched_data *q)
+{
+ int prio;
+
+ for (prio = q->lowest_prio + 1; prio <= q->highest_prio; prio++) {
+ if (!skb_queue_empty(&q->qdiscs[prio]))
+ return prio;
+ }
+
+ /* SKB queue is empty, return SKBPRIO_MAX_PRIORITY - 1
+ * (default lowest priority setting).
+ */
+ return SKBPRIO_MAX_PRIORITY - 1;
+}
+
+static int skbprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+ struct sk_buff **to_free)
+{
+ const unsigned int max_priority = SKBPRIO_MAX_PRIORITY - 1;
+ struct skbprio_sched_data *q = qdisc_priv(sch);
+ struct sk_buff_head *qdisc;
+ struct sk_buff_head *lp_qdisc;
+ struct sk_buff *to_drop;
+ u16 prio, lp;
+
+ /* Obtain the priority of @skb. */
+ prio = min(skb->priority, max_priority);
+
+ qdisc = &q->qdiscs[prio];
+ if (sch->q.qlen < sch->limit) {
+ __skb_queue_tail(qdisc, skb);
+ qdisc_qstats_backlog_inc(sch, skb);
+ q->qstats[prio].backlog += qdisc_pkt_len(skb);
+
+ /* Check to update highest and lowest priorities. */
+ if (prio > q->highest_prio)
+ q->highest_prio = prio;
+
+ if (prio < q->lowest_prio)
+ q->lowest_prio = prio;
+
+ sch->q.qlen++;
+ return NET_XMIT_SUCCESS;
+ }
+
+ /* If this packet has the lowest priority, drop it. */
+ lp = q->lowest_prio;
+ if (prio <= lp) {
+ q->qstats[prio].drops++;
+ q->qstats[prio].overlimits++;
+ return qdisc_drop(skb, sch, to_free);
+ }
+
+ __skb_queue_tail(qdisc, skb);
+ qdisc_qstats_backlog_inc(sch, skb);
+ q->qstats[prio].backlog += qdisc_pkt_len(skb);
+
+ /* Drop the packet at the tail of the lowest priority qdisc. */
+ lp_qdisc = &q->qdiscs[lp];
+ to_drop = __skb_dequeue_tail(lp_qdisc);
+ BUG_ON(!to_drop);
+ qdisc_qstats_backlog_dec(sch, to_drop);
+ qdisc_drop(to_drop, sch, to_free);
+
+ q->qstats[lp].backlog -= qdisc_pkt_len(to_drop);
+ q->qstats[lp].drops++;
+ q->qstats[lp].overlimits++;
+
+ /* Check to update highest and lowest priorities. */
+ if (skb_queue_empty(lp_qdisc)) {
+ if (q->lowest_prio == q->highest_prio) {
+ /* The incoming packet is the only packet in queue. */
+ BUG_ON(sch->q.qlen != 1);
+ q->lowest_prio = prio;
+ q->highest_prio = prio;
+ } else {
+ q->lowest_prio = calc_new_low_prio(q);
+ }
+ }
+
+ if (prio > q->highest_prio)
+ q->highest_prio = prio;
+
+ return NET_XMIT_CN;
+}
+
+static struct sk_buff *skbprio_dequeue(struct Qdisc *sch)
+{
+ struct skbprio_sched_data *q = qdisc_priv(sch);
+ struct sk_buff_head *hpq = &q->qdiscs[q->highest_prio];
+ struct sk_buff *skb = __skb_dequeue(hpq);
+
+ if (unlikely(!skb))
+ return NULL;
+
+ sch->q.qlen--;
+ qdisc_qstats_backlog_dec(sch, skb);
+ qdisc_bstats_update(sch, skb);
+
+ q->qstats[q->highest_prio].backlog -= qdisc_pkt_len(skb);
+
+ /* Update highest priority field. */
+ if (skb_queue_empty(hpq)) {
+ if (q->lowest_prio == q->highest_prio) {
+ BUG_ON(sch->q.qlen);
+ q->highest_prio = 0;
+ q->lowest_prio = SKBPRIO_MAX_PRIORITY - 1;
+ } else {
+ q->highest_prio = calc_new_high_prio(q);
+ }
+ }
+ return skb;
+}
+
+static int skbprio_change(struct Qdisc *sch, struct nlattr *opt,
+ struct netlink_ext_ack *extack)
+{
+ struct tc_skbprio_qopt *ctl = nla_data(opt);
+
+ sch->limit = ctl->limit;
+ return 0;
+}
+
+static int skbprio_init(struct Qdisc *sch, struct nlattr *opt,
