IPA Issue - Downlink Throughput Degradation

Problem

In the customer environment, the downlink throughput will drop to 30% after 8-12 hours.

Image Not Showing Possible Reasons

The workaround to resolve this issue is to reboot or rescan.

When the traffic is sent by TCP, IPA will learn the rule and send the traffic by this rule. (The maximum rule number for IPA is 500)
Ideally, this rule should be deleted shortly after the traffic is finished.
But in fact, the rule was not deleted and timeout showed five days, so the rule number will increase until it hits the limit.

To mitigate this issue, we modify the timeout manually from five days to ten minutes.

The ipacm daemon will periodically update the timeout of the conntrack that it has recorded.
This action is used to prevent the conntrack from being removed because the Linux kernel is unaware of the traffic that go through IPA directly.

To resolve this race condition, the timeout of conntrack must be updated only when its state is ESTABLISHED.
And we found there are some fixes for this issue in qcom-opensource repositories.
(The ipanat library has been separated into another repository in newer versions)
dataipa, data-ipa-cfg-mgr
The patch used to solve this problem is located at the ~/mojito-sdk/trunk/buildroot/external/package/SdxPkgs/meta-qti-data/data-ipa-cfg-mgr/LE.UM.4.4.2.r1-02200-SDX55/0006-check-redirect-flag-for-nat-entry.patch, which combines the above two fixes from qcom opensource repository.