[syslog] Fixes syslog test case to add a route to PTF server

[shlomibitton]

Signed-off-by: Shlomi Bitton [email protected]

Description of PR

Summary:
Fixes # (issue)

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Approach

What is the motivation for this PR?

Current syslog test implementation is not making sure the DUT has a route to the PTF server.
This causing the test to fail as a result of:
Failed: Test syslog message not seen on the server after 10s

How did you do it?

1. Get default GW of eth0 interface.
2. Get PTF server IP address.
3. Add a static route from eth0 default GW to the PTF server.
4. At the end of the test, remove this route.

How did you verify/test it?

1. Try to ping to PTF server from DUT and get: "Destination Host Unreachable"
2. Run test and see it is passing.

Any platform specific information?

Supported testbed topology if it's a new test case?

Documentation

[wangxin]

Can you consider adding the subnet of PTF management IP to ansible variable forced_mgmt_routes?

For example, assume:

• Your PTF mgmt IP is on subnet 10.10.10.0/24:
• Your DUT is defined as children of group lab, then variables defined in sonic-mgmt/ansible/group_vars/lab/*.yml would be visible.

sonic-mgmt/ansible/group_vars/lab/lab.yml:

forced_mgmt_routes: ['10.10.10.0/24']

This information will go to minigraph.xml, then routing rules will be added to /etc/network/interfaces while loading minigraph on DUT. With the routing rules, the default management gateway will always be used for accessing 10.10.10.0/24.

This can ensure that the DUT always has route to PTF management IP via the management default gateway.

By this method, you can also force to use management default gateway for other prefixes, like NTP server, etc.

[wangxin]

Please consider using forced_mgmt_routes.