netdev - [PATCH net-next v3] net-loopback: set lo dev initial state to UP

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Date:   Mon,  1 Feb 2021 15:34:45 -0800
From:   Jian Yang <jianyang.kernel@...il.com>
To:     davem@...emloft.net, kuba@...nel.org, netdev@...r.kernel.org
Cc:     Mahesh Bandewar <maheshb@...gle.com>,
        Jian Yang <jianyang@...gle.com>
Subject: [PATCH net-next v3] net-loopback: set lo dev initial state to UP

From: Jian Yang <jianyang@...gle.com>

Traditionally loopback devices come up with initial state as DOWN for
any new network-namespace. This would mean that anyone needing this
device would have to bring this UP by issuing something like 'ip link
set lo up'. This can be avoided if the initial state is set as UP.

Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
Signed-off-by: Jian Yang <jianyang@...gle.com>
---
v3:
  * Addressed Jakub's comment to remove the sysctl knob

v2:
  * Updated sysctl name from `netdev_loopback_state` to `loopback_init_state`
  * Fixed the linking error when CONFIG_SYSCTL is not defined

 drivers/net/loopback.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index a1c77cc00416..24487ec17f8b 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -219,6 +219,12 @@ static __net_init int loopback_net_init(struct net *net)
 
 	BUG_ON(dev->ifindex != LOOPBACK_IFINDEX);
 	net->loopback_dev = dev;
+
+	/* bring loopback device UP */
+	rtnl_lock();
+	dev_open(dev, NULL);
+	rtnl_unlock();
+
 	return 0;
 
 out_free_netdev:
-- 
2.30.0.365.g02bc693789-goog