CMake, BSD: Fix BPF detection, use clonable device #90
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klemensn
commented
Apr 18, 2023
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klemensn
commented
- CMake: Typofix BSD bpf guard
- BSD: bpf(4) is clonable, use /dev/bpf
- CMake: Fix net/bpf.h detection on OpenBSD
- CMake: BSD: Fix bpf detection
- CMake: Linux: Pick BPF last
On OpenBSD, NetBSD and FreeBSD this device is clonable, i.e. the same device may be opened multiple times and there is no need to find an exclusive bpfN. /dev/bpf0 exists on OpenBSD (and certainly other systems) as mere fallback, but bpf[1-N] do not; they're the same anyway. ``` crw------- 1 root wheel 23, 0 Apr 11 16:01 /dev/bpf crw------- 1 root wheel 23, 0 Apr 11 16:01 /dev/bpf0 ``` Simplify code and match bpf(4) handling in existing BSD userland tools.
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There's more to fix in the CMake code and it makes sense to have it in one PR, so converting it to a draft until I have everything... |
https://man.openbsd.org/bpf.4 explains how `<net/bpf.h>` usage requires other headers as well, but CMake's `check_include_file()` only tests the single header alone, thus it fails to detect bpf(4) on at least OpenBSD. Pull BPF out of the generic loop and add `<sys/types.h>` to unbreak test compilation.
https://cmake.org/cmake/help/latest/command/find_file.html as well as the simpler `if (EXISTS ...)` expect files to be readable (i.e. `test -r`). At least on OpenBSD, thus bpf detection fails unless cmake is privileged: ``` crw------- 1 root wheel 23, 0 Apr 11 16:01 /dev/bpf ``` Rely on usual C header tests to discover bpf(4) instead. This should unbreak bpf detection on other BSDs as well.
BPF exists on both Linux and BSD. Make `src/eth-bsd.c` least preferred, so that `src/eth-linux.c` is used whenever possible on Linux.
klemensn
changed the title
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This gets
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Awesome @klemensn - happy someone is looking into the BSD part, because I have none to my avail at the moment ! |
Your call -- if this looks good enough, I'll fix other CMake stuff as well until OpenBSD is happy enough that I can consider switching upgrading our official Works (better) for me, I don't see how this would make it worse for any other system... |
Builds fine on Linux and it looks fine. I'll merge it in a sec - this time as merge commit - not squash it :-) |
