selftests/net: l2_tos_ttl_inherit.sh: Ensure environment cleanup on failure.

Use 'set -e' and an exit handler to stop the script if a command fails
and ensure the test environment is cleaned up in any case. Also, handle
the case where the script is interrupted by SIGINT.

The only command that's expected to fail is 'wait $ping_pid', since
it's killed by the script. Handle this case with '|| true' to make it
play well with 'set -e'.

Finally, return the Kselftest SKIP code (4) when the script breaks
because of an environment problem or a command line failure. The 0 and
1 return codes should now reliably indicate that all tests have been
run (0: all tests run and passed, 1: all tests run but at least one
failed, 4: test script didn't run completely).

Fixes: b690842d12fd ("selftests/net: test l2 tunnel TOS/TTL inheriting")
Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Tested-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

selftests/net: l2_tos_ttl_inherit.sh: Run tests in their own netns.

This selftest currently runs half in the current namespace and half in
a netns of its own. Therefore, the test can fail if the current
namespace is already configured with incompatible parameters (for
example if it already has a veth0 interface).

Adapt the script to put both ends of the veth pair in their own netns.
Now veth0 is created in NS0 instead of the current namespace, while
veth1 is set up in NS1 (instead of the 'testing' netns).

The user visible netns names are randomised to minimise the risk of
conflicts with already existing namespaces. The cleanup() function
doesn't need to remove the virtual interface anymore: deleting NS0 and
NS1 automatically removes the virtual interfaces they contained.

We can remove $ns, which was only used to run ip commands in the
'testing' netns (let's use the builtin "-netns" option instead).
However, we still need a similar functionality as ping and tcpdump
now need to run in NS0. So we now have $RUN_NS0 for that.

Fixes: b690842d12fd ("selftests/net: test l2 tunnel TOS/TTL inheriting")
Reported-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Tested-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr>
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

selftests/net: l2_tos_ttl_inherit.sh: Set IPv6 addresses with "nodad".

The ping command can run before DAD completes. In that case, ping may
fail and break the selftest.

We don't need DAD here since we're working on isolated device pairs.

Fixes: b690842d12fd ("selftests/net: test l2 tunnel TOS/TTL inheriting")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

selftests/net: test l2 tunnel TOS/TTL inheriting

There are currently 3 ip tunnels that are capable of carrying
L2 traffic: gretap, vxlan and geneve.
They all are capable to inherit the TOS/TTL for the outer
IP-header from the inner frame.

Add a test that verifies that these fields are correctly inherited.

These tests failed before the following commits:
b09ab9c92e50 ("ip6_tunnel: allow to inherit from VLAN encapsulated IP")
3f8a8447fd0b ("ip6_gre: use actual protocol to select xmit")
41337f52b967 ("ip6_gre: set DSCP for non-IP")
7ae29fd1be43 ("ip_tunnel: allow to inherit from VLAN encapsulated IP")
7074732c8fae ("ip_tunnels: allow VXLAN/GENEVE to inherit TOS/TTL from VLAN")
ca2bb69514a8 ("geneve: do not use RT_TOS for IPv6 flowlabel")
b4ab94d6adaa ("geneve: fix TOS inheriting for ipv4")

Signed-off-by: Matthias May <matthias.may@westermo.com>
Link: https://lore.kernel.org/r/20220817073649.26117-1-matthias.may@westermo.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>