selftests: drv-net: add require_XYZ() helpers for validating env

Wrap typical checks like whether given command used by the test
is available in helpers.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240420025237.3309296-8-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

selftests: drv-net: add a TCP ping test case (and useful helpers)

More complex tests often have to spawn a background process,
like a server which will respond to requests or tcpdump.

Add support for creating such processes using the with keyword:

with bkg("my-daemon", ..):
# my-daemon is alive in this block

My initial thought was to add this support to cmd() directly
but it runs the command in the constructor, so by the time
we __enter__ it's too late to make sure we used "background=True".

Second useful helper transplanted from net_helper.sh is
wait_port_listen().

The test itself uses socat, which insists on v6 addresses
being wrapped in [], it's not the only command which requires
this format, so add the wrapped address to env. The hope
is to save test code from checking if address is v6.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240420025237.3309296-7-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

selftests: net: support matching cases by name prefix

While writing tests with a lot more cases I got tired of having
to jump back and forth to add the name of the test to the ksft_run()
list. Most unittest frameworks do some name matching, e.g. assume
that functions with names starting with test_ are test cases.

Support similar flow in ksft_run(). Let the author list the desired
prefixes. globals() need to be passed explicitly, IDK how to work
around that.

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240420025237.3309296-6-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

selftests: drv-net: add a trivial ping test

Add a very simple test for testing with a remote system.
Both IPv4 and IPv6 connectivity is optional, later change
will add checks to skip tests based on available addresses.

Using netdevsim:

$ ./run_kselftest.sh -t drivers/net:ping.py
TAP version 13
1..1
# timeout set to 45
# selftests: drivers/net: ping.py
# KTAP version 1
# 1..2
# ok 1 ping.test_v4
# ok 2 ping.test_v6
# # Totals: pass:2 fail:0 xfail:0 xpass:0 skip:0 error:0
ok 1 selftests: drivers/net: ping.py

Command line SSH:

$ NETIF=virbr0 REMOTE_TYPE=ssh REMOTE_ARGS=root@192.168.122.123 \
LOCAL_V4=192.168.122.1 REMOTE_V4=192.168.122.123 \
./tools/testing/selftests/drivers/net/ping.py
KTAP version 1
1..2
ok 1 ping.test_v4
ok 2 ping.test_v6 # SKIP Test requires IPv6 connectivity
# Totals: pass:1 fail:0 xfail:1 xpass:0 skip:0 error:0

Existing devices placed in netns (and using net.config):

$ cat drivers/net/net.config
NETIF=veth0
REMOTE_TYPE=netns
REMOTE_ARGS=red
LOCAL_V4="192.168.1.1"
REMOTE_V4="192.168.1.2"

$ ./run_kselftest.sh -t drivers/net:ping.py
TAP version 13
1..1
# timeout set to 45
# selftests: drivers/net: ping.py
# KTAP version 1
# 1..2
# ok 1 ping.test_v4
# ok 2 ping.test_v6 # SKIP Test requires IPv6 connectivity
# # Totals: pass:1 fail:0 xfail:1 xpass:0 skip:0 error:0

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240420025237.3309296-5-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>