[CTT-7] Delete the rules while half-closing tcp state entered

This is fixing post-FIN state (by disabling offload post-FIN).
Once the tcp state enters half-closing tcp state (fin wait,
close wait), delete the offload rules.

From this commit, we have done the short term solution for conntrack
tcp timeout issue. Here is what we have done so far.
- Stop updating tcp timeout to avoid updating wrong tcp state
  timeout.
- Update the ESTABLISHED timeout
  nf_conntrack_tcp_timeout_established (432000) after adding
  bidirectional rules.
- Delete the tcp rules when the tcp state has left
  "established".

Here is the long term solution and need to be addressed in follow up
commits.
- Parse the tcp state from netlink conntrack event.
- Build a mapping to trace the tcp state of the tcp conntrack event.
- Update tcp state timeout for {ESTABLISHED (432000), FIN_WAIT (120),
  CLOSE_WAIT (60)}.

Bug: 190783768
Bug: 192804833
Test: atest TetheringCoverageTests

Manual test:
1. Browse on tethered device
2. Check conntrack tcp state is established.
   $ cat /proc/net/nf_conntrack
   ipv4     2 tcp      6 431995 ESTABLISHED src=192.168.207.9
   dst=140.112.8.116 sport=50697 dport=443 ..
3. Check offload rules are added via dumpsys.
   Upstream:
     tcp .. 192.168.207.9:50697 -> 14(rmnet0) 10.224.1.247:50697
     -> 140.112.8.116:443 ..
   Downstream:
     tcp .. 140.112.8.116:443 -> 30(30) 10.224.1.247:50697
     -> 192.168.207.9:50697 ..
4. Stop browsing for a few seconds.
5. Check conntrack tcp state is half-closed.
   $ cat /proc/net/nf_conntrack
   ipv4     2 tcp      6 116 TIME_WAIT src=192.168.207.9
   dst=140.112.8.116 sport=50697 dport=443 ..
5. Check offload rules are removed via dumpsys.
   Upstream:
     (not found)
   Downstream:
     (not found)

Change-Id: I07e27230bf8952acd7828d1f605167758b3bc490

0 files changed, 0 insertions, 0 deletions