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bpf-program: make bpf_program_load_kernel() idempotent 

Let's "seal" off the BPF program as soo as bpf_program_load_kernel() is
called, which allows us to make it idempotent: since the program can't
be modified anymore after being turned into a kernel object it's safe to
shortcut behaviour if called multiple times.
This commit is contained in:
Lennart Poettering 2018-02-20 19:19:57 +01:00
parent 72a1db0bb2
commit e0ad39fc52
1 changed files with 8 additions and 2 deletions
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10
src/basic/bpf-program.c
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@ -28,6 +28,7 @@
#include "fd-util.h"
#include "log.h"
#include "missing.h"
#include "util.h"
int bpf_program_new(uint32_t prog_type, BPFProgram **ret) {
_cleanup_(bpf_program_unrefp) BPFProgram *p = NULL;
@ -58,6 +59,9 @@ int bpf_program_add_instructions(BPFProgram *p, const struct bpf_insn *instructi
assert(p);
if (p->kernel_fd >= 0) /* don't allow modification after we uploaded things to the kernel */
return -EBUSY;
if (!GREEDY_REALLOC(p->instructions, p->allocated, p->n_instructions + count))
return -ENOMEM;
@ -72,8 +76,10 @@ int bpf_program_load_kernel(BPFProgram *p, char *log_buf, size_t log_size) {
assert(p);
if (p->kernel_fd >= 0)
return -EBUSY;
if (p->kernel_fd >= 0) { /* make this idempotent */
memzero(log_buf, log_size);
return 0;
}
attr = (union bpf_attr) {
.prog_type = p->prog_type,