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linux/net/sched/sch_teql.c
Herbert Xu 932ff279a4 [NET]: Add netif_tx_lock 
Various drivers use xmit_lock internally to synchronise with their
transmission routines.  They do so without setting xmit_lock_owner.
This is fine as long as netpoll is not in use.

With netpoll it is possible for deadlocks to occur if xmit_lock_owner
isn't set.  This is because if a printk occurs while xmit_lock is held
and xmit_lock_owner is not set can cause netpoll to attempt to take
xmit_lock recursively.

While it is possible to resolve this by getting netpoll to use
trylock, it is suboptimal because netpoll's sole objective is to
maximise the chance of getting the printk out on the wire.  So
delaying or dropping the message is to be avoided as much as possible.

So the only alternative is to always set xmit_lock_owner.  The
following patch does this by introducing the netif_tx_lock family of
functions that take care of setting/unsetting xmit_lock_owner.

I renamed xmit_lock to _xmit_lock to indicate that it should not be
used directly.  I didn't provide irq versions of the netif_tx_lock
functions since xmit_lock is meant to be a BH-disabling lock.

This is pretty much a straight text substitution except for a small
bug fix in winbond.  It currently uses
netif_stop_queue/spin_unlock_wait to stop transmission.  This is
unsafe as an IRQ can potentially wake up the queue.  So it is safer to
use netif_tx_disable.

The hamradio bits used spin_lock_irq but it is unnecessary as
xmit_lock must never be taken in an IRQ handler.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-06-17 21:30:14 -07:00

