After some tests on new ZTE units (like MC888 or MC889), I've found that when these are put in Router mode (using repacked firmware), the packet acceleration (IPA) is broken, and all traffic is software accelerated.
This issue seems related to a permission problem when the mount-copybind script should mount the IPACM_cfg.xml file from the filesystem /etc_rw. The script checks if the stat of the files are the same, and if not, it overwrites the default configuration into /etc_rw. This causes ipacm to read the wrong LAN address and break the acceleration.
In the /etc/data/ipa directory, there is the stock Qualcomm configuration using the standard subnet 192.168.225.0/24, while ZTE uses its custom scripts and binaries to avoid using / as Read-Write. When you extract the rootfs UBI volume, even with the -k flag of ubireader or the --preserve flag of ubidump, the IPACM_cfg.xml file in /etc/data/ipa gets incorrect permissions. This file should be owned by the radio user and group, with permissions set to 755.
So before repacking the rootfs, be sure to change the ownership and permissions of this file using these commands:
chown 1001:1001 PATHetc/data/ipa/IPACM_cfg.xml
chmod 755 /etc/data/ipa/IPACM_cfg.xml
Please note that UID\GID 1001 are the user radio on the CPE
I want to give a big thanks to my friend @awvarez who helped me find and fix this problem :)
It seems that the ubireader tool, in some cases, doesn’t preserve file ownership (I encountered many issues when repacking a ZTE MC888 Ultra/MC888A Ultra). I recommend using the latest version of nlitsme's ubidump