Re: [PATCH] bpf: bpftool, add support for attaching programs to maps

[John Fastabend <john.fastabend@gmail.com>]

On 10/10/2018 10:11 AM, Jakub Kicinski wrote:
> On Wed, 10 Oct 2018 09:44:26 -0700, John Fastabend wrote:
>> Sock map/hash introduce support for attaching programs to maps. To
>> date I have been doing this with custom tooling but this is less than
>> ideal as we shift to using bpftool as the single CLI for our BPF uses.
>> This patch adds new sub commands 'attach' and 'detach' to the 'prog'
>> command to attach programs to maps and then detach them.
>>
>> Signed-off-by: John Fastabend <john.fastabend@gmail.com>
>> ---
>>  tools/bpf/bpftool/main.h |    1 +
>>  tools/bpf/bpftool/prog.c |   92 ++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 92 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
>> index 40492cd..9ceb2b6 100644
>> --- a/tools/bpf/bpftool/main.h
>> +++ b/tools/bpf/bpftool/main.h
>> @@ -137,6 +137,7 @@ int cmd_select(const struct cmd *cmds, int argc, char **argv,
>>  int do_cgroup(int argc, char **arg);
>>  int do_perf(int argc, char **arg);
>>  int do_net(int argc, char **arg);
>> +int do_attach_cmd(int argc, char **arg);
> 
> Looks like a leftover?
> 

Yeah original I made attach/detach its own top level command
but it seems better fit under prog.

[..]

>> +	if (!REQ_ARGS(4)) {
> 
> Hm, 4 or 5?  id $prog $type id $map ?
> 

Yep thanks.

[...]

>> +
>> +	NEXT_ARG();
> 
> nit: maybe NEXT_ARG() should be grouped with the code that consumes the
>      parameter, i.e. new line after not before?

sure.

> 
>> +	mapfd = map_parse_fd(&argc, &argv);
>> +	if (mapfd < 0)
>> +		return mapfd;
>> +
>> +	err = bpf_prog_attach(progfd, mapfd, attach_type, 0);
>> +	if (err) {
>> +		p_err("failed prog attach to map");
>> +		return -EINVAL;
>> +	}
> 
> Could you plunk a
> 
> if (json_output)
> 	jsonw_null(json_wtr);
> 
> here to always produce valid JSON even for commands with no output
> today?
> 

Makes sense.

> Same comments for detach.

[...]

> Would you mind updating the man page and the bash completions?
> 

Will do this. Thanks.