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net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()
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Le dimanche 05 décembre 2010 à 09:19 +0100, Eric Dumazet a écrit :

> Hmm..
>
> If somebody can explain why RTNL is held in arp_ioctl() (and therefore
> in arp_req_delete()), we might first remove RTNL use in arp_ioctl() so
> that your patch can be applied.
>
> Right now it is not good, because RTNL wont be necessarly held when you
> are going to call arp_invalidate() ?

While doing this analysis, I found a refcount bug in llc, I'll send a
patch for net-2.6

Meanwhile, here is the patch for net-next-2.6

Your patch then can be applied after mine.

Thanks

[PATCH] net: RCU conversion of dev_getbyhwaddr() and arp_ioctl()

dev_getbyhwaddr() was called under RTNL.

Rename it to dev_getbyhwaddr_rcu() and change all its caller to now use
RCU locking instead of RTNL.

Change arp_ioctl() to use RCU instead of RTNL locking.

Note: this fix a dev refcount bug in llc

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Dec 8, 2010
1 parent a2d4b65 commit 941666c
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Showing 5 changed files with 27 additions and 27 deletions.
3 changes: 2 additions & 1 deletion include/linux/netdevice.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1360,7 +1360,8 @@ static inline struct net_device *first_net_device(struct net *net)

extern int netdev_boot_setup_check(struct net_device *dev);
extern unsigned long netdev_boot_base(const char *prefix, int unit);
extern struct net_device *dev_getbyhwaddr(struct net *net, unsigned short type, char *hwaddr);
extern struct net_device *dev_getbyhwaddr_rcu(struct net *net, unsigned short type,
const char *hwaddr);
extern struct net_device *dev_getfirstbyhwtype(struct net *net, unsigned short type);
extern struct net_device *__dev_getfirstbyhwtype(struct net *net, unsigned short type);
extern void dev_add_pack(struct packet_type *pt);
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17 changes: 7 additions & 10 deletions net/core/dev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -743,34 +743,31 @@ struct net_device *dev_get_by_index(struct net *net, int ifindex)
EXPORT_SYMBOL(dev_get_by_index);

/**
* dev_getbyhwaddr - find a device by its hardware address
* dev_getbyhwaddr_rcu - find a device by its hardware address
* @net: the applicable net namespace
* @type: media type of device
* @ha: hardware address
*
* Search for an interface by MAC address. Returns NULL if the device
* is not found or a pointer to the device. The caller must hold the
* rtnl semaphore. The returned device has not had its ref count increased
* is not found or a pointer to the device. The caller must hold RCU
* The returned device has not had its ref count increased
* and the caller must therefore be careful about locking
*
* BUGS:
* If the API was consistent this would be __dev_get_by_hwaddr
*/

struct net_device *dev_getbyhwaddr(struct net *net, unsigned short type, char *ha)
struct net_device *dev_getbyhwaddr_rcu(struct net *net, unsigned short type,
const char *ha)
{
struct net_device *dev;

ASSERT_RTNL();

for_each_netdev(net, dev)
for_each_netdev_rcu(net, dev)
if (dev->type == type &&
!memcmp(dev->dev_addr, ha, dev->addr_len))
return dev;

return NULL;
}
EXPORT_SYMBOL(dev_getbyhwaddr);
EXPORT_SYMBOL(dev_getbyhwaddr_rcu);

struct net_device *__dev_getfirstbyhwtype(struct net *net, unsigned short type)
{
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6 changes: 3 additions & 3 deletions net/ieee802154/af_ieee802154.c
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Original file line number Diff line number Diff line change
Expand Up @@ -52,11 +52,11 @@ struct net_device *ieee802154_get_dev(struct net *net,

