bonding: add min links parameter to 802.3ad

This adds support for a configuring the minimum number of links that
must be active before asserting carrier. It is similar to the Cisco
EtherChannel min-links feature. This allows setting the minimum number
of member ports that must be up (link-up state) before marking the
bond device as up (carrier on). This is useful for situations where
higher level services such as clustering want to ensure a minimum
number of low bandwidth links are active before switchover.

See:
   http://bugzilla.vyatta.com/show_bug.cgi?id=7196

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: Andy Gospodarek <andy@greyhouse.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_procfs.c

@@ -125,6 +125,7 @@ static void bond_info_show_master(struct seq_file *seq)
 		seq_puts(seq, "\n802.3ad info\n");
 		seq_printf(seq, "LACP rate: %s\n",
 			   (bond->params.lacp_fast) ? "fast" : "slow");
+		seq_printf(seq, "Min links: %d\n", bond->params.min_links);
 		seq_printf(seq, "Aggregator selection policy (ad_select): %s\n",
 			   ad_select_tbl[bond->params.ad_select].modename);