I have concluded the source of failure for many applications is that the sendfile syscall on my port doesn’t work. To be precise, sendfile sends garbage data to the other side. I have an USB to Ethernet adapter, and using that adapter, the problem disappears. So the conclusion is that my network driver is buggy.
Applications that might be affected are: network servers that sends file (http servers, file servers, etc), distcc.
I will try to fix this tomorrow.