WIP / DONT MERGE: Switch from userspace to kernelspace BPF filtering#8

Draft

T-X wants to merge 5 commits intolemoer:masterfrom

T-X:test-kernelspace-filtering

Commits on Dec 20, 2020

Makefile: allow overriding CC, CFLAGS and LDFLAGS from env
T-X
committed

Commits on Dec 21, 2020

filter: introducing rule substitutions via ${RULENAME}
T-X
committed

Commits on Dec 22, 2020