+ struct netlink_ext_ack *extack)
+{
+ struct skbprio_sched_data *q = qdisc_priv(sch);
+ int prio;
+
+ /* Initialise all queues, one for each possible priority. */
+ for (prio = 0; prio < SKBPRIO_MAX_PRIORITY; prio++)
+ __skb_queue_head_init(&q->qdiscs[prio]);
+
+ memset(&q->qstats, 0, sizeof(q->qstats));
+ q->highest_prio = 0;
+ q->lowest_prio = SKBPRIO_MAX_PRIORITY - 1;
+ sch->limit = 64;
+ if (!opt)
+ return 0;
+
+ return skbprio_change(sch, opt, extack);
+}
+
+static int skbprio_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+ struct tc_skbprio_qopt opt;
+
+ opt.limit = sch->limit;
+
+ if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
+ return -1;
+
+ return skb->len;
+}
+
+static void skbprio_reset(struct Qdisc *sch)
+{
+ struct skbprio_sched_data *q = qdisc_priv(sch);
+ int prio;
+
+ sch->qstats.backlog = 0;
+ sch->q.qlen = 0;
+
+ for (prio = 0; prio < SKBPRIO_MAX_PRIORITY; prio++)
+ __skb_queue_purge(&q->qdiscs[prio]);
+
+ memset(&q->qstats, 0, sizeof(q->qstats));
+ q->highest_prio = 0;
+ q->lowest_prio = SKBPRIO_MAX_PRIORITY - 1;
+}
+
+static void skbprio_destroy(struct Qdisc *sch)
+{
+ struct skbprio_sched_data *q = qdisc_priv(sch);
+ int prio;
+
+ for (prio = 0; prio < SKBPRIO_MAX_PRIORITY; prio++)
+ __skb_queue_purge(&q->qdiscs[prio]);
+}
+
+static struct Qdisc *skbprio_leaf(struct Qdisc *sch, unsigned long arg)
+{
+ return NULL;
+}
+
+static unsigned long skbprio_find(struct Qdisc *sch, u32 classid)
+{
+ return 0;
+}
+
+static int skbprio_dump_class(struct Qdisc *sch, unsigned long cl,
+ struct sk_buff *skb, struct tcmsg *tcm)
+{
+ tcm->tcm_handle |= TC_H_MIN(cl);
+ return 0;
+}
+
+static int skbprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
+ struct gnet_dump *d)
+{
+ struct skbprio_sched_data *q = qdisc_priv(sch);
+ if (gnet_stats_copy_queue(d, NULL, &q->qstats[cl - 1],
+ q->qstats[cl - 1].qlen) < 0)
+ return -1;
+ return 0;
+}
+
+static void skbprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
+{
+ unsigned int i;
+
+ if (arg->stop)
+ return;
+
+ for (i = 0; i < SKBPRIO_MAX_PRIORITY; i++) {
+ if (arg->count < arg->skip) {
+ arg->count++;
+ continue;
+ }
+ if (arg->fn(sch, i + 1, arg) < 0) {
+ arg->stop = 1;
+ break;
+ }
+ arg->count++;
+ }
+}
+
+static const struct Qdisc_class_ops skbprio_class_ops = {
+ .leaf = skbprio_leaf,
+ .find = skbprio_find,
+ .dump = skbprio_dump_class,
+ .dump_stats = skbprio_dump_class_stats,
+ .walk = skbprio_walk,
+};
+
+static struct Qdisc_ops skbprio_qdisc_ops __read_mostly = {
+ .cl_ops = &skbprio_class_ops,
+ .id = "skbprio",
+ .priv_size = sizeof(struct skbprio_sched_data),
+ .enqueue = skbprio_enqueue,
+ .dequeue = skbprio_dequeue,
+ .peek = qdisc_peek_dequeued,
+ .init = skbprio_init,
+ .reset = skbprio_reset,
+ .change = skbprio_change,
+ .dump = skbprio_dump,
+ .destroy = skbprio_destroy,
+ .owner = THIS_MODULE,
+};
+
+static int __init skbprio_module_init(void)
+{
+ return register_qdisc(&skbprio_qdisc_ops);
+}
+
+static void __exit skbprio_module_exit(void)
+{
+ unregister_qdisc(&skbprio_qdisc_ops);
+}
+
+module_init(skbprio_module_init)
+module_exit(skbprio_module_exit)
+
+MODULE_LICENSE("GPL");