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bpf-firewall: properly handle kernels where BPF cgroup is disabled but TRIE maps are enabled (#7298)

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So far, we assumed that kernels where TRIE was on also supported
BPF/cgroup stuff. That's not a correct assumption to make, hence check
for both features separately.

Fixes: #7054
This commit is contained in:
Lennart Poettering 2017-11-13 10:56:43 +01:00 committed by GitHub
parent bd1750f7fe
commit 93e93da5cc
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 26 additions and 1 deletions
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27
src/core/bpf-firewall.c
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@ -641,6 +641,12 @@ int bpf_firewall_reset_accounting(int map_fd) {
int bpf_firewall_supported(void) { int bpf_firewall_supported(void) {
struct bpf_insn trivial[] = {
BPF_MOV64_IMM(BPF_REG_0, 1),
BPF_EXIT_INSN()
};
_cleanup_(bpf_program_unrefp) BPFProgram *program = NULL;
static int supported = -1; static int supported = -1;
int fd, r; int fd, r;
@ -655,8 +661,10 @@ int bpf_firewall_supported(void) {
if (supported >= 0) if (supported >= 0)
return supported; return supported;
if (geteuid() != 0) if (geteuid() != 0) {
log_debug("Not enough privileges, BPF firewalling is not supported.");
return supported = false; return supported = false;
}
r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER); r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER);
if (r < 0) if (r < 0)
@ -676,5 +684,22 @@ int bpf_firewall_supported(void) {
safe_close(fd); safe_close(fd);
if (bpf_program_new(BPF_PROG_TYPE_CGROUP_SKB, &program) < 0) {
log_debug_errno(r, "Can't allocate CGROUP SKB BPF program, BPF firewalling is not supported: %m");
return supported = false;
}
r = bpf_program_add_instructions(program, trivial, ELEMENTSOF(trivial));
if (r < 0) {
log_debug_errno(r, "Can't add trivial instructions to CGROUP SKB BPF program, BPF firewalling is not supported: %m");
return supported = false;
}
r = bpf_program_load_kernel(program, NULL, 0);
if (r < 0) {
log_debug_errno(r, "Can't load kernel CGROUP SKB BPF program, BPF firewalling is not supported: %m");
return supported = false;
}
return supported = true; return supported = true;
} }