I'm trying to compile the sample bpf program in Linux source code. So I downloaded the current kernel source code and entered samples/bpf folder
apt source linux
cd linux-*/samples/bpf
Then I tried to compile a sample program with gcc:
# gcc sock_example.c
sock_example.c:29:10: fatal error: bpf/bpf.h: No such file or directory
29 | #include <bpf/bpf.h>
| ^~~~~~~~~~~
compilation terminated.
And I'm unable to find bpf/bpf.h with apt-file
# apt-file find bpf/bpf.h
(no output)
What was wrong?
The Linux eBPF samples come with a rather long Makefile. It handles a lot of cases and integrates well with the kernel building workflow, but makes it more complicated to build the samples outside of the kernel tree.
For example, this Makefile adds a number of includes directories, such as TPROGS_CFLAGS += -I$(srctree)/tools/lib/, meaning that bpf/bpf.h will not be fetched from your OS' libraries but from tools/lib/ under your kernel repository.
Here are a few options that you can consider to compile your program:
tprogs-y target.sudo make -C tools/lib/bpf install) or from its GitHub mirror. This should install the headers, and gcc should then be able to find them.gcc -I <path/to/linux>/tools/lib).#include <bpf/bpf.h> to make it point to your library.)