ipv4: fib: Flush all fib_info in fib_table_flush() during netns dismantle.

ipv4: fib: Flush all fib_info in fib_table_flush() during netns dismantle.

Even when fib_table_flush() is called with flush_all true, it does
not flush all fib_info due to this condition:

  !(fi->fib_flags & RTNH_F_DEAD) && !fib_props[fa->fa_type].error)

This creates an implicit ordering between default_device_exit_batch()
and fib_net_exit_batch().

fib_table_flush(flush_all=true) must be called after all devices
are NETDEV_UNREGISTERed, which is after nexthop_flush_dev() marks
RTNH_F_DEAD.

This would cause memory leak if the order were reversed.

fib_table_flush() does not skip non-dead error routes when flush_all
is true:

  !flush_all &&
  !(fi->fib_flags & RTNH_F_DEAD) && fib_props[fa->fa_type].error

Let's merge the two conditions not to skip all non-dead fib_info
during netns dismantle.

Note that we could further apply !flush_all to the basic table
id check and the rtmsg_fib() call in the loop.

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260612063225.455191-2-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>