- -Apparently, checksum offloading is enabled by default and the kernel postpones csum calculation until the last moment, expecting csum to be calculated in the driver when the packet is sent. But we have a virtual environment and the packet eventually goes to the GTP tunnel on UPF. Obviously, this is the reason why csum is not calculated correctly. - -However, if we disable offloading, the checksum is calculated immediately on iperf and everything works. -
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