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/* net/sched/sch_teql.c "True" (or "trivial") link equalizer.
*
* 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: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
*/
#include <linux/module.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/bitops.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/errno.h>
#include <linux/interrupt.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/notifier.h>
#include <linux/init.h>
#include <net/ip.h>
#include <net/route.h>
#include <linux/skbuff.h>
#include <linux/moduleparam.h>
#include <net/sock.h>
#include <net/pkt_sched.h>
/*
How to setup it.
----------------
After loading this module you will find a new device teqlN
and new qdisc with the same name. To join a slave to the equalizer
you should just set this qdisc on a device f.e.
# tc qdisc add dev eth0 root teql0
# tc qdisc add dev eth1 root teql0
That's all. Full PnP 8)
Applicability.
--------------
1. Slave devices MUST be active devices, i.e., they must raise the tbusy
signal and generate EOI events. If you want to equalize virtual devices
like tunnels, use a normal eql device.
2. This device puts no limitations on physical slave characteristics
f.e. it will equalize 9600baud line and 100Mb ethernet perfectly :-)
Certainly, large difference in link speeds will make the resulting
eqalized link unusable, because of huge packet reordering.
I estimate an upper useful difference as ~10 times.
3. If the slave requires address resolution, only protocols using
neighbour cache (IPv4/IPv6) will work over the equalized link.
Other protocols are still allowed to use the slave device directly,
which will not break load balancing, though native slave
traffic will have the highest priority. */
struct teql_master
{
struct Qdisc_ops qops;
struct net_device *dev;
struct Qdisc *slaves;
struct list_head master_list;
struct net_device_stats stats;
};
struct teql_sched_data
{
struct Qdisc *next;
struct teql_master *m;
struct neighbour *ncache;
struct sk_buff_head q;
};
#define NEXT_SLAVE(q) (((struct teql_sched_data*)qdisc_priv(q))->next)
#define FMASK (IFF_BROADCAST|IFF_POINTOPOINT|IFF_BROADCAST)
/* "teql*" qdisc routines */
static int
teql_enqueue(struct sk_buff *skb, struct Qdisc* sch)
{
struct net_device *dev = sch->dev;
struct teql_sched_data *q = qdisc_priv(sch);
__skb_queue_tail(&q->q, skb);
if (q->q.qlen <= dev->tx_queue_len) {
sch->bstats.bytes += skb->len;
sch->bstats.packets++;
return 0;
}
__skb_unlink(skb, &q->q);
kfree_skb(skb);
sch->qstats.drops++;
return NET_XMIT_DROP;
}
static int
teql_requeue(struct sk_buff *skb, struct Qdisc* sch)
{
struct teql_sched_data *q = qdisc_priv(sch);
__skb_queue_head(&q->q, skb);
sch->qstats.requeues++;
return 0;
}
static struct sk_buff *
teql_dequeue(struct Qdisc* sch)
{
struct teql_sched_data *dat = qdisc_priv(sch);
struct sk_buff *skb;
skb = __skb_dequeue(&dat->q);
if (skb == NULL) {
struct net_device *m = dat->m->dev->qdisc->dev;
if (m) {
dat->m->slaves = sch;
netif_wake_queue(m);
}
}
sch->q.qlen = dat->q.qlen + dat->m->dev->qdisc->q.qlen;
return skb;
}
static __inline__ void
teql_neigh_release(struct neighbour *n)
{
if (n)
neigh_release(n);
}
static void
teql_reset(struct Qdisc* sch)
{
struct teql_sched_data *dat = qdisc_priv(sch);
skb_queue_purge(&dat->q);
sch->q.qlen = 0;
teql_neigh_release(xchg(&dat->ncache, NULL));
}
static void
teql_destroy(struct Qdisc* sch)
{
struct Qdisc *q, *prev;
struct teql_sched_data *dat = qdisc_priv(sch);
struct teql_master *master = dat->m;
if ((prev = master->slaves) != NULL) {
do {
q = NEXT_SLAVE(prev);
if (q == sch) {
NEXT_SLAVE(prev) = NEXT_SLAVE(q);
if (q == master->slaves) {
master->slaves = NEXT_SLAVE(q);
if (q == master->slaves) {
master->slaves = NULL;
spin_lock_bh(&master->dev->queue_lock);
qdisc_reset(master->dev->qdisc);
spin_unlock_bh(&master->dev->queue_lock);
}
}
skb_queue_purge(&dat->q);
teql_neigh_release(xchg(&dat->ncache, NULL));
break;
}
} while ((prev = q) != master->slaves);
}
}
static int teql_qdisc_init(struct Qdisc *sch, struct rtattr *opt)
{
struct net_device *dev = sch->dev;
struct teql_master *m = (struct teql_master*)sch->ops;
struct teql_sched_data *q = qdisc_priv(sch);
if (dev->hard_header_len > m->dev->hard_header_len)
return -EINVAL;
if (m->dev == dev)
return -ELOOP;
q->m = m;
skb_queue_head_init(&q->q);
if (m->slaves) {
if (m->dev->flags & IFF_UP) {
if ((m->dev->flags&IFF_POINTOPOINT && !(dev->flags&IFF_POINTOPOINT))
|| (m->dev->flags&IFF_BROADCAST && !(dev->flags&IFF_BROADCAST))
|| (m->dev->flags&IFF_MULTICAST && !(dev->flags&IFF_MULTICAST))
|| dev->mtu < m->dev->mtu)
return -EINVAL;
} else {
if (!(dev->flags&IFF_POINTOPOINT))
m->dev->flags &= ~IFF_POINTOPOINT;
if (!(dev->flags&IFF_BROADCAST))
m->dev->flags &= ~IFF_BROADCAST;
if (!(dev->flags&IFF_MULTICAST))
m->dev->flags &= ~IFF_MULTICAST;
if (dev->mtu < m->dev->mtu)
m->dev->mtu = dev->mtu;
}
q->next = NEXT_SLAVE(m->slaves);
NEXT_SLAVE(m->slaves) = sch;
} else {
q->next = sch;
m->slaves = sch;
m->dev->mtu = dev->mtu;
m->dev->flags = (m->dev->flags&~FMASK)|(dev->flags&FMASK);
}
return 0;
}
/* "teql*" netdevice routines */
static int
__teql_resolve(struct sk_buff *skb, struct sk_buff *skb_res, struct net_device *dev)
{
struct teql_sched_data *q = qdisc_priv(dev->qdisc);
struct neighbour *mn = skb->dst->neighbour;
struct neighbour *n = q->ncache;
