net: Fix userspace RTM_NEWLINK notifications. (d90a909e) · Commits · 戴 / test

I received some bug reports about userspace programs having problems because after RTM_NEWLINK was received they could not immediate access files under /proc/sys/net/ because they had not been registered yet. The original problem was trivially fixed by moving the userspace notification from rtnetlink_event() to the end of register_netdevice(). When testing that change I discovered I was still getting RTM_NEWLINK events before I could access proc and I was also getting RTM_NEWLINK events after I was seeing RTM_DELLINK. Things practically guaranteed to confuse userspace. After a little more investigation these extra notifications proved to be from the new notifiers NETDEV_POST_INIT and NETDEV_UNREGISTER_BATCH hitting the default case in rtnetlink_event, and triggering unnecessary RTM_NEWLINK messages. rtnetlink_event now explicitly handles NETDEV_UNREGISTER_BATCH and NETDEV_POST_INIT to avoid sending the incorrect userspace notifications. Signed-off-by:

Eric W. Biederman <ebiederm@aristanetworks.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/core/dev.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -5035,6 +5035,11 @@ int register_netdevice(struct net_device *dev)
		rollback_registered(dev);
		dev->reg_state = NETREG_UNREGISTERED;
		}
		/*
		* Prevent userspace races by waiting until the network
		* device is fully setup before sending notifications.
		*/
		rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);

		out:
		return ret;
		@@ -5597,6 +5602,12 @@ int dev_change_net_namespace(struct net_device dev, struct net net, const char
		/* Notify protocols, that a new device appeared. */
		call_netdevice_notifiers(NETDEV_REGISTER, dev);

		/*
		* Prevent userspace races by waiting until the network
		* device is fully setup before sending notifications.
		*/
		rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);

		synchronize_net();
		err = 0;
		out:

net/core/rtnetlink.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -1364,15 +1364,15 @@ static int rtnetlink_event(struct notifier_block *this, unsigned long event, voi
		case NETDEV_UNREGISTER:
		rtmsg_ifinfo(RTM_DELLINK, dev, ~0U);
		break;
		case NETDEV_REGISTER:
		rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
		break;
		case NETDEV_UP:
		case NETDEV_DOWN:
		rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP\|IFF_RUNNING);
		break;
		case NETDEV_POST_INIT:
		case NETDEV_REGISTER:
		case NETDEV_CHANGE:
		case NETDEV_GOING_DOWN:
		case NETDEV_UNREGISTER_BATCH:
		break;
		default:
		rtmsg_ifinfo(RTM_NEWLINK, dev, 0);

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