On Thu, 26 Mar 2020 07:28:03 -0700 Maciej Żenczykowski wrote:
> diff --git a/extensions/libxt_bpf.c b/extensions/libxt_bpf.c
> index 92958247..44cdd5cb 100644
> --- a/extensions/libxt_bpf.c
> +++ b/extensions/libxt_bpf.c
> @@ -61,11 +61,22 @@ static const struct xt_option_entry bpf_opts_v1[] = {
> XTOPT_TABLEEND,
> };
>
> -static int bpf_obj_get(const char *filepath)
> +static int bpf_obj_get_readonly(const char *filepath)
> {
> #if defined HAVE_LINUX_BPF_H && defined __NR_bpf && defined BPF_FS_MAGIC
> union bpf_attr attr;
> + // file_flags && BPF_F_RDONLY requires Linux 4.15+ uapi kernel headers
> +#ifdef BPF_F_RDONLY
FWIW the BPF subsystem is about to break uAPI backward-compat and
replace the defines with enums. See commit 1aae4bdd7879 ("bpf: Switch
BPF UAPI #define constants used from BPF program side to enums").
> + int fd;
>
> + memset(&attr, 0, sizeof(attr));
> + attr.pathname = (__u64) filepath;
> + attr.file_flags = BPF_F_RDONLY;
> + fd = syscall(__NR_bpf, BPF_OBJ_GET, &attr, sizeof(attr));
> + if (fd >= 0) return fd;
> +
> + // on any error fallback to default R/W access for pre-4.15-rc1 kernels
> +#endif
