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Commit 4edf547b authored by Johannes Berg's avatar Johannes Berg Committed by David S. Miller
Browse files

net: explain netns notifiers a little better 



Eric explained this to me -- and afterwards the comment
made sense, but not before. Add the the critical point
about interfaces having to be gone from the netns before
subsys notifiers are called.

Signed-off-by: default avatarJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 27e09551

include/net/net_namespace.h

+9 −7
Original line number Diff line number Diff line
@@ -239,13 +239,15 @@ struct pernet_operations { 
 * needs per network namespace operations use device pernet operations,

 * otherwise use pernet subsys operations.

 *

 * This is critically important.  Most of the network code cleanup

 * runs with the assumption that dev_remove_pack has been called so no

 * new packets will arrive during and after the cleanup functions have

 * been called.  dev_remove_pack is not per namespace so instead the

 * guarantee of no more packets arriving in a network namespace is

 * provided by ensuring that all network devices and all sockets have

 * left the network namespace before the cleanup methods are called.

 * Network interfaces need to be removed from a dying netns _before_

 * subsys notifiers can be called, as most of the network code cleanup

 * (which is done from subsys notifiers) runs with the assumption that

 * dev_remove_pack has been called so no new packets will arrive during

 * and after the cleanup functions have been called.  dev_remove_pack

 * is not per namespace so instead the guarantee of no more packets

 * arriving in a network namespace is provided by ensuring that all

 * network devices and all sockets have left the network namespace

 * before the cleanup methods are called.

 *

 * For the longest time the ipv4 icmp code was registered as a pernet

 * device which caused kernel oops, and panics during network