geneve: convert config to RCU-protected pointer

geneve_changelink() currently updates configuration by copying it over
the old one using memcpy() under RTNL, forcing data path pause via
geneve_quiesce() and synchronize_net() to avoid reading torn values.

Convert geneve->cfg to an RCU-protected pointer, allowing lockless
and safe reads under RCU read lock without synchronization overhead.

Key changes:
- Introduced geneve_config_alloc/free() helpers for lifecycle.
- geneve_configure() allocates config and publishes it via RCU.
- Setting dev->priv_destructor = geneve_free_dev handles config cleanup
  if register_netdevice() fails or during netdev unregistration.
- geneve_changelink() performs RCU swap; old config is freed via call_rcu_hurry().
- Allocates new dst_cache during changelink to prevent pcpu sharing.
- Removed geneve_quiesce/unquiesce() and synchronize_net() from changelink.
- Added rcu_barrier() to module exit to wait for pending callbacks.
- Updated data path to use rcu_dereference().
- Updated geneve_fill_info() to use rtnl_dereference() for now.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260707145331.3717941-3-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

0 files changed, 0 insertions, 0 deletions