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authorJohn Fastabend <john.fastabend@gmail.com>2017-07-17 09:30:02 -0700
committerDavid S. Miller <davem@davemloft.net>2017-07-17 09:48:06 -0700
commit2ddf71e23cc246e95af72a6deed67b4a50a7b81c (patch)
treeb5153dd5672bf7f6af6311df36b6037eb652b7c2 /samples
parent11393cc9b9be2a1f61559e6fb9c27bc8fa20b1ff (diff)
download96b-common-2ddf71e23cc246e95af72a6deed67b4a50a7b81c.tar.gz
net: add notifier hooks for devmap bpf map
The BPF map devmap holds a refcnt on the net_device structure when it is in the map. We need to do this to ensure on driver unload we don't lose a dev reference. However, its not very convenient to have to manually unload the map when destroying a net device so add notifier handlers to do the cleanup automatically. But this creates a race between update/destroy BPF syscall and programs and the unregister netdev hook. Unfortunately, the best I could come up with is either to live with requiring manual removal of net devices from the map before removing the net device OR to add a mutex in devmap to ensure the map is not modified while we are removing a device. The fallout also requires that BPF programs no longer update/delete the map from the BPF program side because the mutex may sleep and this can not be done from inside an rcu critical section. This is not a real problem though because I have not come up with any use cases where this is actually useful in practice. If/when we come up with a compelling user for this we may need to revisit this. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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