[PATCH net-next 4/5] bpftool: implement cgdetach command

[Roman Gushchin]

Implement cgdetach command, which allows to detach the bpf
program from a cgroup. It takes program id and attach type
as arguments.

Example:
$ ./bpftool cgdetach /sys/fs/cgroup/user.slice/ device 1

Signed-off-by: Roman Gushchin <g...@fb.com>
Cc: Alexei Starovoitov <a...@kernel.org>
Cc: Daniel Borkmann <dan...@iogearbox.net>
Cc: Jakub Kicinski <jakub.kicin...@netronome.com>
Cc: Martin KaFai Lau <ka...@fb.com>
---
 tools/bpf/bpftool/main.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 8eb3b9bf5bb2..77fcc1a0bd5d 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -81,12 +81,13 @@ static int do_help(int argc, char **argv)
                "Usage: %s [OPTIONS] OBJECT { COMMAND | help }\n"
                "       %s batch file FILE\n"
                "       %s cgattach FILE CGROUP TYPE\n"
+               "       %s cgdetach CGROUP TYPE ID\n"
                "       %s version\n"
                "\n"
                "       OBJECT := { prog | map }\n"
                "       " HELP_SPEC_OPTIONS "\n"
                "",
-               bin_name, bin_name, bin_name, bin_name);
+               bin_name, bin_name, bin_name, bin_name, bin_name);
 
        return 0;
 }
@@ -166,6 +167,7 @@ void fprint_hex(FILE *f, void *arg, unsigned int n, const 
char *sep)
 
 static int do_batch(int argc, char **argv);
 static int do_cgattach(int argc, char **argv);
+static int do_cgdetach(int argc, char **argv);
 
 static const struct cmd cmds[] = {
        { "help",       do_help },
@@ -173,6 +175,7 @@ static const struct cmd cmds[] = {
        { "prog",       do_prog },
        { "map",        do_map },
        { "cgattach",   do_cgattach },
+       { "cgdetach",   do_cgdetach },
        { "version",    do_version },
        { 0 }
 };
@@ -338,6 +341,51 @@ static int do_cgattach(int argc, char **argv)
        return 0;
 }
 
+static int do_cgdetach(int argc, char **argv)
+{
+       int prog_fd, cgroup_fd;
+       enum bpf_attach_type attach_type;
+
+       if (argc < 3) {
+               p_err("too few parameters for cgdetach\n");
+               return -1;
+       } else if (argc > 3) {
+               p_err("too many parameters for cgdetach\n");
+               return -1;
+       }
+
+       cgroup_fd = open(argv[0], O_RDONLY);
+       if (cgroup_fd < 0) {
+               p_err("can't open cgroup %s\n", argv[1]);
+               return -1;
+       }
+
+       attach_type = parse_attach_type(argv[1]);
+       if (attach_type == __MAX_BPF_ATTACH_TYPE) {
+               close(cgroup_fd);
+               p_err("Invalid attach type");
+               return -1;
+       }
+
+       prog_fd = bpf_prog_get_fd_by_id(atoi(argv[2]));
+       if (prog_fd < 0) {
+               p_err("invalid program id\n");
+               return -1;
+       }
+
+       if (bpf_prog_detach2(prog_fd, cgroup_fd, attach_type)) {
+               close(prog_fd);
+               close(cgroup_fd);
+               p_err("Failed to attach program");
+               return -1;
+       }
+
+       close(prog_fd);
+       close(cgroup_fd);
+
+       return 0;
+}
+
 int main(int argc, char **argv)
 {
        static const struct option options[] = {
-- 
2.14.3