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bpftool: introduce cgroup tree command
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This commit introduces a new bpftool command: cgroup tree.
The idea is to iterate over the whole cgroup tree and print
all attached programs.

I was debugging a bpf/systemd issue, and found, that there is
no simple way to listen all bpf programs attached to cgroups.
I did master something in bash, but after some time got tired of it,
and decided, that adding a dedicated bpftool command could be
a better idea.

So, here it is:
  $ sudo ./bpftool cgroup tree
  CgroupPath
  ID       AttachType      AttachFlags     Name
  /sys/fs/cgroup/system.slice/systemd-machined.service
      18       ingress
      17       egress
  /sys/fs/cgroup/system.slice/systemd-logind.service
      20       ingress
      19       egress
  /sys/fs/cgroup/system.slice/systemd-udevd.service
      16       ingress
      15       egress
  /sys/fs/cgroup/system.slice/systemd-journald.service
      14       ingress
      13       egress

Signed-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Cc: Quentin Monnet <quentin.monnet@netronome.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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Roman Gushchin authored and Daniel Borkmann committed Jul 6, 2018
1 parent ab8565a commit 2058b38
Showing 1 changed file with 165 additions and 5 deletions.
170 changes: 165 additions & 5 deletions tools/bpf/bpftool/cgroup.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,12 @@
// Copyright (C) 2017 Facebook
// Author: Roman Gushchin <guro@fb.com>

#define _XOPEN_SOURCE 500
#include <errno.h>
#include <fcntl.h>
#include <ftw.h>
#include <mntent.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
Expand Down Expand Up @@ -53,7 +58,8 @@ static enum bpf_attach_type parse_attach_type(const char *str)
}

static int show_bpf_prog(int id, const char *attach_type_str,
const char *attach_flags_str)
const char *attach_flags_str,
int level)
{
struct bpf_prog_info info = {};
__u32 info_len = sizeof(info);
Expand All @@ -78,7 +84,8 @@ static int show_bpf_prog(int id, const char *attach_type_str,
jsonw_string_field(json_wtr, "name", info.name);
jsonw_end_object(json_wtr);
} else {
printf("%-8u %-15s %-15s %-15s\n", info.id,
printf("%s%-8u %-15s %-15s %-15s\n", level ? " " : "",
info.id,
attach_type_str,
attach_flags_str,
info.name);
Expand All @@ -88,7 +95,20 @@ static int show_bpf_prog(int id, const char *attach_type_str,
return 0;
}

static int show_attached_bpf_progs(int cgroup_fd, enum bpf_attach_type type)
static int count_attached_bpf_progs(int cgroup_fd, enum bpf_attach_type type)
{
__u32 prog_cnt = 0;
int ret;

ret = bpf_prog_query(cgroup_fd, type, 0, NULL, NULL, &prog_cnt);
if (ret)
return -1;

return prog_cnt;
}

static int show_attached_bpf_progs(int cgroup_fd, enum bpf_attach_type type,
int level)
{
__u32 prog_ids[1024] = {0};
char *attach_flags_str;
Expand Down Expand Up @@ -123,7 +143,7 @@ static int show_attached_bpf_progs(int cgroup_fd, enum bpf_attach_type type)

for (iter = 0; iter < prog_cnt; iter++)
show_bpf_prog(prog_ids[iter], attach_type_strings[type],
attach_flags_str);
attach_flags_str, level);

return 0;
}
Expand Down Expand Up @@ -161,7 +181,7 @@ static int do_show(int argc, char **argv)
* If we were able to get the show for at least one
* attach type, let's return 0.
*/
if (show_attached_bpf_progs(cgroup_fd, type) == 0)
if (show_attached_bpf_progs(cgroup_fd, type, 0) == 0)
ret = 0;
}

Expand All @@ -173,6 +193,143 @@ static int do_show(int argc, char **argv)
return ret;
}

