text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * Copyright (c) 2008, Intel Corporation.
   *
   * Author: Alexander Duyck <alexander.h.duyck@intel.com>
   */
  
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/string.h>
  #include <linux/errno.h>
  #include <linux/skbuff.h>
  #include <net/netlink.h>
  #include <net/pkt_sched.h>
  #include <net/pkt_cls.h>
  
  struct multiq_sched_data {
  	u16 bands;
  	u16 max_bands;
  	u16 curband;
  	struct tcf_proto __rcu *filter_list;
  	struct tcf_block *block;
  	struct Qdisc **queues;
  };
  
  
  static struct Qdisc *
  multiq_classify(struct sk_buff *skb, struct Qdisc *sch, int *qerr)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	u32 band;
  	struct tcf_result res;
  	struct tcf_proto *fl = rcu_dereference_bh(q->filter_list);
  	int err;
  
  	*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
  	err = tcf_classify(skb, NULL, fl, &res, false);
  #ifdef CONFIG_NET_CLS_ACT
  	switch (err) {
  	case TC_ACT_STOLEN:
  	case TC_ACT_QUEUED:
  	case TC_ACT_TRAP:
  		*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
  		fallthrough;
  	case TC_ACT_SHOT:
  		return NULL;
  	}
  #endif
  	band = skb_get_queue_mapping(skb);
  
  	if (band >= q->bands)
  		return q->queues[0];
  
  	return q->queues[band];
  }
  
  static int
  multiq_enqueue(struct sk_buff *skb, struct Qdisc *sch,
  	       struct sk_buff **to_free)
  {
  	struct Qdisc *qdisc;
  	int ret;
  
  	qdisc = multiq_classify(skb, sch, &ret);
  #ifdef CONFIG_NET_CLS_ACT
  	if (qdisc == NULL) {
  
  		if (ret & __NET_XMIT_BYPASS)
  			qdisc_qstats_drop(sch);
  		__qdisc_drop(skb, to_free);
  		return ret;
  	}
  #endif
  
  	ret = qdisc_enqueue(skb, qdisc, to_free);
  	if (ret == NET_XMIT_SUCCESS) {
  		sch->q.qlen++;
  		return NET_XMIT_SUCCESS;
  	}
  	if (net_xmit_drop_count(ret))
  		qdisc_qstats_drop(sch);
  	return ret;
  }
  
  static struct sk_buff *multiq_dequeue(struct Qdisc *sch)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	struct Qdisc *qdisc;
  	struct sk_buff *skb;
  	int band;
  
  	for (band = 0; band < q->bands; band++) {
  		/* cycle through bands to ensure fairness */
  		q->curband++;
  		if (q->curband >= q->bands)
  			q->curband = 0;
  
  		/* Check that target subqueue is available before
  		 * pulling an skb to avoid head-of-line blocking.
  		 */
  		if (!netif_xmit_stopped(
  		    netdev_get_tx_queue(qdisc_dev(sch), q->curband))) {
  			qdisc = q->queues[q->curband];
  			skb = qdisc->dequeue(qdisc);
  			if (skb) {
  				qdisc_bstats_update(sch, skb);
  				sch->q.qlen--;
  				return skb;
  			}
  		}
  	}
  	return NULL;
  
  }
  
  static struct sk_buff *multiq_peek(struct Qdisc *sch)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	unsigned int curband = q->curband;
  	struct Qdisc *qdisc;
  	struct sk_buff *skb;
  	int band;
  
  	for (band = 0; band < q->bands; band++) {
  		/* cycle through bands to ensure fairness */
  		curband++;
  		if (curband >= q->bands)
  			curband = 0;
  
  		/* Check that target subqueue is available before
  		 * pulling an skb to avoid head-of-line blocking.
  		 */
  		if (!netif_xmit_stopped(
  		    netdev_get_tx_queue(qdisc_dev(sch), curband))) {
  			qdisc = q->queues[curband];
  			skb = qdisc->ops->peek(qdisc);
  			if (skb)
  				return skb;
  		}
  	}
  	return NULL;
  
