rtnl: expose carrier value with possibility to set it

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/operstates.txt

@@ -88,6 +88,10 @@ set this flag. On netif_carrier_off(), the scheduler stops sending
 packets. The name 'carrier' and the inversion are historical, think of
 it as lower layer.
 
+Note that for certain kind of soft-devices, which are not managing any
+real hardware, there is possible to set this bit from userpsace.
+One should use TVL IFLA_CARRIER to do so.
+
 netif_carrier_ok() can be used to query that bit.
 
 __LINK_STATE_DORMANT, maps to IFF_DORMANT:

include/uapi/linux/if_link.h

@@ -142,6 +142,7 @@ enum {
 #define IFLA_PROMISCUITY IFLA_PROMISCUITY
 	IFLA_NUM_TX_QUEUES,
 	IFLA_NUM_RX_QUEUES,
+	IFLA_CARRIER,
 	__IFLA_MAX
 };
 

net/core/rtnetlink.c

@@ -780,6 +780,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
 	       + nla_total_size(4) /* IFLA_MTU */
 	       + nla_total_size(4) /* IFLA_LINK */
 	       + nla_total_size(4) /* IFLA_MASTER */
+	       + nla_total_size(1) /* IFLA_CARRIER */
 	       + nla_total_size(4) /* IFLA_PROMISCUITY */
 	       + nla_total_size(4) /* IFLA_NUM_TX_QUEUES */
 	       + nla_total_size(4) /* IFLA_NUM_RX_QUEUES */
@@ -909,6 +910,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 	     nla_put_u32(skb, IFLA_LINK, dev->iflink)) ||
 	    (dev->master &&
 	     nla_put_u32(skb, IFLA_MASTER, dev->master->ifindex)) ||
+	    nla_put_u8(skb, IFLA_CARRIER, netif_carrier_ok(dev)) ||
 	    (dev->qdisc &&
 	     nla_put_string(skb, IFLA_QDISC, dev->qdisc->ops->id)) ||
 	    (dev->ifalias &&
@@ -1108,6 +1110,7 @@ const struct nla_policy ifla_policy[IFLA_MAX+1] = {
 	[IFLA_MTU]		= { .type = NLA_U32 },
 	[IFLA_LINK]		= { .type = NLA_U32 },
 	[IFLA_MASTER]		= { .type = NLA_U32 },
+	[IFLA_CARRIER]		= { .type = NLA_U8 },
 	[IFLA_TXQLEN]		= { .type = NLA_U32 },
 	[IFLA_WEIGHT]		= { .type = NLA_U32 },
 	[IFLA_OPERSTATE]	= { .type = NLA_U8 },
@@ -1438,6 +1441,13 @@ static int do_setlink(struct net_device *dev, struct ifinfomsg *ifm,
 		modified = 1;
 	}
 
+	if (tb[IFLA_CARRIER]) {
+		err = dev_change_carrier(dev, nla_get_u8(tb[IFLA_CARRIER]));
+		if (err)
+			goto errout;
+		modified = 1;
+	}
+
 	if (tb[IFLA_TXQLEN])
 		dev->tx_queue_len = nla_get_u32(tb[IFLA_TXQLEN]);