ipconfig: add informative timeout messages while waiting for carrier

Commit 3fb72f1e6e6165c5f495e8dc11c5bbd14c73385c ("ipconfig wait
for carrier") added a "wait for carrier on at least one interface"
policy, with a worst case maximum wait of two minutes.

However, if you encounter this, you won't get any feedback from
the console as to the nature of what is going on. You just see
the booting process hang for two minutes and then continue.

Here we add a message so the user knows what is going on, and
hence can take action to rectify the situation (e.g. fix network
cable or whatever.) After the 1st 10s pause, output now begins
that looks like this:

Waiting up to 110 more seconds for network.
Waiting up to 100 more seconds for network.
Waiting up to 90 more seconds for network.
Waiting up to 80 more seconds for network.
...

Since most systems will have no problem getting link/carrier in the
1st 10s, the only people who will see these messages are people with
genuine issues that need to be resolved.

Signed-off-by: Paul Gortmaker <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/ipv4/ipconfig.c

···
 	struct ic_device *d, **last;
 	struct net_device *dev;
 	unsigned short oflags;
-	unsigned long start;
+	unsigned long start, next_msg;
 
 	last = &ic_first_dev;
 	rtnl_lock();
···
 
 	/* wait for a carrier on at least one device */
 	start = jiffies;
+	next_msg = start + msecs_to_jiffies(CONF_CARRIER_TIMEOUT/12);
 	while (jiffies - start < msecs_to_jiffies(CONF_CARRIER_TIMEOUT)) {
+		int wait, elapsed;
+
 		for_each_netdev(&init_net, dev)
 			if (ic_is_init_dev(dev) && netif_carrier_ok(dev))
 				goto have_carrier;
 
 		msleep(1);
+
+		if time_before(jiffies, next_msg)
+			continue;
+
+		elapsed = jiffies_to_msecs(jiffies - start);
+		wait = (CONF_CARRIER_TIMEOUT - elapsed + 500)/1000;
+		pr_info("Waiting up to %d more seconds for network.\n", wait);
+		next_msg = jiffies + msecs_to_jiffies(CONF_CARRIER_TIMEOUT/12);
 	}
 have_carrier:
 	rtnl_unlock();