if (mn->tbl == NULL)
return -EINVAL;
if (n && n->tbl == mn->tbl &&
memcmp(n->primary_key, mn->primary_key, mn->tbl->key_len) == 0) {
atomic_inc(&n->refcnt);
} else {
n = __neigh_lookup_errno(mn->tbl, mn->primary_key, dev);
if (IS_ERR(n))
return PTR_ERR(n);
}
if (neigh_event_send(n, skb_res) == 0) {
int err;
read_lock(&n->lock);
err = dev->hard_header(skb, dev, ntohs(skb->protocol), n->ha, NULL, skb->len);
read_unlock(&n->lock);
if (err < 0) {
neigh_release(n);
return -EINVAL;
}
teql_neigh_release(xchg(&q->ncache, n));
return 0;
}
neigh_release(n);
return (skb_res == NULL) ? -EAGAIN : 1;
}
static __inline__ int
teql_resolve(struct sk_buff *skb, struct sk_buff *skb_res, struct net_device *dev)
{
if (dev->hard_header == NULL ||
skb->dst == NULL ||
skb->dst->neighbour == NULL)
return 0;
return __teql_resolve(skb, skb_res, dev);
}
static int teql_master_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct teql_master *master = netdev_priv(dev);
struct Qdisc *start, *q;
int busy;
int nores;
int len = skb->len;
struct sk_buff *skb_res = NULL;
start = master->slaves;
restart:
nores = 0;
busy = 0;
if ((q = start) == NULL)
goto drop;
do {
struct net_device *slave = q->dev;
if (slave->qdisc_sleeping != q)
continue;
if (netif_queue_stopped(slave) || ! netif_running(slave)) {
busy = 1;
continue;
}
switch (teql_resolve(skb, skb_res, slave)) {
case 0:
if (netif_tx_trylock(slave)) {
if (!netif_queue_stopped(slave) &&
slave->hard_start_xmit(skb, slave) == 0) {
netif_tx_unlock(slave);
master->slaves = NEXT_SLAVE(q);
netif_wake_queue(dev);
master->stats.tx_packets++;
master->stats.tx_bytes += len;
return 0;
}
netif_tx_unlock(slave);
}
if (netif_queue_stopped(dev))
busy = 1;
break;
case 1:
master->slaves = NEXT_SLAVE(q);
return 0;
default:
nores = 1;
break;
}
__skb_pull(skb, skb->nh.raw - skb->data);
} while ((q = NEXT_SLAVE(q)) != start);
if (nores && skb_res == NULL) {
skb_res = skb;
goto restart;
}
if (busy) {
netif_stop_queue(dev);
return 1;
}
master->stats.tx_errors++;
drop:
master->stats.tx_dropped++;
dev_kfree_skb(skb);
return 0;
}
static int teql_master_open(struct net_device *dev)
{
struct Qdisc * q;
struct teql_master *m = netdev_priv(dev);
int mtu = 0xFFFE;
unsigned flags = IFF_NOARP|IFF_MULTICAST;
if (m->slaves == NULL)
return -EUNATCH;
flags = FMASK;
q = m->slaves;
do {
struct net_device *slave = q->dev;
if (slave == NULL)
return -EUNATCH;
if (slave->mtu < mtu)
mtu = slave->mtu;
if (slave->hard_header_len > LL_MAX_HEADER)
return -EINVAL;
/* If all the slaves are BROADCAST, master is BROADCAST
If all the slaves are PtP, master is PtP
Otherwise, master is NBMA.
*/
if (!(slave->flags&IFF_POINTOPOINT))
flags &= ~IFF_POINTOPOINT;
if (!(slave->flags&IFF_BROADCAST))
flags &= ~IFF_BROADCAST;
if (!(slave->flags&IFF_MULTICAST))
flags &= ~IFF_MULTICAST;
} while ((q = NEXT_SLAVE(q)) != m->slaves);
m->dev->mtu = mtu;
m->dev->flags = (m->dev->flags&~FMASK) | flags;
netif_start_queue(m->dev);
return 0;
}
static int teql_master_close(struct net_device *dev)
{
netif_stop_queue(dev);
return 0;
}
static struct net_device_stats *teql_master_stats(struct net_device *dev)
{
struct teql_master *m = netdev_priv(dev);
return &m->stats;
}
static int teql_master_mtu(struct net_device *dev, int new_mtu)
{
struct teql_master *m = netdev_priv(dev);
struct Qdisc *q;
if (new_mtu < 68)
return -EINVAL;
q = m->slaves;
if (q) {
do {
if (new_mtu > q->dev->mtu)
return -EINVAL;
} while ((q=NEXT_SLAVE(q)) != m->slaves);
}
dev->mtu = new_mtu;
return 0;
}
static __init void teql_master_setup(struct net_device *dev)
{
struct teql_master *master = netdev_priv(dev);
struct Qdisc_ops *ops = &master->qops;
master->dev = dev;
ops->priv_size = sizeof(struct teql_sched_data);
ops->enqueue = teql_enqueue;
ops->dequeue = teql_dequeue;
ops->requeue = teql_requeue;
ops->init = teql_qdisc_init;
ops->reset = teql_reset;
ops->destroy = teql_destroy;
ops->owner = THIS_MODULE;
dev->open = teql_master_open;
dev->hard_start_xmit = teql_master_xmit;
dev->stop = teql_master_close;
dev->get_stats = teql_master_stats;
dev->change_mtu = teql_master_mtu;
dev->type = ARPHRD_VOID;
dev->mtu = 1500;
dev->tx_queue_len = 100;
dev->flags = IFF_NOARP;
dev->hard_header_len = LL_MAX_HEADER;
SET_MODULE_OWNER(dev);
}
static LIST_HEAD(master_dev_list);
static int max_equalizers = 1;
module_param(max_equalizers, int, 0);
MODULE_PARM_DESC(max_equalizers, "Max number of link equalizers");
static int __init teql_init(void)
{
int i;
int err = -ENODEV;
for (i = 0; i < max_equalizers; i++) {
struct net_device *dev;
struct teql_master *master;
dev = alloc_netdev(sizeof(struct teql_master),
"teql%d", teql_master_setup);
if (!dev) {
err = -ENOMEM;
break;
}
if ((err = register_netdev(dev))) {
free_netdev(dev);
break;
}
master = netdev_priv(dev);
strlcpy(master->qops.id, dev->name, IFNAMSIZ);
err = register_qdisc(&master->qops);
if (err) {
unregister_netdev(dev);
free_netdev(dev);
break;
}
list_add_tail(&master->master_list, &master_dev_list);
}
return i ? 0 : err;
}
static void __exit teql_exit(void)
{
struct teql_master *master, *nxt;
list_for_each_entry_safe(master, nxt, &master_dev_list, master_list) {
list_del(&master->master_list);
unregister_qdisc(&master->qops);
unregister_netdev(master->dev);
free_netdev(master->dev);
}
}
module_init(teql_init);
module_exit(teql_exit);
MODULE_LICENSE("GPL");
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