From af3634d4ac652cd93cb97dd2ad2f01536c2cebc7 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Fri, 3 Jul 2026 00:09:17 +0000 Subject: net: Add per-netns netdev unregistration infra. When we need to unregister a netdev in a different netns, we will delegate its unregistration to per-netns work. There are three types of such cross-netns devices: 1. Paired devices (e.g., netkit, veth, vxcan) -> Unregistering one device also deletes its peer, which may reside in another netns. 2. Tunnel devices (e.g., bareudp, geneve, etc) -> Destroying a netns removes devices in another netns if their backend sockets reside in the dying netns 3. Stacked devices (e.g., ipvlan, macvlan, etc) -> Removing the lower device also removes multiple upper devices, each of which may reside in different namespaces. In these cases, we will use unregister_netdevice_queue_net() to queue such potential cross-netns devices for destruction. Each driver must not call both unregister_netdevice_queue_net() and unregister_netdevice_queue() for the same device. See the subsequent veth/bareudp/ipvlan patches for how they avoid double queueing. unregister_netdevice_queue_net() takes net and dev. If dev resides in the net, it simply calls unregister_netdevice_queue(). If dev_net(dev) is different from the net, it enqueues the device to dev_net(dev)->dev_unreg_head and schedules the per-netns work. When __rtnl_net_unlock() is called from the per-netns work (or another thread already holding the lock), unregister_netdevice_many_net() collects the queued devices and calls unregister_netdevice_many() to perform the actual unregistration. During netns dismantle, rtnl_net_flush_workqueue() is called at the end of default_device_exit_batch() to ensure that cross-netns devices in the other alive netns are unregistered. Once RTNL is removed, a device could be moved to another netns while being queued to net->dev_unreg_head. __dev_change_net_namespace() handles this race by acquiring net->dev_unreg_lock of both the old and new netns after dev_set_net() and moving the device between their dev_unreg_head lists. Since dev_set_net() and unregister_netdevice_queue_net() are synchronised by netdev_lock(), the device is either queued to the old netns's dev_unreg_head and then moved, or queued directly to the new netns. Note that unregister_netdevice_move_net() does not need to call rtnl_net_queue_work() because __dev_change_net_namespace() is (supposed to be) called with rtnl_net_lock(). (Not all callers hold it yet, but the race does not happen until all callers are converted and RTNL is removed.) Signed-off-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260703001009.1572444-7-kuniyu@google.com Signed-off-by: Paolo Abeni --- include/net/net_namespace.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/net') diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h index a989019af5f7..501af1999fe8 100644 --- a/include/net/net_namespace.h +++ b/include/net/net_namespace.h @@ -198,6 +198,8 @@ struct net { /* Move to a better place when the config guard is removed. */ struct mutex rtnl_mutex; struct work_struct rtnl_work; + struct list_head dev_unreg_head; + spinlock_t dev_unreg_lock; #endif #if IS_ENABLED(CONFIG_VSOCKETS) struct netns_vsock vsock; -- cgit v1.2.3