  }
  
  static void
  multiq_reset(struct Qdisc *sch)
  {
  	u16 band;
  	struct multiq_sched_data *q = qdisc_priv(sch);
  
  	for (band = 0; band < q->bands; band++)
  		qdisc_reset(q->queues[band]);
  	sch->q.qlen = 0;
  	q->curband = 0;
  }
  
  static void
  multiq_destroy(struct Qdisc *sch)
  {
  	int band;
  	struct multiq_sched_data *q = qdisc_priv(sch);
  
  	tcf_block_put(q->block);
  	for (band = 0; band < q->bands; band++)
  		qdisc_put(q->queues[band]);
  
  	kfree(q->queues);
  }
  
  static int multiq_tune(struct Qdisc *sch, struct nlattr *opt,
  		       struct netlink_ext_ack *extack)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	struct tc_multiq_qopt *qopt;
  	struct Qdisc **removed;
  	int i, n_removed = 0;
  
  	if (!netif_is_multiqueue(qdisc_dev(sch)))
  		return -EOPNOTSUPP;
  	if (nla_len(opt) < sizeof(*qopt))
  		return -EINVAL;
  
  	qopt = nla_data(opt);
  
  	qopt->bands = qdisc_dev(sch)->real_num_tx_queues;
  
  	removed = kmalloc(sizeof(*removed) * (q->max_bands - q->bands),
  			  GFP_KERNEL);
  	if (!removed)
  		return -ENOMEM;
  
  	sch_tree_lock(sch);
  	q->bands = qopt->bands;
  	for (i = q->bands; i < q->max_bands; i++) {
  		if (q->queues[i] != &noop_qdisc) {
  			struct Qdisc *child = q->queues[i];
  
  			q->queues[i] = &noop_qdisc;
  			qdisc_purge_queue(child);
  			removed[n_removed++] = child;
  		}
  	}
  
  	sch_tree_unlock(sch);
  
  	for (i = 0; i < n_removed; i++)
  		qdisc_put(removed[i]);
  	kfree(removed);
  
  	for (i = 0; i < q->bands; i++) {
  		if (q->queues[i] == &noop_qdisc) {
  			struct Qdisc *child, *old;
  			child = qdisc_create_dflt(sch->dev_queue,
  						  &pfifo_qdisc_ops,
  						  TC_H_MAKE(sch->handle,
  							    i + 1), extack);
  			if (child) {
  				sch_tree_lock(sch);
  				old = q->queues[i];
  				q->queues[i] = child;
  				if (child != &noop_qdisc)
  					qdisc_hash_add(child, true);
  
  				if (old != &noop_qdisc)
  					qdisc_purge_queue(old);
  				sch_tree_unlock(sch);
  				qdisc_put(old);
  			}
  		}
  	}
  	return 0;
  }
  
  static int multiq_init(struct Qdisc *sch, struct nlattr *opt,
  		       struct netlink_ext_ack *extack)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	int i, err;
  
  	q->queues = NULL;
  
  	if (!opt)
  		return -EINVAL;
  
  	err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
  	if (err)
  		return err;
  
  	q->max_bands = qdisc_dev(sch)->num_tx_queues;
  
  	q->queues = kcalloc(q->max_bands, sizeof(struct Qdisc *), GFP_KERNEL);
  	if (!q->queues)
  		return -ENOBUFS;
  	for (i = 0; i < q->max_bands; i++)
  		q->queues[i] = &noop_qdisc;
  
  	return multiq_tune(sch, opt, extack);
  }
  
  static int multiq_dump(struct Qdisc *sch, struct sk_buff *skb)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	unsigned char *b = skb_tail_pointer(skb);
  	struct tc_multiq_qopt opt;
  
  	opt.bands = q->bands;
  	opt.max_bands = q->max_bands;
  
  	if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
  		goto nla_put_failure;
  
  	return skb->len;
  
  nla_put_failure:
  	nlmsg_trim(skb, b);
  	return -1;
  }
  
  static int multiq_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
  			struct Qdisc **old, struct netlink_ext_ack *extack)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	unsigned long band = arg - 1;
  
  	if (new == NULL)
  		new = &noop_qdisc;
  