switch (addr->addr_type) {
case IEEE802154_ADDR_LONG:
rtnl_lock();
dev = dev_getbyhwaddr(net, ARPHRD_IEEE802154, addr->hwaddr);
rcu_read_lock();
dev = dev_getbyhwaddr_rcu(net, ARPHRD_IEEE802154, addr->hwaddr);
if (dev)
dev_hold(dev);
rtnl_unlock();
rcu_read_unlock();
break;
case IEEE802154_ADDR_SHORT:
if (addr->pan_id == 0xffff ||
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17 changes: 9 additions & 8 deletions net/ipv4/arp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1017,13 +1017,14 @@ static int arp_req_set_proxy(struct net *net, struct net_device *dev, int on)
IPV4_DEVCONF_ALL(net, PROXY_ARP) = on;
return 0;
}
if (__in_dev_get_rtnl(dev)) {
IN_DEV_CONF_SET(__in_dev_get_rtnl(dev), PROXY_ARP, on);
if (__in_dev_get_rcu(dev)) {
IN_DEV_CONF_SET(__in_dev_get_rcu(dev), PROXY_ARP, on);
return 0;
}
return -ENXIO;
}

/* must be called with rcu_read_lock() */
static int arp_req_set_public(struct net *net, struct arpreq *r,
struct net_device *dev)
{
Expand All @@ -1033,7 +1034,7 @@ static int arp_req_set_public(struct net *net, struct arpreq *r,
if (mask && mask != htonl(0xFFFFFFFF))
return -EINVAL;
if (!dev && (r->arp_flags & ATF_COM)) {
dev = dev_getbyhwaddr(net, r->arp_ha.sa_family,
dev = dev_getbyhwaddr_rcu(net, r->arp_ha.sa_family,
r->arp_ha.sa_data);
if (!dev)
return -ENODEV;
Expand Down Expand Up @@ -1225,10 +1226,10 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
if (!(r.arp_flags & ATF_NETMASK))
((struct sockaddr_in *)&r.arp_netmask)->sin_addr.s_addr =
htonl(0xFFFFFFFFUL);
rtnl_lock();
rcu_read_lock();
if (r.arp_dev[0]) {
err = -ENODEV;
dev = __dev_get_by_name(net, r.arp_dev);
dev = dev_get_by_name_rcu(net, r.arp_dev);
if (dev == NULL)
goto out;

Expand All @@ -1252,12 +1253,12 @@ int arp_ioctl(struct net *net, unsigned int cmd, void __user *arg)
break;
case SIOCGARP:
err = arp_req_get(&r, dev);
if (!err && copy_to_user(arg, &r, sizeof(r)))
err = -EFAULT;
break;
}
out:
rtnl_unlock();
rcu_read_unlock();
if (cmd == SIOCGARP && !err && copy_to_user(arg, &r, sizeof(r)))
err = -EFAULT;
return err;
}

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11 changes: 6 additions & 5 deletions net/llc/af_llc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -316,9 +316,9 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
if (unlikely(addr->sllc_family != AF_LLC))
goto out;
rc = -ENODEV;
rtnl_lock();
rcu_read_lock();
if (sk->sk_bound_dev_if) {
llc->dev = dev_get_by_index(&init_net, sk->sk_bound_dev_if);
llc->dev = dev_get_by_index_rcu(&init_net, sk->sk_bound_dev_if);
if (llc->dev) {
if (!addr->sllc_arphrd)
addr->sllc_arphrd = llc->dev->type;
Expand All @@ -329,14 +329,15 @@ static int llc_ui_bind(struct socket *sock, struct sockaddr *uaddr, int addrlen)
!llc_mac_match(addr->sllc_mac,
llc->dev->dev_addr)) {
rc = -EINVAL;
dev_put(llc->dev);
llc->dev = NULL;
}
}
} else
llc->dev = dev_getbyhwaddr(&init_net, addr->sllc_arphrd,
llc->dev = dev_getbyhwaddr_rcu(&init_net, addr->sllc_arphrd,
addr->sllc_mac);
rtnl_unlock();
if (llc->dev)
dev_hold(llc->dev);
rcu_read_unlock();
if (!llc->dev)
goto out;
if (!addr->sllc_sap) {
Expand Down

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