bpftool: introduce cgroup tree command

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>

diff --git a/tools/bpf/bpftool/cgroup.c b/tools/bpf/bpftool/cgroup.c
index 16bee011e16cc883e99fcc49451b896ce713d636..ee7a9765c6b32f3eb9e22b79f8a112dd38983405 100644 (file)
--- a/tools/bpf/bpftool/cgroup.c
+++ b/tools/bpf/bpftool/cgroup.c
@@ -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>
@@ -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);
@@ -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);
@@ -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;
@@ -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;
 }
@@ -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;
        }
 
@@ -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;
@@ -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"
@@ -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]);
 
@@ -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 },