[NET] core: add RFC2863 operstate

this patch adds a dormant flag to network devices, RFC2863 operstate derived
from these flags and possibility for userspace interaction. It allows drivers
to signal that a device is unusable for user traffic without disabling
queueing (and therefore the possibility for protocol establishment traffic to
flow) and a userspace supplicant (WPA, 802.1X) to mark a device unusable
without changes to the driver.

It is the result of our long discussion. However I must admit that it
represents what Jamal and I agreed on with compromises towards Krzysztof, but
Thomas and Krzysztof still disagree with some parts. Anyway I think it should
be applied.

Signed-off-by: Stefan Rompf <stefan@loplof.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 40 insertions, 0 deletions

diff --git a/net/core/link_watch.c b/net/core/link_watch.c
index d43d1201275..e82a451d330 100644
--- a/net/core/link_watch.c
+++ b/net/core/link_watch.c
@@ -49,6 +49,45 @@ struct lw_event {
 /* Avoid kmalloc() for most systems */
 static struct lw_event singleevent;
 
+static unsigned char default_operstate(const struct net_device *dev)
+{
+	if (!netif_carrier_ok(dev))
+		return (dev->ifindex != dev->iflink ?
+			IF_OPER_LOWERLAYERDOWN : IF_OPER_DOWN);
+
+	if (netif_dormant(dev))
+		return IF_OPER_DORMANT;
+
+	return IF_OPER_UP;
+}
+
+
+static void rfc2863_policy(struct net_device *dev)
+{
+	unsigned char operstate = default_operstate(dev);
+
+	if (operstate == dev->operstate)
+		return;
+
+	write_lock_bh(&dev_base_lock);
+
+	switch(dev->link_mode) {
+	case IF_LINK_MODE_DORMANT:
+		if (operstate == IF_OPER_UP)
+			operstate = IF_OPER_DORMANT;
+		break;
+
+	case IF_LINK_MODE_DEFAULT:
+	default:
+		break;
+	};
+
+	dev->operstate = operstate;
+
+	write_unlock_bh(&dev_base_lock);
+}
+
+
 /* Must be called with the rtnl semaphore held */
 void linkwatch_run_queue(void)
 {
@@ -74,6 +113,7 @@ void linkwatch_run_queue(void)
 		 */
 		clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
 
+		rfc2863_policy(dev);
 		if (dev->flags & IFF_UP) {
 			if (netif_carrier_ok(dev)) {
 				WARN_ON(dev->qdisc_sleeping == &noop_qdisc);