/*
* To distinguish nftw() errors and do_show_tree_fn() errors
* and avoid duplicating error messages, let's return -2
* from do_show_tree_fn() in case of error.
*/
#define NFTW_ERR -1
#define SHOW_TREE_FN_ERR -2
static int do_show_tree_fn(const char *fpath, const struct stat *sb,
int typeflag, struct FTW *ftw)
{
enum bpf_attach_type type;
bool skip = true;
int cgroup_fd;

if (typeflag != FTW_D)
return 0;

cgroup_fd = open(fpath, O_RDONLY);
if (cgroup_fd < 0) {
p_err("can't open cgroup %s: %s", fpath, strerror(errno));
return SHOW_TREE_FN_ERR;
}

for (type = 0; type < __MAX_BPF_ATTACH_TYPE; type++) {
int count = count_attached_bpf_progs(cgroup_fd, type);

if (count < 0 && errno != EINVAL) {
p_err("can't query bpf programs attached to %s: %s",
fpath, strerror(errno));
close(cgroup_fd);
return SHOW_TREE_FN_ERR;
}
if (count > 0) {
skip = false;
break;
}
}

if (skip) {
close(cgroup_fd);
return 0;
}

if (json_output) {
jsonw_start_object(json_wtr);
jsonw_string_field(json_wtr, "cgroup", fpath);
jsonw_name(json_wtr, "programs");
jsonw_start_array(json_wtr);
} else {
printf("%s\n", fpath);
}

for (type = 0; type < __MAX_BPF_ATTACH_TYPE; type++)
show_attached_bpf_progs(cgroup_fd, type, ftw->level);

if (json_output) {
jsonw_end_array(json_wtr);
jsonw_end_object(json_wtr);
}

close(cgroup_fd);

return 0;
}

static char *find_cgroup_root(void)
{
struct mntent *mnt;
FILE *f;

f = fopen("/proc/mounts", "r");
if (f == NULL)
return NULL;

while ((mnt = getmntent(f))) {
if (strcmp(mnt->mnt_type, "cgroup2") == 0) {
fclose(f);
return strdup(mnt->mnt_dir);
}
}

fclose(f);
return NULL;
}

static int do_show_tree(int argc, char **argv)
{
char *cgroup_root;
int ret;

switch (argc) {
case 0:
cgroup_root = find_cgroup_root();
if (!cgroup_root) {
p_err("cgroup v2 isn't mounted");
return -1;
}
break;
case 1:
cgroup_root = argv[0];
break;
default:
p_err("too many parameters for cgroup tree");
return -1;
}


if (json_output)
jsonw_start_array(json_wtr);
else
printf("%s\n"
"%-8s %-15s %-15s %-15s\n",
"CgroupPath",
"ID", "AttachType", "AttachFlags", "Name");

switch (nftw(cgroup_root, do_show_tree_fn, 1024, FTW_MOUNT)) {
case NFTW_ERR:
p_err("can't iterate over %s: %s", cgroup_root,
strerror(errno));
ret = -1;
break;
case SHOW_TREE_FN_ERR:
ret = -1;
break;
default:
ret = 0;
}

if (json_output)
jsonw_end_array(json_wtr);

if (argc == 0)
free(cgroup_root);

return ret;
}

static int do_attach(int argc, char **argv)
{
enum bpf_attach_type attach_type;
Expand Down Expand Up @@ -289,6 +446,7 @@ static int do_help(int argc, char **argv)

fprintf(stderr,
"Usage: %s %s { show | list } CGROUP\n"
" %s %s tree [CGROUP_ROOT]\n"
" %s %s attach CGROUP ATTACH_TYPE PROG [ATTACH_FLAGS]\n"
" %s %s detach CGROUP ATTACH_TYPE PROG\n"
" %s %s help\n"
Expand All @@ -298,6 +456,7 @@ static int do_help(int argc, char **argv)
" " HELP_SPEC_PROGRAM "\n"
" " HELP_SPEC_OPTIONS "\n"
"",
bin_name, argv[-2],
bin_name, argv[-2], bin_name, argv[-2],
bin_name, argv[-2], bin_name, argv[-2]);

Expand All @@ -307,6 +466,7 @@ static int do_help(int argc, char **argv)
static const struct cmd cmds[] = {
{ "show", do_show },
{ "list", do_show },
{ "tree", do_show_tree },
{ "attach", do_attach },
{ "detach", do_detach },
{ "help", do_help },
Expand Down

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