Problem phenomenon:

The following error occurred while compiling the kernel:

make[3]: *** No rule to make target 'net/ipv4/netfilter/ipt_ecn.c', needed by 'net/ipv4/netfilter/ipt_ecn.o'
make[2]: *** [net/ipv4/netfilter] Error 2
make[1]: *** [net/ipv4] Error 2
make: *** [net] Error 2

Cause analysis:

The main reason is that the Linux kernel code is decompressed under windows (I think a convenient reference is also needed on Windows), but some files (such as ipt_ecn. C, etc.) are case sensitive. When decompressing on windows, they overwrite each other because they are not case sensitive, resulting in the lack of files.

Solution:

Just decompress your source code and compile it again. When decompressing under windows, you will be prompted whether the same files need to be processed. Select no for all.