  	*old = qdisc_replace(sch, new, &q->queues[band]);
  	return 0;
  }
  
  static struct Qdisc *
  multiq_leaf(struct Qdisc *sch, unsigned long arg)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	unsigned long band = arg - 1;
  
  	return q->queues[band];
  }
  
  static unsigned long multiq_find(struct Qdisc *sch, u32 classid)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	unsigned long band = TC_H_MIN(classid);
  
  	if (band - 1 >= q->bands)
  		return 0;
  	return band;
  }
  
  static unsigned long multiq_bind(struct Qdisc *sch, unsigned long parent,
  				 u32 classid)
  {
  	return multiq_find(sch, classid);
  }
  
  
  static void multiq_unbind(struct Qdisc *q, unsigned long cl)
  {
  }
  
  static int multiq_dump_class(struct Qdisc *sch, unsigned long cl,
  			     struct sk_buff *skb, struct tcmsg *tcm)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  
  	tcm->tcm_handle |= TC_H_MIN(cl);
  	tcm->tcm_info = q->queues[cl - 1]->handle;
  	return 0;
  }
  
  static int multiq_dump_class_stats(struct Qdisc *sch, unsigned long cl,
  				 struct gnet_dump *d)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	struct Qdisc *cl_q;
  
  	cl_q = q->queues[cl - 1];
  	if (gnet_stats_copy_basic(d, cl_q->cpu_bstats, &cl_q->bstats, true) < 0 ||
  	    qdisc_qstats_copy(d, cl_q) < 0)
  		return -1;
  
  	return 0;
  }
  
  static void multiq_walk(struct Qdisc *sch, struct qdisc_walker *arg)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  	int band;
  
  	if (arg->stop)
  		return;
  
  	for (band = 0; band < q->bands; band++) {
  		if (arg->count < arg->skip) {
  			arg->count++;
  			continue;
  		}
  		if (arg->fn(sch, band + 1, arg) < 0) {
  			arg->stop = 1;
  			break;
  		}
  		arg->count++;
  	}
  }
  
  static struct tcf_block *multiq_tcf_block(struct Qdisc *sch, unsigned long cl,
  					  struct netlink_ext_ack *extack)
  {
  	struct multiq_sched_data *q = qdisc_priv(sch);
  
  	if (cl)
  		return NULL;
  	return q->block;
  }
  
  static const struct Qdisc_class_ops multiq_class_ops = {
  	.graft		=	multiq_graft,
  	.leaf		=	multiq_leaf,
  	.find		=	multiq_find,
  	.walk		=	multiq_walk,
  	.tcf_block	=	multiq_tcf_block,
  	.bind_tcf	=	multiq_bind,
  	.unbind_tcf	=	multiq_unbind,
  	.dump		=	multiq_dump_class,
  	.dump_stats	=	multiq_dump_class_stats,
  };
  
  static struct Qdisc_ops multiq_qdisc_ops __read_mostly = {
  	.next		=	NULL,
  	.cl_ops		=	&multiq_class_ops,
  	.id		=	"multiq",
  	.priv_size	=	sizeof(struct multiq_sched_data),
  	.enqueue	=	multiq_enqueue,
  	.dequeue	=	multiq_dequeue,
  	.peek		=	multiq_peek,
  	.init		=	multiq_init,
  	.reset		=	multiq_reset,
  	.destroy	=	multiq_destroy,
  	.change		=	multiq_tune,
  	.dump		=	multiq_dump,
  	.owner		=	THIS_MODULE,
  };
  
  static int __init multiq_module_init(void)
  {
  	return register_qdisc(&multiq_qdisc_ops);
  }
  
  static void __exit multiq_module_exit(void)
  {
  	unregister_qdisc(&multiq_qdisc_ops);
  }
  
  module_init(multiq_module_init)
  module_exit(multiq_module_exit)
  
  MODULE_LICENSE("GPL");
  