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

This reverts commit 118b5b578a15dbb82146ae5d14d67a2cc79340cd.

Reason for revert: 
Stop releasing this commit because it needs more test coverage.

Bug: 190783768
Bug: 192804833
Change-Id: Ie26f6e528999da42cfa66a5f6c1f187ad2276ae1
Test: atest TetheringCoverageTests
diff --git a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
index c99007e..97ef380 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
@@ -1572,10 +1572,6 @@
             final Tether4Key downstream4Key = makeTetherDownstream4Key(e, tetherClient,
                     upstreamIndex);
 
-            final boolean isConntrackEventDelete =
-                    e.msgType == (NetlinkConstants.NFNL_SUBSYS_CTNETLINK << 8
-                    | NetlinkConstants.IPCTNL_MSG_CT_DELETE);
-
             // Using the timeout to distinguish tcp state is not a decent way. Need to fix.
             // The received IPCTNL_MSG_CT_NEW must pass ConntrackMonitor#isEstablishedNatSession
             // which checks CTA_STATUS. It implies that this entry has at least reached tcp
@@ -1588,18 +1584,8 @@
                     && e.tupleOrig.protoNum == OsConstants.IPPROTO_TCP
                     && (e.timeoutSec >= NF_CONNTRACK_TCP_TIMEOUT_UNACKNOWLEDGED);
 
-            final boolean isTcpNonEstablished =
-                    e.msgType == (NetlinkConstants.NFNL_SUBSYS_CTNETLINK << 8
-                    | NetlinkConstants.IPCTNL_MSG_CT_NEW)
-                    && e.tupleOrig.protoNum == OsConstants.IPPROTO_TCP
-                    && (e.timeoutSec < NF_CONNTRACK_TCP_TIMEOUT_UNACKNOWLEDGED);
-
-            // Delete the BPF rules:
-            // 1. Contrack event IPCTNL_MSG_CT_DELETE received.
-            // 2. For TCP conntrack entry, the tcp state has left "established" and going to be
-            // closed.
-            // TODO: continue to offload half-closed tcp connections.
-            if (isConntrackEventDelete || isTcpNonEstablished) {
+            if (e.msgType == (NetlinkConstants.NFNL_SUBSYS_CTNETLINK << 8
+                    | NetlinkConstants.IPCTNL_MSG_CT_DELETE)) {
                 final boolean deletedUpstream = mBpfCoordinatorShim.tetherOffloadRuleRemove(
                         UPSTREAM, upstream4Key);
                 final boolean deletedDownstream = mBpfCoordinatorShim.tetherOffloadRuleRemove(
@@ -1614,7 +1600,6 @@
                     Log.wtf(TAG, "The bidirectional rules should be removed concurrently ("
                             + "upstream: " + deletedUpstream
                             + ", downstream: " + deletedDownstream + ")");
-                    // TODO: consider better error handling for the stubs {rule, limit, ..}.
                     return;
                 }