net: Add net_passive_inc() and net_passive_dec().

[ Upstream commit e57a6320 ]

net_drop_ns() is NULL when CONFIG_NET_NS is disabled.

The next patch introduces a function that increments
and decrements net->passive.

As a prep, let's rename and export net_free() to
net_passive_dec() and add net_passive_inc().

Suggested-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/netdev/CANn89i+oUCt2VGvrbrweniTendZFEh+nwS=uonc004-aPkWy-Q@mail.gmail.com/


Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250217191129.19967-2-kuniyu@amazon.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 59b33fab ("smb: client: fix netns refcount leak after net_passive changes")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>