selftests/net/lib: update busywait timeout value

The busywait timeout value is a millisecond, not a second. So the
current setting 2 is too small. On slow/busy host (or VMs) the
current timeout can expire even on "correct" execution, causing random
failures. Let's copy the WAIT_TIMEOUT from forwarding/lib.sh and set
BUSYWAIT_TIMEOUT here.

Fixes: 25ae948b4478 ("selftests/net: add lib.sh")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240124061344.1864484-1-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

selftests/net: add variable NS_LIST for lib.sh

Add a global variable NS_LIST to store all the namespaces that setup_ns
created, so the caller could call cleanup_all_ns() instead of remember
all the netns names when using cleanup_ns().

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20231213060856.4030084-2-liuhangbin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

selftests/net: add lib.sh

Add a lib.sh for net selftests. This file can be used to define commonly
used variables and functions. Some commonly used functions can be moved
from forwarding/lib.sh to this lib file. e.g. busywait().

Add function setup_ns() for user to create unique namespaces with given
prefix name.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>