There are multiple ways to query for the carrier state: through
rtnetlink, sysfs, and (possibly) ethtool. Synchronize linkwatch
work before these operations so that we don't have a situation
where userspace queries the carrier state between the driver's
carrier off->on transition and linkwatch running and expects it
to work, when really (at least) TX cannot work until linkwatch
has run.
I previously posted a longer explanation of how this applies to
wireless [1] but with this wireless can simply query the state
before sending data, to ensure the kernel is ready for it.
[1] https://lore.kernel.org/all/
346b21d87c69f817ea3c37caceb34f1f56255884.camel@sipsolutions.net/
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20231204214706.303c62768415.I1caedccae72ee5a45c9085c5eb49c145ce1c0dd5@changeid
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
*/
void linkwatch_fire_event(struct net_device *dev);
+/**
+ * linkwatch_sync_dev - sync linkwatch for the given device
+ * @dev: network device to sync linkwatch for
+ *
+ * Sync linkwatch for the given device, removing it from the
+ * pending work list (if queued).
+ */
+void linkwatch_sync_dev(struct net_device *dev);
+
/**
* netif_carrier_ok - test if carrier present
* @dev: network device
write_lock(&dev_base_lock);
dev->reg_state = NETREG_UNREGISTERED;
write_unlock(&dev_base_lock);
- linkwatch_forget_dev(dev);
+ linkwatch_sync_dev(dev);
}
while (!list_empty(&list)) {
#endif
void linkwatch_init_dev(struct net_device *dev);
-void linkwatch_forget_dev(struct net_device *dev);
void linkwatch_run_queue(void);
void dev_addr_flush(struct net_device *dev);
spin_unlock_irq(&lweventlist_lock);
}
-void linkwatch_forget_dev(struct net_device *dev)
+void linkwatch_sync_dev(struct net_device *dev)
{
unsigned long flags;
int clean = 0;
{
struct net_device *netdev = to_net_dev(dev);
- if (netif_running(netdev))
+ if (netif_running(netdev)) {
+ /* Synchronize carrier state with link watch,
+ * see also rtnl_getlink().
+ */
+ linkwatch_sync_dev(netdev);
+
return sysfs_emit(buf, fmt_dec, !!netif_carrier_ok(netdev));
+ }
return -EINVAL;
}
if (nskb == NULL)
goto out;
+ /* Synchronize the carrier state so we don't report a state
+ * that we're not actually going to honour immediately; if
+ * the driver just did a carrier off->on transition, we can
+ * only TX if link watch work has run, but without this we'd
+ * already report carrier on, even if it doesn't work yet.
+ */
+ linkwatch_sync_dev(dev);
+
err = rtnl_fill_ifinfo(nskb, dev, net,
RTM_NEWLINK, NETLINK_CB(skb).portid,
nlh->nlmsg_seq, 0, 0, ext_filter_mask,
u32 ethtool_op_get_link(struct net_device *dev)
{
+ /* Synchronize carrier state with link watch, see also rtnl_getlink() */
+ linkwatch_sync_dev(dev);
+
return netif_carrier_ok(dev) ? 1 : 0;
}
EXPORT_SYMBOL(ethtool_op_get_link);