Signed-off-by: maipbui <maibui@microsoft.com>
#### Why I did it
`subprocess` is used with `shell=True`, which is very dangerous for shell injection.
`os` - not secure against maliciously constructed input and dangerous if used to evaluate dynamic content
#### How I did it
remove `shell=True`, use `shell=False`
Replace `os` by `subprocess`
- Consolidate the two [Service] sections by moving the ExecStartPre line for mark_dhcp_packet.py to the first section and removing the second.
- Make the mark_dhcp_packet.py file executable
- Also clean up mark_dhcp_packet.py
- Remove unused imports
- Fix spacing and line lengths to conform to PEP8
Signed-off-by: Lawrence Lee <lawlee@microsoft.com>
- add a new service "mark_dhcp_packet" to mux container
- apply packet marks on a per-interface basis in ebtables
- write packet marks to "DHCP_PACKET_MARK" table in state_db
