Re: [PATCH nft v4] src: enable json echo output when reading native syntax

["Jose M. Guisado" <guigom@riseup.net>]

On 4/8/20 16:20, Phil Sutter wrote:
> Yes, 'nft -j monitor' output has always been like this. Given that
> monitor potentially runs for a while and picks up multiple distinct
> ruleset changes, I wonder how it *should* behave.
> 
>> If it's not wrapped by the top-level nftables root then this is
>> unparseable.
> > We could change monitor code to add the wrapping "nftables" object to
> every line printed:
> 
> --- a/src/json.c
> +++ b/src/json.c
> @@ -1857,7 +1857,8 @@ int do_command_list_json(struct netlink_ctx *ctx, struct cmd *cmd)
>   static void monitor_print_json(struct netlink_mon_handler *monh,
>                                 const char *cmd, json_t *obj)
>   {
> -       obj = json_pack("{s:o}", cmd, obj);
> +       obj = json_pack("{s:[o, {s:o}]}", "nftables",
> +                       generate_json_metainfo(), cmd, obj);
>          json_dumpf(obj, monh->ctx->nft->output.output_fp, 0);
>          json_decref(obj);
>   }
> 
> Cheers, Phil
>
This would work on a line by line basis.

After giving another read to COMMAND OBJECTS section of 
libnftables-json(5) the only thing that comes to mind is that a line by 
line basis of JSON command objects would not take advantage of batching. 
If I'm not mistaken, each list of cmds is encapsulated inside the 
{nftables : ...} json object and it is then tried to be sent to netlink 
to be batched.

In addition, the output as a whole could not be parseable , only a 
single "nftables" object is expected when nft input is json.

My previous comments assume whole output of echo is expected to be 
admissible as input in nft for reproducibility, but I don't know if that 
is the case.


Regards.